JP2505883B2 - Development device - Google Patents

Description

The present invention relates to a developing device for developing an electrostatic latent image formed on an image carrier by an electrophotographic system or an electrostatic recording system. .

[Conventional technology]

Conventionally, a developing device for developing an electrostatic latent image formed by an electrophotographic system or an electrostatic recording system on an image carrier using a one-component developer or a two-component developer has various structures. Although proposed, the typical developing device is shown in FIGS. 6 to 8.

In this example, in the rotary developing means used in the color image forming apparatus, one developing device rotationally transferred to the developing position facing the image carrier is shown.

The developing device 1 includes a developing container 2, and screws 4 and 6 are arranged in the developing container 2. The developer 8 is reciprocally circulated in the developing container 2 by the screws 4 and 6.

Further, the developing device 1 includes a developer carrying member for carrying the developer 8 in the developing container toward the image carrying member 100 in order to develop the electrostatic latent image formed on the image carrying member 100. Having 10. Usually, the developer carrier 10 is fixed to a magnet roller 10a which is magnetized as shown in the figure, and is rotatably mounted around the magnet roller 10a in the direction of the arrow shown in the figure, so that the developer is carried toward the image carrier 100. It is composed of a developing sleeve l0b that is conveyed to. As shown in FIG. 7, the shaft 10c of the developing sleeve 10b is supported by both side walls 2a of the developing container 2 (only one side wall 2a is shown in FIG. 7) via a bearing 12. ing.

With this structure, the rotation of the developing sleeve 10b causes N ₂
The developer 8 drawn up by the pole is conveyed in the order of S ₂ pole → N ₁ pole → S ₁ pole and regulated by the regulation blade 30 to form a thin developer layer. The S ₁ pole is the main developing pole, and the developer that has stood there develops the electrostatic latent image on the image carrier 100, and then N
_3-pole, the developer on the developing sleeve 10b by the repulsive magnetic field of the N ₂ pole falls into the developer container 2.

[Problems to be solved by the invention]

However, in such a conventional configuration, a small amount of the developer enters between the end seal members 14 and 16 and the peripheral surface of the developing sleeve 10b. Therefore, if the developing device is used for a long period of time, this developer will be
Fusion and aggregation occur between 6

Part of this aggregate will be taken into the developer,
If the agglomerates are large, they may be caught by the regulation blade 30 and the developer may not be coated on the developing sleeve 10b, which may cause white streaks on the image.

If the agglomerates are small, they are developed together with a developer. Especially in the case of a solid image, transfer defects occur mainly in the developed agglomerates, and white spot-like defects occur on the image, resulting in a poor image quality. Will significantly reduce. If the adhesion of the end seal member is increased for the purpose of preventing this, an extremely large stress is applied to the developing sleeve, the load of the developing sleeve drive motor is increased, and the ingress of the developer is completely prevented for a long period of time. Was difficult.

Further, in the developing device having such a configuration, the developer 8 circulated and moved in the developing container 2 as described above is transferred to the bearing 12 portion along the surface of the developing sleeve 10b to move the bearing portion. Leakage through the outside or stay in the bearing to reduce the function of the bearing, thereby developing sleeve
In order to prevent the smooth rotation of 10b from being hindered, as shown in FIG. 7 and FIG. 8, an end seal member 14 such as an elastic body or a non-woven fabric is provided around both ends of the developing sleeve 10b.
Or an end seal member 16 having an elastic contact tongue 16a for ensuring a reliable contact with the developing sleeve 10b is provided, and means for closing the gap between the developing sleeve and the developing container side wall 2a is provided. Has been.

Particularly in recent years, colorization and graphic conversion have been progressing in printers and copying machines, and the reproducibility of halftones and solid images has become important. Then, in order to achieve these severe high image quality, the developer is made finer, and on the other hand, an alternating electric field is applied in the developing section in order to improve the developing ability.

When the developer (particularly toner) is miniaturized, it is generally prone to agglomeration, and further, these agglomerates are easily developed by a strong electric field.

Therefore, an object of the present invention is to completely prevent the developer from being subjected to stress by the seal member and the developer carrying member such as the developing sleeve to form an agglomerate, and further to cause fusion. Further, unlike the conventional case, it is not necessary to increase the adhesion of the end seal member for the purpose of preventing the generation of aggregates. In other words, it is an object of the present invention to provide a developing device that does not cause an adverse effect such as an increase in driving load on the developer carrier.

[Means for solving the problem]

The present invention which solves the above-mentioned problems, a developer container for accommodating a developer containing toner particles and magnetic particles, and a magnet provided inside an opening of the developer container to carry the developer on the surface and convey it And a magnetic member provided along the circumferential direction of the developer carrier with a predetermined gap at the end of the developer carrier, the magnetic member being a developer. The thickness of the carrier in the axial direction is 0.2 to 1 mm, the angle formed by the magnetic member with respect to the normal to the peripheral surface of the developer carrier is 45 degrees or less, and the magnetic force lines are concentrated in the gap between the magnetic member and the developer carrier. It is characterized in that a magnetic brush is formed to seal the leakage of the developer to the end portion.

〔Example〕

Hereinafter, the present invention will be described based on an embodiment thereof with reference to the accompanying drawings.

Referring to FIG. 5, there is shown an overall schematic structure of a full-color electrophotographic copying machine as an embodiment of the image forming apparatus according to the present invention. Referring to FIG. 5, a schematic central portion of the copying machine is shown. Is provided with a photosensitive drum 100 as an image carrier having an electrophotographic photosensitive layer on its surface, and is rotationally driven in the direction of arrow x (counterclockwise direction).

A primary charger A is disposed almost directly above the photosensitive drum 100, and a rotary developing device B is provided on the left side of the photosensitive drum 100.
Is provided, a transfer device (transfer drum) 5 is provided substantially directly below the photosensitive drum 100, and a cleaning device C is provided on the right side of the photosensitive drum 1.

An optical system D is disposed above the electrophotographic copying machine, and the optical system D forms an image of an original document O on a transparent platen 7 such as a glass plate with the primary charger A and a rotary developing device. Ten
The exposure unit 3 located between 0 and 0 is configured to project (slit exposure) onto the photosensitive drum 100. Although such an optical system D may use any optical system, in the present embodiment, the first scanning mirror 11 and the second scanning mirror 11 that moves in the same direction at a speed half that of the first scanning mirror 11 are used. The third scanning mirrors E and 13, the imaging lens F, and the fourth fixed mirror 15 are provided. Since the optical system D is a well-known slit exposure type optical system, a detailed description thereof will be omitted here.

The document illumination light source G is configured to move together with the first scanning mirror 11, and the color separation filter 17 is arranged between the fourth fixed mirror 15 and the exposure unit 3.

The reflected light image of the original O scanned by the first, second, and third scanning mirrors 11, E, and 13 passes through the lens F, then passes through the fourth fixed mirror 15, and is color separated by the color separation filter 17.
An image is formed on the photosensitive drum 100 by the exposure unit 3.

Further, a fixing device I and a paper feeding device J are arranged on the right side in the full-color electrophotographic copying machine, and a transfer material is provided between the transfer device 5 and the fixing device I and the paper feeding device J, respectively. Transport systems 25 and 35 are provided.

With the above configuration, the photosensitive drum 100 is the color separation filter 17
The series of image forming processes such as charging, exposure, development, transfer and cleaning for each color separated by
A primary charger A, an optical system D, a rotary developing device B, a transfer device 5, and a cleaning device C are used.

Here, the above-mentioned rotary developing device B includes the rotary support 30.
0 and a developing device that is detachably held on the rotary support 300 at an angular interval of approximately 90 ° (in the present embodiment, the yellow developing device unit 101Y and the magenta developing device unit). 101M, a cyan developing unit 101C, and a black developing unit 101Bk are provided as four developing units), and latent images of each color formed on the surface of the photosensitive drum 100 by color separation are respectively associated with the corresponding developing units. Visualize with a unit developer. That is, the rotary support 30
By the rotation angle control of 0 at about 90 °, the developing roller of the required developing device unit is moved to a predetermined developing position that opposes the photosensitive drum 100, and the developing device unit executes the developing process. At the time of development, an oscillating voltage of sine wave, rectangular wave, etc., such as alternating current or alternating current superposed with direct current voltage, is applied to the developing roller as a developing bias voltage at the developing roller to repeatedly attach and detach toner to and from the photosensitive drum. After that, the latent image is developed. Incidentally, FIG. 5 shows the photosensitive drum 1.
On the other hand, the black developing unit 101B is shown in a state of being opposed to the photosensitive drum 1.

The developed image thus developed is transferred by the transfer device 5 to the transfer material P supplied from the paper feeding device J.
That is, the transfer device 5 typically includes a transfer material P, that is, a transfer drum 5b having a gripper 5a for gripping the transfer paper on its peripheral surface. Transfer material transport system from transfer material cassette 31 or 32 of J
The front end of the transfer material P fed through 35 is gripped by the gripper 5a, and is rotated and transferred to transfer the visible image of each color on the photosensitive drum 100. A transfer charger 5c is arranged inside the transfer drum 5 in the transfer area.

Thus, the transfer material P on which the visible images of the respective colors, that is, the toner images by the developer are sequentially transferred, is released from the gripper 5a and separated from the transfer drum 5b by the separation claw 8. Next, the transfer material P separated from the transfer drum 5b is sent to the fixing device I by the transfer material conveying system 25, and the toner image on the transfer material P is fixed on the transfer material P by this fixing device J, and thereafter, The transfer material P is discharged onto the tray K.

FIG. 1 is a sectional view of the vicinity of one developing device shown in FIG. 5 of the embodiment of the present invention. The latent image carrier 100 (hereinafter referred to as a photosensitive drum) is rotated in the direction of arrow a by a driving device (not shown). Reference numeral 10b denotes a developing sleeve which is close to the latent image carrier 100 and is made of a non-magnetic material such as aluminum or SUS316. The developing sleeve 10b is the developing container 1
The left substantially semi-peripheral surface is projected into the container 10a in a laterally long opening formed in the container longitudinal direction on the lower left wall of a, and the right substantially semi-peripheral surface is exposed outside the container and rotatably rotatably laid horizontally. It is rotationally driven in the direction of arrow b.

Reference numeral 10a denotes a fixed permanent magnet (magnet) as fixed magnetic field generating means which is inserted into the developing sleeve 10b and positioned and held in the position and orientation shown in the figure. Even when the developing sleeve 10b is rotationally driven, the magnet 10a is at the position shown in the figure. It is fixedly held as it is. This magnet 10a has five magnetic poles. Magnet 10a
May be replaced with a permanent magnet instead of a permanent magnet.

Reference numeral 30 designates a base portion fixed to a side wall of the container on the upper edge side of the developer supply device in which the developing sleeve 10b is disposed, and the front end side is protruded toward the inside of the container 1a from the upper edge position of the opening and extends along the length of the upper edge of the opening. With a magnetic blade as a developer regulating member arranged as
For example, SUS316 is bent into a V-shaped cross section.

L is a magnetic particle limiting member whose upper surface is in contact with the lower surface side of the non-magnetic blade 30 and whose front end surface is the developer guide surface M. The portion formed by the magnetic blade 30 and the magnetic particle limiting member L and the like is the restriction portion.

In the present invention, the magnetic carrier used has a weight average particle diameter of 35 to 65 μm, preferably 40 to 60 μm,
Weight distribution of particle size 26μm or less 2-6% or less, particle size 35-43
5 to 25% of particles having a particle size of 74 μm and 2% or less of particles having a particle size of 74 μm or more, and an electric resistance value of 10 ⁷ Ωcm or more, preferably 10 ⁸ Ωcm or more, more preferably 10 ⁹ to 10 ¹²
Resin coated with ferrite particles (maximum magnetization of 60 emu / g) so as to be Ωcm can be preferably used.

The measurement of the resistance value of magnetic particles such as ferrite particles or resin-coated ferrite particles is performed with a measuring electrode area of 4 cm ² .
Using a Saint-German type cell with an interelectrode gap of 0.4 cm,
This is a value obtained by measuring the resistance value of the magnetic particles from the current flowing in the circuit by applying an applied voltage E (V / cm) between both electrodes under a pressure of 1 kg weight to one electrode.

The toner used in the present invention has a volume average particle diameter of M and a toner particle diameter of γ, and is 90% by volume or more in a range of 1 / 2M <γ <3 / 2M. A toner containing toner particles and 99% by volume or more of toner particles in the range of 0 <γ <2M is used. Further, in the present invention, a toner having a volume average particle diameter M of less than 12 μm (preferably 10 μm or less, more preferably 8 μm or less) is used.

In the present invention, the volume distribution and volume average particle diameter of the toner are those measured by the following measuring method, for example.

A Coulter Counter TA-II type (manufactured by Coulter) is used as a measuring device, an interface (manufactured by Nikkaki) that outputs a number average distribution and a volume average distribution, and a CX-i personal computer (manufactured by Canon) are connected to the electrolytic solution. Is 1
Prepare a 1% NaCl aqueous solution using graded sodium chloride.

As a measuring method, 0.1 to 5 ml of a surfactant (preferably an alkylbenzene sulfonate) as a dispersant is added to 100 to 150 ml of the electrolytic aqueous solution, and 0.5 to 50 mg of a measurement sample is further added.

The electrolytic solution in which the sample was suspended was subjected to a dispersion treatment for about 1 to 3 minutes by an ultrasonic disperser, and the Coulter Counter TA-II type was used to perform the dispersion using a 100 μm apater as an apater.
The volume distribution is obtained by measuring the particle size distribution of particles of -40 μm.

The volume average particle size of the sample can be obtained from the obtained volume distribution.

In the present invention, the toner means colored resin particles (binder resin,
A colorant, optionally containing other additives) itself, and colored resin particles externally added with an external additive such as hydrophobic colloidal silica fine powder.

Examples of the binder resin used in the toner include a styrene-based copolymer such as a styrene-acrylic acid ester resin or a styrene-methacrylic acid ester resin, or a polyester resin. Particularly, in consideration of the color mixing property at the time of fixing the color toner, the polyester resin is more preferable because it has sharp melting characteristics.

An embodiment of the present invention using the above-mentioned developer will be described in more detail with reference to the drawings.

The developing device 1a of the present embodiment shown in FIG. 1 is a developing device used for a rotary developing means for a color image forming apparatus, as described in connection with FIG. The present invention is not limited to this.

In the present embodiment, the developing device 1a is a developer (a magnetic toner in which magnetic particles are kneaded with a resin, that is, a one-component magnetic developer, or a two-component developer in which a magnetic carrier containing magnetic particles as a main component and toner are mixed. ) Is contained in the developing container 2, and the screws 4 and 6 for circulating the developer in the developing container 2 are arranged in the developing container 2. The developer is not shown in FIG.

Further, the developing device 1 uses the developer in the developing container to develop the electrostatic latent image formed on the image carrier 100.
It has a developer carrier 10 for transporting towards 100.
In the present embodiment, the developer carrying member 10 is a magnetized fixed magnet roller 10a and a developing sleeve 10 that is rotatably mounted around the magnet roller 10a in the direction of the arrow and conveys the developer.
It consists of b and.

As shown in FIG. 2, the developing sleeve 10b has rotary support shafts 10c (only one end is shown in FIG. 2) at both ends, and a bearing 12 is provided on the side wall 2a of the developing container 2. It is rotatably supported via.

With such a configuration, the developing sleeve 10b is the same as the conventional one.
The developer drawn up by the N ₂ pole by the rotation of is conveyed in the order of S ₂ pole → N ₁ pole → S ₁ pole and regulated by the regulation member 30 to form a thin developer layer. The S ₁ pole is the main developing pole, and the developer that has risen here develops the electrostatic latent image on the image carrier 100, and then N ₃
The developer on the developing sleeve 10b falls into the developing container 2 due to the repulsive magnetic fields of the poles and N ₂ poles.

According to the present invention, the plate-shaped magnetic members 21 are arranged at both ends of the developing sleeve 10b so as to surround the developing sleeve 10b and are attached to the side wall 2a of the developing container. The magnetic member 21 is preferably made of a ferromagnetic material such as an iron plate, a nickel plate, a cobalt plate, or an alloy plate thereof having a thickness (t) of about 0.2 to 1 mm. These materials are (1 /
2) ・ (BH) max is 0.7 J / m ² or less. (BH) max is B
Is the residual magnetic flux density and H is the coercive color, and the maximum value of B × H indicates the maximum energy product. The gap (g) with the peripheral surface of the developing sleeve 10b is not limited, but is 0.3.
It is appropriately selected within the range of ~ 2 mm.

In this embodiment, the magnetic member, that is, the magnetic plate 21 is a developing sleeve.
Form a uniform void (g) with the peripheral surface of 10b,
The developing sleeve 10b is formed in an annular shape having a width (w) having the same center as that of the developing sleeve 10b, but the shape is not limited to the illustrated shape, and various shapes can be set by the designer as desired. You can What is important is that the magnetic plate 21 is arranged along the peripheral surface of the developing sleeve 10b in a non-contact state. Further, the angle formed by the side surface of the magnetic plate 21 with respect to the normal line of the peripheral surface of the developing sleeve 10b is to more reliably prevent the developer from leaking.
It is preferably 45 degrees or less.

Further, the magnetic plate 21 is preferably arranged over the entire peripheral surface of the developing sleeve 10b, but as shown in FIG. 1, it may not be formed over the entire peripheral surface of the developing sleeve 10b.

In this way, by disposing the magnetic plates at both ends of the developing sleeve 10b, the magnetic plate 21 is magnetized by the magnetic force of the magnet roller 10a provided inside the developing sleeve 10b, and the magnet roller 10a and the magnetic slope 21 are A magnetic circuit is formed between the magnetic plate 21 and the magnetic field, and the magnetic field is concentrated on the tip of the magnetic plate 21 on the side of the developing sleeve 10b. Therefore, in the space (g) between the magnetic plate and the developing sleeve 10b, a magnetic brush dense with the developer is formed. Is formed. The magnetic brush is provided on the side wall 2 of the developing container along the developing sleeve 10b.
The bearing 12 passes through the gap between a and the developing sleeve 10b and the surface.
It acts to prevent the developer from entering into. That is, the magnetic brush made of the developer formed in the gap (g) between the magnetic plate 21 and the developing sleeve 10b functions as an end seal member.

The above developer was set in a developing device and an image was formed under the following conditions.

Drum 80mmφ OPC Linear velocity 160mm / sec Sleeve 32mmφ SUS Sandblast Linear velocity 280mm / sec Latent image contrast 300V Fog removal potential 150V (difference between bright area potential and development bias DC) Development bias AC component 2.0KVpp 2.0KHz Distance between sleeve and drum 500 μm Sleeve-blade distance 800 μm Development pole 1000 Gauss In particular, in this embodiment, full-color toner, which emphasizes image quality, is used, and although it has sharp melting characteristics, it is soft as toner and easily aggregates with little stress. , It tends to be fused and become a lump. Furthermore, since the particle size is smaller, the cohesiveness is also improved, and the developing ability should be further improved from the initial stage to the long term (specifically, several hundreds of thousands of sheets) even though an AC electric field is applied to the developing section. In addition, a good image was obtained in which white spots and white streaks did not occur on the image.

FIG. 3 shows another embodiment of the present invention. According to this embodiment, the auxiliary seal member 23, which is formed of an elastic sheet adjacent to the magnetic plate 21 and whose tip end elastically contacts the developing sleeve 10b, is used.
Can be installed in parallel. As the auxiliary seal member 23, for example, polyethylene terephthalate, urethane rubber sheet or the like having a thickness of about 0.1 to 0.5 mm is suitable. By providing the auxiliary seal member 23 in this manner, a part of the magnetic brush of the developer formed in the gap (g) between the magnetic plate 21 and the developing sleeve 10b is scattered toward the bearing 12. Can be prevented.

FIG. 4 shows another preferred embodiment of the present invention.

According to the developing device of the present invention, the number and orientation positions of the magnetic poles of the magnet roller 10a do not need to be configured as shown in FIG. 1, but other numbers of poles or various orientation positions may be used. However, when the magnetic poles are arranged as in this embodiment, the magnetic brush is not formed by the developer particularly in the void (g) adjacent to the repulsive magnetic field forming portions of the N ₃ pole and the N ₂ pole. It tends to be weaker than others. Therefore, if the developer enters the bearing 12 through the gap, the magnet 25 is used as an auxiliary seal member to capture the developer.
Can be provided. The magnet 25 is a developing sleeve 10b.
Is a along the circumferential surface an annular magnet formed over the same region as the magnetic plate 21, the inner surface S pole in this embodiment, the outer surface are magnetized to N-pole, in particular N ₃ poles, N configured so as to seal leakage of the developer from _bipolar region. According to this embodiment, the developer once captured by the magnet 25 is
A magnetic brush is formed in the space between the surface of the developing sleeve 10b and the developing sleeve 10b, and has a function of sealing the leakage of the developer that enters from the N ₃ pole and N ₂ pole regions thereafter.

An experiment was conducted in the above two embodiments under the same conditions as in the first embodiment. As a result, in the developing device having the construction according to each of the above embodiments, the developer in the developing container is transferred from the bearing portion 12 to the outside even after long-term use. It has been proved that the function of the bearing portion is not reduced by leaking into the bearing portion 12 or entering the bearing portion 12.

〔The invention's effect〕

As described above, in the developing device according to the present invention, magnetic members are arranged at both ends of a developer carrying member such as a developing sleeve having a magnet built therein to concentrate magnetic force lines. A magnetic brush of the developer, which functions as a seal member at both ends of the carrier, is formed along the magnetic lines of force, whereby the developer can be completely prevented from leaking to the outside. Many solid images using, for example, without disturbing the movement of the developer carrier even in the long-term use of a full-color image, always enables a smooth developing operation, thereby without forming a developer aggregate, This has the advantage that a stable image can be obtained for a long period of time, and the reliability of the full-color image forming apparatus as a whole is improved. Of course, the present invention is also applicable to a developing device of a monochromatic image forming apparatus.

[Brief description of drawings]

FIG. 1 is a sectional view of an embodiment of the developing device according to the present invention, and FIGS. 2, 3, and 4 are sectional front views of the embodiment of the developing device according to the present invention, showing only one end portion. Shows. FIG. 5 is a schematic overall configuration diagram of a full-color image forming apparatus to which an embodiment of the developing device of the present invention is applied, FIG. 6 is a sectional view of a conventional developing device, and FIGS. 7 and 8 are conventional developing devices. Only one end is shown in the sectional front view of FIG. 10a: developer carrier 10b: magnet 21: magnetic member 25: magnet

Continuation of the front page (56) References JP-A-61-130962 (JP, A) JP-A-62-153863 (JP, A) Actually opened 60-74155 (JP, U) Actually opened 62-143968 (JP , U)

Claims (5)

(57) [Claims] 1. A developer container for containing a developer containing toner particles and magnetic particles, and a developer carrier for carrying and carrying the developer on the surface by having a magnet provided inside the opening of the developer container. In a developing device having a body and a magnetic member provided at an end portion of the developer carrying body along a circumferential direction of the developer carrying body with a predetermined gap, the magnetic member is a shaft of the developer carrying body. Direction thickness 0.2-1m
m, the angle formed by the magnetic member with respect to the normal line of the peripheral surface of the developer carrier is 45 degrees or less, and the magnetic brush is formed in the gap between the magnetic member and the developer carrier by the concentration of magnetic force lines to form the end of the developer. A developing device, which is characterized by sealing the leakage into the developing device. 2. The developing device according to claim 1, wherein an auxiliary seal member is arranged adjacent to the magnetic member. 3. The developing device according to claim 2, wherein the auxiliary seal member is an elastic sheet or a magnet. 4. The developing device according to claim 1, wherein an alternating electric field containing a DC component is applied to the developing section. 5. The developing apparatus according to claim 1, wherein the volume average particle diameter M of the toner particles is 12 μm or less.