JP2002365916A - Development machine and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developing device having a plurality of developing carriers and using one-component developer, which developing device uniformly and steadily forms a coating of the magnetic one-component developer over one of the two adjacent developer carriers, which is situated upstream in the direction of rotation of a latent-image carrier. SOLUTION: The polarity of a magnetic pole A and the polarity of a magnetic pole C are set to be the same; the polarity of a magnetic pole B is different from the polarities of the magnetic poles A and C; and their relationships are predetermined, so as to satisfy |the magnetic force of the magnetic pole A|>|the magnetic force of magnetic pole B|>|the magnetic force of the magnetic pole C|.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing apparatus and an image forming apparatus used for a copying machine, a laser beam printer, a facsimile, a printing apparatus, and the like which employ an electrophotographic system or the like.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus employing an electrophotographic system or the like, after uniformly charging a latent image carrier, analog exposure or image exposure using a semiconductor laser or LED is performed. Forming an electrostatic latent image on a latent image carrier, visualizing the electrostatic latent image as a developer image by a developing device, and transferring the developer image to a transfer material as a recording material; There is known an image forming apparatus which outputs a fixed image by separating a toner image from a latent image carrier and performing a fixing process by a fixing device.

First, an example of the operation of the conventional image forming apparatus will be described with reference to FIG.

Such an image forming apparatus is, for example, an OPC,
The photosensitive drum 101 includes a photoconductive layer such as a-Si and is rotated in the direction of arrow A as a latent image carrier.

In this image forming apparatus, first, the surface of the photosensitive drum 101 is uniformly charged to, for example, +500 V by the primary charger 103.

Next, image exposure 1 according to the image signal information
By 12, the surface potential of the exposed portion on the photosensitive drum 101 is attenuated to, for example, −200 V, and a latent image corresponding to the image signal of the image is formed on the photosensitive drum 101. Image exposure 11
For 2, a semiconductor laser or an LED array is used, for example.

Next, the latent image is developed by a developing device 102 as a developing device shown in FIG. 13 using a one-component developer and is visualized as a toner image. A developing device using a one-component developer has a high durability and a long life because it is simple and does not require replacement of a carrier and the like. For example, there is a jumping development using a magnetic one-component toner. The developing device 102 is provided with an upstream developing sleeve 20 as a developer carrier in which a magnetic pole arrangement and a magnet of magnetic force as shown in FIG. The developing device 102 uses black toner that is negatively charged. Further, at the time of development, the upstream developing sleeve 20 provided in the developing device 102 has a developing bias voltage of −50.
A DC bias voltage of about 0 V is applied, and the photosensitive drum 1
01 is developed in reverse.

Since a photosensitive drum having a long service life such as a high-speed machine has a large outer diameter of the photosensitive drum and cannot separate the curvature of the transfer material from the photosensitive drum, the photosensitive drum 101 carrying the toner image may be provided as necessary. Pre-transfer treatment (usually DC or A
C, or a combination of corona application or light neutralization).

Thereafter, the toner image on the photosensitive drum 101 is transferred by the transfer charger 104 onto a transfer material supplied between the photosensitive drum 101 and the transfer charger 104.

The transfer material to which the toner image has been transferred by the transfer charger 104 is separated from the photosensitive drum 101 by the separation charger 105, and then conveyed to a fixing device 107, where the toner image is formed by the fixing device 107. The image is fixed on the transfer material to form a fixed image.

On the other hand, the photosensitive drum 101 after the transfer process is
The transfer residual toner remaining on the photosensitive drum 101 without being subjected to the development is removed by the cleaning device 106 to prepare for the next image formation.

Incidentally, in order to increase the speed of the image forming apparatus, a conventional developing apparatus is disclosed in Japanese Patent Application Laid-Open No. 03-204.
084, a developing device using a two-component magnetic brush is provided with a plurality of developing sleeves as a developer carrier, or as described in JP-A-02-188778. Supplying toner from the developing sleeve to the photosensitive member by providing a developing sleeve as a developer carrying member, and making the distance between each developing sleeve and the photosensitive member as a latent image carrying member closer to the developing sleeve on the downstream side in the rotation direction of the photosensitive member. There is known a developing device which achieves a uniform amount.

Conventionally, in a developing device provided with a plurality of developing sleeves, the size of the developing sleeve is reduced as disclosed in Japanese Patent Publication No. 3-5579 in order to reduce the size of the image forming apparatus. Developing devices are known.

Further, regarding the magnetic force of a plurality of developing sleeves by such two-component development, see JP-A-9-809.
19 and Patent No. 3017514 have been proposed.

[0015]

However, conventionally,
In the developing device having the plurality of developing sleeves as described above, the upstream developer carrier in the rotation direction of the latent image carrier among the two adjacent developer carriers is the downstream developer in the downstream direction. Since the developer is disposed close to the downstream developer carrier so as to regulate the amount of the developer on the carrier to a predetermined amount, space can be saved. When the developer is used, it is difficult to uniformly coat the developer on the developer carrier as in the case of using a two-component developer using a carrier. for that reason,
As a developing device having a plurality of developing sleeves using a magnetic one-component developer as described above, there has been no product that is actually commercialized or has been presented at a conference.

In particular, a replenishment type developing device that replenishes developer at any time and a developing system using a plurality of developer carriers are suitable for a high-speed machine, but not a so-called cartridge system. Since the device is required to have durability and stability, it has been more difficult to realize.

Accordingly, the present invention provides a developing device which includes a plurality of developing carriers and employs a one-component type developer. It is an object of the present invention to provide a developing device and an image forming apparatus that can uniformly and stably coat a magnetic one-component developer on an upstream developer carrier.

[0018]

According to the present application, the object is to develop a latent image by applying a magnetic one-component developer to a rotating latent image carrier that carries the latent image on the surface. A developing device for visualizing as a developer image, comprising a plurality of developer carriers that are arranged in close proximity to the latent image carrier and carry and rotate the developer on the surface, and the plurality of developer carriers are Rotating in the same direction, the upstream developer carrier of the two adjacent developer carriers in the rotational direction of the latent image carrier determines the amount of developer on the downstream developer carrier on the downstream side. In the developing device arranged close to the downstream developer carrier to the extent that the amount is regulated to a fixed amount, each developer carrier is
Each of the magnetic members includes a first magnetic pole disposed at or near the latent image carrier of the upstream developer carrier, and a downstream developing member of the upstream developer carrier. A second magnetic pole disposed in the vicinity of the developer carrier or in the vicinity thereof, and a third magnetic pole disposed in the vicinity of the upstream developer carrier of the downstream developer carrier or in the vicinity thereof. The first magnetic pole and the third magnetic pole have the same polarity, the second magnetic pole has a different polarity from the first magnetic pole and the third magnetic pole, and the magnetic force of the first magnetic pole is A, Assuming that the magnetic force of the two magnetic poles is B and the magnetic force of the third magnetic pole is C, the first invention satisfies the relationship of | A |> | B |> | C |.

Further, according to the present application, the above object is achieved according to the first aspect, wherein the magnetic force A of the first magnetic pole is 80 mT or more, and the magnetic force B of the second magnetic pole and the magnetic force C of the third magnetic pole are each 50 mT. The above is also achieved by the second invention.

Further, according to the present application, the above object is achieved in the first invention or the second invention, in which the second magnetic pole and the third magnetic pole are arranged so that the second magnetic pole and the third magnetic pole are located between the rotation center of the upstream developer carrier and the downstream developer carrier. The present invention is also achieved by the third invention in which the latent image carrier is positioned farther from the line connecting the rotation center and the latent image carrier.

According to the present application, the above object is achieved in any one of the first to third aspects by applying a bias voltage comprising an AC component and a DC component to each developer carrier during development. This is also achieved by the fourth aspect of the invention.

Further, according to the present application, the above object is achieved according to any one of the first to fourth inventions, wherein each developer carrier is coated with a coating member having a crystalline graphite and a phenol resin on the surface. This is also achieved by the fifth invention that is configured as described above.

According to the present application, the object is to provide an image forming apparatus for recording an image formed by a series of image forming processes on a recording material, comprising: a latent image carrier; The present invention is also achieved by the sixth invention including the developing device according to any one of the fifth inventions.

Further, according to the present application, the above object is achieved in the sixth aspect by a transfer means for transferring a developer image on a latent image carrier to a recording material, and the transfer of the developer image by the transfer means. Cleaning means for removing the developer remaining on the latent image carrier after the transfer to the recording material, a developing device,
The present invention is also achieved by the seventh invention in which the developer removed from the latent image carrier by the cleaning means is configured to be collected and reused.

[0025]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

(First Embodiment) First, a first embodiment of the present invention will be described.

FIG. 1 shows a schematic configuration of an image forming apparatus according to the present embodiment.

The image forming apparatus according to the present embodiment is a black-and-white digital copying machine having a process speed of 470 mm / sec and 90 sheets per minute, and a photosensitive drum serving as a latent image carrier, which is an a-Si drum photosensitive member of φ108. 1 is provided.

In this image forming apparatus, as shown in FIG. 1, after the photosensitive drum 1 serving as a latent image carrier is uniformly charged to, for example,
Image exposure 12 is performed at dpi. The image exposure 12 is a laser beam modulated by an image signal using a semiconductor laser as a light source. The laser beam is polarized by a polygon mirror (not shown) rotating at a constant rotation speed by a motor (not shown). After passing through an image lens (not shown),
After being reflected by a folding mirror (not shown), the photosensitive drum 1 is raster-scanned to attenuate the surface potential of the exposed portion to, for example, +50 V to form an image-like latent image. The wavelength of the laser beam in the present embodiment is 680 mm.

Thereafter, the developing device 2 develops the latent image as a toner image. In the present embodiment, the development using a black magnetic one-component developer is a simple and highly durable development method requiring no maintenance until the development sleeve life reaches 2,000 k sheets. Reversal development is performed using two developer carriers with the downstream developing sleeve 30 as a developer carrier. Further, in the present embodiment, when the toner as the developer near the stirring bar 2B shown in FIG. 2 is exhausted, the piezoelectric element 22 detects it and
By rotating the mag roller 24, the toner in the hopper 9B is supplied to the developing device 2.

After the electrostatic latent image on the photosensitive drum 1 is visualized as a toner image by the developing device 2, the toner image is
A difference current of +100 is obtained by the post charger 10 serving as a charging means.
After charging with μA (AC + DC) and weakening the attraction force with the photosensitive drum 1 to facilitate transfer and separation,
The image is transferred by a transfer charger 4 as a transfer unit to a transfer material as a recording material that advances in the direction of the arrow.

The transfer material to which the toner image has been transferred is separated from the photosensitive drum 1 by the separation charger 5, and then sent to the fixing device 7, where the toner image is fixed.

Next, the developing device 2 of the present embodiment will be described in detail.

In the developing device 2 of this embodiment, the upstream developing sleeve 20 and the downstream developing sleeve 30 are
As shown in (a), they are arranged close to each other and rotate in the same direction (the direction of the arrow in the figure).

First, the points of the present invention will be described.

Conventionally, when a two-component developer having a toner and a carrier is used, the flow of the developer on the developer carrier is, as shown in FIG.
The developer is transferred from the upstream developer carrier to the downstream developer carrier in the vicinity of the two developer carriers. That is, the developer is transported on the developing sleeve on the side facing the latent image carrier. This is because, when a two-component developer is used, the toner is mainly charged by the carrier, so that the developer only needs to be transported from the developer carrier to the latent image carrier.

However, in the case of using a magnetic one-component type developer in which the developer carrier mainly contributes to the charging of the developer, the developer is coated on the developer carrier in a thin layer and is sufficiently coated. Since it is necessary to charge the developer, the flow of the developer on the downstream developer carrier is as shown in FIG. 4A, which is clearly different from the case where the two-component developer is used. In addition to transporting the developer from the developer to the latent image carrier, the developer coat on the developer carrier must be uniform and charged.

Therefore, in the present embodiment, as shown in FIG. 3B, the magnetic pole A as the first magnetic pole disposed in the vicinity of the photosensitive drum 1 in the upstream developing sleeve 20 or in the vicinity thereof, Downstream developing sleeve 3 in developing sleeve 20
A magnetic pole B as a second magnetic pole disposed in the vicinity of or near 0, and a magnetic pole C as a third magnetic pole disposed in the vicinity of or in the vicinity of the upstream developing sleeve 20 in the downstream developing sleeve 30; have.

The relationship between these magnetic poles is as follows: magnetic pole A and magnetic pole C have the same polarity, magnetic pole B has a different polarity from magnetic pole A and magnetic pole C, and | magnetic force of magnetic pole A |> | magnetic force of magnetic pole B> | Magnetic force of magnetic pole C |.

Thus, in the present embodiment, the toner coat on the upstream developing sleeve 20 is stabilized.

Here, the relationship between the magnetic force and the polarity of the first magnetic pole, the second magnetic pole, and the third magnetic pole will be described.

First, the second magnetic pole and the third magnetic pole will be described. Here, the arrangement of the second magnetic pole and the third magnetic pole shown in FIG. 4B was changed, and the polarity of the second magnetic pole and the third magnetic pole was changed to examine the state of the developer coat on the upstream developer carrier. .
The magnetic force of each of the second magnetic pole and the third magnetic pole is 70 mT.

Table 1 shows the results regarding the polarities of the second and third magnetic poles and the state of the developer coat on the upstream developer carrier.

[0044]

[Table 1] According to Table 1, when the first magnetic pole and the second magnetic pole have different polarities, the developer coat on the upstream developer carrier is stable.

If there is a region of magnetic force of 0 to 10 mT on the downstream developer carrier side of the upstream developer carrier, there is no developer conveying force in this region, so that the developer stays on the developer carrier. As a result, a coat failure state as shown in FIG. In particular, when a developer carrier that rotates at a high speed is used, this phenomenon becomes remarkable because the developer transport speed cannot keep up. Further, when the first magnetic pole and the second magnetic pole have the same polarity, the area of the magnetic force of 0 to 10 mT is further increased, so that the above-mentioned stagnation of the developer becomes remarkable.

Therefore, it is necessary that the first magnetic pole and the second magnetic pole have different polarities.

Next, the relationship between the first magnetic pole and the third magnetic pole will be described.

The first magnetic pole is a magnetic pole that contributes to development,
As shown in Table 2, usually, to prevent image fog,
The magnetic force needs to be 80 mT or more.

[0049]

[Table 2] When the magnetic force of the first magnetic pole is equal to the magnetic force of the third magnetic pole, a region of a magnetic force of 0 to 10 mT exists on the upstream developer carrier at the portion where the first magnetic pole faces the upstream developer carrier and the downstream developer carrier. Therefore, it is desirable to reduce the magnetic force of the third magnetic pole and bring the position of the magnetic force of 0 to 10 mT formed by the first magnetic pole and the third magnetic pole closer to the second magnetic pole. Further, in order to increase the developer conveying force during this period, the influence of the magnetic force of the third magnetic pole can be reduced by making the second magnetic pole stronger than the third magnetic pole. In addition, regarding the relationship between the magnetic force of the first magnetic pole and the magnetic force of the second magnetic pole, these are of different polarities, and it is preferable that one of the magnetic forces is large in order to increase the developer conveying force.
It is preferable that the magnetic force of the first magnetic pole be larger than the condition of magnetic force of the first magnetic pole ≧ 80 mT. Therefore, the magnetic force of the first magnetic pole> the magnetic force of the second magnetic pole.

Therefore, the relationship between these magnetic forces for reducing the region of the magnetic force of 10 mT or less formed on the upstream developer carrier by the first magnetic pole, the second magnetic pole, and the third magnetic pole is as described above. As described above, unlike the case where the two-component type developer is used, the positions of the second magnetic pole and the third magnetic pole are examined, and as a result, the rotational center of the upstream developer carrier and the downstream developer carrier are examined. If the second magnetic pole and the third magnetic pole are brought out of the latent image carrier (outside of the developing device) beyond the line connecting the rotation center of the body, it becomes difficult to stably charge the developer in the downstream developer carrier. It is more desirable to arrange the magnetic pole and the third magnetic pole on the inner side of the developing device (farther from the latent image carrier) than the above-mentioned lines.

Here, a description will be given of the result of the study on the first magnetic pole, the second magnetic pole, and the third magnetic pole for preventing the developer from staying on the upstream developer carrier. Here, the magnetic force of the third magnetic pole was gradually changed from 40 mT by 10 mT, and the coating state on the upstream developer carrying member in the combination of the first magnetic pole and the third magnetic pole at this time was evaluated by ○ or ×. Regarding the evaluation here, the state as shown in FIG. 5 (a) is x, and the state as shown in FIG. 5 (b) is ○. The evaluation criteria are as follows: fog (か: less than 2%, x: 2% or more), coat stability (x: halftone image (reflection density D: 0.5)), and the uneven density difference 0.1 or more).

As a result, the results shown in Table 3 were obtained.

[0053]

[Table 3] Each table in Table 3 shows that the magnetic force of the third magnetic pole is reduced from 40 mT to 1
This shows the developer coatability on the upstream developer carrying member when changed to 00 mT. This is the coating property when 10k sheets are durable in the actual machine.

According to Table 3, the first magnetic pole and the second magnetic pole have the same polarity, the second magnetic pole has a different polarity from the first magnetic pole and the third magnetic pole, and the magnetic force of the magnetic pole A |> | the magnetic force of the magnetic pole B | > | Magnetic force of magnetic pole C |, it can be seen that the developer coatability on the upstream developer carrier is stable.

The angle θ shown in FIG. 3A was 5 °. In addition, the same examination was performed with the angle θ of 0 to 20 °, but these relationships were qualitatively the same.

In the present embodiment, the upstream developing sleeve 20 has a magnetic pole configuration as shown in Table 4, and the downstream developing sleeve 30
Has a magnetic pole configuration as shown in Table 5.

[0057]

[Table 4]

[0058]

[Table 5] The upstream developing sleeve 20 is made of a non-magnetic member of φ20 S
After blast processing is performed on US 305 with FGB # 600, coating is performed as shown in FIG.

FIG. 3 shows the inside of the upstream developing sleeve 20.
(A) and a magnet 20B as a magnetic member having a magnetic field pattern as shown in Table 4 is fixedly arranged. The upstream developing sleeve 20 is set at 1 to the peripheral speed of the photosensitive drum 1.
It rotates at a peripheral speed of 50%.

The layer thickness of the toner on the upstream developing sleeve 20 is regulated by the magnetic blade 20A. In the present embodiment, the distance S-Bgap between the upstream developing sleeve 20 and the magnetic blade 20A is set to 250 μm.

The distance S-Dgap between the upstream developing sleeve 20 and the photosensitive drum 1 is 200 μm. In the present embodiment, +3 is applied by bias applying means (not shown).
With a DC bias voltage of 00V and a waveform as shown in FIG.
A single-component magnetic non-contact development is performed by superimposing a rectangular wave AC bias voltage having a pp of 1200 V and a frequency of 2.5 kHz and applying the superposed voltage to the upstream developing sleeve 20. Therefore, the development contrast is 200 V in the flight direction and the fog removal contrast is 150 V.

Similarly to the upstream developing sleeve 20, the downstream developing sleeve 30 is a SUS305 of φ20 which is a non-magnetic member.
Blasting with FGB # 600 on the
z is 3 μm. In addition, the contact type surface roughness meter (Surfcoder SE-3300, Kosaka Laboratory) was used for the measurement of Rz. The measurement conditions are a cutoff value of 0.8 mm, a measurement length of 2.5 mm, a feed speed of 0.1 mm / sec, and a magnification of 5000.

FIG. 3 shows the inside of the downstream developing sleeve 30.
A magnet 30B as a magnetic member having a four-pole magnetic field pattern shown in FIG.

A DC bias voltage of +300 V and Vpp12 with a waveform as shown in FIG.
A rectangular wave having a frequency of 00 V and a frequency of 2.5 kHz can be superimposed and applied. In the present embodiment, since the developing bias voltage applied to the downstream developing sleeve 30 is the same as the developing bias voltage applied to the upstream developing sleeve 20, the power source for the bias applying means is shared to reduce the cost to one. In addition, since the space for the power supply is small, the space can be saved.

The downstream developing sleeve 30 rotates at a peripheral speed of 150% of the peripheral speed of the photosensitive drum 1.

The layer thickness of the toner on the downstream developing sleeve 30 is regulated by the upstream developing sleeve 20. In the present embodiment, the S-D of the downstream developing sleeve 30 and the photosensitive drum 1
Dgap is 250 μm.

In this embodiment, as shown in FIG. 8A, the upstream developing sleeve 20 has a magnet 20B having four magnetic poles inside, and the downstream developing sleeve 30 has a magnet 30B having four magnetic poles. FIG. 8 shows a magnetic seal member 2D formed along the outer peripheries of the upstream development sleeve 20 and the downstream development sleeve 30 and made of moldalloy (KN plating, magnetic permeability 10-6) mainly made of iron.
As shown in FIG. 3B, the upstream developing sleeve 20 and the downstream developing sleeve 30 are provided near both ends in the axial direction. The gap between the surfaces of the upstream developing sleeve 20 and the downstream developing sleeve 30 and the magnetic seal member 2D is 400 μm ±
It is 100 μm.

In this embodiment, the length of the magnet 20B in the axial direction of the upstream developing sleeve 20 and the downstream developing sleeve 30 is L1 = 305 mm, and the length of the magnet 30B is L2 = 305 mm.

Regarding the appropriate mounting position of the magnetic seal member 2D with respect to the magnets 20B, 30B, the position of the outer end of the magnetic seal member 2D in the axial direction of the upstream developing sleeve 20 and the downstream developing sleeve 30 and the magnets 20B, 30B It is most preferable to match the position of the end portion with the end position. This is because, when the magnets 20B and 30B protrude outward from the position of the axial outer end of the magnetic seal member 2D, a magnetic force is present outside the longitudinal direction (the axial direction). This causes the toner to be carried out and causes toner leakage.
Also, the magnetic seal member 2D is originally intended to form a magnetic brush between the magnetic seal member 2D and the magnets 20B, 30B to eliminate toner leakage. Conversely, the magnetic seal member 2D is located outside the magnetic seal member 2D in the axial direction. If the positions of the ends of the magnets 20B and 30B are too close to the positions of the ends, the magnetic force of the magnetic seal member 2D does not exist at the outer end of the magnetic seal member 2D.
In order to form a magnetic brush on the upstream developing sleeve 20 and the downstream developing sleeve 30 with the width of the magnetic seal member 2D, the toner located at the outer end leaks from the end and simultaneously the upstream developing sleeve 20 and the downstream developing sleeve. Sleeve 3
This is because the thickness of the toner layer above 0 becomes large, and the toner may fall off. In the present embodiment, since there is play in the longitudinal direction due to the relationship between the upstream developing sleeve 20 and the downstream developing sleeve 30 and the magnets 20B, 30B, etc., as shown in FIG. Magnet 20
The outer end of the magnetic seal member 2D was located at a position 1 mm inward from the end positions of B and 30B.

Next, the image processing in this embodiment will be described.

In the present embodiment, the image signal control section shown in FIG. 9 performs image processing as follows by binarization using the dither method.

The image processing unit 201, as shown in FIG.
The input image signal is subjected to image processing desired by the operator, such as resolution conversion.

The γ correction section 202 applies L
Look-up table (LU) by the UT calculation unit 205
Gamma correction is performed with reference to T).

Then, the binary processing unit 203
A laser drive signal is generated based on the corrected image signal.

The laser unit 204 is driven based on the drive signal output from the binary processing unit 203, and the image exposure 12 corresponding to the image is performed as described above. In the present embodiment, L in the γ correction unit 202 is compared with the development contrast.
The UT is set by the LUT calculation unit 205 so as to be appropriate in the current operating environment.

In this embodiment, as described above, in addition to an appropriate development contrast, an appropriate gradation correction (for example, γ correction) is performed. Then, the obtained tone characteristic is an ideal density reproduction curve (TRC; tone reproductivity).
LUT calculation unit 205 so as to be “on curve”.
Update the LUT of the γ correction unit 202

The effect of the present embodiment is the same as in the case of performing normal development using a negative photosensitive drum and a positive toner.

Further, in this embodiment, since the developing bias voltage of the AC component is applied to the developer carrier, the portion that is excessively developed by the upstream developing sleeve 20 is again transferred into the developing device 2 by the downstream developing sleeve 30. Since it can be returned, the toner consumption can be reduced. The toner consumption was measured on a 6% original image, and was 50 to 60 mg / sheet in a developing device using a conventional magnetic one-component developer, but was 41 mg / sheet in the present embodiment.

Thus, according to the present embodiment, in a maintenance-free compact developing device using a magnetic one-component toner, uniform and stable coating of the developer on the upstream developer carrier is realized, and high image quality is achieved. To provide a developing device with low toner consumption while maintaining a stable density at
In addition, by using a compact developing device that saves space in a high-speed machine, it is possible to provide a small-sized high-speed machine suitable for print-on-demand.

(Second Embodiment) Next, a second embodiment of the present invention will be described. The description of the same configuration as that of the first embodiment is omitted.

Generally, it is difficult to control the triboelectricity of the developer when the surface of the developing sleeve is SUS or the aluminum tube, but in the present embodiment, in consideration of this, the upstream developing sleeve, which is the upstream developer carrying member, and the downstream developer carrying In order to control the toner tribo by the downstream developing sleeve, which is the body, the optimal coating formula is adopted for each of the upstream developing sleeve and the downstream developing sleeve,
A negatively chargeable magnetic one-component toner is used.

The magnetic pole of the upstream developing sleeve has a five-pole configuration in consideration of toner transportability, and forms a repulsive pole in the developing device of the upstream developing sleeve so that the toner is once separated from the developing sleeve by a large mass. The rotation of the toner to the developing sleeve is reduced. The coating on the surface of the developing sleeve is for preventing the sleeve ghost image generated in the cycle of the developing sleeve, which is a problem in JP-A-3-36570 and the like, and for enhancing the durability of the surface of the developing sleeve (protecting the Al surface). Membrane). The distance d between the developing sleeves in this embodiment is 60.
It was set to 0 μm.

This image forming apparatus uses a latent image carrier
The a-Si drum photoconductor of φ108 is used.
As in the embodiment, the process speed is 470 mm / sec.
c, a black and white digital copier of 90 sheets per minute. This embodiment
Developer is a negatively charged toner having a weight average particle size of 7.5 μm.
1.0% (% by weight) of SiO 2 as an external additive _Two
Is painted.

In this embodiment, the coating film of the developing sleeve is prepared by mixing a phenol resin, crystalline graphite and carbon on the surface of the Al developing sleeve to form a film having a thickness of 10 μm.
At 150 ° C. was used. The thickness of the film is about 20 μm for forming a stable and uniform film. In this case, the P / B ratio is 1 / 2.5. here,
B represents the weight of the resin, and P represents the weight of other than the resin (crystalline graphite + carbon).

When the amount of toner coating on the downstream developing sleeve is regulated by the upstream developing sleeve as in this configuration, the quaternary ammonium salt is applied only to the downstream developing sleeve because the charging characteristic for the negative toner is too high. A phenol resin having 70 parts by weight was used.

When the quaternary ammonium salt compound is added, the quaternary ammonium salt compound is uniformly dispersed in the phenol resin, and is further incorporated into the structure of the phenol resin when a film is formed by heating and curing. The phenolic resin composition itself having the above-mentioned property changes to a substance having a negative chargeability. Therefore, if a developer carrier having a coating layer formed using such a material is used, the developer can be suitably charged to a positive polarity.

The quaternary ammonium salt compounds suitably used in the present invention and having the above-mentioned functions include:
For example, a compound represented by the following general formula may be mentioned.

[0088]

Embedded image R1, R2, R3, and R4 in the formula shown in Chemical Formula 1 represent an alkyl group which may have a substituent, an aryl group which may have a substituent, and an aralkyl group, respectively, and R1 to R4 each represent They may be the same or different. X- represents an anion of an acid.

In the general formula shown in the above formula 1, specific examples of the acid ion of X- include organic sulfate ion, organic sulfonate ion, organic phosphate ion, molybdate ion, tungstate ion, molybdenum atom or tungsten atom. Heteropoly acids containing atoms are exemplified.

[0090]

Embedded image As shown in the chemical formula 2, when a coating layer is formed using a resin composition obtained by adding a specific quaternary ammonium salt compound used in the present invention to a phenol resin, as described above, the resin is a binder resin. When the phenol resin is cured by heating to form a coating layer, the quaternary ammonium salt compound is incorporated into the structure of the phenol resin. For this reason, the above-mentioned negative silica particles or negative Teflon (registered trademark)
Unlike the case of a particle-added system such as particles, the positive triboelectric charge imparting property to the positively chargeable developer is improved not partially but entirely as a coating layer. Further, unlike the particle-based coating film, there is no loss of workability and no reduction in the strength of the coating layer.

Specific examples of the quaternary ammonium salt compound suitably used in the present invention include the following, but of course, the present invention is not limited thereto.

[0092]

Embedded image

[0093]

Embedded image

[0094]

Embedded image

[0095]

Embedded image

[0096]

Embedded image

[0097]

Embedded image

[0098]

Embedded image

[0099]

Embedded image As the phenolic resin constituting the binder resin used in the present invention, when a phenolic resin produced by using a nitrogen-containing compound as a catalyst is used in the production process, the quaternary ammonium salt compound is particularly useful when the phenolic resin is heated and cured. It was found that the toner was easily taken into the structure of No. 1 and was preferable for preventing charge-up of the toner. Therefore, in the present invention, if a phenol resin produced by using a nitrogen-containing compound as a catalyst in the production process having such an effect is used as one of the materials constituting the coating layer on the developer carrying member. Thus, it is possible to realize a developing device that prevents toner charge-up.

Examples of the nitrogen-containing compound which can be suitably used in the present invention and which is used as a catalyst in the process of producing a phenolic resin include, for example, ammonium sulfate, ammonium phosphate, ammonium sulfamate, ammonium carbonate, ammonium acetate, and the like. Examples of the basic catalyst include ammonia or dimethylamine, diethylamine, diisopropylamine, diisobutylamine, diamylamine, trimethylamine, triethylamine, tri-n-butylamine, and triamylamine. Dimethylbenzylamine, diethylbenzylamine, dimethylaniline, diethylaniline,
N, N-di-n-butylaniline, N, N-diamylaniline, N, N-di-t-amylaniline, N-methylethanolamine, N-ethylethanolamine, diethanolamine, triethanolamine, dimethylethanolamine, Diethylethanolamine, ethyldiethanolamine, n-butyldiethanolamine, di-n-butylethanolamine, triisopropanolamine,
Amino compounds such as ethylenediamine, hexamethylenetetramine, pyridine, α-picoline, β-picoline, γ
Pyridine such as picoline, 2,4-lutidine and 2,6-lutidine and derivatives thereof, quinoline compounds, imidazole, 2-methylimidazole, 2,4-dimethylimidazole, 2-ethyl-4-methylimidazole, 2-phenyl Nitrogen-containing heterocyclic compounds such as imidazole, imidazole such as 2-phenyl-4-methylimidazole, and 21-heptadecyl imidazole and derivatives thereof, and the like.

In the present invention, in order to adjust the resistance value of the coating layer to the above value, it is preferable that the following conductive substances are contained in the coating layer. As the conductive substance used at this time, for example, aluminum, copper, nickel, metal powder such as silver, antimony oxide, indium oxide, metal oxide such as tin oxide, carbon fiber,
Carbon materials such as carbon black and graphite are exemplified. In the present invention, among these, carbon black, especially conductive amorphous carbon, is particularly excellent in electric conductivity, and is filled with a polymer material to impart conductivity, or only by controlling the addition amount, It is preferably used because a certain degree of dragon conduction can be obtained.

The final film formulation was phenolic resin 250
Graphite 90 having an average particle size of 7.5 μm based on parts by weight
Parts by weight, 10 parts by weight of carbon and 70 parts of quaternary ammonium. By the way, the ratio of graphite to carbon is 3% of carbon to stabilize the resistance of the whole film.
It is preferable that it be twice or more. After the film is applied to the developing sleeve by a spraying method, it is dried at 150 degrees for 30 minutes.

By optimizing the coat, the triboelectric charge (charge amount) on the downstream developing sleeve side is usually large, whereas in the present embodiment, 9 μC /
g, a value almost equal to 9.2 μC / g on the downstream developing sleeve could be controlled. Due to this, high temperature and high humidity,
The development characteristics are stabilized because both development sleeves are optimized for environmental changes such as room temperature and low humidity.

In the inside of the upstream developing sleeve 20, FIG.
As shown in Table 6, a magnet having a 5-pole magnetic field pattern is fixedly arranged.

[0105]

[Table 6] The upstream developing sleeve 20 rotates at a peripheral speed of 125% of the peripheral speed of the photosensitive drum 1. The layer thickness of the toner on the upstream developing sleeve 20 is regulated by the magnetic blade 20A. The distance S-Bgap between the upstream developing sleeve 20 and the magnetic blade 20A is 250 μm. The distance S-Dgap between the upstream developing sleeve 20 and the photosensitive drum 1 is 250 μm. In this embodiment, a DC bias voltage of −550 and an AC bias voltage of Vpp 1500 V having a waveform as shown in FIG. 7 and a rectangular wave having a frequency of 2.7 kHz are applied to the upstream developing sleeve 20 to perform magnetic one-component non-contact development. It is supposed to do. Therefore, the development contrast is 350 V in the flight direction and the fog removal contrast is 150 V.

The downstream developing sleeve 30 is formed by forming a film on aluminum A2017 of φ20 which is a non-magnetic member. FIG. 10 and Table 7 show the inside of the downstream developing sleeve 30.
And a magnet having the four-pole magnetic field pattern shown in FIG.

[0107]

[Table 7] A DC bias voltage of -550 V and a rectangular wave having a Vpp of 1500 V and a frequency of 2.7 kHz are applied to the downstream developing sleeve 30 with a waveform as shown in FIG. Downstream developing sleeve 3
Since the AC bias voltage and the DC bias voltage applied to 0 are the same as the AC bias voltage and the DC bias voltage applied to the upstream developing sleeve 20, the cost can be reduced by sharing the power source and using one. There is an advantage that the space for the power supply can be reduced as well as possible. The downstream developing sleeve 30 rotates at a peripheral speed of 125% of the peripheral speed of the photosensitive drum 1.

The thickness of the toner on the downstream developing sleeve 30 is regulated by the upstream developing sleeve 20. Distance d between upstream developing sleeve 20 and downstream developing sleeve 30
Is 600 μm.

The magnetic pole configurations of the upstream developing sleeve 20 and the downstream developing sleeve 30 are five poles and four poles, respectively, as shown in Tables 6 and 7. The reason why the number of magnetic poles of the upstream developing sleeve 20 is five is as described above.

Therefore, according to the present embodiment, in a maintenance-free compact developing device using a magnetic one-component toner, uniform and stable coating of the developer on the upstream developer carrier is realized, and high image quality and stable To provide a developing device that consumes a small amount of toner while maintaining the density, and a compact developing device that saves space in a high-speed machine, thereby providing a high-speed machine suitable for a small-size print-on-demand type. be able to. Further, toner deterioration on the upstream developer carrying member can be reduced by reducing the rotation of the toner, and the charge can be controlled by using a coating formulation optimal for the charging characteristics of these toners.

(Third Embodiment) Next, a third embodiment of the present invention will be described. In addition, about the structure similar to 1st Embodiment or 2nd Embodiment, the description is abbreviate | omitted.

The developing device according to this embodiment is the same as that of the second embodiment.

The feature of the present embodiment is that the developing device of the present invention is applied to a reuse image forming apparatus.

The reuse toner is basically a waste toner that is not transferred and is collected by the remaining cleaning. Therefore, compared with new toner due to deterioration, the amount of the reversal component toner is extremely small. Due to the large number, the scattering becomes worse. The present embodiment has been implemented in view of these points.

The prescription of the magnetic poles of the upstream developing sleeve and the downstream developing sleeve and the coating material in this embodiment is the same as in the second embodiment.

The image forming apparatus according to the present embodiment is similar to the image forming apparatus shown in FIG.
Process speed of 500 in the image forming system shown in FIG.
This is a digital copying machine of 110 sheets / min of mm / s, and has a photosensitive drum 1 as a latent image carrier using an a-Si drum as a photosensitive member.

In such an image forming apparatus, the surface of the photosensitive drum 1 is uniformly charged to -700 V by the primary charger 3.

Next, the uniformly charged surface of the photosensitive drum 1 is irradiated with a semiconductor laser having a wavelength of 680 μm by 600 dpi.
Performs image exposure 12 by PWM, and the photosensitive drum 1
An electrostatic latent image is formed thereon.

Next, the electrostatic latent image is regularly developed by the developing device 2 and visualized as a toner image. The developing device of this embodiment employs a jumping development method using a magnetic one-component negative toner having a toner particle diameter of 8.0 μm as a developer. This is because, in the conventional two-component developer, the carrier must be replaced every 100,000 sheets by a serviceman, and is not maintenance-free. On the other hand, in this embodiment, a dry magnetic one-component toner having infinite durability and requiring no maintenance is used. The developing bias voltage is applied to the upstream developing sleeve 20.
And the downstream developing sleeve 30 are both 2400 Hz, 1500
Vpp, Duty 50% AC bias voltage +200
A developing bias voltage on which a DC bias voltage of V is superimposed is applied. In this embodiment, the distance S-Bgap between the upstream developing sleeve 20 and the magnetic blade 20A is 250 μm, and the distance S-Dgap between the upstream developing sleeve 20 and the downstream developing sleeve 30 and the photosensitive drum 1 is both 250 μm.
μm.

Thereafter, the toner image is charged by the post-charger 10 serving as a charging means and supplied with a total current of -200 μA, and then transferred by a transfer charger 4 serving as a transfer means to a transfer material serving as a recording material which advances in the direction of the arrow. Is done.

The transfer material to which the toner image has been transferred is separated from the photosensitive drum 1 by the separation charger 205, and then conveyed to the fixing device 7, where the toner image is fixed.

On the other hand, the transfer residual toner on the photosensitive drum 1 is removed from the photosensitive drum 1 by the cleaning device 6 as a removing means and collected, and returned to the developing hopper 9B as waste toner (reuse toner) through the transport pipe 8. It is.

A screw-shaped conveying member is disposed inside the conveying pipe 8, and the reused toner is conveyed to the developing hopper 9B by the rotation of the conveying member.
Thus, as shown in FIG. 11, the reused toner carried by the carrying member of the carrying pipe 8 is supplied to the developing hopper 9B.
And reused. Further, new toner separately from the reused toner is put into the hopper 9A, and the respective toners are attracted by the magnetic force by the mag rollers 24A and 24B, and the respective toners are stored in the developing device 2 by the rotation of the mag rollers 24A and 24B. Carried. In the present embodiment, the method of mixing the reuse toner and the new toner in the developing device is adopted. However, a space for mixing in the hopper may be provided, and the mixing may be performed in the space.

The toner mixed in the developing device 2 is sent to the upstream developing sleeve 20 and the downstream developing sleeve 30 again to be used for developing the electrostatic latent image on the photosensitive drum 1. In the present embodiment, the normal rotation speed of the mag roller 24A is 2 rotations / minute, and the rotation speed of the mag roller 24B is changed at a predetermined ratio to the rotation speed of the mag roller 24A.
In this embodiment, the piezo sensor (manufactured by TDK) provided in the developing device 2 does not receive the weight of the toner, and the signal from the piezo sensor vibrates.
To rotate A and 24B, a toner supply signal is issued. Normally, the mag roller 24B rotates at a rotation speed of 10/90 (the rotation speed of the mag roller 24A: the rotation speed of the mag roller 24B = 9: 1) with respect to the rotation speed of the mag roller 24A.

In this embodiment, the distance d is 800 μm. The magnetic force of N2 (magnetic pole A) arranged in the magnet 20B of the upstream developing sleeve 20 is 80 mT, and the magnetic force of S1 (magnetic pole B) arranged in the magnet 30B of the downstream developing sleeve 30 is 75 mT. Further, the magnetic pole A
And N1 (magnetic pole C) disposed in or near the photosensitive drum 1 in the magnet 30B have the same polarity, and the magnetic pole B has a different polarity from the magnetic poles A and C.

The magnetic poles A and B are located inside the developing device 2 (far side of the photosensitive drum 1) with respect to a line connecting the rotation center of the upstream developing sleeve 20 and the rotation center of the downstream developing sleeve 30. ing. Further, the angle θ shown in FIG.
Is 10 °.

In the present embodiment, the relationship between the magnetic force [mT] of the magnetic pole A, the magnetic force [mT] of the magnetic pole B, and the distance d [μm] is 0.5 ≧ (80 + 75) /800≧0.2 Therefore, the toner coatability on the downstream developing sleeve 30 is stabilized.

Therefore, according to the present embodiment, in a maintenance-free toner-reuse compact developing device using a magnetic one-component toner, uniform and stable coating of the developer on the upstream developer carrier is realized, and high image quality is achieved. To provide a developing device that consumes a small amount of toner while maintaining a stable density in a high-speed machine and a compact developing device that saves space in a high-speed machine. Can be provided.

[0129]

As described above, according to the first aspect of the present invention, the polarities and magnetic forces of the first magnetic pole, the second magnetic pole, and the third magnetic pole are optimized. In a developing device having a development carrier and employing a one-component developer, a magnetic one-component developer is provided on an upstream developer carrier on an upstream side in a rotation direction of a latent image carrier among two adjacent developer carriers. Can be uniformly and stably coated.

According to the second invention of the present application,
Since the first magnetic pole, the second magnetic pole, the polarity and magnetic force of the third magnetic pole, and the distance between the upstream developer carrier and the downstream developer carrier have been optimized, a plurality of developer carriers are required. In a developing device that employs a one-component developer, a magnetic one-component developer is placed on an upstream developer carrier that is upstream of two adjacent developer carriers in the rotational direction of the latent image carrier. Coating can be performed uniformly and stably.

Further, according to the third aspect of the present invention, since the polarities and magnetic forces of the first magnetic pole, the second magnetic pole, and the third magnetic pole are optimized, a plurality of developing carriers can be provided. In a developing device that employs a component-based developer, a magnetic one-component developer is uniformly spread on an upstream developer carrier that is located upstream of the two adjacent developer carriers in the rotational direction of the latent image carrier. It can be coated stably.

According to the fourth invention of the present application,
Since the polarities and magnetic forces of the first magnetic pole, the second magnetic pole, and the third magnetic pole are optimized, two adjacent developing units are used in a developing device including a plurality of developing carriers and employing a one-component developer. The magnetic one-component developer can be uniformly and stably coated on the upstream developer carrier in the rotation direction of the latent image carrier in the developer carrier.

Further, according to the fifth aspect of the present invention, since the polarities and magnetic forces of the first magnetic pole, the second magnetic pole, and the third magnetic pole are optimized, a plurality of developing carriers can be provided. In a developing device that employs a component-based developer, a magnetic one-component developer is uniformly spread on an upstream developer carrier that is located upstream of the two adjacent developer carriers in the rotational direction of the latent image carrier. It can be coated stably.

Further, according to the sixth invention of the present application,
Since the polarities and magnetic forces of the first magnetic pole, the second magnetic pole, and the third magnetic pole are optimized and the surface of the developer carrier is protected, a one-component system including a plurality of developer carriers is provided. In the developing device employing the above-mentioned developer, the magnetic one-component type developer is uniformly stabilized on the upstream developer carrier on the upstream side in the rotation direction of the latent image carrier among two adjacent developer carriers. Can be coated.

Further, according to the seventh aspect of the present invention, since the polarities and magnetic forces of the first magnetic pole, the second magnetic pole, and the third magnetic pole are optimized, a plurality of developing carriers can be provided. In a developing device that employs a component-based developer, a magnetic one-component developer is uniformly spread on an upstream developer carrier that is located upstream of the two adjacent developer carriers in the rotational direction of the latent image carrier. It can be coated stably.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view illustrating a schematic configuration of an image forming apparatus according to a first embodiment of the present invention.

FIG. 2 is a schematic sectional view showing a schematic configuration of a developing device provided in the image forming apparatus of FIG.

FIG. 3 is a diagram for explaining a magnetic pole arrangement of a magnetic member provided inside a developer carrier of the developing device of FIG. 2;

FIG. 4A is a diagram for explaining movement of a developer on a developer carrier when a one-component developer is used, and FIG. 4B is a diagram for explaining a two-component developer. FIG. 9 is a diagram for explaining movement of a developer on a developer carrier when used.

FIG. 5 is a diagram for explaining the relationship between the position and polarity of a magnetic pole of a magnetic member of a developer carrying member and the coatability of a developer on an upstream developer carrying member.

6 is a diagram for explaining a coating member of a developer carrier provided in the developing device of FIG. 2;

FIG. 7 is a diagram illustrating a waveform of an AC component of a bias voltage applied to a developer carrier according to the first embodiment of the present invention.

FIG. 8 is a diagram for explaining an arrangement of a magnetic member of a developer carrier and a seal at an axial end of the developer carrier in the first embodiment of the present invention.

FIG. 9 is a diagram for explaining image processing according to the first embodiment of the present invention.

FIG. 10 is a diagram illustrating a magnetic pole arrangement of a magnetic member provided inside a developer carrier of a developing device according to a second embodiment of the present invention.

FIG. 11 is a schematic sectional view illustrating a schematic configuration of an image forming apparatus according to a third embodiment of the present invention.

FIG. 12 is a schematic sectional view showing a schematic configuration of a conventional image forming apparatus.

13 is a schematic cross-sectional view illustrating a schematic configuration of a developing device provided in the image forming apparatus of FIG.

14 is a diagram for explaining the magnetic pole arrangement of a magnetic member provided inside a developer carrier of the developing device of FIG. 13;

[Explanation of symbols]

Reference Signs List 1 photosensitive drum (latent image carrier) 2 developing device 4 transfer charger (transfer unit) 6 cleaning device (cleaning unit) 20B, 30B magnet (magnetic member) 20 upstream developing sleeve (developer carrier, upstream developer carrier) ) 30 Downstream developing sleeve (developer carrier, downstream developer carrier)

 ──────────────────────────────────────────────────続 き Continued on the front page F-term (reference) 2H031 AA05 AC08 AC10 AC11 AC14 AC19 AC20 AC30 BA03 CA11 2H073 BA04 BA13 BA43 CA02 2H077 AA15 AA37 AD02 AD06 AD13 AD18 AD24 AD36 BA03 CA12 CA15 DA16 DA45 DA72 DB01 EA21 FA12 FA19

Claims (7)

[Claims] 1. A developing device for visualizing the latent image as a developer image by applying a magnetic one-component type developer to a rotating latent image carrier that carries a latent image on a surface thereof, the developing device comprising: A plurality of developer carriers that are disposed in close proximity to the carrier and that carry and rotate the developer on the surface; the plurality of developer carriers rotate in the same direction with each other to form two adjacent developer carriers; The upstream developer carrier on the upstream side in the rotation direction of the latent image carrier is close to the downstream developer carrier so that the amount of developer on the downstream developer carrier on the downstream side is regulated to a predetermined amount. In the developing device, each developer carrier has a magnetic member therein, and each magnetic member is located in the vicinity of the upstream developer carrier in the vicinity of the latent image carrier or in the vicinity thereof. The first magnetic pole arranged in the portion and the downstream developer carrying of the upstream developer carrying member A second magnetic pole disposed in the vicinity of the body or in the vicinity thereof, and a third magnetic pole disposed in the vicinity of the upstream developer carrier of the downstream developer carrier or in the vicinity thereof. The first magnetic pole and the third magnetic pole have the same polarity, the second magnetic pole has a different polarity from the first magnetic pole and the third magnetic pole, the magnetic force of the first magnetic pole is A, and the second magnetic pole is A developing device characterized by satisfying a relationship of | A |> | B |> | C | when the magnetic force of B is B and the magnetic force of the third magnetic pole is C. 2. The developing device according to claim 1, wherein the magnetic force A of the first magnetic pole is 80 mT or more, and the magnetic force B of the second magnetic pole and the magnetic force C of the third magnetic pole are each 50 mT or more. 3. The second magnetic pole and the third magnetic pole are located farther from the latent image carrier with respect to a line connecting the rotation center of the upstream developer carrier and the rotation center of the downstream developer carrier. The developing device according to claim 1 or 2, wherein 4. The method according to claim 1, wherein each developer carrier is configured to apply a bias voltage comprising an AC component and a DC component during development. Developing device. 5. The developer carrier according to claim 1, wherein the surface of each developer carrier is coated with a coating member having crystalline graphite and a phenol resin. Developing device. 6. An image forming apparatus for recording an image formed by a series of image forming processes on a recording material, comprising: a latent image carrier; and a developing device according to claim 1. And an image forming apparatus. 7. A transfer means for transferring a developer image on a latent image carrier to a recording material, and the developer image remaining on the latent image carrier after the transfer of the developer image to the recording material by the transfer means. 7. A cleaning device for removing a developer, wherein the developing device is configured to collect the developer removed from the latent image carrier by the cleaning device and make the developer reusable. An image forming apparatus according to claim 1.