JP2001022169A - Two-component developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize development with high image quality at high speed without causing image quality defects by using two-component developer. SOLUTION: By setting the amount of the developer drawn up onto the surface of a developing roller 3-1-1 to >=85 mg/cm2, a ring mark formation is prevented. Further, the roller 3-1-1 having a plurality of magnetic poles inside is arranged obliquely by 40 deg. to 70 deg. above a developer stirring member 3-2-2 and with a gap of 2 mm to 5 mm from the member 3-2-2. A pair of magnetic poles P4 and P5 arranged on both sides of a line linking the center of the roller 3-1-1 and the center of the member 3-2-2 are composed of magnetic poles having different polarity from each other, and, out of a pair of the magnetic poles, the magnetic force of the magnetic pole P4 which exists on the downstream side in the rotating direction of the roller 3-1-1 is set to >=50 mT and <=80 mT in a normal direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-component developing apparatus used in an electrophotographic image forming apparatus and for developing an electrostatic latent image with a two-component developer comprising a toner and a carrier.

[0002]

2. Description of the Related Art In a two-component developing apparatus for developing an electrostatic latent image with a two-component developer, for example, an image carrier and a developer carrier are used in order to perform high-speed and high-quality development with the two-component developer. There is a tendency that the gap is narrowed, a two-component developer is supplied onto the developer carrying member to form a thin layer, and development is performed by applying a high electric field AC bias.

[0003] However, with such a tendency, an image quality defect called a so-called ring mark tends to easily occur. The ring mark forms a gap for forming a thin layer of the two-component developer on the developer carrier, for example, when conductive powder passes, ionization occurs in a gap between the image carrier and the tip of the powder, It is considered that one factor is that the electrostatic latent image is destroyed and a ring-shaped or disk-shaped latent image defect is formed. Further, when the AC voltage value is large and the gap is small, the frequency of occurrence of the ring mark increases and the defect tends to increase as the powder size increases. Also, a jam may be cleared from a paper jam generated in the image forming apparatus, and a ring mark may be generated immediately after the process unit is replaced.
While progressing smoothly, it gradually decreased, but there was a situation in which a ring mark was generated again thereafter. In this method, when the clam shell is opened and closed, metal foreign matter adhering to the main body falls and is transferred to the photosensitive drum, reaches the developing device or the developing gap via the photosensitive drum, and generates a ring mark. In particular, in the color image forming apparatus, since the photosensitive drum rotates a plurality of times while releasing the pressure contact of the cleaning unit, the ratio of foreign matter passing through the cleaning is high, and ring marks are easily generated.

A method for solving this problem is disclosed in Japanese Patent Publication No. Hei 8-8.
No. 7172 and Japanese Patent Publication No. 7-97238. The method disclosed in Japanese Patent Publication No. 8-87172 is provided with a magnetic field generating means, which collects magnetic foreign matter that causes ring marks and reduces the occurrence of image quality defects. The method disclosed in Japanese Patent Publication No. 7-98238 is a technique for obtaining uniform image quality without fogging by defining the amount of magnetic particles on a developer carrying member.

[0005]

However, the above method has the following problems. An analysis of the ring mark revealed that the ring mark was caused by unevenness of the ears formed on the developing sleeve by the toner and magnetic particles. Further, a ring mark may not be generated even if conductive powder is intentionally applied on the developer carrying member, and it was confirmed that a ring mark was generated even without conductive powder. For this reason,
The method disclosed in Japanese Patent Publication No. 8-87172 cannot prevent the generation of a ring mark. In addition, when longer and shorter ears coexist on the developing sleeve due to uneven ears, ionization occurs in the gap between the shorter ear and the photosensitive drum that does not contact the photosensitive drum, and an electrostatic latent image is formed. It is broken to form a ring-shaped or disk-shaped (spot-shaped) latent image defect. In the method disclosed in Japanese Patent Publication No. 7-97238, the amount of magnetic particles present on the developing sleeve is specified. However, this amount causes non-uniform spikes and completely prevents the generation of ring marks. It cannot be prevented.

[0006] The present invention has been made in view of the above problems, and an object thereof is to use a two-component developer,
An object of the present invention is to provide a developing device capable of performing high-speed and high-quality development without causing image quality defects.

[0007]

In order to solve the above-mentioned problems, the invention according to claim 1 is arranged at a position close to and opposed to an image carrier on which an electrostatic latent image is formed on a surface, and is rotated. Supported, an alternating electric field is applied to the surface thereof, a developer carrier for carrying a two-component developer composed of toner and carrier, a developer accommodating section for accommodating the two-component developer, and stirring of the two-component developer. A developer stirring member for supplying the developer carrier to the developer carrier while developing the electrostatic latent image formed on the surface of the image carrier with the two-component developer. Provided is a two-component developing device in which an amount of a developer pumped on a body surface is 85 mg / cm ² or more.

According to a second aspect of the present invention, the developer carrier has a plurality of magnetic poles therein, and is obliquely above the developer stirring member by 40 to 70 degrees, and A pair of magnetic poles that are provided at a distance of 2 mm to 5 mm from the stirring member and that are arranged with a line connecting the center of the developer carrier and the center of the developer stirring member among the plurality of magnetic poles, 2. The two-component developing device according to claim 1, wherein the magnetic poles having different polarities, wherein, of the pair of magnetic poles, a magnetic pole downstream of the developer carrier in the rotation direction has a magnetic force of 50 mT or more and 80 mT or less in a normal direction. Provide equipment.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the two-component developing device of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram showing a photoconductor unit (PCU) in which the developing device is used. In this photoconductor unit, a charging roller 2 for uniformly charging the surface of the photoconductor 1 around the photoconductor 1 on the drum, and a surface of the uniformly charged photoconductor 1 is exposed to form a latent image. A developing unit 3 for forming a toner image by attaching a charged toner to a latent image formed on the photoconductor 1, a photoconductor shutter 5, and a recording sheet on which the toner image has been transferred to the photoconductor 1. Separation blade 6, a cleaning blade 7-1 for scraping toner remaining on photoconductor 1 after toner transfer, discharge screw 7-2 for discharging scraped residual toner, and photoconductor 1 after toner transfer.
A static elimination lamp 8 for sequentially erasing the electrification of the latent image by light is provided, and a transfer separation unit (not shown) is provided via a photoreceptor shutter 5. The photoconductor shutter 5 is
It is openable and closable, and covers the photoconductor when it is not set in the apparatus main body.

The developing section 3 comprises a developer carrying section 3-1 and a developer accommodating section 3-2. When the developing section 3 is not used, it is located between the developer carrying section 3-1 and the developer accommodating section 3-2. It is isolated by the provided seal member 3-2-1. The developer carrying section 3-1 includes a developing roller 3-1-1 which is a developer carrying body.
And a developing doctor 3-1-2 for controlling the amount of developer supplied to the photoconductor 1. The developing roller 3-1 is
A magnet roller formed in a cylindrical shape and fixedly supported,
The developing sleeve is formed around a magnet roller and is rotatably supported. The developer accommodating section 3-2 agitates the developer and supplies the developer to the developing roller 3-1-1 with the first agitating member 3-2-2, the second agitating member 3-2-4, and the toner in the developer. And a toner density sensor (magnetic permeability sensor) 3-2-3 for magnetically detecting the mixing ratio of the toner and the carrier, and contains a two-component developer.

FIG. 2 is a diagram showing the configuration of the vicinity of the photoreceptor of the photoreceptor unit. The transfer separation unit 10 includes a transfer roller and a static elimination needle. A P sensor 9 for detecting the image density of the density pattern created on the photoreceptor 1 and controlling toner supply to the developing unit 3 is provided between the transfer separation unit 10 and the developing unit 3. The toner supply control is performed according to the detection value of the toner concentration sensor 3-2-3 shown in FIG. 1 and the detection value of the P sensor 9 shown in FIG. Is supplied with toner.

The operation of the photosensitive unit will be described. After the photoconductor 1 is uniformly charged by the charging roller 2,
An electrostatic latent image is formed on the surface by exposure from exposure means,
The area where the electrostatic latent image is formed moves to the developing area facing the developer carrier 3-2 of the developing unit 3 as the photoconductor 1 rotates. In the developing section 3, the developer contained in the developer accommodating section 3-2 is agitated by the first developer agitating member 3-2-2 and the second developer agitating member 3-2-4 while the developing roller 3 is agitated.
-Supply to the 1-1 side. The developer supplied to the developing roller 3-1-1 is pumped up onto the developing roller 3-1-1 to form a spike of the developer. The electrostatic latent image on the photoconductor 1 that has moved to the development area is developed in contact with the ears of the developer to form a toner image. This toner image is transferred to the transfer paper conveyed to the transfer separation section. After the toner image is transferred, the transfer paper electrostatically attached to the photoconductor is separated from the photoconductor by discharge from the separation unit or by the separation claw 6, and the toner image is fixed on the transfer paper by the fixing device. The toner remaining on the photoreceptor 1 without being transferred is transferred to the cleaning blade 7
-1 and is collected in the developing unit 3 or the waste toner bottle by the discharge screw 7-2. Subsequently, the photoconductor 1 is initialized by the charge removing lamp 8.

FIG. 7 shows a state between the photosensitive member 1 and the developing sleeve.
It is the figure which modeled the state of the ear. In Fig. 7, ear A is longer
Because of the ear, the surface of the developing sleeve to the surface of the photoconductor 1
However, since the ear B is short, it is
A gap is formed between the tip of the ear. Such a gap
Ionization occurs, the latent image is destroyed, and a ring mark is emitted
Live. Fig. 8 shows the occurrence of ring marks and the amount of developer pumped up.
Shows the relationship. OK on the vertical axis has no ring mark
NG indicates that a ring mark has occurred.
The level of ring mark
And the number and size of the ring marks. Figure
7, the developer pumping amount is 70 mg / cm ²Above
Although there is almost no problem in image formation, ring
The occurrence of marks may be seen. Developer pumping amount
Is 85mg / cm²If it is above, the generation of ring mark
can not see. Therefore, taking the margin into account,
90mg / cm²Above
Good. In this way, when the amount of developer pumped up increases,
The occurrence of marking marks is no longer observed.
This is because the ear B as shown in FIG. You
In other words, if the amount of developer pumped up is small,
Long and short spikes are mixed and uneven.
If the amount of developer pumped up is large, sufficient
Due to the presence of a suitable developer, a fairly uniform spike is formed. Long
The ear is longer than the distance between the photoconductor 1 and the developing sleeve.
The tip is broken toward the developing sleeve after contacting the photoconductor 1
Bends or spreads along photoreceptor 1 so the percentage of short ears
If there is little, even if ionization occurs in a short ear,
Blocks are formed and no destruction of the latent image occurs.

The structure of the developing section 3 in the photosensitive unit for obtaining the above-described effects will be further described. FIG. 3 shows a schematic configuration diagram of the developing unit, and FIG. 4 shows a magnetic force distribution around the developing roller. As shown in FIG. 4, the developing roller 3-1-1 is arranged at an angle of θ and a distance of δ with respect to the first stirring member 3-2-2. The magnetic force in the normal direction of the developing roller 3-1-1 is a P4 pole (S pole) that pumps the developer in the developer container from the first developer stirring member 3-2-2 onto the developing roller 3-1-1. P5 pole (N pole), P6 pole (S pole) for transporting the pumped developer to the development area, P1 pole (N pole) for supplying the transported developer onto the photoreceptor 1, and development. The P2 pole (S-pole) that transports the developer remaining on the developing roller 3-1-1 to the developer accommodating unit and not remaining on the developing roller 3-1-1, and the horizontal direction and the normal line P3 that releases the conveyed developer on the developer container with a magnetic force of 10 mT or less in both directions.
Consists of poles.

The developer stirring member 3-2-2 of the present embodiment,
The positional relationship between 3-2-4 and the developing roller 3-1-1 and the magnetic force on the developing roller 3-1-1 will be described. Each condition of the present embodiment is as follows. Photoconductor: OPC drum, diameter 30 mm, rotation speed: 125
mm / sec Developing roller: diameter 16 mm, rotation speed 380 rpm Developer stirring member: screw, diameter 19 mm, rotation speed 42
0 rpm, screw pitch 12 mm Magnetic distribution: as shown in FIG. 5 As described above, polarities are different from each other on both sides of a line connecting the center of the first developer stirring member 3-2-2 and the center of the developing roller 3-1-1. Magnetic poles (P4 pole, P5 pole) are arranged, and a magnetic pole P3 pole is provided on the upstream side of the rotation of the developing roller 3-1-1 with a magnetic force of 10 mT or less in both horizontal and normal directions, A test was conducted on the relationship between the positions of the developing roller 3-1-1 and the first developer stirring member 3-2-2 and the image density. The result is shown in FIG.

As shown in FIG. 6, the developing roller 3-1-1
Is arranged at an angle θ of 40 to 70 degrees and a distance δ of 2 mm to 5 mm with respect to the first developer stirring member 3-2-2, so that the development remaining on the developing roller 3-1-1 after the development is performed. It has been confirmed that the developer is released and resupplied on the developer accommodating portion to improve the circulation efficiency of the developer. When the distance between the developing roller 3-1-1 and the first developer stirring member 3-2-2 is 2
If the distance is less than 5 mm, the distance between the first developer stirring member 3-2-2 and the developing roller 3-1-1 is too short, and an image defect due to uneven supply of the developer by the developer stirring member appears. Sufficient developer was not supplied to the developing roller 3-1-1, and the image density was reduced. Further, the developing roller 3
-1-1 with respect to the first developer stirring member 3-2-2
If it is arranged at an angle smaller than the angle, the developing roller 3-1
-1 is not sufficiently separated on the developer accommodating portion, resulting in a decrease in image density. When the developer is arranged at an angle larger than 70 degrees, the amount of developer pumped to the developing roller is reduced. Also, the image density decreased.

In order to obtain a condition in which a margin is added to the above condition, the magnetic force of the P4 pole and the P5 pole facing the first developer stirring member 3-2-2 was examined and examined. As a result, it was found that the margin was improved by setting the magnetic force of the P4 pole to 30 mT to 60 mT. When the magnetic force of the P4 pole is lower than this range and the distance from the wall of the developer accommodating portion is 2 mm in the above-described embodiment, but is too large as 3 mm or more, the pumping amount of the developer is insufficient, Conversely, P
If the magnetic force of the four poles is higher than the above range, the developer in the P3 pole region is attracted, and the image density is likely to be reduced or pitch unevenness is likely to occur. For the P5 pole, the margin can be improved by setting the magnetic force to 50 mT to 80 mT. When the magnetic force of the P5 pole is lower than this range, the amount of the developer pumped is insufficient as described above. Conversely, when the magnetic force of the P5 pole is 80 mT or more, the stress with the developer regulating member (development doctor) increases. As a result, the charge amount increases, and the image density decreases or pitch unevenness easily occurs.

[0018]

As described above, the two-component developing apparatus of the present invention has the following effects. According to the first aspect of the present invention, when a two-component developer is used and an alternating electric field is applied to perform development, the amount of the developer pumped on the surface of the developer carrier is set to 85 mg / cm ² or more. As a result, generation of ring marks is prevented, and image quality defects do not occur, and high-speed and high-quality development can be performed. According to a second aspect of the present invention, the developer carrier having a plurality of magnetic poles therein is disposed obliquely upward by 40 to 70 degrees with respect to the developer stirring member, and separated from the developer stirring member by 2 to 5 mm. Arranged, a pair of magnetic poles arranged with a line connecting the center of the developer carrying member and the center of the developer stirring member to be composed of magnetic poles having different polarities from each other. The magnetic force of the magnetic pole on the downstream side in the rotation direction should be 50 mT or more in the normal direction,
By setting it to 80 mT or less, generation of a ring mark can be prevented, and high-quality development without image quality defects can be performed at high speed.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a photoconductor unit using a developing device according to an embodiment of the present invention.

FIG. 2 is a schematic diagram illustrating a configuration near a photoconductor of the photoconductor unit illustrated in FIG. 1;

FIG. 3 is a schematic diagram illustrating a configuration of a developing unit of the photoconductor unit illustrated in FIG. 1;

FIG. 4 is a diagram showing a normal direction magnetic force distribution and a horizontal direction magnetic force distribution of a developing roller constituting the developing unit shown in FIG. 3;

FIG. 5 is a diagram showing the magnetic force of each magnetic pole disposed inside the developing roller shown in FIG. 4 and an angle with respect to a normal line.

FIG. 6 is a diagram illustrating an influence of a positional relationship and a distance between a developing roller and a first developer stirring member illustrated in FIG. 4 on image density.

FIG. 7 is a diagram illustrating a state of ears of a developer formed on a developing sleeve.

FIG. 8 is a diagram showing the relationship between the amount of developer pumped onto a developing sleeve and the occurrence of a ring mark.

[Explanation of symbols]

 DESCRIPTION OF REFERENCE NUMERALS 1 photoconductor 2 charging roller 3 developing section 3-1 developer carrying section 3-1-1 developing roller 3-1-2 developing doctor 3-2 developer accommodating section 3-2-1 sealing member 3-2-2 1 Developer stirring member 3-2-3 Toner density sensor 3-2-4 Second developer stirring member 4 Exposure means 5 Photoconductor shutter 6 Separation claw 7-1 Cleaning blade 7-2 Discharge screw 8 Static elimination lamp 9 P sensor 10 Transfer separation unit 11 Toner supply unit 12 Toner hopper unit

Continued on the front page (72) Inventor Hideki Yoshinami 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Company (72) Inventor Mayumi 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Company (72) Inventor Toshitaka Yamaguchi 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Company (72) Inventor Hiroshi Mizusawa 1-3-6 Nakamagome, Ota-ku, Tokyo Ricoh Company (72) Invention Person Kenzo Tatsumi 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (72) Inventor Satoshi 1-3-6 Nakamagome, Ota-ku, Tokyo F-term in Ricoh Co., Ltd. 2H031 AB09 AC19 2H077 AB01 AB18 AD06 AD36 DA52 EA03 FA19

Claims (2)

[Claims] 1. A two-component developer comprising a toner and a carrier, which is disposed at a position facing and close to an image carrier on which an electrostatic latent image is formed on its surface, is rotatably supported, and has an alternating electric field applied thereto. And a developer accommodating section that accommodates a two-component developer, and a developer stirring member that supplies the two-component developer to the developer carrier while stirring the two-component developer.
In a two-component developing device for developing an electrostatic latent image formed on the surface of the image carrier with a two-component developer, the amount of the developer pumped on the surface of the developer carrier is 8
A two-component developing device, wherein the amount is 5 mg / cm ² or more. 2. The developer carrier has a plurality of magnetic poles therein, and is obliquely upward by 40 to 70 degrees with respect to the developer stirring member, and is separated from the developer stirring member by 2 mm to 5 mm. And a pair of magnetic poles disposed across a line connecting the center of the developer carrier and the center of the developer stirring member are magnetic poles having different polarities from each other; 2. The two-component developing device according to claim 1, wherein, of the pair of magnetic poles, a magnetic pole downstream of the developer carrier in the rotation direction has a magnetic force of 50 mT or more and 80 mT or less in a normal direction.