JPH0643740A - Developing device - Google Patents

Abstract

PURPOSE:To prevent a developing sleeve from being flawed even when a foreign matter intrudes into a developing device by allowing a developer thin layer forming member to abut on the developing sleeve by the magnetic force of the developing sleeve. CONSTITUTION:The developer thin layer forming member (columnar bar) 28 for forming the thin layer of developer on the peripheral surface of the developing sleeve 26 is installed in the developing device 6. A pin 29 is planted at one spot in a central part in the longituinal direction of the columnar bar 28 and fitted in a hole 20c formed at the lower jaw part 20a of a developing device main body 20 so as to attain detent. The bar 28 is allowed to abut on the sleeve 26 by the magnetic force of the sleeve 26, and even when the forign matter is interposed between the respective peripheral surfaces of the sleeve 26 and the bar 28, the bar 28 is separated and its pressurizing force becomes weak, so that the developing sleeve is not flawed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to prevention of scratches on the surface of a developing sleeve provided in a developing device of an image forming apparatus such as a copying machine or a printer, and measures against white spots on images.

[0002]

2. Description of the Related Art Generally, an electrophotographic image forming apparatus such as a copying machine or an image scanner includes a platen on which a document is placed, a document irradiation lamp reciprocating below the platen, a reflection mirror, a fixed projection lens and a reflection mirror. A scanning optical system, a photosensitive drum that is charged with a predetermined potential by a band electrode and rotates, and toner is applied to the electrostatic latent image formed on the surface of the photosensitive drum by the scanning optical system. A developing device for developing the image, a transfer pole for transferring a toner image onto a recording paper surface which is a transfer material conveyed below the surface of the photosensitive drum, a separating electrode and a removing electrode, and the recording paper surface. The fixing device fixes the toner image transferred onto the surface of the photosensitive member, and the cleaning device removes the toner and paper dust remaining on the surface of the photosensitive member after the transfer.

Then, desired toner images are successively recorded on the surface of the recording paper which is intermittently conveyed along a predetermined conveying path.

FIG. 3 shows a cross section of the main part of the developing device 6.
Is a main body of the developing device that forms the housing of the developing device 6, 22 is a first stirring member, 23 is a second stirring member, 24 is a supply roller, 26 is a developing sleeve, and 28 is developing applied to the peripheral surface of the developing sleeve 26. A cylindrical rod which is a developer thin layer forming member having rigidity to regulate the amount of the developer, 28a is a spring plate for regulating the amount of the developer conveyed, and the cylindrical rod 28 has the developer on the developing sleeve 26. It is pressed with a constant load in a state where it is not. 27 is a scraper that cuts off the ears of the developer, 25 is a stirring partition plate,
Reference numeral 21 is an upper lid integrally attached to the upper surface of the developing device main body.

The toner replenished in the developing device 6 is sufficiently agitated and mixed with the carrier by the second stirring member 23 rotating in the direction of the arrow and the first stirring member 22 rotating so as to overlap each other in the opposite direction. The upper developer D is sent to the developing sleeve 26 via the supply roller 24.

The first stirring member 22 and the second stirring member 23 are screw-shaped members having a spiral angle of left-handed rotation in the opposite arrow directions, and are conveyed to the inner side by the thrust of the first stirring member 22. The toner and the carrier successively pass over the stirring partition plate 25 whose upper edge is slanted downward in the direction toward the back of the drawing, and the second
It moves to the side of the stirring member 23 and is conveyed to the front side of the drawing by its thrust, and becomes a homogeneous developer D that is triboelectrically charged by the mixing action of the toner and the carrier during that time, and is a sponge-like supply roller that rotates in the arrow direction The toner is adhered in a layered manner on the peripheral surface of the developing sleeve 26 which rotates clockwise by the arrow 24.

Then, the toner conveyed by the developing sleeve 26 is applied to the electrostatic latent image formed on the peripheral surface of the adjacent photosensitive drum 3 with a predetermined gap from the surface of the developing sleeve 26 to form a toner image. Is developed. The rotations of the first and second stirring members 22, 23, the supply roller 24, and the developing sleeve 26 are transmitted to each other by a drive transmission mechanism mounted on the side surface of the developing device main body 20.

[0008]

As described above, when the cylindrical rod 28, which is the developer thin layer forming member, is brought into contact with the developing sleeve 26 by the spring plate 28a, the elastic force of the spring plate 28a is resisted, for example. If a gap is provided between the developing sleeve 26 and the developing sleeve 26, the spring pressure inevitably increases and the pressing force on the cylindrical rod 28 increases. Since the conventional cylindrical rod 28 rotates with the rotation of the developing sleeve 26, a relatively strong pressing force is applied to the developing sleeve 26 to form a thin layer of the developer of about 50 μm on the developing sleeve 26.
It is in contact with the peripheral surface of 26. And the stirred developer D
Sometimes foreign matter such as cutting chips gets mixed in the developing sleeve 26
And the cylindrical rod 28, the cylindrical rod 28 separates against the elasticity of the spring plate 28a while the foreign matter passes, and the foreign matter is strongly pressed against the peripheral surface of the developing sleeve 26. As a result, a ring-shaped scratch is generated on the peripheral surface of the developing sleeve 26.
When the developing sleeve 26 is scratched, a white stripe corresponding to the scratch is generated on the developed toner image on the photosensitive drum 3 and the image quality is significantly deteriorated. SUMMARY OF THE INVENTION It is an object of the present invention to solve the above problems and to provide a developing device in which a developing sleeve is not scratched even if foreign matter is mixed into the developing device.

[0009]

[Means for Solving the Problems]
It is achieved by any means.

(A) In a developing device of an image forming apparatus for applying toner to an electrostatic latent image formed on an image bearing member to develop the electrostatic latent image, the developing device is provided with a developing sleeve for applying toner to the image bearing member. A developer thin layer forming member that contacts and forms a thin layer of developer on the surface of the developing sleeve, and a developer thin layer forming member that slidably contacts and separates from the developing sleeve is contacted by the magnetic force of the developing sleeve. A developing device characterized by being brought into contact with each other.

(B) The developing device as described in item (a), wherein the developer thin layer forming member attached to the developing device main body is provided with a rotation preventing member for preventing its rotation.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention is a side sectional view of a developing device showing a mounting state of a developer thin layer forming member (cylindrical rod), and a side sectional view showing the constitution of the image forming apparatus of FIG. 2 and FIG. A side cross-sectional view showing the main configuration of a conventional developing device will be described. However, the present invention is not limited to this embodiment. Each member of the developing device having the same function as the conventional one is represented by the same symbol.

Since the function and operation of the developing device 6 are exactly the same as those of the conventional device, the description thereof will be omitted and only the differences between the present invention and this invention will be described.

As shown in FIG. 3, an electrophotographic image forming apparatus 18 is provided.
A platen glass P for placing a document M is provided on the upper surface of the main body 1, and a scanning optical device 2 is provided below the platen glass P in the main body 1. The scanning optical device 2 includes a reciprocating document irradiation lamp 2a, a first mirror 2b, second and third mirrors 2c forming a V shape, a fixed lens 2d and a fourth mirror 2e. A photoconductor drum 3 is rotatably provided in the center of the main body 1 in the direction of the arrow, and a belt electrode 4 for uniformly charging the photoconductor 3a along the rotation direction is provided around the photoconductor drum 3, and a toner replenishing device. 5, a developing device 6 which is replenished with toner and has a developing sleeve 26 built therein, a transfer electrode 7, a separation electrode 8, a charge eliminating electrode 9 and a cleaning device 10 are sequentially arranged. Paper cassette 11,1
Two types of recording papers of different sizes are housed in 1'and set in the main body 1. 12 is a paper cassette 11
Is a first paper feed roller that feeds the recording paper stored in to a standby position in front of the second paper feed roller 13, and is a roller 12a that is rotated via a belt to prevent double feeding of the recording paper.
12a and a stop roller (also referred to as a separating roller) 12b. 13 is an appropriate timing so that the recording paper fed by the first paper feed roller 12 is temporarily stopped at the standby position, and then the leading edge of the visible image on the photoconductor 3a and the leading edge of the recording paper are aligned at the transfer position. The second paper feed roller 14 that feeds paper toward the transfer position again, and 14 is a guide plate for guiding the recording paper fed by the first paper feed roller 12 to the position of the second paper feed roller 13, It is opened and closed by operating a lever (not shown) so that the jammed paper can be taken out by inserting a hand. Reference numeral 15 is a conveying device that conveys the recording paper after transfer to a fixing position, and the fixing device 16 is a heating roller.
16a and pressure roller 16b. Reference numeral 17 denotes a paper discharge roller that discharges the recording paper after fixing to the outside of the main body.

When the copy button is operated in the above apparatus, the original M on the platen glass P is exposed and scanned by the scanning optical device 2, and an electrostatic latent image of the original M is formed on the photoconductor 3a of the photoconductor drum 3. It This electrostatic latent image is developed by the developing device 6.
Is converted into a visible image by the transfer electrode 7 and transferred to the recording paper fed from one of the paper feed cassettes 11 and 11 'of the main body 1. After the transfer, the recording sheet is separated from the photoconductor 3a by the separation electrode 8 and is fixed by the transport device 15.
The sheet is conveyed to 16, is fixed there, and is ejected by the ejection roller 17. In this way, desired toner images are successively recorded on the recording paper surface.

The preventive measures against scratches on the developing sleeve of the present invention are configured as follows.

As shown in FIG. 1 and the enlarged view, a pin 29 which is a rotation preventing member for preventing the rotation of the columnar rod 28 is planted at one central portion in the longitudinal direction (the direction perpendicular to the paper surface) of the columnar rod 28. A hole 20c into which the pin 29 is slidably fitted is provided at one position in the longitudinal direction of the mounting surface 20b of the lower jaw portion 20a of the developing device main body 20 to which the conventional spring plate 28a is mounted. Then, the cylindrical rod 28 in which the pin 29 is planted is fitted into the hole 20c, and the slide surface 20d.
Position and attach to. Therefore, the rotation of the cylindrical rod 28 is restricted, and the pin 29 is used to open the hole 20c and the slide surface 20.
It slides diagonally to the upper left as indicated by the arrow along d and contacts the peripheral surface of the developing sleeve 26. Therefore, the rotation of the cylindrical rod 28 is restricted by the pin 29, and the conventional spring plate 28a is eliminated.

The number of holes 20c and pins 29 is not limited to one, but depending on the structure, the number and positions of the holes 20c and the pins 29 may be arbitrarily set, for example, two.

The cylindrical rod 28 is brought into contact with the peripheral surface of the developing sleeve 26 by the magnetic force of the developing sleeve 26. Therefore, since the rotation of the columnar bar 28 is restricted, a predetermined thin layer of the developer is formed even if the cylindrical bar 28 is brought into contact with a weaker pressing force than in the conventional case. Then, the cylindrical rod 28 is positioned on the slide surface 20d of the lower jaw 20a of the developing device main body 20 and the pin 29 is inserted into the hole 20c to be attached, and then the developing sleeve 26 is attached to a predetermined position of the developing device main body 20 to form a cylindrical shape The rod 28 slides diagonally to the upper left in the direction of the arrow via the pin 29 due to the magnetic force of the developing sleeve and contacts the peripheral surface of the developing sleeve 26 with a predetermined pressing force.

Then, the cylindrical rod 28 which is abutted by the magnetic force
Contrary to the conventional art, the pressing force of the cylindrical rod 28 becomes weaker as the distance from the developing sleeve 26 becomes larger and the gap becomes larger.

In this way, the developing sleeve 26 is attached to the cylindrical rod 28.
Therefore, even if the foreign substance F is sandwiched as described above, the cylindrical rod 28 is separated in the arrow direction and the pressing force is weakened as shown by the chain line, and the peripheral surface of the developing sleeve 26 is damaged. The foreign matter F that is caught without any trouble passes between the developing sleeve 26 and the cylindrical rod 28 without any trouble.

The present invention is not limited to a mono-black image forming apparatus, but is of course applicable to a color image forming apparatus.

[0023]

Since the developer thin layer forming member (cylindrical rod) according to the present invention is brought into contact with the developing sleeve by the magnetic force of the developing sleeve, a foreign substance is temporarily sandwiched between the developing sleeve and the cylindrical rod. Also, the cylindrical rod separates without damaging the peripheral surface of the developing sleeve, and the foreign matter passes together with the developer without any trouble.

Therefore, in the toner image formed on the peripheral surface of the photoconductor drum, the occurrence of white stripes which deteriorate the image was prevented.

[Brief description of drawings]

FIG. 1 is a side sectional view of a developing device showing a mounted state of a developer thin layer forming member (cylindrical rod) according to an embodiment of the present invention.

FIG. 2 is a side sectional view showing the configuration of the image forming apparatus.

FIG. 3 is a side sectional view showing a main configuration of a conventional developing device.

[Explanation of symbols]

 3 Photoreceptor Drum 6 Developing Device 18 Image Forming Device 20 Developing Device Main Body 20a Lower Jaw 20c Hole 28 Developer Thin Layer Forming Member (Cylindrical Rod) 29 Pins

Claims (2)

[Claims] 1. A developing device of an image forming apparatus for applying toner to an electrostatic latent image formed on an image carrier to develop the electrostatic latent image, the developing device being in contact with a developing sleeve for applying toner to the image carrier. And a developing agent thin layer forming member for forming a developing agent thin layer on the developing sleeve surface, and the developing agent thin layer forming member that slidably contacts the developing sleeve is brought into contact with the developing sleeve by magnetic force. A developing device characterized in that 2. The developing device according to claim 1, wherein the developer thin layer forming member attached to the developing device main body is provided with a rotation preventing member for preventing the rotation thereof.