JPS5921555B2 - Magnetic brush development method and its device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic brush developing method and apparatus for use in electrophotography and the like.

One of the developing methods commonly used in electrophotographic copying machines at present is the magnetic brush developing method.

In this developing method, a developer consisting of toner and carrier is placed in a developing container, and the developer is supplied to a developing roll containing a built-in magnet to form a magnetic brush around the developing roll, which is then applied to the photoreceptor. A visible image is obtained by contacting the upper electrostatic latent image. After development, the developer on the developing roll is scraped off into the developing container by a scraping V plate, stirred together with an appropriate amount of toner, and then supplied to the developing roll again. Preferably, a developer concentration detection device is used to control the amount of toner to be replenished to maintain a constant developer concentration. In such a developing method and apparatus, the developer becomes fatigued when used for a long period of time, resulting in a decrease in density, fogging of the developed image, and the like.

The causes are thought to be an increase in spent toner due to pressure bonding to the carrier and an increase in the amount of charge on the carrier. It seems to be highly dependent.

Therefore, an object of the present invention is to provide a developing method which can control excessive stirring of the developer, eliminate the above-mentioned drawbacks caused by this, and which can function satisfactorily as a magnetic brush developing method. An object of the present invention is to provide a developing device.

The purpose of the above is to scrape off the developer on the surface layer of the magnetic brush that actually contributed to the development of the latent image after it has come into contact with the latent image surface, and to remove it from the developer provided separately from the main developer container. This is accomplished by conveying the developer into an auxiliary container and intensively stirring the developer and the newly replenished toner.

Hereinafter, the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a schematic diagram showing an embodiment of the present invention. A developer main container 2 containing a developer 1 consisting of toner and carrier is continuously provided with a smaller developer auxiliary container 3 on the upper left side thereof. A developing roll 4 is provided in the developer main container 2 with its lower part buried in the developer 1. The developing roll 4 is comprised of a rotatable non-magnetic conductive sleeve 7 which incorporates an immovable magnet roll 5 and is connected to a DC bias power source 6 via a rotating shaft (not shown). One end of a first scraping phantom plate 9 is placed above the developing roll 4 on the side opposite to the photosensitive drum 8 at a constant distance from the surface of the developing roll 4 . The constant interval means that, of the magnetic brush formed by the developer adsorbed on the developing roll 4, only the developer on the surface layer that actually contributes to the development of the electrostatic latent image on the photoreceptor 8 is used. It's something that can be scraped off. 1st
The other end of the scraping plate 9 is tilted downward and is located above the developer auxiliary container 3.A stirring device 10 is provided inside the developer auxiliary container 3 and is located above the developer auxiliary container 3. , a toner replenishing device 1 having a supply roll 11 in a lower opening is provided.
2 is provided. On the other hand, below the first scraping plate 9, one end of a second scraping plate 13 is arranged so as to scrape off all or most of the remaining developer on the developing roll 4. is slanted downward. The developer 1 in the developer main container 2 is attracted to the surface of the sleeve 7 by the magnetic attraction force of the magnet roll 5, forming a magnetic brush.

This magnetic brush is conveyed upward as the sleeve 7 rotates in the direction of the arrow, and is regulated to a predetermined thickness by the doctor blade 2a. The thickness of this magnetic brush layer is formed to be thick to some extent in consideration of the strength of contact of the magnetic brush with the surface of the photoreceptor drum 8, etc., and the electrostatic latent image on the surface of the photoreceptor 8 is formed at the developing position. It is only the surface layer that comes into contact and actually contributes to development. Development is performed by electrostatically adsorbing the toner of the carrier and toner that constitute the developer onto the electrostatic latent image. After the development, the surface layer of the magnetic brush is a developer with a reduced density because the toner is adsorbed to the latent image. This developer whose concentration has decreased is scraped off by the first scraping plate 9 and falls into the developer auxiliary container 3. On the other hand, the remaining developer on the sleeve 7 whose concentration has not decreased is scraped off by the second scraping plate 13 and falls into the developer main container 2 . An appropriate amount of new toner is replenished from the toner replenishing device 12 to the developer whose concentration has decreased and has fallen into the developer auxiliary container 3 , and mixed and stirred by the stirring device 10 .

Since the amount of toner consumed during development is generally constant, a constant amount of toner is replenished into the developer auxiliary container by manually or automatically rotating the supply roll 11 as appropriate. be done. Developer auxiliary container 3
The developer and toner inside are stirred and mixed to be newly frictionally charged, flow from the developer auxiliary container 3 into the developer main container 2, and are again developed together with the developer in the developer main container 2. It is attracted to the roll 4 and used for developing the latent image.
Note that the bias voltage is applied to the developing roll 4 because the developing roll is used as a developing electrode, and by applying a voltage slightly higher than the background potential of the latent image, the background potential can be reduced. Prevents toner adhesion,
This is to obtain an image without background stains.

The stirring device 10 shown in FIG. 1 is an impeller having a plurality of blades continuous in the axial direction, and as shown in FIG.
It can also be set to 0a.

In this case, the first scraping board is the spiral roll 10a.
It is preferable to use a centrally integrated scraping plate 9a formed by narrowing the side, widening the developing roll side, and bending both edges upward toward the spiral roll 10a side. This scraping board 9a
The developer that has flown down is collected in the center at its ends, falls from there to the center of the spiral roll 10a, and is agitated by the rotation of the spiral roll 10a in the direction of the arrow, towards both ends. transported. In this case, therefore, more lateral stirring is achieved than in the case of an ordinary impeller. This is sufficiently effective because the developer concentration changes differently in the lateral direction. Also,
In the embodiment shown in FIG. 1, the second scraping plate 13 is
Not necessarily necessary.

The second scraping plate is required when the amount of charge of the developer used is insufficient to some extent due to the characteristics of the developer used. The charging of the developer is obtained by frictionally moving the developer. Therefore, a certain degree of frictional electrification can be obtained by scraping the developer on the developing roll 4 by the second scraping plate 13 and moving it downward until it is adsorbed by the next developing roll. FIG. 3 is a schematic configuration diagram showing another embodiment of the present invention.

At the upper left of the developer main container 22 containing the developer 21,
Similarly, a developer auxiliary container 23 is provided continuously.
A supply roll 26 consisting of a rotatable non-magnetic sleeve 25 containing an immovable magnet roll 24 is provided at the lower part of the developer main container 22.
A developing roll 27 is provided diagonally above and to the left of 6 at a constant interval. Similar to the above example, the developing roll 27 houses an immovable magnet roll 28 (which is magnetically stronger than the above magnet roll 24), and is connected to a bias power supply 29 via a rotating shaft (not shown). It consists of a rotatable non-magnetic conductive sleeve 30. Above the opposite side of the photosensitive drum 31 disposed on the right side of the developing roll 27, one end of a first scraping plate 32 for scraping only the surface layer of the magnetic brush on the developing roll 2r is installed at a predetermined interval. The other end thereof is inclined downward and is located above the developer auxiliary container 23. The first scraping plate 32 is a centrally integrated scraping plate as shown in FIG. In addition, an iron core coil 34 is provided close to the outside of this rectangular tube 33. Inside the developer auxiliary container 23, a spiral roll type stirring device 35 as shown in FIG. 37 are provided. This supply roll 36 is controlled and driven by a control circuit 38 connected to the iron core coil 34. On the other hand, below the first scraping plate 32, one end is attached to the developing roll 2.
7 surface, with the other end facing downward.
A scraping plate 39 is provided. The developer 21 in the developer main container 22 is transferred to the magnet roll 2 of the supply roll 26.
7 is attracted to the surface of the sleeve 25 to form a magnetic brush.

As the sleeve 25 rotates in the direction of the arrow, the magnetic brush is conveyed upward while the height of the brush is adjusted by the doctor blade 22a on the way, and is attracted to the developing roll side at a position facing the upper developing roll 27, and is attached to the photoreceptor drum. Develop the latent image on 31. After the development is completed, the developer on the surface layer of the magnetic brush is scraped off by the first scraping plate 32.
The remaining developer is scraped off by the second scraping V plate 39.

The developer whose concentration has changed and has been scraped off by the first scraping plate 32 passes through the rectangular tube 33 and falls into the developer auxiliary container 23, while the change in concentration is detected by the iron core coil 34. Ru.

This is done by introducing the developer into the magnetic path of the iron core coil and detecting a change in current due to a change in the inductance of the coil. This current change is input to the control circuit 38, and the rotation of the supply roll 36 is controlled according to the change, so that the required amount of toner is appropriately replenished into the developer auxiliary container 23. The toner particles and developer in the developer auxiliary container 23 are stirred and mixed by the stirring device 35 and are frictionally charged, flow into the developer main container 22, and are scraped off by the second scraping plate 39. Together with the unchanged developer, it is again attracted to the supply roll 26 and headed for the development position.

As described above, according to the present invention, first, only the surface layer portion of the magnetic brush where the developer concentration has changed is scraped off, and this is guided into the developer auxiliary container provided separately from the developer main container. The required amount of toner is replenished and stirred, and in the developer main container, the developer remaining on the developing roll after the scraping is removed to the developing section through only a scraping plate and a conveying means such as a developing roll and a supply roll. This prevents the developer from being actively stirred by supplying it to the developer, thereby preventing an increase in spent toner due to excessive agitation of the developer and excessive charging of the developer, preventing developer fatigue and extending the life of the developer. In addition to being able to extend the time period, it is also possible to sufficiently adjust the developer concentration.

In addition, when detecting the developer concentration using a developer concentration detection device, conventionally it was done without distinguishing between the surface layer and the inner layer of the magnetic brush, so if there is no relatively large change in concentration, the concentration Detection was difficult, but according to this invention, concentration is detected by collecting only the developer in the surface layer where concentration changes occur, so it is possible to detect even more minute changes in concentration than before, and the developer concentration can be detected even more minutely than before. Accurate control can be performed.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing one embodiment of the present invention, and FIG.
The figure is a perspective view showing another embodiment of the first scraping V plate and stirring device used in the present invention, and FIG. 3 is a schematic configuration diagram showing another embodiment of the present invention. DESCRIPTION OF SYMBOLS 1...Developer, 2...Developer main container, 3...Developer auxiliary container, 4...Developing roll, 8...Photosensitive drum, 9...First scraping V plate , 10... Stirring device, 1
2... Toner supply device, 13... Second scraping board.

Claims (1)

[Scope of Claims] 1. A developer consisting of at least two components, carrier and toner, contained in a main developer container is adsorbed onto a developing roll to form a magnetic brush, and this magnetic brush is applied to the static surface of a photoreceptor. In the magnetic brush development method, which develops the latent image by bringing it into contact with the latent image, the magnetic brush after contacting the latent image surface,
The developer on the surface layer that actually contributed to the development of the latent image is scraped off and conveyed into an auxiliary developer container, and the necessary amount of toner is replenished and stirred into the developer in the auxiliary developer container. Obtaining a predetermined developer concentration, conveying this to the developer main container, and further supplying the developer remaining on the developing roll after the scraping to the developing section through only the conveying means to perform development. A magnetic brush development method featuring: 2. A developer consisting of at least two components, carrier and toner, contained in a main developer container is adsorbed onto a developing roll to form a magnetic brush, and this magnetic brush is brought into contact with the electrostatic latent image on the surface of the photoreceptor. In a magnetic brush developing device that develops the latent image, the developer on the surface layer of the magnetic brush that has come into contact with the latent image surface, which actually contributed to the development of the latent image, is scraped off and transferred to the developer main container. a scraping member for causing the developer to flow down into the continuously provided auxiliary container;
a toner replenishing device for supplying a required amount of toner to the developer in the developer auxiliary container; The developer is provided with an agitation device for conveying the developer to the developer, and the developer from the agitation device and the developer remaining on the developing roll after the scraping is supplied to the developing section through only the conveyance means to perform development. Features a magnetic brush developing device. 3. A developer consisting of at least two components, carrier and toner, contained in a main developer container is adsorbed onto a developing roll to form a magnetic brush, and this magnetic brush is brought into contact with the electrostatic latent image on the surface of the photoreceptor. In the magnetic brush development method, which develops the latent image using a magnetic brush, the magnetic brush after contacting the latent image surface,
The developer on the surface layer that actually contributed to the development of the latent image is scraped off by a first scraping member and conveyed into the developer auxiliary container, and the developer remaining on the developing roll after the scraping is scraped off by the first scraping member. 2 Scrape the toner with a scraping member and convey it into the main developer container, and replenish the necessary amount of toner to the developer conveyed into the developer auxiliary container and stir it to obtain a predetermined developer concentration. The magnetic brush developing method is characterized in that the obtained developer is transported into a main developer container and supplied to a developing section together with the developer from the second scraping member through only a transport means to perform development. 4. A developer consisting of at least two components, carrier and toner, contained in a main developer container is adsorbed onto a developing roll to form a magnetic brush, and this magnetic brush is brought into contact with the electrostatic latent image on the surface of the photoreceptor. In a magnetic brush developing device that develops the latent image, the developer on the surface layer of the magnetic brush that has come into contact with the latent image surface, which actually contributed to the development of the latent image, is scraped off and transferred to the developer main container. a first scraping member for causing the developer to flow down into the developer auxiliary container provided in succession; and a first scraping member for scraping off the developer remaining on the developing roll after the above-mentioned scraping and causing the developer to flow down into the developer main container. a toner replenishing device for supplying a necessary amount of toner to the developer flowing down into the developer auxiliary container; and a stirring device for transporting the developer and toner into the developer main container while stirring the developer, and the developer from the stirring device and the developer from the second scraping member are used for development only through the transport means. A magnetic brush developing device is characterized in that a magnetic brush is supplied to a portion of the magnetic brush to perform development. 5. The magnetic brush according to claim 1 or 3, wherein the amount of toner supplied into the developer auxiliary container is obtained by measuring the concentration of the developer conveyed into the developer auxiliary container. Development method. 6. Claim No. 6, characterized in that the toner supply device for supplying the required amount of toner to the developer auxiliary container is controlled by means for detecting the concentration of the developer flowing down into the developer auxiliary container. The magnetic brush developing device according to item 2 or 4.