JPH0582944B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is a two-component development method using a dry two-component developer, in particular, a compact and lightweight method in which developer replenishment and conveyance to a developing sleeve and mixing and agitation can be carried out independently. - Provides an inexpensive developing device.

[Prior art]

In the conventional system for conveying and supplying developer in the axial direction of the developing sleeve, a scraper scrapes off the developer that once contributed to development, regenerates it into developer with an appropriate toner concentration, and supplies it again to the sleeve from the upper screw. If the amount of upper and lower developer conveyed is less than the amount of developer applied to the sleeve, the amount of developer scraped off by the scraper will increase, and the developer applied to the sleeve will not be collected in the developing device and will overflow outside. The biggest drawback occurred (see Figure 2). Also, JP-A-51-
The development method shown in 15443 does not have a scraper;
Since only one screw is used to supply new developer and transport used developer, the developer that once contributed to development is used for development many times, resulting in dark density and density unevenness on the image. That was the result.

〔the purpose〕

The present invention eliminates the drawbacks of the above-mentioned conventional examples, and has a small, lightweight, and simple structure that allows the developer to be supplied to the developing sleeve.
It is possible to carry out stripping and transport and stirring and mixing of the developer independently, and the developer that always maintains an appropriate toner concentration contributes to the development, eliminating the problems of density thinning and density unevenness, and further improving the image quality due to durability. The purpose of the present invention is to provide a developing device that has a great effect on stability.

According to the present invention, by making the amount of developer conveyed by the upper and lower screws larger than the amount of developer applied to the sleeve, it has become possible to eliminate the developer overflow phenomenon, which was the biggest problem.

(Summary of the Invention) The present invention achieves the above object, and includes upper and lower developer transport means that have a stirring/mixing region longer than the length of the developer carrier and move and circulate the developer in the axial direction of the developer carrier. , the amount of developer applied to the carrier per unit time is the same as or less than the amount of upper and lower developer conveyed per unit time, and the scraper end opposite to the carrier is axially This developing device is characterized in that an opening for passing the developer is provided across the developer, and the developer is caused to fall from the upper developer transport means side to the lower developer transport means.

〔Example〕

FIG. 1 shows an embodiment of the present invention. 1 is an image carrier, 2 is a developer carrier, and 3 is a developing sleeve which rotates in the forward direction of the image carrier. A magnet placed in the sleeve transports the developer to the image carrier, and a developing pole drives the magnetic brush. The electrostatic latent image is formed and developed in accordance with the electrostatic latent image.

As can be seen from the sectional view of FIG. 1, the portion facing the developing sleeve is provided with no means for supplying and conveying the developer to the sleeve using only the upper and lower screws and for stirring and mixing.

Separately, the upper and lower screws are longer than the sleeve length, and the carrier and toner are stirred and mixed in a region C that extends longer than the sleeve.

We have achieved independent functions in a compact and lightweight manner, which will be explained in detail below.

The developer, which has once contributed to development and whose toner concentration has decreased, is conveyed by the lower screw 4 into a tube having a curvature in area C, and is conveyed to the upper screw portion. At this time, an appropriate amount of toner is also supplied from the toner hopper 11 through the toner replenishment port 13 by a toner concentration detector (not shown) and the toner stirring rod 12, and both are sufficiently stirred and mixed by the screw in the area C carried in the tube. The developer that has reached a specified toner concentration is transferred to the upper screw and conveyed to the upper part of the developing sleeve. At this time, the upper screw is transported by the partition wall 5 from the front to the back of the sleeve with a certain amount of developer stored therein. The partition wall 5 has an opening as shown in the figure, and more than a certain amount of developer is supplied to the sleeve from the opening 5'. At this time, the upper screw is separated from the sleeve by the partition wall 5, and does not interfere with the movement of the developer held in the sleeve. The developer supplied from the upper screw is conveyed and mixed by the scraper 6, carrier return 8, and further by the conveyance pole and cut pole of the magnet, and is sufficiently charged. Then, regulated by a doctor blade 7, only an appropriate amount of developer is conveyed to the development pole side, where a magnetic brush is formed and development is performed.

In the figure, 100 has the shape shown in the figure, and instead of supplying insufficiently charged toner directly between the sleeve and the upper screw, the replenishing developer is reliably supplied to the lower screw to ensure sufficient supply. It gives a strong charge.

The developer that has contributed to the development is again conveyed into the developing device as the sleeve rotates, is scraped off by the scraper 6, and is again conveyed to the area C by the lower screw 4 located away from the sleeve. It turns out.

At this time, the amount of developer conveyed per unit time by the upper and lower screws 4, 4' is made equal to or larger than the amount applied to the sleeve per unit time. As a result, the developer scraped by the scraper 6 stays on the lower screw side and is transported by the lower screw without filling up, and the developer with a constant toner concentration is supplied from the upper screw to the sleeve. As a result, the problem that the developer collected from the sleeve side to the lower screw side cannot fully enter the developing device and overflows is solved. However, if this is done alone, the amount of developer on the upper screw side increases and the upper screw side becomes full, resulting in significant deterioration of image quality or damage to the developing device.

Therefore, in the present invention, an opening toward the lower screw is provided at the end of the scraper that does not face the sleeve, so that excess developer can be moved toward the lower screw.

As described above, it has become possible to maintain a system in which the developer circulates in one direction in a closed circuit, and to maintain an equilibrium state in which the developer does not accumulate too much on either the upper screw side or the lower screw side. As shown in Figure 1, the developer is sufficiently agitated without taking up a large space behind the developing sleeve, and the developer that always maintains a constant toner concentration is uniformly supplied in the axial direction of the sleeve, completely eliminating density distortion and density unevenness. This makes it possible to maintain the initial image quality even during durability.

(Effects of the Invention) As described above, according to the present invention, the developer can be sufficiently charged, a good image can be obtained even with a small device, and a good quality image can be obtained over the entire image.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of an embodiment of the present invention, 1
2 is an image carrier, 2 is a developer carrier, 3 is a developing sleeve, and FIG. 2 is an explanatory diagram showing a conventional example in which developer is conveyed in the axial direction of the sleeve. (Magnetic roller fixed) 4 is the lower screw, 4' is the upper screw.
is lifted outside the developing area and crosses with 4' to transfer the developer. 5 is a partition wall on the upper screw side, and 5' is its opening. 6 is a scraper, 7 is a doctor blade, 8 is a carrier return, 9 is a toner scattering prevention plate, 10 is a developer, 11
is a toner hopper, 12 is a stirring rod for toner replenishment,
13 is a toner supply port. Also shown is a cross-sectional view through AB and the openings at 5 and 5'. 1 is an image carrier, 2 is a developer carrier, 3 is a developer sleeve (magnet roll fixed), 4 is a doctor blade, 5 is a scraper, 6 is an upper screw, 7 is a lower screw, 8 is a developer, 9 is a toner The concentration detector 10 is a stirring blade.

Claims (1)

[Scope of Claims] 1. A top and bottom developer conveying means having a stirring/mixing area longer than the length of the developer carrier and moving and circulating the developer in the axial direction of the developer carrier, The amount of developer applied is the same as or less than the amount of upper and lower developer conveyed per unit time, and an opening for passing the developer is provided in the axial direction on the opposite side of the carrier at the end of the scraper facing the carrier. A developing device characterized in that a developer is dropped from an upper developer transporting means side to a lower developer transporting means.