JPH0126059B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a developing device in an electronic copying machine. The developer used in this type of developing device consists of a carrier and a toner. The carrier is mainly made of iron or iron oxide, and the surface is coated with an oxide film or a polymer. Toner is a colored polymer powder. When the carrier and toner are mixed and stirred, they rub against each other and become electrically charged. When amorphous selenium is used for the photosensitive drum, the toner and carrier are selected so that the toner is negatively charged and the carrier is positively charged. Changing the mixture ratio of toner and carrier changes the image. If the toner ratio is low, the image density will decrease and streaks will become noticeable. If the proportion of toner is too high, it may cause background fog or dirt inside the machine. Therefore, it is necessary to keep the mixing ratio of toner and carrier as constant as possible.

Toner is consumed in the developing device, and new toner is repeatedly replenished. When new toner is replenished into the developing device, agitation creates friction and imparts a sufficient charge to the toner. As mentioned above, the toner concentration in the developer is extremely important in obtaining high-quality images, and in order to obtain a large quantity of stable images, it is necessary to maintain the toner concentration constant at all times. It is an object of the present invention to provide a developing device for an electronic copying machine that can meet this demand.

Embodiments of the present invention will be described with reference to the drawings. 1st
The figure shows an electronic copying machine equipped with the developing device of the present invention. In FIG. 1, reference numeral 1 denotes a photosensitive drum made of amorphous selenium, which rotates in the direction of arrow a. 2 is a charger, and when a positive high voltage is applied, the photosensitive drum 1
gives a positive charge to . The image of document 3 is mirror 4,
5, 6, 7, 8, 9, and is imaged onto the photosensitive drum 1 through the lens 10 and the slit 11,
Forms an electrostatic latent image. Reference numeral 12 denotes a developing device, which applies developer onto the photosensitive drum 1 by means of a magnet roll 13 rotating in the direction of arrow b, thereby visualizing the electrostatic latent image. At this time, only the toner adheres to the photosensitive drum 1, and the carrier remains on the magnet roll 13. As development is repeated, the amount of toner in the developer decreases, so new toner is replenished. A scraper 14 is provided so as to be in sliding contact with the magnet roll 13, and scrapes off the developer adhering to the surface of the magnet roll 13. A density sensor 15 is provided behind the scraper 14 to detect the toner density in the developer. The density sensor 15 controls the supply of toner by the toner hopper 16 based on the detected signal to maintain a constant mixing ratio of toner and carrier.

Stirring rods 17 and 18 mix the supplied toner and developer. The toner adhering to the photosensitive drum 1 is transferred onto copy paper by a transfer charger 19. 2
A separating charger 0 separates the copy paper from the photosensitive drum 1. The image on the copy paper separated from the photosensitive drum 1 is fixed by a fixing device 21. The photosensitive drum 1 is neutralized by a static eliminator 22 and cleaned by a cleaner 23 to complete the copying operation.

Next, the developing device of the present invention will be explained with reference to FIGS. 2 and 3. The developing device 12 includes a magnet roll 13 mounted on a shaft between a front side plate 24 and a rear side plate 25.
, two stirring rods 17 and 18, and a scraper 14 provided so as to be in sliding contact with the magnetic roll 13.
and a concentration sensor 15. The magnet roll 13 has a permanent magnet fixed therein by a knob 26, and has a rotating non-magnetic sleeve on the outside. The stirring rods 17 and 18 have driving gears 27 and 28 at their shaft ends. The density sensor 15 is composed of a coil wound around an iron core, and detects changes in magnetic permeability caused by changes in the mixing ratio of toner and carrier in the developer. 29 is a container of the developing device, and 30 is its cover.

The developer is stirred and mixed by stirring rods 17 and 18, and is rubbed onto the photosensitive drum 1 through between the magnet roll 13 and the doctor blade 31. After development, the developer adhering to the magnet roll 13 is scraped off by a scraper 14. When the density sensor 15 detects that the toner density has decreased, the replenishment roller 3 provided in the hopper 16
4 is driven to supply new toner. 32
is a sealing member that prevents toner from leaking from the gap between the hopper 16 and the container 29. 33 is a guide plate.

The stirring rods 17, 18 have spiral stirring blades as shown in FIG. The first stirring rod 17 provided below the hopper 16 and behind the scraper 14 rotates in the direction of arrow c, and transfers the toner replenished from the direction of arrow e by the replenishment roller 34 to one side of the container (f direction). The toner collected on one side of the container is moved to the other side of the container (in the g direction) by a second stirring rod 18 provided below the first stirring rod 17. That is, the second stirring rod 18 rotates in the d direction, which is the opposite direction to the first stirring rod 17. In addition,
When the spiral directions of the stirring blades of the first stirring rod 17 and the second stirring rod 18 are opposite, they rotate in the same direction. Immediately after the toner is replenished from the hopper 16, the toner concentration is highest on one side of the container where the toner is collected by the first stirring rod 17. Concentration sensor 1
Reference number 5 is provided at a location in the container 29 where the toner concentration is highest to facilitate its detection.

As described above, the present invention provides an electronic copying machine that visualizes the electrostatic latent image by applying a developer made of toner and carrier to the surface of the photosensitive drum 1 on which the electrostatic latent image is formed using the magnet roll 13. , a hopper 16 for supplying toner to a container 29 of a developing device that accommodates and rotatably supports the magnet roll 13; and a scraper for scraping off developer remaining on the magnet roll 13. 14, first and second stirring rods 17 and 18 having spiral stirring blades, and a concentration sensor 15 for detecting the concentration of toner in the developer, the first stirring rod 17 is connected to the hopper. The second stirring bar 18 is located behind the scraper 14 below the first stirring bar 16 and stirs and mixes the developer to collect it on one side of the container 29, and the second stirring bar 18 is located below the first stirring bar 17. The developer collected on one side of the container 29 is stirred and mixed so as to move to the other side of the container 29. The developer is disposed on one side of the container 29, and is configured to detect the toner concentration in the developer.

Since the developing device of the present invention has the above configuration, the developer in the container and the replenished toner are collected on one side of the container and mixed and stirred by the first stirring rod 17, and the developer is mixed and stirred at the most effective position. By detecting the toner concentration in the developer and controlling the amount of toner to be replenished, the toner concentration in the developer can be maintained substantially uniform. As a result of experiments, we were able to control the toner concentration in the developer to an ideal range of 3.5% to 4.3%.
After continuously copying 30,000 sheets, it was confirmed that there was almost no difference in image quality between the initial copy and the final copy.

[Brief explanation of drawings]

Fig. 1: Side view of an electronic copying machine equipped with the developing device of the present invention, Fig. 2: Side view of an embodiment of the developing device of the present invention, Fig. 3: Plan view of an embodiment of the developing device of the present invention. . [Symbols] 1...Photosensitive drum, 2...Charger, 3...
Original, 4, 5, 6, 7, 8, 9...Mirror, 10...
Lens, 11...Slit, 12...Developer, 13...
Magnet roll, 14... Scraper, 15... Concentration sensor, 16... Toner hopper, 17... First stirring bar, 18... Second stirring bar, 19... Transfer charger, 2
0...Separation charger, 21...Fixer, 22...Static eliminator, 23...Cleaner, 24...Front side plate, 25...Rear side plate, 26...Knob, 27, 28...Gear, 29...Container, 30...Cover, 31 ...Doctor Blade, 3
2... Seal member, 33... Guide plate, 34... Supply roller.

Claims (1)

[Scope of Claims] 1. An electronic copying machine that visualizes the electrostatic latent image by applying a developer consisting of toner and carrier to the surface of the photosensitive drum on which the electrostatic latent image is formed using a magnetic roll, A container of a developing device that accommodates the roll and rotatably supports the roll is provided with a hopper for supplying toner into the container, a scraper for scraping off developer remaining on the magnetic roll, and a spiral stirring blade. and a concentration sensor for detecting the concentration of toner in the developer, the first stirring rod is located behind the scraper below the hopper, and The second stirring rod is located below the first stirring rod and moves the developer collected on one side of the container to the other side. the toner is stirred and mixed in a moving manner, and the concentration sensor is disposed on one side of the container in which the developer is collected by the first stirring bar and is configured to detect the toner concentration in the developer. A developing device for an electronic copying machine featuring the following. 2. The density sensor is composed of a coil wound around an iron core, detects changes in magnetic permeability based on changes in toner concentration in the developer, and controls toner supply based on the output thereof. A developing device for an electronic copying machine according to claim 1.