JPS6258507B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a developing device for an electronic copying machine that uses toner as a developer.

A developing device for a dry type electronic copying machine that is currently in practical use uses a magnetic brush.
This uses a magnetic two-component or magnetic one-component method in which a magnetic brush is brought into sliding contact with a photoreceptor, which is an image carrier, and supplies toner or magnetic toner to an electrostatic latent image formed on the surface of the photoreceptor. ing.

However, the magnetic rollers that form the magnetic brush are expensive and require a high degree of mechanical precision, and in the magnetic two-component method, the carrier itself has a limited lifespan, making it difficult to maintain a constant mixing ratio of the carrier and toner. There are drawbacks such as being difficult and requiring a lot of time and effort to maintain the stability of the machine.

Recently, developing devices using fur brush rollers have been proposed, but these do not take into account how to keep the amount of toner held by the fur brush constant regardless of the amount of toner consumed. The density of the toner is not stable, and when there is an excess of toner, uncharged toner that does not participate in the frictional charging with the fur causes a noticeable background fog in the image.

This invention has been made in view of the above circumstances, and its purpose is to stably and appropriately supply toner to a rotating body having hairs, and further promote charging of the toner, thereby improving the ability to perform continuous copying. Another object of the present invention is to provide a developing device that can obtain copied images with stable image density.

The present invention will be explained below based on an embodiment shown in the drawings. In FIG. 1, reference numeral 1 denotes an image carrier, such as a photoreceptor, of a dry type electronic copying machine, which is designed to rotate in the direction of the arrow. Adjacent to this photoconductor 1 is a developing roller 2 which is a rotating body to be described later.
and a toner supply device 4 that supplies, for example, non-magnetic toner 3 to the development roller 2.
is provided. The developing roller 2 is formed by providing a urethane layer 7 on the outer circumferential surface of a mandrel 6, and planting bristles 9 on the outer circumferential surface of the urethane layer 7 via a conductive adhesive layer 8. is adapted to come into sliding contact with the surface of the photoreceptor 1. Furthermore, the hair body 9 has a specific resistance of 10 ⁶ to 10 ¹⁴ Ω. cm, length
It is made of rayon fibers with a diameter of 1.5 mm and a thickness of 1.5 denier, and has a surface density of 20,000 fibers/cm ² .
electrically connected to. Further, the toner supply device 4 accommodates the non-magnetic toner 3 and is provided with a toner supply port 10 at a lower portion facing a part of the outer peripheral surface of the development roller 2. Further, a conductive case 11 having a radius of curvature approximately equal to the radius of curvature of the lower outer circumferential surface of the developing roller 2 is provided, and the conductive case 11 is in light contact with the bristles 9 of the developing roller 2 on the inner circumferential surface thereof. There is. A DC power supply 12 is connected to the toner supply device 4 which is electrically connected to the conductive case 11 for applying a positive or negative DC voltage thereto. Furthermore, stirring blades 13 for stirring the non-magnetic toner 3 are provided inside the toner supply device 4 . Further, a net 14 is stretched over the toner supply port 10, and the non-magnetic toner 3 is supplied to the developing roller 2 through the net 14. That is,
This net body 14 is made of nylon (trade name), has a square mesh of 1.5 mm on each side, and has a wire thickness of 0.2 mm. Note that 15 is a DC power source for applying a negative DC voltage to the mandrel 6 of the developing roller 2.

Next, the operation of the above embodiment will be explained.
When the electrostatic latent image formed on the surface of the photoreceptor 1 faces the developing device 5 as the photoreceptor 1 rotates, a non-magnetic toner 3 is applied to the surface of the photoreceptor 1 by the developing roller 2 rotating in the direction of the arrow. is supplied, and the electrostatic latent image is developed. That is, the non-magnetic toner 3 in the toner supply device 4 is agitated by the stirring blade 13 and is supplied to the developing roller 2 from the toner supply port 10. Therefore, excessive supply of non-magnetic toner 3 is suppressed. Furthermore, the bristles 9 of the developing roller 2 rub against the net 14 as the developing roller 2 rotates, so the bristles 9 are inserted into the mesh of the net 14 . Therefore, the non-magnetic toner 3 on the net 14 is scraped off by the bristles 9, and the non-magnetic toner 3 excessively attached to the bristles 9 is conversely scraped off by the net 14. . For this reason, an appropriate amount of non-magnetic toner 3 is always supplied to the bristles 9 of the developing roller 2, and furthermore, the bristles 9 slide against the inner peripheral surface of the conductive case 11 and then rub against the photoreceptor 1. . Therefore, the non-magnetic toner 3 is supplied from the developing roller 2 to the surface of the photoreceptor 1, and the electrostatic latent image formed on the surface of the photoreceptor 1 is developed. Furthermore, by applying a DC voltage to the conductive case 11, charges are injected into the uncharged toner of the non-magnetic toner 3, thereby preventing background fog from occurring on the uncharged portion of the photoreceptor 1. . For example, when a DC voltage of -200V is applied as a developing bias to the mandrel 6 of the developing roller 2, the toner is charged due to the potential difference between the conductive case 11 and the mandrel 6 of the developing roller 2, as shown in FIG. The amount changes. In this case, the conductive case 11 -
When a voltage of 100 V was applied, the amount of uncharged toner was the least, and the background fogging of the uncharged portion on the photoreceptor 1 was also least. Further, by changing the case bias of the conductive case 11, the amount of toner adhering to the developing roller 2 can be controlled. For example, as shown in FIG. 3, as the absolute value of the case bias increases, the amount of toner adhesion decreases. Therefore,
By controlling the case bias, the developing roller 2 rotates and it is possible to ensure that an appropriate amount of toner always adheres to the developing roller 2 when it leaves the conductive case 11. The disadvantage of this method is that excess toner that does not participate in frictional charging with the bristles 9 causes background fog on the non-electrified area of the photoreceptor 1, but this method makes it possible to remove the excess toner. A duplicate image can be obtained.

As described above, the present invention provides a conductive case that comes into contact with a part of the outer circumference of a rotary body having a hair body, and the rotary body is connected to a toner supply device, a conductive case, and the surface of an image carrier. Since they rotate in order to face each other, toner can be stably and appropriately supplied from the toner supply device to the rotating body, and a copied image with stable image density can be obtained even during continuous copying.

Furthermore, it is possible to reduce the amount of uncharged toner, and it also has the effect of preventing background fog in copied images, which is the biggest drawback of the fur brush development method.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view of a developing device showing an embodiment of the present invention, FIG. 2 is a graph showing the amount of toner charge that changes depending on the potential difference between the conductive case and the developing roller, and FIG. 7 is a graph showing the amount of toner adhesion that increases or decreases depending on a change in case bias of the case. DESCRIPTION OF SYMBOLS 1... Photoreceptor (image carrier), 2... Developing roller (rotating body), 4... Toner supply device, 9... Hair body,
11... Conductive case.

Claims (1)

[Claims] 1 A toner supply device and a toner supplied from a toner supply port of this toner supply device, which is charged and adsorbed, conveyed, and supplied to the surface of an adjacent image carrier, thereby developing an electrostatic latent image on the surface of the image carrier. The rotating body has a structure in which a number of bristles protrude from the outer peripheral surface of the rotating body in a state of being electrically connected to the mandrel of the rotating body, and the toner supplying device has a toner supplying device. A net body on which the bristles of the rotary body rub against each other is provided at the mouth with approximately the same radius of curvature as the rotary body, and a circle is formed from the toner supply port in the rotational direction of the rotary body with approximately the same radius of curvature as the rotary body. 1. A developing device comprising a conductive case extending in an arc shape and having an inner peripheral surface in sliding contact with the bristles and to which a DC voltage is applied.