JPH032778A - Image forming device - Google Patents

Abstract

PURPOSE:To prevent toner leakage and blow-off by forming the developer carrying downstream edge part of an opening which exposes the developer carrier peripheral surface of a developing device casing into a specific shape. CONSTITUTION:The developer carrying downstream edge part 9 of the opening which exposes the peripheral surface of the developer carrier 2 of the developing device casing is formed so that its leading edge closely extended to an image carrier 1 is closely bent to the surface of the developer carrier 2 and distance between the leading edge and the surface of the developer carrier 2 is set below 1.7mm and above the maximum thickness of a developer layer passing the position. Thus, an excessive developer which passes a developing area E is stably returned to a developer retaining part and toner leakage and toner back flow and blow-off from the developer dropping part are prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of industrial application] The present invention relates to an image forming apparatus such as an electrophotographic copying machine, and more particularly, to a developing device that visualizes an electrostatic latent image formed on an image carrier. The present invention relates to an image forming apparatus that has been improved.

[Conventional technology]

2. Description of the Related Art Magnetic brush developing devices are often used as developing devices that use a one-component developer made of toner containing a magnetic substance or a two-component developer made of a mixture of toner and a magnetic carrier.

Figure 2 is a sectional view of a main part of an image forming apparatus showing an example of a conventional magnetic brush developing device. In the figure, l is an image carrier that rotates in the direction of the arrow, and is made of, for example, ZnO.

It has a photosensitive layer of Se, OPC, etc. on the surface. Reference numeral 2 denotes a developing sleeve as a developer carrying member made of a non-magnetic cylindrical body, which rotates in the direction of the arrow and conveys the developer De to the developing area E where the developing sleeve 2 is close to the image carrying member l. . 3
has multiple magnetic poles radially arranged in N.

S are arranged so that they are adjacent to each other in the circumferential direction; Reference numeral 4 denotes a spike regulating member provided on the upstream side of the development area E, which regulates the thickness of the developer layer so that the electrostatic latent image is developed under the best condition. A bias power supply 5 applies a bias voltage to the developing sleeve 2, and applies a DC bias voltage having a polarity opposite to that of toner charging, for example, to prevent toner scattering and development fog. 5a is a protective resistor.

In this magnetic plan developing device, development is performed by fixing the magnet body 3 and rotating the developing sleeve 2, and the magnet body 3 in which N and S magnetic poles are evenly arranged is also opposite to the arrow direction of the developer conveyance direction. There is a method in which development is performed by rotating the image in the direction of . In addition, there is also a developing device in which the developing sleeve 2 is fixed and the magnet body 3 is rotated. However, the magnetic flux density and magnetic field distribution of the magnetic pole required for developer transport are generally different from the magnetic flux density and magnetic field distribution of the magnetic pole required for good development in the development area, and the rotating magnet type Since there are disadvantages such as a complicated drive mechanism compared to a fixed type, a magnet fixing method in which magnets with different magnetic forces are disposed is advantageous.

Regarding the direction of rotation of the developing sleeve 2, that is, the direction in which the developer is conveyed, there is a method in which development is carried out in which the direction of movement of the image carrier surface in the development area E and the direction in which the developer is carried are the same (forward direction), and a method in which development is carried out in the opposite direction. There is a method in which development is carried out using Among these, when developing in the opposite direction, the density tends to decrease at the leading edge of the image (especially the leading edge of a solid black part), and it is difficult to transport the developer stably in the development area E (the developer may not stagnate). Because it is easy to use), forward development is often performed.

In any of the above methods, the developer layer regulated by the spike control member 4 forms a developer flow and is conveyed over the developing sleeve 2, and the electrostatic potential of the image carrier L is Developing the image into a toner image. The developer flow that has passed through the developing area E is conveyed to the developer reservoir while adhering to the developing sleeve 2, but the remaining surplus developer after this development is returned to the developing area while remaining attached to the developing sleeve 2. A scraper 6 is provided in the developer reservoir to scrape off excess developer from the developing sleeve 2 so that it is not conveyed to the developing sleeve 2.

Toner equivalent to the amount consumed by development is replenished into the developer reservoir by a supply means 8 from a hopper located above the back of the developing device, and is stirred by a stirring member 7 so as to uniformly mix with the developer in the developer reservoir. . The stirring member 7 also triboelectrically charges the toner. As mentioned above, the developer homogenized by stirring is attracted to the surface of the rotating developing sleeve 2 by the magnetic force of the magnet body 3, and
The layer thickness is regulated by the spike control member 4, and the development area E
transported to.

In the developing device described below, toner tends to leak from the developer transport downstream edge 9 of the developing device casing, which is open to expose the peripheral surface of the developing sleeve 2 to the image carrier 1. I have a problem to say.

This problem is significant in image forming apparatuses in which the developer is transported by rotation of the developing sleeve 2, and the transport direction and the moving direction of the image carrier surface are in the forward direction.

This problem occurs when an image forming apparatus is equipped with a plurality of developing devices each using toner of a different color as a developer. This has a large impact because it causes the problem of contamination with equipment.

In order to solve the above-mentioned problem, the present applicant previously disclosed in Japanese Patent Application No. 62-264238 that a developing area is provided at the downstream side line of the opening of the developing device casing that exposes the developer carrier to the image carrier. An image forming apparatus using a developing device in which a developer receiver that touches the bottom forms a part, and the receiver has an inward protrusion close to the surface of the developer carrier on the back side when viewed from the image carrier side of the part. The invention has been filed. However, in the image forming apparatus of this prior application, there is a problem in that the developer receptacle of the developing device casing has an inward protrusion formed on the back side that is close to the developer carrier surface, making it quite troublesome to produce the developing device. .

[Problem to be solved by the invention]

The present invention was made based on the discovery that toner can be prevented from leaking or blowing out from the developing device even if the edge of the opening of the developing device casing is bent so as to be close to the surface of the developer carrier. An object of the present invention is to provide an image forming apparatus using a developing device that is easy to produce by preventing toner from leaking or blowing out by such a simple means.

[Means to solve the problem]

The present invention provides an electrostatic image formed on the circumferential surface of a rotating image carrier by carrying a developer on the circumferential surface of the developer carrier and transporting the developer so as to pass through a position close to the image carrier. In an image forming apparatus equipped with a developing device that visualizes image, the downstream edge of the developer transport side of the opening of the developing device casing that exposes the peripheral surface of the developer carrier extends so as to approach the image carrier. Bend the tip so that it approaches the surface of the developer carrier,
The image forming apparatus is characterized in that the distance between the tip and the surface of the developer carrier is 1.7 mm or less and is greater than or equal to the maximum thickness of the developer layer passing through this position. The above objective is achieved by:

[Effect]

That is, the image forming apparatus of the present invention prevents toner from leaking or blowing out by a simple means in which the developing device bends the downstream edge of the opening of the casing toward the developer carrier and brings it close to a predetermined gap. Therefore, manufacturing of the developing device is easy.

Note that if the gap between the tip of the casing bent toward the developer carrier side and the surface of the developer carrier exceeds 1.7 mm, toner will blow out due to backflow from the developer reservoir, and the excess will pass through the gap. If the thickness is less than the maximum thickness of the developer, the surplus developer cannot be returned stably into the developing device, making it easy for toner to blow out or leak.

〔Example〕

The present invention will be explained below with reference to the embodiment shown in FIG.

FIG. 1 is a cross-sectional view of essential parts of an example of the image forming apparatus of the present invention, and the same reference numerals as in FIG. 2 indicate the same functional members.

In the developing device shown in FIG. 1, the downstream edge 9 of the developer conveyance of the developing device casing is bent so that the leading end thereof, which extends so as to approach the image bearing member l, approaches the surface of the developing sleeve 2. The developing device differs from the developing device shown in FIG. 2 in that the distance a from the developing sleeve 2 is 1.7 mm or less and the maximum thickness b of the developer layer passing through this position is greater than or equal to the maximum thickness b of the developer layer passing through this position, and amm is 1.7≧
By satisfying a≧b, the surplus developer that has passed through the development area E can stably return to the developer reservoir, and the toner does not flow backwards and blow out from the developer reservoir. Note that b can be measured, for example, by photographing the surface of the developing sleeve 2 having the developer layer from the side. In other words, b is also the apparent thickness.

In addition to the above, the developing device shown in FIG. 1 can replace the adhered developer on the developing sleeve 2 with enough fresh developer using the developer stirred by the stirring member 7, so that the returned surplus developer can be used for developing. The toner supplied from the hopper by the supply means 8 is first fed into the pre-mixing chamber so that a scraper for stripping it off from the sleeve 2 is not provided and the supplied toner is sufficiently mixed with the developer in the developer reservoir. The mixture is mixed with the developer from the developer reservoir in the mixing supply means 8', and a part of the mixture is sent into the developer reservoir through a hole (not shown) provided in the partition wall, and the rest is sent to the second premixing chamber and the developer is mixed with the developer from the developer reservoir. This is different from the developing device shown in FIG. 2 in that after being further mixed by the two mixing supply means 8'', the developer is sent to the developer reservoir through a hole 1o provided in the partition wall.

The present invention is limited to a developing device that uses a two-component developer, but may also be one that uses a one-component developer, and is not limited to one that faces the horizontal surface of the image carrier, but one that faces the downward surface. Good too. Further, the number of developing devices is not limited to one, but a plurality of developing devices may be provided.

〔Effect of the invention〕

In the image forming apparatus of the present invention, the developing device has a distance of 1 from the downstream edge of the casing opening to the surface of the developer carrier.
, 7 mm or less, which is greater than the maximum thickness of the developer layer passing through it, so that it can be developed into a toner image with sufficient density in the developing device, and the toner does not flow out from the developing device. It is possible to obtain the excellent effect that there is no spilling or blowing out, and the production of the developing device is easy.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a main part showing an example of an image forming apparatus according to the present invention, and FIG. 2 is a sectional view of a main part showing an example of a conventional image forming apparatus. ■...Image carrier 2...Developing sleeve 3...
... Magnet body 4 ... Ear stand regulating member 7 ...
Stirring member 8... Supply means 8'... Stirring and supplying means 8''... Second stirring and supplying means 9... Downstream edge E of developing device casing... Development area

Claims (2)

[Claims] (1) The electrostatic image formed on the circumferential surface of the rotating image carrier by carrying the developer on its circumferential surface and transporting the developer through a position close to the image carrier. In an image forming apparatus equipped with a developing device that visualizes an image, the downstream edge of the developer transport side of the opening that exposes the circumferential surface of the developer carrier in the developing device casing has a tip that extends so as to approach the image carrier. is bent to approach the surface of the developer carrier, and the distance between the tip and the surface of the developer carrier is 1.7 mm or less and is greater than or equal to the maximum thickness of the developer layer passing through this position. An image forming apparatus characterized by: (2) The image forming apparatus according to claim 1, wherein the developer carrier rotates in a developer transport direction, and the developer transport direction of the developer carrier and the moving direction of the image carrier surface are the same direction.