JPS5922941B2 - Electrostatic image developing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrostatic image developing apparatus that prevents the fogging phenomenon that occurs when developing an electrostatic latent image formed on an electrostatic latent image support.

It is generally known that when the developer deteriorates, fog occurs in copied images.

This fog is a phenomenon in which a small amount of toner adheres to the non-developing area of the photoconductor surface, but the cause of the deterioration of the conventionally known developer consisting of two components, toner and carrier, is as follows.
The toner sticks to the carrier surface, reducing the direct friction between the toner and the carrier, and reducing the triboelectric charging effect of the carrier on the toner. Furthermore, as a large number of copies are made while repeatedly consuming and replenishing the toner in the developing device, only the fine toner particles that are easily developed are consumed, and the large toner particles that are difficult to develop remain in the developer. It turns out that this is a major cause of fogging. In this fog development, fog caused by extremely fine toner particles of several microns uniformly adhering is not noticeable at first glance, but fog caused by large toner particles of about 50 microns adhering becomes extremely noticeable. The reason why these large toner particles cause fogging and affect copied images is that large toner particles have a weak frictional charging force in terms of mass ratio and weak adhesion retention force to the carrier, so the developer supports the electrostatic latent image. It is conceivable that the electrostatic latent image adheres to the non-image surface of the electrostatic latent image support due to some factor such as the impact force when it comes into contact with the body surface or the mechanical ejection force of the developing device. The present invention has been specifically proposed to eliminate the above-mentioned drawbacks. That is, an air flow forming device forms an air flow outside the developer movement and circulation path in the developing device, and an impact member is provided in the developer movement and circulation path to apply an impact to the developer. At this time, fine particles of toner suitable for development have good adsorption to the carrier and are not dispersed from the carrier due to impact action, but large particles of toner having a large mass are discretely ejected from the carrier. The air flow is passed through the discharged position to suck and collect large toner particles. Therefore, only fine particles of toner remain in the developer, and the above-mentioned defects can be prevented. An embodiment of the present invention will be described below. Reference numeral 1 shown in FIG. 1 is a rotating sleeve made of a non-magnetic material, and inside the sleeve there is provided a series of developer conveying devices 1' having a group of magnets 2 fixedly attached to the outer periphery. A developer conveying device V for conveying developer is housed in a housing 3. Inside the housing 3, the developer 4 is conveyed by rotating the rotary sleeve 1 in the direction of the arrow with the developer 4 interposed therebetween. The thickness of the developer is adjusted by a doctor blade 6, and the developer passes through a developing section 7 and reaches a scraping plate 8.
Due to the movement of the developer 4, the developer hits the scraping plate 8 and is subjected to a mechanical impact force, so that the toner is easily separated from the carrier. On the other hand, an air flow generating device A is provided in the upper part of the casing 3, and the air flow as shown by the arrow 9 flows into the inside of the casing 3, passes near the developer scraping part 8, and then flows into the casing as shown by the arrow 10. An air flow is created that is sucked out of the body. Here, toner that is weakly triboelectrically charged, that is, tends to cause large fogging particles, is separated from the carrier by the impact and is discharged into the air stream. In particular, large toner particles have a large mass, so the impact force is strong, and frictional electrification is weak, so they are easily released from the developer 4, that is, from the carrier. The released toner is removed from the developing device by air flow. What is particularly necessary in such a configuration is to prevent the toner replenishing part 11 and the toner replenishing port 12 from being affected by the air flow, in order to prevent the newly replenished toner from being removed at the same time. A part of the circulating developer is always closed. With this method, only large toner particles are collected. As an example of the effects achieved by the above means, fog was able to be suppressed to one-third of the conventional level when measured using a reflection density measuring method with the developer used. Furthermore, the amount of charge on the attracted toner was one-fifth of that of normal toner expressed per unit weight. Next, referring to FIG. 2, a group of pins 13 are placed upright on the scraping plate 8 to strengthen the impact on the developer 4. Similarly, in FIG. This device improves non-uniformity of toner concentration by erecting a group of panels 14 that divide the flow of toner in the direction of developer movement, and also serves as an impact means.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional side view of a developing device according to the present invention, and FIG.
This figure and FIG. 3 are perspective views showing a modification of the developer scraping plate 8 used in the developing device shown in FIG. 1... Rotating sleeve, 2... Magnet group,
3... Housing, 4... Developer, 6...
...Doctor blade, 7...Development section, 8.
..... Scraping plate, 11 ..... Toner supply section, 1
2... Fall port, 13... Pin group, 14
... Panel group, A ... Air flow generator.

Claims (1)

[Claims] 1 In a dry-type developing device that develops an electrostatic image formed on an electrostatic latent image support while sequentially moving and circulating the developer using a conveying device with a built-in magnet, an air flow forming means forming an air flow path near the impact means and in close proximity to the developer movement and circulation path; and a developer recovery means provided in the air flow path. An electrostatic image developing device characterized by: