JPH02139587A - Developing device - Google Patents

Abstract

PURPOSE:To prevent soiling due to scattering of toner with a simple constitution by providing a depressurizing hole with a filter on at least one place of developing unit housing in a dry, two-component developing device and also providing air flow guide plates of specific dimensions downstream of a development opening. CONSTITUTION:The title device 2 has the housing 13 with the opening confronted with a photosensitive drum 1, and a developing sleeve 3 which moves toward the drum 1 through the opening provided in the housing and rotates. The sleeve carries a developer 7 to a developing part and recovers the developer used for development into the housing 13 through a sleeve lower opening 6. At this time, a depressurizing hole 14 for inner pressure is provided on at least one place of the housing 13, and the hole is covered with the filter 4. Simultaneously, the smooth air flow guide plates 5 with a width of 5mm or above are spaced at the intervals of 2mm opposite to the drum 1 on almost the entire opening. The air flowing from the opening 6 is allowed to escape owing to the rotation of the sleeve 3, etc., from the hole 14, thereby preventing toner from blowing inside the device.

Description

[Detailed description of the invention] Good! 1. Field of the Invention The present invention relates to a dry two-component developing device for an electrostatic recording device, and particularly to a device for preventing leakage of toner from a developing device housing.

In the dry two-component developing device, which is widely used as a developing device for electrostatic recording devices such as electrophotographic copying machines and laser printers, the developing device is provided in a housing having an opening formed opposite to the surface of the photoreceptor. A developing sleeve that rotates close to the photoconductor surface through the above-mentioned opening carries a dry two-component developer consisting of toner and carrier, and conveys it to a developing section close to the photoconductor, where it forms a magnetic brush and is exposed to light. Development is performed by adhering toner to an electrostatic latent image formed on the body by an electrostatic photographic process. After development, the developer remains adsorbed by the developing sleeve, and as it rotates, it is returned into the housing through the gap between the edge of the housing opening and the developing sleeve, where the missing toner is replenished and agitated, and the development is carried out again. It is used for.

The developing device housing is sealed except for the opening through which the developing sleeve faces the photoreceptor to prevent developer from leaking. Therefore, the internal pressure inside the developer housing increases due to the inflow of air as the developing sleeve rotates and the rotation of the stirring roller, and the toner cloud is blown out from the gap between the edge of the opening and the developing sleeve, and then the toner cloud is blown out from the gap between the edge of the housing opening and the developing sleeve. It is likely that it will spray out into the machine from the gap between it and the photoconductor, contaminating the interior of the machine.

On the upstream side of the developing section where the developing sleeve and photoreceptor are close to each other, a doctor blade is provided with a small gap on the surface of the developing sleeve, and since no toner image has yet adhered to the photoreceptor surface, the edge of the housing and the photoreceptor surface A sealing member can be provided between the developing sleeve and the opening, but on the downstream side of the developing section, an appropriate gap is required between the developing sleeve and the edge of the opening in order to allow the developer on the developing sleeve to pass through. Further, it is necessary to provide a required distance between the edge of the housing opening and the photoreceptor so that the unfixed toner image can pass through without being disturbed. Therefore, the toner cloud blows out from the above two dose lines downstream of the developing section.

Various methods have been considered to prevent the toner cloud from blowing out. Among them, a hole is provided in the developer housing to release the internal pressure, and a filter is installed in the hole to prevent toner from passing through. For example, Japanese Patent Laid-Open No. 56-46272, Japanese Patent Laid-Open No. 56-99604,
This is disclosed in Japanese Patent Application Laid-Open No. 60-3678.

However, in the first type, the pressure relief hole provided in the housing is connected to a vacuum suction device, and in the third type, air is released from the gap between the opening of the housing facing the photoreceptor drum and the surface of the photoreceptor drum. Both systems require vacuum pumps, air compressors, and piping, resulting in high costs. In the second type, the direction of rotation of the developing sleeve is set in one direction counter to the photoreceptor drum to generate an airflow in the direction of sucking air from between the green opening of the housing and the photoreceptor drum. However, if the direction of rotation of the developing sleeve is not one direction toward the photoreceptor drum and the counter, there is a possibility that the toner cloud will blow out.

In view of the above-mentioned situation of preventing the toner cloud from blowing out in the conventional two-component developing device, the present invention provides a means for providing an internal pressure relief hole in the housing and a toner filter to close the hole, and uses a vacuum pump or an air compressor. There is no need for mechanical devices such as machines and piping connected to them, and it is possible to prevent the toner cloud from blowing out even when the developing sleeve is rotated in the forward direction relative to the photoreceptor, which is usually used. It is an object of the present invention to provide a developing device having a simple configuration and an inexpensive toner blow-out prevention device.

In order to solve the above-mentioned problems, the present invention provides a dry two-component developing device in which a pressure relief hole is provided at at least one location in the developer housing, and the hole is blocked to prevent toner from passing through. A filter is provided in a ridge on the downstream side of the developing opening of the housing with respect to the rotational direction of the photoreceptor, and is arranged opposite to the photoreceptor and connected to the surface of the photoreceptor.
The present invention is characterized in that smooth airflow guide plates having a width of 5 mm or more are provided at intervals of 5 mm or less over approximately the entire width of the opening.

In addition to providing a hole for internal pressure relief in the Tsutsuki housing, the airflow guide plate is installed at a distance of 21I1m or less from the photoreceptor as described above.
By providing a width of ++n+ or more over almost the entire width of the opening, an airflow flowing from the outside toward the housing opening is generated in the gap between the photoreceptor and the airflow guide plate, and the airflow in the housing is directed toward the developing sleeve. The toner cloud flows into the housing between the toner and the edge of the housing, and the toner cloud is prevented from blowing out.

EXAMPLE Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram showing the overall configuration of an embodiment of a two-component developing device to which the present invention is applied.

The housing 13 of the developing device 2 is provided with an opening facing the circumferential surface of the photoreceptor drum l, and the developing sleeve 3 provided in the housing 13 is connected to the photoreceptor drum l through this opening.
The development gap Gp is located close to the development gap Gp. The developing sleeve 3 rotates in the forward direction relative to the photoreceptor drum l. The developer 7 in the developing device 2 is stirred by the stirring roller 9, charged, and sent to the developing sleeve 3.
The developing material is attracted to the surface of the developing sleeve by the magnetic force of a magnet provided inside and is conveyed, and the layer thickness is regulated by a doctor 8 installed opposite to the developing sleeve 3 with a predetermined doctor gap Gd, and the developing material comes into contact with the photoreceptor drum 1. sent to the department. After developing the electrostatic latent image on the photosensitive drum in the developing section, the developer passes through the opening 6 between the lower part of the sleeve and the housing and is recovered into the developing device 2 again. Since the toner in the collected developer has been consumed by development, the replenishment toner 11 in the toner tank 10 is replenished according to the opening and closing of the toner replenishment shutter 12, and is stirred together with the developer. A hole 14 for releasing internal pressure is provided in the upper part of the developing device housing 13.
This hole is closed with a filter 4 that does not allow toner to pass therethrough so that the toner cloud does not blow out.

Numerical values of an example of an actual developing device having the above configuration are shown below.

・Developer capacity in the developing unit: 1.0 to 1.4 kg
・Developer carrier average particle size: approx. 100 μm Toner average particle size: approx. 10 μm Toner weight ratio: 1.5 to 4 wt% ・Photoconductor diameter: approx. φ80 ・Developing roller diameter: approx. φ40 ・Photoconductor linear speed
180 mm/sec・Developing roller linear speed (photoreceptor linear speed) x approx. 2.7 times・Doctor gap (G d
) 0.6-0.9111m・Development gap
(G p ) 0.8 to 1.1 ++ua As the developing sleeve 3 rotates, air flows in through the opening 6 with the help of the rotation of the stirring roller 9, but the internal pressure inside the housing is reduced by the internal pressure release hole 14. Even if the air does not rise through the pressure relief hole 14, the toner is blocked by the filter 4 and will not be blown out into the machine.

As shown in detail in FIG. 2, a smooth air guide plate 5 having a width β is provided on the edge of the opening 6 of the housing, with a distance d from the circumferential surface of the photoreceptor drum, extending over approximately the entire length of the opening. ing.

The function of this airflow guide plate 5 will be explained below.

FIG. 3 qualitatively shows the relationship between the air velocity at the center of the sleeve and the internal pressure of the housing. The lower the internal pressure, the greater the suction wind speed.

Figure 4 (at, (bl) shows the wind velocity distribution in the width direction at the lower opening of the sleeve when the housing has no pressure relief hole and no airflow guide plate, and when it has a pressure relief hole, respectively, based on experimental results. (In al and fbl, suction occurs at the center of the sleeve, but it changes to blowout at both ends.Also, at the boundary, there is an unstable region where suction and blowout alternate irregularly.lal Comparing fbl and fbl, it can be seen that by providing the pressure relief hole, the suction wind speed becomes stronger in the center, and the blowout wind speed weakens at both ends, and the overall flow shifts to suction.

FIG. 5 shows the results of actually measuring the toner scattering amount distribution in the width direction of the developing sleeve in the case of FIG. 4 fa). Figure 4 fat
As is clear from a comparison between and FIG. 5, the toner scattering distribution corresponds to the wind speed distribution of the blown air flow.

FIG. 6 shows the distance d between the airflow guide plate 5 and the photosensitive drum 1.
(See Figure 2) shows changes in suction wind speed when changing. As you can see from the diagram, between T? , d increases, and this can be understood from the fact that when the flow velocity is constant, the cross-sectional area of the flow path and the flow velocity are inversely proportional. From this figure,
In order to obtain a certain amount of suction force, the distance d should be set to 211I.
It turns out that it is sufficient to make it less than l.

In addition, the relationship between the width of the airflow guide plate in the flow direction and the wind speed is
As shown in the figure. If the width of the airflow guide plate is short, the turbulence of the airflow that occurs below it becomes an obstacle to smooth suction, and the wind speed decreases. Therefore, it can be seen from the figure that in order to obtain the effect of smooth suction by the airflow guide plate, this width should be set to 5 m1W or more.

FIG. 4fcl shows the wind velocity distribution at the lower part of the sleeve when an internal pressure relief hole and an airflow guide plate satisfying the above conditions are provided based on the present invention. In this case, the unstable region is reduced, the range of the blowout region and the wind speed at both ends become significantly smaller, and it can be seen that the overall tendency is to turn to suction.

As a result, as shown in FIG. 8, the toner scattering amount distribution was reduced to only a small portion at both ends of the developing sleeve in the width direction, corresponding to the blown airflow distribution, and the amount could be significantly reduced.

As described above, according to the present invention, with a simple configuration, toner scattering from the developing device can be prevented, and contamination by toner inside the machine can be prevented.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing the overall structure of a developing device according to an embodiment of the present invention, FIG. The figure is a curve diagram for explaining the effects of the present invention. 1...-Photosensitive drum (image carrier) 2...Developing device 4...Filter 6...Sleeve lower opening 13...Housing 3...Developing sleeve 5...Air flow guide plate 7... ...Developer 14... Internal pressure release hole load 1 Figure 6 Figure 2 d (mm) Figure 7 1 (mm) 8th factor

Claims (1)

[Scope of Claims] A housing having an opening formed opposite to the surface of the image carrier, and a housing provided within the housing that approaches the surface of the image carrier through the opening and rotates to bring the developer into contact with the image carrier. The dry type 2 includes a developing sleeve that is conveyed to a developing section to perform development, and that the developer after development is carried on the developing sleeve and collected into the housing through a gap between the developing sleeve and the opening. In the component developing device, the housing is provided with a pressure relief hole provided in at least one location, and a filter that closes the pressure relief hole and prevents passage of toner, and the housing opening is located downstream of the housing opening with respect to the rotational direction of the image carrier. A developing device characterized in that a smooth air flow guide plate having a width of 5 mm or more is provided on the edge of the image carrier, facing the image carrier, at an interval of 2 mm or less from the surface of the image carrier, and extending approximately over the entire width of the opening.