JPS627067A - Developing device - Google Patents

Abstract

PURPOSE:To reduce toner stagnation by positioning the center axis of a feed roller lower than a horizontal surface including the center axis of a developing roller and contacting or intersecting a vertical surface including the center axis of the feed roller with the developing roller. CONSTITUTION:The center axis X of the feed roller 4 is positioned lower than the horizontal surface (h) including the center axis Y of the developing roller 5 and the vertical surface (v) including the center axis X of the feed roller 4 is positioned so as to be contacted or intersected with the developing roller 5. When it is defined that the radius of the developing roller 4 is R, the radius of the feed roller 4 is (r), an angle formed by a plane (p) including the center axis Y of the developing roller 5 and the center axis X of the feed roller 4 and the horizontal surface (h) is theta, and an angle formed when the vertical surface (v) including the center axis X of the feed roller 4 is just contacted with the periphery of the developing roller 5 is theta0, the shown equation is formed and the angle theta is set up so that theta>=theta0 is satisfied by the developing device. As the feed roller 4 is positioned on a comparatively lower part, the trouble of toner stagnation can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a developing device having a developing roller that conveys toner to develop an electrostatic latent image, and a replenishment roller that supplies toner to the developing roller.

Moxibustion Skin 4 The applicant has already proposed the use of a developing device of the above type in order to visualize an electrostatic latent image formed on a latent image carrier in a recording device such as an electronic copying machine or a printer. has been done. Since this type of developing device has a replenishment roller, it has the advantage of being able to actively supply toner to the developing roller not only when magnetic toner is used, but also when non-magnetic toner is used. ing. However, as a result of recent studies, toner accumulates in the area above the area where the replenishment roller and developing roller face each other, and this impedes the supply of toner to the developing roller, resulting in an insufficient amount of toner supplied to the developing roller, and It has been found that the quality of visual images may deteriorate.

1. The present invention is based on the above-mentioned novel recognition,
The object is to provide a developing device of the type mentioned at the outset, in which toner retention can be reduced as much as possible with a simple construction.

慅I! In the present invention, the central axis of the replenishment roller is located below a horizontal plane including the central axis of the developing roller, and the vertical plane including the central axis of the replenishing roller is located in contact with or intersects with the developing roller. We propose the following configuration.

An embodiment of the present invention will be explained below in comparison with a conventional configuration example.

FIG. 1 shows an example of a developing device according to the present invention, in which powdered toner 2 contained in a toner container 1 is stirred by a stirring paddle 3, and a replenishment roller rotates counterclockwise (or in the opposite direction). 4.

The toner on the replenishment roller 4 is conveyed to the developing roller 5, which rotates counterclockwise, by the rotation of the replenishment roller 4. At the contact point between the replenishment roller 4 and the developing roller 5, the toner is strongly rubbed and charged to a predetermined polarity, and the toner is attracted onto the developing roller 5, which is induced to have a polarity opposite to the charged polarity of the toner. It is conveyed in the direction of rotation while being carried by the. This toner is thicker than the toner thickness regulating blade 6.
When passing through the toner, the layer thickness of the toner is regulated and preferably arranged into a single layer. The toner that has passed through the blade 6 is further conveyed while being carried by the developing roller 5 in a thin layer, approaching the latent image carrier 7 made of, for example, a photosensitive drum or a dielectric drum (or belt), and then being carried by the developing roller 5. When the toner reaches the opposing development area of the electrostatic carrier 7, the toner electrostatically transfers to the electrostatic latent image formed on the latent image carrier 7, and the latent image is visualized.

The toner may be magnetic or non-magnetic, but when magnetic toner is used, it is common practice to incorporate a magnet into the developing roller 5 and transport the toner while attracting it toward the developing roller using magnetic force. be. Further, when the magnet is rotated to convey the toner, the developing roller 5 can be stopped, or depending on the case, the developing roller 5 can be rotated clockwise in FIG. 1.

Regarding the above-mentioned structure and operation, there is no difference from the conventional developing device illustrated in FIG. 4. The parts in FIG. 4 that correspond to those in FIG. 1 are given the same reference numerals as in FIG. What is the difference between the two?

In the conventional developing device shown in FIG. 4, toner remains in an area above the facing portion of the supply roller 4 and the developing roller 5, that is, an area A shown with hatching in FIG.
This stagnant toner hinders the supply of new toner. When the toner stays, since the toner is constantly under pressure, its density increases and it aggregates, resulting in an insufficient amount of toner supplied to the developing roller 5.

In the developing device shown in FIG. 1, in order to eliminate the above-mentioned drawbacks, the relative positions of the developing roller 5 and the supply roller 4 are determined as follows. That is, the central axis X of the replenishment roller 4 is located below the horizontal plane including the central axis Y of the developing roller 5, and the vertical plane V including the central axis X of the replenishing roller 4 is in contact with the developing roller 5. , are located at an intersection. More specifically, it is as follows.

Now, the radius of the developing roller 5 is R1 and the radius of the replenishing roller 4 is R.
In addition, the angle between the horizontal plane and a plane p including the central axis Y of the developing roller 5 and the central axis X of the replenishing roller 4 is θ, and the vertical plane V including the central axis X of the replenishing roller 4 is the second As shown in the figure, the angle θ when exactly touching the circumferential surface of the developing roller 5 is θ. Then, θ. is given by cosθo = −0) R+r, but in the developing device according to the present invention, the angle θ is θ≧
θ. is set to meet. With this configuration, the replenishment roller 4 with respect to the developing roller 5
Since the position is relatively lowered, the inconvenience of toner retention as shown in FIG. 4 can be reduced as much as possible.

In Figure 4, θ is θ. Therefore, the replenishment roller 4 is positioned in a higher position than in the case of FIG. 1, and toner tends to stay in the area A above the replenishment roller 4.

The supply roller 4 can be made of any suitable material, but when it is made of an elastic material such as foam, it is pressed against the developing roller 5 as shown in FIG.

It is also possible to arrange the abutment portion by elastically deforming it. In such a case, the amount of biting of the replenishment roller 4.

That is, if the amount of compression of the replenishment roller 4 in the radial direction due to the pressure from the developing roller side is t, then rtt in equation (1)
It is sufficient to replace it with rt and set it to 0 so that θ≧00 is satisfied.

According to the present invention, with a simple configuration, toner retention can be suppressed and toner can be smoothly conveyed to the latent image carrier.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view showing an example of a developing device according to the present invention, and FIG. 2 is an explanatory view showing a state in which a vertical plane including the central axis of a supply roller is in contact with the developing roller. FIG. 3 is a schematic sectional view showing an example in which the replenishment roller is disposed in a state where it bites into the developing roller, and FIG. 4 is a schematic sectional view showing an example of a conventional developing device. 2... Toner 4... Supply roller 5...
Developing roller h...Horizontal surface V...Vertical surface X, Y...
Center axis Figure 1 Figure 2 Figure ○

Claims (1)

[Scope of Claims] In a developing device including a developing roller that conveys toner to develop an electrostatic latent image and a replenishment roller that supplies toner to the developing roller, the central axis of the replenishment roller is aligned with the center of the developing roller. A developing device characterized in that the developing device is located below a horizontal plane including an axis, and is located so that a vertical plane including a central axis of the replenishment roller touches or intersects with the developing roller.