JPH0251177A - Gap holding mechanism - Google Patents

Abstract

PURPOSE:To keep a gap between a developing sleeve and a latent image carrier drum constant in an axial direction by holding the central axis of the developing sleeve and the central axis of the latent image carrier drum in parallel. CONSTITUTION:The developing sleeve 2 abuts on the latent image carrier drum 1 through a spacer ring 3 at an abutting line 4a and the latent image carrier drum 1 is apart from the developing sleeve 2 as much as the thickness of the spacer ring 3. Besides, it is held in a fixed distance from the developing sleeve 2 by a base 6 and an auxiliary roller 5 held on an axis which is in parallel with the axis of the developing sleeve 2 abuts on the latent image carrier drum 1 at an abutting line 4b being in parallel with the abutting line 4a. The whole of them is fixed to a developing unit main body at the coupling point 7 of the base 6 and the interacting line of abutting force A which is propagated at the coupling point 7 turns to a spot between the abutting lines 4a and 4b. By the gap holding mechanism, the central axis of the developing sleeve 2 is held in parallel with the central axis of the latent image carrier drum 1. Thus, the gap between the developing sleeve 2 and the latent image carrier drum 1 can be held constant in the axial direction.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a gap holding mechanism, and particularly to a gap holding mechanism between a latent image carrier drum and a developing sleeve in a developing device of an electrostatic image forming apparatus.

[Prior Art] Conventionally, the gap between the latent image carrier drum and the developing sleeve in the developing device of an electrostatic image forming apparatus is relatively narrow, although it varies depending on the developing method, especially in non-magnetic component methods and static In the liquid development method, which uses an electric field to attract the liquid toner itself, it is necessary to stably maintain a narrow gap of 200 μm or less, and as a means to do so, it is necessary to insert a spacer with the thickness of the gap between the latent image carrier drum and the developing sleeve, or as shown in Figure 4. As shown in FIG. 2, ring-shaped spacers 3 are placed over both ends of the developing sleeve 2 and pressed against the latent image carrier drum 1 to ensure a gap.

[Problems to be Solved by the Invention] There is no problem with the conventional gap holding mechanism described above when the central axes of the latent image carrier drum 1 and the developing sleeve 2 are positioned parallel to each other. If the central axes are not parallel but are pressed in a twisted position as shown in Figure 6, the gap will not be constant and will be wider at both ends and narrower at the center, as shown in Figure 6, resulting in the development characteristics changing at the center. In the worst case, the latent image carrier tram 1 is different in the center.
There is a drawback that the developing sleeve 2 may come into contact with the developing sleeve 2.

[Means for Solving the Problems] The present invention has been made to solve the above problems. In the gap holding mechanism that maintains the gap, two or more points of contact with the developing sleeve or the latent image carrier drum are on a straight line parallel to the central axis of the latent image carrier drum, and this straight line is on another parallel line above. The developing sleeve has at least one contact point with the latent image carrier drum at both ends thereof.

[Example] Next, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a side view of a gap holding mechanism according to an embodiment of the present invention, viewed from the axial direction of a latent image carrier drum and a developing sleeve.

The developing sleeve 2 is in contact with the latent image carrier drum 1 at a contact line 4a via a spacer ring 3, and the latent image carrier drum 1 and the developing sleeve 2 are separated by the thickness of the spacer ring 3.

Further, the auxiliary roller 5, which is maintained at a constant distance from the developing sleeve 2 by the base 6 and supported on an axis parallel to the axis of the developing sleeve 2, is connected to the contact line 4b, which is parallel to the contact line 4a.
The latent image carrier drum 1 is in contact with the latent image carrier drum 1.

All of these are fixed to a developing device main body (not shown) by a connecting point 7 of the base 6, and the line of action of the abutting force A transmitted by the connecting point 7 is directed between the abutting lines 4a and 4b.

Since the central axis of the developing sleeve 2 is held parallel to the central axis of the latent image carrier drum 1 by this gap holding mechanism, the distance between the developing sleeve 2 and the latent image carrier drum 1 is kept constant in the axial direction.

Furthermore, if such a gap holding mechanism is provided at both ends of the developing sleeve 2 as shown in FIG. 2, the effect of keeping the central axis of the latent image carrier drum 1 and the central axis of the developing sleeve 2 parallel to each other is greater. preferable.

FIG. 3 is a diagram showing another embodiment of the present invention.

In this case, the developing sleeve 2 is in contact with the latent image carrier drum 1 at a contact line 4a and one end of the base 6 is in contact with the latent image carrier drum 1 at a contact point 4C via a spacer 8 fixedly supported by a mechanism not shown. Similarly, the central axis of the developing sleeve 2 is held parallel to the central axis of the latent image carrier drum 1, and the gap is kept constant.

[Effects of the Invention] As explained above, the gap holding mechanism of the present invention has two or more contact points with the developing sleeve or the latent image carrier drum that are on a straight line parallel to the central axis of the latent image carrier drum; Since the developing sleeve has one or more points of contact with the latent image carrier drum on both sides of the latent image carrier drum, which are on another parallel line different from the straight line, the center axis of the developing sleeve and the center axis of the latent image carrier drum are The developing sleeve and the latent image carrier drum can be held parallel to each other, so that the gap between the developing sleeve and the latent image carrier drum can be kept constant in the axial direction.

[Brief explanation of the drawing]

FIG. 1 is a side view of a gap holding mechanism according to an embodiment of the present invention viewed from the axial direction of a latent image carrier drum and a developing sleeve;
Fig. 2 is a front view seen from a direction perpendicular to the axis, Fig. 3 is a side view of another embodiment similarly seen from the axial direction of the developing sleeve, etc., and Fig. 4 is a perspective view of an example of a conventional gap holding mechanism. 5 is a front view of this as seen from a direction perpendicular to the central axis of the latent image carrier drum, and FIG. 6 is a special drawing showing the gap distribution of the conventional example. :Latent image carrier drum 2:Developing sleeve 3 Varnish spacer ring 4a. 4b Two contact lines 4c: Contact point 5: Auxiliary roller 6: Base 7: Connection point 8 Varnish spacer

Claims (1)

[Claims] In a gap holding mechanism that maintains a constant gap between the latent image carrier drum and the developing sleeve of the developing device, two or more points with respect to the latent image carrier drum are located on a straight line parallel to the central axis of the developing sleeve or the latent image carrier drum. and the latent image carrier drum which is on another parallel line different from this straight line.
1. A gap holding mechanism characterized by having at least one contact point on both end sides of a developing sleeve.