JPH055568Y2 - - Google Patents

Description

[Detailed explanation of the idea] (Technical field) The present invention relates to a developing device.

(Prior Art) Regarding the developing device of a printer which is a copying machine or other printing means that uses electrophotography, it is known that the developing device has a developing roller that is pressed against a surface to be developed.

For example, in a developing device that uses non-magnetic one-component toner, a method is adopted in which the toner is formed into a thin layer on an elastic developing roller having a metal shaft, and the developing roller is pressed against a photoreceptor, which is the surface to be developed. However, this pressure contact force is applied to both ends of the metal shaft.

Generally, in order to maintain development quality, it is required that the pressing force be uniform in the axial direction. For this reason, the above pressure welding method requires the metal shaft to be strong, and in the current situation where a shaft with a diameter of 8 mm or less is used, the shaft flexes, so it is necessary to use a thick shaft, and the elastic body also becomes thick, making the device smaller. This has become an obstacle to the development of

(Objective) Accordingly, an object of the present invention is to provide a developing device that can bring the developing roller into pressure contact with the surface to be developed uniformly along the axial direction and can reduce the size of the device.

(Structure) In order to achieve the above object, the present invention includes a developing roller that supports the circumferential surface in the longitudinal direction of the developing roller in a float-like manner on a toner case and a toner supply roller arranged around the developing roller. The toner case is in contact with the photoreceptor drum, and a curved portion is formed in a portion of the toner case that faces the rear surface of the developing roller that is in contact with the photoreceptor drum to apply pressure uniformly to the developing roller. It is characterized by

The present invention will be specifically described below based on one embodiment of the present invention.

In FIG. 4, which describes the overall structure of the developing device, reference numeral 1 indicates a toner case, in which toner is accommodated.

Also, inside this toner case 1, an agitator 2,
A toner supply roller 3 and a developing roller 4 are each provided rotatably in the direction of the arrow. The developing roller 4 is pressed against the photosensitive drum 6. Further, the free end of a thinning blade 5 whose base end is fixed to the toner case 1 is provided in sliding contact with the developing roller 4 .

The toner in the toner case 1 is supplied to the developing roller 4 via a toner supply roller 3 made of, for example, a conductive sponge, and a conductor selected from metals such as Al or silicone resin depending on the polarity with the toner. A thin toner layer is formed with a constant thickness by the layering blade 5 and transferred to the photoreceptor drum 6.

Next, in FIG. 1, which is an enlarged view of the area around the developing roller in FIG. 3,
This is provided by supporting the peripheral surface of the developing roller in the axial longitudinal direction with a thinning blade 5 or the like.

Therefore, both ends of the shaft 8 of the developing roller 4 have a degree of freedom in rotation and displacement relative to the toner case 1, and the positional relationship with the toner case 1 is not restricted. Therefore, rotational power is also transmitted via a universal joint or the like.

The manner in which the developing roller 4 is supported by each of the peripheral members described above will be explained in more detail as follows.

Since the base end of the thinning blade 5 is fixed to the toner case 1, its free end is in elastic contact with the developing roller 4, and in addition to its original toner thinning function, it also has a developing roller supporting function. is fulfilled.

The toner supply roller 3 is pivotally supported by the toner case 1 , and the circumferential surface of the toner supply roller 3 in the longitudinal direction of the shaft is set in pressure contact with the circumferential surface of the developing roller 8 in the longitudinal direction of the shaft.

Therefore, the toner supply roller 3 also performs the function of supporting the developing roller in addition to the original toner supplying function and the function of neutralizing the charged developing roller. From the viewpoint of achieving this static elimination function, the material is preferably electrically conductive.

Furthermore, as shown in FIG. 1, the toner case 1 has a curved portion that faces the back surface of the developing roller 4 that is in contact with the photoreceptor drum 6, and a protruding strip on the portion that covers the developing roller 4. Support convex part 2
0 and 21 are formed in the axial direction so that the pressing force against the developing roller is uniform. The recesses formed relative to each other by forming the support projections 20 and 21 are filled with an elastic member 13 to prevent toner from accumulating.

Furthermore, a slippery sheet 12 made of fluororesin, polyethylene, etc. is adhered so as to commonly cover the elastic member 13, the supporting convex portions 20, 21, etc., to enable rotation of the developing roller 4 and prevent toner leakage. However, it is in contact with and supported on a wide surface.

In this manner, the developing roller 4 is supported in a so-called float-like manner using the above-mentioned peripheral members, and is positioned in such a manner that a pressing force is applied to the photosensitive drum 6.

According to this method of applying pressure force, the developing roller 4 is evenly pressed against the photoreceptor drum over the entire length of the shaft, regardless of the thickness of the shaft, even if the shaft has a diameter of 8 mm or less. It turns out. Therefore, there is no need to configure the shaft of the developing roller with a thick shaft as in the prior art.

Next, the structure of the developing roller 4 will be explained. For example, a conductive particle layer 10 made of resin, acrylic, polycarbonate, etc. in which metal powder (cu, Al, etc.) is dispersed is formed on the outer periphery of a cylindrical elastic body 9 made of conductive silicone rubber. is formed, and an insulating layer 11 made of acrylic resin is formed around the outer periphery. Since the toner T is attached to the outer periphery of the insulating layer 11 in a thin layer, the developing roller 4 is in fact supported in pressure contact with the photoreceptor drum 6 by the peripheral member through the toner layer. become.

When configured as in this example, there is an elastic member approximately equal to the diameter of the developing roller between the photoreceptor drum surface and the supporting convex portion 21, and as a result, the pressing force is not applied as in the prior art. Acts on both ends of the shaft,
Unlike the fact that there is only an elastic member corresponding to the radius, the spring constant that contributes to pressure welding is approximately 1/2,
A secondary effect is that the influence of dimensional accuracy, vibration, etc. on the pressure contact force can be reduced.

Incidentally, assuming that the force used on the elastic material corresponding to the above radius is F, the displacement is x, and the spring constant is k, the relationship between these is expressed as F=-kx. If two of these elastic materials are connected in series, that is, if they are made into diameters, they will exhibit twice the displacement for the same force F, so the above equation can be written as follows: If the new spring constant is k ₁ , then F = - k ₁ (2x) = −2k ₁ x.

Therefore, if k = 2k ₁ , then k ₁ = k/2, so it can be said that the spring constant is halved.

Incidentally, since a shaft is no longer essential for the developing roller, a structure without a shaft as shown in FIG. 3 may be used.
Alternatively, it may be hollow as shown in FIG.

In either case, the developing roller can be made small in diameter, making it possible to reduce costs and increasing the practicality of the disposable developing unit.

This example has the possibility of being implemented not only in a conventional dry type two-component developing device but also in a rotary developing device having a plurality of developing devices. This is because in the case of a rotary developing device, each developing device rotates, so the developer inside the developing device may go around to both ends of the developing sleeve when the developing device rotates. Moreover, when the developing device rotates, developer enters both ends of the sleeve, impairing the reliability of the bearing.

In this regard, since the developing roller does not necessarily have a shaft in this example, there is no need to consider wear and tear on the bearing due to intrusion of developer.

(Effects) As described above, according to the present invention, there is no need for the shaft of the developing roller, and pressure is applied uniformly from the back of the roller, thereby avoiding the adverse effects caused by deflection of the shaft, increasing the effective elastic body thickness, and reducing vibration. This is advantageous in that it is possible to avoid adverse effects on image quality, etc., increase dimensional margin, and reduce the size and cost of the device.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of the main parts of the developing device according to the present invention,
FIGS. 2 and 3 are cross-sectional views each illustrating an example of a developing roller, and FIG. 4 is an overall explanatory view of the developing device according to the present invention. 4...Developing roller, 20, 21... Support convex portion.

Claims (1)

[Scope of Claim for Utility Model Registration] In a developing device having a developing roller that is pressed against a surface to be developed, the developing roller The circumferential surface in the longitudinal direction of the shaft is supported in a float-like manner and is in contact with the photoreceptor drum, and the developing roller is uniformly applied to the portion of the toner case that faces the back side of the developing roller that is in contact with the photoreceptor drum. A developing device characterized in that a curved portion for pressing is formed.