JP2008242244A - Toner supply roller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a toner supply roller capable of eliminating image failure due to shortage of image density and ghost image. <P>SOLUTION: A toner conveyance roller 11 for supplying toner to a developing roller 11, has the average skeleton width Wk defined by formula (1) of 30 to 300 μm, in the formula (1) Sc represents the total of the open areas of cells that are open in the peripheral face of an elastic layer, Sf represents the area of the peripheral face of the elastic layer, and D represents the average diameter of the cells that are open in the peripheral face. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a toner conveying roller in which an elastic layer formed by opening a large number of cells on an outer peripheral surface is disposed around a shaft.

  In an image forming apparatus using an electrophotographic system such as a copying machine or a printer, toner (developer) is supplied to an image forming body such as a photoreceptor or paper, and toner is applied to a developing roller that forms a visible image on the surface. A roller called a toner supply roller is used for supplying. The supply roller is composed of a shaft and an elastic layer disposed around the shaft. By rotating the outer peripheral surface against each other against the developing roller, the supply roller rotates the outer surface of the elastic layer with new toner pumped up from the hopper. And the old toner scraped from the developing roller through the outer peripheral surface thereof is collected in a hopper.

  In order to give such a function to the toner supply roller, it is necessary to open a large number of cells capable of holding toner on the outer peripheral surface thereof, and to increase the amount of stored toner. In addition, it is preferable to provide a large number of cells that communicate with the cells that are open on the surface, and for this reason, polyurethane having such a continuous cell structure is used as the elastic layer for the toner supply roller. .

In such an elastic layer, as a standard of a good communication cell structure, for example, in Patent Document 1, the cell opening ratio that defines the ratio of the total area of cells opened to the outer peripheral surface of the elastic layer to the entire outer peripheral surface is described. It has been proposed to define an upper and lower limit. (For example, refer to Patent Document 1).
JP-A-10-221945

  However, even when a toner supply roller having an aperture ratio specified in the above proposal is attached to the image forming apparatus to form a visible image, the visible image is caused by insufficient toner supply capability and scraping capability of the toner supply roller. It has been found that problems such as insufficient density of image and generation of ghost images cannot be solved.

  The present invention has been made in view of such a problem, and an object thereof is to provide a toner supply toe or the like capable of eliminating an image density deficiency and an image defect due to a ghost image.

<1> is a toner conveying roller in which an elastic layer formed by opening a large number of cells on the outer peripheral surface is disposed around the shaft.
When Sc is the sum of the opening areas of the cells that open to the outer peripheral surface of the elastic layer, Sf is the area of the outer peripheral surface of the elastic layer, and D is the average diameter of the cells that open to the outer peripheral surface, Equation (1) The toner transport roller is characterized in that the average skeleton width Wk defined in (1) is 30 to 300 μm.

  <2> is a toner conveying roller according to <1>, wherein the average cell diameter D is 100 to 500 μm.

  <3> is a toner transport roller according to <1> or <2>, wherein the average aperture ratio of the cells is 0.3 to 08.

  According to <1>, since the average skeletal width Wk of the cell defined by the formula (1) is set to 30 to 300 μm, as described in detail later, by increasing the rigidity of the cell wall surface, Activating the supply from the cell and the collection to the cell, thereby forming a good image in that the charge amount of the toner is maintained properly, the image density is appropriate, and no ghost image is generated. can do.

  According to <2>, since the average cell diameter D is configured to be 100 to 500 μm, when the cell is larger than 500 μm, it is possible to prevent the toner holding amount from being reduced, and the cell When the particle size is smaller than 100 μm, it is possible to prevent the toner from being replaced in the cell. This makes it possible to further finely optimize the charge amount of the toner and obtain a better image.

  According to <3>, since the average aperture ratio of the cells is set to 0.3 to 08, this makes it possible to obtain an optimal balance between the cell skeleton width and the cell diameter, and the toner charge amount is further finely optimized. Can be

  Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a side view showing the toner supply roller of this embodiment, FIG. 2 is a developed view of the outer peripheral surface of the elastic layer as seen from the outside in the radial direction, and FIG. 3 is a cross-sectional view showing the vicinity of the outer peripheral surface of the elastic layer. The toner supply roller 10 includes a polyurethane elastic layer 2 formed around the shaft 1. A large number of cells 3 are formed on the outer peripheral surface of the elastic layer 2 and open to the outer peripheral surface without communicating with each other. In addition, a large number of cells 4 that do not open to the surface are formed inside the elastic layer, and many of these cells 4 are directly or via other cells 4 to the cells 3 that open to the outer surface. Communicate.

  FIG. 4 is a schematic view showing the toner supply roller mounted on the image forming apparatus. The toner supply roller 10 rotates against the developing roller 11 while being pressed against each other. The new toner 12 adjusted to have a charge amount is pumped up, and the pumped toner 12 is held on the outer peripheral surface 2a and conveyed to the pressing portion 15 against the developing roller. The pressing portion 15 supplies the new toner 12 to the developing roller 11. At the same time, the old toner 13 is scraped off from the developing roller 11, the scraped toner 13 is held on the outer peripheral surface 2 a and carried to the hopper 14 where the toner 13 is discharged.

  FIG. 5 is a schematic cross-sectional view showing the elastic layer 2 that becomes the pressing portion 15. As shown in the drawing, when the width of the skeleton portion 5 that separates the surface cells 3 of the elastic layer 2 of the toner supply roller 10 from each other is narrow, The skeleton 5 falls down and closes the cell 3, and it becomes impossible to supply new toner to the developing roller 11 and scrape old toner 13 from the developing roller 11 through the surface 2 a, In this case, since the toner on the developing roller 11 is not metabolized, the amount of toner whose charge amount deviates from the expected value (mainly charged) with repeated use increases, resulting in insufficient image density and a ghost image. It becomes.

  Therefore, the feature of the present invention is to set the minimum value of the average width of the skeleton part 5 on the outer peripheral surface of the elastic layer in order to prevent the skeleton part 5 from falling down, and if this width becomes too large, The maximum value of the average width of the skeleton portion 5 is set in order to prevent the larger cells from holding the toner. Specifically, the average skeleton width Wk of the cells is expressed by the formula (1). The Wk is set to 30 to 300 μm.

Here, the expression (1) can be obtained as follows. First, as shown in FIG. 6, the skeleton width Wk is obtained in the case where square cells 21 of the same size having one side a are arranged in a grid pattern with the skeleton width Wk interposed therebetween. Here, the aperture ratio R of the cell 21, that is, Sc, is obtained by using the ratio of the total opening area Sc of the cells open to the outer peripheral surface of the elastic layer to the area Sf of the outer peripheral surface of the elastic layer as shown in Equation (2) There is a relationship.

Here, when the square cell 21 having one side a is replaced with a circular cell 22 having the same area and a diameter D as shown in FIG. 7, the relationship of Expression (3) is established.

  Then, the expression (1) can be obtained by eliminating a from the expressions (1) and (2). Actually, the cells are not uniform in size and shape, but if D is the average diameter of the cells, as is clear from the derivation of the above formula, Wk represented by formula (1) is the average skeleton width. That is, the average value of the thickness of the wall separating the cells can be regarded as a representative parameter.

  Actually, in order to obtain the aperture ratio Sc / Sf and the average diameter D of the cells 3, for example, the elastic layer 3 is formed on the outer peripheral surface 2 a while rotating the toner supply roller 10 around its central axis. An image of the cell portion may be extracted by performing image processing on the developed image of the outer peripheral surface of the elastic layer obtained by irradiating a laser beam from a line light source having substantially the same width as the image and imaging the reflected light. The diameter D can be obtained by calculating the area of each cell 3 from the extracted cell portion image and replacing it with a circle of the same area, and the aperture ratio Sc / Sf can be obtained by calculating the area of the extracted cell. It can be obtained by obtaining the sum of the areas of the cells 3 from the partial image.

  The toner supply roller 10 having the above characteristics can be formed as follows, for example. That is, the shaft 1 is disposed in a cylindrical mold 31 and both ends of the mold 31 are closed with caps 32 to form cavities 33. A polyurethane material is injected into the cavity 33 and foamed and cured in the mold. As a material to be injected, a material obtained by stirring and mixing polyol, isocyanate, water, and a catalyst is used.

  At this time, what is important for forming the elastic layer having the average skeleton width is the repelling condition of the injection material with respect to the mold surface material when injected into the mold, and this determines the average skeleton width. This repellency is determined by the contact angle of the mold surface material with water and the foam stabilizing property of the injection material.

  Forming multiple types of elastic layers with different foam-stabilizing properties of the mold surface material and the injection material to create a toner transport roller, and for each, the average skeleton width of the cell and image evaluation It was. The results and conditions are shown in Table 1. The numerical values of the formulations in Table 1 represent parts by mass with FA703 as 100.

  In addition, all of the toner transport rollers that were created had a diameter of 16 mm, and this toner transport roller was attached to the actual printer, and the image was printed under conditions of low temperature and low humidity of temperature 15 ° C and humidity 10% RH. The evaluation of the image density was performed under the condition of a 100% black image, and the evaluation of the ghost image was performed using a combination of a 100% black image and a 30% black image. The OK / NG determination was made based on the presence or absence of a 100% black image afterimage.

  As is clear from Table 1, when the cell skeleton width is in the range of 30 to 300 μm, good results are shown in terms of image density and ghost image. In addition to setting the surface material of the mold so as to be 40 to 100 °, it is necessary to use a urethane material having high foam regulating properties.

FIG. 3 is a side view illustrating a toner supply roller according to an embodiment of the present invention. FIG. 4 is a developed conceptual view of an elastic layer of a toner supply roller as viewed from the outside in the radial direction. FIG. 4 is a cross-sectional view showing the vicinity of the outer peripheral surface of an elastic layer of a toner supply roller. FIG. 4 is a schematic diagram illustrating a toner supply roller that is attached to the image forming apparatus. 3 is a schematic cross-sectional view showing an elastic layer 2 of a toner supply roller serving as a pressing portion. FIG. It is a schematic diagram of cell arrangement | positioning used for description of the formula which calculates | requires the average frame | skeleton width | variety of a cell. It is another schematic diagram of cell arrangement used for explanation of a formula which asks for the average frame width of a cell. It is sectional drawing which shows the metal mold | die used for forming a toner supply roller.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Shaft 2 Elastic layer 2a The outer peripheral surface of an elastic layer 3 The cell opened to an outer peripheral surface 4 The cell which does not open to the surface 5 Skeletal part 10 Toner supply roller 11 Developing roller 12 New toner 13 Old toner 14 Hopper 15 Press part 21, 22 Outer peripheral surface Opening cell 31 Cylindrical mold 32 Cap 33 Cavity

Claims (3)

In the toner conveying roller in which an elastic layer formed by opening a large number of cells on the outer peripheral surface is arranged around the shaft,
When Sc is the sum of the opening areas of the cells that open to the outer peripheral surface of the elastic layer, Sf is the area of the outer peripheral surface of the elastic layer, and D is the average diameter of the cells that open to the outer peripheral surface, Equation (1) The toner transport roller, wherein the average skeleton width Wk defined in (1) is 30 to 300 μm.

  The toner conveying roller according to claim 1, wherein an average cell diameter D is 100 to 500 μm.   3. The toner conveying roller according to claim 1, wherein the average aperture ratio of the cells is 0.3 to 08.

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