JP2008138735A - Conductive roller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a conductive roller capable of limiting variation of outer diameters of cylindrical members constructed by connecting the resin cylindrical members in a roller shaft direction on core bars. <P>SOLUTION: The conductive roller 10 is composed of a conductive cylindrical member 3, an outer circumference cylinder part 5, and a plurality of ribs 6 supporting the outer circumference cylinder part 5 against the core bar, and at least a part of the rib 6 is cut off on both end parts in length direction of the cylindrical member 3 respectively. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a conductive roller, and more particularly to a conductive roller used as various roller members in an image forming apparatus such as a copying machine or a printer.

  In an image forming apparatus using an electrophotographic system such as a copying machine or a printer, a transfer roller, a developing roller, a toner supply roller, a charging roller, a cleaning roller, an intermediate transfer roller, a belt driving roller, etc. A conductive roller provided with conductivity is used.

Such a conductive roller is formed by forming a conductive coating layer on the outside of the shaft member. In order to reduce the weight of such a conductive roller, the shaft member is made of a resin containing a hollow conductive agent. The thing comprised by the cylindrical member which consists of is proposed (for example, refer patent document 1). And in order to suppress the deformation | transformation by heat contraction of resin, a short-length cylindrical member is shape | molded and this resin cylindrical member is connected on a core metal to the roller axial direction, and it is set as the shaft member of predetermined length. Things have also been proposed.
JP 2004-150610 A

  However, the accuracy required for the outer diameter of the conductive roller is increasing, and there is a demand for reducing the variation in the outer diameter of the shaft member. Even if the length is short, the outer diameter tends to increase at both ends with respect to the central portion in the length direction due to the effect of heat shrinkage. It has been found that large-diameter portions and small-diameter portions appear alternately to deteriorate the outer diameter accuracy.

  This invention is made in view of such a problem, and can suppress the dispersion | variation in the outer diameter of the resin cylindrical member comprised by connecting the resin cylindrical member to the roller axial direction on the metal core. An object is to provide a conductive roller.

<1> comprises a shaft member formed by connecting a plurality of conductive cylindrical members made of resin on the circumference of a core metal in the axial direction, and a coating layer formed around the shaft member. In the conductive roller
The cylindrical member is composed of an outer peripheral cylindrical portion and a plurality of ribs that support the outer peripheral cylindrical portion with respect to the cored bar, and at least a part of the ribs at each of the longitudinal ends of the cylindrical member. It is a conductive roller formed by cutting out the.

  <2> is a conductive roller provided with an inner cylindrical portion connecting the inner sides in the radial direction of the ribs in <1>.

  According to <1>, since at least a part of the rib is cut out at each of both ends in the lengthwise direction of the cylindrical member, in the heat shrinkage after molding, there is no rib at both ends. Inward shrinkage increases with respect to the axial central portion, and in the state where the cylindrical member is fitted to the cored bar and assembled, the central part is the cored bar with respect to both ends without the fitted part. The inner diameter is expanded by fitting with the outer diameter, and the outer diameter is also expanded accordingly, so that the difference between the outer diameter at the central portion in the axial direction and that at both ends can be reduced, and the variation in outer diameter is reduced. can do.

  According to <2>, since the inner cylindrical portion that connects the radial inner sides of the ribs to each other is provided, deformation of the radially inner end of the ribs can be prevented and circumferential uniformity can be improved.

  Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a view showing a conductive roller according to this embodiment. FIG. 1A is a cross-sectional view taken along a central axis of the roller, and FIG. 1B is a cross-sectional view taken along line bb in FIG. FIG. 3 is a cross-sectional view corresponding to a cross section, and the conductive roller 10 is configured by connecting a plurality (in the illustrated case, five) of conductive cylindrical members 3 made of resin on the circumference of the core metal 2 in the axial direction. The shaft member 1 and a coating layer 4 formed around the shaft member 1 are provided. The cylindrical member 3 includes an outer peripheral cylindrical portion 5 and a plurality of outer peripheral cylindrical portions 5 that support the core metal 2. The rib 6 and an inner peripheral cylindrical portion 7 that connects these ribs 6 on the inner side in the radial direction.

  The ribs are arranged in the circumferential direction, for example, at equal intervals, and at least a part of the ribs 5 is cut out to a length shorter than that of the outer cylindrical portion 5 at each of both ends in the longitudinal direction of the cylindrical member 3. ing.

  Thus, by cutting out part of the rib 6 at both ends of the cylindrical member 3, the difference in outer diameter between the both ends and the center of the cylindrical member 3 can be made extremely small. This will be explained below.

  FIG. 3 shows a cylindrical member 93 having a conventional structure. In this case, the rib 96 is formed to have the same length as the outer peripheral cylindrical portion 95, and in this case, the cooling rate between the central portion in the axial direction and both end portions is shown. However, in the present invention, both ends of the tubular member of the rib 6 are formed in a so-called drum shape that is smaller than the outer diameter a at both ends. Since the radial contraction is larger at both ends than the axial central portion, and when the cylindrical member 3 is fitted into the cored bar 2, the outer diameter of the central portion is fitted into this portion. The outer diameter on both sides in the axial direction can be reduced relative to the outer diameter of the central portion for two reasons that this diameter expansion does not occur at both ends. These outer diameter differences can be reduced to suppress variations in outer diameter.

  Here, the notch length of the rib 6 is preferably 10 to 35% of the outer peripheral cylindrical portion 5 when notched over the entire width of the rib 6 in the radial direction, and this is less than 10%. In this case, the outer diameters at both ends in the axial direction cannot be made sufficiently close to the central part, whereas when the notch length exceeds 35% of the outer cylindrical part 5, the outer periphery of the rib 6 The support effect with respect to the cylindrical portion 5 is reduced, and deformation during use is increased.

  FIG. 3 is a cross-sectional view and a side view showing a cylindrical member of a conductive roller according to another embodiment. The cylindrical member 13 includes only an outer peripheral cylindrical portion 15 and a rib 16. The radially inner end of 16 is in direct contact with the core metal 2, thereby supporting the outer diameter cylindrical portion 15.

  Further, the width of the notch at both ends of the cylindrical member of the rib does not need to extend over the entire width in the radial direction. For example, as shown in FIG.

  The resin material used for the cylindrical members 3 and 13 may be any material as long as it has an appropriate strength and can be molded by injection molding or the like, and can be appropriately selected from general-purpose resins and engineering plastics. It is not done. Specifically, as an engineering plastic, for example, polyacetal, polyamide resin (for example, polyamide 6, polyamide 6 · 6, polyamide 12, polyamide 4 · 6, polyamide 6 · 10, polyamide 6 · 12, polyamide 11, polyamide MXD6) (Polyamide obtained from meta-xylenediamine and adipic acid)), polybutylene terephthalate, polyphenylene oxide, polyphenylene ether, polyphenylene sulfide, polyethersulfone, polycarbonate, polyimide, polyamideimide, polyetherimide, polysulfone, polyetheretherketone , Polyethylene terephthalate, polyarylate, liquid crystal polymer, polytetrafluoroethylene, and the like. Examples of the general-purpose resin include polypropylene, acrylonitrile-butadiene-styrene (ABS) resin, polystyrene, and polyethylene. In addition, a melamine resin, a phenol resin, a silicone resin, etc. can also be used. These may be used individually by 1 type and may be used in combination of 2 or more type.

  Among the above, engineering plastics are particularly preferable, and polyacetal, polyamide resin, polybutylene terephthalate, polyphenylene ether, polyphenylene sulfide, polycarbonate and the like are preferable because they are thermoplastic and have excellent moldability and mechanical strength. . In particular, polyamide 6 · 6, polyamide MXD6, polyamide 6 · 12, polybutylene terephthalate, or a mixed resin thereof is preferable. Although there is no problem in using a thermosetting resin, it is preferable to use a thermoplastic resin in consideration of recyclability.

  Various conductive agents can be used as long as they can be uniformly dispersed in the resin material, such as carbon black powder, graphite powder, carbon fiber, aluminum, copper, nickel, etc. A powdered conductive agent such as metal powder, metal oxide powder such as tin oxide, titanium oxide and zinc oxide, and conductive glass powder is preferably used. These may be used individually by 1 type and may be used in combination of 2 or more type. The blending amount of the conductive agent may be selected so as to obtain an appropriate resistance value according to the intended use and situation of the conductive roller, and is not particularly limited. Usually, the material of the hollow member 10 is used. It is preferable to set it as 5-40 weight% with respect to the whole, especially 5-20 weight%.

The volume resistivity of the cylindrical members 3 and 13 may be appropriately set according to the use of the roller as described above, but is usually 1 × 10 ⁰ to 1 × 10 ¹² Ω · cm, preferably 1 ×. 10 ⁰ to 1 × 10 ⁶ Ω · cm, more preferably 1 × 10 ⁰ to 1 × 10 ³ Ω · cm.

  In the material of the cylindrical members 3 and 13, various conductive or non-conductive fibrous materials, whiskers, ferrites, and the like can be blended as needed for the purpose of reinforcement or increase in weight. Examples of the fibrous material include fibers such as carbon fiber and glass fiber, and examples of the whisker include inorganic whiskers such as potassium titanate. These may be used individually by 1 type, and may be used in combination of 2 or more types. These blending amounts can be appropriately selected according to the length and diameter of the fibrous material or whisker to be used, the type of the main resin material, the intended roller strength, etc. 70% by weight, in particular 10-20% by weight.

  Moreover, as the metal core 2, for example, sulfur free-cutting steel, aluminum, stainless steel or the like subjected to nickel, galvanization, or the like can be used.

  Since the shaft member 1 constitutes the core of the conductive roller, the shaft member 1 needs to have sufficient strength to stably exhibit good performance as a roller, and usually has bending strength in accordance with JIS K 7171. It is preferable that it has a strength of 80 MPa or more, particularly 130 MPa or more, so that good performance can be reliably exhibited over a long period of time. In addition, although there is no restriction | limiting in particular about the upper limit of bending strength, Generally it is about 500 Mpa or less.

  Taking the cylindrical member 13 of the embodiment shown in FIG. 3 as an example, the outer diameters at both ends and the center in the length direction were measured. Moreover, the measurement regarding the same item was performed also about the conventional cylindrical member in which the rib 16 in FIG. 3 extended to the same length as the outer periphery cylindrical part 15. FIG. Table 1 shows the results.

  The overall length A of the tubular member 13 of the embodiment is 58.9 mm, the length B of the notch of the rib 13 is 15 mm, the diameter d of the cored bar 2 is 5.5 mm, and the nominal diameter D is 17.4 mm. Met. The outer diameter was measured by measuring the dimensions after assembling the cylindrical member 13 to the cored bar.

  As can be seen from Table 1, the conductive roller of the example was able to greatly reduce the variation of the outer diameter as compared with the conventional roller.

It is sectional drawing which shows the electroconductive roller of embodiment which concerns on this invention. It is a perspective view of the cylindrical member in the conventional electroconductive roller. It is sectional drawing which shows the electroconductive roller of other embodiment. It is sectional drawing which shows the modification of the electroconductive roller of other embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Shaft member 2 Core metal 3 Cylindrical member 4 Coating layer 5 Outer cylindrical member
6 Rib 7 Inner peripheral cylindrical member 10 Conductive roller 13 Cylindrical member 15 Outer peripheral cylindrical member 16, 26 Rib 26A Part of rib

Claims (2)

A conductive roller comprising a shaft member configured by axially connecting a plurality of conductive cylindrical members made of resin on the circumference of a core metal, and a coating layer formed around the shaft member In
The cylindrical member is composed of an outer peripheral cylindrical portion and a plurality of ribs that support the outer peripheral cylindrical portion with respect to the cored bar, and at least a part of the ribs at each of the longitudinal ends of the cylindrical member. Conductive roller made by cutting out.   The conductive roller according to claim 1, wherein an inner cylindrical portion that connects the radially inner sides of the ribs to each other is provided.

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