JP2004206019A - Developing roll - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lightweight developing roll in which accuracy of position is not lowered and a drive force in sliding is not increased. <P>SOLUTION: A rubber elastic layer 5 is formed on the outer peripheral surface of a core metal 2 where a small diameter part 3a provided on both ends of an aluminum pipe part 3 is force fitted into a recessed part 4b of a steel shaft end part 4, and thus the developing roll 1 is obtained. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a developing roll used in a copying machine or various printers using electrophotography.
[0002]
[Prior art]
2. Description of the Related Art In a copier or the like utilizing electrophotography, an electrostatic latent image is formed by exposing a uniformly charged photosensitive drum, and a toner having an opposite charge is attached to the photosensitive drum by a developing roll to develop an image. . After the toner image on the photosensitive drum is transferred onto a sheet, the toner image is fixed on the sheet by heating while pressing with a fixing roll.
[0003]
As shown in FIG. 3, as a developing roll 6 used in such an electrophotographic apparatus, a steel pipe 8 and a steel shaft 9 constituting a metal core 7 are joined by resistance welding. One having a low hardness rubber elastic layer 10 made of silicone rubber or the like provided on the outer peripheral surface thereof (see Patent Document 1) is used. When the developing roll requires conductivity, a conductive agent such as carbon black is contained in the rubber elastic layer 10 and, if necessary, a single-layer or multiple-layer coating layer is further formed on the outer peripheral surface of the rubber elastic layer 10. May be formed. The core metal 7 of the developing roll 6 is generally used after the pipe portion 8 and the shaft portion 9 are joined by resistance welding, and the entire surface is subjected to rust prevention treatment such as electroless nickel plating. .
[0004]
[Patent Document 1]
JP-A-2002-275956
However, when the outer diameter of the developing roll itself is large, or when the thickness of the rubber elastic layer is reduced due to system requirements such as improvement of the outer diameter accuracy, the outer diameter of the core metal used becomes large. As described above, when the outer diameter of the core increases, the weight of the developing roll using the steel core increases as described above.
[0006]
In a full-color copying machine, a full-color printer, or the like, a system in which four-color developing cartridges each having a developing roll are arranged in a rotary manner around a photosensitive drum and develops necessary colors while rotating is used. The increase increases the rotary moment of the rotary. Also, in a system in which the developing cartridges of four colors slide and approach the photosensitive drum, an increase in the weight of the developing roll causes a decrease in positional accuracy, an increase in driving force during sliding, and the like.
[0007]
[Problems to be solved by the invention]
The present invention has been made in view of such circumstances, and an object of the present invention is to provide a lightweight developing roll that does not cause a decrease in positional accuracy or an increase in driving force during sliding.
[0008]
[Means for Solving the Problems]
In order to solve the above problems, the present invention is based on a metal core press-fitted into a recess provided at the end of a steel shaft at both ends of an aluminum pipe, and a rubber elastic layer provided on the outer peripheral surface of the metal core. The development roll is a gist.
[0009]
Also preferably, the developing roll is provided with small-diameter portions at both ends of the pipe portion.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, embodiments of the present invention will be described in detail with reference to the drawings.
[0011]
As shown in FIG. 2, the developing roll 1 of the present invention comprises a cored bar 2 and a rubber elastic layer 5 provided on the outer peripheral surface thereof. As shown in FIG. 1, the metal core 2 includes an aluminum pipe portion 3 and a shaft end portion 4. The pipe portion 3 is provided with a small diameter portion 3a, a large diameter portion 3b, and a step portion 3c. .
[0012]
The shaft end 4 has a recess 4b at one end and a bearing 4a at the other end. The small diameter portion 3a of the pipe 3 is press-fitted into the recess 4b of the shaft end 4 and integrated. ing. When the small-diameter portion 3a of the pipe portion 3 is press-fitted into the concave portion 4b of the shaft end 4, the distal end of the concave portion 4b is fitted by abutting on the step 3c of the pipe portion.
[0013]
The metal core 2 has a pipe portion 3 made of aluminum and a shaft end portion 4 made of steel. Since the linear expansion coefficient of aluminum is larger than that of steel, the linear expansion coefficient of the pipe portion 3 is smaller than that of the shaft end portion 4. It is larger than the linear expansion coefficient. As a result, when the small diameter portion 3a of the pipe portion 3 is press-fitted into the concave portion 4b of the shaft end portion 4, the degree of adhesion between the outer peripheral surface of the small diameter portion 3a of the pipe portion 3 and the inner peripheral surface of the concave portion 4b of the shaft end portion 4 increases. As a result, the press-in force increases.
[0014]
Moreover, since the pipe portion is made of aluminum, the weight of the core metal can be reduced as compared with the conventional steel core metal. By reducing the weight, the rotational moment of the rotary is reduced, the positional accuracy is improved, and the driving force at the time of sliding is reduced.
[0015]
【Example】
A pipe made of aluminum having an inner diameter of 8 mm, an outer diameter of 12 mm, a thickness of 2 mm, and a length of 300 mm was prepared, and the outer peripheral surface was cut off from both ends by a length of 5 mm to form a small-diameter portion having a thickness of 1 mm. SUS having a bearing portion with an outer diameter of 12 mm, an outer diameter of 6 mm from the shaft center and a length of 20 mm, and a recess having an inner diameter of 10 mm, a wall thickness of 1 mm, and a depth of 5 mm by cutting the inner periphery opposite to the bearing portion. A shaft end made of a material was prepared.
[0016]
The small-diameter portions at both ends of the pipe portion were respectively press-fitted into the recesses at the shaft ends by a press-fitting machine, thereby producing a core metal of the example product.
[0017]
Also, the shaft end is fitted into the fitting part of the pipe part, and the pipe part and the shaft end are mounted in a resistance welding machine, and a current of 15 kA flows while the pipe part and the shaft end are pressed in the axial direction at a pressure of 0.15 mm. In this way, the joint portion between the pipe portion and the shaft end portion was airtightly resistance-welded to produce a core metal as a comparative example product.
[0018]
The weight of each of the cores of the above-mentioned Example product and Comparative example product was measured. As a result, it was 68.4 g for the Example product and 148.8 g for the Comparative product.
[0019]
In addition, after applying and drying a primer to each of the above-mentioned cores, the cores were placed in a mold, and a silicone rubber composition was injected into the outer periphery thereof, followed by vulcanization (150 ° C. × 20 minutes). Next, secondary vulcanization was performed at 200 ° C. for 4 hours to produce a developing roll having a 2 mm thick silicone rubber elastic layer formed on the outer peripheral surface of the cored bar.
[0020]
When the amount of change in run-out was measured for each of the developing rolls of the above-mentioned example product and comparative example product, it was 9 μm for the example product and 21 μm for the comparative example product. The amount of run-out was measured by measuring the run-out at the center of the pipe section before and after heating at 200 ° C. for 4 hours while supporting the bearings at both ends, and showed the amount of change.
[0021]
In addition, even if the above-mentioned example product is subjected to the secondary vulcanization at 200 ° C. for 4 hours, the pressure inside the pipe portion whose both ends are hermetically sealed by the shaft end increases, and the shaft end may come off. Did not.
[0022]
As described above, the developing roll of the present invention is reduced in weight and has high runout accuracy, and the shaft end does not come off even when pressure is applied inside as in the case of secondary vulcanization.
[0023]
【The invention's effect】
The developing roll of the present invention comprises a metal core having both ends of an aluminum pipe portion press-fitted into a concave portion provided at a steel shaft end, and a rubber elastic layer provided on an outer peripheral surface of the metal core. Therefore, the weight is reduced, the runout accuracy is good, and the shaft end does not come off even if pressure is applied inside as in the case of secondary vulcanization.
[Brief description of the drawings]
FIG. 1 is a schematic sectional view showing a main part of a specific example of a core used for a developing roll of the present invention.
FIG. 2 is a schematic sectional view showing a main part of a developing roll of the present invention.
FIG. 3 is a schematic sectional view showing a main part of a conventional developing roll.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Development roll 2 Core metal 3 Pipe part 3a Small diameter part 3b Large diameter part 3c Step part 4 Shaft end part 4a Bearing part 4b Concave part 5 Rubber elastic layer

Claims (2)

A developing roll comprising: a metal core having both ends of an aluminum pipe part press-fit into a concave portion provided at a steel shaft end; and a rubber elastic layer provided on an outer peripheral surface of the metal core. The developing roll according to claim 1, wherein small diameter portions are provided at both ends of the pipe portion.

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