JP2000275955A - Developing roll - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily produce a developing roll, to make it drastically light in weight and to obtain excellent joining strength, durability and high reliability by using a core bar obtained by joining a pipe part and a shaft end which are made of steel excellent in material strength by friction welding. SOLUTION: The pipe part 5 made of steel and the shaft end 6 made of steel constituting the core bar are joined at joining parts 7 by the friction welding. Namely, the end of the pipe part 5 and the shaft end 6 produced to have the same outside diameter are opposed, bought into contact with each other while either of which is rotated, made to generate heat, pressured in an axial direction after stopping the rotation when sufficient frictional heat is generated, and joined in an airtight state. A rubber elastic layer 8 is formed on the outer periphery of the obtained core bar. The strength of the core bar joined by the friction welding is high because both the pipe 5 and the shaft end 6 are made of steel, and the joining parts 7 of both of them are joined by metal-to- metal joining, so that joining strength rises to the rupture strength of the pipe part 5. Since the center part of the core bar except the shaft end 6 is constituted of the hollow pipe part 5a, the developing roll is made light in weight.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing roll used for a copying machine or various printers utilizing electrophotography, and more particularly to a lightweight developing roll.

[0002]

2. Description of the Related Art In a copying machine 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 adhered to the photosensitive drum by a developing roll. To develop the image. After the toner image on the photosensitive drum is transferred onto paper, the toner image is fixed on the paper by heating while applying pressure with a fixing roll.

As shown in FIG. 3, a developing roll used in such an electrophotographic apparatus is generally made of a steel material, and has a low hardness made of silicone rubber or the like on the outer periphery of a metal core 1 having a protruding bearing portion 1a. The rubber elastic layer 2 is used. When the developing roll requires conductivity, the rubber elastic layer 2 contains a conductive agent such as carbon black, and if necessary, a single-layer or multiple-layer coating layer is further provided around the rubber elastic layer 2. May form.
The core 1 of the developing roll is made of SUS as shown in FIG.
A cut metal core prepared by cutting a steel round bar material such as a material or a SUM material, or a material obtained by applying a rust-proof treatment such as electroless nickel plating to this material is generally used.

The specifications such as the size of the developing roll and the thickness of the rubber elastic layer are determined by the developing system and the like to be used. In particular, when the outer diameter of the developing roll itself is large, the system requirements such as improvement of the outer diameter accuracy and the like are required. Therefore, when the thickness of the rubber elastic layer is reduced, the outer diameter of the core metal used increases. When the outer diameter of the metal core is increased as described above, a general developing roll using a metal core cut out from a steel material as described above necessarily results in an increase in weight.

For this reason, 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. In addition, the rotational moment of the rotary increases due to an increase in the weight of the developing roll. 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 and an increase in driving force during sliding.

In the case of a single-color printer or the like, the position of the developing cartridge is often fixed, so that there is no problem with the movement. However, from the viewpoint of the driving force for rotating the developing roller, the developing roller is not used. Needless to say, it is desirable to have a light weight.

[0007]

As described above, a developing roll having a large outer diameter or a developing roll having a thin rubber elastic layer and a large outer diameter of a steel cored bar due to a recent demand for improvement in accuracy. It is desired to reduce the weight.
Therefore, in order to reduce the weight of the developing roll, the material of the cored bar 1 manufactured by shaving shown in FIG. 4 is made of lightweight aluminum, or as shown in FIG. There has been proposed a metal core into which the shaft end 4 having 4a is press-fitted.

However, in the case of the cored bar 1 obtained by cutting aluminum shown in FIG. 4, although weight reduction can be achieved, since the material strength of aluminum is lower than that of a general steel material, the wear resistance of the bearing portion 1a is reduced. Is extremely reduced. In particular, when the mating bearing is an oil-impregnated bearing or a resin bearing, the bearing portion 1a of the cored bar 1 is liable to wear, and ultimately poor rotation of the developing roll, rattling, etc. occur. Expensive bearings such as bearings had to be used for holding.

Further, in the cored bar 1 from which aluminum is cut, residual stress at the time of cutting may adversely affect the developing roll. For example, when a rubber elastic layer is formed of a material that requires high-temperature molding such as silicone rubber, the temperature is generally 200 ° C.
In the secondary vulcanization step of the silicone rubber for about × 4 hours, the stress of the aluminum was relaxed, and problems such as deformation of the obtained developing roll occurred. Therefore, it is necessary to select molding conditions that do not affect the stress relaxation of aluminum, and there is a problem that the width of the rubber elastic layer material that can be selected is narrowed.

Further, in the case of the press-fitting core shown in FIG. 5, since the steel shaft end 4 is press-fitted at both ends of the steel pipe 3, the connection between the shaft end 4 and the pipe 3 is performed. There is a limit to the force, and there is a problem that the shaft end 4 comes off when a strong force is applied, or slippage occurs between the shaft end 4 and the pipe 3. For example, when a rubber elastic layer of silicone rubber is formed on the outer periphery of the press-fitting core, in the above-described silicone rubber secondary vulcanization step, the inside of the pipe portion 3 whose both ends are hermetically sealed by the shaft end portion 4. The pressure increased and the shaft end 4 sometimes came off.

In order to increase the press-fit of the shaft end 4, it is necessary to increase the press-fit allowance d. However, the pipe portion 3 made of a thin steel material is easily deformed, so that a large press-fit allowance d cannot be set. . If the thickness of the pipe portion 3 is increased in order to set the press-fitting allowance d to a large value, the result is that it goes against the originally intended reduction in weight.

The present invention has been made in view of such a conventional situation,
An object of the present invention is to provide a highly reliable developing roll that can be easily manufactured while using a steel core having excellent material strength, and has a reduced weight as a whole.

[0013]

In order to achieve the above object, a developing roll provided by the present invention comprises: a metal core having a steel shaft end portion hermetically friction-welded to both ends of a steel pipe portion; And a rubber elastic layer provided on the outer periphery of the cored bar.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, as shown in FIG. 1, a steel pipe portion 5 and a steel shaft end portion 6 constituting a metal core are joined by a friction welding at a joining portion 7. I have. That is, the end portion of the steel pipe portion 5 previously made to have the same outer diameter and the shaft end portion 6 are opposed to each other, and one of them is brought into contact with each other while rotating, thereby generating sufficient frictional heat at the contact portion. By stopping rotation when it occurs and applying pressure in the axial direction,
The pipe part 5 and the shaft end part 6 are joined in an airtight manner. As shown in FIG. 2, the developing roll of the present invention can be manufactured by forming the rubber elastic layer 8 as usual on the outer periphery of the cored bar thus obtained. 1 and 2 is a bearing.

The core metal joined by friction welding has high strength because the pipe part 5 and the shaft end part 6 are both made of steel, and the joint part 7 of both is joined by metal-to-metal joint. The force basically rises to the breaking strength of the pipe part 5. Therefore, as shown in FIG. 2, when the rubber elastic layer 8 is formed on the outer periphery of the core metal, even if it is heated at about 200 ° C. × 4 hours in the secondary vulcanization step of silicone rubber, for example, Is not deformed, or the shaft end 6 does not fall off due to an increase in the internal pressure of the pipe portion 5 whose ends are joined and hermetically sealed. In addition, even when used for a long time, the shaft end 6 does not come off or slip, and a highly reliable developing roll can be provided.

In addition, since this core has a hollow pipe portion 5 at the center except for the shaft end 6, it is about one-third or less as compared with a conventional steel core manufactured by machining. It is possible to reduce the weight. In particular, since the joint portion 7 between the pipe portion 5 and the shaft end portion 6 is firmly joined by friction welding, the thickness of the pipe portion 5 is reduced to a lower limit at which the breaking strength of the pipe portion 5 satisfies the necessary strength in actual use. Can be made thinner, whereby a further reduction in weight can be achieved.

Also, when comparing the weight with the conventional steel press-fitting core, as shown in FIG.
Therefore, the weight of the shaft end 4 is increased only by the press-fit allowance d, but in the friction welding according to the present invention, the press-fit allowance d is increased.
Is unnecessary, which is more advantageous for weight reduction.

[0018]

Example: Inside diameter 14 mm, outside diameter 16 mm, wall thickness 1 mm,
A pipe portion made of STKM12 material having a length of 230 mm,
A shaft end made of a SUS material having an outer diameter of 16 mm and a bearing having an outer diameter of 8 mm on one side from the center of the shaft was prepared, and each end was fitted to a friction welding device with the center of the shaft coincident.
While rotating the pipe at a rotational speed of 2800 rpm around the axis, the pipe is brought into contact with the fixed shaft end, and the contact portion of both turns red by frictional heat (after about 3.5 seconds). Was stopped, and the two were pressed and abutted in the axial direction at a pressure of 15 kg / mm ² , and were frictionally pressed in an airtight manner to produce a core metal (Sample 1) of the present invention.

As comparative examples, a metal core cut from an aluminum material (sample 2) and a metal core cut from a SUS material (sample 3) so as to have the same shape and dimensions as those of the present invention, and ST of the same dimensions as the pipe section of the present invention example
A core metal (sample 4) was prepared by press-fitting a shaft end made of a SUS material having the same outer diameter as the shaft end of the example of the present invention and having a thickness increased by the press-fitting allowance, into a pipe portion made of KM12 material.

With respect to the obtained cores of the present invention and comparative examples, the weight was measured and the characteristics were evaluated as follows. The results obtained are shown in Table 1 below. That is, the pulling force was evaluated by measuring the force when the shaft end was pulled out from the fixed pipe portion while holding and pulling the bearing at the shaft end. In addition, a circumferential force was applied to the shaft end to the fixed pipe portion, and the torque when the shaft end began to slide was measured and evaluated as the idling torque.

Further, the outer peripheral surface of each cored bar is polished smoothly, inserted into a mold and coated with silicone rubber on its outer periphery, and then subjected to secondary vulcanization at 200 ° C. for 4 hours. As a result, a rubber elastic layer having a thickness of 2 mm was formed. Thereafter, the surface of the rubber elastic layer was polished and finished with a cylindrical polisher to obtain a developing roll of the present invention. The core metal of Sample 4 manufactured by press fitting was:
In the secondary vulcanization step of the silicone rubber (200 ° C. × 4 hours), the shaft end dropped out of the pipe.

Each of the obtained developing rolls is attached to a simple endurance test device, the shafts at both ends are held by resin bearings, one shaft end is connected to a driving device such as a motor, and a rubber belt is attached to the surface of the developing roller. A simple durability test was conducted in which the developing roller was rotated while the brake was applied to the developing roller. This simple durability test was repeated 50 times.
The test was performed for a time, and the state of the bearing portion of the developing roll and the state of the joint portion of the cored bar were evaluated. The results are also shown in Table 1.

[0023]

[Table 1] Weight Pulling force Idling torque sample core metal manufacturing method (g) (kgf) (kgf) Simple durability test 1 Friction welding 118 100 or more 100 or more No problem for up to 50 hours 2 * Al cutting 109 100 Not less than 100 or more than 28 hours with poor rotation 3 * SUS cutting 347 More than 100 or more and no more than 50 hours with no problem 4 * Press-fit 134 12 21 Not tested (Note) Samples marked with * in the table are comparative examples. A simple endurance test was not performed on the core metal of Sample 4 because the shaft end was removed in the secondary vulcanization step of silicone rubber.

[0024]

According to the present invention, since the core metal in which the steel pipe portion and the shaft end portion having excellent material strength are joined by friction welding is used, it can be easily manufactured, and the weight is significantly reduced. And a highly reliable lightweight developing roll excellent in characteristics such as bonding strength and durability can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a main part of a specific example of a core metal used for a developing roll of the present invention.

FIG. 2 is a schematic sectional view showing a main part of a specific example of a developing roll of the present invention.

FIG. 3 is a schematic sectional view showing a main part of a conventional developing roll.

FIG. 4 is a schematic cross-sectional view showing a main part of a machined core used for a conventional developing roll.

FIG. 5 is a schematic sectional view showing a main part of a press-fitting core used for a conventional developing roll.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Core metal 2,8 Rubber elastic layer 3,5 Pipe part 4,6 Shaft end part 4a, 6a Bearing part 7 Joint part

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Tsutomu Saito 3600 Gezu, Kita-gaiyama, Komaki City, Aichi Prefecture Inside Tokai Rubber Industries Co., Ltd. Address Tokai Rubber Industries Co., Ltd. F-term (reference) 2H077 AD06 FA00 FA22 3J103 AA02 AA13 AA24 AA51 AA74 EA06 FA15 FA19 GA02 GA52 GA57 GA58 HA03 HA12 HA32

Claims (1)

[Claims] 1. A developing roll, comprising: a metal core having a steel shaft end frictionally pressure-welded to both ends of a steel pipe portion; and a rubber elastic layer provided on an outer periphery of the metal core. .