JPH09230692A - Developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a developing device easily and inexpensively by forming a cylindrical developing roll by means of mutually connecting both ends of a stainless steel plate of uniform thickness together. SOLUTION: A developing roll 20 is formed of an electric resistance welded pipe 31 made by rounding a stainless steel made band plate 30 in its width direction and welding them together. In other words, the electric resistance welded pipe 31 is formed by rounding the band plate 30, which is coiled in a reel shape, in its width direction as it is drawn out and connecting both side ends facing each other by welding after which the same welded pipe 31 is cut a specific length. In rounding the band plate 30, a die body, through which the band plate 30 is inserted, is used and the band plate 30 drawn out from the die body in a cylindrical shape is immediately welded so that the electric resistance welded pipe 31 is formed in the complete roundness. The developing roll 20 cut from seam welded pipe 31 is ground on its outside circumferential surface by a centerless grinder and the outside circumferential surface is finished to a specific roughness.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device for developing an electrostatic latent image formed on an image bearing member such as a photoconductor drum in an image forming device such as a copying machine or a laser printer, and more particularly to a developing device. The present invention relates to an improvement for improving the rotation accuracy of the developing roll that rotates adjacent to the image carrier.

[0002]

2. Description of the Related Art Conventionally, as a developing device for developing an electrostatic latent image formed on an image bearing member such as a photosensitive drum, a developing roller which rotates while holding a predetermined developing gap with the image bearing member. There is known a so-called non-contact type developing device which holds a developer by a magnetic force and / or an electrostatic force, and causes the developer to fly toward the image carrier to develop the electrostatic latent image.

In such a conventional developing device, the developing roll is formed in a cylindrical shape capable of accommodating a magnet roll therein, and is usually formed by drawing a relatively soft metal material such as aluminum. . When the developing roll is rotatably supported on the housing of the developing device, a pair of flanges having a rotating shaft are fitted to the openings of both ends of the developing roll, and the rotating shaft is supported on the device housing via bearings. Was there.

[0004]

In the above-mentioned non-contact type developing device, the size of the developing gap between the image carrier and the developing roll has a great influence on the developing characteristics of the electrostatic latent image. Therefore, it is desirable that the development gap is always constant. However, when the rotation axis of the developing roll is eccentric, it is difficult to keep the developing gap constant because the distance between the outer peripheral surface of the developing roll and the rotation axis is not constant.

In this respect, since the conventional developing roll is formed by the drawing process, it is difficult to form the wall thickness uniformly in the circumferential direction only by the drawing process. There was no choice but to perform the centering work of the developing roll before fitting it into the openings at both ends of the developing roll. That is, the outer peripheral surface of the developing roller after the drawing processing was uniformly ground by a centerless grinder, and further the inner peripheral surface of both ends of the developing roller into which the above flange was fitted was also ground. Only after that, the flange could not be fitted into the openings on both ends of the developing roll, and the processing was very troublesome.

On the other hand, when the developing roll is manufactured by the drawing process, a relatively soft metal material such as aluminum must be selected as the material of the developing roll from the viewpoint of the ease of the drawing process and the processing cost. However, it is severe that these metal materials are required to have mechanical strength, and the developing roll can be rotated with respect to the apparatus housing only through the above-mentioned flange formed of another material such as stainless steel. It was difficult to mount a gear that supports and transmits the rotational power from the motor.

Further, in recent years, for the purpose of surely replacing the developer held on the developing roll, a scraper made of stainless steel is brought into contact with the developing roll, and the developer passing through the position facing the image carrier is removed. A developing device for completely peeling from the developing roll has also been proposed (Japanese Patent Application No. 7-2712).
No. 70), a developing roller made of a metal material such as aluminum causes galling on the surface due to contact with a scraper, and the developing roller becomes unusable.

The present invention has been made in view of the above problems, and an object of the present invention is to easily and inexpensively manufacture a developing roll having good rotation accuracy.
Moreover, it is an object of the present invention to provide a developing device capable of significantly simplifying the support structure of the developing roll with respect to the device housing.

[0009]

In order to achieve the above object, the developing device of the present invention has a cylindrical shape which is rotatably supported with respect to the device housing and rotates while holding the developer on its peripheral surface. A developing roll and a developer supply chamber that is provided adjacent to the developing roll and supplies the developer to the developing roll are provided, and the developer held by the developing roll is formed on the image carrier. In the developing device for developing the electrostatic latent image, the developing roll is formed by joining both ends of stainless steel plates having a uniform thickness.

According to the developing device of the present invention having such a technical means, the developing roll is formed by joining both ends of stainless steel plates having a uniform thickness to each other by a method such as welding. Is always uniform in the circumferential direction, even if a flange having a rotating shaft is fitted to the openings at both ends of the developing roll without grinding the inner peripheral surface of the developing roll, the developing of the rotating shaft is not performed. The eccentricity with respect to the roll can be eliminated, and the rotation accuracy of the developing roll can be maintained while omitting the processing labor.

Further, since the developing roll is formed by rolling a stainless steel plate having excellent mechanical strength, it is possible to directly fit a bearing on the outer peripheral surface of the developing roll and support it on the apparatus housing. With this configuration, compared with the case of supporting the device housing through the flanges fitted to the openings at both ends, the accuracy of rotation of the developing roll is further improved because there is no accumulated accuracy error as a part of the flange. Can be achieved. In addition, since the flanges at both ends of the developing roll, which were conventionally required, can be omitted,
It is possible to simplify the assembly of the developing device and reduce the cost.

Further, for the developing roller of the present invention having excellent mechanical strength, it is possible to directly fit a power transmission member for transmitting the rotational power of the motor to the outer peripheral surface at one end thereof. Also, the angular velocity error due to the misalignment of the flange can be reduced, the rotation accuracy of the developing roll can be improved, and the assembling of the developing device can be simplified and the cost can be reduced. Here, the power transmission member may be a gear, a pulley, or the like.

[0013]

DETAILED DESCRIPTION OF THE INVENTION The developing device of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 shows an outline of a laser beam printer configured by using the developing device of the present invention. In the figure, reference numeral 1 is a photosensitive drum as an image bearing member, reference numeral 2 is a charging roll for charging the photosensitive drum 1 to a predetermined bright potential, and an arrow 3 is irradiated by a laser beam scanner (not shown). The above photoconductor drum 1
A laser beam for writing an electrostatic latent image on the photosensitive drum 1, a developing device 4 for developing the electrostatic latent image formed on the photosensitive drum 1 with toner (developer), and a reference numeral 5 for the photosensitive drum 1. A sheet supply tray for feeding the recording sheet 6 at a predetermined timing synchronized with the writing timing of the electrostatic latent image, reference numeral 7 denotes a transfer roll for electrostatically transferring the toner image developed on the photosensitive drum 1 to the recording sheet 6, Reference numeral 10 is a cleaner provided with a cleaning blade 9 that comes into contact with the surface of the photosensitive drum 1 on which the transfer of the toner image is completed, and a reference numeral 10
Is a fixing device for fixing the toner image transferred onto the recording sheet 6 to the recording sheet 6.

Further, in this laser beam printer, the photosensitive drum 1, the charging roll 2, the developing device 4 and the cleaner 8 constitute one cartridge unit, and at the time point when printing on a specified number of recording sheets is completed, The entire cartridge unit is replaced. Therefore, by replacing the cartridge unit, it is possible to replace the deteriorated photosensitive drum, replenish toner, and collect the waste toner collected by the cleaner at one time.

Under such a structure, a toner image corresponding to image information is formed on the photosensitive drum 1 through the charging process by the charging roll 2, the exposure process by the laser beam 3 and the developing process by the developing device 4. The toner image is transferred to the recording sheet 6 at the position where the photosensitive drum 1 and the transfer roll face each other. The recording sheet on which the toner image has been transferred is discharged to a sheet discharge tray (not shown) via a fixing device, while the photosensitive drum 1 after the transfer process is cleaned by the cleaning blade to remove residual toner, paper dust, and other adhering substances. Are removed.

FIG. 2 shows a specific structure of the cartridge unit. In the figure, reference numeral 11 is a cleaner housing that holds the photosensitive drum 1 rotatably. The cleaning blade 9 is fixed to the cleaner housing 11, and the cleaning blade 9 removes the surface of the photosensitive drum 1 from the surface. Adhered substances such as collected waste toner and paper powder are accumulated inside the device. The charging roll 2 is also rotatably held in the cleaner housing 11, and the charging roll 2 is pressed against the photosensitive drum 1 by a spring 12. Therefore, when the photoconductor drum 1 rotates, the charging roll 2 also rotates following the rotation of the photoconductor drum 1.

Further, the developing device 4 is swingably connected to the cleaner housing 11 via a pin 13, and a spring 14 interposed between the cleaner housing 11 and the developing device 4 is provided. The developing device is biased in one direction. As a result, the developing gap between the developing roller 20 provided in the developing device 4 and the photosensitive drum 1 held in the cleaner housing 11 is maintained.

On the other hand, the developing device 4 has a cylindrical developing roll 20 which rotates while holding a thin layer of toner on its peripheral surface, and a toner supply chamber 21 which supplies toner to the developing roll 20. A layer forming blade 22 for forming a thin layer of toner having a predetermined thickness from the toner supply chamber 21 on the developing roll 20, a peeling blade 23 for peeling off the thin toner layer from the peripheral surface of the developing roll 20, and the toner supply described above. It is composed of an agitator (stirring means) 24 that rotates in the chamber 21 to stir the toner in the chamber.

Here, a magnetic toner is used as the toner, and the toner is held on its peripheral surface by the magnetic force generated by the developing roller 20. That is, the developing roll 20 has a built-in magnet roll (not shown), and the toner in the toner supply chamber 21 is attracted to the peripheral surface of the developing roll 20 by the magnetic force of the magnet roll.

Further, the agitator 24 rotating in the toner supply chamber 21 not only prevents the blocking of the toner in the chamber but also serves to send the toner toward the developing roll 20, so that the latter function is more effective. In order to demonstrate it, PET is attached to the tip of the agitator 24.
A flexible film 25 such as is attached. The flexible film 25 rubs the inner wall of the toner supply chamber 21 as the agitator 24 rotates, and the toner existing in the corners of the toner supply chamber 21 is also sent to the developing roll without waste. It should be noted that the broken line circle in the figure indicates the range reached by the advanced flexible film 25, in other words, it indicates the stirring range of the toner by the agitator 24.

Further, one end of the layer forming blade 22 is pressed against the developing roll 20 with a predetermined pressing force, and the other end is fixed to the mounting block 28, so that the toner attached to the developing roll 20 is rubbed by the magnetic force. The layer is thinned to a predetermined layer thickness while being charged. Between the layer forming blade 22 and the mounting block 28, a synthetic resin tube 26 having a substantially cylindrical cross section is sandwiched in parallel with the developing roll 20, and the tube 26 is directed toward the developing roll 20. 22 is pressed uniformly from the back side.

Then, as described above, the developing roll 20
The toner thinned on the peripheral surface of the toner is carried out to the developing area facing the photoconductor drum 1 as the developing roll 20 rotates, and a part of the toner adheres to the photoconductor drum 1 to form an electrostatic latent image. To develop. On the other hand, the toner left on the developing roll 20 without adhering to the photosensitive drum 1 is collected into the developing device 4 as the developing roll 20 rotates, and is peeled off from the developing roll by the peeling blade 23. .

Next, the details of the developing roll 20 will be described. The developing roll 20 in this embodiment is formed of a so-called electric resistance welded tube obtained by rolling a stainless steel strip plate along its width direction and welding it. Specifically, as shown in FIG. 3, the strip plate 30 wound in a reel shape is rolled out sequentially while being rounded along the width direction thereof, and opposite ends of the strip plate 30 are joined by welding to form an electric resistance welded pipe. 31 is formed and the electric resistance welded pipe 31 is cut into a predetermined length. Although not shown in the figure, when rolling the strip plate 30, a mold body through which the strip plate 30 is inserted is used, and a strip plate formed into a cylindrical shape from the mold body is used. Immediately welding was performed so that the electric resistance welded pipe 31 was formed with a predetermined roundness. Further, the developing roll 20 cut out from the electric resistance welded pipe 31 has its outer peripheral surface ground by a centerless grinding machine, and the outer peripheral surface is finished to have a predetermined surface roughness. The width of the strip plate 30 is appropriately changed according to the required diameter of the developing roll 20,
In this embodiment, a developing roll having a grinding diameter of 75 mm was manufactured using a strip plate having a width of 47 mm and a thickness of 0.5 mm.

As shown in FIGS. 4 and 5, the cylindrical developing roller 20 thus formed has a flange 3 having a rotating shaft 32 on the inner peripheral surface 20a at the open end thereof.
3 is fitted and is rotatably supported by a housing 35 of the developing device 4 via a bearing 34 fitted to the rotary shaft 32. A gear 36 is fitted to the rotary shaft 32, and the rotational driving force of a motor (not shown) is transmitted to the gear 36.

Since the developing roll 20 of this embodiment is formed by rolling the strip plate 30 having a predetermined thickness as described above, the wall thickness thereof is uniform and the perfect circle of the electric resistance welded pipe 31 formed from the strip plate. If the degree is high, it is not necessary to perform centering work on the inner peripheral surface of the developing roll. Therefore, the flange 33
In fitting the developing roll with the developing roll, the grinding process of the inner peripheral surface of the developing roll, which has been conventionally required, can be omitted, and the developing roll 20 formed by cutting the electric resistance welded pipe 31 is formed.
The flange can be fitted immediately to the open end of the.

According to the verification by the inventor of the present application, when the flange is directly fitted to the opening end of the developing roll formed by drawing, the developing gap between the developing roll and the photosensitive drum is about 0.1 mm. When the inner peripheral surface of the developing roll is ground and then the flange is fitted, the developing gap varies by 0.05 mm.
It was suppressed to the extent. On the other hand, in the developing roller 20 of the present embodiment, even when the flange is fitted without grinding the inner peripheral surface, the variation in the developing gap is reduced to 0.
It was revealed that the rotation accuracy can be suppressed to about 05 mm, and the rotation accuracy similar to that of the conventional developing roll can be maintained even if the centering work is omitted.

On the other hand, since the developing roll 20 of this embodiment formed by rolling the stainless steel strip 30 is superior in mechanical strength to the conventional aluminum developing roll, the bearing is directly fitted to the outer peripheral surface thereof. Even if they are combined with each other, the inconvenience such as galling does not occur, and it is possible to support them in the housing 35 of the developing device 4 with the flange 33 omitted. That is, as shown in FIGS. 6 and 7, the bearing 37 and the gear 38 are directly fitted to the outer peripheral surface of the developing roll 20, and the developing roll 20 is supported by the housing 35 via the bearing 37.

When fitting the gear 38 to the developing roll 20, it is necessary to prevent the gear 38 from rotating with respect to the developing roll 20, but the developing roll 20 has sufficient mechanical strength as described above. Since it is made of stainless steel, the notch 39 is formed at the end of the developing roller 20, and the gear can be prevented from rotating using this notch. Alternatively, the end portion of the developing roll may be deformed into a D-shaped cross section by plastic working, and a gear may be fitted to the plastically deformed portion to prevent rotation.

If the developing roll is directly supported on the apparatus housing 35 without the flange 33, the eccentricity of the developing roll caused by the fitting error between the developing roll and the flange can be eliminated. Therefore, the rotation accuracy of the developing roll can be further improved.

In addition, in order to achieve the original function of the developing roll that holds a uniform thin toner layer, the outer peripheral surface of the developing roll is ground with a predetermined accuracy in the first place, so a bearing is fitted to the outer peripheral surface. No special processing steps occur in the process. Therefore, if the bearing is fitted to the outer peripheral surface of the developing roller of this embodiment,
The developing device can be assembled very easily, and the production cost can be greatly reduced.

According to the verification by the inventor of the present application, when the bearing is fitted to the outer peripheral surface of the developing roller 20 of this embodiment formed from the electric resistance welded tube 31 and the developing roller is supported, the fluctuation of the developing gap is caused. It can be suppressed to about 0.03 mm, and a better result can be obtained as compared with the case where the flange is fitted to the inner peripheral surface of the developing roller 20 of this embodiment.

[0032]

As described above, according to the developing device of the present invention, both ends of stainless steel plates having a uniform thickness are joined to each other to form a cylindrical developing roll.
In order to rotatably support the developing roll with respect to the apparatus housing, the processing step of the developing roll, which has been indispensable in the past, can be omitted, and the developing device can be easily and inexpensively manufactured.

Further, while omitting the processing step of the developing roll as described above, the fluctuation of the developing gap between the developing roll and the image carrier can be suppressed to the same level as the conventional one or smaller than the conventional one. It is possible to develop the electrostatic latent image formed on the carrier with high quality.

[Brief description of drawings]

FIG. 1 is a schematic view showing a laser beam printer in which a developing device of the present invention is used.

FIG. 2 is a sectional view showing a cartridge unit in which the developing device of the present invention is incorporated.

FIG. 3 is a diagram showing an outline of a method of manufacturing a developing roll according to the present invention.

FIG. 4 is a diagram showing a relationship between a developing roll according to the present invention and a flange fitted to an inner peripheral surface of an end portion thereof.

5 is a diagram showing a mounting state of the developing roll shown in FIG. 4 to a housing.

FIG. 6 is a diagram showing a relationship between a developing roll according to the present invention and bearings and gears fitted to the outer peripheral surface thereof.

FIG. 7 is a diagram showing a mounting state of the developing roll shown in FIG. 6 on a housing.

[Explanation of symbols]

30 ... Strip plate (stainless steel plate), 31 ... ERW tube, 20 ... Development roll

Claims (3)

[Claims] 1. A cylindrical developing roll, which is rotatably supported with respect to an apparatus housing and rotates while holding a developer on its peripheral surface, and a cylindrical developing roll provided adjacent to the developing roll. In a developing device for developing an electrostatic latent image formed on an image bearing member with the developer held by the developing roll, the developing roll has a uniform thickness. A developing device characterized in that both ends of a stainless steel plate are joined to each other. 2. The developing device according to claim 1, wherein the developing roll is supported by the device housing via a bearing fitted directly to an outer peripheral surface of the developing roll. 3. The developing device according to claim 1, wherein a power transmission member for transmitting rotational power to the developing roll is directly fitted to an outer peripheral surface of one end of the developing roll. And developing device.