JP2003167426A - Developing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing device realizing the improvement of toner carrying power and the reduction of the roughness/denseness of a toner thin layer by providing a magnet on the upstream side of a rotating sleeve on a blade, and improved further so that the roughness/denseness of the toner thin layer can be reduced all the more, and an image forming apparatus. <P>SOLUTION: This developing device using magnetic one-component developer has the rotating sleeve 13 including a fixed magnet 15 and a toner layer thickness regulating member 16 regulating the thickness of a toner layer formed on the sleeve 13. The member 16 is equipped with the blade 11 constituted of a plate member made of magnetic substance and the magnet 12 attached to the upstream side in the rotating direction of the sleeve 13 on the blade 11. In the blade 11, a thin edge part 17 is formed at an opposed part to the sleeve 13. <P>COPYRIGHT: (C)2003,JPO

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 forming an electrostatic latent image on an image bearing member using a magnetic one-component developer, and an image forming apparatus having this developing device (for example, a copying machine, Facsimiles, printers, etc.). In the following description, a photoconductor drum will be described as an example of the image carrier, but the present invention is not limited to this, and can be applied to a belt photoconductor and the like.

[0002]

2. Description of the Related Art FIG. 5 is a schematic view showing the periphery of an image forming portion of copying (image forming apparatus).

The image forming portion is a portion for forming a predetermined toner image on the recording paper 115 by the electrophotographic process, and is arranged around the photosensitive drum 301 having photosensitivity in order along the rotation direction thereof. 302, exposure unit 303, developing unit 304, transfer unit 30
5, a charge eliminating unit 307 and a cleaner 306 are provided. The static elimination unit 307 and the cleaner 306 may be arranged in reverse.

The charging unit 302 gives a predetermined potential to the surface of the photosensitive drum 301 by generating corona discharge. The exposure unit 303
Is to selectively attenuate the surface potential of the photosensitive drum 301 by irradiating light corresponding to a desired image to form an electrostatic latent image. The developing unit 304 is
The electrostatic latent image formed on the surface of the photoconductor drum 301 is developed with toner to form a toner image. The transfer unit 305 transfers the toner image formed on the photosensitive drum 301 onto the recording paper 115. The charge eliminating unit 307 is for eliminating the surface charge of the photoconductor drum 301 by the lamp light. The cleaner 306 is composed of a fur brush 316 and a rubber blade 326, and removes toner and its additives remaining on the surface of the photosensitive drum 301. The cleaner 306 in the illustrated example is a fur brush 316.
And a rubber blade 326, but may be a cleaner 306 having only one.

The recording paper 115 to which the toner image has been transferred in the image forming section is heated and pressed by the heating roller 401 and the pressure roller 402 to fix the toner image (fixing section), and then the paper discharge roller ( The sheet is discharged onto the sheet discharge tray (not shown).

FIG. 6 shows the developing unit (developing device) 30.
4 is a cross-sectional view showing No. 4 and is shown together with the photosensitive drum 301. The developing device shown in FIG. 6 is called a conventional example.

A magnetic one-component developer (toner) (not shown) is housed in the developing unit 304. The stirring roller 324 stirs the toner and the toner is transferred to the surface of the photosensitive drum 301. The developing roller 344 is provided.

The developing roller 344 comprises a rotary sleeve 341 covering the roller surface and a roller-shaped magnet 342 provided inside the roller. The magnet 342 is fixed, and the rotary sleeve 341 rotates. Has become. A magnetic blade 394 is provided so as to face the developing roller 344.

As the magnetic pole arrangement of the magnet 342, for example, an S pole (blade pole S ₁ ) is arranged at a position facing the magnetic blade 394, and an N pole (developing pole N ₁ ) is arranged at a position facing the photosensitive drum 301. the developing pole N ₁ of the rotary sleeve rotating direction downstream side to the S pole (S _2), include those further four-pole structure in which the N pole (N ₂₎ on the downstream side.

Next, a developing method using the developing unit 304 will be described.

The toner in the developing unit 304 is charged to a predetermined polarity by friction with the rotating sleeve 341, and the charged toner adheres to the rotating sleeve 341 and is conveyed. The toner layer thickly formed on the rotating sleeve 341 is divided into two at the intermediate position between the rotating sleeve and the blade when passing through the magnetic blade 394, and the toner near the magnetic blade 394 is divided into two parts. 394
The toner that is fixed to the rotary sleeve 341 is attracted to the rotary sleeve 341 by the magnetic attraction force and separated from the magnetic blade 394 toward the photoconductor drum 301.

The thin toner layer that has come to the position facing the photoconductor drum 301 flies to the electrostatic latent image portion formed on the photoconductor drum 301, and forms an image with toner on the surface of the photoconductor drum 301.

However, the rotary sleeve 3 as in the above-mentioned conventional example.
In the method of coating the toner on the surface 41, the toner charge amount is unstable because the toner conveying force is relatively weak, and therefore, when the toner layer is divided into two when passing through the blade 394, the toner is attracted to the rotating sleeve 341 side. However, there is a problem in that the surface of the toner thin layer is disturbed, and the toner thin layer is often dense and dense.

Therefore, as a toner of which the density of the toner thin layer is reduced, the upstream side in the rotating direction of the rotating sleeve of the blade (hereinafter, referred to as
A developing device in which a magnet is attached to a surface (which may be simply referred to as an upstream side) has been proposed (conventional example: JP-A-10-3).
33437 publication). FIG. 7 is a cross-sectional view showing the vicinity of the developing roller in the developing device of this conventional example, and the same components as those in FIG. 6 are designated by the same reference numerals to avoid redundant description.

In this developing device, the magnet 384 on the upstream side of the blade (having the same pole as the magnet in the developing roller at the portion facing the blade:
The toner density on the front side of the blade is improved by the suction effect by the S pole (in the example shown in the figure), and the triboelectric charge amount of the toner is also improved by such an increase in the toner conveyance amount. When the toner layer having a high density and a high charge amount reaches the blade 394, the repulsive magnetic field formed by the magnet 384 on the upstream side of the blade and the fixed magnet S ₁ in the developing roller causes the blade to move. The toner floats up at the position of 394, and the ears of the toner between the blade and the rotating sleeve are broken without being disturbed so much, and as a result, the toner thin layer formed has reduced density.

[0016]

As described above, the developing device of the conventional example having the magnet provided on the upstream side of the blade has a good toner conveying force, and the density of the toner thin layer after the toner layer thickness regulation is reduced. However, since the toner conveying force is too good, the toner may be slightly agglomerated depending on the system conditions such as the peripheral speed of the rotating sleeve and the type of toner. If the aggregated toner causes clogging between the blade and the rotary sleeve, the formation of a good toner thin layer is hindered. Therefore, in order to avoid clogging, the distance between the blade and the rotating sleeve is made relatively large (for example, in the conventional example, 0.
It is necessary to set the thickness to 2 mm, whereas it is necessary to set it to 0.3 mm in the conventional example. As a result, the toner thin layer obtained is relatively thick (for example, in the conventional example, it is 0.1 mm. In the example, the thickness is 0.15 mm), and as the toner thin layer becomes thicker, the density tends to increase. As described above, in the conventional example, there is a limit to making the toner thin layer uniform, and further improvement is desired.

In view of the above, the present invention provides a developing device and an image forming apparatus capable of further reducing the density of the toner thin layer (toner layer after the toner layer thickness is regulated) to make the toner layer substantially uniform. With the goal.

[0018]

A developing device according to the present invention comprises a rotary sleeve containing a fixed magnet, and a toner layer thickness regulating member for regulating the thickness of a toner layer formed on the rotary sleeve. A developing device using a magnetic one-component developer, wherein the toner layer thickness regulating member is a blade composed of a magnetic plate member, and a magnet attached to the blade on the upstream side in the rotating sleeve rotation direction. And a blade having a thin edge portion formed at a portion facing the rotary sleeve.

The above-mentioned blade has a magnetic force due to the above-mentioned magnet attached to its upstream side.
Since the thin edge portion is thin, the magnetic force is concentrated and strong. Since such a strong magnetic force extends from the tip of the blade, that is, the tip of the thin edge portion to the rotating sleeve, the toner layer between the blade and the rotating sleeve is hardly disturbed, and thus a toner thin layer having almost no coarse and dense can be obtained. it can.

Further, since the thin edge portion has a small wall thickness, the distance that the toner on the rotary sleeve passes between the blade and the rotary sleeve becomes short, so that clogging hardly occurs and the distance between the blade and the rotary sleeve is too wide. There is no need to take it. Therefore, it is possible to prevent layer disturbance due to a thick toner thin layer.

Further, in the present invention, in the developing device, the position where the blade faces the rotary sleeve (hereinafter,
(Blade-may be referred to as rotating sleeve facing position)
The rotary sleeve and the blade may be arranged so that the toner is supplied from the lower side, and the rotation of the rotary sleeve may be in a direction upward from the portion to which the toner is supplied.

If the toner supplying portion of the developing device is below the blade-rotating sleeve facing position, it is necessary to lift the toner upward against the gravity, but in the developing device of the present invention, the blade is used. Since the magnetic force is strong at the position facing the rotating sleeve, the toner can be sufficiently lifted by the suction force. If the developing device does not have enough power to lift the toner, it is necessary to position the toner supply position above the position where the blade and the rotating sleeve face each other, and the shape of the developing device and the arrangement of the developing device in the image forming apparatus need to be adjusted. There will be restrictions. However, in the developing device of the present invention, the toner containing portion (housing) does not necessarily have to be provided above the position of the rotary sleeve, and the degree of freedom in shape increases,
In addition, the degree of freedom in the arrangement in the image forming apparatus including this developing device is increased.

Further, in the present invention, the thin edge portion has a thickness of 0.4 to about 0.4 at a tip facing the rotary sleeve.
It is preferably 0.8 mm. In this way, the thickness is 0.8
If it is less than or equal to mm, the above effect can be sufficiently exerted. On the other hand, if it is too thin, the tip of the thin edge portion is likely to wear, which may shorten the service life.
mm or more is preferable.

The thickness of the blade portion other than the thin edge portion is 2 in order to secure the rigidity of the blade.
It is desirable that it is mm or more.

In addition, in the present invention, the tip of the magnet on the side of the rotary sleeve is 0.1 to 0.5 mm from the tip of the thin edge portion in the direction away from the rotary sleeve.
It is preferably in a retracted position.

In this way, the retracted position of the magnet tip from the tip of the thin edge portion (interval W ₂ described later) is set to 0.5 mm or less, and the magnet is moved closer to the rotary sleeve as compared with the conventional example, whereby the blade- The attraction force of the toner to the position facing the rotating sleeve becomes higher than the conventional one. Therefore, similarly to the above, the toner can be sufficiently lifted against gravity, and thus the degree of freedom in the shape of the developing device is increased, and the degree of freedom in disposing the developing device in the image forming apparatus is also increased. However, if the receding position of the tip of the magnet from the tip of the thin edge portion is less than 0.1 mm, clogging of the toner may occur. Therefore, it is preferably 0.1 mm or more as described above.

The gist of the image forming apparatus according to the present invention is that it is provided with the developing device and develops the electrostatic latent image formed on the photoconductor by the developing device.

[0028]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, an example of a copying machine (image forming apparatus) according to an embodiment of the present invention will be described.

FIG. 1 is a schematic diagram showing a schematic configuration of the copying machine. The same components as those in FIG. 5 are designated by the same reference numerals to avoid redundant description.

The copying machine 60 includes a paper feeding section 200 arranged at the bottom of the copying machine main body, an image forming section 300 arranged above the paper feeding section 200, and an image forming section 300 more than the image forming section 300. The fixing unit 400 disposed on the discharge side and the fixing unit 4
00, and an image reading unit 500 provided above the main body of the copying machine. The paper feeding unit 200, the image forming unit 300, the fixing unit 400, and the ejection unit. Paper transport unit 100 connecting the units 600
Is equipped with.

The image forming unit 300 forms a predetermined toner image on a sheet by the electrophotographic process as described above, and the photosensitive drum 301 rotatably supported.
Around the photosensitive drum 301 along the rotation direction (arrow A), the charging unit 302 and the exposure unit 3
03, developing unit (developing device) 10, transfer unit 3
05, the cleaner 306 is provided. The developing unit 10 develops the electrostatic latent image with toner to form a toner image on the surface of the photosensitive drum 301.

The fixing unit 400 is the image forming unit 30.
No. 0, which is arranged on the downstream side in the paper conveyance direction, and on which the toner image is transferred in the image forming unit 300 is nipped by a pair of rollers (a heating roller 401 and a pressure roller 402) and heated, and the toner is transferred onto the paper. It fixes the image.

The image reading section 500 irradiates a document placed on the contact glass with light from an exposure lamp and guides the reflected light to a photoelectric conversion section via a reflecting mirror.
The image information of the original is read.

The paper feeding section 200 comprises a plurality of paper feeding cassettes 201, 202 and 221. The paper feed cassette 221 is a bypass tray for replenishing paper from the side of the copying machine, and can be closed by a lid 222.

Each of the paper feed cassettes 201, 202,
A sheet conveyance path 110 is connected to the sheet 221, and the sheet conveyance path 110 faces the image forming unit 300, and further, the fixing unit 40.
It goes toward the discharge part 600 through 0. Note that the paper transport path 110 constitutes the paper transport unit 100. Further, the paper for which copying has been completed is discharged onto the discharge tray 610 from the discharge roller 605 of the discharge unit 600.

As can be seen from FIG. 1, the copying machine 60 is a vertical conveyance type, and the entire copying machine is compact, and as the developing unit 10, the developing roller 14 is located above,
The toner storage portion 354 is shaped to be located below the developing roller 14.

Next, a developing unit (developing device) 10 according to an embodiment of the present invention used in the above copying machine will be described.

FIG. 2 is a sectional view showing the developing unit 10. The toner storage portion 354 of the developing unit 10
Contains a magnetic one-component developer (toner) (not shown), and two stirring rollers 31 for stirring the toner.
4,324 are provided. Further, the developing roller 14 for transferring the toner to the surface of the photosensitive drum 301 is provided above the toner storage portion 354.

The developing roller 14 is a cylindrical rotary sleeve 13 made of a non-magnetic material such as aluminum.
And a fixed magnet 15 contained in the rotary sleeve 13, and the rotary sleeve 13 rotates around the fixed magnet 15 with the position of the magnet 15 fixed. Magnet 1 in this rotating sleeve 13
5 is the same as the conventional _one , the S pole (blade pole S ₁ ) is provided at a position facing the toner layer thickness regulating member 16 described later, and the photosensitive drum 3
N pole (developing pole N ₁₎ arranged in 01 positions opposed to, S-pole (S ₂₎ in the rotary sleeve rotating direction downstream side of the developing pole N _1, further N-pole on the downstream side (N ₂₎ is arranged Has been done.

The toner layer thickness regulating member 16 is provided so as to face the rotary sleeve 13 (developing roller 14), and the toner layer thickness regulating member 16 is composed of a blade 11 and a magnet 12, and the magnet 12 of the blade 11 is provided. The rotary sleeve is mounted on the upstream side in the rotation direction.

FIG. 3A is a partially enlarged sectional view showing the developing roller 14 and the toner layer thickness regulating member 16.
(B) is a sectional view in which the portion between the blade and the rotating sleeve is further enlarged. The same components as those in FIG. 2 are designated by the same reference numerals to avoid redundant description.

The blade 11 is a magnetic plate member (for example, magnetic stainless steel, specifically SUS340 or SU).
S430 etc., and its rotating sleeve 1
A thin edge portion 17 is formed at a portion facing the edge 3. The thin edge portion 17 is arranged so as to extend parallel to the rotary sleeve 13 with a predetermined distance W ₁ (for example, 0.2 to 0.4 mm) from the rotary sleeve 13. The thickness T ₂ at the tip 17a of said thin edges 17 0.4 is a range of, for example, 0.4 mm (preferred thickness T ₂
0.8 mm), and the protruding length L ₁ of the thin edge portion 17 is, for example, 0.5 mm (a preferable range of the protruding length L ₁ is 0.3 to 0.8 mm). The thickness T ₃ of the trunk portion 18 of the blade 11 is, for example, 2 mm, and holds the position of the thin edge portion 17 firmly without bending. The transition portion 19 from the trunk portion 18 to the thin edge portion 17 is gradually inclined so as to be inclined.

The magnet 12 has a thickness T ₄ of, for example, 2 mm and a length L ₂ of, for example, 10 mm, and the side facing the developing roller 14 is the same as the magnetic pole (S ₁ ) of the blade 15 of the developing roller magnet 15. The south pole is the north pole on the opposite side. The end of the magnet 12 facing the developing roller 14 (the magnet 1
2a is located farther from the developing roller 14 than the tip 17a of the thin edge portion 17 and the gap W ₂ between the thin edge portion 17a and the opposite end 12a of the magnet 12 is, for example, 0. 0.3 mm (preferably W ₂ is 0.1 to 0.5 mm).

Next, the operation will be described.

In the developing unit 10, at the position facing the toner layer thickness regulating member 16-rotating sleeve 13 (the position indicated by the arrow B in FIG. 2), S _{1 of the} fixed magnet 15 is changed.
A strong magnetic field is formed by the pole and the S pole at the tip of the magnet 12, and a strong N-polarity that repels this magnetic force is formed at the thin edge portion 17 of the blade 11 (FIG. 4: toner layer thickness). S of regulating member 16 and developing roller 14
Diagram for explaining the magnetic field of _one pole part).

The toner charged to a predetermined polarity by friction with the rotating sleeve 13 is S _{1 of the} fixed magnet 15.
The toner layer thickness regulating member 16-rotating sleeve 1 is strongly attracted by the pole and the S pole at the tip of the magnet 12 and rises.
3 toward the facing position (the position indicated by the arrow B in FIG. 2).
Then, this toner is conveyed while being attached to the rotary sleeve 13, and the blade 1 in the toner layer thickness regulating member 16 is conveyed.
The thin edge portion 17 of No. 1 regulates the layer thickness to reduce the thickness. At this time, since the strong magnetic field is formed between the thin edge portion 17 and the rotary sleeve 13 as described above, the toner is transferred between the thin edge portion 17 and the rotary sleeve 13 in a substantially uniform state in which the density is extremely reduced. When the toner passes through the thin edge portion 17, the toner spikes are divided into two in a substantially uniform state, and a thin toner layer is formed on the rotary sleeve 13. After that, the thin toner layer on the rotary sleeve 13 moves toward the photoconductor drum 301.

As described above, in this embodiment, the toner layer
The magnet 12 of the thickness regulating member 16 exerts a strong attractive force.
In addition to exhibiting an excellent toner transport effect, the thin edge portion 1
Due to the strong N-polarity in 7, the toner thin layer disorder is solved.
Can be erased to form a nearly uniform thin toner layer
It In addition, since the thin edge portion 17 is thin,
It is difficult to cause clogging between the edge portion 17 and the rotary sleeve 13,
Therefore, the distance (W ₁) Does not need to be wide. Well
Stable image formation can be achieved because it is less likely to cause clogging.
Wear.

For the purpose of simply strengthening the magnetic force between the blade rotating sleeves, a method of adopting a strong magnet as the magnet inside the rotating sleeve or using a strong magnet for the blade upstream side is considered. However,
In these methods, the strong magnet is expensive, so that the cost is increased, and the density of the toner thin layer cannot be reduced as described above.

As described above, the developing device (developing unit) and the image forming apparatus according to the present invention have been specifically described with reference to the drawings showing examples, but the present invention is not limited to the illustrated examples. However, it is also possible to make appropriate modifications and implement them within a range that is compatible with the above-mentioned meaning, and all of them are included in the technical scope of the present invention.

For example, in the above-described embodiment, the transition portion 19 from the trunk portion 18 to the thin edge portion 17 of the blade 11 is inclined, but the present invention is not limited to this, and the transition portion whose thickness changes stepwise is shown. May be Further, the thin edge portion 17 may be directly connected to the trunk portion 18 without providing the transition portion 19.

[0051]

According to the developing device and the image forming apparatus of the present invention, it is possible to obtain a toner thin layer after the toner layer thickness is regulated, which is substantially uniform and has almost no coarse and fine density. Moreover, clogging between the toner layer thickness regulating member and the rotating sleeve is unlikely to occur.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a schematic configuration of an example of a copying machine (image forming apparatus) according to an embodiment of the present invention.

FIG. 2 is a sectional view showing a developing unit (developing device) according to an embodiment of the present invention.

FIG. 3A is an enlarged cross-sectional view showing a portion of a developing roller and a toner layer thickness regulating member, and FIG. 3B is a further enlarged cross-sectional view of a portion between a blade and a rotary sleeve.

FIG. 4 is a diagram for explaining a magnetic field of a toner layer thickness regulating member and a S ₁ pole portion of a rotating sleeve.

FIG. 5 is a schematic diagram showing the periphery of an image forming unit for copying or the like.

FIG. 6 is a sectional view showing a conventional developing unit (developing device).

FIG. 7 is a sectional view showing the vicinity of a developing roller in a conventional developing device.

[Explanation of symbols]

10 Development unit (developing device) 11 blade 12 magnets 13 rotating sleeve 14 Developing roller 15 fixed magnet 16 Toner layer thickness regulating member 17 Thin Edge 17a Edge of thin edge 18 executives 19 Transition 314,324 Stir roller 354 toner storage part

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Okubo             Kyocera 1-22-28 Tamatsukuri, Chuo-ku, Osaka-shi             Within Mita Co., Ltd. (72) Inventor Masatake Hayashi             Kyocera 1-22-28 Tamatsukuri, Chuo-ku, Osaka-shi             Within Mita Co., Ltd. (72) Inventor Takusaku White             Kyocera 1-22-28 Tamatsukuri, Chuo-ku, Osaka-shi             Within Mita Co., Ltd. (72) Inventor Yoshiyuki Asakawa             3-17-18 Nakamichi, Tosei-ku, Osaka             Le 6th floor Kyocera Co., Ltd. F-term (reference) 2H031 AC08 AC31 AC34 AD16 BA01                 2H077 AD06 AD13 AD16 AD18 AD24                       EA13 FA19

Claims (5)

[Claims] 1. A developing device using a magnetic one-component developer, comprising: a rotary sleeve containing a fixed magnet; and a toner layer thickness regulating member for regulating the thickness of a toner layer formed on the rotary sleeve. The toner layer thickness regulating member includes a blade formed of a magnetic plate-shaped member and a magnet attached to an upstream side of the blade in the rotation direction of the rotating sleeve, and the blade faces the rotating sleeve. A developing device, characterized in that a thin edge portion is formed in the portion. 2. In the developing device, the rotary sleeve and the blade are arranged so that toner is supplied from a lower side than a position where the blade faces the rotary sleeve, and the rotation of the rotary sleeve is The developing device according to claim 1, wherein the developing device is directed upward from a portion to which toner is supplied. 3. The developing device according to claim 1, wherein the thin edge portion has a thickness of 0.4 to 0.8 mm at a tip facing the rotary sleeve. 4. The tip of the magnet on the side of the rotary sleeve is at a position retracted by 0.1 to 0.5 mm from the tip of the thin edge portion in a direction away from the rotary sleeve. The developing device according to 1. 5. An image forming apparatus comprising the developing device according to claim 1, wherein the developing device develops an electrostatic latent image formed on a photoconductor. .