JPH09146356A - Developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To hold magnetic powder falling from a developer reservation part in the developer reservation part again and to prevent the irregularity of image density from occurring in the axial direction of a developing sleeve by extending the inner surface of a bottom wall to a toner hopper side beyond than the lower end of the side wall of a doctor front hood and inclining it low over the developing sleeve side. SOLUTION: The inner surface 10 of the bottom wall of a toner reservation part B is extended to a toner housing part side further than the lower end of the side wall 7a of the doctor front hood 7 on the toner housing part side and inclined to be low from the toner housing part side to the developing sleeve 4 side. By such constitution, carrier falling from the developer reservation part A through the aperture of the doctor front hood is received by the inner surface of the bottom wall, moved to the developing sleeve 4 side on the inner periphery of the bottom wall, held by magnetic force on the developing sleeve and supplied to the developer reservation part again.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device used in an image forming apparatus such as a copying machine, a facsimile, a printer, and more specifically, it is formed on an image carrier by using a two-component developer composed of toner and magnetic particles. The present invention relates to a developing device that develops a latent image.

[0002]

2. Description of the Related Art In recent years, with regard to a developing device for developing a latent image formed on an image carrier using a two-component developer (hereinafter referred to as "developer") composed of toner and magnetic particles, downsizing of the device and From the viewpoint of cost reduction, there has been proposed one that controls the toner concentration and the toner charge amount without providing a complicated toner concentration control mechanism such as the developer stirring / conveying member and the toner concentration sensor (for example, JP-A-5
-273859, Japanese Patent Publication No. 5-67233). For example, in Japanese Patent Publication No. 5-67233, a magnetic particle layer is formed on a developer carrier in a container,
The toner is accommodated in the toner supply unit in the container so as to come into contact with the magnetic particle layer, and the magnetic particles in the magnetic particle layer move with the rotation of the developer carrier having a magnet fixedly arranged inside the toner. The toner is taken into the magnetic particle layer at the supply unit, and the developer in which the toner and the magnetic particles are mixed,
In a developing device in which a developer regulating member regulates the layer thickness and conveys the layer to a developing area, the magnet does not have a magnetic pole facing the toner replenishing portion, and is downstream of the toner supplying portion with respect to the rotation direction of the developer carrying member. And has a magnetic pole on the upstream side of the regulation member, and is provided on the downstream side of the toner supply section and on the upstream side of the regulation member at a position within the range of the magnetic field of the magnetic pole so as to face the developer carrying member. There is proposed a developing device having a shielding member that forms a region (hereinafter, referred to as a developer retaining portion) filled with the developer carrying member and filled with the magnetic particle layer.

2 (a) to 2 (c), a developer carrier 4 for carrying a developer composed of toner and magnetic particles on the surface, and a magnetic field generated inside the developer carrier 4 are generated. A means 5, a developer regulating member 6 for regulating the amount of the developer carried on the developer carrying body 4, and a developer holding portion A for holding the developer whose progress is blocked by the developer regulating member 6. A holding case 7 having an opening at the bottom for forming between the developer carrying member 4 and the developer carrying member 4 is provided, and is supplied from a toner storage portion (not shown) by the developer carrying force of the developer carrying member 4. This is a conventionally proposed developing device that takes in the toner into the developer in the developer retaining portion A and conveys it to the developing area.

In the developing device having the above-described structure, the developer on the developer carrying member 4 is conveyed as the developer carrying member 4 rotates in the direction of the arrow and is regulated by the developer regulating member 6 to form a thin layer. To be done. The thinned developer is conveyed to a developing area facing the latent image carrier 1 rotating in the arrow direction. Then, in the developing area, toner is supplied to the electrostatic latent image formed on the latent image carrier 1 to visualize the electrostatic latent image. The developer that has not been used for visualization is conveyed to the side facing the toner supply port as the developer carrier 4 rotates, and after taking in the new toner supplied from the toner supply port 8a, Return to the developer holding section A.
Then, the internal pressure of the developer in which the new toner is taken in is increased by the regulation of the developer regulating member 6, and the toner of the developer is dispersed and the toner is charged. In this way, the developer holding section A
Since the toner in the developer on the developer carrier 4 can be charged by the increase in the internal pressure of the developer in, the complicated stirring mechanism for charging or stirring the developer such as a paddle and a screw is unnecessary. .

On the other hand, a part of the developer which has not been supplied to the developing area and whose progress is blocked by the developer regulating member 6 is stored in the toner accommodating portion in the developer retaining portion A due to the internal pressure and gravity of the developer itself. It moves toward the toner supply port 8a. The developer that has moved to the vicinity of the toner supply port 8a is conveyed so as to circulate to the developer regulating member 6 side as the developer carrier 4 rotates.

Next, the moving state of the developer in the developer holding section A will be described. A part of the developer that is conveyed to the downstream side in the rotation direction of the developer carrying member 4 so as to hit the developer regulating member 6 flows above the developer carrying member 4 toward the holding case 7 and the developer holding portion. It comes to make a rotational movement in A.

The toner in the toner accommodating portion is taken into the developer from the vicinity of the confluence point c between the flow indicated by the symbol a and the flow indicated by the symbol b in FIG. At this time, the developer is moving in the vicinity of the surface of the developer carrying member 4 at a rate of about 100 mm / sec, and since the developer retaining portion A still has sufficient voids, the developer retaining layer is Rotation speed is about 10 mm /
sec.

FIG. 2B shows a state in which the toner intake is started. When the toner concentration and the developer volume gradually increase as the toner is taken into the magnetic particles, the developer moving layer that moves with the rotation of the developer carrier 4 expands, and the confluence point c gradually develops. The flow velocity a of the developer near the surface of the developer carrying member 4 decreases as the distance from the surface of the developer carrying member 4 increases. At this time, the developer is moving near the surface at a speed of about 65 mm / sec,
The rotation speed of the developer retaining portion A is about 5 mm / sec.

Next, as shown in FIG. 2C, the amount of toner replenished to the developer is increased, the toner density is increased, the bulk of the developer is increased, and the developer retaining portion A has no void. Therefore, the fluidity of the developer gradually deteriorates. Therefore, as the developer moving layer expands, the confluence point c approaches the inside of the holding case front end portion 7a. As a result, the toner is no longer taken into the developer.
At this time, the rotation speed of the developer retaining portion A is about 1 mm / sec.
It has become. However, in the developer retaining portion A, there is a portion where the developer remains still in a loosely filled state,
The developer in this part has a relatively high toner content compared to the other parts, and although it has a very slow flow speed, it continues to rotate, in which the toner is dispersed and charged in the developer. Is starting up.

Then, the toner is consumed by the development,
When the toner concentration in the developer holding section A decreases and the bulk of the developer decreases, the state returns to the state of FIG. 2A, so that the toner starts to be taken into the developer again. At this time, not only the toner newly taken into the developer but also the toner which is dispersed in the developer while rotating in the developer retaining portion A as described above and in which the charged electric charge rises is naturally developed. Since the toner is conveyed to the area, a large amount of toner is used for development, and even when a large amount of toner is taken into the developer, scumming and toner scattering due to insufficient charging of the toner becomes severe. Such problems are less likely to occur.

When the toner density of the developer becomes low, the bulk of the developer decreases, so that the developer is replenished by the toner replenishing section 8a.
Since the toner is not blocked, a predetermined amount of toner is taken into the developer on the developer carrying member 4, and the toner concentration of the developer is always maintained at a certain concentration or higher. Since the upper limit of the toner concentration can be controlled in this way, a complicated toner concentration control mechanism using a toner concentration sensor, a toner replenishing member, etc. is not required.

[0012]

However, conventionally, in the developing device having the above-mentioned structure, there has been a problem that the image density tends to be uneven in the axial direction of the developer carrying member. The cause of this problem is that the amount of magnetic particles held is reduced or increased locally in the axial direction of the developer carrier, and as a result, the toner concentration is partially increased or decreased. That is. Here, the amount of magnetic particles held is partially reduced in the axial direction of the developer carrying member because the magnetic force of the magnetic field generating means provided in the developer carrying member holds it in the developer holding section A. The magnetic particles are released from being held by the magnetic force due to vibration and fall by their own weight, or partially in the longitudinal direction due to the unevenness of the magnetic force distribution of the magnetic field generating means provided on the developer carrier in the axial direction. The magnetic particles fall, or the toner concentration in the developer in the developer holding section A rises and the amount of magnetic particles that can be held decreases, and the magnetic particles fall from the developer holding section. The magnetic particles that have fallen from may drop from the lower opening of the holding case forming the developer holding section into the toner containing section adjacent to the developer holding section, and fall into the toner containing section. Magnetism Since the body is never again return to the developer holding unit, thereby believed magnetic particles of the developer holding portion is to reduce.

The present invention has been made in view of the above problems, and its object is to release the magnetic force of the magnetic field generating means from being held by vibration, uneven magnetic force distribution of the developer carrying member, increase of toner concentration and the like. It is an object of the present invention to provide a developing device in which magnetic powder falling from a developer retaining portion is supplied to the developer retaining portion again so that the formed image does not have image density unevenness in the axial direction of the developer carrier.

[0014]

In order to achieve the above object, a developing device according to a first aspect of the invention is provided with a developer regulating member for regulating the amount of the developer composed of toner and magnetic particles conveyed to the developing area. The developer whose passage through the gap between the developer regulating member and the developer carrier is regulated is magnetically retained in the developer retaining portion between the surface of the developer carrier and the retaining case opened downward. At the same time, the toner supplied from the toner accommodating portion located on the side of the toner accumulating portion is accumulated in the toner accumulating portion located below the opening, and the developer is moved by the developer carrying by the developer carrier. In the developing device for taking in the toner in the toner retaining portion into the developer in the developer retaining portion, the inner surface of the bottom wall of the toner retaining portion is accommodated in the toner storage area more than in the side wall lower end portion of the opening on the toner storage portion side. Extends to the department side It was, and is characterized in that it has formed to be inclined from the toner accommodating portion so as to be lower toward the side of the developer carrying member.

In the developing device according to the first aspect, even if the magnetic particles fall through the opening of the holding case, the fallen magnetic particles are contained in the toner rather than in the lower end portion of the side wall of the opening on the toner accommodating portion side. The toner is received by the inner surface of the bottom wall of the toner retaining portion extending to the storage portion side. Thus, the magnetic particles received on the inner surface move to the developer carrying body side on the inner surface inclined so as to become lower from the toner containing portion side to the developer carrying body side, and magnetic force is carried on the developer carrying body. It is held by the body and supplied again to the developer holding section.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment in which the present invention is applied to a developing device used in an electrophotographic copying machine (hereinafter referred to as "copying machine") which is an image forming apparatus will be described. FIG. 1 is a partial cross-sectional view illustrating a schematic configuration of a developing device according to the present embodiment. This developing device is disposed laterally of a cylindrical photosensitive drum 1 which is a latent image carrier used in an image forming apparatus, and supports a supporting case 2 for supporting the developing device from below, toner and magnetic particles (hereinafter referred to as "carrier"). The developing sleeve 4 as a developer carrying member carrying a developer 3 on the surface, a magnet roller 5 made up of a fixed magnet group as a magnetic field generating means fixedly arranged inside the developing sleeve 4, and a developing sleeve 4. A doctor 6 as a developer regulating member that regulates the amount of the developer 3 carried and conveyed on the upper side;
The front sleeve 7 serving as a holding case that forms a space for storing the developer 3 that is to be stored above the developing sleeve 4 and the toner hopper 8 that serves as a toner storage unit are provided.
Then, a part of the developing sleeve 4 is exposed from the opening between the support case 2 and the doctor 6, and the photosensitive drum 1 is exposed.
Facing.

The lower front portion of the doctor's front desk 7 is opened, and a side wall 7a of the front side doctor blade 7 on the upstream side in the rotation direction of the developing sleeve 4 is provided along the developing sleeve 4 with a predetermined space. A developer holding portion A that extends at a distance and holds the developer 3 which is not supplied to the developing area facing the photoconductor drum 1 between the developing sleeve 4 and the developing sleeve 4 and whose passage is restricted by the doctor 6. Is formed. In addition, below the opening of the doctor's front knee 7, there is a bottom wall inner surface 10 further below the opening.
A toner accumulating portion B for accumulating the toner supplied from the toner hopper is formed between and.

The toner hopper 8 is provided adjacent to the upstream side of the developer retaining portion A in the developer transporting direction, and the toner transporting means sends the toner to the toner retaining portion B while stirring the toner. An agitator 9 as a rotary blade for use is provided.

In the developing device having the above-mentioned structure, the developer 3 on the developing sleeve 4 is conveyed as the sleeve 4 rotates in the direction of the arrow, and is regulated by the doctor 6 to form a thin layer. The thinned developer 3 is conveyed to a developing area facing the photoconductor drum 1 rotating in the arrow direction. Then, in the developing area, toner is supplied to the electrostatic latent image formed on the photosensitive drum 1, and the electrostatic latent image is visualized. Developer 3 not used for this visualization
Is taken in by the rotation of the developing sleeve 4, the new toner sent by the agitator 9 and supplied to the toner accumulating portion B is taken in, and then returns to the developer holding portion A. Then, the internal pressure of the developer 3 containing new toner increases due to the restriction of the doctor 6, and the toner of the developer 3 is dispersed and the toner is charged. In this way, the toner in the developer 3 on the developing sleeve 4 can be charged by the increase in the internal pressure of the developer 3 in the developer holding portion A, so that the developer 3 such as a paddle or a screw is charged or stirred. No complicated stirring mechanism is required.

On the other hand, a part of the developer 3 which is not supplied to the developing area and is prevented from advancing by the doctor 6 is stored in the developer holding portion A by the internal pressure and gravity of the developer 3 itself, and is left in the front of the doctor's knee 7. Move towards the opening. The developer 3 that has moved to the vicinity of the opening is conveyed so as to circulate to the doctor 6 side as the developing sleeve 4 rotates.

Here, in the developing device of the present embodiment, the inner surface 10 of the bottom wall of the toner retaining portion B and the inner wall of the toner hopper 8 are integrally formed by the supporting case 2 so that the toner retaining portion B is formed.
An inner surface 10 of the bottom wall of the doctor's front knee 7 extending to a toner storage portion side from a lower end portion of a side wall 7a of the doctor storage device 7 on the toner storage portion side, and inclined so as to be lower from the toner storage portion side to the developing sleeve 4 side. Is formed. According to this configuration, when vibration, uneven magnetic force distribution of the magnet roller 5, a partial increase in toner concentration in the developer 3, or the like occurs, the developer holding portion A is opened through the opening of the front doctor blade 7.
Even if the carrier falls from the inside, the dropped carrier is received by the inner surface 10 of the bottom wall of the toner retaining portion B, moves on the inner surface 10 of the bottom wall to the developing sleeve 4 side having a lower inclination, and is magnetically generated. The toner is held by the developing sleeve 4 and is again supplied to the developer holding section A. As a result, it is possible to prevent the amount of carriers in the developer retaining portion A from decreasing, and it is possible to prevent the occurrence of image density unevenness in the formed image in the axial direction of the developing sleeve 4.

Here, the inner surface 1 of the bottom wall of the toner retaining portion B is
It is preferable that the protrusion amount w of the end portion 10a of the toner storage portion side 0 toward the toner storage portion side with respect to the inner surface of the side wall 7a of the doctor front hist 7 on the toner storage portion side is 1 to 5 mm. This distance is 1
If it is shorter than mm, use the agitator 9 and the toner hopper 8.
The amount of toner sent out from the bottom wall 10 is reduced, the amount of toner in the toner retaining portion B is reduced, and as a result, the toner is not sufficiently taken into the developer 3. On the other hand, if this distance is longer than 5 mm,
The movement of the toner on the bottom wall becomes poor, and it becomes difficult for the toner to be taken into the developer 3 from the toner retaining portion B.

Further, in the developing device of this embodiment, the shape of the inner wall surface of the toner hopper 8 is formed substantially along the trajectory of the tip of the agitator 9 by the rotation of the agitator 9. FIG.
FIG. 9 is a cross-sectional view showing the shape of the inner wall surface of the toner hopper 8 of the developing device having the agitator 9 in the conventionally proposed toner hopper 8. As shown in this figure, the agitator 9
The shape of the inner wall surface of the toner hopper 8 retreats toward the developing sleeve 5 side on the developing sleeve 5 side with respect to the locus of movement of the tip of the agitator 9 by the rotation of the agitator 9, and a gap 12 is formed between the locus and the inner wall surface of the toner hopper 8. Therefore, when the toner is sent to the developer holding portion A (see also FIG. 2) by the rotation of the agitator 9, the toner sent to the void 12 is accumulated one after another, and is gradually pressed and blocked. Will end up. Conventionally, such blocking occurs partially by the axial direction of the developing sleeve 4, the amount of toner supplied to the developer retaining portion A decreases, and the toner concentration partially decreases in the axial direction of the developing sleeve 4. Then, the image density may be uneven. In the developing device of this embodiment, the tip of the agitator 9 rotates in a path substantially along the inner wall surface of the toner hopper 8, and a gap 12 is formed between the tip of the agitator 9 and the inner wall surface of the toner hopper 8 to block the toner.
Since this does not occur, it is possible to prevent the occurrence of the above problems.

Further, the toner on the bottom wall of the toner hopper 8 beyond the end 10a of the inner surface 10 of the bottom wall on the toner accommodating portion side is supplied to the toner accumulating portion B and taken into the developer 3 more smoothly. In order to prevent the rotation of the developing sleeve 4 from the rotation center 4 of the developing sleeve 4 as shown in FIG.
It is preferable to form the bottom wall so as to be above the horizontal plane including a. By forming the bottom wall in this way, the toner supplied from the toner hopper 8 over the end portion is easily moved to the lower side by gravity, and is taken into the developer 3 favorably.

Furthermore, in order to favorably convey the toner in the toner hopper 8 by the agitator 9 without causing toner blocking, as shown in FIG. 5, an elastic blade made of an elastic member such as Mylar is provided at the tip of the agitator 9. It is also possible to attach 9a and rotate the agitator 9 so that the tip of the elastic blade 9a scrapes the inner wall surface of the toner hopper 8. According to this configuration, the toner is less likely to be blocked on the inner wall surface of the toner hopper 8. Here, the elastic blade 9a is pressed against the inner wall surface of the toner hopper to be curved, and the tip portion of the blade 9a is in contact with the inner wall surface with a certain width x. The contact width x is set to about 2 to 3 mm. Then, the toner is favorably taken from the toner hopper 8 to the inner surface 10 of the bottom wall of the toner retaining portion B.

[0026]

According to the developing device of the first aspect, even if the magnetic particles fall through the opening of the holding case, the dropped magnetic particles are received by the inner surface of the bottom wall of the toner retaining portion, and the toner is stored. Since the inner surface inclined so as to be lowered from the side of the developer to the side of the developer is moved to the side of the developer, the magnetic force holds the developer on the developer carrier and supplies the developer again to the developer holding unit. In addition, it is possible to prevent the magnetic particles in the developer retaining portion from partially decreasing, and it is possible to prevent occurrence of uneven image density in the formed image in the axial direction of the developer carrier.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional view showing a schematic configuration of a developing device according to the present embodiment.

FIG. 2A is an explanatory diagram showing a state before starting to take in toner into a developer. 9B is an explanatory diagram showing a process of taking toner into the developer. FIG. 6C is an explanatory diagram showing a state in which the toner incorporation into the developer is completed.

FIG. 3 is an explanatory diagram showing a shape of an inner wall of a toner hopper in a conventionally proposed developing device.

4 is a partial cross-sectional view showing a schematic configuration of a modified example of the developing device shown in FIG.

FIG. 5 is a partial cross-sectional view showing a modified example of the agitator applicable to the present embodiment.

[Explanation of symbols]

 1 Photoreceptor Drum 2 Support Case 3 Developer 4 Developing Sleeve 4a Center of Rotation of Developing Sleeve 5 Magnet Roller 6 Doctor 7 Doctor Front Hisse 7a Sidewall 8 Toner Hopper 8a Toner Supply Port 9 Agitator 9a Elastic Blade 10 Bottom Wall Inner Surface 10a Edge 12 Void A developer holding part B toner retention part w protrusion amount

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasushi Akiba 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd.

Claims (1)

[Claims] 1. Development in which a developer regulating member for regulating the amount of a developer composed of toner and magnetic particles conveyed to a developing area regulates passage of a gap between the developer regulating member and a developer carrying member. The agent is magnetically retained in a developer retaining portion between the surface of the developer carrying member and a retaining case having an opening at the lower side, and at the toner retaining portion located below the opening, the side of the toner retaining portion is provided. Development in which the toner supplied from the toner containing portion located on the other side is retained, and the toner in the toner retaining portion is taken into the developer in the developer retaining portion by the movement of the developer accompanying the developer conveyance by the developer carrier. In the apparatus, the inner surface of the bottom wall of the toner retaining portion extends from the lower end of the side wall of the opening on the toner containing portion side to the toner containing portion side, and from the toner containing portion side to the developer carrying body side. Get lower The developing device is formed so as to be inclined like this.