JPH0962071A - Developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To discharge developer scooped up by a blade toward a developing sleeve neither too much nor too little by tilting the part of the blade having a paddle wheel toward a rear side with respect to a rotating direction. SOLUTION: The paddle wheel 14 is provided to rotate counterclockwise, and plural blades 14A extended in the normal direction from the center of rotation are provided along a peripheral direction. A leading end part 14A equivalent to the part of the blade 14A is tilted backward with respect to the rotating direction. A straightening member 22 is arranged in the vicinity of the paddle wheel 14. The member 22 is provided, so that the developer discharged by the paddle wheel 14 is straightened according to air flow caused by the rotation of the paddle wheel 14, and is moved toward the developing sleeve side. Thus, the developer can be efficiently discharged by effectively using centrifugal force caused in the case of the rotation of the paddle wheel 14.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device,
More specifically, it relates to a developer supply mechanism.

[0002]

2. Description of the Related Art Conventionally, in a developing device used in an image forming apparatus such as an electrophotographic copying machine or a printer, as a developer,
There is a magnetic brush developing device that uses a two-component developer in which a magnetic carrier and a magnetic or non-magnetic toner are mixed. When a two-component developer is used, the developer mixed by stirring and frictionally charged with opposite polarities is supplied to the developing roller.

The two-component developer is carried in a state in which a magnetic brush is formed on the surface of a developing roller having magnets for a main developing pole and a developer transporting inside. The two-component developer carried on the surface of the developing roller is subjected to visible image processing by electrostatically adsorbing the toner of the two to the electrostatic latent image carried on the photoconductor. Has become.

By the way, in such a magnetic brush developing device, only one developing roller may be provided.
In this case, since the developing area for the photoconductor is relatively narrow, it may not be possible to sufficiently supply the developer.

In order to eliminate the insufficient supply of the developer, it is possible to arrange a plurality of developing rollers in parallel along the moving direction of the photosensitive member.

However, in this structure, the developer passes through the gap existing between the adjacent developing rollers,
There are cases where the vehicle does not move along a predetermined moving route. That is,
It is desirable for the developer carried on the surface of the developing roller to move along the peripheral surface of the developing roller facing the surface of the photoconductor, in order to improve the contact efficiency with the surface of the photoconductor. For this purpose, it is necessary to transfer the developer between the peripheral surfaces facing the photoconductor. However, a part of the developer released from the paddle wheel rotates according to the rotation of the developing roller while being carried on the surface of one developing roller, and passes through the gap existing at the position where the developing rollers face each other. However, there is a case where the transfer to the other developing roller is not performed due to the accompanying phenomenon of moving to the side opposite to the position facing the photoconductor.

When the developer released from the paddle wheel reaches the other developing roller, the developer adsorbed on the developing roller passes through the gap existing at the position where the developing rollers face each other. May be brought to a position facing the photoconductor. Therefore, the amount of the developer carried by the other developing roller is the sum of the amount transferred from the one developing roller and the amount adsorbed by itself, so that the developer comes into contact with the photosensitive member in an excessive state.

As described above, when the developer is accompanied by the developing roller on the side of one developing roller, the amount of the developer transferred to the other developing roller tends to be insufficient, so that the developer is formed on the photosensitive member. The amount of contact with the latent image
There is a risk that the image density will decrease and that the toner that is being supplied to the latent image and that is being developed will scatter. Further, if the developer is excessively carried on the other developing roller, a load variation on the photoconductor side is generated when the developer comes into contact with the photoconductor, and speed unevenness causes striped density unevenness in the image. When a part of the developer that is carried or carried collides with the housing and is knocked down, the developer may be scattered around and contaminated.

Therefore, in order to solve such a problem,
Among the magnetic poles provided on one of the developing rollers arranged in parallel, there is proposed a configuration in which the polarities of the magnetic poles adjacent to each other at the positions where the developing rollers face each other are set to the same polarity (for example, Japanese Patent Application Laid-Open No. Hei 5 (1999) -58242). -346737).

FIG. 4 is a diagram showing the above proposed structure. In FIG. 4, a drum-shaped photosensitive member 2 is provided inside the developing device 1.
A pair of developing rollers 3 and 4 which are arranged in parallel along the circumferential direction of the photoconductor 2 so as to face each other and have an odd number of magnetic poles, the polarities of which are N and S. , And the polarities of the magnetic poles arranged at positions where the developing rollers of one of the developing rollers face each other are set to the same polarity.

At the position where the developing rollers face each other, a repulsive magnetic field is formed by the magnetic poles of the same polarity located on one of the developing rollers, so that at the position where the developing rollers face each other.
A barrier is formed by the repulsive magnetic field. For this reason, the developer released from the paddle wheel 5 cannot move into the gap at the position where the developing rollers face each other and moves toward one of the developing rollers 3, as indicated by symbol A1. It will be. Further, the developer carried on one of the developing rollers 3 is shielded by the repulsive magnetic field even when the developing rollers try to move to the position where the developing rollers face each other, and as shown by reference numeral D1, the peripheral surface on the side facing the photoconductor 2 is indicated. Can be moved toward the other developing roller 4. Further, the developer directly discharged from the paddle wheel 5 toward the other developing roller 4 is prevented from entering the gap at the position where the developing rollers are opposed to each other, as indicated by symbol A2. , And can be moved to one developing roller 3 side. Moreover, since the developer transferred from the one developing roller 3 is carried on the peripheral surface of the developing roller facing the photoconductor, the developer is brought into contact with the photoconductor 2 without excess or deficiency, as indicated by reference numeral D2. Can be made.

[0012]

By the way, the paddle wheel 5 used in the developing device is required to efficiently discharge the agitated and mixed developer toward the developing roller. For this reason, conventionally, as shown in FIG. 4, as a structure of the paddle wheel 5, a part of the blade extending in the direction of the normal to the center of rotation, particularly the tip, is the paddle wheel 5.
Is inclined forward with respect to the rotation direction (the direction of the arrow in the figure), so that the developer accumulated in the developing device 2 can be easily scooped.

The paddle wheel 5 having the above-described structure can scoop off the developer mixed with stirring while further stirring, but has the following problems.

The paddle wheel 5 is rotated at a high speed, and the developer scooped by the centrifugal force generated at that time is discharged toward the developing rollers 3 and 4. However, since some of the blades are inclined forward in the rotational direction, when the scooped developer reaches the inclined portion by centrifugal force, the inclined portion tends to suppress the release,
There has been a situation in which the supply amount to the developing roller is not sufficient. Moreover, among the developers released toward the developing sleeve, the excess developer not adsorbed to the developing sleeve and the developer not released are liable to drop or scatter. However, there is also a possibility of causing a secondary adverse effect such that the periphery of the apparatus or the transfer paper used for image transfer is contaminated.

Therefore, in view of the above-mentioned problems in the conventional developing device, an object of the present invention is to provide a developing device capable of preventing the scattering of the developer and preventing the surroundings of the developing device and the transfer paper from being contaminated. To do.

[0016]

In order to achieve this object, the invention according to claim 1 discharges a developer toward a developing roller for forming a magnetic brush which is arranged so as to face a latent image carrier. In a developing device provided with a rotatable paddle wheel, the paddle wheel has a plurality of blades extending in a direction normal to a rotation center along a rotation direction, and a part of the blades is rearward in the rotation direction. The feature is that it is inclined toward the side.

According to a second aspect of the invention, in the developing device according to the first aspect, a rectifying member for rectifying the discharged developer toward the developing roller is arranged near the paddle wheel. It is characterized by that.

According to a third aspect of the present invention, in the developing device according to the second aspect, the rectifying member has the same curvature as the rotation locus of the blade of the paddle wheel, and is the same as the tip of the blade. It is characterized by having a rectifying surface in which a gap of a size is set.

According to a fourth aspect of the present invention, in a developing device provided with a developing roller for forming a magnetic brush, which is arranged so as to face the latent image carrier, the developing device is rotatably provided, and is arranged along the rotational direction. A paddle wheel in which a part of the blade extending in the direction normal to the rotation center is inclined rearward in the rotation direction, and the paddle wheel is arranged in the vicinity of the rotation trajectory of the blade of the paddle wheel, and the rotation direction of the paddle wheel. And a straightening member having a straightening surface formed in a shape such that a gap from the tip of the blade is larger on the rear side in the rotation direction than on the front side.

According to a fifth aspect of the present invention, in the developing device according to the fourth aspect, the rectifying surface has a large gap between the front and rear sides of the paddle wheel in the rotation direction from the front side to the rear side. It is characterized in that the shape of the rectifying surface is set so that

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, referring to FIG. 1 to FIG.
The details of the described invention will be described.

FIG. 1 is a sectional view showing the overall construction of the developing device according to the first to third aspects of the invention. In FIG. 1, the construction of the developing device 10 will be described below along with its functions.

That is, the developing device 10 includes the developing container 10
The developing container 10A includes a drum-shaped photoconductor (hereinafter, referred to as a photoconductor drum) that is a latent image carrier movable in a direction indicated by an arrow AO in the figure. ) 12, and the toner replenishing section 10B is mounted in the developing container 10A.

Inside the developing container 10A, the stirring roller 1 is provided.
3 and a paddle wheel 14 are provided.

A two-component developer composed of a magnetic or non-magnetic toner and a magnetic carrier, which are agitated and mixed by an agitating roller 13 and frictionally charged in opposite polarities, is scooped by a paddle wheel 14. .

The toner replenishing section 10B is provided, for example, when the density of the toner supplied to the photosensitive drum 12 decreases.
The toner T is fed toward the stirring roller 13 by the rotation of the toner supply roller 10B1.

On the other hand, at a position where the developer is drawn up by the paddle wheel 14, a plurality of developing rollers 15 and 16 are arranged close to the photosensitive drum 12.

The developing rollers 15 and 16 are the photosensitive drums 1.
2 are disposed on the upstream side and the downstream side along the moving direction of 2, and the one located on the upstream side is the first developing roller 15, and the one located on the downstream side is the second developing roller 16. Has been done.

The developing rollers 15 and 16 are counterclockwise corresponding to a rotation direction in which an arbitrary position on the peripheral surface can be moved in the same direction at a position facing the photosensitive drum 12 in the drawing by a driving unit (not shown). The main part is provided with a sleeve rotatable in a direction and a mag roller fixed inside the sleeve. Of these, the sleeve is made of a non-magnetic material such as aluminum or stainless steel, and the mag roller is a ferrite magnet or a rubber magnet, and a magnetic pole formed by kneading nylon powder and ferrite powder along the circumferential direction. It has a structure in which multiple units are arranged. The magnetic pole will be described later.

In the developing container 10A, an arbitrary portion on the peripheral surface of the first developing roller 15 is a photosensitive drum 12.
The doctor blade 17 for regulating the layer thickness of the magnetic brush carried on the developing roller 15 is provided at a position before reaching the doctor blade, and one end in the extension direction is provided near the doctor blade 17 in the extension direction. The separators 18 are arranged in the vicinity of 17 and the other ends in the extension direction are positioned above the stirring roller 13, and the rotatable conveying screw 19 is arranged at the other end in the extension direction of the separator 18. ing.

In FIG. 1, reference numerals 20 and 21 are seal members which are attached to a supporting member 19A of the doctor blade 19 and shield above the facing position between the photosensitive drum 12 and the first developing sleeve 15.

In the mag roller provided in the developing rollers 15 and 16 in this embodiment, the arrangement of magnetic poles is set as follows.

That is, in FIG. 1, the alternate long and short dash line shown in the developing roller indicates the position of the magnetic pole, and the number of magnetic poles on the side of the first developing roller 15 is an odd number (see the figure). The numbers P _{11 to} P ₁₅ ), and the number of magnetic poles on the side of the second developing roller 16 are odd (numbers P _{21 to} P _{23 in the} drawing) along the circumferential direction.

The order in which the developer is conveyed by these magnetic poles is as follows.
It is set in the order of P ₁₃ → P ₁₄ → P ₁₅ → P ₁₁ → P ₁₂ → P ₂₃ → P ₂₁ → P ₂₂ . In order to enable such conveyance, the polarities of the respective magnetic poles are P ₁₃ (S pole) → P ₁₄ (N pole) → P ₁₅ (S pole) → P ₁₁ (N very)
Different poles are alternately arranged in the order of → P ₁₂ (S pole) → P ₂₃ (N pole) → P ₂₂ (S pole) → P ₂₁ (N pole).

On the side of the first developing roller 15, since the number of poles is an odd number, there is always a place where the same poles are lined up. In the case of this embodiment, the first developing roller 15 is arranged.
Both the magnetic poles P ₁₂ and P ₁₃ on the side are aligned with the S poles.

The position where the same poles are lined up is the position where the developing rollers 15 and 16 are closest to each other. In the embodiment shown in FIG. 1, the magnetic pole P ₁₂ is the rotational direction of the first developing roller 15. The magnetic pole P ₁₃ is arranged on the upstream side (counterclockwise) and on the downstream side in the rotation direction (counterclockwise) of the first developing roller 5.

Due to the arrangement of the magnetic poles as described above, a repulsive magnetic field due to the same poles is formed between the positions where the developing rollers 15 and 16 are closest to each other.

In the developing container 10A, the developer is scooped up by the centrifugal force generated when the paddle wheel 14 is rotated and is pumped up and discharged toward the first developing roller 15. Therefore, a part of the released developer is
As indicated by an arrow A1, the toner is directly supplied to the first developing roller 15 and carried on the surface of the first developing roller 15.
When another part of the discharged developer hits the second developing roller 16 and bounces back, it is carried on the surface of the first developing roller 15 by the magnetic force on the first developing roller 15 side.

In order to supply the developer to the first developing roller 15 also from the second developing roller 16 side, the paddle wheel is used for the purpose of increasing the amount of rebound from the second developing roller 16. It is necessary to make the rotational speed of 14 relatively high and increase the centrifugal force.

The developer carried on the first developing roller 15 moves on the roller surface as the developing sleeve rotates,
After the layer thickness is regulated by the doctor blade 17,
When the developing roller 15 reaches the first developing area D1 where the photosensitive drum 12 faces each other and moves to a position where the action of the magnetic force on the first developing roller 15 side is weakened, the second developing roller 1
By the rotation of the developing sleeve on the 6 side and the magnetic force from the mag roller, the second developing roller 16 and the photosensitive drum 12 are transferred toward the second developing area D2 facing each other, as indicated by the broken line in the figure, Then, at a position where the magnetic force of the second developing roller 16 does not act, the second developing roller 16 falls to the bottom of the developing container 1A and is again stirred by the paddle wheel 14.

The developer scraped off by the doctor blade 17 is guided by the separator 18 toward the conveying screw 19 located at the other end in the extension direction, and is dropped onto the stirring roller 16 by the conveying screw 19. ing. Therefore, a slit for dropping the developer is formed at the other end of the separator 18 in the extension direction at a position facing the stirring roller 16.

In FIG. 1, the paddle wheel 14 is provided so as to be rotatable in the counterclockwise direction, and the peripheral surface thereof is
A plurality of blades 14A extending in the normal direction from the center of rotation are provided along the circumferential direction.

Tip portion 14B corresponding to a part of blade 14A
Is inclined rearward with respect to the rotation direction, as shown in FIG.

The inclination angle of the tip portion 14B is determined in consideration of the following. After the optional blade 14A scoops the developer, it does not prevent the developer from moving toward the tip portion due to centrifugal force. When the tip portion rotates, the same direction as the rotation direction around the tip portion. Direction can be generated.

In the vicinity of the paddle wheel 14, a rectifying member indicated by reference numeral 22 in FIG. 1 is arranged. The rectifying member 22 is provided to rectify the developer discharged by the paddle wheel 14 in accordance with the airflow generated by the rotation of the paddle wheel 14 and move the developer toward the developing sleeve.

In this embodiment, the rectifying member 22 has the following features. In the rectifying member 22, the rectifying surface 22A facing the blade of the paddle wheel has the same curvature as the rotation trajectory of the paddle wheel 14, and a gap (L1) of the same size is set between the blade and the tip of the blade. ing. The area length of the rectifying surface 22A is made to correspond to the area length of the area where the blade 14A moves after scooping off the developer.
As a result, the space between the blades 14A and the space between the straightening surfaces 22A are always set to the same size.

Since the present embodiment has the above configuration,
The developer scooped by the blades 14A of the paddle wheel 14 moves toward the tip portion 14B of the blades 14A by the centrifugal force generated by the high speed rotation of the paddle wheel 14,
Is released. The discharged developer is the rectifying surface 2 of the rectifying member.
Due to the airflow generated between 2A and 2A, it moves toward the developing sleeve side and is pushed away. On the other hand, between the blades 14A of the paddle wheel 14 that has released the developer, a negative pressure tends to occur due to volume expansion. For this reason, when the blade 14A forming the negative pressure space passes through the region of the rectifying surface 22A of the rectifying member 22 and faces the developing sleeve, the negative pressure acts on the vicinity of the developing sleeve. For this reason, the developer that falls from the developing sleeve and tries to fly out of the apparatus has a relatively small weight because the amount of the dropped developer is smaller than the amount that is pushed toward the developing sleeve. It is easy to be sucked to the 14 side. Therefore, the developer that is about to be scattered outside the apparatus is collected by the paddle wheel 14, so that the scattering outside the apparatus is prevented. Particularly, the tendency of negative pressure due to volume expansion is made possible by the smooth release of the developer, but in the present embodiment, the inclination direction to the front side with respect to the normal direction or the rotation direction is set. Compared with the case where the developer is released, the inclination direction of the blade tip is set to the direction that promotes the release of the developer, so that the negative pressure tendency after the release of the developer is promoted and the developer that is about to be scattered is suctioned and collected. It can be done more efficiently.

According to this embodiment, the developer can be efficiently discharged by effectively utilizing the centrifugal force generated when the paddle wheel 14 rotates, so that the developer can be supplied to the developing sleeve side without excess or deficiency. It becomes possible to do. In addition, since the excess developer that exceeds the carrying amount on the developing sleeve side and the developer that has dropped from the developing sleeve are sucked by the paddle wheel 14, they will not be scattered outside the apparatus.

Next, the inventions described in claims 4 and 5 will be described.

The inventions of claims 4 and 5 are characterized in that the tendency of negative pressure generated in the paddle wheel after releasing the developer is made to act more effectively.

FIG. 3 is a sectional view showing a developing device according to the invention described in claims 4 and 5, in which the same components as those shown in FIGS. 1 and 2 are designated by the same reference numerals. .

In FIG. 3, the straightening member 22 arranged near the paddle wheel 14 has a straightening surface 22B in the front of the paddle wheel 14 in the rotational direction corresponding to the developing sleeve, unlike the structure shown in FIG. Location 22 located on the side
The shape (B2) is set so that the interval (L2) between the paddle wheel 14 and the blade tip portion 14B becomes large. In this embodiment, the straightening surface 22B is the paddle wheel 1
4 from the rear side to the front side in the rotation direction, the gap between the blades 14A of the paddle wheel 14 is continuously increased (L1 <L2).

Since this embodiment has the above-mentioned structure,
The developer scooped by the paddle wheel 14 moves toward the tip 14B of the blade 14A by the centrifugal force generated when the paddle wheel 14 rotates at high speed, and is discharged from the tip.

The released developer moves toward the developing sleeve side by the air flow generated between the developing sleeve and the rectifying surface 22B of the rectifying member 22, and the reference numerals A1 and A2 are applied to the developing sleeve.
Will be supplied in the state indicated by.

On the other hand, since the space between the blade 14A of the paddle wheel 14 and the portion 22B1 on the developing sleeve side of the rectifying surface 22B of the rectifying member 22 is made large, the paddle wheel 14 that has released the developer has a blade. 14
The volume of the space between A and the rectifying surface 22B of the rectifying member 22 is expanded, and volume expansion occurs. Therefore, when the blades 14A of the paddle wheel 14 reach the developing sleeve side, the tendency of negative pressure is strengthened due to volume expansion due to the shape change of the flow regulating surface 22B of the flow regulating member 22.

In the vicinity of the developing sleeve, the paddle wheel 1
Due to the tendency for negative pressure to be generated by 4 and the rectifying member 22, the excess developer that falls from the developing sleeve is sucked and is prevented from scattering.

According to the present embodiment, it is possible to prevent the developer from scattering with a simple structure in which the shape of the rectifying member is changed.

In the present invention, 2 shown as the embodiment
It goes without saying that not only the book developing roller is targeted, but also the case where three or more developing rollers are arranged along the moving direction of the photoconductor.

[0059]

As described above, according to the invention described in claim 1, since a part of the blades of the paddle wheel is inclined rearward with respect to the rotation direction, centrifugal force generated when the paddle wheel is rotated. Therefore, the developer can be smoothly moved, and the developer scooped by the blade can be discharged toward the developing sleeve without excess or deficiency.

According to the second and third aspects of the present invention, since the blade tip and the rectifying surface of the rectifying member are arranged at the same distance in the rotational trajectory of the blade of the paddle wheel, the paddle after the developer is discharged. The volume between the blades of the wheel and the flow-regulating surface is expanded to a negative pressure to suck in the developer that is about to scatter and prevent it from scattering outside the device or adhering to the transfer paper. Will be possible.

According to the fourth and fifth aspects of the present invention, after the developer is discharged, the gap between the blade tip of the paddle wheel and the rectifying member is set to be large on the developing sleeve side. It is possible to more effectively prevent the scattering to the outside of the apparatus and the adhesion to the transfer paper by more efficiently suctioning and collecting the developer that tends to scatter by strengthening the negative pressure tendency.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an overall configuration of a developing device according to the first to third aspects of the invention.

FIG. 2 is an enlarged cross-sectional view for explaining a main part of the developing device shown in FIG.

FIG. 3 is a sectional view showing an overall configuration of a developing device according to the inventions of claims 4 and 5.

FIG. 4 is a sectional view showing an example of a developing device.

[Explanation of symbols]

10 developing device 12 photoconductor drum 14 paddle wheel 14A blade 14B blade tip 15 first developing roller 16 second developing roller 22 rectifying member 22A, 22B rectifying surface 22B1 developing sleeve side portion of rectifying surface L1, L2 blade tip and Distance between straightening surface

Claims (5)

[Claims] 1. A developing device having a rotatable paddle wheel for discharging a developer toward a developing roller for forming a magnetic brush, which is arranged so as to face a latent image carrier, wherein the paddle wheel has a rotating direction. A developing device having a plurality of blades extending in a direction normal to a rotation center along, and a part of the blades being inclined rearward in the rotation direction. 2. The developing device according to claim 1, wherein a rectifying member for rectifying the discharged developer toward the developing roller is disposed in the vicinity of the paddle wheel. apparatus. 3. The developing device according to claim 2, wherein the straightening member has the same curvature as the rotation locus of the blade of the paddle wheel, and a gap of the same size is provided between the blade and the tip of the blade. A developing device having a rectified surface. 4. A developing device provided with a developing roller for forming a magnetic brush, which is arranged to face a latent image carrier, is rotatably provided, and extends in a direction normal to a rotation center along a rotation direction. A part of the blade extended to the rear of the paddle wheel in the direction of rotation, and the paddle wheel is arranged in the vicinity of the rotation path of the blade of the paddle wheel, and is rotated relative to the front side in the direction of rotation of the paddle wheel. A rectifying member having a rectifying surface formed in a shape such that a gap from the tip of the blade becomes large on the rear side in the direction. 5. The developing device according to claim 4, wherein the straightening surface of the straightening surface is formed continuously from the front side toward the rear side in the rotational direction of the paddle wheel so that the distance between the straightening surface and the tip of the blade increases. A developing device having a set shape.