JPH10149015A - Developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developing device which has self-controllability for the toner concentration so that the toner is taken into a developer in accordance with the toner concentration with movement of the developer in association with transport of the developer on its carrier and in which unevenness of the developing density in the direction perpendicular to the developer transporting direction of the carrier is suppressed. SOLUTION: Gap between a developing sleeve 4 and a doctor 6 is arranged as narrowing to the downstream about the developer transporting direction made by a developing sleeve 4. In this gap, the stress given to the developer 3 owing to touching and friction of developers 3 with each other and of the developer 3 with the doctor 6 enlarges gradually, and the rise of the electrostatic charge of the toner can be made quickly and effectively.

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 an image forming apparatus such as a copying machine, a facsimile, and a printer.
Specifically, a developer in a developer accommodating portion accommodating a two-component developer containing toner and magnetic particles is magnetically supported on a developer carrier having a magnetic field generating means therein, and a gap between the developer accommodating member and the developer regulating member is provided. The developer is conveyed to a developing region facing the latent image carrier of the image forming apparatus by rotating the developer after regulating the amount of the developer carried on the developer carrier by passing The toner in the toner container where the toner communicates with the toner container through the toner intake opening and the stored toner contacts the developer on the developer carrier is moved into the developer by the movement of the developer. It relates to a developing device for taking in.

[0002]

2. Description of the Related Art Conventionally, as a developing device of this kind, for example, a magnetic particle layer is formed on a developer carrier in a container, and a toner is supplied to a toner replenishing section in the container so as to contact the magnetic particle layer. The toner particles are taken into the magnetic particle layer by the toner replenishing section by the movement of the magnetic particles of the magnetic particle layer accompanying the rotation of the developer carrying member having the magnet fixedly disposed therein, and the toner and the magnetic particles are In a developing device in which the mixed developer is transported to the developing area with the layer thickness regulated by a developer regulating member, the magnet does not have a magnetic pole facing the toner replenishing unit, and the magnet is not rotated with respect to the rotation direction of the developer carrier. The developer has a magnetic pole downstream of the toner replenishing unit and upstream of the regulating member, and is located at a position downstream of the toner replenishing unit and upstream of the regulating member and within a range where the magnetic field of the magnetic pole reaches. Opposite to carrier There is known a developing device provided with a shielding member for forming a region filled with a magnetic particle layer (hereinafter referred to as a developer accommodating portion) between the developing device and the developer carrier (for example, Japanese Patent Publication No. 5-67233). Reference).

In this developing device, when the developer stagnating in the developer accommodating portion has a high toner concentration and a large bulk of the developer, the developer filling rate is increased and the developer is difficult to move. Except for the developer passing through, the developer in the developer accommodating portion hardly moves. Conversely, when the toner concentration decreases due to consumption of the toner and the volume of the developer becomes small, the filling rate of the developer in the developer accommodating portion decreases, and the developer easily moves. It is captured. Then, when the toner concentration of the developer increases and the bulk of the developer increases, the developer in the developer accommodating portion hardly moves again as described above, and the taking in of the toner stops.

FIG. 6 shows an example of such a developing device. The developing device is disposed on a side of a cylindrical photosensitive drum 1 serving as an image carrier, and has a casing 2 having an opening formed toward the photosensitive drum 1, and a part of the casing 2 is exposed from the opening. , Toner and magnetic particles (hereinafter “carrier”)
That. ), A developing roller 4 as a developer carrying member for carrying a developer 3 on the surface, a magnet roller 5 composed of a group of fixed magnets as magnetic field generating means fixedly arranged inside the developing sleeve 4, and a developing sleeve. A doctor 6 serving as a developer regulating member for regulating the amount of the developer 3 carried and conveyed on the developer 4, and a developer container 1 for the developer 3 between the developer sleeve 4 and the surface of the sleeve 4 above the developing sleeve 4
A cover member 7 provided so as to form a toner container 0, a toner hopper 8 as a toner container, and the like are provided. The toner hopper 8 has a toner replenishing opening 8a adjacent to the upstream side of the developer accommodating portion 10 in the developer transport direction and facing the surface of the developing sleeve 4.
A toner agitator 9 as a toner stirring and conveying member for feeding the toner 3a in the hopper 8 toward the toner supply opening 8a while stirring the toner 3a is disposed in a space adjacent to the toner supply opening 8a.

In this developing device, the developer 3 on the developing sleeve 4 is transported with the rotation of the sleeve 4 in the direction of the arrow S, and is regulated to a predetermined amount by the doctor 6. The regulated developer 3 on the developing sleeve 4 is conveyed to the developing area A facing the photosensitive drum 1 rotating in the direction of the arrow. In the developing area A, the toner in the developer is supplied to the electrostatic latent image formed on the photosensitive drum 1,
Visualization of the electrostatic latent image is performed. The developer 3 that has passed through the developing area A is further transported with the rotation of the developing sleeve 4, passes through the toner supply opening 8 a filled with the toner sent out by the agitator 9, and
Return to 0. While passing through the toner supply opening 8a,
New toner 3a is taken into the developer portion where the toner concentration is reduced by the development. On the other hand, a part of the developer 3, which is not supplied to the developing area A and is prevented from proceeding by the doctor 6, reaches the vicinity of the toner supply opening 8 a in the developer accommodating section 10 due to the internal pressure of the developer 3 and gravity. The developer moves and the developer moving layer moves along with the rotation of the developing sleeve 4, and is conveyed to the doctor 6 side and circulated.

As described above, according to this type of developing device,
The incorporation of the toner 3a into the developer accommodating section 10 is automatically performed in accordance with the toner concentration of the developer, and the toner concentration is self-controlled, so that the toner concentration of the developer 3 is always within a substantially constant range. Kept to be. This eliminates the need for a complicated toner density control mechanism such as a toner density sensor and a toner replenishing member that is driven and controlled in accordance with the output of the sensor.

[0007]

However, in a conventionally proposed developing device such as the device shown in FIG. 6, unevenness in the charge amount of the toner occurs in a direction orthogonal to the direction of transport of the developer on the developer carrier. There is a problem in that the development density difference and background stain corresponding to the unevenness of the charge amount occur during the subsequent image formation.

FIG. 7 is an explanatory diagram of how the development density difference occurs. FIG. 7A shows a document image to be formed,
7B is a graph showing the toner charge amount distribution of the developer on the developing sleeve 4 after the image formation, and FIG.
(D) is a developed image when a solid halftone image is formed after the image formation. FIG. 8 is an enlarged view near the doctor 6 of the developing device. The document image to be image-formed is a document image having a black stripe on a white background.
Since the stripe extends in the rotation direction of the developing sleeve 4 of the developing device, only the toner at the portion facing the stripe is intensively consumed in the direction x orthogonal to the rotation direction of the developing sleeve 4, and The toner density decreases, and a large amount of new toner is taken in from the toner hopper 8.
Further, since the toner is not consumed in the white portion, new toner is not taken in, and the charged toner is used for the next image formation. As shown in FIG. 8, the excess developer 3 of the developer on the developing sleeve 4 is separated from the surface of the developing sleeve 4 by the doctor 6, and the remaining developer 3 is separated from the doctor 6 and the developing sleeve 4. However, if the new toner is transported to the developing area A as it is for the next image formation, the distance through which the toner passes through the regulatory area B, which receives stress, is short. And the doctor 6 and the like are not sufficiently rubbed with each other and cannot be sufficiently charged. And
When a solid halftone image is formed in a state where the charge of the new toner does not rise, as shown in FIG. 7D, the developing density is higher in the portion of the new toner that is insufficiently charged than in the other portions. A developed image having a difference in development density is formed.

In order to eliminate such density unevenness, for example, the developer is conveyed by the developer carrying member in a regulating area B regulated by a doctor 6 as a developer regulating member for regulating the developer on the developing sleeve 4. An improvement has been made in which the doctor 6 is formed so as to increase the distance in the direction to increase the stress applied to the developer and sufficiently charge the developer. However, since the developer that has entered the regulation area B passes through the regulation area B smoothly without a large change in density, even with such an improvement, the charging of the newly taken-in toner can be sufficiently performed. It's hard to get up. For this reason, it has not been possible to completely prevent the development density difference from appearing on the developed image corresponding to the partial difference in the toner charge amount in the developing sleeve axial direction.

Incidentally, for example, Japanese Patent Application Laid-Open No. 63-225269
In the developing device for developing a latent image using a developer having magnetic particles and toner particles in a developing unit, a developer container containing a developer having toner particles and magnetic particles, A developer carrying member for forming a developing unit for supplying toner particles to the latent image carrier, the developer carrying member for carrying and transporting a developer from the container to the developing unit; A magnetic field generating means provided on a side of the developer carrying member opposite to the developer carrying surface, and a member for regulating amounts of magnetic particles and toner particles applied on the developer carrying member surface, A developing device has been proposed, wherein a tip of a developer application amount regulating member is positioned in the developer at an upstream side in the developer carrier moving direction, and the regulating member is provided toward a downstream side in the moving direction. ing. According to this developing device, it is possible to reduce the load of the developer on the regulating portion, and to release the insufficiently charged toner from the developer carrying member to supply the sufficiently frictionally charged toner to the developing area. . This may contribute to the elimination of the difference in development density caused by unevenness in the toner charge amount in the direction orthogonal to the developer transport direction, but may not be sufficient in the ability to supply the developer to the development area. .

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to provide an image forming apparatus in which the movement of a developer accompanying the transport of the developer on a developer carrying member is carried out in accordance with the toner concentration. It is an object of the present invention to provide a developing device which is capable of controlling the toner concentration of the toner to be taken into the developing device, and which can suppress unevenness in the developing concentration in a direction orthogonal to the developer conveying direction of the developer carrying member.

[0012]

In order to achieve the above object, the invention of claim 1 provides a two-component developer containing a toner and magnetic particles on a developer carrier having a magnetic field generating means therein. After the developer in the accommodated developer accommodating portion is carried by magnetic force, and the amount of the developer carried on the developer carrying member is regulated by passing through the gap with the developer regulating member, the image forming apparatus is rotated. The developer is conveyed to a developing area opposed to the latent image carrier, and communicates with the developer accommodating section via the toner intake opening, and the contained toner is transferred to the developer on the developer carrier. In the developing device, the toner in the toner container that comes into contact with the developer is moved into the developer by moving the developer, and the width of the gap between the developer carrier and the developer regulating member is determined by the width of the developing device. Agent It is characterized in that it has formed to be narrower toward the developer conveying direction downstream side by the body.

In this developing device, the width of the gap between the developer carrier and the developer regulating member becomes narrower toward the downstream side in the developer conveying direction by the developer carrier. And the stress applied between the developers or between the developer and the developer regulating member gradually increases. This allows the toner in the developer to be charged more quickly and efficiently.

According to a second aspect of the present invention, in the developing device of the first aspect, the gap is formed by providing an inclined end of the developer regulating member on a side where the developer is regulated. It is.

In this developing device, since the gap is formed by providing an inclination at the end of the developer regulating member on the side where the developer is regulated, a separate member is attached to the developer regulating member to reduce the gap. Unlike the case where the separate member is formed, a step between the separate member and the regulating member, which is likely to occur when the separate member is attached, does not occur. Accordingly, since the developer does not stay due to the step, stress can be effectively applied to the developer.

According to a third aspect of the present invention, in the developing device of the first aspect, the gap is formed by providing the developer regulating member at an upstream side in a developer conveying direction by the developer carrier. It is a feature.

In this developing device, the gap is formed by arranging the developer regulating member at an upstream side in the developer conveying direction by the developer carrier.
Unlike the case where the gap is formed by attaching a separate member to the developer regulating member, a step between the separate member and the regulating member, which tends to occur when the separate member is attached, does not occur. Accordingly, since the developer does not stay due to the step, stress can be effectively applied to the developer.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a developing device of an electrophotographic copying machine (hereinafter referred to as a copying machine) as an image forming apparatus will be described. FIG. 1 is a schematic configuration diagram of a developing device according to the present embodiment. In the present embodiment, the gap between the developing sleeve 4 serving as the developer carrier and the doctor 6 serving as the developer regulating member is set such that the width of the gap is in the developer conveying direction by the developing sleeve 4 (hereinafter referred to as the agent conveying). (Referred to as the direction). Other configurations are the same as those of the developing device of FIG.

FIG. 2 is an enlarged view of the vicinity of the doctor 6. In the illustrated device, the distal end of the doctor 6 on the side that regulates the developer is formed so as to have a slope that forms a wedge between the distal end and the surface of the developing sleeve 4. The tip may be formed, for example, by chamfering the corner of the doctor 6 on the side where the developer 3 enters so that the shape of the tip shown in FIG. 8 is substantially parallel to the surface of the developing sleeve 4. it can. In the regulating region C between the doctor 6 and the developing sleeve 4 formed in this manner, the density of the developer 3 that has entered the regulating region C by the rotation of the developing sleeve 4 gradually increases as the developer 3 advances through the regulating region C. The stress applied to the developer 3 due to the contact and friction between the developers 3 and between the developer 3 and the doctor 6 gradually increases. This allows the toner to be charged more quickly and efficiently.

In order to form a gap between the developing sleeve 4 and the doctor 6 such that the width of the gap becomes narrower toward the downstream side in the agent transport direction, the doctor 6 having the above shape shown in FIG. A wedge-shaped forming member 6a may be attached to the surface on the upstream side in the agent transport direction or the surface on the downstream side in the agent transport direction so as to form a wedge shape between the front end portion in contact with the developer and the surface of the developing sleeve 4. It is possible. For example, FIG. 3 shows an example in which the wedge-shaped forming member 6a is provided on the surface of the doctor 6 on the upstream side in the agent transport direction to form the gap. However, when the above-mentioned gap is formed by attaching another member to the doctor 6 in this way, a step is easily generated between the another member and the doctor 6, and the developer 3 may stay in this portion. is there. If such a stagnation of the agent occurs, the stress is not effectively applied to the developer 3. Therefore, it is desirable that the doctor 3 itself be formed in the above-described shape as in the example of FIG. 2.

Next, a state of occurrence of a difference in development density when the developing device according to the embodiment is used will be described with reference to FIG. FIG. 4 is an explanatory diagram of how the development density difference occurs. FIG. 4A shows an original image to be formed, and FIG.
4B is a developing sleeve 4 of a developing device for forming an image, FIG. 4C is a graph showing a toner charge amount distribution of the developer on the developing sleeve 4 after the image formation, and FIG. This is a developed image when a solid halftone image is formed after formation. As shown in the figure, when an image of a document image having a black stripe on a white background is formed, even if a large amount of new toner is taken in at a portion facing the stripe, the doctor 6 and the developing sleeve 4 shown in FIG. The charging of the new toner efficiently rises in the restricted area C formed in a wedge shape. Thereby, the unevenness of the toner charge amount in the direction orthogonal to the developer conveying direction of the developing sleeve 4 can be suppressed, and thus the unevenness of the developing density can be suppressed. Therefore, even after the toner charge amount is sufficiently ensured even at the portion facing the stripe, the development area A
Therefore, even when a solid halftone image is formed after the image formation, it is possible to form an image without uneven development density.

FIG. 5 is a schematic configuration diagram of a developing device according to a modification. In this developing device, the doctor 6 is provided to be inclined to the upstream side in the agent transport direction so that the gap between the developing sleeve 4 and the doctor 6 is increased as the width of the gap goes downstream in the agent transport direction. It is formed to be narrow. In this case, the density of the developer increases while moving in the agent transport direction along the lower surface 61 of the doctor 6, and a stress is applied to effectively charge the toner. Then, by passing through the portion where the width of the gap between the distal end of the doctor 6 and the surface of the developing sleeve 4 is the narrowest, the gap is regulated to a predetermined amount and supplied to the developing area.

Also in this developing device, the charging of the new toner is efficiently performed while the developer 3 passes through the gap between the doctor lower surface 61 and the developing sleeve 4 immediately after the new toner is taken into the developer 3. stand up. Thereby, the unevenness of the toner charge amount in the direction orthogonal to the developer conveying direction of the developing sleeve 4 can be suppressed, and thus the unevenness of the developing density can be suppressed.

Further, as in the developing device shown in FIG. 5, the doctor 6 is provided so as to be inclined to the upstream side in the agent transport direction so that the width of the gap becomes narrower toward the downstream side in the agent transport direction. For example, unlike the case where the gap is formed by attaching another member to the doctor 6, there is no step between the doctor 6 and the another member, which is likely to occur when the other member is attached. Therefore, since the developer does not stay due to the step, the stress can be effectively applied to the developer 3.

[0025]

According to the first to third aspects of the present invention, the density of the developer passing through the gap between the developer carrier and the developer regulating member gradually increases due to the wedge effect, and the density of the developer applied to the developer is increased. Since the applied stress gradually increases, the charging of the toner in the developer becomes faster and more efficient. Therefore, the unevenness of the toner charge amount in the direction orthogonal to the developer conveying direction of the developing sleeve 4 can be suppressed, so that there is an excellent effect that the unevenness of the development density can be suppressed. In addition, since the toner with insufficient frictional charge can be sufficiently charged while passing through the gap, the toner with insufficient frictional charge is released on the developer carrier side upstream of the gap portion. Unlike the case, there is an effect that the agent can be sufficiently supplied to the development area.

In particular, according to the second and third aspects of the present invention, unlike the case where the gap is formed by attaching a separate member to the developer regulating member, the developer does not stay, and Can be effectively stressed. As a result, the charge of the toner rises more quickly, so that there is an excellent effect that it is possible to more effectively suppress the development of the development.

[Brief description of the drawings]

FIG. 1 is a front view showing a schematic configuration of a developing device according to an embodiment.

FIG. 2 is an enlarged view near a doctor 6 of the developing device.

FIG. 3 is an explanatory view showing a modified example of the doctor 6;

FIGS. 4A to 4D are diagrams illustrating the effect of the developing device.

FIG. 5 is a schematic configuration diagram of a developing device according to a modification.

FIG. 6 is a schematic configuration diagram of an example of a conventional developing device.

FIGS. 7A to 7D are explanatory diagrams of a problem of a conventional developing device.

FIG. 8 is an enlarged view of the vicinity of a doctor 6 of the developing device.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 photoconductor drum 2 casing 3 developer 3a toner 4 developing sleeve 5 magnet roller 6 doctor (developer regulating member) 7 cover member 7a tip of eave portion 8 toner hopper 8a toner supply opening 9 toner agitator 10 developer retention portion

Claims (3)

[Claims] A developer regulating member for magnetically supporting a developer in a developer accommodating portion accommodating a two-component developer containing toner and magnetic particles on a developer carrier having a magnetic field generating means therein. After regulating the amount of the developer carried on the developer carrying member by passing through the gap, the developer is conveyed by rotation to a developing area facing the latent image carrying member of the image forming apparatus, and The toner in the toner container is communicated with the developer container through the toner intake opening, and the stored toner contacts the developer on the developer carrier. In the developing device that takes in the developer, the gap between the developer carrier and the developer regulating member is formed such that the width of the gap becomes narrower as it goes downstream in the developer conveying direction by the developer carrier. A developing device, characterized in that: 2. The developing device according to claim 1, wherein said gap is formed by providing an inclination at a tip of said developer regulating member on a side where developer is regulated. 3. The developing device according to claim 1, wherein said gap is formed by providing said developer regulating member at an upstream side in a developer conveying direction by said developer carrier. .