JP2000206782A - Developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developing device capable of charging toner without giving stress to developer more than needed by improving the stirring efficiency of the toner and carrier, while keeping characteristic that its structure is compact and simple. SOLUTION: An extended part 10 is provided to be L-shape as a whole at the end of a doctor 5. The extended part 10 is formed to be circular arc shape in matching with the shape of the outer peripheral surface of the diameter of a sleeve 3 and extended to the image carrier side. The length of the extended part 10 is longer than the plate thickness of the doctor 5. A regulating gap between the sleeve 3, and the extended part 10 is made equal to or under the regulating gap on a housing part 6 side. Therefore, the time when the developer passes through a very narrow void between the doctor 5 and sleeve 3 becomes long, and the toner and the carrier are strongly drawn for a long time, so that they are completely triboelectrified.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing apparatus using an electrophotographic system used in an image forming apparatus such as a copying machine, a printer, a facsimile, and the like.

[0002]

2. Description of the Related Art FIG. 1 shows a sleeve for carrying and transporting a developer having a first developer amount regulating member and an accommodating portion for scraped-off developer, and a second developer amount regulating member. FIG. 4 is a cross-sectional view illustrating an example of a developing device that changes a contact state between the developer and the toner according to a change in the toner concentration in the developer at an upstream portion of the developing device to change a state of taking in the toner into the developer.

In FIG. 1, reference numeral 1 denotes an image carrier, 2 denotes a developing device, and a rotating cylindrical sleeve 3 and a toner container 4 are provided in the developing device 2. Above the sleeve 3, a doctor 5, which is a first developer amount regulating member, is provided. The doctor 5 is upstream in a direction in which the sleeve 3 conveys the developer (indicated by an arrow in the figure; hereinafter, simply referred to as a developer conveying direction). On the side, a storage section 6 for storing the developer scraped off by the doctor 5 is formed. Further, a pre-doctor 7 as a second developer amount regulating member is provided upstream of the storage section 6 in the developer transport direction. Is provided. On the other hand, an agitator 8 for stirring the toner inside is provided in the toner container 4 so that the stirred toner can be supplied from the supply port 9 to the sleeve 3 side. This developing device changes the state of contact between the developer and the toner in accordance with the change in the toner concentration in the developer at the upstream side of the pre-doctor 7 in the direction of the developer transport, thereby changing the state of the toner taken into the developer. Is to change.

That is, in the developing device 2 of this type, when the toner density in the container 6 is high and the bulk density of the developer is low and the fluidity of the agent is low, the developer is transferred from the container 6 in the developer conveying direction. The developer moves to the upstream side of the pre-doctor 7, and the amount of the developer convection in the upstream portion of the pre-doctor 7 increases. Furthermore, since the fluidity of the developer that moves with the rotation of the sleeve 3 is deteriorated, the flow range is limited to the vicinity of the sleeve 3, and there is no movement on the contact surface with the toner. In such a situation, the toner is not taken into the developer, and the increase in the toner concentration stops. Further, when the toner is consumed and the toner concentration is reduced, the bulk density of the toner is high, the fluidity of the developer is improved, and the amount of the developer at the upstream portion of the predoctor 7 in the developer transport direction is reduced. At the same time, the entrainment of the developer with the sleeve 3 becomes active, the movement of the developer on the contact surface is improved, the toner is taken into the developer, and the toner density increases. By such repetition, the toner concentration is automatically controlled to a substantially constant state.

[0005]

Such a developing device has the advantages of being very small and simple in structure, as can be inferred from FIG. 1, however, the amount of developer that can be accommodated is And there are many problems caused by this.

That is, since the structure is simple and small, it is not possible to secure a space for stably charging the developer by sufficiently stirring the developer after taking in the toner as described above, and to install a stirring member. In some cases, the developer is conveyed to the developing area in a state where charging is unstable. In addition, since the amount of developer is small, in this type of developing device, the toner concentration is generally set higher than that of a normal developing device so as to cope with temporary large consumption of toner to some extent. There is also a problem that the chance of contact of the toner with the carrier is reduced, so that the rise of the charge of the toner in the developer is delayed and the charge amount is also reduced.

In particular, when toner is partially consumed in the axial direction of the sleeve 3 (in the direction perpendicular to the plane of the drawing),
Since the lateral stirring member is not installed, a difference in toner charge amount occurs between a place where toner consumption is large and other parts, and partial density unevenness and background stain may occur in a formed image. There are problems, and it is very difficult to deal with these problems only by improving the developer so as to make the rise of charging faster, and a solution has been desired.

In the developing device disclosed in Japanese Patent Application Laid-Open No. 10-149015, in order to cope with the above-mentioned problem, the shape of the tip of a doctor Are arranged so as to narrow the gap along the rotation direction of the sleeve, so that the stress is increased to improve the rise of charging. Although this configuration seems to be effective at first glance, the narrow width of the sleeve and the rapid application of stress places a large load on the developer, shortens the life of the developer, and further reduces the opportunity for stirring. As a result, the effect cannot be obtained as the value is increased. In addition, various means for improving the stirring efficiency of the developer have been studied and proposed, but no effective means has yet been found to the present inventors.

The present invention solves the above-mentioned conventional problems relating to the amount of developer and the toner concentration under necessary conditions while taking advantage of the structural characteristics of small size and simplicity. It is an object of the present invention to provide a developing device that can satisfy the requirements.

[0010]

According to a first aspect of the present invention, there is provided a developing apparatus comprising: a first developing agent provided on a sleeve which carries and conveys the developer; A regulating member, a storage portion that is located upstream of the first developer amount regulating member in the transport direction of the developer by the sleeve and that stores the scraped-off developer; A second developer amount regulating member located on the upstream side in the transport direction of the developer, wherein the second developer amount regulating member has an intermediate portion of the developer at an upstream portion in the transport direction of the developer by the sleeve of the second developer amount regulating member. In the developing device, which changes the contact state between the developer and the toner in accordance with the change in the toner concentration of the toner to change the state of taking in the toner into the developer, the first developer amount regulating member includes Downstream in material transport direction A portion extending along the outer shape of the sleeve toward a developing area to be placed, and a length dimension of the extended portion along the outer shape of the sleeve is equal to that of the first developer amount regulating member. It is characterized by being longer than the plate thickness.

According to a second aspect of the present invention, the gap between the extended portion and the outer peripheral surface of the sleeve is narrowed toward the downstream side in the transport direction of the developer by the sleeve. .

According to a third aspect of the present invention, the gap dimension is reduced by at least 0.1 mm or more.

According to a fourth aspect of the present invention, the distal end of the extended portion reaches a portion where the perpendicular magnetic force component of the magnetic pole in the developing area is higher than the perpendicular magnetic force component on the housing portion side. Features.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. In the following, portions common to the related art are denoted by the same reference numerals, and redundant description is omitted. FIG. 2 is a sectional view showing a main part of the first embodiment of the developing device according to the present invention. In the present embodiment, the extension portion 10 is provided at the end of the doctor 5 such that the entire portion has an L-shape, with the aim of taking as much time as possible for the rise of the toner charge. And an arcuate shape corresponding to the outer peripheral surface shape of the circular diameter of the sleeve 3 and extended toward the image carrier. The dimension of the extension portion 10 along the outer direction of the sleeve 3 is longer than the thickness of the doctor 5, and the distance between the inner peripheral surface of the sleeve 3 and the sleeve 3, that is, the dimension of the regulating gap, is set to the It is equal to or less than the size of the regulating gap on the side of the storage section 6 where the developer is located, so that the developer contacts the inner peripheral surface of the extension section 10 well.

With this configuration, the time required for the developer to pass through a very narrow gap between the doctor 5 and the sleeve 3 is increased, and the toner and the carrier are strongly squeezed at this portion for a long time. Sufficient triboelectric charging is performed. In addition, since the extension portion 10 is positioned so as to cover the sleeve 3, the extension portion 10 also functions as a seal member for preventing toner from scattering from the agent of the sleeve 3, which is difficult to install in such a small-sized device. It is like that.

FIG. 3 is a sectional view showing a main part of a second embodiment of the developing device according to the present invention. In the present embodiment, the regulating gap between the extended portion 10 and the sleeve 3 is configured to be narrower in the developer transport direction toward the distal end side of the extended portion 10 than the storage portion 6 side. The stress that is given to is gradually increased.

By gradually increasing the stress in this way, it is possible to eliminate the inconvenience caused by suddenly applying a load to the developer in a short time as in the developing device disclosed in JP-A-10-149015 described above. By gradually increasing the stress, a sufficient start-up effect can be obtained, and the life can be prevented from being shortened without imposing an unnecessary load on the developer. However, in order to sufficiently obtain the effect of providing the arc-shaped extending portion 10 on the doctor 5, it is necessary to reduce the particle size of the toner carrier and the resistance of the developer due to the recent trend toward higher image quality. Even in consideration of the reduction of the gap, a taper gap having a difference of 0.1 mm or more between the gap (Amm) on the accommodation section 6 side and the gap (Bmm) on the distal end side of the extension section 10 is required. Is desirable.

FIG. 4 is a sectional view showing a main part of a third embodiment of the developing device according to the present invention. In the present embodiment, the distal end of the extension portion 10 reaches a position where the component of the perpendicular magnetic force of the developing magnetic pole of the sleeve 3 rises and is larger than the magnetic force on the housing portion 6 side of the doctor 5. This is the accommodation part 6
As the agent regulated by the low magnetic force portion (magnetic force a (Gauss: G)) on the side moves on the sleeve 3, the portion where the developing perpendicular magnetic force at the tip of the extension portion 10 becomes large (magnetic force b ( Gauss: G)), and the so-called magnetic brush ears rise with the rise of the magnetic force.

At this time, the raised ears come into strong contact with the extended portion 10 due to the effect of magnetism, receive a large stress, and the toner is strongly friction-charged, so that a sufficient amount of charge can be obtained. This load stress is not much greater than the stress that the developer receives from the image carrier in the development area, has little effect on the life of the developer, and has a sufficient level of load for charging. It can be said that there is.

[0020]

As described above, in the developing device according to the first aspect, the first developer amount regulating member provided on the sleeve that carries and transports the developer is provided with the direction of transport of the developer by the sleeve. A portion extending along the outer shape of the sleeve toward the developing region located on the downstream side, and the length of the extended portion along the outer shape of the sleeve is set to a first developer amount regulating member. Longer than the plate thickness dimension, it is easy to increase the time for the developer to pass through the narrow gap, increase the toner and carrier agitation efficiency, and increase the toner Charge can be applied to the replenished toner while taking advantage of its features such as small size, simplicity, and low cost. Maintain That there is an effect that can be achieved.

According to a second aspect of the present invention, as described above, the gap between the extended portion of the doctor and the outer peripheral surface of the sleeve is narrowed toward the downstream side in the direction in which the developer is transported by the sleeve. In addition to the above-mentioned common effects, the effect of improving the start-up efficiency of toner charging can be obtained.

According to a fourth aspect of the present invention, as described above, the leading end of the extended portion reaches the portion where the perpendicular magnetic force component of the magnetic pole in the developing region is higher than the perpendicular magnetic force component on the housing portion side. In addition to the above-mentioned common effects, further charging efficiency can be achieved by using the perpendicular magnetic force of the developing magnetic pole of the sleeve. There is an effect that an unnecessary strong load stress is not applied and a bad influence on the life of the agent is not generated.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating an example of a conventional developing device.

FIG. 2 is a cross-sectional view illustrating a main part of a first embodiment of the developing device according to the present invention.

FIG. 3 is a sectional view showing a main part of a second embodiment of the developing device according to the present invention.

FIG. 4 is a sectional view showing a main part of a third embodiment of the developing device according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Image carrier 2 Developing device 3 Sleeve 4 Toner container 5 Doctor 6 Storage part 7 Predoctor 8 Agitator 9 Supply port 10 Extension part A, B gap a, b Magnetic force

Claims (4)

[Claims] A first developer amount regulating member provided on a sleeve for carrying and transporting the developer, and a first developer amount regulating member provided upstream from the first developer amount regulating member in a direction in which the developer is transported by the sleeve. A storage portion for storing the scraped-down developer, and a second developer amount regulating member positioned upstream from the storage portion in a direction in which the developer is conveyed by the sleeve. The contact state between the developer and the toner is changed according to the change in the toner concentration in the developer at the upstream portion in the transport direction of the developer by the sleeve of the developer amount regulating member of No. 2, and the toner is taken into the developer. In the developing device for changing a state, a portion in which the first developer amount regulating member extends in accordance with an outer shape of the sleeve toward a developing region located on a downstream side in a conveying direction of the developer by the sleeve. And above the extension A developing device, wherein a length dimension along an outer shape of the sleeve is longer than a plate thickness dimension of the first developer amount regulating member. 2. The developing device according to claim 1, wherein a gap dimension between the extended portion and the outer peripheral surface of the sleeve is reduced toward a downstream side in a conveying direction of the developer by the sleeve. 3. The gap size is at least 0.1 m.
3. The developing device according to claim 2, wherein the width is at least m. 4. The developing device according to claim 2, wherein the distal end of the extended portion reaches a portion where the perpendicular magnetic force component of the magnetic pole in the developing area is higher than the perpendicular magnetic force component on the housing portion side. 3. Developing device.