JP2004151326A - Developer conveyance member - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developer conveyance member for effectively preventing occurrence of irregular screw pitch. <P>SOLUTION: The developer conveyance members 5 and 6 for spirally winding a blade member around a center shaft member 14 have a conveyance blade part 15 having a blade face in which the angle of the blade face of a developer conveyance direction for a rotation center line 13 of the developer conveyance member is the largest; and at least one or more mass increasing blade parts 16 in which the angle of the blade face of the developer conveyance direction for the rotation center line 13 of the developer conveyance member is smaller than the angle of the blade face of the conveyance blade part. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a developer conveying member for conveying a developer to a developing unit.
[0002]
[Prior art]
2. Description of the Related Art As a developing device of an image forming apparatus for performing electrophotographic development, a two-component developing device having very good chargeability to toner has been widely used. FIG. 13 is a top view of the developing device, and FIG. 14 is a cross-sectional view illustrating an example of the two-component developing device.
[0003]
As shown in the figure, a developer container 10 stores a developer D composed of a toner and a carrier. An opening is provided in a portion of the developer container 10 which is in close proximity to the photosensitive drum 1, and a developing sleeve 2 which is a developer carrier is provided in the opening. The developing sleeve 2 is a hollow non-magnetic metal sleeve and includes a magnet roller 3 as a magnetic field generating means.
[0004]
Reference numerals 5 and 6 denote developer conveying members (A screw 5 and B screw 6), which are screws in which blade members are spirally wound at a constant pitch around a cylindrical central shaft member. The A screw 5 and the B screw 6 are arranged substantially in parallel, and an inner wall 7 is provided between the A screw and the B screw to partition the developer so that it does not flow. There are no inner walls at both longitudinal ends, so that the developer can move between the A and B screws. Since the A screw and the B screw convey the developer in opposite directions, when each screw rotates, the developer circulates inside without interruption as shown by the arrow.
[0005]
The developer supplied by the A screw 5 is supplied to the developing sleeve 2 by the magnetic force of the magnet roller 3, and is conveyed with rotation. Reference numeral 4 denotes a developer regulating member, and a uniform amount of the developer is formed on the developing sleeve 2 by regulating the amount of the developer on the developing sleeve 2 to an appropriate amount. The magnetic brush of the developer carried on the developing sleeve 2 comes into contact with the photosensitive drum 1 rotating in the developing section, and the electrostatic latent image on the photosensitive drum 1 is developed.
[0006]
FIG. 15 is an external view of a conventional screw, and FIG. 16 is a cross-sectional view taken along a plane passing through a rotation center line of the conventional screw. The transport direction of the developer in this figure is to the left. Reference numeral 13 denotes a rotation center line, reference numeral 14 denotes a center shaft member, and reference numeral 15 denotes a spirally wound blade. As shown in the figure, the angle formed by the blade surface (shown by oblique lines in the drawing) in the transport direction with respect to the rotation center line is referred to as an angle θ. The angle .theta. Is closer to the perpendicular, the greater the developer conveying force. Therefore, the angle .theta. Is usually set to about 70 to 80.degree. In consideration of the draft angle of the mold.
[0007]
[Problems to be solved by the invention]
However, the conventional configuration may have the following problems.
[0008]
FIG. 17 is an explanatory view schematically showing a state of transporting the developer by a conventional screw. As the screw rotates, the developer receives a force that is pushed in the traveling direction by the blade, so that the developer is biased toward the transport direction surface side of the blade. Since the amount decreases as the distance from the blade increases, each blade is conveyed in the state shown in FIG.
[0009]
Therefore, looking at the distribution of the developer in the longitudinal direction, a large portion and a small portion (so-called unevenness) are formed in accordance with the blade pitch. Then, since the screw rotates, the developer is transported in the longitudinal direction, and the unevenness of the developer becomes an oblique density shading and appears on the image. This image defect is hereinafter referred to as screw pitch unevenness. Screw pitch unevenness is extremely likely to occur in a two-component developing device in which a developing sleeve and a developer conveying screw are arranged close to each other.
[0010]
Therefore, screw pitch unevenness is prevented by optimizing each configuration, such as the arrangement relationship between the developing sleeve 2 and each screw, the magnetic pole relationship of the magnet roller 3 in the developing sleeve 2, and the compression state of the developer in the regulating portion. It was difficult to completely prevent the developer conveyed by the screw from being distributed unevenly at the pitch of the screw blades.
[0011]
Further, in the two-component developing device, since the toner concentration of the developer fluctuates depending on the balance between toner consumption and replenishment, the amount of the developer may increase or decrease accordingly, and the amount of the developer in the developing device decreases. However, it is difficult to completely prevent screw pitch unevenness, no matter how the configuration is optimized.
[0012]
Conventionally, there has been a device that devises the shape and the number of strips of the developer conveying member (for example, JP-A-10-221937 and JP-A-2002-31940). There was no object for solving the screw pitch unevenness.
[0013]
Accordingly, an object of the present invention is to provide a developer conveying member that can effectively prevent the occurrence of screw pitch unevenness.
[0014]
[Means for Solving the Problems]
In order to achieve the above object, a representative configuration of the present invention is a developer transport member that spirally winds a blade member around a central shaft member and supplies a developer to a developer carrier. A transport blade having a blade surface having the largest angle of the blade surface in the developer transport direction with respect to the rotation center line of the transport member, separately from the transport blade portion, with respect to the rotation center line of the developer transport member. At least one or more bulky blades, wherein the angle of the blade surface in the developer transport direction is smaller than the angle of the blade surface of the transport blade.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
(1st Embodiment)
FIG. 5 is an explanatory diagram of the image forming apparatus according to the present embodiment. 1 is a photosensitive drum as an image carrier, 20 is a charging device, 21 is an exposure device for forming a latent image on the photosensitive drum, 11 is a developing device for visualizing the latent image with toner, and 9 is a developing device. A developer replenishing device for replenishing toner, 22 a transfer device for transferring the visualized toner image onto a transfer material, 23 a fixing device for fixing the toner image transferred on the transfer material, and 24 a photosensitive drum This is a cleaning device for removing transfer residual toner remaining on the surface.
[0016]
The developing device includes a developer container 10 for storing a developer, and stores a developer D in which toner particles and magnetic carrier particles are mixed. As the toner, a known toner in which a colorant, a charge control agent, and the like are added to a binder resin can be used. In the present embodiment, a toner having a volume average particle size of 5 to 15 μm is used. On the other hand, as the magnetic carrier, a ferrite carrier, a resin-coated one or the like is suitably used, and the average particle size is preferably 15 to 70 μm. A developer replenishing device 9 is provided above the developer transporting member 6, and an amount of toner corresponding to the consumed toner is dropped and replenished into the developer container 10 through the replenishing port 8, so that the amount of The developer is always kept at a constant toner concentration.
[0017]
Next, the screw which is the developer conveying member according to the present embodiment will be described. 1 and 2 are cross-sectional views taken along a plane passing through the rotation center line of the screw according to the present embodiment, and are diagrams for explaining the angle of the blade and the length of the blade. The transport direction of the developer in this figure is to the left.
[0018]
In the configuration of the present invention, in addition to the transport spiral blade 15 serving as the transport blade portion being spirally wound around the screw shaft, a bulky spiral blade 16 serving as the bulky blade portion is separately provided immediately after the transport spiral blade 15. (Corresponding to Embodiments 1 and 4).
[0019]
As shown in FIGS. 1 and 2, the angle between the blade surface in the transport direction of the transport spiral blade 15 and the center line of the shaft is (θ1), the height of the blade is (H1), and the axial length of the blade. Is defined as (L1), the angle between the blade surface in the conveying direction of the bulky spiral blade and the center line of the shaft is (θ2), the height of the blade is (H2), and the length of the blade in the axial direction is (L2). And The outer diameter including the blades of the screw was 14 mm, the diameter of the central shaft member was 6 mm, the pitch in the longitudinal direction of the blades was 15 mm, θ1 = 70 °, H1 = 4 mm, L1 = 3 mm, and L2 = 5 mm.
[0020]
With the condition of the conveying spiral blade 15 fixed, an image-drawing test was performed by increasing the height H2 of the spiral spiral blade 16 by several levels. The result is shown in FIG. From these results, it was confirmed that the screw pitch unevenness was improved by adding the spiral blade 16 to the transport spiral blade 15 by increasing the volume. The reason will be described with reference to FIG.
[0021]
In a configuration having only the transport spiral blade 15 as in the conventional technique, the developer is reduced at a position immediately after the transport spiral blade 15 so that a gap is easily formed. On the other hand, in the present embodiment, the bulk of the developer D is increased by applying a force exerted on the developer D in a direction substantially perpendicular to the center shaft member 14 by adding the bulky spiral blade 16. By increasing the bulk of the developer D in this manner, it is possible to fill a gap immediately after the transport spiral blade 15. For this reason, it seems that screw pitch unevenness can be effectively prevented.
[0022]
Further, as shown in FIG. 3, it can be seen that the height H2 of the bulky spiral blade 16 has a suitable range, and that the effect is reduced if the height H2 is too large or too small. If H2 is too small, the effect of increasing the bulk of the developer is reduced, and the effect of preventing screw pitch unevenness is reduced. On the other hand, if H2 is too large, the bulk increases and a gap portion with a small amount of developer is formed immediately after the spiral blade 16, and even if the gap immediately after the transport spiral blade 15 is filled, a new developer gap is generated. It is because.
[0023]
In consideration of these points, it is desirable that the upper limit of the height of the bulky spiral blade 16 be within H2 <H1 × 0.7 (corresponding to the second embodiment). In this case, the optimum angles of θ2 are 5 ° <θ2 <40 °, 60 ° <θ1 (corresponding to the third embodiment), and more preferably, 10 ° <θ2 <30 ° and 60 ° <θ1.
[0024]
In the examination of the present embodiment, the above results were obtained because the screw diameter and the pitch were fixed, but if these shapes are changed, the preferable value of the angle θ is slightly changed. However, by providing the increased spiral blade 16, the gap immediately after the transport spiral blade can be filled, and the original function and effect that screw pitch unevenness can be effectively prevented does not change.
[0025]
As described above, in the present embodiment, the transport state of the developer to be transported is improved substantially horizontally by providing the bulky spiral blade 16 immediately after the transport spiral blade 15. As a result, the supply unevenness of the developer D to the developing sleeve 2 and the unevenness of the compression in the regulated portion, and the toner density of the developer D transported by the screw and the developed developer returned from the developing sleeve 2 And any factors that cause image unevenness due to screw pitch can be reduced. Thus, the screw pitch unevenness image can be improved.
[0026]
(2nd Embodiment)
In the first embodiment, the configuration in which one bulky spiral blade 16 is separately provided immediately after the transport spiral blade 15 has been described. However, in the present embodiment, another bulky spiral blade is added and two The configuration provided will be described. FIG. 6 is an external view of the screw according to the present embodiment, and FIGS. 7 and 8 are cross-sectional views taken along a plane passing through a rotation center line of the screw according to the present embodiment. FIG. The transport direction of the developer in this figure is to the left.
[0027]
The outer diameter of the screw including the blade was 14 mm, the diameter of the central shaft member was 6 mm, the pitch in the longitudinal direction of the blade was 15 mm, θ1 = 70 °, H1 = 4 mm, and L1 = 3 mm. As described in the first embodiment, the bulky spiral blade has H2 = 2 mm and L2 = 5 mm.
[0028]
In this state, a bulky spiral blade 17 as another bulky blade portion was installed immediately after the bulky spiral blade 16 of the first embodiment. Since the blade surface in the transport direction of the bulky spiral blade 17 newly provided in the second embodiment is located very close to the blade surface in the transport direction of the transport spiral blade 15, the blade surface in both transport directions is set to the point P. (See FIG. 8) to form a shape having two surfaces at different angles. Under these conditions, the height H3 was varied at several levels in order to vary the angle of the increased spiral blade 17, and the effects on screw pitch unevenness and developer transportability were examined. The result is shown in FIG. From this result, it was confirmed that the screw pitch unevenness was improved by adding the bulky spiral blade 17. The reason will be described with reference to FIG.
[0029]
As shown in FIG. 10, in the present embodiment, by providing the increased spiral blade 17, it is possible to fill the gap of the developer immediately after the transport spiral blade 15, as in the first embodiment, A force exerted on the developer in a direction substantially perpendicular to the rotation center line can also be applied to the intermediate point between the transport spiral blade 15 and the transport spiral blade 15 where the developer height tends to decrease. This makes it possible to achieve a very uniform developer height as a whole. Further, since the transport amount is not reduced only by increasing the apparent bulk of the developer, if the developer is used in a suitable range, the developer transportability is not hindered.
[0030]
As shown in FIG. 9, it has been found that the height H3 of the bulky spiral blade 17, that is, the angle θ3 has a suitable range, and that the effect is reduced if the height H3 is too large or too small. If H3 is too small, the effect of increasing the bulk of the developer is reduced, and the effect of preventing screw pitch unevenness is reduced. On the other hand, if H3 is too large, the effective area of the transport spiral blade 15 located immediately after the spiral blade 17 is reduced, so that the developer transportability is reduced and the density is easily reduced.
[0031]
Taking these facts into consideration, a preferable range of the bulky spiral blade 17 is H3 <H1 × 0.5. The optimum angle of θ3 at this time is 5 ° <θ3 <40 °, and more preferably, 10 ° <θ3 <30 °.
[0032]
As described above, in the present embodiment, since two bulky spiral blades are provided, not only can the gap immediately after the transport spiral blade be filled as in the first embodiment, but also the developer height tends to decrease. By applying a force that acts on the developer in the direction perpendicular to the rotation center line at the intermediate point between the transport spiral blade and the transport spiral blade, it is possible to achieve a very uniform developer height as a whole It became.
[0033]
As a result, the uneven supply of the developer to the developing sleeve, and the uneven compression in the regulation portion accompanying the unevenness, and the difference in the toner concentration between the developer conveyed by the screw and the developed developer returned from the developing sleeve, etc. Since it is possible to reduce all causes of image unevenness due to screw pitch, it is possible to improve an image of screw pitch unevenness.
[0034]
Up to this point, the description has been given of the case where the bulky spiral blade is composed of two. As shown in FIG. 11, a bulky spiral blade as three or more bulky blade portions (here, the bulky spiral blade 18 is added), or The above configuration may be used. Thus, by disposing a plurality of bulking spiral blades in addition to the transporting spiral blades, the central shaft member is covered by the transporting spiral blades and the bulking spiral blades, and the screw is substantially removed without exposing the central shaft member. Is constituted by a surface inclined in the transport direction (corresponding to the fifth embodiment). As a result, the force in the transport direction and the force exerted in the direction perpendicular to the rotation center line can be applied to the developer existing everywhere on the screw, and the height of the developer can be kept more uniform.
[0035]
In the examination of the present embodiment, the above result was obtained because the screw diameter and the pitch were fixed, but if the shape is changed, the preferable value of the angle θ is slightly changed. However, by providing the bulky spiral blade which is a feature of the present invention, the gap immediately after the transport spiral blade or the gap between the transport spiral blade and the intermediate point between the transport spiral blade can be filled, so that the screw pitch unevenness is reduced. This does not change the original function and effect that can be prevented.
[0036]
(Third embodiment)
This embodiment is an example in which the second embodiment is mounted on a color image forming apparatus on which a plurality of developing devices are mounted. FIG. 12 shows a four-drum type (in-line) printer in which images developed on four image carriers are continuously multiplex-transferred to an intermediate transfer belt 40 as an intermediate transfer member to obtain a full-color print image.
[0037]
In FIG. 12, an endless intermediate transfer belt 40 is suspended by a driving roller 41, a tension roller 42, and a secondary transfer opposing roller 43, and rotates in the direction of the arrow in the figure.
[0038]
During the rotation process, the photosensitive drum 1 for developing the yellow toner is uniformly charged to a predetermined polarity and potential by a primary charging roller as a charging device 20, and then the image exposure means (not shown) (color of the color original image) The target color image yellow by receiving image exposure by a separation / imaging exposure optical system, a laser scanning scanning exposure system that outputs a laser beam modulated in accordance with a time-series electric digital pixel signal of image information, etc. An electrostatic latent image corresponding to the component image is formed. Next, the electrostatic latent image is developed by the first developing device 11 (yellow developing device), and the bias is transferred onto the transfer belt. Thus, the yellow, magenta, cyan, and black images are sequentially superimposed on the intermediate transfer body 40, and a full-color image is formed.
[0039]
The four-color full-color image formed on the intermediate transfer belt 40 is then collectively transferred to a transfer material by a secondary transfer roller 44, and is fused and fixed by a fixing device (not shown) to obtain a color print image. The secondary transfer residual toner remaining on the intermediate transfer belt 40 is blade-cleaned by the intermediate transfer belt cleaner 45 to prepare for the next image forming process.
[0040]
In such a color image forming apparatus, unevenness of fixed pitch such as screw pitch unevenness tends to be amplified and deteriorated in level due to color overlap. However, the configurations of the first and second embodiments according to the present invention are as follows. It is very effective and exerts a great effect even in such a color image forming apparatus.
[0041]
(Other embodiments)
In the above-described embodiment, an example has been described in which the photosensitive drum 1 and the process means that acts on the photosensitive drum 1 are arranged separately. However, the present invention is not limited to this, and the photosensitive drum 1 and the At least the developing device 11 may be integrally formed as a cartridge as an operating process unit, and may be a process cartridge detachably mounted to the image forming apparatus. As a process cartridge, for example, in addition to the photosensitive drum 1 and the developing device 11, any or all of the charging device 20, the exposure device 21, and the cleaning device 24 can be arranged in one frame to form a process cartridge. The process cartridge can be attached to and detached from the apparatus main body by the user himself, and as a result, the user can perform maintenance on the apparatus main body by himself (corresponding to the eighth embodiment).
[0042]
Further, the image forming apparatus according to the present invention may take the form of a copying machine, a facsimile machine, or the like, in addition to the printer described above.
[0043]
[Embodiment]
Next, examples of embodiments of the present invention will be listed below.
[0044]
[Embodiment 1]
In a developer transporting member that spirally winds the blade member around the central shaft member and supplies the developer to the developer carrier,
A transport blade having a blade surface having the largest angle of the blade surface in the developer transport direction with respect to the rotation center line of the developer transport member,
Apart from the transport blade, the angle of the blade surface in the developer transport direction with respect to the rotation center line of the developer transport member is at least one or more bulks smaller than the angle of the blade surface of the transport blade. And an additional blade portion.
[0045]
[Embodiment 2]
In the developer transport member according to the first embodiment,
The distance from the central shaft member of the developer transport member to the tip of the outer diameter of the transport blade is H1,
When the distance from the central shaft member of the developer conveying member to the tip of the outer diameter of the bulky blade portion is Hn (n = 2, 3,...),
Hn <H1 × 0.7,
A developer conveying member, characterized in that:
[0046]
[Embodiment 3]
In the developer transport member according to the embodiment 1 or 2,
The angle formed by the blade surface in the transport direction of the transport blade portion with respect to the rotation center line is θ1,
When the angle formed by the blade surface in the transport direction of the bulky blade portion with respect to the rotation center line is θn (n = 2, 3,...),
5 ° <θn <40 °, 60 ° <θ1,
A developer conveying member, characterized in that:
[0047]
[Embodiment 4]
The developer conveying member according to any one of Embodiments 1 to 3,
A developer transporting member, wherein the bulky blade is disposed without an interval upstream of the transport blade in the transport direction.
[0048]
[Embodiment 5]
The developer conveying member according to any one of Embodiments 1 to 4,
A developer conveying member, wherein most or all of the central shaft member is covered by the conveying blade portion and the bulky blade portion.
[0049]
[Embodiment 6]
A developing device comprising: a developer; an image carrier; a developer carrier for supplying the developer with the image carrier; and a developer carrying member for carrying the developer to the developer carrier. A developing device, wherein the transport member is the developer transport member according to any one of the first to fifth embodiments.
[0050]
[Embodiment 7]
The developing device according to embodiment 6, wherein
The developing device according to claim 1, wherein the developer is a two-component developer including a toner and a carrier.
[0051]
[Embodiment 8]
An image carrier, and a process unit acting on the image carrier, a process cartridge configured to be detachable from the image forming apparatus,
A process cartridge comprising at least the developing device according to the sixth or seventh embodiment as the process means.
[0052]
【The invention's effect】
As described above, in the present invention, since the central shaft member of the developer transport member includes the transport blade and the bulky blade, the developer is transported in a substantially horizontal state. For this reason, it is possible to prevent a portion where the amount of the developer supplied in the longitudinal direction of the developer carrier is large and a portion where the amount is small, and it is possible to effectively prevent the occurrence of screw pitch unevenness.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view taken along a plane passing through a rotation center line of a screw according to a first embodiment.
FIG. 2 is a sectional view taken along a plane passing through the rotation center line of the screw according to the first embodiment.
FIG. 3 is a diagram showing a result of an image-drawing test in which the height of a bulky spiral blade 16 is used as a parameter.
FIG. 4 is a view for explaining effects of the first embodiment.
FIG. 5 is a diagram illustrating an image forming apparatus according to the first and second embodiments.
FIG. 6 is an external view of a screw according to a second embodiment.
FIG. 7 is a sectional view taken along a plane passing through a rotation center line of the screw according to the second embodiment.
FIG. 8 is a sectional view taken along a plane passing through the rotation center line of the screw according to the second embodiment.
FIG. 9 is a diagram showing a result of an image-drawing test in which the height of a bulky spiral blade 17 is used as a parameter.
FIG. 10 is a view for explaining effects of the second embodiment.
FIG. 11 is a sectional view showing a modification of the second embodiment.
FIG. 12 is an explanatory diagram of an image forming apparatus equipped with a plurality of developing devices according to a third embodiment.
FIG. 13 is a top view of a conventional developing device.
FIG. 14 is a sectional view showing an example of a conventional two-component developing device.
FIG. 15 is an external view of a conventional screw.
FIG. 16 is a cross-sectional view taken along a plane passing through a rotation center line of a conventional screw.
FIG. 17 is an explanatory view schematically showing a state in which a developer is transported by a conventional screw.
[Explanation of symbols]
D: developer, 1: photosensitive drum, 2: developing sleeve,
3: magnet roller, 4: developer regulating member, 5: developer conveying member,
6: developer transport member, 7: inner wall, 8: supply port, 9: developer supply device,
10: developer container, 11: developing device, 13: rotational center line, 14: central shaft member,
15: conveying spiral blade, 16: bulking spiral blade, 17: bulking spiral blade,
18: spiral blade, 20: charging device, 21: exposure device, 22: transfer device,
23 ... fixing device, 24 ... cleaning device,
Reference numeral 40: intermediate transfer belt, 41: drive roller, 42: tension roller, 43: secondary transfer facing roller, 44: secondary transfer roller, 45: intermediate transfer belt cleaner,

Claims (1)

In a developer transport member that spirally winds the blade member around the central shaft member and supplies the developer to the developer carrier,
A transport blade having a blade surface having the largest angle of the blade surface in the developer transport direction with respect to the rotation center line of the developer transport member,
Apart from the transport blade, the angle of the blade surface in the developer transport direction with respect to the rotation center line of the developer transport member is at least one or more bulks smaller than the angle of the blade surface of the transport blade. And an additional blade portion.

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