JP2002132040A - Image forming device and method of developing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem of an image unevenness being attributable to the pitch of groove by the conventional means of improving transportability of the developer by providing the number of grooves on the developer carrying surface of the developer carrier. SOLUTION: For this image forming device, the number of grooves are provided on the developer carrier, so as to establish a relation between traveling speed Vs of the developer carrier, and the pitch P (mm) of the grooves to the effect that the pitch P is >=2 times that of Vs/Vp.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a developing technique of an image forming apparatus for forming an image on a recording material by an electrophotographic method.

[0002]

2. Description of the Related Art In a developing device of an image forming apparatus for forming an image by an electrophotographic method, a developer carrier is arranged to face an image carrier carrying an electrostatic latent image, and the developer carrier is moved. As a result, the developer is generally transported to the development area to perform the development.

[0003] In order to give the developer carrying member a good developer carrying ability, the developer carrying surface is often subjected to a surface roughening treatment such as a metal spraying treatment or a sand blasting treatment.

[0004]

Although metal spraying is a means capable of forming a developer carrying surface having a desired conveying ability and durability, it has a problem of high cost. On the other hand, sandblasting is low in cost, but has a problem in that the durability of the developer carrier formed by this process is low.

[0005] Conventional methods for providing the developer carrying ability to the developer carrier have such advantages and disadvantages. For this purpose, a means is employed in which a groove is formed on the developer carrying surface by cutting, extruding, casting, forging, or the like. This means has a feature that a relatively low cost and a good developer carrying capacity can be obtained.

However, in the means for providing a groove on the developer carrying surface, the amount of developer carried varies periodically in accordance with the pitch of the groove. There is a problem that image quality is deteriorated due to the occurrence of uneven density.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problem in a method of providing a groove on a developer carrying member, and to prevent a decrease in image quality due to density unevenness at a relatively low cost.

[0008]

The above-mentioned object of the present invention is achieved by the following inventions.

1. An image forming apparatus comprising: an image carrier and a developer carrier that is disposed to face the image carrier, moves in the same direction as the image carrier by rotation, and conveys the developer to a development area. The carrier has a developer carrying surface provided so that grooves in the rotation axis direction are uniformly distributed over the entire surface, and the pitch P (mm) of the grooves is Vp
(Mm / sec) is the moving speed of the image carrier, Vs (m
m / sec) as the moving speed of the developer carrying member,
An image forming apparatus characterized in that Vs / Vp is twice or less.

[0010] 2. ^2. The image forming apparatus according to claim 1, wherein an amount W of the developer conveyed to the developing area by the developer carrier is 70 mg / cm ² or more.

3. 3. The image forming apparatus according to 2, wherein the image forming apparatus includes a regulation unit that regulates the developer conveyed by the developer carrier.

4. A developer carrying member that carries a developer with respect to the image carrying member is disposed opposite to the image carrying member, and the developer carrying member is rotated in the same direction with respect to the image carrying member so that the developer carrying member is disposed on the image carrying member. In a developing method for developing an electrostatic latent image, the developer carrying member has a developer carrying surface provided so that grooves in a rotation axis direction are uniformly distributed over the entire surface, and the pitch of the grooves is P (mm) is Vp (mm / s)
ec) is the moving speed of the image carrier, Vs (mm / sec).
When c) is the moving speed of the developer carrier, Vs / V
p is twice or less of p.

5. The developing method according to claim 4, wherein an amount W of the developer conveyed to the developing area by the developer carrier is 70 mg / cm ² or more.

6. 6. The developing method according to the above item 5, wherein the regulating means regulates the developer conveyed by the developer carrying means.

[0015]

FIG. 1 shows an image forming apparatus according to an embodiment of the present invention.

A charging device 2, an exposing device 3, a developing device 4, a transfer device 5, a separating device 6, and a cleaning device 9 are arranged around the photoreceptor 1 as an image carrier. In the lower part of the apparatus, there are disposed a registration roller 10 for transporting the recording paper to the transfer device 5, a transport belt 7 for transporting the recording paper separated from the photoreceptor 1 by the separating device 6, and a fixing device 8.

As the image carrier, a negatively chargeable OPC photosensitive member having an organic photoconductive layer formed on a metal drum substrate is desirable, but the present invention is not limited to this, and any known photosensitive member can be used. As the charging device 2, a scorotron charger having a control electrode and a discharge electrode, a corotron charger having a discharge electrode, or a contact charger such as a roller charger or a brush charger is used. The exposure device 3 includes a scanning exposure device including a laser diode and a scanning optical system, a scanning exposure device including a light emitting diode array,
A well-known exposure device such as a scanning projection optical system for projecting an image of a document thereon is used to scan the photosensitive member 1 to perform image exposure.

The developing device 4 uses a two-component developer, applies a developing bias having the same polarity as the electrostatic latent image on the photoconductor 1 to the developer carrier, and negatively charges the exposed portion on the photoconductor 1. A developing device that performs reversal development by attaching toner is desirable, but is not limited to this. As the developer, either a two-component developer or a one-component developer can be used. Further, as the toner constituting the developer, either a non-magnetic toner or a magnetic toner can be used. Further, it is possible to use a developing device that applies a developing bias having a polarity opposite to that of the electrostatic latent image on the photoconductor 1 to the developer carrier to perform regular development. Any of the developing methods can be used.

The transfer device 5 is preferably a corotron charger having a discharge electrode and positively charging the recording paper, but any known device such as a roller transfer device may be used. As the separation device 6, any known separation device having a discharge electrode, such as a corotron charger for removing electricity from the recording paper, is used.

At the time of image formation, the photosensitive member 1 rotates as shown by an arrow A, and in accordance with the rotation of the photosensitive member 1, charging by the charging device 2, image exposure by the exposure device 3, and development by the developing device 4 are performed. 1, a toner image is formed. The formed toner image is transferred to the recording paper by the transfer device 5 and then fixed to the recording paper by the fixing device 8. Transfer device 5
The photoreceptor 1 that has passed the transfer position where the image is transferred is cleaned by the cleaning device 9 to remove the residual toner.

The developing device 4 has a unit structure in which the following components are provided in a frame 40.

A developing sleeve 41 as a developer carrier is rotatably arranged opposite to the photoreceptor 1. Photoconductor 1
Between the developing sleeve 41 and the developing sleeve 41 (the shortest distance between the surface of the photoreceptor 1 (electrostatic latent image holding surface) and the surface of the developing sleeve 41 (developer holding surface)) and the closest distance giving the developing interval A development region G centering on the position is formed.

The developing interval is 0.1 mm to 1.0 mm
Is preferable. Inside the developing sleeve 41, a magnet 42 having magnetic poles N1, S1, S2, N2, and S3 is fixedly arranged.

When the developing interval is 0.1 mm or less, the developing sleeve 41 is susceptible to mechanical fluctuations such as run-out, and the quality of a halftone image is degraded. When the developing interval is 1.0 mm or more, the effect of the developing sleeve 41 as a counter electrode is reduced, and the latent image such as a fine line is disturbed.

A developer DV composed of a toner and a carrier is stirred and conveyed by the rotation of the stirring and conveying screws 46 and 47, and has four radial wings formed over the entire developing width direction. Is supplied to the developing sleeve 41 by an impeller-shaped transport member 45 that transports the developer. The developer DV on the developing sleeve 41 is regulated by regulating means 44 that forms a constant interval between the developer DV and the developing sleeve 41 over the entire developing width direction, and a uniform developer layer DVL (see FIG. 2) is formed.

As shown in FIG. 2 showing the rotation direction of the photosensitive member 1 and the developing sleeve 41, in the image formation, the photosensitive member 1 rotates at the linear velocity on the surface, that is, the moving velocity Vp as indicated by an arrow A. The developing sleeve 41 rotates at the linear speed of the developer carrying surface, that is, the moving speed Vs, as shown by the arrow B, and the electrostatic latent image on the photoconductor 1 is developed to form a toner image T. As shown in FIG. 3 showing the developing sleeve 41 in an unfolded state,
On the developer carrying surface of the developing sleeve 41, the grooves MZ in the rotation axis direction are formed so as to be uniformly distributed at a pitch (interval between grooves) P (mm). The developing sleeve 41 is made of aluminum or non-magnetic SUS, and is cut, extruded,
A groove MZ extending parallel to the rotation axis direction of the developing sleeve 41 is formed by casting, forging, or the like, as shown in FIG. The developer DV is generated by the magnetic attraction force of the magnet 42 and the developing sleeve 41.
Is conveyed to the developing area G by the frictional force of the surface of the developer.

As a developer carrier, as shown in FIG. 1, in addition to a developing sleeve in which a magnet 42 is disposed inside,
It is also possible to use only a rotating magnet. When the developer carrying member is constituted only by the magnet, the groove MZ is formed on the surface of the magnet.

As shown in FIG. 4, the groove MZ formed in the developing sleeve 41 has various shapes such as a concave shape shown in FIG. 4A, a V shape shown in FIG. 4B, and a U shape shown in FIG. It can be shaped. Further, by changing the depth E of the groove MZ and the opening angle θ indicating the relationship between the width and the depth of the groove MZ, it is possible to adjust the characteristics of carrying and transporting the developer DV.

The pitch P (mm) of the groove MZ is defined as Vp (mm
/ Sec) is the moving speed of the photosensitive member 1 as an image carrier, V
When s (mm / sec) is the moving speed of the developing sleeve 41 as a developer carrying member, by setting the moving speed to twice or less of Vs / Vp, a halftone can be uniformly developed and a clear image can be formed. Can be. Note that this condition is such that the image carrier (photoconductor 1) and the developer carrier (developing sleeve 4)
1) are conditions for moving in the same direction as indicated by A and B.

If the pitch P is larger than the upper limit of the above-mentioned condition, periodic density unevenness is conspicuous in the halftone, and the image quality deteriorates.

When the pitch P (mm) is not more than 1.5 times Vs / Vp, a particularly good image is formed.

By setting the pitch P to 1.5 times or less of Vs / Vp, not only visual observation but also non-uniform density due to microscopic observation can be prevented.

Furthermore, when the amount W of the developer conveyed to the developing area G by the developer carrier is 70 mg / cm ² or more, a particularly good image is formed. When the amount W of the conveyed developer is smaller than the lower limit of the above-mentioned condition, there is a tendency that periodic density unevenness due to the influence of the groove MZ of the developer carrier is conspicuous and the image quality tends to be reduced.

It is particularly preferable that the developer amount W is 85 mg / cm ² or more. When the developer amount W is 85 mg /
When the density is not less than cm ² , density unevenness is hardly observed not only in the case of visual observation but also in the case of microscopic observation, for example, in a halftone image having an absolute reflection density of 0.5 or less.

The developer amount W is preferably 180 mg / cm ² or less. When the developer amount W exceeds 180 mg / cm ² , the amount of the developer supplied to the developer carrier becomes unstable. For example, the effect of the pitch of the impeller of the impeller-shaped transport member 45 is affected by the image density. And so on. Further, the rubbing force between the developer carrier and the image carrier in the developing region becomes strong, and fine streaks in the sub-scanning direction, which appear in a halftone image, called “grilling”, tend to occur. Further, since the developer is excessively supplied to the developing area, the developer pushes the developer carrier or the image carrier, and a vibration is generated between the two, which may affect the image quality. Further, an increase in the rubbing force tends to decrease the durability of the developer.

The developer amount W is particularly preferably 160 mg / cm ² . When the developer amount W is 160 mg / cm ² or more
In the range of 180 mg / cm ² ,
Although there is a case where density unevenness which is not observed with the naked eye but is observed by microscopic observation may occur, the amount of developer W is 160 mg.
/ Cm ² or less eliminates such slight unevenness in density.

Other preferable main conditions relating to the structure of the developing device are as follows. 1 ≦ Vs / Vp ≦ 8 When Vs / Vp is smaller than 1, the moving speed of the image carrier is higher than the moving speed of the developer carrier, so that the supply of the developer to the developing area is insufficient. A development defect called a development ghost occurs. In a system where Vs / Vp is larger than 8, the scattering of the developer increases, and the durability of the developer decreases. When the radius r of the developer carrying member is 5 mm ≦ r ≦ 100 mm When the radius r is smaller than 5 mm, the restriction on the volume of the magnet arranged in the developer carrying member becomes severe, and the magnetic force required on the developer carrying member is reduced. It becomes difficult to secure. Further, since the surface curvature of the developer carrier becomes large, the development area becomes small, and it becomes difficult to secure the developability. Radius r
Is larger than 100 mm, it is difficult to set development conditions such as a development interval and a regulating unit interval (described later).
The device becomes large. The opening angle θ of the groove MZ is 0 ° ≦ θ ≦ 60 °. As is clear from FIG. 4, a groove having an opening angle θ smaller than 0 ° does not contribute to increasing the developability, and is difficult to process, and is not practical. Not a target. If the opening angle θ is larger than 60 °, the developer carrying ability of the developer carrier decreases. When the depth E of the groove MZ is 0.1 mm ≦ E ≦ 0.4 mm, if the depth E is smaller than 0.1 mm, the developer carrying property of the developer carrier is reduced.

In order to secure the required magnetic field strength on the developer carrier, it is desirable not to make the developer carrier thicker. If the depth E is larger than 0.4 mm, the strength of the developer carrying member decreases. When the depth E is larger than 0.4 mm,
The image quality of thin lines tends to decrease. The natural frequency of the drive system of the image carrier and the natural frequency of the drive system of the developer carrier do not overlap with the pitch P of the groove MZ.

When the natural frequency overlaps with the pitch P, that is, when a vibration having a period substantially equal to the pitch P occurs during development, the density unevenness due to the pitch P tends to be emphasized and the density unevenness is conspicuous. Image is formed. It is preferable to set the distance between the restricting means between the developer carrier (developing sleeve 41) and the restricting means 44 within a range of 0.1 mm to 1.0 mm.

If the distance between the regulating means is smaller than 0.1 mm, it becomes difficult to secure a necessary transport amount of the developer. Further, the stress applied to the developer increases, and the durability of the developer decreases. If the distance between the regulating means is larger than 1.0 mm, the amount of the developer supplied to the developer carrier becomes unstable. For example, the influence of the pitch of the impeller of the impeller-shaped transport member 45 is affected by the image density. , The density unevenness of the image tends to occur.

[0041]

EXAMPLE An image was formed on recording paper under the conditions shown in Table 1. Note that "dpi" in Table 1 represents the number of dots in 25.4 mm.

[0042]

[Table 1]

Table 2 shows the conditions of the experiments (1) to (9).
Tables 3 to 20 show the results of the experiment, Tables 3 and 4 show the results of the experiment (1), Tables 5 and 6 show the results of the experiment (2), and Tables 7 and 8 show the results of the experiment (2).
And 8 show the results of experiment (3), and Tables 9 and 10 show the results of experiment (4).
Tables 11 and 12 show the results of the experiment (5), and Tables 13 and 12 show the results of the experiment (5).
And 14 show the results of Experiment (6), Tables 15 and 16 show the results of Experiment (7), Tables 17 and 18 show the results of Experiment (8),
Tables 19 and 20 show the results of experiment (9), respectively. In these tables, the unit of P is mm and the unit of W is mg / cm ² . Further, in Tables 3 to 20, .largecircle. Indicates that the pitch unevenness, that is, the periodic density unevenness did not occur even when observed under magnification with a microscope or the like, and a good image was obtained. Indicates the result that a good image was obtained without the occurrence of the pitch unevenness observed in the above, and x indicates the result of the occurrence of the pitch unevenness and the formation of a defective image.

[0044]

[Table 2]

[0045]

[Table 3]

[0046]

[Table 4]

[0047]

[Table 5]

[0048]

[Table 6]

[0049]

[Table 7]

[0050]

[Table 8]

[0051]

[Table 9]

[0052]

[Table 10]

[0053]

[Table 11]

[0054]

[Table 12]

[0055]

[Table 13]

[0056]

[Table 14]

[0057]

[Table 15]

[0058]

[Table 16]

[0059]

[Table 17]

[0060]

[Table 18]

[0061]

[Table 19]

[0062]

[Table 20]

As is clear from Tables 3 to 20, good results are obtained under the condition that the pitch P (mm) is not more than twice Vs / Vp and the amount of developer W is not less than 70 mg / cm ^2. Was done.

[0064]

According to the invention of claim 1, 3, 4, or 6,
A low-cost, high-durability developer carrier can be realized, and a high-quality image with good halftone expression of a photographic image can be formed.

According to the second or fifth aspect of the present invention, it is possible to stably form a higher quality image.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a rotation direction of a photoconductor and a developing sleeve.

FIG. 3 is a diagram showing a developing sleeve in a developed state.

FIG. 4 is a view showing various groove shapes.

[Explanation of symbols]

 Reference Signs List 1 photoconductor 4 developing device 41 developing sleeve MZ groove DV developer P pitch Vp moving speed of image carrier Vs moving speed of developer carrier

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Toru Yamaguchi 2970 Ishikawacho, Hachioji-shi, Tokyo Konica Corporation F-term (reference) 2H077 AD02 AD06 AD13 AD17 DB14 FA01

Claims (6)

[Claims] 1. An image forming apparatus comprising: an image carrier; and a developer carrier that is disposed to face the image carrier, moves in the same direction as the image carrier by rotation, and conveys the developer to a development area. In the above, the developer carrying member has a developer carrying surface provided so that grooves in the rotation axis direction are uniformly distributed over the entire surface, and the pitch P (mm) of the grooves is Vp (mm). / Sec) is the moving speed of the image carrier, and Vs (mm / sec) is the moving speed of the developer carrier, and is not more than twice Vs / Vp. 2. The image forming apparatus according to claim 1, wherein an amount W of the developer conveyed to the developing area by the developer carrier is 70 mg / cm ² or more. 3. The image forming apparatus according to claim 2, further comprising a regulating unit that regulates the developer conveyed by the developer carrier. 4. A method according to claim 1, further comprising: disposing a developer carrying member for carrying the developer on the image carrying member, and moving the developer carrying member in the same direction by rotation with respect to the image carrying member. In a developing method for developing an electrostatic latent image on an image carrier, the developer carrier has a developer carrying surface provided such that grooves in a rotation axis direction are uniformly distributed over the entire surface. , The pitch P (mm) of the groove is Vp (mm / sec)
c) is the moving speed of the image carrier, Vs (mm / sec)
Where V is the moving speed of the developer carrying member, and is not more than twice Vs / Vp. 5. The developing method according to claim 4, wherein an amount W of the developer conveyed to the developing area by the developer carrier is 70 mg / cm ² or more. 6. The developing method according to claim 5, wherein the developer conveyed by the developer carrier is regulated by regulating means.