JPH1063102A - Developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developing device capable of controlling toner concentration in a two-component developer with a simple constitution and preventing the deterioration of the developer in the case of forming, carrying and feeding the thin layer of the two-component developer on an developer carrier and developing an electrostatic latent image on an electrostatic latent image carrier. SOLUTION: The developer adhering to the cylindrical carrier 11 of a developing roll 12 and consisting of carrier 14 to which the toner 15 has been supplied, is fed to a developing area opposed to a photoreceptor drum 1 with the rotation of the cylindrical carrier 11. The carrier 14 of the developer passing through the developing area comes in contact with the toner 15 at a toner supply part 18 and continuously the toner 15 enough to supplement a consumed amount in developing is supplied to the carrier 14 by a toner regulating member 16. Thereafter, the developer is peeled from the cylindrical carrier 11 by a toner electrifying part 13 and supplied to the cylindrical carrier 11 again after the supplied toner 15 is electrified, so that it is submitted for the next use.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device used in an image forming apparatus (image recording apparatus) such as an electrophotographic copying machine or a printer for forming a monochromatic or multicolor image, and more particularly, to a developing device on a developer carrying member. And a developing device for forming and carrying a thin layer of a two-component developer, applying a developing bias voltage to the developer carrier, and developing an electrostatic latent image on the electrostatic latent image carrier.

[0002]

2. Description of the Related Art In an image forming apparatus such as a copying machine, an electrostatic latent image formed on an electrostatic latent image carrier is developed by a developing means, and the developed image (visible image) is transferred onto recording paper. It is configured to copy an image or the like. As a developing device for developing an electrostatic latent image formed on an electrostatic latent image carrier, many so-called two-component developing devices using a two-component developer composed of a toner and a magnetic carrier have been proposed. In the two-component developing device, the toner and the carrier are contact-charged to impart a charge to the toner, and a layer thickness regulating member called a trimmer is arranged at an appropriate interval with respect to the developer carrier, and the toner is developed on the developer carrier. The toner layer is formed into an electrostatic latent image by forming an agent layer and applying an electric field between the electrostatic latent image carrier and the developer carrier.

Although the two-component developing apparatus has become the mainstream of the developing method from the viewpoint of superior image quality characteristics and ease of colorization, it has difficulty in controlling the toner concentration in the developer. In addition, there is a problem in that the developer is easily deteriorated in the layer thickness regulating portion. The inventors of the present application
Japanese Patent Application No. 8-40380 filed earlier proposes a developing device for preventing the developer from deteriorating in the layer thickness regulating section. The proposed developing device is configured such that magnetic poles having different polarities are alternately arranged on the entire circumference of the developer carrier such that the interval is 25 μm or more and 250 μm or less.
Alternatively, an electrode means for forming a converged electric field all around the surface of the developer carrier may be provided with an interval of 25 μm to 200 μm.
By arranging it to be equal to or less than m, a uniform developer layer is formed without using a layer thickness regulating member to prevent the developer from being deteriorated when the developer layer is formed.

However, the developing device proposed in Japanese Patent Application No. 8-40380 can prevent the deterioration of the developer in the layer thickness regulating section, but controls the toner density by detecting a change in the image density or the inductance of the developer. However, the conventional method of replenishing toner based on this detection signal is used, and the complexity of control in toner density control and the complexity of the apparatus configuration are still insufficient. Conventionally, as means for controlling the toner density by a simple mechanism, for example, JP-A-63-287874, JP-A-2-291577, and Japanese Patent Application No. 8-115667.
There is a technology disclosed in the issue.

The electrostatic image developing device disclosed in Japanese Patent Application Laid-Open No. 63-287874 discloses a regulating plate which controls a developer conveyed by a developing member composed of a developing roll and a magnet roll so as to have a desired developer layer thickness. Has been arranged. The developer cut by the regulating plate is dropped to the lower part of the developing device, transported again by the developing member and rotated, and a simple toner concentration control is performed so that the carrier surface area is controlled more than the entire surface is covered with the toner particles. ing.

The developing device disclosed in Japanese Patent Application Laid-Open No. 2-91577 exposes a toner for replenishment at an opening so that the developer on the developing sleeve comes into direct contact with the toner. Are rotated to perform spin motion of the developer spikes, and the toner concentration is easily controlled by taking the toner into the developer.

Japanese Patent Application No. Hei 8 filed earlier by the present applicant.
The developing device proposed in JP-A-115567 supplies toner to the developer collected from the developer conveying member until the developer is in an excessive state, and thereafter, the toner is separated from the carrier by an excessive toner separating means such as a sieving means or a mesh. The toner density is easily controlled by separating the toner having a small adhesive force.

[0008]

However, in the method disclosed in Japanese Patent Application Laid-Open No. 63-287874, the developer on the developing roll is cut to a desired thickness by a regulating plate to rotate the developer. This requires the developer to be excessively filled on the back surface of the regulating plate, and thus has a problem that the developer deteriorates. Further, when the present invention is applied to a developing device in which a thin layer of a developer layer is formed on a developer carrier as proposed in Japanese Patent Application No. 8-40380, the above method may cause sufficient rotation of the developer. However, there is also a problem that the toner density cannot be stably controlled.

In the method disclosed in Japanese Patent Application Laid-Open No. 2-291577, the toner is taken into the developer by the spinning motion of the developer spikes. Therefore, when the thickness of the developer layer on the developing sleeve is large, the efficiency is low. There is a problem that the spinning of the developer spike cannot be performed well, and a required amount of toner cannot be taken into the developer.
Further, when a thin layer of the developer layer is formed using the layer thickness regulating member, the developer is excessively filled on the back surface of the layer thickness regulating member, so that the developer deteriorates. Have a point. Further, a thin layer of a developer layer is formed on a developer carrier without a developing sleeve as proposed in Japanese Patent Application No. 8-40380, and the present invention is applied to a developing device which does not cause spin motion of developer ears. In addition, the toner spills from the opening of the toner for replenishment, making it difficult to control the toner concentration. Further, the developer is deteriorated when the developer layer is scraped off from the developing sleeve by the scraper. Also occurs.

According to the method proposed in Japanese Patent Application No. 8-115667, it is possible to control the toner concentration with a simple structure, but it is necessary to supply an excessive amount of toner to separate toner having a small adhesive force with a carrier. Therefore, it is necessary to once scrape the developer from the developer transport member, and there is a problem that the developer is deteriorated when the developer layer is scraped. Further, when the present invention is applied to a developing device using a developer carrier having magnetic poles having different polarities over the entire circumference as proposed in Japanese Patent Application No. 8-40380, a repulsive magnetic pole for scraping off the developer layer is formed. It is necessary to use a physical scraping means such as a scraper, which causes a problem that the developer deteriorates.

SUMMARY OF THE INVENTION It is an object of the present invention to control the toner concentration in a two-component developer with a simple structure, to prevent the deterioration of the developer, and to easily control the developer without depending on the precision of parts. An object of the present invention is to provide a developing device capable of forming a thin layer and having excellent image quality stability and maintainability.

[0012]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image forming apparatus comprising: a magnetic latent image carrier having an electrostatic latent image;
m carrying a developer consisting of two components, toner and magnetic carrier, on the surface formed alternately at intervals of m or less,
A developing bias voltage is applied, a developer carrier for developing an electrostatic latent image with toner, a toner supply unit for supplying toner to the developer on the developer carrier, and a predetermined distance from the surface of the developer carrier. And a toner regulating member disposed at an end of the toner supply section on the transport direction side of the supplied toner.

Further, the above object is achieved by a developing device in which the toner regulating member in the developing device is a seal member that comes into contact with a developer layer on a developer carrier at a predetermined pressure. Further, the above object is achieved by the developing device, wherein a toner charging unit for charging the toner is provided on the downstream side of the toner regulating member in the transport direction of the developer on the developer carrier. Achieved. The toner charging means includes a sleeve, and a magnetic field generating means provided in the sleeve and having magnetic poles having different polarities alternately arranged on the entire circumference along the circumferential direction of the sleeve. The above object is also achieved by a developing device wherein the developer carrier has an outer peripheral member and an inner member in which magnetic poles having different polarities are alternately arranged on the entire circumference.

According to the present invention, magnetic poles having different polarities are alternately arranged around the entire circumference of the developer carrying member, and the distance between the magnetic poles on the surface of the developer carrying member is set to 25 μm or more and 250 μm or less. The developer is conveyed by rotation. At this time, the lines of magnetic force generated by the magnetic poles are directed to adjacent magnetic poles having different polarities, so that the magnetic field component in the direction perpendicular to the surface of the developer carrier rapidly attenuates near the surface of the developer carrier. Therefore,
Since the developer does not concentrate on the top of the magnetic pole and does not have a portion where the developer does not adhere, a uniform developer layer can be formed without using a layer thickness regulating member. Thus, the deterioration of the developer during the formation of the developer layer is prevented, and further, the amount of the developer transported does not depend on the precision of the parts and does not change with time. Further, the toner supply unit is configured to supply the toner to the gaps of the developer by arranging a toner regulating member at least at a side end in a direction in which the developer is conveyed. At this time, the gap of the developer in the portion where the toner is consumed by the development is large, and
Since the gap of the developer in the portion where the toner is not consumed is small, it is possible to supply the consumed amount of the toner to the developer by keeping the toner regulating member and the surface of the developer carrier at a constant interval. The toner concentration in the developer can be controlled without using a complicated control mechanism.

Further, according to the present invention, the toner regulating member is configured to be a seal member that comes into contact with the developer layer on the developer carrier at a constant pressure. Accordingly, the toner can be supplied to the developer following the minute unevenness of the developer layer, and stable control of the toner concentration in the developer can be performed. Further, according to the present invention, the toner charging means for charging the toner is arranged downstream of the toner supply means with respect to the developer conveying direction on the developer carrying member. , And toner adherence to the background portion of the electrostatic latent image carrier and toner cloud inside the developing device do not occur.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A developing device according to a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows a schematic configuration of an image recording apparatus using the developing device according to the present embodiment. In FIG. 1, a photosensitive drum 1 as an electrostatic latent image carrier has a cylindrical member 1 made of a conductive material.
1A, a thin photoreceptor layer 1b is formed on the surface of FIG. For the photoconductor layer 1b, for example, a negatively charged organic photoconductor is used. The outer diameter of the photosensitive drum 1 is set to, for example, 100 mm. Around the photoreceptor drum 1, a charging device 2, an exposure unit 3, a developing device 4 having a developer carrier 11 made of a cylindrical member facing the photoreceptor drum 1 along a rotation direction thereof, a pre-transfer corotron 5 , A transfer corotron 6, a peeling corotron 7, a cleaner 8, and an optical neutralizer 9 are sequentially provided with an electrophotographic recording means.

The image forming process in the present embodiment will be briefly described with reference to FIG. FIG. 3 shows the surface potential of the photosensitive drum in each step. In the image recording apparatus, the photosensitive drum 1 is driven to rotate in a direction indicated by an arrow in FIG. The surface of the photosensitive drum 1 is uniformly charged to a potential of, for example, -450 V by the charger 2 (FIG. 3A). Next, exposure corresponding to an image is performed on the surface of the photoconductor drum 1 by the exposure unit 3 to form, for example, an electrostatic latent image of -200V.
(B)). The electrostatic latent image formed on the surface of the photoreceptor drum 1 is visualized by developing the toner by the developing device 4. At this time, a developing bias voltage is applied to the developer carrier 11 by a developing bias power supply (not shown) (FIG. 3C).

Next, the toner image thus formed on the photosensitive drum 1 is charged by the pre-transfer corotron 5 as required, and then transferred onto the recording paper 10 by the charging of the transfer corotron 6. Is done. Thereafter, the recording paper 10 is separated from the surface of the photosensitive drum 1 by the charging of the separation corotron 7. Thereafter, the recording paper 10 is conveyed to a fixing device (not shown), the toner image is fixed on the recording paper 10, and the image recording is completed. In addition,
After the transfer of the toner image and the peeling process of the recording paper 10 are completed, the surface of the photosensitive drum 1 is cleaned by a cleaner 8 to remove residual toner. It is prepared for the recording process.

As the exposure means 3, any exposure means can be used as long as it can perform exposure according to image information. As the exposure means 3, any means such as a laser writing device, an LED array, a liquid crystal light valve comprising a uniform light source and a liquid crystal micro-shutter can be used according to the purpose. The exposure means 3 may be either one for performing image portion exposure or one for performing non-image portion (background portion) exposure, and is appropriately selected as necessary.

Next, the configuration of the developing device 4 used in the image recording apparatus shown in FIG. 1 will be described with reference to FIG. The developing device 4 has a developing opening provided at a portion facing the photosensitive drum 1, and a developing roll 12 is provided facing the developing opening. In the present embodiment, the outer diameter of the developing roll 12 is set to 18 mm, the gap between the photosensitive drum 1 and the cylindrical carrier 11 is set to 300 μm, and the developer layer is in a non-contact state with the photosensitive drum 1. Is held in.

The developing roll 12 comprises a cylindrical carrier 11 which is a developer carrier which rotates in the direction of the arrow in the figure, and shafts at both ends (not shown). The developer 14 composed of the toner and the carrier adhered to the cylindrical carrier 11 is transported to a developing area facing the photosensitive drum 1 as the cylindrical carrier 11 rotates. Further, the developer 14 that has passed through the developing area
The medium carrier comes into contact with the supply toner 15 in the toner supply unit 18, and then the toner regulating member 16 supplies the toner enough to replenish the amount consumed in the development. Thereafter, the developer 14 is peeled off from the cylindrical carrier 11 by the toner charging unit 13, and after the supplied toner is charged, is supplied again onto the cylindrical carrier 11, and is used for the next use. As the toner regulating member 16, for example, a resin sheet such as polyurethane can be used. In the present embodiment, a 0.5 mm thick polyurethane sheet is brought into contact with the developer 14. The contact pressure is 0.01 ~
It is set to be in the range of 0.1 kg · f / m ² .

The cylindrical carrier 11 is formed by laminating a magnetic recording layer 11b on a conductive substrate 11a as shown in FIG. A developing bias voltage is applied to the conductive substrate 11a by a developing bias power supply (not shown). The magnetic recording layer 11b is magnetized such that magnetic poles having different polarities are alternately arranged at equal intervals on the entire circumference of the cylindrical carrier 11. The magnetic recording layer 11b is configured by dispersing a magnetic material in a binder resin. As the magnetic material, any material known as a magnet material or a magnetic recording material can be used. For example, γ-Fe ₂ O ₃
And CrO ₂ can be used. Also, as the binder resin,
Any known resin can be used as the resin constituting the magnetic recording material. For example, polycarbonate, polyester, polyurethane and the like can be used. Furthermore, conductive fine particles and the like can be added to the magnetic recording layer 11b as needed. In the present embodiment, γ-Fe ₂ O ₃ is used as the magnetic material and polyurethane is used as the binder resin, and the magnetic recording layer 1 having a thickness of 50 μm is formed on the conductive substrate 11a.
1b was formed. A magnetic recording head was used to magnetize the magnetic recording layer 11b. The direction of magnetization was horizontal to the surface of the cylindrical support 11 as shown in FIG.

Next, the magnetization of the magnetic recording layer 11b using the magnetic recording head will be described with reference to FIG. In FIG. 5, 20 is a magnetic recording head, 21 is a core member, 2
2 is a coil, 23 is a butt gap, and 24 is a magnetic flux. A current is supplied to the coil 22 from a signal generator (not shown). When a current flows through the coil 22, the core member 21 made of, for example, ferrite becomes an electromagnet,
A magnetic flux 24 is generated as shown. In the butt gap portion 23, the magnetic flux passes through the magnetic recording layer 11b and the gap space. This magnetic flux 24 causes the magnetic recording layer 11b
Is magnetized to form a residual magnetization pattern. At this time, a current according to the magnetization pattern is supplied to the coil 22, and a predetermined magnetization pattern is formed on the magnetic recording layer 11b moving in the direction of the arrow. Thus, the cylindrical carrier 11
In the circumferential direction, the N and S poles are alternately magnetized on the magnetic recording layer 11b in a sine wave pattern. The peak value of the magnetic flux density in the radial direction on the surface of the cylindrical support 11 is set to 50 mT.

In the developing device 4 shown in FIG. 2, a certain amount of the developer 14 on the cylindrical carrier 11 adheres to the cylindrical carrier 11 based on the magnetic field of the magnetic recording layer 11b described with reference to FIG. The developer layer is conveyed in a state, and a developer layer is formed without using a layer thickness regulating member. At this time, the cylindrical carrier 11
The cylindrical carrier 1 is formed by the magnetic recording layer 11b formed thereon.
On the photosensitive drum 1, the developer 14 becomes stationary, and is transported to a developing area facing the photosensitive drum 1 with the rotation of the cylindrical carrier 11, thereby developing the electrostatic latent image on the photosensitive drum 1.

FIG. 6 shows a state of the toner 31 and the carrier 32 in the developer 14 after passing through the developing area. FIG.
(A) shows developer 1 when it has not yet passed through the development area
4 is shown. The toner 31 is aligned around the carrier 32 without attaching the extra toner 15. As shown in FIG. 6B, a gap corresponding to the amount of toner used for development is generated in the developer 14 on the cylindrical carrier 11 after developing the toner. In the toner supply unit 18, toner is supplied to the gap, and excess toner is removed by the toner regulating member 16, so that a predetermined amount of toner is supplied to the developer 14.

Since the toner supplied in the toner supply section 18 is not sufficiently charged, the toner supplied to the developer 14 is charged using the toner charging section 13. For example, as shown in FIGS. 7A and 7B, the toner charging unit 13 includes a magnet roll 13b inside a non-magnetic cylindrical sleeve 13a.
Is used. This toner charging unit 13
A magnetic brush of developer is applied to the non-magnetic cylindrical sleeve 1 by a magnetic field formed between adjacent magnetic poles of the magnet roll 13b.
The magnetic brush is formed on the surface of the magnetic brush 3a, and one or both of the non-magnetic cylindrical sleeve 13a and the magnet roll 13b are rotationally driven, so that the magnetic brush is conveyed while being stirred to charge the toner. The optimal magnetic pattern of the magnet roll 13b can be appropriately selected as needed by a combination of rotation and fixing of the non-magnetic cylindrical sleeve 13a and the magnet roll 13b. For example, when the non-magnetic cylindrical sleeve 13a is rotated and the magnet roll 13b is fixed (FIG. 7).
(A)) The developer is smoothly moved from the cylindrical support 11 to the toner charging unit 13 by the repulsive magnetic fields of the two magnetic poles by setting the magnetic poles at the portion facing the cylindrical support 11 to have the same polarity. It becomes possible. Further, for example, when the magnet roll 13b is rotated (FIG. 7)
(B)) By forming a magnetic pattern such that N poles and S poles are alternately arranged in the circumferential direction of the magnet roll 13b, without causing excessive stress to the developer,
The developer can be stirred and transported.

The toner 31 in the present embodiment uses a negatively-chargeable polyester-based magenta toner having a weight average particle diameter of 7 μm, and the carrier 32 is a so-called ferrite carrier in which spherical ferrite particles are coated with a resin. I'm using The charge amount of the toner 31 is -15 to 20 m
It is adjusted to the range of C / kg. In a developing method using a thin layer of a two-component developer as in the present embodiment, it is preferable to use a carrier having a small average particle size in order to obtain a fine-grained image. When a carrier having a large average particle size is used, the distance between the developer chains arranged along the magnetic field is wide and coarse, so that it is difficult to obtain a thin layer having high uniformity, and the uniformity of the image is low. A defect and a defective edge reproduction of the line image occur. The average particle size of the carrier is preferably 100 μm or less.

In this embodiment, the relationship between the image density and the background fog on the photosensitive drum 1 was investigated by changing the magnetic pole interval of the magnetic recording layer 11b. Further, the toner concentration in the developer was measured before development, after development, and after toner supply. At this time, the weight ratio of the developer and the toner in the developer was measured. The cylindrical carrier 11 has a magnetic pole interval on its surface of 13 μm, 25 μm,
μm, 50 μm, 100 μm, 250 μm, 500 μm
Were used. However, the magnetic pole interval is a value obtained by rounding off the first decimal place.

In evaluating the results, the image density was measured for a solid image using a reflection densitometer (trade name: X-Rite310). If the image density is 1.8 or more, both solid images and line images are sufficient.
Less than 8 was indicated as x. The background fog on the photoreceptor drum 1 was visually evaluated at the time of solid image formation, and a state where no background fog was visually observed was evaluated as ○. Δ, unusable levels are indicated by x. Further, the toner concentration in the developer was indicated by け れ ば when the difference between the toner concentration in the developer before development and after the toner supply was smaller than ± 1.0, and × when the difference was ± 1.0 or more. Table 1 was obtained as a result. The comprehensive evaluation was evaluated as ○ when none of the above three items had an x, and x when there was at least one x.

[0030]

[Table 1]

According to Table 1, the distance between the magnetic poles is 25 μm or more and 250
μm or less, more preferably 50 μm or more and 250 μm
In the range of m or less, it can be seen that the toner does not adhere to the background portion, a sufficient image density is obtained, and a necessary amount of toner is supplied. Magnetic pole spacing is 25μ
If the width is smaller than m, it is difficult to arrange the magnetic carriers along the magnetic field, and the developer layer is generally sparse. For this reason, a gap is formed in an amount equal to or larger than the amount of toner consumed by the development, so that the toner is supplied more than necessary. In addition, the magnetic field at a portion distant from the surface of the cylindrical carrier 11 rapidly attenuates and becomes weaker as the magnetic pole interval is smaller. Therefore, when the magnetic pole interval is smaller than 25 μm, the magnetic field acts on the magnetic carrier on the cylindrical carrier 11. The magnetic binding force was weakened, and the centrifugal force acting on the developer when the cylindrical carrier 11 was rotated caused fogging to the background and scattering of the developer.

On the other hand, when the distance between the magnetic poles is wider than 250 μm, the magnetic binding force acting on the magnetic carrier in the region between the magnetic poles becomes extremely weak, and the developer is concentrated on the uppermost part. Accordingly, the state of the developer layer has a peak-valley structure corresponding to the magnetization pattern, and even in the developed image, unevenness of the magnetization pattern was generated, and a sufficient image density could not be obtained. Further, since the developer is intensively attached to the uppermost portion and the developer is likely to be multilayered at the uppermost portion, a necessary amount of toner cannot be supplied. Also, as mentioned above,
Since the magnetic binding force acting on the magnetic carrier attached to the gap between the magnetic poles is weak, the developer is scattered.

By setting the interval between the magnetic poles to be 25 μm or more and 250 μm or less, it is possible to arrange the magnetic carriers on the cylindrical carrier 11 in an orderly manner along the magnetic field. A developer layer having a substantially constant thickness without a developer non-adhered portion and having no peak-and-valley structure on the developer carrier is conveyed while being held by magnetic force. Therefore, an image with high uniformity can be obtained without using a layer thickness regulating member. Further, the toner is supplied to the gap of the toner generated in the carrier 32 in the developer 14 on the cylindrical carrier 11 after the development by the toner supplying unit, and the toner regulating member 16 removes the excess toner, so that the necessary amount is removed. Of toner can be supplied. Therefore, it is possible to control the toner concentration in the developer without using a complicated control mechanism.

In the present embodiment, the photosensitive drum 1
Although the developer layer on the cylindrical carrier 11 is not in contact with the photosensitive drum 1, the same effect can be obtained when the developer layer is set to be in contact with the photosensitive drum 1.
Further, in the present embodiment, the magnetic recording layer 11b has a configuration in which a magnetic material is dispersed in a binder resin. However, a similar effect can be obtained when a magnetic metal material is used. In this case, as the magnetic metal material, any known material such as a magnet material or a magnetic recording material can be used, and for example, Co-Ni-P, Co-Ni, or Co-Cr can be used.

Further, the same effect can be obtained when the magnetic recording layer 11b has a structure in which a magnetic material is dispersed in a flexible material. In this case, as the material having flexibility, a large amount of a magnetic material can be mixed, and any material that can maintain flexibility can be used. For example, Hypalon, polyisobutylene, neoprene rubber, nitrile rubber, Chlorinated polyethylene and the like can be used. Further, in the present embodiment, the N pole and the S pole are alternately magnetized in the circumferential direction of the cylindrical support 11, but the N pole and the S pole are Similar effects can be obtained even when alternate magnetization is performed.

Next, the maintenance of the toner density when the image recording apparatus having the developing device 4 according to the present embodiment shown in FIG. 1 is used will be described in comparison with a conventional developing device. For comparison with a conventional developing device, the developing device 4 according to the present embodiment has the following configuration. First, the toner 31 uses the polyester-based magenta toner as described above, and the carrier 32 uses a ferrite carrier. Toner 31 in developer and carrier 32
Was 9.5% by weight based on the weight ratio of the toner 31 in the developer. The charge amount of the toner 31 at this time is-
It is 15 mC / kg. The magnetic pole interval on the surface of the cylindrical support 11 is 100 μm.

The structure of a developing device using a conventional layer thickness regulating member used for comparison will be described with reference to FIG. Developing device 40
Has a developing opening provided in a portion of the developing housing 41 in which the developer is accommodated, facing the photosensitive drum 1, and a developing roll 42 is disposed facing the developing opening. The outer diameter of the developing roll 42 is set to 18 mm, and the gap between the photosensitive drum 1 and the cylindrical carrier 43 is set to 500 μm. The developing roll 42 includes a cylindrical carrier 43 that is a developer carrier that rotates in the direction of the arrow, a magnet roll 44 that is provided inside the cylindrical carrier 43 and has a fixed positional relationship with the photosensitive drum 1, It is constituted by shafts at both ends (not shown). A substantially intermediate portion between the magnetic poles N and S is disposed at a position where the developing roll 42 is closest to the photosensitive drum 1. The angle between the magnetic poles N and S is 70 °, and the magnetic flux density is set to 70 mT for both the magnetic poles N and S.

In the developing device 40, a fixed amount of the developer layer is formed on the cylindrical carrier 43 by the layer thickness regulating member 45. The layer thickness of the developer layer was set to be 200 μm at an intermediate portion between the magnetic poles N and S in a portion closest to the photosensitive drum 1, and the developer layer was in a non-contact state with the photosensitive drum 1. The developer 46 attached to the cylindrical carrier 43 is transported to a developing area facing the photosensitive drum 1 as the cylindrical carrier 43 rotates. Further, the developer 4 that has passed through the development area
6 is separated from the cylindrical carrier 43 by the action of the repulsive magnetic field formed by the pick-off magnetic pole 47, which is the same magnetic pole, and is conveyed to the stirring chamber 49 by the paddle 48. The two augers 50 and 51 arranged in the stirring chamber 49 rotate in opposite directions, respectively, and circulate the developer in the stirring chamber 49 connected at both ends. Developer 4
6 is mixed with other developer and newly replenished toner in the stirring chamber 49 and is sufficiently stirred. A part of the sufficiently agitated developer 46 is supplied to the cylindrical carrier 43 by the paddle 48, and is used for the next use.

In order to control the toner density of the developer 46, a solid image is developed on the photosensitive drum 1 as a reference image, and the solid image density on the photosensitive drum 1 is measured by a density detector (not shown). When the density is lower than the reference value, control is performed to supply toner. The developing bias voltage applied to the cylindrical carrier 11 is an AC voltage on which a DC voltage is superimposed. The DC component of the developing bias voltage was set to -400 V in order to prevent occurrence of background fog. The AC component of the developing bias voltage has a frequency of 6
A rectangular wave of kHz was set at a peak-to-peak voltage of 1.6 kV. The surface moving linear velocity of the cylindrical carrier 11 is 320 m.
m / s. In the developing device 4 according to the present embodiment and the developing device 40 in the related art, the weight of the developer in the developing housing is equal, and in the present embodiment, it is set to 400 g. FIG. 9 shows a transition result of the solid image density in a long-term printing experiment on A4 paper using the developing device 4 and the developing device 40.

As shown in FIG. 9, the developing device 4 according to the present embodiment
It can be seen that the image density and the toner density in the developer are favorably maintained over 100,000 sheets. On the other hand, in the developing device 40 according to the comparative example, a sharp decrease in image density occurs, the toner concentration in the developer gradually increases, and ground fogging occurs due to toner scattering on 20,000 sheets, and the developer has a long life. Reached. In addition, as a result of examining the state of the developer after the long-term printing experiment, the developer used in the developing device 40 showed significant toner deterioration and carrier deterioration. Developing device 40
In this case, since a strong stress acts on the developer when the layer thickness is regulated by the layer thickness regulating member 45, toner deterioration and carrier deterioration occur early. Due to this effect,
As described above, the image density decreases, and therefore, the toner density in the developer increases.

On the other hand, in the developing device 4, the toner and the carrier after the long-term printing experiment are in the same state as the initial state, and the layer thickness regulating member is not used. Therefore, deterioration of the developer can be prevented. Further, in the developing device 4, by supplying the toner to the gap of the toner generated in the developer after the development, the image density does not decrease and the toner concentration in the developer is kept constant.

As described above, in the developing device 4 according to the present embodiment, the toner concentration in the developer can be controlled without using a complicated control method and device, and good image quality is stably maintained for a long time. It is possible. The cylindrical carrier 1
Although the first developer layer is not in contact with the photosensitive drum 1, the same effect can be obtained even when the developer layer is set to be in contact with the photosensitive drum 1. The developing device 4 sets the magnetic pole interval on the surface of the cylindrical carrier 11 to 100 μm, but sets the magnetic pole interval to 25 μm.
The same effect can be obtained when the distance is set to m or more and 250 μm or less. Further, the magnetic recording layer 11b has a configuration in which a magnetic material is dispersed in a binder resin, but a magnetic metal material is used, or a configuration in which a magnetic material is dispersed in a flexible material. Can obtain the same effect. Further, the N-pole and S-pole were alternately magnetized in the circumferential direction of the cylindrical support 11, but the N-pole and S-pole were alternately magnetized in the longitudinal direction of the cylindrical support 11. In such a case, a similar effect can be obtained.

Next, a developing device according to a second embodiment of the present invention will be described with reference to FIG. The developing device according to the present embodiment is characterized in that the developing roll 12 in the developing device 4 according to the first embodiment is replaced with a developing roll 60 described below. The developing device 4 in this embodiment is the same as that in the first embodiment except for the developing roll 60, and the developer used is also the same as that in the first embodiment.

The structure of the developing roll 60 of the developing device 4 according to the present embodiment will be described with reference to FIG. Developing roll 6
Numeral 0 denotes a cylindrical carrier 61 which is a developer carrier rotating in the direction of the arrow in the figure, and a magnet roll 6 provided inside the cylindrical carrier 61 and having a fixed positional relationship with the photosensitive drum 1.
2 and shafts at both ends (not shown).
The outer diameter of the developing roll 60 is set to 18 mm, and the gap between the photosensitive drum 1 and the cylindrical carrier 61 is set to 500 μm. The developing roll 60 has a magnetization direction as a horizontal direction.
Magnetization is performed by the same method as in the first embodiment so that the magnetic pole interval on the surface of the cylindrical support 61 is 250 μm in the circumferential direction of the magnet roll 62. The peak value of the magnetic flux density in the radial direction on the surface of the cylindrical support 61 is 50 mT.

In the developing device 4 using such a developing roll 60, the developer adheres to the cylindrical support 61 based on the magnetic field of the magnet roll 62, and the photosensitive drum 1 is rotated with the rotation of the cylindrical support 61. Is transported to the developing area opposite to. The developer that has passed through the development area contacts the toner in the toner supply unit 18, so that the toner is supplied to the gap of the toner generated by the development. At this time, the excess toner adhering to the developer is removed by the toner regulating member 16, and thereafter, the developer is charged and stirred by the toner charging unit 13 and used for the next use.

The developing bias voltage applied to the cylindrical carrier 61 is an AC voltage on which a DC voltage is superimposed. The DC component of the developing bias voltage is set to -400 V in order to prevent occurrence of background fogging. The AC component of the developing bias voltage is a rectangular wave having a frequency of 6 kHz and a peak-to-peak voltage of 1.6 kV. Also, the cylindrical carrier 18
Is set at 320 mm / s. When the image was recorded by the developing device 4 using the developing roll 60, the toner did not adhere to the background portion, a high-quality image with high uniformity was obtained, and a necessary amount of toner was supplied. A long-term printing experiment of 100,000 sheets was performed using the developing device 4 in the same manner as described above. As a result, the image density was maintained good throughout 100,000 sheets, and the developer did not show any deterioration. Was also kept constant.

In the present embodiment, the cylindrical carrier 61
Although the upper developer layer is set in a non-contact state with the photoconductor drum 1, the same effect can be obtained when the developer layer is set so as to be in contact with the photoconductor drum 1. Further, the magnetic pole interval on the surface of the cylindrical support 61 in the magnet roll 60 is set to 250 μm, but the magnetic pole interval is 2 μm.
A similar effect can be obtained when the thickness is 5 μm or more and 250 μm or less. Further, the developing bias voltage is an AC voltage on which a DC voltage is superimposed, and the waveform of the AC voltage is a rectangular wave. However, the developing device in the form of the present invention is not limited to this, and any developing device according to the purpose or application can be used. Can be used. Further, the rotation direction of the cylindrical carrier as the developer carrier is opposite to the rotation direction of the photosensitive drum as the electrostatic latent image carrier, but the same can be applied in the same direction. Further, the cylindrical support as the developer support is rotated and the magnet roll is fixed, but the cylindrical support is fixed and the magnet roll is rotated, or the cylindrical support and the magnet roll are provided with a speed difference. The developer may be conveyed in the same direction or in the opposite direction to convey the developer.

A cylindrical carrier as a developer carrier,
In addition, the configuration of the magnet roll is not limited to the present embodiment, and an arbitrary configuration according to the purpose and application is possible. For example, a conductive layer, a resistance layer, a protective layer, a wear-resistant layer, and the like may be provided on the magnetic recording layer. Further, an adhesive layer, an underlayer, a nonmagnetic layer, and an elastic layer may be provided between the conductive layer and the magnetic recording layer, or between the soft magnetic layer and the magnetic recording layer, or between the substrate and the magnetic recording layer. Note that the surface moving linear velocity of the developer carrier
Although set to 20 mm / s, the state of formation of the developer layer does not depend on the linear velocity of the surface movement.

Further, the description has been given of the monochromatic image recording apparatus. However, the present invention is also applicable to a color image recording apparatus which forms a color image with a plurality of color toners on an electrostatic latent image carrier and collectively transfers the toner images onto recording paper. It is equally applicable.
Further, a photosensitive member was used as the electrostatic latent image carrier. However, a dielectric material was used as the electrostatic latent image carrier, and a discharge recording head used in an electrostatic printer and a Japanese Patent Application Laid-Open No.
An electrostatic latent image may be formed by an ion flow control head or the like disclosed in JP-A-190854.

[0050]

As described above, according to the present invention, the magnetic poles having different polarities are alternately arranged on the entire circumference of the developer carrying member, and the distance between the magnetic poles on the surface of the developer carrying member is set to 25 μm to 250 μm. The developer carrier is transported by the rotation of the developer carrier including a magnetic pole, and the toner carrier is supplied to the developer on the developer carrier by bringing the toner into contact with the developer carrier at least at the end of the developer carrier in the developer transport direction. It is configured to arrange a toner regulating member that keeps a constant interval with the developer, so that a fixed amount of the developer layer is formed on the developer carrying member without using the layer thickness regulating member, and used for development. A small amount of toner can be supplied to the developer without using a complicated control method / apparatus. Furthermore, according to the present invention,
The present invention can be applied regardless of the shape of the developer carrying member and the developing method, that is, whether it is a contact type or a non-contact type, and a developing device applicable to any image forming apparatus can be realized.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration of an image forming apparatus including a developing device according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating a configuration of a developing device according to the first embodiment of the present invention.

FIG. 3 is a potential explanatory diagram showing an image forming step according to the first embodiment of the present invention.

FIG. 4 is a diagram illustrating a structure of a developer carrying member according to the first embodiment of the present invention.

FIG. 5 is a diagram illustrating a method of magnetizing a developer carrier according to the first embodiment of the present invention.

FIG. 6 is an explanatory diagram schematically showing states of a developer before and after development.

FIG. 7 is an explanatory diagram illustrating a rotation direction of a toner charging unit according to the first embodiment of the present invention.

FIG. 8 is a diagram illustrating a configuration of a conventional developing device.

FIG. 9 is a diagram illustrating changes in solid image density and toner density in a developer in a long-term printing experiment.

FIG. 10 is a view showing a developing roll of a developing device according to a second embodiment of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 photoconductor drum 1a conductive cylindrical member 1b photoconductor layer 2 charger 3 exposure means 4 developing device 5 pre-transfer corotron 6 transfer corotron 7 exfoliating corotron 8 cleaner 9 light eliminator 10 recording paper 11 cylindrical carrier 11a conductive substrate 11b Magnetic recording layer 12 Developing roll 13 Toner charging section 13a Non-magnetic cylindrical sleeve 13b Magnet roll 14 Developer 15 Supplying toner 16 Toner regulating member 18 Toner supply section 20 Magnetic recording head 21 Core member 22 Coil 23 Butt gap section 24 Magnetic flux 31 Toner 32 Carrier 40 Developing device 42 Developing roll 43 Cylindrical carrier 44 Magnet roll 45 Layer regulating member 46 Developer 47 Pickoff magnetic pole 48 Paddle 49 Stirrer chamber 50, 51 Auger 60 Developing roll 61 Cylindrical carrier 62 Magnet roll

Claims (14)

[Claims] An image forming apparatus comprising: an electrostatic latent image carrier that carries an electrostatic latent image; and a toner and a toner on a surface on which magnetic poles having different polarities are alternately formed at an interval of not less than 25 μm and not more than 250 μm all around. A developer carrier that carries and transports a developer composed of two components of a magnetic carrier, and a developing bias voltage is applied to develop the electrostatic latent image with the toner; and the developer on the developer carrier. A toner supply unit that supplies the toner to the toner supply member, and a toner regulating member disposed at an end of the toner supply unit on the side in the transport direction of the supplied toner while maintaining a predetermined distance from the surface of the developer carrier. A developing device comprising: 2. The developing device according to claim 1, wherein the toner regulating member is a seal member that contacts a developer layer on the developer carrier at a predetermined pressure. 3. The developing device according to claim 1, wherein a toner charging unit for charging the toner is provided downstream of the toner regulating member with respect to a direction in which the developer on the developer carrier is transported. A developing device, comprising: 4. The developing device according to claim 3, wherein the toner charging means is provided in the sleeve, and magnetic poles having different polarities are alternately arranged on the entire circumference along the circumferential direction of the sleeve. And a magnetic field generating means. 5. The developing device according to claim 4, wherein said toner charging means rotates said sleeve to convey and charge said developer. 6. The developing device according to claim 4, wherein said toner charging means charges said developer by rotating said magnetic field generating means to transfer and charge said developer. 7. The developing device according to claim 4, wherein said toner charging means carries and charges said developer by rotating said sleeve and said magnetic field generating means. 8. The developing device according to claim 1, wherein the developer carrier has an outer peripheral member and an inner member in which magnetic poles having different polarities are alternately arranged on the entire circumference. A developing device. 9. The developing device according to claim 8, wherein said developer carrier conveys said developer by rotating said outer peripheral member. 10. The developing device according to claim 8, wherein said developer carrier conveys said developer by rotating said internal member. 11. The developing device according to claim 8, wherein said developer carrier carries said developer by rotating said outer peripheral member and inner member. 12. The developing device according to claim 1, wherein the toner supply unit is configured such that an area where the supplied toner contacts the developer on the developer carrier is the developer. A developing device, wherein the distance between the magnetic poles on the surface of the developer carrying member is wider in the transport direction of the developing device. 13. The developing device according to claim 1, wherein said developer layer is not in contact with said electrostatic latent image carrier. 14. The developing device according to claim 1, wherein said developer layer is in contact with said electrostatic latent image carrier.