JP2001183893A - Color image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize excellent developing available over a long term without being replenished often by a service man as a color image forming device constituted such that a color image is formed by plural developing units using the two-component developer. SOLUTION: Toner can be supplied to the respective developing units 13 from a supply toner housing part 31 by a toner supply means 32 and carrier can be supplied to the respective units 13 from a supply carrier housing part 33 by a carrier supply means 34. Then, the toner is supplied according to the consumption thereof associated with an image forming action and the carrier is supplied according to the total working time of the developing units.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color image forming apparatus for forming a color image by an electrophotographic system,
In particular, the present invention relates to a color image forming apparatus that forms a color image by a plurality of developing devices using a two-component developer.

[0002]

2. Description of the Related Art In an electrophotographic image forming apparatus,
A latent image is formed by performing image exposure on a uniformly charged image forming body, developing the latent image into a toner image, and then transferring the toner image to a transfer material such as recording paper. As the transfer material carrying the toner image passes through the fixing device, the toner is fixed on the transfer material.

In developing a latent image, a two-component developer composed of a toner and a carrier is often used because of its excellent developability. The toner and the carrier are agitated in the developing device, and the toner is electrostatically attached to the outer surface of the carrier. The toner is conveyed to the developing area and the toner is separated from the carrier under the condition that the developing bias is applied, and the toner is separated from the carrier. Electrostatically adheres to the latent image portion of. Since toner is consumed by development in the developing device, a toner concentration detecting means for detecting the amount of toner in the developer using an inductance or the like is provided in the developing device, and when the toner falls below a predetermined ratio, A toner is supplied from a toner supply unit such as a toner hopper into a developing device.

[0004] The toner in each developing unit is replenished for the shortage by the consumed new toner, but the carrier is continuously used. When the carrier is used for a long period of time, fine toner of less than 1 μm adheres to the outer periphery of each carrier, and as a result, the developing performance gradually decreases and a good toner image is obtained. Will not be. For this reason, when a predetermined number of images have been formed, good development is performed again by removing each of the developing devices arranged in the vicinity of the image forming body, replacing the internal developer, and replacing it with a new carrier. Service business was performed.

[0005] From such a situation, a new carrier is added at a fixed ratio together with the toner to be replenished and replenished, and the carrier having deteriorated developing performance is gradually replaced with a new carrier, whereby the developer is replaced as a service business. Has been proposed by Japanese Patent Publication No. 2-15991 (hereinafter referred to as "trickle development").

Further, a developing device containing a plurality of developers having different toner colors such as Y, M, C, and K is provided at a peripheral portion of the rotating image forming body, and a toner image is superposed on the image forming body. A color image forming apparatus for forming a color toner image and transferring the color toner image to a transfer material at once is provided by the present applicant. This type has a feature that the color image forming apparatus can be miniaturized by effectively arranging a charger, a developing device and a cleaner around the image forming body without providing an extra space. In such a color image forming apparatus, the consumption of the toner inside the developing unit is detected, and the toner is replenished based on the detection result.

[0007]

In the conventionally proposed trickle development, a carrier having a fixed ratio with the toner has been supplied in proportion to the toner consumption. However, in such a developer replenishment method, the characteristics of the carrier significantly change depending on the use condition of the image forming apparatus, and a difference occurs in a developed toner image.

According to the present invention, in a color image forming apparatus in which a plurality of developing devices are arranged in proximity to the periphery of an image forming body, an operation of replacing a developer is not required, an excessive amount of carrier is not consumed, An object of the present invention is to provide an image forming apparatus in which a developing device always maintains good developing conditions and can obtain a good color image stably over a long period of time.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to provide a color image forming apparatus which forms a color image by providing a plurality of developing units having a two-component developer comprising a color toner and a common carrier at a peripheral portion of an image forming body. A means for individually supplying a color toner and a carrier to each developing device, and a storage unit, wherein the color toner is supplied according to the amount of toner consumed during the image formation, and the carrier is supplied to the developing device during the image formation. A color image forming apparatus which is supplied in accordance with an operation frequency; and a plurality of developing devices having a two-component developer composed of a color toner and a common carrier are provided on the periphery of the image forming body. A color image forming apparatus for forming a color image by providing a color toner and a carrier to each developing device individually, and a storage unit, wherein the color toner is used for image formation. Supplies in accordance with the toner consumption, the carrier is achieved by a color image forming apparatus characterized by being fed in inverse proportion to the toner consumption amount consumed in association with image formation (the invention of claim 2).

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Prior to the description of an embodiment of the present invention, a developing device used in a color image forming apparatus of the present invention will be described.

FIG. 1 shows a cross-sectional structure of an example of the developing device 13, which is provided so as to face a photosensitive drum 10 which is an image forming body which rotates in the direction of an arrow.

Reference numeral 130 denotes a developing sleeve which is made of a non-magnetic conductive material such as aluminum or stainless steel, and whose rotating shaft is fitted into the side wall of the housing 136 and rotates in the direction of the arrow. A voltage is applied to the developing sleeve 130 via a protective resistor 138 by a bias power supply 137 in which a DC power supply and an AC power supply are superimposed.

Reference numeral 131 denotes a magnet body fixed inside the developing sleeve 130 and having a plurality of N and S magnetic poles arranged in the circumferential direction.
The S magnetic pole is usually magnetized to a magnetic flux density of 300 to 1500 Gauss, and the magnetic force holds the developer on the developing sleeve 130 to form a developer spike.

Reference numeral 132 denotes a developer layer thickness regulating member made of a rod-shaped magnetic material for regulating the developer layer thickness on the developing sleeve 130 to a predetermined amount. Reference numeral 133 denotes a developer supply roller which supplies a newly stirred two-component developer onto the developing sleeve. Reference numeral 134 denotes a developer stirring screw; 135, a toner supply path; and a case 13 that holds toner and carriers through a developer supply path 135, which will be described later, to hold a developer capacity.
6 to the developer pool.

The toner newly supplied through the toner supply path 135 is stirred with the existing developer by the developer stirring screw 134, and a predetermined charge (Q
/ M), the toner is attached to the surface of the magnetic carrier, and is supplied to the developing sleeve 130 by the developer supply roller 133. Developing sleeve 130
A magnetic carrier having toner adhered to the surface by the internal magnet body 131 adheres to the peripheral surface, and rotates in the arrow direction.
The developer attached to the peripheral surface of the developing sleeve 130 is regulated by the developer layer thickness regulating member 132 such that the layer thickness of the developer becomes a uniform thin layer. The technique for making the layer thickness of the developer on the developing sleeve 130 uniform is described in detail in Japanese Patent Application Laid-Open No. 2-64675 by the present applicant.

With the rotation of the developing sleeve 130, the developer layer whose uniform thickness is regulated moves the base portion to a developing area facing the grounded photosensitive drum 10, and supplies a bias power to the developing sleeve 130. 137, the photosensitive drum 10 and the developing sleeve 1
An oscillating electric field is generated between the photosensitive drum 30 and the toner, so that the toner in the developing area is separated from the carrier by the toner and adheres to the latent image portion on the photosensitive drum 10 to visualize the latent image with toner particles. Development takes place.

By appropriately setting the arrangement relationship of the magnetic poles of the magnet body 131 and the magnetic flux density of the magnetic poles, the developing gap Ds
d can be set, a sufficient developing electric field is maintained,
Further, since the magnetic carrier is also held by the strong magnetic binding force, the toner easily flies in a non-contact state, and a good quality toner image is formed on the latent image portion of the photosensitive drum 10.

The developing device used in the color image forming apparatus of the present invention has an excellent feature that a non-contact developing method can easily perform development with a high image density without fog. Preferred conditions for developing a clear image will be described in more detail below.

Conventionally, a two-component developer comprising a non-magnetic toner having an average particle size of tens of μm and a magnetic carrier having an average particle size of tens to hundreds of μm has been used in the developing device. However, as the developer used in the present invention, the transfer of the toner can be effectively controlled by the oscillating electric field. Therefore, the toner having an average particle diameter of 1 to 20 μm, preferably 4 to 10 μm, and the average particle diameter of 10 to 60 μm, More preferably, 20-50μ
It is preferable to use a two-component developer comprising m carriers. This will be described.

(Carrier) In general, if the average particle size of the magnetic carrier particles is large, the state of the ears of the magnetic brush formed on the developing sleeve 130 becomes coarse, so that the electrostatic latent image is developed while being vibrated by an electric field. However, there is a problem that unevenness tends to appear in the toner image, and the toner density in the ears becomes low, so that high-density development is not performed. In order to solve this problem, the average particle diameter dc of the magnetic carrier particles may be reduced.
It has been found that the above problem does not occur when the thickness is 0 μm, preferably 20 to 50 μm.

When dc is 10 μm or less, it is difficult to sufficiently magnetize the carrier, and the carrier adheres to the surface of the image forming body 10 together with the toner particles, or easily scatters.

On the other hand, when dc is 60 μm or more, the specific surface area of the carrier becomes small, so that the toner cannot be sufficiently charged. Further, since the covering ratio is high, toner scattering is also likely to occur.

The intensity of magnetization of the carrier (maximum magnetization) is 5
-60 emu / g, preferably 10-40 emu / g. Although this strength depends on the magnetic flux density on the developing sleeve 130, under a general magnetic flux density condition of the developing sleeve 130, if it is less than 5 emu / g, the magnetic binding force does not work and causes carrier scattering. . In addition, 60 emu /
If the ratio exceeds g, the ears of the carrier become too high, and it is difficult to maintain a non-contact state with the photosensitive drum 10.

Such a magnetic carrier is made of a metal such as iron, chromium, nickel, or cobalt, or a compound or alloy thereof, such as triiron tetroxide, γ-oxide, as in a conventional magnetic carrier. Ferromagnetic spherical particles such as ferric iron, chromium dioxide, manganese oxide, ferrite, and manganese-copper alloy, or the surfaces of these spherical magnetic particles are made of styrene resin, vinyl resin, ethylene resin. , Rosin-modified resin, acrylic resin, polyamide resin, epoxy resin, polyester resin, silicone resin, fluorine resin, or the like, or by spherical coating with a copolymer.

A so-called resin-dispersed carrier in which magnetic fine particles are dispersed and contained in these resins can also be used.

(Toner) Generally, when the average particle size of the toner particles is reduced, the charge amount is qualitatively reduced in proportion to the square of the particle size, and the adhesive force such as van der Waals force is relatively increased. Scattered easily, and fogging is likely to occur. Then, when the average particle size is 10 μm or less, this problem becomes remarkable. In the developing device according to the present embodiment, this problem is solved by performing the development under an oscillating electric field.

When the volume average particle diameter D ₅₀ (μm) of the toner increases, as already mentioned, the roughness of the image becomes conspicuous. If D ₅₀ is used the toner following micronized 10 [mu] m, the resolution is remarkably improved, so give a clear high-quality images shading difference also faithfully reproduced. D ₅₀ is 20μm or more, results in degradation of image quality, at the 1μm or less, poor charging, scattering and the like easily occurs.

For the above reasons, the volume average particle diameter D _{50 of the} toner
Is 1 to 20 μm, preferably 3 μm ≦ D ₅₀ ≦ 10 μm.

When D ₅₀ is larger than 10 μm, the particle size is large and the resolution is insufficient, and when D ₅₀ is smaller than 3 μm, the cohesive force is large and triboelectric charging tends to be poor.

In addition, since the toner particles operate following the electric field, the absolute value of the charge amount of the toner particles is preferably set to 3 to 30 μC / g in the case of a two-component developer, in particular, in order to secure the developing property and to prevent the fog. And from the viewpoint of preventing scattering. In particular, when the particle size is small, a high charge amount is required.

Examples of the binder resin for such a toner include a styrene resin, a vinyl resin, an ethyl resin, a rosin-modified resin, an acrylic resin, a polyamide resin, an epoxy resin, a polyester resin, and a styrene-acryl resin. And the like, or a mixed resin or the like. To these resins, a coloring component such as a color pigment, and if necessary, a charge controlling agent, a release agent such as a wax, etc. are added, and toners such as a conventionally known pulverization granulation method, suspension polymerization method and emulsion polymerization method are used. It can be made by a method equivalent to the manufacturing method.

(Developer) As the two-component developer used in the developing device used in the present invention, the above-mentioned spherical carrier particles and toner are mixed at the same ratio as in the conventional two-component developer. An agent is preferably used. As a carrier, a general coating carrier (density 5 to 5) is used.
8 g / cm ³ ), the toner concentration in the developer is 2 to 30% by weight, preferably 5 to 20% by weight.

If the amount is less than 2% by weight, the number of toners required for development cannot be secured, and the coverage decreases, resulting in excessive charging and a decrease in developability.

If it is more than 30% by weight, the coverage becomes large, and poor charging and toner scattering tend to occur.

However, when a relatively light (2-4 g / cm ³ ) resin-dispersed carrier having the above-mentioned density is used as the carrier in the developer, the toner concentration in the developer is as follows:
Slightly higher than when using a general resin-coated carrier,
The content is preferably 5 to 40% by weight, more preferably 10 to 30% by weight.

A toner concentration detecting sensor 139 for detecting the toner concentration in the developer by, for example, inductance is provided at a position on the inner surface of the housing 136 which is always in contact with the stirred developer.
Is provided, and when the toner density detected by the toner density detection sensor 139 becomes lower than a preset toner density, the control unit (not shown) replenishes the toner consumed by the development with toner. Done. In the present invention, replenishment of the carrier, which will be described later, is also performed.

If necessary, a fluidizing agent for improving the fluid sliding of the particles and a cleaning agent useful for cleaning the surface of the image forming body 1 are mixed with the developer. As the fluidizing agent, colloidal silica, silicon varnish, metal soap or nonionic surfactant can be used. As the cleaning agent, a surfactant such as fatty acid metal salt, organic group-substituted silicon or fluorine can be used. Can be.

The conditions for the developer have been described above. Next, the developing conditions for forming a developer layer with such a developer and developing the electrostatic latent image on the photosensitive drum 10 will be described.

The gap between the developing sleeve 130 and the photosensitive drum 10 is preferably set between 50 and 1,000 μm. If this gap is smaller than 50 μm, it is difficult to form a non-contact developing layer that uniformly performs a developing action, and it is also impossible to supply a sufficient amount of toner to the developing area, so that stable development cannot be performed. Conversely, when the gap exceeds 1,000 μm, the counter electrode effect is reduced, and a sufficient development density cannot be obtained. When the gap is in the range of 50 to 1,000 μm, a non-contact developer layer having an appropriate thickness can be uniformly formed. Therefore, the gap and the thickness of the developer layer are adjusted so that the developer layer does not come into contact with the surface of the photosensitive drum 10 and is as close as possible under the condition that no oscillating electric field is generated during non-image formation. Setting is done. As a result, it is possible to prevent sweeping or fogging from occurring in the toner image. The position where the developing sleeve 130 is close to the photosensitive drum 10 is used to prevent scattering of toner and the like.
A position where the direction of gravity is directed toward the developing sleeve 130 is preferable, but, of course, the position is not limited thereto.
The outer diameter of the developing sleeve 130 is preferably 10 mm to 30 mm, and the rotation speed and the rotation direction of the developing sleeve 130 are changed at a low speed in order to prevent scattering of toner and the like. The direction is preferably opposite to the moving direction, but from the viewpoint of the image reproducibility due to the developer layer, it is preferable that the speed is almost the same or faster in the same direction as the moving direction of the photosensitive drum 10. Therefore, it is preferable that the peripheral speed of the developing sleeve 130 be kept within 1.5 to 3.5 times the peripheral speed of the photosensitive drum 10, and the direction be the same. But,
It is not limited to this.

For development under an oscillating electric field, the developing sleeve 13 is used.
The bias power supply 137 applies a superimposed voltage of a DC voltage related to fogging prevention and development density and an AC voltage related to development density and gradation, thereby generating an oscillating electric field in the development area. It is preferred to do so. As the DC component, in the reversal development, the DC component of the bias voltage is set to a voltage substantially equal to the receiving potential of the non-image background portion of the photosensitive drum 10. The frequency of the AC component is 100 Hz to 20 kHz, preferably 1 to 10 kHz.
Hz and an amplitude of 100 to 5000 V are used.
The AC component is not limited to a sine wave, but may be a rectangular wave, a triangular wave, or the like. If the frequency of the AC component is too low, the pitch of the vibration will appear in the development.On the other hand, if it is too high, the developer will not be able to follow the vibration of the electric field, and the development density will decrease, resulting in a clear high image quality. There is a tendency that images cannot be reproduced. The amplitude of the AC component is related to the frequency, but the greater the amplitude, the more the developer layer vibrates and the more the effect increases, but on the other hand, the larger the amplitude, the easier it is to cause fog, Such dielectric breakdown is likely to occur. However, if the carrier particles of the developer are insulated by a resin or the like and are made spherical, the dielectric breakdown can be prevented, and the generation of fog can be prevented by the DC component. The surface of the developing sleeve 130 may be insulated or semi-insulated with a resin or an oxide film,
The surface may be provided with irregularities to improve the transportability of the developer layer. By using the above-mentioned developer and developing conditions, clear development with no fog and excellent resolving power can be performed stably.

In the developing device 13 used in the present invention, a hole 136a is provided near the developer interface on the rear wall of the housing 136 along the developer stirring screw 134.
When the amount of the developer inside exceeds a predetermined amount, the excess developer overflows from the hole 136a, and the overflowed developer falls to the waste carrier collection part 136b, and the dropped developer is used for waste carrier collection. It is transported to the waste toner box by the screw 136c.

In the conventional trickle development, a small amount of carrier at a fixed ratio is mixed with the toner to be replenished.
Case 13 detected by toner concentration detection sensor 139
When the toner density in the toner cartridge 6 becomes lower than a preset toner density, a small amount of a predetermined ratio of carrier is supplied together with the toner when supplying the toner. In the present invention, in a color image forming apparatus using a plurality of developing devices, which will be described later, the amount of toner to be supplied to each developing device and the amount of carrier to be supplied are controlled independently of developer supply. One embodiment will be described.

(Embodiment 1) In the color image forming apparatus of the present embodiment, the developer is individually supplied to each developing unit. At this time, the color toner is supplied in accordance with the amount of toner consumed for image formation. The carrier is controlled so as to be supplied in accordance with the operation frequency of the developing device accompanying the image formation. FIG. 2 is a block diagram showing the replenishment control of the developer.
FIG. 4 is an explanatory diagram illustrating a state in which developer is supplied to the developing device through a supply path.

When the image formation is started, the developing sleeve 1
The rotation of 30 causes the developer attached on the peripheral surface of the developing sleeve 130 to be developed in the developing area, and the toner is consumed. The toner in the housing 136 is detected by the toner concentration detection sensor 139. When the toner ratio is detected to be lower than a predetermined toner ratio, the control unit T1 supplies toner using a supply roller or the like. By operating the means 32, the toner in the replenishment toner storage unit 31 is replenished into the housing 136 through the developer replenishment path 135.
When the toner concentration detection sensor 139 detects that the toner ratio of the developer in the housing 136 has recovered to the predetermined toner ratio by the toner replenishment, the control unit T1 controls the toner replenishing unit 3
2 is stopped to stop toner supply.

When the image formation is started, the operation frequency detecting means 30A of the development unit 13 detects the operation time of the development unit 13 and the number of prints.
The operation time and the number of prints are measured. Control unit T
1 is a predetermined detection result by the operation frequency detection means 30A,
For example, when it is detected that the developing operation for 100 printed sheets has been performed, for example, the carrier replenishing means 34 using a supply roller is rotated by a predetermined number of revolutions, and a 20 g of carrier is supplied from the replenishment carrier accommodating portion 33 to the developer replenishing path 135.
Through which the housing 13 containing, for example, a carrier of about 1 kg
Replenish into 6. The replenishment of the carrier may be performed separately from the replenishment of the toner. It is preferable to replenish the toner in the case 136 through the developer replenishing passage 135 in a mixed form because the transportability is improved.

The developer supply path 135 is a hollow pipe, and the supply and supply of toner and carrier are performed by gravity or by rotating a transfer screw provided therein. Even when the developer supply path 135 is a supply path in which the carrier is joined to the toner supply path from the middle and is conveyed, the supply is such that the toner is joined to the carrier supply path from the middle and is conveyed. It can be on the road.
Alternatively, the transport path may be configured such that toner is merged into a separately provided supply path and the carrier is merged.

Since the carrier gradually deteriorates depending on the operation frequency of the developing device 13, the carrier is replenished according to the operation frequency in the present embodiment, and FIG. 4 shows the effect of the present invention. In the graph, the horizontal axis indicates the number of prints, and the vertical axis indicates the charge amount of the toner. A decrease in toner charge is an indicator of developer deterioration,
A curve CT2 is a curve showing a decrease in the average charge amount of the toner when the carrier is not replenished, and a curve CT1 is a curve showing the decrease in the charge amount of the toner when the carrier is replenished in the present embodiment. This indicates that when the carrier is replenished in the embodiment, good development is performed over 50,000 prints or more without forming a developer, and image quality can be stabilized. Note that the curve CT3
Is a curve showing a decrease in the charge amount of the toner when the carrier is replenished at a fixed ratio with the toner replenishment by the conventional toggle method.

(Embodiment 2) In the color image forming apparatus of this embodiment, the developer is individually supplied to each of the developing devices. At this time, the color toner is supplied in accordance with the amount of toner consumed during image formation. The carrier is controlled so as to be supplied in inverse proportion to the amount of toner consumed during the image formation. FIG. 5 is a block diagram showing the supply control of the developer, and FIG. FIG. 9 is an explanatory diagram illustrating a state in which developer is supplied through a path.

When the image formation is started, the developing sleeve 1
The rotation of 30 causes the developer attached on the peripheral surface of the developing sleeve 130 to be developed in the developing area, and the toner is consumed. The toner in the housing 136 is detected by the toner concentration detection sensor 139 at the toner ratio. When the toner ratio is detected to be lower than the predetermined toner ratio, the control unit T2 rotates the supply roller to control the toner. By operating the toner replenishing means 32 for replenishing, the toner in the replenishment toner storage unit 31 is replenished into the housing 136 through the developer replenishment path 135. The toner replenishing means 32 is provided with a replenished toner amount detection unit S32 for detecting the replenished toner amount by measuring the number of rotations of the supply roller, and measures the replenished toner amount when replenishing the toner.

When the toner concentration detecting sensor 139 detects that the toner ratio of the developer in the housing 136 has recovered to the predetermined toner ratio by the toner replenishment, the controller T2 stops the toner replenishing means 32 and stops the toner replenishment. I do.

When the image formation is started, the developing device 13
The number of prints is used as a method of detecting the operation time of
Number-of-prints accumulator 30 for measuring and integrating the number of prints
The number of prints is measured by B. However, in the case of double-sided printing, it is measured as 2. When the control unit T2 detects that the print number accumulating unit 30B has completed, for example, printing 100 sheets, the replenishment toner amount detecting unit 32
A is detected as to how much toner has been supplied.
In the present embodiment, the processing is performed on the assumption that the amount of toner consumed during printing of 100 sheets is equal to the amount of toner supplied during printing of 100 sheets.

The control unit T2 detects the amount of replenishment toner at the end of printing 100 sheets. If the replenishment toner amount detected by the replenishment toner amount detection unit S32 is within a preset standard replenishment range, a carrier of 20 g is used. Replenish. When the replenishment toner amount detected by the replenishment toner amount detection unit S32 is equal to or less than a preset replenishment range, 30 g of carrier replenishment is performed. Further, when the detected amount of supplied toner is equal to or larger than the preset supply range, 10 g of carrier is supplied.

In the present embodiment, since the developer deteriorates as the amount of toner consumed during the formation of a predetermined amount of image decreases, a large amount of carrier is supplied to promote the recovery of the developer. 5 is a graph showing the effect of the present invention, in which the horizontal axis indicates the number of prints, and the vertical axis indicates the toner charge amount as an index of the deterioration of the developer. A curve CT11 is a curve showing a decrease in the charge amount of the toner when the development is performed without performing the carrier replenishment and the toner consumption is large in forming the image.
Curve CT12 is developed without carrier replenishment,
This shows a decrease in the charge amount of the toner when the toner consumption amount is small during image formation. In the present embodiment,
When the amount of toner consumption is small, a larger amount of carrier is replenished than when the amount of toner consumption is large, whereby the charge amount of the toner is maintained at a substantially constant state as shown by the curve CT10. When the carrier was replenished in the present embodiment, it was confirmed that the image formation of 50,000 prints or more was performed without developing agent replacement, and all favorable development was performed.

Next, a description will be given of a color image forming apparatus for forming a color image by mounting a plurality of sets of the developing devices 13 described above. FIG. 8 is a cross-sectional view of a color printer as an example of an image forming apparatus equipped with a plurality of developing devices of the present invention, and FIG. 9 is a cross-sectional view of the image forming body.

According to FIG. 8 or FIG. 9, the photosensitive drum 10 as an image forming body is formed on the outer periphery of a cylindrical base formed of a light-transmitting member such as glass or light-transmitting acrylic resin. It is formed by forming a photoconductive layer and a photoconductor layer of an organic photosensitive layer (OPC).

The photosensitive drum 10 is rotated clockwise as shown by an arrow in FIG. 1 with the light-transmitting conductive layer grounded by power from a drive source (not shown).

In the present invention, the exposure beam for image exposure is
The photoconductor layer of the photoconductor drum 10, which is the image forming point, only needs to have an exposure light amount of a wavelength that can provide an appropriate contrast with respect to the light attenuation characteristic (photocarrier generation) of the photoconductor layer. . Therefore, the light transmittance of the light-transmitting substrate of the photosensitive drum in the present embodiment does not need to be 100%, and may have a characteristic of absorbing a certain amount of light when transmitting the exposure beam. . The point is that any suitable contrast can be provided. As a material of the light-transmitting substrate, an acrylic resin, particularly one obtained by polymerizing a methyl methacrylate monomer, is preferably used because of its excellent light-transmitting properties, strength, accuracy, surface properties, etc. Various translucent resins such as acryl, fluorine, polyester, polycarbonate, polyethylene terephthalate and the like used for the above can be used. Further, as long as it has a light-transmitting property with respect to the exposure light, it may be colored. As the light-transmitting conductive layer, indium tin oxide (I
TO), tin oxide, lead oxide, indium oxide, copper iodide, or a metal thin film of Au, Ag, Ni, Al, or the like that maintains light transmissivity. Reactive deposition method, various sputtering methods, various CV
D method, dip coating method, spray coating method and the like can be used.
Various organic photosensitive layers (OPC) can be used as the photoconductor layer.

The organic photosensitive layer serving as the photosensitive layer of the photoconductor layer includes a charge generation layer (CGL) mainly composed of a charge generation substance (CGM) and a charge transport layer (CTM) mainly composed of a charge transport substance (CTM). And CTL). An organic photosensitive layer having a two-layer structure has high durability as an organic photosensitive layer due to its thick CTL and is suitable for the present invention.
The organic photosensitive layer may have a single layer structure containing a charge generation material (CGM) and a charge transport material (CTM) in one layer. ,
Usually, a binder resin is contained.

A scorotron charger 11 as a charging unit described below, and an exposure optical system 1 as an image writing unit will be described.
2. The developing device 13 as a developing unit is prepared for an image forming process for each color of yellow (Y), magenta (M), cyan (C) and black (K), respectively. Are arranged in the order of Y, M, C, and K with respect to the rotation direction of the photosensitive drum 10 indicated by the arrow in FIG.

Scorotron charger 11 as charging means
Is mounted so as to face and be close to the photosensitive drum 10 in a direction perpendicular to the moving direction of the photosensitive drum 10 as an image forming body (the direction perpendicular to the plane of FIG. 1). A control grid (no symbol) maintained at a predetermined potential with respect to the body layer;
As a, for example, a sawtooth electrode is used, and a charging action (in this embodiment, negative charging) is performed by corona discharge having the same polarity as that of the toner, thereby giving a uniform potential to the photosensitive drum 10. As the corona discharge electrode 11a, a wire electrode or a needle electrode may be used.

The exposure optical system 12 for each color has a linear exposure element (LED) in which a plurality of LEDs (light emitting diodes) as light emitting elements for image exposure light are arranged in an array parallel to the axis of the photosensitive drum 10. (Not shown) and a selfoc lens (not shown) as an equal-magnification imaging element are configured as an exposure unit attached to a holder. Cylindrical holding member 2
At 0, the exposure optical system 12 for each color is attached and housed inside the base of the photosensitive drum 10. In addition, as the exposure element, a linear element in which a plurality of light emitting elements such as FL (phosphor emission), EL (electroluminescence), and PL (plasma discharge) are arranged in an array is used.

The exposure optical system 12 as an image writing means for each color sets the exposure position on the photosensitive drum 10 between the scorotron charger 11 and the developing unit 13 and the photosensitive unit with respect to the developing unit 13. It is arranged inside the photoconductor drum 10 in a state provided on the upstream side in the rotation direction of the drum 10.

The exposure optical system 12 performs image processing based on image data of each color sent from a separate computer (not shown) and stored in the memory, and then performs image processing on the uniformly charged photosensitive drum 10. Exposure is performed to form a latent image on the photosensitive drum 10. The emission wavelength of the light-emitting element used in this embodiment is usually 6 for the toners of Y, M, and C, which have high translucency.
The wavelength in the range of 80 to 900 nm is good, but the wavelength may be shorter than this, since the color toner does not have sufficient translucency since image exposure is performed from the back surface.

The developing device 13 as a developing means for each color includes
Inside yellow (Y), magenta (M), cyan (C)
Alternatively, a two-component developer of black (K) is accommodated, and is a cylindrical developer carrier made of non-magnetic stainless steel or aluminum material having a thickness of 0.5 to 1 mm and an outer diameter of 15 to 25 mm, respectively. A certain developing sleeve 130 is provided.

In the developing area, the developing sleeve 130 is kept out of contact with the photosensitive drum 10 with a predetermined gap, for example, 100 to 1000 μm, by abutting rollers (not shown). It rotates in the forward direction at the closest position. At the time of development, an AC voltage AC is superimposed on a DC voltage of the same polarity as the toner (in the present embodiment, a negative polarity) or a DC voltage with respect to the developing sleeve 130. By applying the developing bias voltage, non-contact reversal development is performed on the exposed portion of the photosensitive drum 10. At this time, the precision of the development interval needs to be about 20 μm or less in order to prevent image unevenness.

As described above, the developing unit 13 transfers the electrostatic latent image formed on the photosensitive drum 10 by the charging by the scorotron charger 11 and the image exposure by the exposure optical system 12 in a non-contact state. Reversal development is performed with toner having the same polarity as the charge polarity of No. 10 (in the present embodiment, the photosensitive drum is negatively charged, and the toner has a negative polarity).

As shown in FIG. 9, the photosensitive drum 10 and the holding member 20 are located at the rear and front ends of the apparatus.
Flange members 10A and 10B, which are support members for rotatably supporting the photosensitive drum 10, respectively, and a holding member 20
Are integrally formed with the flanges 120A and 120B for supporting by pressing means or means such as screws. The photosensitive drum 10 has a flange member 10 as a support member.
A and the flange member 10B are shafts 12 which are fixed members integrally formed with the flange 120A of the holding member 20.
1 and the flange 120B are rotatably supported via bearings B1 and B2, respectively.

The shaft 121 has a shaft portion 121A for holding the photoreceptor drum 10, and a support shaft 140 as a holding means for the shaft 121 having an engagement hole 140A is provided on the rear device board 70. I have. Engagement hole 140
A is fitted with a linear bearing B4, and the support shaft 140 is fixed to the rear device substrate 70 by screws or the like with the receiving member 140a interposed therebetween. The support shaft 140 is located at the center of the gear G2 that meshes with the drive gear G1, and rotatably supports a conductive member 141 that integrates the gear G2 via a bearing B3. On the other hand, the device substrate 70 on the front side of the device
An opening 70 </ b> A that allows the photosensitive drum 10 that integrates the exposure optical system 12 fixed to the holding member 20 to be inserted and removed is opened.

The holding member 20 inserts the shaft portion 121A of the shaft 121 into the linear bearing B4 provided on the support shaft 130 with respect to the device board 70 on the rear side, and
A of the engagement pin 121P of the support shaft 140
By engaging with a V-shaped groove formed in 40B, the exposure optical system 12 is attached while regulating the angular position thereof. The front cover 120D is mounted at a predetermined position by fixing the front cover 120D with the screw 52 while pressing the front cover 120D in the axial direction with the buffer material K interposed therebetween.

The coupling 10C, which is an engagement member attached to the side surface of the flange member 10A, which is a support member for supporting the photosensitive drum 10, and the drive member, which is a coupling member attached to the side surface of the transmission member 141 that integrates the gear G2. The flange member 10 is formed by the pin 141A and the set screw 51.
A coupling portion between the gear A and the gear G2 is formed, and when the photosensitive drum 10 having the holding member 20 integrated therewith is mounted, the coupling 10C attached to the side surface of the flange member 10A.
Is fitted into a drive pin 141A attached to the side surface of the conductive member 141 having the gear G2, and after engagement, the conductive member 131 having the gear G2 and the photosensitive drum 10 having the flange member 10A are aligned at the center and the outer peripheral surface. In the state
The drive pin 141A and the coupling 10C are fixed from the side of the photosensitive drum 10 using the set screw 51, and the flange member 10A and the gear G2 are connected and fixed.

When the image forming body driving motor (not shown) is started by the start of image formation, the rotational power of the driving gear G1 is transmitted to the photosensitive drum 10 via the coupling portion by the gear G2, and the photosensitive drum 10 is moved to the position shown in FIG. , And at the same time, application of a potential to the photosensitive drum 10 is started by the charging action of the Y scorotron charger 11.
After a potential is applied to the photosensitive drum 10, exposure by the first color signal, that is, an electric signal corresponding to Y image data is started in the Y exposure optical system 12, and the surface of the photosensitive drum 10 is rotated by the rotational scanning. An electrostatic latent image corresponding to the yellow (Y) image of the original image is formed on the photosensitive layer. This latent image is reversely developed in a non-contact state by the Y developing device 13, and a yellow (Y) toner image is formed on the photosensitive drum 10.

Next, the photoreceptor drum 10 places an M scorotron charger 11 on the yellow (Y) toner image.
A potential is applied by the charging action of the M exposure optical system 12
Exposure is performed using an electrical signal corresponding to the second color signal of m, i.e., magenta (M) image data.
Yellow (Y) by non-contact reversal development
A toner image of magenta (M) is formed on the toner image of FIG.

By the same process, the cyan (C) toner image corresponding to the third color signal is further obtained by the C scorotron charger 11, the exposure optical system 12 and the developing device 13, and the K scorotron charger 11. , Exposure optical system 1
A black (K) toner image corresponding to the fourth color signal is sequentially superimposed and formed by the second and developing units 13, and a color toner image is formed on the peripheral surface within one rotation of the photosensitive drum 10. You.

As described above, in this embodiment, Y, M,
The exposure of the organic photosensitive layer of the photoconductor drum 10 by the C and K exposure optical systems 12 is performed through a transparent substrate from the inside of the photoconductor drum 10. Therefore, the exposure of the image corresponding to the second, third, and fourth color signals can form an electrostatic latent image without being shielded by the previously formed toner image, which is preferable. Photoconductor drum 1
0 may be exposed from outside.

On the other hand, the recording paper P as a transfer material is sent out from a paper feed cassette 15 as a transfer material storage means by a feed roller (no code) and fed by a feed roller (no code) to a timing roller. It is conveyed to 16.

The recording paper P is synchronized with the color toner image carried on the photosensitive drum 10 by the driving of the timing roller 16, and the recording paper P is charged by the paper charger 1 as paper charging means.
Due to the electrification of 50, the toner is attracted to the conveyor belt 14a and fed to the transfer area. The recording paper P, which is closely transported by the transport belt 14a, is moved around the photosensitive drum 10 by a transfer unit 14c as a transfer unit to which a voltage having a polarity opposite to that of the toner (positive polarity in the present embodiment) is applied in a transfer area. The color toner images on the surface are collectively transferred to the recording paper P.

The recording paper P on which the color toner image has been transferred is
The paper is discharged by a paper separation AC neutralizer 14h as a transfer material separating unit, separated from the transport belt 14a, and transported to the fixing device 17.

The fixing device 17 includes a heat-ray fixing roller 17a as an upper roll-shaped rotating member for heat ray fixing (upper fixing member) for fixing a color toner image, and a pressure rubber roller 47a as a lower fixing member. Is composed of
Inside the heat ray fixing roller 17a, a halogen lamp 171g that emits heat rays such as infrared rays or far infrared rays including visible light depending on a light source is provided as a heat ray irradiation unit.

Heat ray fixing roller 17a and pressure rubber roller 4
The recording paper P is sandwiched by a nip portion N formed between the recording paper P and the color toner image on the recording paper P by applying heat and pressure. Is discharged to the tray at the top of the device.

The toner remaining on the peripheral surface of the photosensitive drum 10 after the transfer is transferred to a cleaning blade 19 provided in a cleaning device 19 as an image forming body cleaning means.
Cleaning is performed by a. The photosensitive drum 10 from which the residual toner has been removed is uniformly charged by the scorotron charger 11, and enters the next image forming cycle.

Developing units 13 (Y), 13 (M), 13
(C) and 13 (K) respectively show replenishment toner storage units 3 containing yellow, magenta, cyan, and black toners.
1 (Y), 31 (M), 31 (C), 31 (K), and a common supply carrier storage section 33 for supplying a carrier are provided. The developing unit 13 (Y) receives the yellow toner from the replenishment toner storage unit 31 (Y), and the carrier from the common replenishment carrier storage unit 33, as described above. Supplied through. Developing units 13 (M), 13 (C), 13
The same applies to (K).

Since the toner and the carrier are mixed and supplied to improve the transportability, the developer supply path 135 may be a supply path (FIG. 8) for supplying the toner at the time of the supply of the carrier. The supply path may be a supply path that supplies a carrier to the supply path. Further, the developer supply path 13
5 may be a system in which toner and carrier are supplied to a supply path to the developing device 13. In either case, the toner and the carrier are supplied to the developing device 13 from the developer supply path 135 in a merged manner.

Although the carrier is supplied from the replenishment carrier storage section 33, it is also effective to mix the carrier with the same fluidizing agent as used for the toner for improving the fluid sliding.

The carrier is supplied in accordance with the operation frequency of the developing unit 13 and the like. However, since the developing characteristics change due to environmental changes and changes in the characteristics of the photosensitive member, the environmental temperature and humidity are lower than a predetermined value. When the charge potential of the photosensitive member measured by a surface voltmeter becomes lower than a predetermined value, the supply amount of the carrier is controlled to be increased so that the developed image quality is stabilized. Will be further achieved.

[0085]

According to the first and second aspects of the present invention, a new carrier is appropriately supplied into the developing device.
With a stable connection of good developing performance, a color image forming apparatus using such a developing device does not require replacement of a developer by a service person, consumes excessive carrier, and can produce a high-quality image. It can be obtained stably over a long period of time.

[Brief description of the drawings]

FIG. 1 is a cross-sectional configuration diagram of a developing device.

FIG. 2 is a block diagram illustrating developer supply control according to the first embodiment.

FIG. 3 is an explanatory diagram illustrating developer supply in the first embodiment.

FIG. 4 is a graph showing the effect of the invention in the first embodiment.

FIG. 5 is a block diagram illustrating developer supply control according to a second embodiment.

FIG. 6 is an explanatory diagram showing developer supply in the second embodiment.

FIG. 7 is a graph showing the effect of the invention in the second embodiment.

FIG. 8 is a sectional configuration diagram of a color printer.

FIG. 9 is a sectional configuration diagram of the image forming body of FIG. 8;

[Explanation of symbols]

 REFERENCE SIGNS LIST 10 photoconductor drum 11 scorotron charger 12 exposure optical system 13 developing device, developing device 31 supply toner storage unit 32 toner supply unit 33 supply carrier storage unit 34 carrier supply unit 135 developer supply path 139 toner density detection sensor

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H005 AA21 CA21 FA01 2H030 AD16 BB04 BB25 BB36 2H077 AA28 AA39 AB02 AB18 AC02 AC04 AD06 AD13 AD24 AD36 BA01 CA19 DA10 DA22 DA42 DA54 DA78 DB02 EA03 EA16 GA13 GA17

Claims (5)

[Claims] In a color image forming apparatus for forming a color image by providing a plurality of developing units having a two-component developer composed of a color toner and a common carrier on a peripheral portion of an image forming body, each developing unit is individually provided. A means for supplying a color toner and a carrier, and a storage unit, wherein the color toner is supplied in accordance with the amount of toner consumed in forming the image, and the carrier is supplied in accordance with the operation frequency of the developing device in accordance with the image formation A color image forming apparatus, comprising: 2. In a color image forming apparatus for forming a color image by providing a plurality of developing units having a two-component developer composed of a color toner and a common carrier on a peripheral portion of an image forming body, each developing unit is individually provided. A means for supplying a color toner and a carrier, and a storage unit, wherein the color toner is supplied in accordance with the amount of toner consumed in forming the image, and the carrier is supplied in inverse proportion to the amount of toner consumed in forming the image. A color image forming apparatus supplied. 3. The toner according to claim 1, wherein the toner and the carrier merge and are supplied to each developing unit through a supply path.
Or the color image forming apparatus according to 2. 4. The image forming apparatus according to claim 1, wherein when a change in the environment or a change in the characteristics of the image forming body is performed, the amount of the carrier to be supplied together with the toner replenishment is changed so that the toner can be supplied.
Item 10. A color image forming apparatus according to item 9. 5. The developing device according to claim 1, wherein a discharge port for discharging the overflowed developer is provided on an outer wall of the developer near an interface of the developer above the stirring screw. The color image forming apparatus according to claim 1.