JP2003098772A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of preventing developing property from being deteriorated by preventing the initial lowering of the bulk density of developer and the lowering of toner concentration caused therewith and normalizing the variation of the developer amount carried on a developer carrier caused by the influence of the variation of the bulk density of the developer due to environmental variation even in the case of using two- component developer consisting of small particle size toner and carrier. SOLUTION: In this image forming apparatus, a developing device is provided with two sensors for detecting magnetic permeability, either of which is a sensor for detecting the mixing ratio of the toner and the carrier and the other of which is a sensor for detecting the bulk of the developer, and the ratio of the circumferential speed of an image carrier and the developer carrier is changed in accordance with an output value from the sensor for detecting the bulk of the developer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus having a developing device used for an electrophotographic copying machine, a printer, a fax machine, etc., and in particular, it uses a two-component developer composed of a toner having a small particle diameter and a carrier. The present invention relates to an image forming apparatus that forms an image.

[0002]

2. Description of the Related Art Conventionally, as a developing device used in an image forming apparatus such as an electrophotographic copying machine, a printer or a facsimile, a developing device which uses a two-component developer containing a toner and a carrier is widely used. Has been.

A developing device using a two-component developer basically conveys the developer to a developing area and carries the developer in the developing area, and supplies the developer to the developer carrying body. On the developer carrier, a supply unit, a recovery unit that recovers the developer after development from the developer carrier, an agitating / conveying unit that mixes the replenished toner and the developer, and conveys the developer to the supply unit. It is composed of a regulation unit that regulates the amount of the developer to be constant.

As the two-component developer used in the developing device, toner particles having a particle size of 7 μm or less are used as toner, and carrier particles corresponding to the toner particles having a particle size of 50 μm are used.
Carrier particles having a particle size of less than or equal to μm are usually used as those having good developability.

[0005]

Conventionally, in the electrophotographic development process, the surface of an image bearing member (photoreceptor) is uniformly charged and then exposed to form a latent image. The latent image was made visible by applying a developing bias to (1) and bringing the developer into contact with the image carrier. However, in this developing process, by using a toner particle having a particle size of 7 μm or less as a toner and a two-component developer composed of carrier particles having a particle size of 50 μm or less as a carrier corresponding thereto, high developing property is obtained. Although obtained, the bulk of the developer, that is, the bulk density, changes due to environmental changes such as high temperature / high humidity, low temperature / low humidity, and deterioration of the developer due to use time, and the toner particle size is 7.0 μm or less.
Even when a two-component developer consisting of a toner having a carrier particle size of 50 μm or less and a carrier is used, the bulk density of the developer decreases due to the initial decrease in the bulk density of the developer and the accompanying decrease in toner concentration, and environmental changes. The amount of the developer conveyed on the developer carrying member fluctuates due to the influence of the fluctuation of 1. In particular, in the case of a two-component developer composed of a toner having a polymerization prescription or a toner having a small particle diameter and a carrier, the bulk density of the developer varies greatly, and there is a problem that the developability is deteriorated due to a decrease in the developer carrying amount of the developer carrier. .

The present invention solves the above problems and prevents the initial decrease in developer bulk density and the accompanying decrease in toner concentration even when a two-component developer comprising a toner having a small particle size and a carrier is used. At the same time, it is an object of the present invention to provide an image forming apparatus that normalizes fluctuations in the amount of developer conveyed on a developer carrier due to the effects of fluctuations in developer bulk density due to environmental changes and prevents deterioration in developability. .

[0007]

SUMMARY OF THE INVENTION The above object is produced by forming an latent image on an image carrier, visualizing the latent image, and mixing toner and carrier at a constant mixing ratio. In an image forming apparatus using a component developer and a developing device having a developer carrier that conveys the two-component developer to a developing area, the developing device is provided with two sensors for detecting magnetic permeability. One is a sensor for detecting the mixing ratio of toner and carrier, the other is a sensor for detecting the bulk of the developer, and the image carrier and the developing device are selected according to the output values of the sensor for detecting the bulk of the developer. This is achieved by an image forming apparatus characterized by changing the peripheral speed ratio with the agent carrier.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below. Note that the description in this section does not limit the technical scope of the claims or the meaning of terms. Further, the following affirmative description in the embodiments of the present invention shows the best mode, and does not limit the meaning or technical scope of the terms of the present invention.

An image forming process and each mechanism of an embodiment of an image forming apparatus using the developing device according to the present invention will be described with reference to FIGS. 1 to 8. 1 is a schematic sectional configuration diagram of a color image forming apparatus showing an embodiment of an image forming apparatus using the developing apparatus according to the present invention, and FIG. 2 is a schematic sectional configuration diagram showing an example of the developing apparatus of FIG. FIG. 3 is a diagram for explaining the flow of the two-component developer.
4 is a front view of the developing device of FIG. 4, FIG. 4 is a view showing a method for measuring the bulk density of a two-component developer, FIG. 5 is a view showing a projected image of polymerized toner particles, and FIG. FIG. 7 is a control block diagram of a developing device showing correction control of the invention, and FIG. 7 shows how to obtain predicted data from the toner concentration detection sensor and the developer bulk density detection sensor, and the detection detected by the developer bulk density detection sensor. FIG. 8 is a diagram showing an example of a method for correcting the output value of the developer bulk density detection sensor based on the difference between the value and the ideal value of the predicted data, and FIG. 8 is a diagram showing the developer carrying property and the developing property in the continuous copy test. 7 is a graph showing experimental results of the present invention and a conventional example for and.

In FIG. 1, the image forming apparatus GS comprises an image forming apparatus body GH and an image reading apparatus YS.

The image forming apparatus main body GH is called a tandem type color image forming apparatus, and includes a plurality of sets of image forming units 10Y, 10M, 10C, 10K, a belt-shaped intermediate transfer member 6, a sheet feeding / conveying means, and a sheet feeding / conveying means. The fixing device 24.

The image forming unit 10Y for forming a yellow (Y) color image includes a charging unit 2Y, an exposing unit 3Y, a developing unit 4Y and a cleaning unit 8Y arranged around a photosensitive drum 1Y as an image carrier. Have. The image forming unit 10M that forms a magenta (M) color image includes a photosensitive drum 1M as an image carrier, a charging unit 2M, an exposing unit 3M, a developing device 4M, and a cleaning unit 8M. Image forming unit 10C that forms a cyan (C) color image
Is a photosensitive drum 1C as an image bearing member, and a charging unit 2
C, an exposure unit 3C, a developing device 4C, and a cleaning unit 8C. The image forming unit 10K that forms a black (K) image has a photosensitive drum 1K as an image carrier, a charging unit 2K, an exposing unit 3K, a developing device 4K, and a cleaning unit 8K. Charging means 2Y and exposing means 3Y, charging means 2M and exposing means 3M, charging means 2C and exposing device 3C
The charging unit 2K and the exposure device 3K form a latent image forming unit.

The intermediate transfer member 6 is wound by a plurality of rollers and is rotatably supported. Image forming unit 10Y,
The images of the respective colors formed by 10M, 10C, and 10K are transferred onto the rotating intermediate transfer member 6 by transfer means 7Y, 7M, 7
Sequential transfer by C and 7K (primary transfer) forms a composite color image. The recording paper P stored in the paper feed cassette 20 is fed by the paper feed means 21, and is fed by the paper feed rollers 22A, 22B, 22C and the registration rollers 23.
After that, the color image is transferred to the transfer unit 7A, and the color image is transferred onto the recording paper P (secondary transfer). The recording paper P to which the color image is transferred is fixed by the fixing device 24, sandwiched by the paper discharge rollers 25, and placed on the paper discharge tray 26 outside the machine.

On the other hand, after the color image is transferred onto the recording paper P by the transfer means 7A, the residual toner is removed by the cleaning means 8A from the intermediate transfer body 6 in which the recording paper P is separated by the curvature.

4Y, 4M, 4C and 4K are yellow (Y), magenta (M), cyan (C) and black (K).
Is a developing device containing a two-component developer consisting of a toner having a small particle diameter and a carrier, and 5Y, 5M, 5C and 5K are
Toner replenishing means for replenishing the developing devices 4Y, 4M, 4C, and 4K with new toner.

An image reading device YS including an automatic document feeding device 201 and a document image scanning exposure device 202 is installed above the image forming apparatus main body GH. The original d placed on the original table of the automatic original feeding device 201 is conveyed by the conveying means, and the image of one side or both sides of the original is scanned and exposed by the optical system of the original image scanning exposure device 202, and the line image sensor CCD is exposed. Is read.

The analog signal photoelectrically converted by the line image sensor CCD is subjected to analog processing, A / D conversion, shading correction, image compression processing, etc. in an image processing section, and then an image writing section (exposure means) 3Y, Three
Send signals to M, 3C and 3K.

The automatic document feeder 201 is provided with automatic double-sided document conveying means. Since the automatic document feeder 201 can continuously read the contents of a large number of documents d fed from the document table and store them in the storage means (electronic RDH function), copying is possible. It is conveniently used when copying the contents of a large number of originals by the function or when transmitting a large number of originals d by the facsimile function.

A temperature / humidity sensor TS as an environmental condition detecting means for detecting an environmental condition is provided inside the image forming apparatus main body GH. Further, the image forming apparatus main body GH is provided with a sheet number counter CT (see FIG. 6, not shown in FIG. 1) for counting the number of sheets to be copied, which is connected to a developing control unit described later in detail.

Next, the developing devices 4Y, 4M, 4C and 4K will be represented as the developing device 4, and the photosensitive drums 1Y, 1 will be described.
The photosensitive drum 1 is represented by M, 1C, and 1K as shown in FIG.
The developing device used in the image forming apparatus of the present invention will be described below with reference to FIGS. In the following description, the two-component developer is also called a developer. Further, the black solid arrows in FIG. 3 indicate the supply and conveyance directions of the two-component developer to the developer carrier, and the white arrows indicate the peeling and recovery directions of the two-component developer from the developer carrier. It is a thing. V1 to V11 indicate the circulation order of the circulation system of the two-component developer.

The developing device 4 includes a developing device frame 40, a developer carrying member 41 consisting of a developing roller, a magnetic field generating means (magnet roll) 42, a regulating means 43 consisting of an ear cutting plate, a water wheel type supplying means 44, and a screw. From a supply / conveying means 45 consisting of a screw, a stirring / conveying means 46 consisting of a screw, a stripping roller 47, a stripping plate 48, a collecting means 49 consisting of a screw, a toner concentration detection sensor TD, a developer bulk density detection sensor TK, and the like. It is configured.

The developer carrying member 41 of the developing device 4 is 200 to 580 mm / sec by the developing roller driving motor M2.
The photosensitive drum 1 is rotated at a peripheral speed Vs of about 80 to 250 mm / sec by the photosensitive member drive motor M1. Usually, it is preferable that the peripheral speed ratio between the developer carrying member 41 and the photosensitive drum 1, Vs / Vp, be a constant value of about 1.5. Further, the magnetic field generating means 42 is fixed, and the regulating means 43, the supplying means 44, the supplying / conveying means 45, the stirring / conveying means 46, the peeling roller 47, the peeling plate 48, the collecting means 49, etc. are driven by the developing roller. The motor M2 is driven to rotate each.

By the counterclockwise rotation of the peripheral velocity Vp indicated by the arrow of the photosensitive drum 1 and the clockwise rotation of the peripheral velocity Vs indicated by the arrow of the developer carrying member 41, an electrostatic latent image is formed in the developing region DR. It is developed. A developing bias in which a DC bias having the same polarity as the latent image polarity is superimposed on the AC bias is applied to the developer carrying member 41 by the bias power source BS, and reversal development is performed.

The developer carrying member 41 is disposed so as to face the photosensitive drum 1 carrying an electrostatic latent image and is rotatably supported. The developer carrying member 41 rotates as shown by an arrow to develop the developer in the developing region DR. Then, the developer is carried in the developing region DR to form a developer layer necessary for the development.

The magnetic field generating means 42 includes a plurality of magnetic poles N1, N2, S1, which are arranged so as to be included in the developer carrying member 41.
It has S2 and S3. Of the plurality of magnetic poles of the magnetic field generating means 42, the two magnetic poles S2 and S3 adjacent to each other are arranged with the same polarity and form a repulsive magnetic field. The developer stripping magnetic pole S2 strips and scatters the developer on the developer carrier 41. The developer receiving magnetic pole S3 sucks the developer supplied by the supply unit 44 and attaches the developer onto the developer carrier 41.

The supplying means 44 is a rotatable water wheel type conveying means for supplying the developer to the developer carrying body 41, and the developer carried from the supplying / conveying means 45 is supplied to the developer carrying body 4.
The developer is uniformly supplied in the vicinity of the developer receiving magnetic pole S3.

The supplying / conveying means 45 is arranged in parallel with the supplying means 44 and agitates the developer conveyed from the agitating / conveying means 46 to convey it to the supplying means 44.

The stirring / conveying means 46 mixes the new toner to be replenished with the developer refluxed from the supplying / conveying means 45, agitates them, and conveys them to the upstream portion of the supplying / conveying means 45.

A stripping roller 47 is disposed near the developer stripping magnetic pole S2 of the developer carrying member 41. The stripping roller 47 includes a rotatable rotating member (sleeve) 47A and a cylindrical magnet body 47B housed inside the rotating member 47A and fixed to the developing device frame 40. The magnet body 47B includes, for example, n1, n2, s1, s
The magnetic pole n1 is composed of five magnetic poles 2 and s3, and the magnetic pole n1 is the developer carrier
Adjacent two magnetic poles s2 and s3 that face the developer stripping magnetic pole S2 and that are adjacent to each other form a repulsive magnetic field of the same polarity.

In the vicinity of the magnetic pole s2, the tip of the stripping plate 48 is in close proximity or in slight contact. The stripping plate 48 and the stripping roller 47 form stripping means. The developer released from the surface of the developer carrier 41 by the developer stripping magnetic pole S2 of the developer carrier 41 is sucked by the magnetic pole n1 in the stripping roller 47, and carried and transported by the rotating rotary member 47A. Then, it is stripped off by the stripping plate 48 in the vicinity of the magnetic pole s2, and falls into the collecting section 403.

The collecting means 49 rotatably arranged in the collecting section 403 receives and collects the developer which is peeled off by the peeling roller 47 and the peeling plate 48 and falls,
The developer is transported to the outside of the developing region DR of the developer carrier 41 (see FIG. 3) on the downstream side of the supply / transport unit 45 in the transport direction. At the position where the developer does not return to the developer carrier 41, the collected developer is put in the developing region of the developer carrier 41 on the downstream side in the transport direction of the supply / transport means 45. (See FIG. 3). Alternatively, the collecting means 49
The developer collected by the above may be returned to the upstream portion of the stirring / conveying unit 402.

Supply / transport means 45, stirring / transport means 46
Each of the collecting means 49 and the collecting means 49 is composed of a spiral screw, conveys the developer in the rotation axis direction while stirring, and discharges the developer in a direction substantially perpendicular to the rotation axis.

The developing device frame 40 includes a lower frame 40A for supporting the supplying means 44, the supplying / conveying means 45 and the stirring / conveying means 46, and a middle frame 40B for supporting the collecting means 49.
And an upper lid 40C for closing the upper opening of the middle frame 40B
It consists of and.

The lower frame 40A is supplied with the supply means 44 and
It comprises a supply unit 401 for accommodating the conveying means 45 and an agitating / conveying section 402 for accommodating the agitating / transporting means 46. The supply unit 401 and the stirring / conveying unit 402 are connected to the lower frame 40A.
Are formed on both sides with the first partition wall 404 standing upright from the bottom portion thereof.

The second partition wall 405 formed at the bottom of the middle frame 40B for rotatably supporting the collecting means 49 separates the supply section 401 and the collecting section 403 from each other in the image area GR (see FIG. 3). Separated. Also, the middle frame 40B
A part of the above covers the upper opening of the stirring / conveying unit 402.

As shown in FIG. 3, the developer transport downstream side of the recovery section 403 and the developer transport downstream side of the supply section 401 are
A first opening 40 formed near the end of the second partition 405.
6 communicate with each other.

Stirring with the developer conveying downstream side of the supply unit 401
The developer transport upstream side of the transport unit 402 means the first partition 404.
A second opening 407 is formed near one end of the first opening 407 so that the second opening 407 communicates with the second opening 407.

A first partition wall 404 is provided between the developer carrying downstream side of the stirring / carrying section 402 and the developer carrying upstream side of the supplying section 401.
The third opening portion 408 is provided near the other end portion of the above, and communicates with each other.

The toner concentration detection sensor TD for detecting the mixing ratio of the toner and the carrier, that is, the toner concentration is the developing device 4
Inside the supply unit 401 of the developer supply unit 401, at the bottom of the supply unit 401 on the downstream side of the developer transport (see FIG. 2), the developer bulk density detection sensor TK for detecting the bulk of the developer, that is, the bulk density, is Inside the supply unit 401, the detection unit is attached to the side surface of the lower frame 40A between the supply / conveyance unit 45 and the supply unit 44 so as to cover the upper portion of the developer. The toner concentration detection sensor TD may be attached at a position other than the above-mentioned place, for example, on the upstream side of the developer conveyance of the supply unit 401. In addition, as shown in FIG.
The developer is dropped into the funnel RT, which is a triangular pyramid-shaped member installed in a plate shape (no reference numeral) at an angle of 45 °, and the funnel R
When the developer is dropped from the hole Ha having an outer diameter of 2.5 mm at the lower part of T to the box-shaped receiving member GBa at a constant speed,
The weight of the developer received by the receiving member GBa (g / cm ³ ) is defined as the bulk density.

The toner density detection sensor TD and the developer bulk density detection sensor TK measure the magnetic permeability of the developer by using resistance / capacity detection, respectively, to detect the developer conveyed inside the developing device 4. The toner concentration and the bulk density of the developer are detected. The developing roller drive motor M2 is rotated by the control signal from the development control unit, which will be described in detail later, in response to the toner concentration detection signal, and the toner replenishment unit 5 is driven to agitate the new toner and the developer conveyance upstream side of the conveyance unit 402. The toner is replenished to the toner replenishing opening 409 provided in the vicinity. The toner replenishing means 5 can also optically detect the image density after the development processing and perform toner replenishment control according to the detection result of the image density.

The developer stripped off by the stripping roller 47 and the stripping plate 48 is collected in the collecting section 403, and the collected developer is conveyed to the developer conveying downstream side by the collecting means 49, and the second partition wall is formed. First opening 4 formed in 405
Reflux from 06 into the supply unit 401.

The developer in the supplying section 401 is conveyed by the supplying / conveying means 45 into the stirring / conveying section 402 from the second opening 407 formed at one end of the first partition 404. The developer conveyed into the agitating / conveying unit 402 is conveyed by the agitating / conveying means 46 while mixing and agitating the toner replenished from the toner replenishment opening 409 with the developer, and the developer is conveyed to the first partition 404. It is discharged from the third opening 408 formed at the other end and is returned to the supply unit 401.
In the supply unit 401, the supply / conveyance means 45 conveys the developer in the axial direction and discharges the developer to supply it to the supply means 44. The supply unit 44 radiates the developer while conveying the developer in the axial direction to supply the developer to the developer carrier 41.

The first opening 40 provided in the vicinity of the end of the second partition wall 405 for partitioning the recovery unit 403 and the supply unit 401.
6, and the second opening 4 provided near both ends of the first partition wall 404 that partitions the supply unit 401 and the stirring / conveying unit 402.
07 and the third opening 408 are both arranged outside the image forming region GR of the developer carrier 41.

The supply means 44 and the supply / conveyance means 45 are rotated in the same direction as the rotation direction of the developer carrier 41, so that the developer can be efficiently supplied to the developer carrier 41. Is achieved, and a stable developer can be supplied, so that a good image can be obtained.

Further, by making the rotating direction of the collecting means 49 reverse to the rotating direction of the developer carrying member 41, it is possible to reduce the backflow of the developer in the collecting section 403. Further, the developer carrying force of the supplying means 44 is set to be smaller than the developer carrying force of the supplying / transporting means 45. As a result, it is possible to prevent the occurrence of developer packing on the downstream side of the supply unit 44 in the developer transport direction, and to stably supply the developer to the developer carrier 41 without impairing the durability of the developer. Will be possible.

The circulation of the developer is performed in the following order shown in FIG. (1) On the upstream side of the stirring / conveying unit 402, the supply unit 4
01, the developer recirculated from the recovery unit 403 and new toner are carried in, stirred and mixed by the stirring / conveying means 46, and conveyed in the developer moving direction indicated by the arrow V1.

(2) The mixed developer passes through the third opening 408 on the downstream side of the agitating / conveying unit 402, and then passes through the arrow V2.
Is introduced upstream of the supply unit 401.

(3) In the supply section 401, the developer is conveyed by the supply / conveying means 45 in the developer moving direction indicated by the arrow V3, and the supplying means 44 is indicated by the arrow V4.
Be transported to. The bulk density of the developer is detected by the developer bulk density detection sensor TK while the developer is being transported from the supply / transport means 45 to the supply means 44.

(4) The supply means 44 does not have a function of conveying in the direction of its rotation axis, and conveys the developer conveyed from the supply means 44 to the developer carrier 41 as shown by arrow V5.

(5) The developer on the developer carrying member 41 develops the electrostatic latent image on the photosensitive drum 1 in the developer region DR (see FIG. 2) facing the photosensitive drum 1. The developer indicated by the white arrow whose toner concentration has decreased due to the development is removed from the developer carrying member 41 by the arrow V by the peeling roller 47.
It is peeled off as shown in FIG. 6 and moves on the peeling roller 47.

(6) The collected developer on the stripping roller 47 is stripped off by the stripping plate 48 (see FIG. 2),
It is accommodated in the recovery unit 403 as shown by an arrow V7.

(7) The collected developer contained in the collecting section 403 is conveyed by the rotating collecting means 49 as shown by an arrow V8.

(8) The collected developer is collected in the collecting section 403.
It is discharged from the first opening 406 on the downstream side, and is supplied to the supply unit 401.
The image is carried in outside the image area on the downstream side of as shown by an arrow V9.

(9) The developer supplied to the first opening portion 406 of the supply portion 401 is conveyed as shown by an arrow V10, and after the toner concentration is detected by the toner concentration detection sensor TD, the second opening portion is opened. After passing through 407, it is introduced to the upstream side of the stirring / conveying unit 402 as indicated by an arrow V11.

(10) In the stirring / conveying unit 402, the toner replenishment means 5 replenishes the toner by the toner concentration detection signal from the toner concentration detection sensor TD, and the developer merges with the arrow V1.

The developer is conveyed by the circulation system as described above, but a part of the developer is supplied to the supply section 401 and the stirring / conveying section 402.
It circulates between them as shown by arrows V1, V3, V10, and V11.

As is clear from the above description, after the developer is collected from the developer carrying member 41 to the collecting section 403, the developer is not circulated to the supplying section 401 in the image region GR, as shown by an arrow V9. It circulates to the supply unit 401 outside the image region GR. Then, from the supply unit 401 to the developer carrier 41
After the toner is replenished, the developer conveyed to
It is sufficiently agitated in the transport section 402 and the supply section 401 to be homogenized.

For the developing device described above, it is preferable to use a two-component developer containing a non-magnetic polymerized toner and a small particle size magnetic carrier. As such a two-component developer, a two-component developer containing a carrier having a mass average particle diameter of 20 to 50 μm and a non-magnetic polymerized toner having a mass average particle diameter of 3 to 7 μm is particularly preferable. Agent carrier 41
It is preferable that the electrostatic latent image on the photosensitive drum 1 is developed by applying a developing bias in which an alternating electric field is superposed on.

The details of the small particle size polymerized toner and the carrier used for the two-component developer will be described below.

First, the polymerized toner used in the present invention will be described with reference to FIG. FIG. 5A is an explanatory diagram showing a projected image of polymerized toner particles without corners.
(B) and (C) are explanatory views showing projected images of polymerized toner particles each having corners.

The polymerized toner used in the present invention is
(1) Toner particles having a shape factor in the range of 1.2 to 1.6 are 65% by number or more, and the variation coefficient of the shape factor is 16
% Of polymerized toner particles,
(2) toner particles having a coefficient of variation of 16% or less and a coefficient of number variation of 27% or less in a number particle size distribution, (3) a ratio of polymerized toner particles having no corners of 50 It is preferable that the toner particles are composed of toner particles of which content is at least%, or a combination thereof.

In the present invention, the shape factor of the polymerized toner is represented by the following formula and represents the degree of roundness of the polymerized toner particles.

Shape factor = ((maximum diameter / 2) ² × π) / projected area Here, the maximum diameter is the parallel line when a projected image of toner particles on a plane is sandwiched by two parallel lines. Refers to the width of the particles at which the interval is maximum. The projected area means the area of the projected image of the toner particles on the plane.

In the present invention, this shape factor is determined by taking a photograph of the toner particles magnified 2000 times with a scanning electron microscope, and then, based on the photograph, "SCANNING" is used.
It was measured by analyzing a photographic image using "IMAGE ANALYZER" (manufactured by JEOL Ltd.). At this time, the shape factor of the present invention was measured by the above calculation formula using 100 toner particles.

In the polymerized toner used in the present invention, the number of toner particles having the shape factor in the range of 1.2 to 1.6 is preferably 65% by number or more, more preferably 70% by number or more. .

When the number of toner particles having the shape factor in the range of 1.2 to 1.6 is 65% by number or more, the triboelectrification property with carrier particles becomes more uniform,
Accumulation of excessively charged toner can be reduced, and toner can be more smoothly conveyed by carrier particles, so that problems such as development ghosts are less likely to occur. Further, the toner particles are less likely to be crushed, the contamination of the charging member (charging device) is reduced, and the charging property of the toner can be stabilized.

The method of controlling the shape factor is not particularly limited. For example, a method of spraying toner particles in a hot air stream, a method of repeatedly applying mechanical energy by impact force in a gas phase in a gas phase, or a method of adding a toner to a solvent that does not dissolve toner to give a swirling flow, etc. According to the method described above, a toner having a shape factor of 1.2 to 1.6 is prepared, and this is added to a normal toner so as to be within the range of the present invention, and then adjusted. Also, controlling the overall shape at the stage of adjusting the so-called polymerization method toner,
There is a method in which a toner whose shape factor is adjusted to 1.2 to 1.6 is similarly added to an ordinary toner to prepare.

The variation coefficient of the shape factor of the polymerized toner preferably used in the present invention is calculated from the following formula.

Coefficient of variation = (S / K) × 100 (%) In the formula, S represents the standard deviation of the shape factors of 100 toner particles, and K represents the average value of the shape factors.

In the polymerized toner used in the present invention, the variation coefficient of the shape factor is preferably 16% or less, more preferably 14% or less. When the variation coefficient of the shape factor is 16% or less, the voids of the transferred toner layer are reduced, the fixability is improved, and the offset is less likely to occur. In addition, the charge amount distribution becomes sharp and the image quality is improved.

In order to uniformly control the shape factor and the variation coefficient of the shape factor of the toner without extremely lot-to-lot variation, they are formed in the steps of polymerizing, fusing and controlling the shape of resin particles (polymer particles). An appropriate process end time may be determined while monitoring the characteristics of certain toner particles (colored particles).

Monitoring means that a measuring device is installed in-line and the process conditions are controlled based on the measurement result. That is, in the case of a polymerization toner in which measurement of a shape or the like is incorporated inline, for example, a resin toner is formed by associating or fusing resin particles in an aqueous medium, the shape and the particle size are measured while performing sequential sampling in the steps such as fusing. Is measured, and the reaction is stopped when the desired shape is obtained.

The monitoring method is not particularly limited, but a flow type particle image analyzer FPIA-
2000 (manufactured by Toa Medical Electronics Co., Ltd.) can be used. This device is suitable because the shape can be monitored by performing image processing in real time while passing the sample liquid. That is, a pump or the like is used from the reaction field to constantly monitor and measure the shape and the like, and the reaction is stopped when the desired shape or the like is obtained.

The number particle size distribution and number variation coefficient of the polymerized toner used in the present invention are measured by Coulter Counter TA-II or Coulter Multisizer (manufactured by Coulter Co.). In the present invention, a Coulter Multisizer was used, and an interface (manufactured by Nikkaki Co., Ltd.) for outputting the particle size distribution and a personal computer were connected and used. The aperture used in the Coulter Multisizer was 100 μm, and the volume and number of 2 μm or larger toners were measured to calculate the particle size distribution and mass average particle size. The number particle size distribution represents the relative frequency of toner particles with respect to the particle size, and the mass average particle size represents the median diameter in the number particle size distribution. The number variation coefficient in the number particle size distribution of the toner is calculated from the following formula.

Number variation coefficient = (S / Dn) × 100 (%) In the formula, S represents the standard deviation in the number particle size distribution,
Dn indicates a mass average particle diameter (μm).

In the polymerized toner used in the present invention, the number variation coefficient is preferably 27% or less, more preferably 25% or less. When the number variation coefficient is 27% or less, the voids of the transferred toner layer are reduced, the fixing property is improved, and the offset hardly occurs. Further, the charge amount distribution becomes sharp, the transfer efficiency is improved, and the image quality is improved.

The method of controlling the number variation coefficient is not particularly limited. For example, a method of classifying toner particles by wind force can be used, but classification in a liquid is effective for reducing the number variation coefficient. As a method of classifying in this liquid, there is a method of controlling the number of revolutions and separately collecting and preparing toner particles according to the difference in sedimentation speed caused by the difference in toner particle diameter.

Particularly when the toner is produced by the suspension polymerization method, the classification operation is indispensable in order to keep the number variation coefficient in the number particle size distribution at 27% or less. In the suspension polymerization method,
Before the polymerization, it is necessary to disperse the polymerizable monomer into an oil droplet having a desired size as a toner in an aqueous medium. That is, the large oil droplets of the polymerizable monomer are repeatedly mechanically sheared by a homomixer or a homogenizer to reduce the oil droplets to the size of toner particles. In the method of different shearing, the number particle size distribution of the obtained oil droplets becomes wide, and therefore,
The toner obtained by polymerizing this also has a wide particle size distribution. For this reason, classification operation is essential.

In the polymerized toner used in the present invention, the cornerless polymerized toner particles are toner particles having substantially no protrusions where electric charges are concentrated or protrusions which are easily worn by stress. That is, FIG.
As shown in (A), when the major axis of the toner particle T is L, a circle C having a radius (L / 10) is rolled inside while contacting the inner side at one point with respect to the peripheral line of the toner particle T. In this case, the case where the circle C does not substantially extend to the outside of the toner T is referred to as “a corner-free polymerized toner particle”. The term “when substantially not protruding” means a case where there is one or less protrusions with protruding circles. Further, the “major axis of the polymerized toner particles” refers to the width of the particles in which the distance between the parallel lines is maximum when the projected image of the polymerized toner particles on a plane is sandwiched by two parallel lines. In addition, FIG. 5 (B) and (C)
Shows projected images of polymerized toner particles each having corners.

The corner-free polymerized toner was measured as follows. First, an enlarged photograph of the polymerized toner particles was taken with a scanning electron microscope, and further magnified to 15,000.
A 0x photographic image is obtained. Then, the presence or absence of the above-mentioned corner is measured for this photographic image. This measurement was performed on 100 polymerized toner particles.

In the polymerized toner used in the present invention, the proportion of cornerless polymerized toner particles is preferably 50% by number or more, more preferably 70% by number or more. The percentage of polymerized toner particles without corners is 50% by number
By the above, the generation of fine particles due to stress with the carrier particles is less likely to occur, the adhesion of the carrier particles to the surface of the carrier particles can be prevented from being present excessively large, and to the carrier particles Contamination can be suppressed. In addition, the polymerized toner particles that are easily worn or broken and the polymerized toner particles that have a portion where electric charge is concentrated are reduced, the charge amount distribution becomes sharp, the chargeability is stable, and a high-quality image is stable for a long time. Can be formed as desired.

The method for obtaining the corner-free polymerized toner is not particularly limited. For example, as described above as a method of controlling the shape factor, a method of spraying toner particles in a hot air flow, a method of repeatedly applying mechanical energy due to impact force in a gas phase, or a method of dissolving toner It can be obtained by adding it to a solvent that does not contain it and imparting a swirling flow.

Further, in the polymerization toner formed by associating or fusing resin particles, the surface of the fused particles has many irregularities at the step of stopping the fusion, and the surface is not smooth, but the shape control step Corner-free toner particles can be obtained by appropriately adjusting the conditions such as the temperature, the rotating speed of the stirring blade, and the stirring time. These conditions are
Although it depends on the physical properties of the resin particles, for example, by setting the glass transition temperature of the resin particles or higher to a higher rotation speed, the surface becomes smooth and toner particles without corners can be formed.

The polymerized toner used in the present invention preferably has a mass average particle diameter of 3 to 7 μm. When the toner particles are formed by a polymerization method, the particle size of the polymerized toner can be controlled by the concentration of the aggregating agent, the addition weight of the organic solvent, the desorption time, and the composition of the polymer itself.

Since the mass average particle diameter of the polymerized toner is 3 to 7 μm, it is possible to reduce the presence of a toner having an excessively large adherence to the carrier or a toner having a low adherence in the fixing step, which is excellent. The developability can be stably obtained over a long period of time, the transfer efficiency is improved, the halftone image quality is improved, and the image quality of fine lines, dots, etc. is improved. Mass average particle size of polymerized toner is 3μ
If it is smaller than m, the image quality is apt to be deteriorated due to fogging, and if it is larger than 7 μm, the characteristic of high image quality becomes thin.

Particles used as a carrier are iron,
Conventionally known magnetic particles such as metals such as ferrite and magnetite and alloys of these metals with metals such as aluminum and lead can be used, and ferrite particles are particularly preferably used. The carrier particles used for the polymerized toner having a small particle diameter of 3 to 7 μm are preferably those having a small particle diameter of 20 to 50 μm as the mass average particle diameter. The mass average particle diameter of carrier particles is typically measured by a laser diffraction type particle size distribution measuring apparatus “HELOS” (sympathic (SY
Manufactured by MATETEC). As the carrier, the above magnetic particles can be used as they are, but a carrier coated with a resin or a so-called resin dispersion type carrier in which magnetic particles are dispersed in a resin is preferable. The resin composition for coating is not particularly limited, but for example, an olefin resin, a styrene resin, a styrene / acrylic resin, a silicon resin, an ester resin, a fluorine-containing polymer resin, or the like is used. The resin for forming the resin-dispersed carrier is not particularly limited, and known ones can be used. For example, styrene / acrylic resin, polyester resin, fluorine resin, phenol resin, etc. can be used. You can When the mass average particle diameter of the carrier is smaller than 20 μm, carrier adhesion is likely to occur, and the carrier is 50 μm.
If it is larger than the above range, deterioration of the image quality such as density unevenness called "crimping" is likely to occur in the image.

The developing device 4 is constructed as described above. When developing with a two-component developer comprising a toner having a small particle diameter and a carrier, the bulk of the developer, that is, the bulk density of the developer is used. 2 decreases, the supply capability of the developer carried on the developer carrier 41 by the supply unit 44 described above with reference to FIG. 2 decreases, and the developer carrying amount of the developer carrier 41 decreases, resulting in a decrease in the developability. Will decrease. In the present invention, in order to prevent this and compensate for the lowered developability, the ratio of the peripheral speeds of the developer carrying member 41 and the photosensitive drum 1, Vs / Vp, is increased to supplement the developability.

The control of developing property correction will be described below with reference to FIG. 6 or 7. As described above with reference to FIGS. 2 and 3, the toner concentration detection sensor TD for detecting the mixing ratio of the toner and the carrier of the two-component developer composed of the toner and the carrier having a small particle diameter, that is, the toner concentration is the same as that of the developing device 4. Inside the supply unit 401, at the bottom of the supply unit 401 on the downstream side of the developer transport, and a developer bulk density detection sensor TK for detecting the bulk of the developer, that is, the bulk density, is provided inside the supply unit 401 of the developing device 4. At the side surface of the lower frame 40A between the supply / conveyance means 45 and the supply means 44, the detection portion is attached so as to cover the upper portion of the developer. At this time, the developer bulk density detection is performed on the developer. By mounting the sensor TK vertically, the amount of the developer passing through the detection surface of the developer bulk density detection sensor TK varies depending on the size of the developer bulk density. Therefore, the output value of the developer bulk density detection sensor TK also changes. This allows the developer bulk density detection sensor TK to detect fluctuations in the bulk density of the developer.

However, only the lower frame 40A of the developing device 4 is
If the developer bulk density detection sensor TK is attached to the side surface of the developer bulk density detection sensor TK, the output of the fluctuation of the developer bulk density and the output of the toner concentration are confused, and the accurate volume density of the developer bulk density detection sensor TK Cannot be detected. Therefore, it is necessary to separate the output of the fluctuation of the developer bulk density and the output of the toner concentration.

Therefore, general environment (20 ° C., 50% RH)
The relationship between the detection value of the toner density detection sensor TD and the output of the developer bulk density detection sensor TK in FIG. 2 is grasped, and the ideal output value of the developer bulk density detection sensor TK is calculated from the detection value of the toner concentration detection sensor TD. A conversion formula to be estimated is prepared in advance, a reference table is prepared from the conversion formula, and the output value of the developer bulk density detection sensor TK is determined by referring to the reference table.

That is, as shown in FIG. 6, detection by the toner density detection sensor TD corresponding to the value of the temperature / humidity sensor TS for each environment of high temperature / high humidity, normal temperature / normal humidity and low temperature / low humidity and the number of copies by the number counter CT. Value and the developer bulk density detection sensor T corresponding to the detection value of the toner concentration detection sensor TD
The detected value of K is calculated and used as predicted data as an ideal value of the developer bulk density detection sensor TK, and a conversion formula and a reference table based on the conversion formula are created from the predicted data experimentally obtained in advance, and the conversion formula and The reference table is stored in the ROM of the storage unit and stored in the ROM of the storage unit and the detection value of the bulk density actually detected by the developer bulk density detection sensor TK when the image forming apparatus is used. The ideal value of the reference table is referred to, the output value of the developer bulk density detection sensor TK is determined based on the difference between the ideal value based on the reference table and the detected value of the bulk density actually detected, and the output value is determined according to the output value. And the peripheral speed ratio Vs / Vp between the developer carrying member 41 (developing roller) and the photosensitive drum 1 is determined, and the developing roller drive motor M2
And the peripheral speed ratio, Vs / V, by the photoconductor drive motor M1
By changing p, the fluctuation amount of the developer carrying amount of the developer carrying member 41 is corrected.

The timing of changing the peripheral speed ratio between the developer carrying member 41 and the photosensitive drum 1 and Vs / Vp by reading the output value of the developer bulk density detecting sensor TK from the reference table is the same as the one in the morning (image When the environmental movement is detected by the temperature / humidity sensor TS of the machine at the time of starting the forming apparatus), it is preferable to perform the following. Further, the ideal value (output value) is read from the reference table of the developer bulk density detection sensor TK by stirring the developer in the photoconductor drum 1 and the developing device 4 for about 1 minute, and then outputting the output value from the reference table. It is preferable to perform the correction control for changing the peripheral speed ratio between the developer carrying member 41 and the photosensitive drum 1 and Vs / Vp according to the output value after reading

Further, since the fluctuation of the bulk density due to the deterioration of the developer is also corrected, the rotation time of the developing roller is monitored, and a constant copy count, for example, 50 ksec or 100.
Correction control may be performed by preparing a reference table for converting the toner density detection sensor TD into the output value of the developer bulk density detection sensor TK every k · sec.

By the correction control described above, it is possible to provide a developing device capable of obtaining a constant developing property without being affected by environmental changes, the number of copies, or the standing time.

FIG. 7 shows an example of correction control of the developer bulk density detection sensor TK using the above reference table. FIG. 7 (A)
FIG. 7B shows the relationship between the toner concentration of the developer and the output value of the toner concentration detection sensor, FIG. 7B shows the relationship between the toner concentration of the developer and the bulk density, and FIG. 7C shows the volume of the developer. FIG. 7 shows the relationship between the density and the ideal output value of the developer bulk density detection sensor. If the output detected by the toner density detection sensor TD is 3.26V, the toner density at that time is as shown in FIG. From the conversion formula based on the experiment shown by the straight line in A), it is predicted to be 4% by mass. Next, from the conversion formula showing the relationship between the toner density and the bulk density (g / cm ³ ) of the developer based on the experiment shown by the straight line in FIG. 7B, the proper developing property is obtained when the toner concentration is 4 mass%. The bulk density of the developer required to obtain is 2.0
It can be predicted to be 4 g / cm ³ . The ideal output value that should be output by the developer bulk density detection sensor TK when the developer bulk density is appropriate is 2.25 V when calculated from the curve based on the experiment of FIG. 7C. From the difference between the ideal output value of the developer bulk density detection sensor TK and the actually detected output value of the developer bulk density detection sensor TK, the ratio of the peripheral speeds of the developer carrier and the image carrier, The developability is corrected by Vs / Vp.

(Examples) The following tests were conducted using the developing device shown in FIG. The main image forming conditions are as follows.

Test environment: General (22 ° C., 50% RH) Two-component developer: Carrier particles having a particle size of 50 μm are used as a carrier, and a particle size of 6.5 μm is used as a toner.
The toner density is adjusted to 6% by mass by using the cyan polymerized toner of m. The photoconductor drum is used. The OPC photoconductor is used. V for the difference between the output value of the developer bulk density sensor and the ideal value
The correction control of s / Vp (the peripheral speed ratio of the developing roller and the drum) was conducted by using the control method described above. Further, the peripheral speed Vs of the developing roller and the peripheral speed of the photosensitive drum are determined according to the difference between the ideal output value of the developer bulk density detection sensor TK and the actually detected output value of the developer bulk density detection sensor TK. Speed Vp, ratio of peripheral speeds of developer carrier and image carrier, Vs /
For the correction value (reference table) of Vp, an experiment was conducted based on Table 1 shown below.

[0098]

[Table 1]

In the experiment, a continuous copy test was conducted, and the maximum reflection density (Dma) of the image with respect to the rotation time of the developing roller was measured.
x) The stability of the developing property is measured, and the stability of the developer transport amount of the developing roller is measured by the amount of the developer adhering to the photosensitive drum (mg / cm ² ) with respect to the rotation time of the developing roller. did.

The measurement result when the correction control according to the present invention is performed is shown in the graph of FIG. 8B, and the measurement result when the correction control of the present invention is not performed is shown in the graph of FIG. 8A. The horizontal axis represents the developing roller rotation time (k · sec) during the continuous copy test, and the vertical axis represents the maximum reflection density (Dmax) with respect to the developing roller rotation time (k · sec) during the continuous copy test on the left side. Change, and on the right, the rotation time of the developing roller (k · se
Amount of developer adhered to the photosensitive drum for c) (mg /
The change in cm ² ) is shown.

As shown in FIG. 8 (B), when the correction control of the present invention is performed, the fluctuation range of the amount of developer adhering to the photosensitive drum (mg / cm ² ) during the continuous copy test is It was small, the amount of adhesion was constant and stable, the amount of developer conveyed by the developing roller was stabilized, and it was measured that the amount of conveyance was good. Further, the fluctuation range of the maximum reflection density (Dmax) in the continuous copy test is small, the maximum reflection density is constant and stable, and the developing property is stabilized by the developing roller, which indicates good developing property. Was measured. On the other hand, in the conventional method which does not use the correction control of the present invention, as shown in FIG. 8B, the amount of the developer adhering to the photosensitive drum (mg / cm ² ) during the continuous copy test is Maximum reflection density (Dmax) during change or continuous copy test
It was measured that there was variation in the value of (1), the fluctuation range was large and unstable, and the amount of developer conveyed by the developing roller and the developability were unstable.

[0102]

According to the present invention, when a two-component developer consisting of a toner having a small particle diameter and a carrier is used, a toner having a toner particle diameter of 7.0 μm or less and a corresponding toner particle diameter are Even when using a carrier of 50 μm or less, the predicted data as an ideal value is previously obtained from a sensor that detects the mixing ratio and a sensor that detects the bulk density of the two-component developer and that detects the magnetic permeability. And changing the peripheral speed ratio between the developer carrier and the image carrier according to the difference between the detection value of the sensor that detects the bulk of the developer and the ideal value of the predicted data. It is possible to make constant the amount of developer that is conveyed to the development area for a certain period of time,
It is possible to provide an image forming apparatus that can obtain a certain developing property without being affected by environmental changes, the number of copies, or leaving time.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional configuration diagram of a color image forming apparatus showing an embodiment of an image forming apparatus using a developing device according to the present invention.

FIG. 2 is a schematic cross-sectional configuration diagram showing an example of the developing device of FIG.

FIG. 3 is a front view of the developing device of FIG. 2 for explaining the flow of a two-component developer.

FIG. 4 is a diagram showing a method for measuring the bulk density of a two-component developer.

FIG. 5 is a diagram showing a projected image of polymerized toner particles.

FIG. 6 is a control block diagram of the developing device showing correction control of the present invention.

FIG. 7 is a diagram showing an example of a method of correcting the output value of the developer bulk density detection sensor based on the difference between the detection value detected by the developer bulk density detection sensor and the ideal value of the prediction data.

FIG. 8 is a graph showing the experimental results of the present invention and the conventional example concerning the transportability and the developability of the developer bearing member in the continuous copy test.

[Explanation of symbols]

1,1Y, 1M, 1C, 1K Photoconductor drum 4,4Y, 4M, 4C, 4K Developing device 41 developer carrier 42 Magnetic field generating means 43 Regulation means 44 Supplying means 45 supply / transport means 46 Agitating / transporting means 47 Stripping roller 49 Recovery means 401 supply unit 402 Agitator / transporter 403 Collection Department CT number counter TD toner density detection sensor TK developer bulk density detection sensor TS temperature and humidity sensor M1 photoconductor drive motor M2 developing roller drive motor

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G03G 15/08 507 G03G 15/08 507X 9/08 384 (72) Inventor Nobuyasu Tamura Ishikawa, Hachioji, Tokyo Machi 2970 Konica Stock Company F-term (Reference) 2H005 AB06 AB10 EA02 EA05 EA07 EA10 FA01 2H027 DA11 DA14 DA32 DA45 DD07 DE04 DE07 DE09 EA04 EA06 EB04 EC06 EC07 EC09 EC18 EC20 AD02 AC02 AC02 AC07 AC02 AC02 AC02 AC02 EA04 AE02 HI02 EF07 EA02 HI02 EF07 2 AD06 AD13 AD18 AD31 AD36 AE06 BA03 DA10 DA18 DA24 DA42 DA52 DA82 DB02 DB11 DB14 EA03 GA02 GA03 GA13 GA17

Claims (3)

[Claims] 1. A two-component developer prepared by mixing a latent image forming image carrier with a latent image into a visible image and mixing a toner and a carrier at a constant mixing ratio.
An image forming apparatus using a developing device having a developer carrying member for transporting a component developer to a developing area, wherein the developing device is provided with two sensors for detecting magnetic permeability, one of which is a mixture of toner and carrier. As a sensor for detecting the ratio, the other as a sensor for detecting the bulk of the developer, and the peripheral speed ratio between the image carrier and the developer carrier according to the output value of the sensor for detecting the bulk of the developer. An image forming apparatus characterized by changing the. 2. The image forming apparatus according to claim 1, wherein a toner having a polymerization prescription is used as the toner of the two-component developer. 3. The image forming apparatus according to claim 1, wherein the toner used in the two-component developer has a particle diameter of 7 μm or less, and the carrier has a particle diameter of 50 μm or less.