JP2002333774A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus in which the entire amount of developer in a developing device is sufficiently secured by securing developer feeding force even when the diameter of a supplying and feeding auger is made smaller. SOLUTION: In this image forming apparatus, the developer is carried on the surface of a rotationally driven developing roller and supplied to an electrostatic latent image on an image carrier so as to develop the latent image, and then the developer left after development on the surface of the developing roller is peeled and recovered. The image forming apparatus is equipped with a 1st feeding path for restoring the developer fed to the downstream end of a recovering auger to the outside of an image area on the downstream side of the supplying and feeding auger and a 2nd feeding path for restoring the developer fed to the downstream end of the recovering auger to a stirring auger.

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 such as an electrophotographic copying machine, a printer, a facsimile, and a multifunction peripheral having these functions, and more particularly, to an electrostatic latent image formed on an image carrier. The present invention relates to a mechanism for developing an image.

[0002]

2. Description of the Related Art In an electrophotographic image forming apparatus, there is known a technique for developing a latent image on the surface of a photoreceptor using a two-component developer adhered to the surface of a developing roller having a fixed magnetic pole. . The demand for downsizing the image forming apparatus has increased the need for downsizing the developing apparatus.

In a developing device, a developer developed by a developing roller is removed by a scraper which is in contact with or in close proximity to the developing roller and a repulsive magnetic field of a release pole, and this is removed by a new toner. There is an example of reflux near the supply site. In such an example, in order to avoid the adverse effect on the image quality due to the recirculated developer, the agitating section and the developer supply section are so arranged that the agitated developer and the removed developer are not mixed by the recirculation. And the developer collecting section are separated by a partition wall or the like.

For example, in a developing device, a developer stirring chamber, a developer supply chamber, and a developer recovery chamber are separated from each other, and the two-component developer is sufficiently stirred by a stirring auger in the developer stirring chamber. The developer is delivered to the developer supply chamber, the developer is supplied evenly along the axial direction of the developing roller by the supply transport auger of the developer supply chamber, the developing is performed by the developing roller, and a magnet is built in the developer collecting chamber. A carrier magnet roller is provided to collect the developer released from the developing roller.This time, the developer is peeled off from the surface of the carrier magnet roller by the release magnetic pole of the carrier magnet roller, and the peeled developer is collected by a collecting auger. There are examples of recovery and reflux.

In such an image forming apparatus, the size of the developing device can be reduced by reducing the diameter of the supply / conveyance auger. In a color image forming apparatus in which a plurality of developing devices are arranged, there is a high demand for a reduction in the size of the color image forming device. In particular, in a color image forming device in which a plurality of developing devices are arranged in a vertical direction, the color image forming apparatus is also required. As for the developing device, there is a higher demand for downsizing in the vertical direction than downsizing in the horizontal direction, and the reduction in the diameter of the supply and auger contributes greatly.

However, if the diameter of the supply / conveyer auger is reduced, there is an adverse effect such as a decrease in the conveying force and an insufficient supply of the developer to the developing roller. In order to solve this problem, it is conceivable to increase the number of rotations of the supply / conveyer auger. However, there is an upper limit on the number of rotations, and the number of rotations cannot be increased until sufficient conveyance performance is obtained.

In view of the above, two supply / conveyer augers having a reduced diameter are arranged in a developer supply chamber so as to be arranged in parallel to each other and to convey the developer in the same direction. The length is about the same as the width, and the supply and transport auger far from the developing roller extends out of the image area,
At the portion extended to outside the image area, the above-described recirculation and reception of new toner are performed. With such a configuration, it is expected that the contradictory effects of maintaining the transport force of the entire supply and transport auger and reducing the diameter are achieved.

Further, a toner density sensor which separately detects a change in toner density contained in a two-component developer as a change in inductance and outputs the output signal as a change in frequency or an output signal as a change in voltage value is known. There has been known a technique for controlling such that an appropriate toner density is maintained in accordance with an output signal of such a toner density sensor.

In such an image forming apparatus, the toner density is detected by disposing a toner density sensor a little downstream in the transport direction from the position where the collected developer recirculates.

[0010]

However, in a developing device using two supply / conveyor augers, the number of supply / conveyor augers is reduced to one outside the image area, so that the conveying force is reduced by half. As a bottleneck of the conveying force, the amount of the entire developer is regulated to be small. For example, it is extremely difficult to secure the conveying force for two screws even if the conveying force is secured by changing the screw pitch outside the image area.

If the amount of the developer present in the entire developing device is small, the image quality may be adversely affected due to the unstable supply of the developer or the susceptibility of the recirculated developer to the fluctuation of the toner concentration. Problems occur.

Accordingly, the present invention is directed to an image forming apparatus capable of securing a sufficient amount of developer and ensuring a sufficient amount of developer in the developing device even if the diameter of the supply / conveyor auger is reduced. The purpose is to provide.

Further, the toner concentration of the recirculated developer may be extremely low. In a developing device in which a toner density sensor is arranged slightly downstream in the transport direction from the position where the developer circulates, after developing at a high printing rate, the developer whose toner density has decreased recirculates, and the toner density sensor Since a signal corresponding to the decrease in toner density is output, the control unit instructs replenishment of new toner in order to maintain a predetermined toner density. On the other hand, at that time, the toner concentration in the developer at the developer supply portion to the developing roller is maintained at the predetermined toner concentration, and the portion where the toner concentration sensor is disposed and the developer supply portion to the developing roller are Causes a certain toner density difference.

When new toner is replenished under such conditions, the toner density of the toner density sensor unit is controlled so as to be a predetermined toner density. Is too high, the density of the developed image becomes too high, or the formed image is covered with toner or scattered.

SUMMARY OF THE INVENTION It is an object of the present invention to always supply a developer having a stable toner concentration to a developing roller regardless of a printing rate.

Another object of the present invention is to always supply a developer having a stable toner concentration to a developing roller by toner supply control according to a printing rate.

[0017]

SUMMARY OF THE INVENTION The object of the present invention is defined in claim 1.
Can be solved by the image forming apparatus described in (1). That is, in the image forming apparatus according to the first aspect, the developer is carried on the surface of the developing roller that is driven to rotate, and the developer is supplied to the electrostatic latent image on the image carrier to develop the image. An image forming apparatus for removing and collecting the developer remaining on the surface of the developing roller,
A supply transport auger that transports the developer in the axial direction and supplies the developer to the developing roller; and supplies and agitates the developer while transporting the developer in a direction opposite to the transport direction of the supply transport auger. A stirring auger to be supplied to the auger,
A collection auger that collects the stripped developer above the stirring auger and transports the developer in an axial direction to outside the image area; and a developer that is transported to a downstream end of the recovery auger on a downstream side of the supply transport auger. A first transport path returning outside the image area;
A second conveyance path for returning the developer to the stirring auger while being conveyed to the downstream end of the collection auger.

According to the image forming apparatus of the first aspect,
Even when the diameter of the supply / conveyer auger is reduced, the developer conveying force is ensured, and the entire amount of the developer in the developing device is sufficiently ensured. In addition, the detection deviation of the toner density, which tends to occur at a high printing rate, is also improved, so that it is possible to suppress fog, toner scattering, and an abnormal increase in the image density due to the increase in the toner density.

The object of the present invention can be solved by an image forming apparatus according to the present invention. That is, the image forming apparatus according to claim 2, wherein the first developer transport member transports the developer in the axial direction while stirring, and the first transport chamber in which the first developer transport member is disposed. A drop port provided downstream of the first developer transport member in the transport direction; a second developer transport member that transports the developer in the axial direction while stirring the developer; and a transport port that is transported by the second developer transport member. The second developer conveying member is arranged so that the developer to be conveyed and the developer conveyed to the first developer conveying member and dropped from the drop port merge, and the developer merges. The first position except at the merging position
A second transfer chamber separated from the first transfer chamber; and a merging position where the developer merges in the second transfer chamber or a toner concentration disposed upstream of the first developer conveying member in the conveying direction from the merging position. And a sensor.

According to the image forming apparatus of the second aspect,
The developer having a stable toner concentration was always supplied to the developing roller irrespective of the printing ratio.

Further, the object of the present invention can be solved by an image forming apparatus according to the present invention. That is, an image forming apparatus according to a seventh aspect is an image forming apparatus that develops an electrostatic latent image formed on an image carrier based on image data with a two-component developer containing toner, while stirring. A first developer transport member for transporting the developer in the axial direction, a first transport chamber in which the first developer transport member is arranged, and a first developer transport member provided downstream of the first developer transport member in the transport direction. A second developer transport member that transports the developer in the axial direction while stirring the developer,
The second developer conveying member is arranged such that the developer conveyed by the second developer conveying member and the developer conveyed by the first developer conveying member and dropped from the drop port merge. And a second transfer chamber separated from the first transfer chamber and a downstream of the first developer transfer member in the transfer direction of the first developer transfer member with respect to the second transfer chamber apart from the first transfer chamber at positions other than the merge position where the developer merges. A toner density sensor, a printing rate determining unit that determines a printing rate of the image data, a replenishing control unit that compares the output signal of the toner density sensor with a threshold value to determine whether toner replenishment is necessary, and a replenishing control unit. The toner replenishing unit for replenishing the toner according to the determination and the replenishment control unit change a determination factor according to the printing rate.

According to the image forming apparatus of the present invention,
By the toner supply control according to the printing rate, it has become possible to always supply the developer having a stable toner concentration to the developing roller.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As a first embodiment of the present invention, a configuration of a color copying machine as an example of an image forming apparatus having a plurality of developing devices mounted thereon will be described. FIG. 1 is a configuration diagram of the color copying machine.

This image forming apparatus is called a tandem type color image forming apparatus, and includes a plurality of sets of image forming units 10Y, 10M, 10C, and 10K, a belt-like intermediate transfer body 6, a sheet feeding and conveying means 20, And a fixing device 23. A document image reading device SC is arranged in an upper portion inside the image forming apparatus main body.

The image forming unit 10Y for forming a yellow image has a charging unit 2Y, an exposing unit 3Y, a developing unit 4Y, and a cleaning unit 8Y arranged around the photoreceptor 1Y. The image forming unit 10M that forms a magenta image has a photoconductor 1M, a charging unit 2M, an exposing unit 3M, a developing device 4M, and a cleaning unit 8M.
The image forming unit 10C that forms a cyan image includes:
Photoconductor 1C, charging means 2C, exposure means 3C, developing device 4
C, and has cleaning means 8C. An image forming unit 10K for forming a black image includes a photoconductor 1K, a charging unit 2
K, exposure means 3K, developing device 4K, cleaning means 8
K.

As the charging means 2Y, 2M, 2C and 2K, a scorotron discharger or the like can be adopted. Exposure means 3Y, 3M,
For 3C and 3K, a scanning exposure device that scans a laser beam with a polygon mirror can be adopted. Cleaning means 8
For Y, 8M, 8C, and 8K, a rubber blade or the like can be adopted.

As the document image reading device SC, a scanner device that generates image data color-separated based on a document by photoelectrically converting image information read optically can be employed. Each image forming unit 10Y, 10M, 10C, 10
K denotes a toner image formed by the electrophotographic method according to image data generated by the original image reading device SC.
Develop on 1M, 1C, 1K surfaces. not to mention,
The photoreceptor 1Y develops a yellow toner image, the photoreceptor 1M develops a magenta toner image, the photoreceptor 1C develops a cyan toner image, and the photoreceptor 1K develops a black toner image.

The intermediate transfer member 6 is wound around a plurality of rollers and is rotatably supported. Image forming unit 1
The toner images of the respective colors developed by 0Y, 10M, 10C and 10K are transferred onto a rotating intermediate transfer body 6 by transfer means 7
Y, 7M, 7C, and 7K sequentially transfer (primary transfer), and a combined color image is formed. The sheet P accommodated in the sheet cassette 25 is picked up by the pickup roller 2.
1 and is conveyed to the transfer means 7A via a plurality of intermediate rollers and registration rollers 22 to transfer a color image onto the sheet P (secondary transfer). The paper P to which the color image has been transferred is subjected to a fixing process by a fixing device 23, and is sandwiched by paper discharge rollers 24 and placed on a paper discharge tray outside the apparatus.

On the other hand, after the color image is transferred onto the sheet P by the transfer means 7A, the intermediate transfer member 6 obtained by separating the sheet P by curvature is used.
The remaining toner is removed by the cleaning means 8A.

The toner supply units 5Y, 5M, 5C and 5K are
Has a toner bottle filled with new toner,
New toner is supplied to each of the developing devices 4Y, 4M, 4C, and 4K. The toner supply paths from the toner supply units 5Y, 5M, 5C, and 5K to the developing devices 4Y, 4M, 4C, and 4K are omitted.

FIG. 2 is a central sectional view of the developing device 4, and FIG. 3 is a schematic view of the developing device 4 as viewed from above.

In these figures, F indicates a front side of the developing device 4 and R indicates a back side of the developing device 4. Hereinafter, the photoconductors 1Y, 1M, 1C, and 1K will be referred to as a photoconductor 1 as a representative.
Developing device 4 on behalf of developing devices 4Y, 4M, 4C, and 4K
Called. The toner supply units 5Y, 5M, 5C, and 5K will be referred to as toner supply units 5 as representatives.

The developing device 4 includes a developing device main body 40, a developing roller 41, a cutting member 42, a first supply / conveyer auger 43,
It comprises a second supply and transport auger 44, a stirring auger 45, a recovery auger 46, a transport magnet roller 47, a scraper 48 and the like.

The developing roller 41 is disposed so as to face the photoconductor 1 carrying an electrostatic latent image. The photoconductor 1 is an example of the image carrier of the present invention. The developing roller 41 includes a rotatable developing sleeve 41 a which is a cylindrical conductor and a developing sleeve 4.
1a includes a fixed magnetic pole 41b built therein, and performs contact development by a magnetic pole fixed developing method using a two-component developer.

The fixed magnetic pole 41b is disposed inside the developing sleeve 41a, and includes a plurality of magnetic poles N1, N2, N3, N4.
It has S1, S2, and S3. Magnetic pole N4 for receiving developer
Sucks the developer supplied by the first supply and transport auger 43 and causes the developer to adhere to the surface of the developing roller 41. The developer adhering to the surface of the developing roller 41 passes through a gap with the photoconductor 1 according to the rotation of the developing roller 41, and when passing through, a part of the toner in the developer is used for development on the photoconductor 1. . Further, the developer containing the toner not used for the development reaches the release magnetic pole N3 according to the rotation of the developing roller 41 while adhering.

Two magnetic poles N3 and N4 adjacent to each other among the plurality of magnetic poles of the fixed magnetic pole 41b are arranged at the same polarity (N pole) to form a repulsive magnetic field. Of these, the magnetic pole N3 is
The release magnetic pole N3 is used to peel off and scatter the developer on the developing roller 41 by such a repulsive magnetic field. The surface of the developing roller 41 is nothing but the surface of the developing sleeve 41a.

The tipping member 42 is a developer regulating member which has a constant gap with the surface of the developing roller 41 and regulates the amount of developer supplied to the developing roller 41.

Each of the first supply and transport auger 43, the second supply and transport auger 44, the stirring auger 45, and the recovery auger 46 is a spiral screw-type auger, which transports the developer in the axial direction and substantially rotates the rotary shaft. The developer is released at right angles.

Of these, the first supply and transport auger 43 and the second supply and transport auger 44 have a screw outer diameter, a shaft diameter,
The configuration is such that the same conveying force is obtained with the same pitch and rotation speed. Further, the first supply / conveyance auger 43 and the second supply / conveyance auger 44 convey the developer in the same direction because the rotation axes thereof are parallel to each other and the screw advances in the same direction. If the conveyance directions are the same, the directions of rotation of the screws may be different from each other. Further, if the conveyance is the same, the outer diameter, the shaft diameter, the pitch, and the number of rotations of the screws may not be the same.

The mutual length and arrangement of the first supply and transport auger 43 and the second supply and transport auger 44 will be described later with reference to FIG.

The transport magnet roller 47 is an example of a means for stripping and transporting, and includes a rotatable front roller 47a which is a cylindrical conductor, and a plurality of magnetic poles N11 and N12 disposed inside the front roller 47a. , N13, S11,
S12 is provided. The magnetic pole S11 is a receiving magnetic pole,
The developing roller 41 is disposed at a position slightly downstream of the position facing the release magnetic pole N3 in the developer conveying direction of the developing roller 41. The magnetic pole S11 sucks the developer stripped and scattered by the release magnetic pole N3 of the developing roller 41,
It is adhered on the surface of the front roller 47a.

Two magnetic poles N12 and N13 adjacent to each other among a plurality of magnetic poles are arranged with the same polarity (N pole) to form a repulsive magnetic field. The release magnetic pole N12 peels off and scatters the developer on the front roller 47a by such a repulsive magnetic field.

The scraper 48 has an elastic plate abutted along a substantially tangential direction of the transport magnet roller 47. Further, the scraper 48 may be configured to be disposed close to the transport magnet roller 47. Scraper 48
Removes the developer that cannot be peeled and scattered by the release magnetic pole N12. Further, the scraper 48 is disposed so as to extend from the transport magnet roller 47 to the collection auger 46, and is further inclined and disposed so as to be high near the transport magnet roller 47 and low near the recovery auger 46.
As a result, the stripped developer or the developer stripped and scattered by the release magnetic pole N12 slides down the surface of the scraper 48 and reaches the collection auger 46.

The scraper 48 is a means for stripping the developer from the transporting magnet roller 47 and guiding the stripped developer to the collecting auger 46.
Stripping is assured.

The collecting auger 46 conveys the developer slid down the surface of the scraper 48 toward the downstream of the collecting auger 46 in the conveying direction.

Around the developing roller 41, a first supply / conveyor auger 43, a spike member 42, the photosensitive member 1, and a conveying magnet roller 47 are arranged in this order from the upstream side in the developer conveying direction.

The developing device main body 40 supports a first supply / conveyance auger 43, a second supply / conveyance auger 44, and a stirring auger 45, and a lower main body 40A, and supports a collection auger 46, a conveyance magnet roller 47, and a scraper 48. A middle body 40B for closing the upper opening of the main body 40A and a cover 40C for closing the upper opening of the middle body 40B are provided.

The lower main body 40A is provided with a first supply / transfer auger 43.
Developer supply chamber 4 accommodating the second supply conveyance auger 44
01 and a developer stirring chamber 402 containing a stirring auger 45.
The developer supply chamber 401 and the developer stirring chamber 402 are formed on both sides of a first partition 404 that stands upright from the bottom of the lower main body 40A.

The middle main body 40B has a developer collecting chamber 403 for accommodating the collecting auger 46 and the conveying magnet roller 47, and a second partition 405 formed at the bottom of the middle main body 40B.
Separates the developer supply chamber 401 and the developer recovery chamber 403. A part of the middle main body 40B closes an upper opening of the developer stirring chamber 402. With such a configuration, the lower body 40
A, the middle body 40B, and the lid 40C are separated from each other.

A first opening 406 for circulating the collected developer from the developer collection chamber 403 to the developer supply chamber 401 is provided.
The developer that is provided on the second partition 405 and reaches the downstream end of the recovery auger 46 sequentially falls from the first opening 406 and flows back to the developer supply chamber 401. The situation where the developer drops from the first opening 406 is schematically indicated by an arrow E. The first opening 406 is an example of a first transport path of the present invention.

The middle main body 40B is provided with a bypass passage 411 for circulating the collected developer from the developer collection chamber 403 to the developer stirring chamber 402. The bypass path 411 is an example of the second transport path of the present invention, and includes two bypass openings 407a and 407b and a bypass opening 407a.
And 407b. The bypass opening 407a and the bypass opening 407b are provided outside the image area, and the transport state of the developer by the bypass path 411 is schematically indicated by an arrow H.
The transport direction of the second supply transport auger 44 is a direction substantially orthogonal to the transport direction.

In the present embodiment, the bypass opening 4
In the example described above, the developer supply chamber 401 is separated from the developer recovery chamber 403 and the developer agitation chamber 402, so that the bypass opening 407a and the developer supply chamber 401 are separated from each other. Both or one of the bypass opening 407b may be provided inside the image area.

The bypass path 411 does not particularly have a transport mechanism for transporting the developer, and the developer that has reached the downstream end of the recovery auger 46 is sequentially pushed out of the developer recovery chamber 403 and passes through the bypass path 411. Through the developer stirring chamber 4
Reflux at 02.

The toner density sensor 51 is a sensor that detects the toner density in the developer and outputs a detection signal.

To detect the toner density, an L (reactance) detecting toner density sensor composed of a coil is installed at a position close to the two-component developer, and the magnetic permeability of the two-component developer is measured. A method of knowing the density (the mixing ratio of the toner in the two-component developer) is known. The method based on the measurement of magnetic permeability is excellent in that it can be measured at all times and there is no need to change the image forming process.

The toner density sensor 51 includes an oscillation circuit including a coil and a frequency / voltage conversion circuit. The relationship between the toner density and the output voltage is such that the smaller the toner density, the higher the output voltage. I have. Toner density sensor 5
Numeral 1 has a control voltage input terminal, and the output voltage of the density sensor can be adjusted by changing the control voltage applied to this input terminal. The toner concentration sensor 51 detects that the developer circulating from the developer collection chamber 403 is in the developer supply chamber 40.
It is arranged slightly downstream of the position where it merges into 1.

Next, the developing device of FIG. 3 will be described with reference to a schematic diagram as viewed from above. In the figure, the opening and a part of the member supported by the lower main body 40A are indicated by broken lines.

The first supply and transport auger 43 and the second supply and transport auger 44 have different axial lengths. The first supply / conveyor auger 43 has substantially the same dimension as the length of the developing roller 41 in the axial direction, and is arranged so as to supply (discharge) the developer to the developing roller 41 over the entire length thereof. is there. The second supply and transport auger 44 has an axial length larger than that of the first supply and transport auger 43 and protrudes greatly from the first supply and transport auger 43 on both the downstream side and the upstream side in the transport direction.

First opening 406 and bypass opening 407
“a” (see FIG. 2) is provided at a position in phase with the screw pitch of the second supply / conveyance auger 44. Therefore, all of the developer that has reached the downstream end of the collection auger 46 does not drop at the first opening 406, and part of the developer is pushed out to the bypass path 411. The collected developer is the first
If it is configured to divide the flow into the opening 406 and the bypass path 411, the first opening 406 and the bypass opening 407a are not limited to the same phase.

The vicinity of the collecting auger 46 corresponds to the developer collecting chamber 403 (see FIG. 2), which is not shown.
Also, a second partition 405 between the collection auger 46 and the second supply / conveyance auger 44 is not shown. The direction in which the developer is transported by the second supply and transport auger 44 is indicated by an arrow K pointing downstream in the transport direction. The direction of transport of the developer by the stirring auger 45 is indicated by an arrow L pointing downstream in the transport direction. Regarding the transport direction of the developer by the collection auger 46,
An arrow M pointing downstream in the transport direction is shown.

The downstream side of the developer recovery chamber 403 (see FIG. 2) and the downstream side of the developer supply chamber 401 are conveyed near the end of the second partition 405 (see FIG. 2). The first openings 406 provided communicate with each other. The first opening 406 is arranged outside the image area d (non-image area). The image area d is an area in which development from the developing roller 41 to the photoconductor 1 is performed, and has a width substantially matching the axial length of the developing roller 41 in the present embodiment.

The downstream side of the developer supply chamber 401 and the upstream side of the developer agitating chamber 402 are connected to the first recirculation port 40 formed near one end of the first partition 404.
8 communicates.

The downstream side of the developer transport of the developer stirring chamber 402 and the upstream side of the developer transport of the developer supply chamber 401 are connected to the second recirculation port 40 formed near the other end of the first partition 404.
9 communicates.

A toner replenishing port 410 for replenishing new toner from the toner replenishing section 5 is provided upstream of the developer stirring chamber 402.
Is provided.

When new toner is supplied from the toner supply port 410 to the upstream portion of the stirring auger 45, the supplied new toner is sufficiently stirred with the developer already existing in the developer stirring chamber 402. Such stirring ensures sufficient triboelectric charging and uniform distribution of the toner. The developer sufficiently stirred after the replenishment of the new toner is introduced into the upstream part of the second supply / conveyance auger 44 at the downstream part of the stirring auger 45. The developer introduced from the agitation auger 45 to the upstream portion of the second supply / conveyance auger 44 is partially conveyed to the first supply / conveyance auger 43 while being conveyed by the second supply / conveyance auger 44. The developer that has not been introduced from the second supply / conveyance auger 43 into the first supply / conveyance auger 43 flows back from the downstream portion of the second supply / conveyance auger 44 to the upstream portion of the stirring auger 45 through the first circulation port 408.

The developer introduced into the first supply / conveyer auger 43 is supplied to the developing roller 41 and adheres to the surface of the developing roller 41. Further, a part of the developer introduced into the first supply / conveyance auger 43 is extruded as it is in the conveyance direction without being supplied to the developing roller 41, and the second supply / conveyance auger 4
Reflux to 4.

The developer adhering to the developing roller 41 is used for development on the surface of the photoreceptor 1, and after the development, the developing roller 4
The magnetic flux reaches the release magnetic pole N3 (see FIG. 2) while being attached to the magnetic pole N1.

The developer adhered to the developing roller 41 is peeled and scattered by the release magnetic pole N3,
7 (shown by a solid line), peeling and scattering by the release magnetic pole N12, and a part of the developer further reaches the collecting auger 46 by peeling off by the scraper 48.

The developer that has reached the collecting auger 46 is gradually conveyed to the downstream side inside the developer collecting chamber 403 and
When the developer reaches the opening 406, it falls into the developer supply chamber 401 below the developer recovery chamber 403 and circulates (arrow S).
Further, part of the developer conveyed to the downstream side of the developer collection chamber 403 by the collection auger 46 is supplied to the bypass path 411.
When the toner reaches the bypass opening 407b via the nozzle 407, the developer drops into the developer stirring chamber 402 and circulates (arrow R).

The developer collected by the reflux shown by the arrow S is supplied to the developer supply chamber 40 at the position of the first opening 406.
Merge into one developer. Therefore, such a position is an example of the merging position of the present invention. Further, the second supply / conveyor auger 44 supplies the developer to the developing roller 41 on the upstream side in the conveyance direction from the merging position P1 (described later in FIG. 4).

The arrangement of the first opening 406 is such that the collected developer circulates outside the image area of the developing roller 41 on the downstream side in the transport direction of the second supply and transport auger 44. The transport direction of the second supply and transport auger 44 and the recovery auger 46 match, and the developer circulating from the first opening 406 flows first downstream of the first opening 406 in the transport direction. The mouth 408 is reached.

In this embodiment, the bypass opening 407
The arrangement of b is such that the collected developer is arranged to recirculate on the upstream side in the transport direction of the stirring auger 45, but the present invention is not limited to this, and the collected developer includes the image area d.
It may be recirculated to any position of the stirring auger 45.

The first opening 406, the first reflux port 408,
It is preferable that each of the second circulation ports 409 is arranged in a non-image area of the developing roller 41.

Next, the state of the toner density inside the developing device 4 will be described with reference to Table 1 which compares this embodiment with the conventional example.

[0075]

[Table 1]

In Table 1, the printing rate (%) is a value indicating the number of pixels for which exposure is performed with respect to the total number of pixels per page as a percentage ((number of pixels for which exposure is performed / number of all pixels)).
× 100) and the density (toner attachment amount) of each pixel adjusted by pulse width modulation (PWM). The density of each pixel is x / 2 in the case of an image forming apparatus that reproduces, for example, 256 gradations by PWM.
It can be expressed as a fraction such as 56 or a value obtained by converting the fraction into a percentage. The toner concentration (%) indicates the concentration of the toner contained in the two-component developer in percentage by mass.

There are two actual measurement points of the toner density, that is, the position where the toner density sensor 51 is disposed and the supply position. The supply position is an upstream portion of the developer supply chamber 401 in the transport direction, and this point can be treated as a representative value of the entire image area d.

As shown in Table 1, in the present embodiment, the toner density inside the developing device 4 is 6.0 (%) at the toner density sensor position,
The toner density at the supply position is 6.0 (%) and the printing rate is 30%
In the case of, the toner concentration at the supply position is 6.2 (%),
When the printing rate is 90%, the toner density at the supply position is 6.4 (%).

On the other hand, in the conventional example, the toner density inside the developing device is 6.0 at the toner density sensor position.
(%), When the printing rate is 5%, the toner density at the supply position is 6.0 (%), and when the printing rate is 30%, the toner density at the supply position is 6.3 (%). ), When the printing rate is 90%, the toner density at the supply position is 6.8 (%).

When the first embodiment is compared with the conventional example, the measured value of the toner density at the supply position is significantly different when the printing rate is high. That is, at a printing rate of 90%, the toner density at the supply position is 6.4% in the present embodiment, and 6.8% in the conventional example. That is, the detection deviation of the toner concentration by the toner concentration sensor which is likely to occur at a high printing rate is improved by about 0.4% from the conventional example according to the present embodiment.

As described above, in the present embodiment, the developer supply chamber 401, the developer stirring chamber 402, the developer collection chamber 40
3 are separated from each other, and the flow of the developer between the developer supply chamber 401 and the developer stirring chamber 402 is limited to the first reflux port 408 and the second reflux port 409. From the collection chamber 403, the first supply port 406 is connected to the developer supply chamber 4.
01 and a bypass opening 40
7a and 407b, which flow back to the developer stirring chamber 402
Transport path. Therefore, the transportation route of the developer is limited, and adverse effects such as accidental mixing of the developer to be reused are avoided. Further, the collected developer is passed through a bypass path 4.
11 and the first recirculation port 408. Therefore, the first supply and transport auger 43 and the second supply and transport auger 4
Since no stagnation occurs at the junction of No. 4 and the junction does not become a bottleneck of the conveying force, the total amount of the developer circulating in the entire developing device can be increased as compared with the conventional example.

Therefore, according to the image forming apparatus of the first embodiment, even if the diameter of the supply / conveyer auger is reduced, the developer conveying force is secured, and the amount of the entire developer in the developing device is sufficiently increased. It was decided to secure.

In addition, since the detection deviation of the toner density, which tends to occur at a high printing rate, is also improved, it is possible to suppress fog, toner scattering, and an abnormal increase in the image density due to the increase in the toner density.

Next, a second embodiment of the present invention will be described.
A description will be given based on a rear view schematically showing the developing device of FIG. FIG. 4 shows the developing device 4 from the direction of the arrow G in FIGS.
This shows a state in which a is viewed.

In FIG. 4, the developing device 4a has substantially the same configuration as the developing device 4 described in the first embodiment, but the bypass path 411 and the bypass opening 407 are provided.
The developing device 4 is different from the developing device 4 in that the developing device a and 407b are not provided. The developer collected by the collecting auger 46 flows to the developer supply chamber 401 from one location of the first opening 406. or,
The developing devices 4a represent four developing devices corresponding to four colors.

In FIG. 4, the developing roller 41 (shown by a dotted line) of the developing device 4a includes a second supply / conveyor auger 44, a recovery auger 46, a developer supply chamber 401, and a developer recovery chamber 40
3, the second partition 405, the first opening 406, and the toner density sensor 51 are shown. The developer collected by the collecting auger 46 drops from the first opening 406 and joins the developer in the developer supply chamber 401 at the joining position P1.

The merging position P1 is set at the second supply / transport auger 44.
Is provided downstream of the region for supplying the developer to the developing roller 41, so that the second supply / conveyor auger 44 supplies the developer to the developing roller 41 upstream of the junction P1.

The second supply / conveyer auger 44 is an example of the second developer conveying member of the present invention, the recovery auger 46 is an example of the first developer conveying member of the present invention, and the first opening 406 is the present invention. , The developer supply chamber 401 is an example of the second transport chamber of the present invention, and the developer recovery chamber 403 is the first transport chamber of the present invention.
1 is an example of a transfer chamber.

The toner density sensor 51 is arranged upstream of the merging position P1 in the transport direction (arrow K) and downstream of the image area d.

Table 2 shows the toner density inside the developing device 4a when the arrangement of the toner density sensor 51 is as shown in FIG.

[0091]

[Table 2]

In Table 2, the printing rate (%) and the toner density (%) are shown.
Are the same parameters as in Table 1 and will not be described.

The actual measurement points of the toner density are at two positions, that is, the toner density sensor position and the supply position. As shown in FIG. 4, the position of the toner concentration sensor is upstream of the second supply / transport auger 44 in the transport direction including the position where the developer circulating from the developer recovery chamber 403 joins the developer supply chamber 401. . The supply position is an upstream portion of the developer supply chamber 401 in the transport direction, but this point can be treated as a representative value of the entire image area d.

As shown in Table 2, in this embodiment, when the toner density inside the developing device 4a is 6.0 (%) at the toner density sensor position, regardless of the printing rate, the toner density at the supply position is The concentration is 6.0 (%).

On the other hand, in the conventional example, the toner density inside the developing device is 6.0 at the toner density sensor position.
(%), When the printing rate is 5%, the toner density at the supply position is 6.0 (%), and when the printing rate is 30%, the toner density at the supply position is 6.3 (%). ), When the printing rate is 90%, the toner density at the supply position is 6.8 (%).

When the present embodiment is compared with the conventional example, the present embodiment does not cause the detection deviation of the toner density irrespective of the printing rate, but in the conventional example, the higher the printing rate, the higher the toner density. Detection deviation is large.

Therefore, according to the image forming apparatus of the second embodiment, the detection result of the toner concentration by the toner concentration sensor 51 is not affected by the sudden change in the toner concentration when the collected developer flows. Therefore, since excessive toner replenishment can be suppressed, problems such as an increase in image density, fogging and toner scattering can be suppressed.

In the second embodiment, an example has been described in which the output voltage of the toner density sensor 51 changes in accordance with the toner density. However, the frequency / voltage conversion circuit is omitted, and the output is performed in accordance with the toner density. It is also possible to use a sensor whose frequency changes.

In FIG. 4, the position of the toner density sensor 51 is located upstream of the merging position P1 in the transport direction (arrow K) and downstream of the image area d. As shown, the toner concentration sensor 51 may be arranged in the same phase as the merging position P1. In this way, when the toner is arranged in the same phase, the developer circulating from the developer recovery chamber 403 is slightly transported by the second supply and transport auger 44, so that the detection result of the toner density sensor 51 is not affected. FIG. 5 is a rear view schematically showing the developing device, and is the same as FIG. 4 except that the position of the toner density sensor 51 is changed from FIG.

Next, a third embodiment of the present invention will be described.
A description will be given based on a rear view schematically showing the developing device of FIG. 6 and a control block diagram of the toner supply control of FIG. The third embodiment is an example in which the threshold value of the toner supply control is changed according to the printing rate.

The third embodiment shown in FIG. 6 is different from the second embodiment shown in FIG. 4 in that the position of the toner density sensor 51 is changed.

In FIG. 6, although the developing device 4b has substantially the same configuration as the developing device 4a described in the second embodiment, the arrangement of the toner density sensor 51 is different from that of the developing device 4a.
a. The other configuration is the same as that of the developing device 4, and a duplicate description will be omitted.

The second supply and transport auger 44 is an example of the second developer transport member of the present invention, the recovery auger 46 is an example of the first developer transport member of the present invention, and the first opening 406 is the present invention. , The developer supply chamber 401 is an example of the second transport chamber of the present invention, and the developer recovery chamber 403 is the first transport chamber of the present invention.
It is the same in that it is an example of the transfer chamber.

In FIG. 6, the developer collected by the collecting auger 46 provided in the developing device 4b is supplied to the first opening 406.
The developer further drops and joins the developer in the developer supply chamber 401 at the joining position P1.

[0105] The merging position P1 is the
Is provided downstream of the region for supplying the developer to the developing roller 41, so that the second supply / conveyor auger 44 supplies the developer to the developing roller 41 upstream of the junction P1.

The toner density sensor 51 is arranged downstream of the merging position P1 in the transport direction (arrow K).

Next, FIG. 7 is a control block diagram of a control system for executing toner supply according to the output of the toner density sensor 51.

The control unit 50 includes a replenishment control unit 52, a printing rate determination unit 53, and a table storage unit 54.
Is connected to the toner density sensor 51 and the toner replenishing unit 5.

The toner replenishing section 5 stores unused toner (new toner), and replenishes unused toner to the developing device 4b according to a toner replenishment signal generated by the replenishment control section 52. The technology for storing unused toner and the technology for replenishing the developing device 4b with the toner are well known, and therefore detailed description is omitted.

The printing ratio determining section 53 is a block for analyzing the image data generated by the document image reading device SC and calculating the above-mentioned printing ratio. In the present embodiment, the printing rate is calculated for each page.

The table storage section 54 is a non-volatile memory for storing table data relating to a threshold value corresponding to the printing rate. Table 3 is an example of table data relating to the threshold. The threshold is an example of the judgment factor of the present invention.

[0112]

[Table 3]

In Table 3, the printing rate has already been described in Table 1, and the threshold value is a threshold value for determining whether or not the toner replenishment operation can be performed, and is determined by the output voltage of the toner density sensor 51.

The replenishment control unit 52 can change the threshold value according to the printing rate obtained from the printing rate determination unit 53 with reference to the table data in the table storage unit 54. , A toner supply signal is issued. That is, the replenishment control unit 52 determines whether or not toner replenishment is necessary based on the threshold, and issues a toner replenishment signal when it is determined necessary.

For example, when the printing rate of a page on which image formation is to be performed is 11 to 40%, the replenishment control unit 52, which has obtained the printing rate from the printing rate determination unit 53, refers to the table data in the table storage unit 54. The threshold is set to 2.3V. When the output voltage of the toner density sensor 51 falls below 2.3 V during the execution of image formation or the like, the replenishment control unit 52 issues a toner replenishment signal, and the toner replenishment unit 5 replenishes the developing device 4b with new toner.

As described above, the toner density sensor 5
Reference numeral 1 denotes a negative characteristic in which the output voltage increases as the toner density decreases. To increase the threshold, the toner supply control is performed to decrease the toner density. Conversely, when the threshold is decreased, the toner density is reduced. The toner replenishment control is set to be higher.

In the present embodiment, when the developer in the developer collection chamber 403 joins the developer supply chamber 401, if the toner concentration of the developer in the developer collection chamber 403 is low, the developer is temporarily joined. The developer concentration at the position P1 is greatly reduced. This is a state in which the toner concentration at the joining position P1 is locally reduced with respect to the toner concentration of the entire developer circulating in the developing device 4b. When the printing rate is high, the toner density of the collected developer becomes low. Therefore, in the present embodiment, the threshold value is changed according to the printing rate with reference to the table data, and the toner density of the locally generated toner density is changed. In the case of a decrease, the toner supply is not performed.

Table 4 shows the toner density inside the developing device 4b in the case where the threshold value of the toner replenishment control is changed according to the printing rate as described above.

[0119]

[Table 4]

In Table 4, the printing rate (%) and the toner density (%) are shown.
Are the same parameters as in Table 1 and will not be described.

The actual measurement points of the toner density are at two positions: the toner density sensor position and the supply position. As shown in FIG. 4, the position of the toner concentration sensor is slightly downstream of the position where the developer circulating from the developer collection chamber 403 joins the developer supply chamber 401. The supply position is an upstream portion of the developer supply chamber 401 in the transport direction, but this point can be treated as a representative value of the entire image area d.

As shown in Table 4, in the present embodiment, when the toner density inside the developing device 4b is 6.0 (%) at the toner density sensor position, the printing rate is 0 to 10% at the supply position. The toner density is 6.0 (%) and the printing ratio is 11 to 4.
At 0%, the toner concentration at the supply position is 5.8 to 6.2.
(%), The toner density at the supply position at a print rate of 41 to 70% is 5.8 to 6.2 (%), and the toner density at the supply position at a print rate of 71% to 5.8 to 6.2 (%). %).

On the other hand, in the conventional example, the toner density inside the developing device is 6.0 at the toner density sensor position.
(%), The toner density at the supply position is 6.0 (%) at a printing rate of 0 to 10%, the toner density at the supply position is 6.3 (%) at the printing rate of 11 to 40%, and the printing rate is 41 to 70%, the toner density at the supply position is 6.8 (%), and the printing rate is 71% to
Thus, the toner density at the supply position is 6.8 (%).

A comparison between the present embodiment and the conventional example shows that the present embodiment does not cause the detection deviation of the toner density irrespective of the printing rate. In the conventional example, however, the higher the printing rate, the higher the toner density. Detection deviation is large.

According to the image forming apparatus of the third embodiment, the detection result of the toner density by the toner density sensor 51 is not affected by the sudden change in the toner density when the collected developer flows around. Therefore, since it is possible to suppress excessive toner replenishment, it is possible to suppress problems such as an increase in image density and fogging and toner scattering.
A developer having a stable toner concentration can always be supplied to the developing roller regardless of the printing ratio.

Therefore, according to the image forming apparatus of the third embodiment, the developer having a stable toner concentration can always be supplied to the developing roller by the toner supply control according to the printing rate.

Next, a fourth embodiment of the present invention will be described. The image forming apparatus according to the fourth embodiment is different from the third embodiment in that the operation of the supply control unit 52 and the table data stored in the table storage unit 54 are different from those of the third embodiment.
Other points are the same as those of the third embodiment described with reference to FIGS. Therefore, the fourth embodiment will be described with reference to FIGS.

In the fourth embodiment, the value of the output voltage of the toner density sensor 51 can be shifted according to the control voltage. That is, even if the toner densities are the same, a sensor having such characteristics that the output voltage shifts high when the control voltage applied to the toner density sensor 51 is high and the output voltage shifts low when the control voltage is low is used. The output voltage thus shifted is an example of the judgment factor of the present invention.

The supply controller 52 controls the execution of toner supply according to the output voltage of the toner density sensor 51 with a fixed threshold value. The replenishment control unit 52 includes the toner density sensor 5
It is possible to apply a control voltage to 1 and shift the output voltage of the toner density sensor 51 by an arbitrary shift amount. The supply control unit 52 serves as an example of the shift means of the present invention and an example of the supply control means of the present invention.

In the fourth embodiment, the table storage unit 5
Reference numeral 4 stores table data relating to the control voltage corresponding to the printing rate. Table 5 is an example of table data relating to the control voltage.

[0131]

[Table 5]

In Table 5, the printing ratio has already been described in Table 1, and the control voltage indicates the value of the control voltage applied to the toner density sensor 51.

The supply control section 52 can change the control voltage according to the printing rate obtained from the printing rate determining section 53 by referring to the table data in the table storage section 54. When the value falls below the threshold value, a toner supply signal is issued. That is, the replenishment control unit 52 determines whether or not toner replenishment is necessary based on the threshold, and issues a toner replenishment signal when it is determined necessary.

For example, when the printing rate of a page on which image formation is to be performed is 11 to 40%, the replenishment control unit 52 that has obtained the printing rate from the printing rate determination unit 53 refers to the table data in the table storage unit 54. The control voltage is set to 6.5V. When the output voltage of the toner density sensor 51 falls below a threshold value (fixed), for example, during execution of image formation, the supply control unit 52 issues a toner supply signal, and the toner supply unit 5 replenishes the developing device 4b with new toner. .

As described above, the toner density sensor 5
Reference numeral 1 denotes a characteristic in which the output voltage shifts so as to increase as the control voltage increases. When the control voltage is increased, toner replenishment control is performed to increase the toner density. Conversely, when the control voltage is decreased, the toner replenishment control is performed. This is toner supply control for reducing the density.

In this embodiment, when the developer in the developer collection chamber 403 joins the developer supply chamber 401, if the toner concentration of the developer in the developer collection chamber 403 is low, the developer is temporarily joined. The developer concentration at the position P1 is greatly reduced. This is a state in which the toner concentration at the junction P1 is locally lower than the toner concentration of the entire developer circulating in the developing device 4b. When the printing rate is high, the toner density of the collected developer becomes low. Therefore, in the present embodiment, the control voltage is changed according to the printing rate by referring to the table data, and the locally generated toner density is changed. The toner supply is not executed in the case of the decrease.

Table 6 shows the toner density inside the developing device 4b in the case where the threshold value of the toner supply control is changed according to the printing rate as described above.

[0138]

[Table 6]

In Table 6, the printing rate (%) and the toner density (%) are shown.
Are the same parameters as in Table 1 and will not be described.

In addition, the actual measurement points of the toner concentration are at two positions, that is, the position of the toner concentration sensor and the supply position. As shown in FIG. 4, the position of the toner concentration sensor is slightly downstream of the position where the developer circulating from the developer collection chamber 403 joins the developer supply chamber 401. The supply position is an upstream portion of the developer supply chamber 401 in the transport direction, but this point can be treated as a representative value of the entire image area d.

As shown in Table 6, in this embodiment, when the toner density inside the developing device 4b is 6.0 (%) at the toner density sensor position, the printing rate is 0 to 10% at the supply position. The toner density is 6.0 (%) and the printing ratio is 11 to 4.
At 0%, the toner concentration at the supply position is 5.8 to 6.2.
(%), The toner density at the supply position at a print rate of 41 to 70% is 5.8 to 6.2 (%), and the toner density at the supply position at a print rate of 71% to 5.8 to 6.2 (%). %).

On the other hand, in the conventional example, the toner density inside the developing device is 6.0 at the toner density sensor position.
(%), The toner density at the supply position is 6.0 (%) at a printing rate of 0 to 10%, the toner density at the supply position is 6.3 (%) at the printing rate of 11 to 40%, and the printing rate is 41 to 70%, the toner density at the supply position is 6.8 (%), and the printing rate is 71% to
Thus, the toner density at the supply position is 6.8 (%).

When the present embodiment is compared with the conventional example, the present embodiment does not cause the detection deviation of the toner density irrespective of the printing rate, but in the conventional example, as the printing rate increases, the toner density increases. Detection deviation is large.

According to the image forming apparatus of the fourth embodiment, the detection result of the toner density by the toner density sensor 51 is not affected by the sudden change in the toner density when the collected developer flows around. Therefore, since excessive toner replenishment can be suppressed, problems such as an increase in image density, fogging and toner scattering can be suppressed.

Therefore, according to the image forming apparatus of the fourth embodiment, it is possible to always supply the developer having a stable toner concentration to the developing roller by controlling the toner supply according to the printing rate.

The image forming apparatus according to the fourth embodiment is an example in which the output voltage of the toner density sensor 51 is shifted and the threshold value is fixed, but both the output voltage of the toner density sensor 51 and the threshold value are fixed. The replenishment control unit 52 calculates a numerical value equivalent to the case where the output signal obtained by A / D converting the output voltage is subjected to software processing and shifted.
The supply control unit 52 may be configured to compare the calculated value with the threshold.

That is, the replenishment control unit 52, which is an example of the shift means, may be configured to shift the voltage value itself of the output signal output from the toner density sensor 51, or the software may be used without shifting the voltage value itself. A configuration in which the shift is performed by adding an added value to the output signal in the processing may be employed.

In the above embodiments, one system of control blocks has been described. However, in the image forming apparatus of each embodiment, the developing devices 4, 4a, and 4b for four colors are actually used.
It is equipped with four control blocks for convenience.
The operation of toner supply to each of the developing devices 4, 4a, 4b is executed independently for each color.

[0149]

According to the image forming apparatus of the first aspect, even if the diameter of the supply / conveyer auger is reduced, the developer conveyance force is ensured, and the amount of the entire developer in the developing device is sufficiently increased. It was decided to secure. In addition, the detection deviation of the toner density, which tends to occur at a high printing rate, is also improved, so that it is possible to suppress fog, toner scattering, and an abnormal increase in the image density due to the increase in the toner density.

According to the image forming apparatus of the second aspect,
The developer having a stable toner concentration was always supplied to the developing roller irrespective of the printing ratio.

According to the image forming apparatus of the seventh aspect,
By the toner supply control according to the printing rate, it has become possible to always supply the developer having a stable toner concentration to the developing roller.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a color copying machine.

FIG. 2 is a central sectional view of the developing device.

FIG. 3 is a schematic view of the developing device as viewed from above.

FIG. 4 is a rear view schematically showing the developing device.

FIG. 5 is a rear view schematically showing the developing device.

FIG. 6 is a rear view schematically showing the developing device.

FIG. 7 is a control block diagram of toner supply control.

[Explanation of symbols]

 4, 4a, 4b Developing device 5 Toner replenishing unit 41 Developing roller 43 First supply transport auger 44 Second supply transport auger 45 Stirring auger 46 Recovery auger 401 Developer supply chamber 402 Developer stirring chamber 403 Developer recovery chamber 406 First Opening 411 Bypass path 50 Control unit 51 Toner density sensor 52 Supply control unit 53 Print ratio determination unit 54 Table storage unit P1 Merging position d Image area

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Kazutoshi Kobayashi Konica Corporation, 2970 Ishikawa-cho, Hachioji-shi, Tokyo (72) Inventor Motofumi Motoki 2970, Ishikawa-cho, Hachioji-shi, Tokyo F-term ( Reference) 2H027 DB01 DD07 DE07 DE10 EA06 EC06 EC09 2H077 AA37 AB02 AB14 AB15 AB18 AC02 AC16 AD06 AD32 CA19 DA08 DA10 DA42 DA54 DA80 DB02 DB14 DB22 EA03

Claims (13)

[Claims] A developer is carried on a surface of a developing roller that is driven to rotate, and the developer is supplied to an electrostatic latent image on an image carrier for development, and the developer remains on the surface of the developing roller after development. An image forming apparatus for stripping and collecting a developer, wherein a supply conveyance auger for conveying the developer in the axial direction and supplying the developer to the developing roller, and conveying the developer in a direction opposite to the conveyance direction of the supply conveyance auger. A stirring auger for supplying the stirred and agitated developer to the supply / conveyor auger; and a collection auger for collecting the stripped developer above the stirring auger and conveying the developer in an axial direction to outside the image area. A first conveyance path for returning the developer conveyed to the downstream end of the collection auger to the outside of the image area on the downstream side of the supply auger, and agitating the developer while being conveyed to the downstream end of the collection auger. The second transport path back to the auger An image forming apparatus comprising: 2. A first developer transport member for transporting developer in an axial direction while stirring, a first transport chamber in which the first developer transport member is disposed, and the first developer. A drop port provided downstream of the transport member in the transport direction, a second developer transport member that transports the developer in the axial direction while stirring the developer, and a developer transported by the second developer transport member and the first developer transport member. The second developer conveying member is arranged so that the developer conveyed by the developer conveying member and drops from the drop port merge with each other, and the first developer is arranged at a position other than the merging position where the developer merges. A second transfer chamber separated from the transfer chamber, and a merging position where the developer merges in the second transfer chamber, or a toner concentration sensor disposed upstream of the first developer conveying member in the conveying direction from the merging position. An image forming apparatus comprising: 3. The image forming apparatus according to claim 2, wherein the developer transport directions of the first developer transport member and the second developer transport member are parallel to each other. 4. A developing roller capable of rotating and supplying a developer carried on a surface to an electrostatic latent image on an image carrier, wherein a part of the developer in the second transfer chamber is supplied to the developing roller. The image forming apparatus according to claim 2, wherein the image forming apparatus is supplied. 5. The developing device according to claim 4, wherein the second developer conveying member supplies the developing roller to the developing roller at an upstream side of the merging position in a developer conveying direction. Image forming apparatus. 6. The image forming apparatus according to claim 2, further comprising a collecting auger for collecting the developer peeled off from the surface of the developing roller in the first transfer chamber. Image forming device. 7. An image forming apparatus for developing an electrostatic latent image formed on an image carrier based on image data with a two-component developer containing toner, wherein the developer is conveyed in an axial direction while stirring. A first developer transport member, a first transport chamber in which the first developer transport member is disposed, a drop port provided downstream of the first developer transport member in the transport direction, A second developer transport member that transports in the axial direction while stirring, and a developer transported by the second developer transport member and the first developer transport member.
The second developer conveying member is arranged so that the developer conveyed by the developer conveying member and drops from the drop port merge with each other, and the first developer is arranged at a position other than the merging position where the developer merges. A second transfer chamber separated from the transfer chamber, a toner density sensor disposed downstream of the junction position in the transfer direction of the first developer transfer member, and a print rate determination for determining a print rate of the image data. A replenishment control unit that determines whether or not toner replenishment is necessary by comparing an output signal of the toner density sensor with a threshold value; a toner replenishment unit that replenishes toner according to the determination of replenishment control means; The image forming apparatus according to claim 1, wherein the determining factor is changed according to the printing rate. 8. The image forming apparatus according to claim 7, wherein the determination element is the threshold. 9. The apparatus according to claim 8, further comprising a shift unit that shifts an output signal of the toner density sensor according to the printing ratio, wherein the determination element is an output signal shifted by the shift unit. The image forming apparatus as described in the above. 10. The first developer conveying member and the second developer conveying member.
10. The image forming apparatus according to claim 7, wherein the directions of transport of the developer by the developer transport member are parallel to each other. 11. A developing roller which is rotatable and supplies a developer carried on a surface to an electrostatic latent image on an image carrier.
11. The image forming apparatus according to claim 7, wherein a part of the developer in the second transfer chamber is supplied to the developing roller. 12. The image forming apparatus according to claim 11, wherein the second developer conveying member supplies the developing roller to the developing roller at an upstream side of the merging position in the developer conveying direction. The image forming apparatus as described in the above. 13. The developing device according to claim 7, wherein the developer is collected in the first transfer chamber by a collecting unit that strips the developer remaining after development on the surface of the developing roller.
13. The image forming apparatus according to 10, 11, or 12.