JPH11167260A - Developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain uniform image density, to eliminate irregularities in an image, to stabilize the density and to improve the display definition, even in an image having a high printing ratio by thoroughly stirring two-component developer and thereafter supplying the developer to a developing roller in a circulating state. SOLUTION: The device is provided with a 3rd carrying path 30 for joining the excessive developer from a 1st carrying path 27 and recovered developer from a 2nd carrying path 28 and for stirring/carrying the developer, and thereafter supplying the developer to the 1st carrying path 27 in the circulating state. Thus, the toner concentration in the stirred developer to be supplied to the 1st carrying path 27 is made more uniform, then, the image density is kept constant and the high definition image free from irregularities can be obtained even in the image having the high printing ratio.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a developing device mounted on an image forming apparatus such as a printer or an electrophotographic apparatus.

[0002]

2. Description of the Related Art In recent years, laser printers having a high recording density,
With the practical use of facsimile machines, digital copiers, full-color digital copiers, laser printers, and the like, there is a demand for stabilization of the display quality of images with a large print area, such as graphics, and a high printing rate.

For this reason, the developing device realizes a uniform and sufficient supply of toner even for an image with a high printing rate in which a large amount of toner is consumed, and has excellent reproducibility of a solid image or continuous tone, and Because it does not contain magnetic material, it can respond to small particle size and is also suitable for colorization, so magnetic brush development that forms and develops a magnetic brush with a so-called two-component developer consisting of toner and carrier The device is heavily used.

[0004] Among such magnetic brush developing devices using a two-component developer, the magnetic brush developing device is excellent in agitating the developer even for an image with a high printing rate, and has a plurality of developing devices mounted in parallel in the horizontal direction. In response to a demand for downsizing a full-color developing device such as a quadruple tandem system in the horizontal direction, a conventional Japanese Patent Application Laid-Open No.
As disclosed in Japanese Patent Application Laid-Open No. 991, two mixing augers whose transport directions are opposite to each other are arranged on an upper transport path and a lower transport path of a casing having two transport paths above and below, and the developer is stirred in the casing. A vertical developing device that circulates vertically while developing has been developed.

That is, as shown in FIGS. 7 and 8, this vertical developing device is provided with a toner supply / conveyance path 2a in the upper part of the housing 1 and a toner recovery path 2b in the lower part. , The two-component developer 6 is circulated in the directions indicated by the arrows o and p while stirring the two-component developer 6 in the conveying paths 2a and 2b . While the two-component developer 6 is circulated while being stirred, the two-component developer 6 is supplied to the developing roller 7 through the upper toner supply conveyance path 2a to develop the photoreceptor 8, and after the development , Lower toner recovery transport path 2
The developer 6 is collected from the developing roller 7 at b.

[0006]

However, in such a vertical developing device, even if the stirring is performed by the mixing augers while circulating between the upper and lower conveying paths,
For an image with a high printing ratio, there is still a problem that the toner density is partially non-uniform or the density is reduced.

That is, in the conventional developing device, sufficient replenishment of the replenishment toner and the two-component developer 6 is ensured, and the amount corresponding to the toner consumed during development is reduced so as not to affect the density of the developed image. Replenishing section 1a for replenishing toner
As shown in FIG. 8, in the upper toner supply path 2a, the surplus developer and the replenishment toner that are provided near the end of the developing roller 7 and that are not supplied to the developing roller 7 are:
The toner collection conveyance path 2b at the lower part is merged from the collection port 1b.
And is sufficiently stirred by the mixing auger 4.

However, in the toner collecting and conveying path 2b, not only the developer which receives the toner supply and is dropped and supplied from the collecting port 1b and is stirred, but also the developer which does not receive the toner collected from the developing roller 7 is collected. Have been joined. Thus, the developer supplied with toner and the developer not received are combined, and the supply port 1c is not sufficiently stirred.
When the toner is circulated from the toner supply conveyance path 2a to the toner supply conveyance path 2a, especially in the case of an image with a high printing rate in which a large amount of toner is consumed, the delay of the toner supply from the toner supply section 1a has a great effect. The toner density of the component developer decreases, and the image density decreases.In addition, the developer supplied with the toner and the developer not received are not sufficiently agitated. Had been lowered.

Further, since the developer supplied with the toner and the developer not received are merged and pass near the supply port 1c of the toner collecting and conveying path 2b where the density sensor 10 is provided, the detection output of the density sensor 10 is obtained. Of the image density is large, as a result, the detection accuracy of the toner density is poor, good density control cannot be obtained, and the density of the image varies, which also deteriorates the display quality.

In view of the above, the present invention has been made in order to solve the above-mentioned problems. In a vertical developing device in which a two-component developer is circulated in an upper and lower conveying path, an image carrier always has a sufficient toner density and a uniform toner density. By providing a two-component developer that does not vary, it provides a developing device that can obtain a high-quality image with a constant image density and no density unevenness even for images with a high printing rate that consumes a large amount of toner. The purpose is to do.

[0011]

According to the present invention, as a first means for solving the above-mentioned problems, a housing for accommodating a two-component developer composed of a toner and a carrier, and the two-component developer in the housing are provided. A developing unit that magnetically conveys the developer and applies the toner to the electrostatic latent image holding unit, and is provided at a position in the housing where the two-component developer is supplied to the developing unit,
The two-component developer is placed in the first direction along the axial direction of the developing means.
And a first transport path having a first developer transport means for supplying the two-component developer to the developing means while stirring and transporting the developer in the direction of, and provided in the housing in parallel with the first transport path. A second developer transporting means for recovering the two-component developer after the development from the developing means and stirring and transporting the recovered developer in the same direction as the first direction; Path, and the developer is provided in parallel with the first transport path, and the excess developer after being supplied to the developing unit is supplied from the first transport path, and the recovered developer is supplied from the second transport path. And a third developer conveying means for stirring and conveying the supplied surplus developer and the recovered developer in a second direction opposite to the first direction, wherein the surplus developer and the recovered developer are provided. Circulates the agitated developer formed by agitating the developer through the first transport path Kyusuru in which the third provided a conveying path.

Further, the present invention provides a second invention for solving the above problems.
Means for housing a two-component developer comprising a toner and a carrier, and a developing means for magnetically transporting the two-component developer in the housing and applying the toner to an electrostatic latent image holding means Wherein the two-component developer is provided in the housing at a position for supplying the two-component developer to the developing means, and the two-component developer is stirred and conveyed in a first direction along an axial direction of the developing means, and the developing is performed. A first transport path having a first developer transport means for supplying the two-component developer to the means, and a first transport path provided in the housing in parallel with the first transport path; A second transport path having second developer transport means for recovering the two-component developer and agitating and transporting the recovered developer in the same direction as the first direction; and the first transport path. Is provided in parallel with the front end at the front end side in the first direction. Wherein the opposite end of the first recovery port with the first recovery port and the second recovery port electrically connected to the second transport path to conduct the first transport path are formed first
A supply port is formed to be electrically connected to the first conveyance path. The surplus developer after being supplied to the developing unit supplied from the first conveyance path through the first recovery port and the second conveyance path from the second conveyance path. 2
And the recovered developer supplied through the recovery port of the first type.
A third developer conveying unit that stirs and conveys the excess developer and the recovered developer through the supply port through the first port. And a third transport path for circulating the supply to the transport path.

Further, the present invention provides a third aspect for solving the above problems.
Means for housing a two-component developer comprising a toner and a carrier, and a developing means for magnetically transporting the two-component developer in the housing and applying the toner to an electrostatic latent image holding means Wherein the two-component developer is provided in the housing at a position for supplying the two-component developer to the developing means, and the two-component developer is stirred and conveyed in a first direction along an axial direction of the developing means, and the developing is performed. A first conveying path having a first developer conveying means for supplying the two-component developer to the means, and a first conveying path which is electrically connected to the first conveying path at a front end side in the first direction. A toner replenishing means for replenishing new toner, and a two-component developer after development is provided from the developing means in parallel with the first transport path in the housing, and the recovered and developed The agent is stirred and transported in the same direction as the first direction. A second transport path having a second developer transport means, and a second transport path provided in parallel with the first transport path, and the surplus developer after being supplied to the developing means from the first transport path is supplied to the developing means. A third developer transport unit that is supplied with the recovered developer from a second transport path and agitates and transports the supplied surplus developer and the recovered developer in a second direction opposite to the first direction; And a third transport path for circulating and supplying the agitated developer formed by agitating the surplus developer and the recovered developer to the first transport path.

Further, the present invention provides a fourth invention for solving the above problems.
Means for housing a two-component developer comprising a toner and a carrier, and a developing means for magnetically transporting the two-component developer in the housing and applying the toner to an electrostatic latent image holding means Wherein the two-component developer is provided in the housing at a position for supplying the two-component developer to the developing means, and the two-component developer is stirred and conveyed in a first direction along an axial direction of the developing means, and A first conveying path having a first developer conveying means for supplying the two-component developer to the means, and a first conveying path which is electrically connected to the first conveying path at a front end side in the first direction. A toner replenishing means for replenishing new toner, and a two-component developer after development is provided from the developing means in parallel with the first transport path in the housing, and the recovered and developed The agent is stirred and transported in the same direction as the first direction. A second conveyance path having a second developer conveyance means, and a first recovery provided parallel to the first conveyance path and connected to the first conveyance path at a front end side in the first direction. A second collection port communicating with the second conveyance path is formed, and a supply port communicating with the first conveyance path is formed at an end opposite to the first collection port, and the second collection port is formed. A surplus developer supplied to the developing unit supplied from the first transport path through the first recovery port and the recovered developer supplied through the second recovery port from the second transport path to the developing means; Has a third developer conveying means for stirring and conveying the developer in the second direction opposite to the first direction, and agitating the excess developer and the recovered developer through the supply port. A third transport path for circulating the first transport path.

Further, the present invention provides a fifth aspect for solving the above problems.
Means for housing a two-component developer comprising a toner and a carrier, and a developing means for magnetically transporting the two-component developer in the housing and applying the toner to an electrostatic latent image holding means Wherein the two-component developer is provided in the housing at a position for supplying the two-component developer to the developing means, and the two-component developer is stirred and conveyed in a first direction along an axial direction of the developing means, and the developing is performed. A first transporting path having a first developer transporting means for supplying the two-component developer to the means, and a toner replenishing unit which conducts to the first transporting path and replenishes the first transporting path with new toner. Means and the first
A second developer transport that is provided in parallel with the transport path and collects the two-component developer after the development is completed from the developing unit and agitates and transports the recovered developer in the same direction as the first direction. A second transport path having a unit, and a second transport path which is provided in parallel with the first transport path, and is supplied with surplus developer after being supplied from the first transport path to the developing means, and the second transport path. And a third developer transport unit that agitates and transports the supplied surplus developer and the recovered developer in a second direction opposite to the first direction. A third transport path for circulating and supplying the agitated developer formed by agitating the surplus developer and the collected developer to the first transport path, and a third transport path at a front end side in the second direction. Density detecting means for detecting the toner density of the It is intended to provide a control means for controlling the toner supply means in response to.

Further, the present invention provides a sixth aspect for solving the above problems.
Means for housing a two-component developer comprising a toner and a carrier, and a developing means for magnetically transporting the two-component developer in the housing and applying the toner to an electrostatic latent image holding means Wherein the two-component developer is provided in the housing at a position for supplying the two-component developer to the developing means, and the two-component developer is stirred and conveyed in a first direction along an axial direction of the developing means, and the developing is performed. A first conveyance path having a first developer conveyance means for supplying the two-component developer to the means, and a toner which is connected to the first conveyance path and supplies new toner to the first conveyance path. Replenishing means, provided in the housing in parallel with the first transport path, for recovering the two-component developer after the completion of development from the developing means, and for collecting the recovered developer in the first direction. The second to stir and transport in the same direction
And a first recovery port provided in parallel with the first transport path and connected to the first transport path at a front end side in the first direction. And the second
A second recovery port is formed to communicate with the first transport path, and a supply port is formed at the opposite end of the first recovery port to communicate with the first transport path. The first
The surplus developer after being supplied to the developing means supplied through the recovery port and the recovered developer supplied through the second recovery port from the second transport path are opposite to the first direction. A third developer conveying unit that stirs and conveys the surplus developer and the recovered developer from the supply port to the first conveying path. A third conveying path for supplying, a density detecting means for detecting a toner density in the third conveying path at a front end side in the second direction, and the toner replenishing means in accordance with a detection result by the density detecting means And control means for controlling the

Further, the present invention provides a seventh aspect for solving the above problems.
Means for housing a two-component developer comprising a toner and a carrier, and a developing means for magnetically transporting the two-component developer in the housing and applying the toner to an electrostatic latent image holding means Wherein the two-component developer is provided in the housing at a position for supplying the two-component developer to the developing means, and the two-component developer is stirred and conveyed in a first direction along an axial direction of the developing means, and the developing is performed. A first conveying path having a first developer conveying means for supplying the two-component developer to the means, and a first conveying path which is electrically connected to the first conveying path at a front end side in the first direction. A toner replenishing means for replenishing new toner, and a two-component developer after development is provided from the developing means in parallel with the first transport path in the housing, and the recovered and developed The agent is stirred and transported in the same direction as the first direction. A second transport path having a second developer transport means, and a second transport path provided in parallel with the first transport path, and the surplus developer after being supplied to the developing means from the first transport path is supplied to the developing means. A third developer transport unit that is supplied with the recovered developer from a second transport path and agitates and transports the supplied surplus developer and the recovered developer in a second direction opposite to the first direction; A third transport path for circulating and supplying the agitated developer obtained by agitating the surplus developer and the recovered developer to the first transport path, and the third transport path at the front end side in the second direction. And a control means for controlling the toner replenishing means in accordance with the detection result by the density detecting means.

Further, the present invention provides an eighth aspect for solving the above problems.
Means for housing a two-component developer comprising a toner and a carrier, and a developing means for magnetically transporting the two-component developer in the housing and applying the toner to an electrostatic latent image holding means Wherein the two-component developer is provided in the housing at a position for supplying the two-component developer to the developing means, and the two-component developer is stirred and conveyed in a first direction along an axial direction of the developing means, and the developing is performed. A first conveying path having a first developer conveying means for supplying the two-component developer to the means, and a first conveying path which is electrically connected to the first conveying path at a front end side in the first direction. A toner replenishing means for replenishing new toner, and a two-component developer after development is provided from the developing means in parallel with the first transport path in the housing, and the recovered and developed The agent is stirred and transported in the same direction as the first direction. A second conveyance path having a second developer conveyance means, and a first recovery provided parallel to the first conveyance path and connected to the first conveyance path at a front end side in the first direction. A second collection port communicating with the second conveyance path is formed, and a supply port communicating with the first conveyance path is formed at an end opposite to the first collection port, and the second collection port is formed. A surplus developer supplied to the developing unit supplied from the first transport path through the first recovery port and the recovered developer supplied through the second recovery port from the second transport path to the developing means; Has a third developer conveying means for stirring and conveying the developer in the second direction opposite to the first direction, and agitating the excess developer and the recovered developer through the supply port. A third conveyance path that circulates and supplies the first conveyance path, and a third conveyance path inside the third conveyance path at the front end side in the second direction. And density detecting means for detecting the toner concentration, is intended to provide a control means for controlling the toner supply means in response to the detection result by the density detecting means.

According to the present invention, according to the present invention, the surplus developer supplied from the first transport path and the recovered developer supplied from the second transport path are combined and then sufficiently stirred and transported to the first transport path. By providing a third transport path for circulating supply,
Improves the agitating property of the two-component developer supplied to the conveying path of
The purpose of the present invention is to make the toner density uniform and to improve the display quality without causing image density unevenness even in an image with a high printing rate. Further, since the density sensor can detect the concentration of the agitated developer obtained by sufficiently agitating the surplus developer that has been supplied with toner and the collected developer that has not received the toner, the density detection result does not greatly change. Since the density detection accuracy can be improved and good density control can be obtained, variations in image density are prevented and display quality is improved.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to a first embodiment shown in FIGS. Reference numeral 16 denotes a developing device incorporated in an image forming apparatus such as a laser printer (not shown) for a digital copier, and circulates a two-component developer 20 including a toner and a carrier in a housing 17 in a vertical direction. And supply it to a developing roller 18 as a developing means.
The photosensitive drum 21 serving as an electrostatic latent image holding unit is developed.

The photosensitive drum 21 is made of an organic photoconductor 21b on an aluminum (Al) drum 21a having a diameter of 60 mm.
Is provided. The developing roller 18 has a developing sleeve 18a made of aluminum (Al) having an outer diameter of 28 mm and provided with irregularities having a surface roughness of about 20 μm by sandblasting, with a gap of 0.5 mm with respect to the photosensitive drum 21. A fixed magnet roller is provided on the inner periphery of the developing sleeve 18a, and a developing pole N1 of 950 gauss and a developer regulating pole S2,6 of 500 gauss are provided.
A magnet roller 18b having a developer supply pole N2 of 00 gauss, a developer stripping pole S3 of 600 gauss, and a developer collection pole S4 of 800 gauss is fixed. Reference numeral 22 denotes a developer regulating blade made of stainless steel, which is attached to the housing 17 with a gap of 0.45 mm to the developing sleeve 18a and regulates the thickness of the magnetic brush 19 formed around the developing roller 18. .

In the housing 17, first to third members provided in parallel with the developing roller 18 and each serving as developer stirring means are provided.
First to third transport paths 2 having first and second augers 23, 24, and 26, and partitioned by first and second partition walls 31, 32.
7, 28, 30 are formed. One end of the first partition wall 31 is connected to the first transport path 27 and the third transport path 30, and the excess developer 27 a that is not applied to the developing roller 18 of the first transport path 27 is removed by the third transport path. A first recovery port 31a that drops and supplies the developer to the transport path 30 is formed. At the other end of the first partition wall 31, the agitated developer 30a that has been agitated and transported in the third transport path 30 is supplied to the first transport path. 27, a supply port 31b for circulating supply by overflow is formed.

A second transport path 28 and a third transport path 30 are electrically connected to one end of the second partition 32 so that the collected developer 28a in the second transport path 28 is transferred to the third transport path. 30 is provided with a second recovery port 32a to be supplied by overflow.

First to third augers 23, 24, 26
Is formed by spirally winding metal plates 23b, 24b, 26b around 8 mmφ metal shafts 23a, 24a, 26a, and the diameter of the first and third augers 23, 26 is 23 m.
m, the pitch is 34 mm, the diameter of the second auger 24 is 18 mm, and the pitch is 27 mm. Also, the second
At the end of the auger 24 on the side of the second recovery port 32a, a folded wing 24c for facilitating the transfer of the recovered developer 28a to the third transport path 30 in the reverse direction is provided. At the end on the supply port 31b side, there is provided a folded blade 26c for facilitating the transfer of the agitated developer 30a to the first transport path 27 in the reverse direction.

As shown in FIG. 2 in the housing 17, in the first transport path 27, the surplus developer 27a is moved in the first direction by the rotation of the first auger 23 in the direction of arrow q. The sheet is conveyed in a certain arrow r direction, dropped and supplied to the third conveyance path 30 through the first collection port 31a, and is supplied to the second conveyance path 2
In FIG. 8, the recovered developer 28a is transported in the arrow r direction which is the first direction by the rotation of the second auger 24 in the direction of arrow t, and is supplied to the third transport path 30 through the second recovery port 32a. Is done. In the third transport path 30, the third auger 2
6 in the direction of arrow u, the excess developer 2
7a and the recovered developer 28a are moved in the second direction indicated by an arrow v.
The developer 30a is stirred and transported in the direction
A developer circulation path 34 for circulating and supplying the first conveyance path 27 to the first conveyance path 27 by overflow is formed.

The reference numeral 17a designates a new toner supply from a toner replenishing machine (not shown) to the first conveying path 27 in the vicinity of the first recovery port 31a in accordance with the amount of toner consumed during development. Reference numeral 36 denotes a density sensor that detects the toner density of the agitated developer 30a in the third conveyance path 30 near the supply port 31b. The density sensor 36 detects a toner density by detecting a change in magnetic permeability in the agitated developer 30a. The density sensor 36 is connected to a control device (not shown) of the image forming apparatus, and the control device (not shown) supplies an excess developer 27a having an optimum toner density to the developing roller 18 according to a detection result by the density sensor 36. A toner supply unit (not shown) is controlled to control the amount of toner supplied to the toner supply port 17a so that the toner can be supplied.

Next, the operation will be described. With the start of the image forming process of the image forming apparatus, in the developing device 16, the developing sleeve 18a of the developing roller 18 rotates in the direction of the arrow x, and the first to third augers 23, 24, and 26 also move the arrows q, Rotate in the t and u directions. Thereby, the developing roller 18 is supplied with the agitated developer 30a supplied from the supply port 31b to the first transport path 27 at the developer supply pole N2,
Magnetic Field by Magnet Roller 18b and Developing Sleeve 18
A magnetic brush 18c is formed on the developing sleeve 18a while the height is regulated by the developer regulating blade 22 by the rotation of the a, and the static electricity is formed on the photosensitive drum 21 through the image forming process at the developing pole N1. Develop the latent image. Thereafter, the developing sleeve 18a is rotated and the surplus developer 27a, which has been developed at the developer collecting pole S4, is dropped and collected on the second transport path 28. At the developer supply pole N2, the developer is used for the next development.
A new stirring developer 30a is supplied.

On the other hand, in the first transport path 27,
By rotating the auger 23, the surplus developer 27a of the agitated developer 30a not supplied to the developing roller 18 is supplied to the developing roller 18 while being agitated and conveyed in the direction of arrow r.
Further, the surplus developer 27a not contributing to the development is dropped and supplied from the first recovery port 31a to the third transport path 30. During this time, toner is replenished to the toner replenishing port 17a by a toner replenishing machine controlled by a control device (not shown) in accordance with the detection result from the density sensor 36. The toner is supplied from the first recovery port 31a to the third transport path 30 so as to maintain an optimum toner density according to the image density.

Further, in the second transport path 28, the recovered developer 28a dropped and recovered from the developer recovery pole S4 by the rotation of the second auger 24 is stirred and transported in the direction of the arrow r while the second developer 28a is being transported. It is supplied from the recovery port 32a to the third transport path 30 by overflow by the folded blade 24c.

In the third transport path 30, the first recovery port 31a
And the excess developer 2 which is merged from the second collection port 32a.
7a and the recovered developer 28a are sufficiently agitated and conveyed in the direction of arrow v by the rotation of the third auger 26, and at the position of the supply port 31b, the agitated developer 30a is used for new development while overflowing with the return blade 26d. It is circulated and supplied to the upper first transport path 27. The density sensor 36 is connected to the supply port 31.
The toner concentration of the agitated developer 30a passing through the conveyance path 30 near b is detected, and the detection result is input to a control device (not shown).

Next, a development test in which the developing device 16 is mounted on a digital copying machine ED-2460 (manufactured by Toshiba Corporation) will be described. The digital copying machine used in the development test has a peripheral speed of the photosensitive drum 21 of 127 mm / sec, a printing speed of 22 sheets / min (paper size: A4 landscape), and a recording density of 6
00 dpi (dot / inch, 1 dot is about 43μ)
m). The potential condition of the photosensitive drum 21 at the developing position is a charging potential of −600 V and a post-exposure potential of −50 V, and development is performed by a reversal developing method in which toner is adhered to an exposed portion and developed.

The driving conditions of the developing device 16 are as follows: the peripheral speed of the developing sleeve 18a is 1.3 times the peripheral speed of the photosensitive drum 21, and the rotational speeds of the first to third augers 23, 24 and 26 are each 3
At 50 rpm, the developing bias applied to the developing sleeve 18a was changed to a DC voltage of -420 V, 1.6 V _PP , and a frequency of 4
It is assumed that the waveform is applied by superimposing a square wave alternating voltage of kHz.

As the two-component developer, ferrite particles having a substantially spherical shape, a saturation magnetization of 65 emu / g (at 3000 Oe), an electric resistance of 10 ⁸ Ωm, a true specific gravity of 5.0 g / cm ^{3 and} an average particle diameter of 60 μm are used as the carrier. The toner used was a black toner (manufactured by Toshiba Corporation) for the above digital copying machine ED-3850 having an average particle diameter of 9.3 μm, a negatively charged polarity and a true specific gravity of 1.1.

Then, the carrier and the toner are mixed so that the toner concentration becomes 6 wt% with respect to the amount of the developer to prepare a two-component developer.
As shown in FIG. 2 on the developing sleeve 18a after printing all the solid images continuously on 10 sheets using A3 paper. D. E
The toner concentration at the position was examined. As a result, as shown by the solid line (a) in FIG. 6, despite the rapid toner consumption, a uniform and good toner density could be maintained over the entire length of the developing sleeve 18a. Incidentally, when a similar developing test was performed using the conventional developing device described with reference to FIG. 7 and a comparison was made, as shown by a dotted line (b) in FIG. In particular, in the longitudinal direction of the developing roller 7, the toner density was remarkably reduced as the distance from the developer supply port 1b was increased, resulting in density unevenness.

Next, printing was performed on 200,000 sheets of a 25% printing rate image having a high printing rate using A4 paper continuously, and the change in toner density was examined. As a result, as shown in FIG. 8, in the conventional developing device, the detection accuracy of the density sensor is poor, and the delay of toner replenishment is greatly affected. Although it fluctuated,
In this embodiment, as shown by the solid line (a), almost no fluctuation was observed, and a good toner density was stably obtained.

With this configuration, in a vertical developing device that improves the agitating property of the two-component developer and saves space in the horizontal direction, the surplus toner supplied from the first conveying path 27 is supplied. The developer 27a and the recovered developer 28a that does not receive toner supply from the second transport path 28 are merged and sufficiently agitated and transported by the third auger 26, and then the agitated developer 30a
Transport path 30 that circulates and supplies the first to the first transport path 27 side
Is supplied to the developing roller 18 by circulating and supplying the agitated developer 30a having a uniform toner concentration in which the surplus developer 27a always supplied with toner and the recovered developer 28a not supplied with toner are sufficiently stirred and mixed. Thus, even in an image with a high printing rate in which a large amount of toner is consumed, it is possible to form an image with high display quality without density unevenness in the longitudinal direction of the developing roller 18. Further, since the stirring developer 30a is sufficiently stirred at the position of the density sensor 36, the detection result of the density by the density sensor 36 is not largely changed, so that the detection accuracy of the toner density can be improved and the toner density can be controlled well. And a good image having a stable density can be obtained.

The present invention is not limited to the above-described embodiment, but can be variously changed in design. For example, the material or particle size of the toner or carrier of the two-component developer is not limited as long as it is within a range normally used. The shape and the like are also arbitrary.

[0038]

As described above, according to the present invention, in the vertical developing device, the surplus developer not supplied to the developing means and the recovered developer recovered from the developing means after the completion of the development are merged. A third transport path is provided, and the two-component developer is sufficiently stirred in the third transport path, and then circulated and supplied to the developing device side, whereby a stable two-component developer having a uniform toner concentration is always supplied to the developing device. Even in an image having a high printing rate, which can be supplied and consumes a large amount of toner, an image having a high display quality without a density unevenness and a constant image density can be obtained. Further, the accuracy of the toner density control can be improved by improving the detection accuracy by the density detecting means, and a stable and good image with little change in the image density can be obtained, and the display quality can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a developing device according to an embodiment of the present invention as viewed from a side.

FIG. 2 is an explanatory diagram showing a circulation path of a developer in the developing device according to the embodiment of the present invention.

FIG. 3 is an explanatory diagram of a second transport path and a third transport path according to the embodiment of the present invention as viewed from the line AA ′ in FIG. 1;

FIG. 4 is an explanatory diagram of a first transport path and a third transport path according to the embodiment of the present invention as viewed from a line BB ′ in FIG. 1;

FIG. 5 is a graph showing a toner density on a developing sleeve after a continuous image is formed at a high printing rate by incorporating the developing device according to the embodiment of the present invention into a laser printer.

FIG. 6 is a graph showing a change in toner density during continuous image formation at a high printing rate when the developing device according to the embodiment of the present invention is incorporated in a laser printer.

FIG. 7 is a schematic configuration diagram of a conventional developing device viewed from a side.

FIG. 8 is an explanatory view showing a circulation path of a developer in a conventional developing device.

[Explanation of symbols]

 Reference Signs List 16 developing device 17 housing 17a toner supply port 18 developing roller 18a developing sleeve 18b magnet roller 20 two-component developer 21 photosensitive drum 23 first auger 24 second auger 26 3rd auger 27 ... 1st conveyance path 28 ... 2nd conveyance path 30 ... 3rd conveyance path 31 ... 1st partition 31a ... 1st collection port 31b ... supply port 32 ... 2nd partition 32a ... Second recovery port 34: circulation path 36: concentration sensor

Claims (8)

[Claims] 1. A housing for housing a two-component developer including a toner and a carrier, and a developing device for magnetically transporting the two-component developer in the housing and applying the toner to an electrostatic latent image holding unit. Means, provided in the housing at a position for supplying the two-component developer to the developing means, stirring and transporting the two-component developer in a first direction along an axial direction of the developing means, and A first transporting path having a first developer transporting means for supplying the two-component developer to the developing means; and a first transporting path provided in the housing in parallel with the first transporting path. A second transport path having second developer transport means for recovering the later two-component developer and agitating and transporting the recovered developer in the same direction as the first direction; and the first transport A first transporting path from the first transport path. Is supplied to the collected developer from the second conveying path is supplied excess developer after supplying to the means,
A third developer conveying unit that stirs and conveys the supplied surplus developer and the collected developer in a second direction opposite to the first direction; A third transport path for circulating and supplying the agitated developer formed by stirring to the first transport path. 2. A housing for accommodating a two-component developer including a toner and a carrier, and a developing device for magnetically transporting the two-component developer in the housing and applying the toner to an electrostatic latent image holding unit. Means, provided in the housing at a position for supplying the two-component developer to the developing means, stirring and transporting the two-component developer in a first direction along an axial direction of the developing means, and A first transporting path having a first developer transporting means for supplying the two-component developer to the developing means; and a first transporting path provided in the housing in parallel with the first transporting path. A second transport path having second developer transport means for recovering the later two-component developer and agitating and transporting the recovered developer in the same direction as the first direction; and the first transport Provided in parallel with the road, and at the front end side in the first direction. A first recovery port that communicates with the first transport path and a second recovery port that communicates with the second transport path are formed, and the first recovery port is formed at an opposite end of the first recovery port. A supply port communicating with a transport path is formed, and surplus developer after being supplied to the developing unit that is supplied from the first transport path through the first recovery port and the second developer from the second transport path. A third developer conveying means for stirring and conveying the collected developer supplied through the collecting port in a second direction opposite to the first direction, wherein the surplus developer and the collected developer are provided. And a third transport path for circulating and supplying agitated developer formed by agitating from the supply port to the first transport path. 3. A housing for accommodating a two-component developer including a toner and a carrier, and a developing device for magnetically transporting the two-component developer in the housing and applying the toner to an electrostatic latent image holding unit. Means, provided in the housing at a position for supplying the two-component developer to the developing means, stirring and transporting the two-component developer in a first direction along an axial direction of the developing means, and A first transport path having a first developer transport unit that supplies the two-component developer to the developing unit; and a first transport path that is electrically connected to the first transport path at a front end side in the first direction. A toner replenishing unit for replenishing a new toner to the path, and a two-component developer after development is provided from the developing unit, which is provided in parallel with the first conveying path in the housing, and the collected recovery Stir and transport the developer in the same direction as the first direction A second transport path having a second developer transport unit, provided in parallel with the first transport path, and supplied with excess developer after being supplied to the developing unit from the first transport path. The recovered developer is supplied from the second transport path,
A third developer conveying unit that stirs and conveys the supplied surplus developer and the collected developer in a second direction opposite to the first direction; A third transport path for circulating and supplying the agitated developer formed by stirring to the first transport path. 4. A housing for accommodating a two-component developer including a toner and a carrier, and a developing device for magnetically transporting the two-component developer in the housing and applying the toner to an electrostatic latent image holding unit. Means, provided in the housing at a position for supplying the two-component developer to the developing means, stirring and transporting the two-component developer in a first direction along an axial direction of the developing means, and A first transport path having a first developer transport unit that supplies the two-component developer to the developing unit; and a first transport path that is electrically connected to the first transport path at a front end side in the first direction. A toner replenishing unit for replenishing a new toner to the path, and a two-component developer after development is provided from the developing unit, which is provided in parallel with the first conveying path in the housing, and the collected recovery Stir and transport the developer in the same direction as the first direction A second transport path having a second developer transport unit, a first transport path provided in parallel with the first transport path, and a first conductive path connected to the first transport path at a front end side in the first direction. A collection port and a second collection port that communicates with the second conveyance path are formed, and a supply port that communicates with the first conveyance path is formed at an end opposite to the first collection port, and the supply port is formed. Surplus developer after being supplied to the developing unit supplied from the first transport path through the first recovery port and the recovered developer supplied through the second recovery port from the second transport path. And a third developer conveying means for stirring and conveying the developer in the second direction opposite to the first direction, and stirring the surplus developer and the recovered developer by the supply port. And a third transport path for circulating and supplying the first transport path to the first transport path. 5. A housing for accommodating a two-component developer comprising a toner and a carrier, and a developing device for magnetically transporting the two-component developer in the housing and applying the toner to an electrostatic latent image holding unit. Means, provided in the housing at a position for supplying the two-component developer to the developing means, stirring and transporting the two-component developer in a first direction along an axial direction of the developing means, and A first transport path having a first developer transport unit that supplies the two-component developer to the developing unit; and a toner that conducts to the first transport path and supplies new toner to the first transport path. Replenishing means, provided in the housing in parallel with the first transport path, for recovering the two-component developer after the development is completed from the developing means, and transferring the recovered developer to the first direction. The second developer conveying means for stirring and conveying in the same direction A second transport path, which is provided in parallel with the first transport path, and supplies surplus developer after being supplied to the developing unit from the first transport path, and supplies the excess developer from the second transport path. Collected developer is supplied,
A third developer conveying unit that stirs and conveys the supplied surplus developer and the collected developer in a second direction opposite to the first direction; A third conveying path for circulating and supplying the agitated developer to the first conveying path, and a density detecting unit for detecting a toner density in the third conveying path at a front end side in the second direction. And a control means for controlling the toner replenishing means in accordance with the detection result of the density detecting means. 6. A housing for accommodating a two-component developer comprising a toner and a carrier, and a developing device for magnetically transporting the two-component developer in the housing and applying the toner to an electrostatic latent image holding unit. Means, provided in the housing at a position for supplying the two-component developer to the developing means, stirring and transporting the two-component developer in a first direction along an axial direction of the developing means, and A first transport path having a first developer transport unit that supplies the two-component developer to the developing unit; and a first toner path that conducts to the first transport path and supplies new toner to the first transport path. A toner replenishing means, provided in the housing in parallel with the first transport path, for recovering the two-component developer after the completion of the development from the developing means, and transferring the recovered developer to the first direction. Second developer transporter that agitates and transports in the same direction as A second collection path having: a first collection port that is provided in parallel with the first conveyance path and that is connected to the first conveyance path at a front end portion in the first direction and the second collection path; A second recovery port that communicates with the transport path is formed, and a supply port that communicates with the first transport path is formed at an end opposite to the first recovery port, and the supply port is formed from the first transport path. The surplus developer supplied to the developing unit supplied through the first recovery port and the recovered developer supplied through the second recovery port from the second conveyance path and the developer are supplied in the first direction. A third developer conveying unit that stirs and conveys the excess developer and the recovered developer from the supply port through the first conveying path. And a toner concentration in the third conveyance path is detected at the front end side in the second direction. That the concentration detection means, a developing device, characterized in that and a control means for controlling the toner supply means in response to the detection result by the density detecting means. 7. A housing for accommodating a two-component developer including a toner and a carrier, and a developing device for magnetically transporting the two-component developer in the housing and applying the toner to an electrostatic latent image holding unit. Means, provided in the housing at a position for supplying the two-component developer to the developing means, stirring and transporting the two-component developer in a first direction along an axial direction of the developing means, and A first transport path having a first developer transport unit that supplies the two-component developer to the developing unit; and a first transport path that is electrically connected to the first transport path at a front end side in the first direction. A toner replenishing unit for replenishing a new toner to the path, and a two-component developer after development is provided from the developing unit, which is provided in parallel with the first conveying path in the housing, and the collected recovery Stir and transport the developer in the same direction as the first direction A second transport path having a second developer transport unit, provided in parallel with the first transport path, and supplied with excess developer after being supplied to the developing unit from the first transport path. The recovered developer is supplied from the second transport path,
A third developer conveying unit that stirs and conveys the supplied surplus developer and the collected developer in a second direction opposite to the first direction; A third conveying path for circulating and supplying the agitated developer to the first conveying path, and a density detecting unit for detecting a toner density in the third conveying path at a front end side in the second direction. And a control means for controlling the toner replenishing means in accordance with the detection result of the density detecting means. 8. A housing for accommodating a two-component developer including a toner and a carrier, and developing the two-component developer magnetically in the housing and applying the toner to an electrostatic latent image holding unit. Means, provided in the housing at a position for supplying the two-component developer to the developing means, stirring and transporting the two-component developer in a first direction along an axial direction of the developing means, and A first transport path having a first developer transport unit that supplies the two-component developer to the developing unit; and a first transport path that is electrically connected to the first transport path at a front end side in the first direction. A toner replenishing unit for replenishing a new toner to the path, and a two-component developer after development is provided from the developing unit, which is provided in parallel with the first conveying path in the housing, and the collected recovery Stir and transport the developer in the same direction as the first direction A second transport path having a second developer transport unit, a first transport path provided in parallel with the first transport path, and a first conductive path connected to the first transport path at a front end side in the first direction. A collection port and a second collection port that communicates with the second conveyance path are formed, and a supply port that communicates with the first conveyance path is formed at an end opposite to the first collection port, and the supply port is formed. Surplus developer after being supplied to the developing unit supplied from the first transport path through the first recovery port and the recovered developer supplied through the second recovery port from the second transport path. And a third developer conveying means for stirring and conveying the developer in the second direction opposite to the first direction, and stirring the surplus developer and the recovered developer by the supply port. And a third transport path for circulating supply from the first transport path to the first transport path, and a third transport path at a front end side in the second direction. And density detecting means for detecting the toner concentration of the developing device, characterized in that and a control means for controlling the toner supply means in response to the detection result by the density detecting means.