JP3795596B2 - Development device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a developing device used for developing an electrostatic latent image such as electrophotography.
[0002]
[Prior art]
Some developing devices of this type use a two-component developer composed of a carrier and a toner.
In the developing container, first and second screws as first and second agitating / conveying means are disposed, and the rotation of the first and second screws causes the first and second screws to move between the first and second screws. The developer is cyclically stirred and conveyed, whereby the toner is charged and sent to the developing roller.
[0003]
By the way, in the case of color recording, compared with the conventional monochrome recording, the area ratio of the image portion is high and the toner consumption is large due to the characteristics of the image.
Therefore, it is necessary to replenish a large amount of toner and to provide an amount of charge that can be sufficiently developed.
[0004]
On the other hand, there has been a demand for downsizing and speeding up of color devices.
For speeding up, a known type is a quadruple tandem system in which photoconductors are arranged in a horizontal direction.
[0005]
In the case of this quadruple tandem system, the apparatus can be made smaller by reducing the interval between the photosensitive drums. However, in order to sufficiently mix the replenished toner with the developer, a sufficient developer capacity is required.
For this reason, in order to secure the developer capacity, means such as arranging the first and second screws up and down to increase the volume in the developing device are used.
[0006]
[Problems to be solved by the invention]
However, if the first and second screws are simply arranged above and below, the replenished toner cannot be sufficiently mixed with the carrier for charging, and there is insufficiently charged toner. However, uneven density and fog toner scattering on the image were liable to occur.
[0007]
This was particularly noticeable when a large amount of toner was replenished.
Therefore, in the developing device, even if the developer transport path cannot be sufficiently established, the replenishment toner and the developer are sufficiently mixed and charged to cause uneven image density, fogging, toner scattering, and the like. It is an object of the present invention to provide a developing device that does not generate such a problem.
[0008]
[Means for Solving the Problems]
In order to solve the above-described problems, the present invention provides a developer supplying means for supplying a developer composed of toner and a carrier to a developing portion, and a vicinity of the developer supplying means. A first agitating and conveying means for supplying the developer to the developer supplying means while agitating and conveying the developer in a first direction; and provided below the first agitating and conveying means and carried out from the first agitating and conveying means The developer that has been dropped and then stirred and transported in a second direction opposite to the first direction, and then transported upward and sent to the first stirring and transporting means. The toner is replenished to the upstream side in the developer conveying direction of the second agitating / conveying means with respect to the second agitating / conveying means and the portion of the second agitating / conveying means that receives the developer dropped from the first agitating and conveying means Toner replenishing means.
[0010]
According to a third aspect of the present invention, there is provided a developer supplying means for supplying a developer composed of toner and a carrier to the developing portion, and provided in the vicinity of the developer supplying means, and the developer is stirred and conveyed in the first direction. A first agitating / conveying means for supplying the developer to the developer supplying means, and a developer which is provided below the first agitating / conveying means and is discharged from the first agitating / conveying means. A second agitating and conveying means for agitating and conveying the developer in a second direction opposite to the first direction; and the developer conveyed by the second agitating and conveying means is conveyed upward. The developer of the second agitating / conveying means than the part for receiving the developer dropped from the first agitating / conveying means of the second agitating / conveying means and the feeding means for sending to the first agitating / conveying means Toner replenishing means for replenishing toner upstream in the conveying direction Comprising a.
[0013]
According to a fourth aspect of the present invention, a first magnet roller that supplies a developer composed of toner and a carrier to the developing portion, and provided in the vicinity of the first magnet roller, the developer is moved in the first direction. A first agitating / conveying means that supplies the first magnet roller while agitating and conveying, and a developer that is provided below the first agitating / conveying means and is discharged from the first agitating / conveying means and dropped. Receiving, the second agitating and conveying means for agitating and conveying the developer in a second direction opposite to the first direction, and the developer conveyed by the second agitating and conveying means upward. A second magnet roller that transports to the first stirring and conveying means, and a second portion of the second stirring and conveying means that receives the developer dropped from the first stirring and conveying means. Developer transport direction of agitation transport means Comprising a toner replenishing means for replenishing the toner to the flow side.
[0015]
According to the present invention, toner is replenished by the toner replenishing means to the upstream side of the portion that receives the developer dropped from the first agitating and conveying means of the second agitating and conveying means, and is dropped from the first agitating and conveying means. A heavy developer is dropped from above the light replenishment toner, thereby improving the mixing efficiency of the developer and the replenishment toner.
[0016]
Further, the toner supply means replenishes the downstream side of the developer supply means (first magnet roller) of the second agitating and conveying means with the toner replenishing means, thereby increasing the agitating and conveying distance of the replenished toner. The stirring and mixing efficiency with the developer can be improved.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
The present invention will be described below with reference to an embodiment shown in FIGS.
FIG. 2 shows the internal structure of a four-tandem color electronic copying apparatus. In the figure, reference numeral 1 denotes an apparatus main body, and an automatic document feeder 2 for automatically feeding an original is provided on a document placing table 1 a on the upper surface of the apparatus main body 1.
[0018]
A document scanner unit 5 for exposing the document is provided on the upper side in the apparatus main body 1. The scanner unit 5 includes a first carriage 6 and a second carriage 7 that are movably movable. The first carriage 6 irradiates an original with an exposure lamp 8 that irradiates light and a reflected light that is reflected from the original. The reflecting mirror 9 is provided. The second carriage 7 is provided with second and third reflecting mirrors 10 and 11 that reflect the reflected light reflected from the first reflecting mirror 9 and guide it in a predetermined direction. An optical lens 13 and a photoelectric conversion element 14 are disposed in the optical path of the reflected light reflected by the third reflecting mirror 11.
[0019]
A plurality of (four) photosensitive drums 31a to 31d as developing portions for carrying an image are rotatably disposed in a substantially central portion of the apparatus main body 1 in the sheet conveyance direction.
[0020]
Around each of the photosensitive drums 31a to 31d, a charging charger 32 for uniformly charging the drum surface sequentially along the rotation direction, a developing device 34 for developing a latent image on the drum, and a visible image on the drum. A transfer device 35 for transferring to a sheet and a cleaner 36 for removing residual toner are provided.
[0021]
Further, a laser beam scanning unit (not shown) that emits a laser beam corresponding to image information is provided in the apparatus main body 1, and the laser beam emitted from the laser beam scanning unit is respectively applied to the photosensitive drums 31a to 31d. It is guided and irradiated to form an electrostatic latent image.
[0022]
A sheet conveyance path 16 is provided in a substantially horizontal state on the lower side of the photosensitive drums 31a to 31d. A paper feed roller 21 for supplying the paper, a registration roller 22 for aligning the paper, a transfer device 35 for transferring the visible image to the paper, and the paper are conveyed in the paper conveyance path 16 in order along the paper conveyance direction. A conveying belt 27, a fixing device 18 as fixing means, a feed roller 28, and a paper discharge roller 30 are provided.
[0023]
The fixing device 18 includes a heat roller 18a and a press roller 18b that presses against the lower side of the heat roller 18a to press the paper.
A paper feed tray 24 that supplies paper is provided on one side of the apparatus main body 1, and a paper discharge tray 25 that receives paper discharged from the paper discharge roller 30 is provided on the other side.
[0024]
Thus, at the time of image formation, a document is placed on the document placing table 1a, and a copy button (not shown) is turned on.
As a result, the exposure lamp 8 is turned on, the first and second carriages 6 and 7 are traveled, and the original is scanned with light. Reflected light reflected from the original by this scanning is received by the photoelectric conversion element 14 via the first to third reflection mirrors 9 to 11 and the optical lens 13 and is subjected to photoelectric conversion. By this photoelectric conversion, laser light corresponding to the image information is emitted from the laser light scanning unit, this laser light is scanned by a polygon mirror, and this scanned laser light is applied to the photosensitive drums 31a to 31d via the optical system. Guided and irradiated. The surfaces of the photosensitive drums 31a to 31d are uniformly charged by the charging chargers 32, and electrostatic latent images of the original are formed by irradiation with laser light. The electrostatic latent images are sent to and opposed to the developing units 34 by the rotation of the photosensitive drums 31a to 31d, and a color image is formed by supplying each color toner.
[0025]
On the other hand, at this time, the sheet is supplied from the sheet feeding tray 24 by the rotation of the sheet feeding roller 21 and is aligned by the registration roller 22, and then sent between the photosensitive drums 31 a to 31 d and the transfer unit 35. The image is transferred. After this transfer, the toner remaining on the photosensitive drums 31a to 31d is scraped off and cleaned by a cleaner 36.
[0026]
The sheet on which the image has been transferred is sent to the fixing roller 18 as the conveyor belt 27 travels, and is heated and pressurized and fixed. The paper P on which the image is fixed is discharged to the paper discharge tray 25 via the discharge roller 30.
[0027]
1, 3 and 4 show the developing unit 34. FIG.
FIG. 1 is an external perspective view showing the developing device 34.
The developing device 34 includes a developing container 41, and a magnet roller 45 is provided in the developing container 41 as supply developer supplying means for supplying developer to the photosensitive drums 31 a to 31 d. The carrier to which the toner is attached adheres by magnetic force. The magnet roller 45 has a plurality of N poles and S poles arranged adjacent to each other, and a developing bias of 200 to 300 V is applied thereto.
[0028]
An upper screw portion 42 serving as a first stirring / conveying means is rotatably provided on the upper side in the developing container 41, and a lower screw portion serving as a second stirring / conveying means is provided below the upper screw portion 42. 43 is rotatably provided. The developer is circulated and conveyed while being stirred by the rotation of the upper screw portion 42 and the lower screw portion 43, and is supplied from the upper screw portion 42 to the magnet roller 45.
[0029]
As a feeding means for inserting the end portions of the upper screw portion 42 and the lower screw portion 43 into one side portion of the developing container 41 and sending the developer conveyed by the lower screw portion 43 to the upper screw portion 42. A casing 81 for accommodating the upper conveying magnet roller 55 is provided. A toner replenishment hopper 56 as a toner replenishing means for replenishing toner to the lower screw portion 43 is provided on the upper surface portion on the other end side of the developing container 41.
[0030]
FIG. 3 is a front sectional view showing the developing device 34.
In the developing container 41, a two-component developer T composed of toner and carrier is accommodated. Styrene acrylic is used as the toner particles, and the toner is negatively charged with an average particle diameter of about 10 μm. The carrier particles are 30-100 μm iron powder and are magnetic. In the developing container 41, a doctor blade 46 is provided in which the developer attached on the magnet roller 45 is a uniform developer layer.
[0031]
In a developer using a mixture of practical toner and carrier, the toner adheres as almost one particle layer on the carrier particles, and 5 to 20 carriers are developed in the development gap between the magnet roller 45 and the photosensitive drums 31a to 31d. The particles are connected by magnetic force to form brush tips. The developer at the tip of the brush tip carries toner particles to the electrostatic latent image surfaces on the photosensitive drums 31a to 31d, and development is performed.
[0032]
FIG. 4 is a side sectional view showing the developing device 34.
Between the upper screw part 42 and the lower screw part 43, a partition plate 48 is provided as a partition member for partitioning the two. One end of the partition plate 48 is opposed to one end of the lower screw 43, and the first opening 50 for dropping the developer T is disposed on the other end of the lower screw 44 on the other end. Opposing second openings 51 are provided.
[0033]
Due to the rotation of the upper screw portion 42, the toner and the carrier are supplied to the developing magnet roller 45 while being agitated and transported from one end side to the other end side. Dropped downward from the portion 50. The toner and the carrier fall to one end side of the lower screw portion 43, and are stirred and conveyed toward the other end portion by the rotation of the lower screw portion 43, and then sent to the upper side by the rotation of the conveying magnet roller 55. Then, it is sent to the upper screw part 42 through the second opening 51 and conveyed.
[0034]
Thereafter, the developer T is sequentially agitated and conveyed in the same manner and supplied to the developing magnet roller 45.
When the toner is consumed by the supply of the developer T and the toner density is lowered, the toner is supplied from the toner supply hopper 56.
[0035]
Incidentally, the supply tube 56a of the toner supply hopper 56 is inserted into the developing container 41 and extends downward. The supply pipe 56a is close to and opposed to a part upstream of the part of the lower screw part 43 that receives the developer T dropped from the first opening 50.
[0036]
When the toner is to be replenished, the developer T in which the lower screw portion 43 is dropped from the first opening portion 50 with respect to the lower screw portion 43 from the replenishment pipe 56a of the toner replenishment hopper 56 as indicated by an arrow. It is replenished to the site upstream of the site that receives it. The replenished toner is conveyed by the rotation of the lower screw portion 43, reaches the lower portion of the first opening 50, and is mixed with the developer T dropped from the first opening 50 as indicated by an arrow. The That is, a heavy developer is dropped on the light replenishing toner, mixed well, and stirred and conveyed.
[0037]
Thereafter, as described above, the developer T is circulated and conveyed between the upper screw portion 42 and the lower screw portion 43, the toner and the carrier are contacted and charged, and the developer T is moved to the magnet roller by the rotation of the upper screw portion 42. 45.
[0038]
An image characteristic test was performed using the developing device 34 configured as described above.
The test method was to output 20 sheets of continuous solid printing on A3 size continuously, then output a white image on the entire surface, and measure the fog. For the fog, the lightness of the white background was measured with a color difference meter. At this time, the toner replenishment was replenished in an amount corresponding to the developed toner amount.
[0039]
For comparison, a developing device using conventional toner replenishment (replenishing toner to the upper screw portion 42) was also evaluated at the same time.
In the conventional developing device, the fog value is 3%, which is a level with a lot of fog, whereas in the developing device according to the present invention, the fog value is 0.8%, which is a satisfactory level.
[0040]
Further, an output test of 20,000 sheets of an A4 size image with a printing rate of 5% was performed. In the developing device using the comparative conventional toner replenishing method, the contamination due to the toner scattering was noticeable around the developing device after 20,000 sheets, but in the device according to the present invention, the toner scattering was small and the contamination was extremely small.
[0041]
5 to 8 show a second embodiment of the present invention.
In addition, the same number is attached | subjected about the part same as the part shown in the above-mentioned 1st Embodiment, and the description is abbreviate | omitted.
[0042]
FIG. 5 is an external perspective view showing the developing device 34.
In this embodiment, the developer is circulated and conveyed while being stirred by the rotation of the upper screw portion 42 and the lower screw portion 43, and is supplied from the lower screw portion 43 to the magnet roller 45.
[0043]
The toner replenishment hopper 56 is provided in the opposite direction to that of the first embodiment, that is, on the casing 81 side of the upper conveying magnet roller 55.
FIG. 6 is a cross-sectional view showing the developing device 34 cut from the magnet roller 45 portion.
[0044]
The magnet roller 45 includes a cylindrical sleeve 69 having a diameter of 20 and a magnet 70 is provided in the sleeve 69. The magnet 70 has an N1 pole, an S1 pole, an N2 pole, an S2 pole, and an S3 pole and is fixed, and the sleeve 69 is rotatably provided.
[0045]
The developer T in the lower screw 43 is attracted to the developing magnet roller 45 by the magnetic force of the S2 pole, and is conveyed onto the sleeve 69 to the doctor blade 46 by the rotation of the sleeve 69. The developer on the sleeve 69 is thinned by the doctor blade 46, and development on the photosensitive drums 31a to 31d is performed at the N1 pole. The developer T on the sleeve 69 after development is peeled off at the place where the magnetic force between the S3 pole and the S2 pole is the weakest (0G) and is conveyed into the lower screw 43.
[0046]
The developer T to which the toner is sufficiently supplied by the circulation of the developer T rotates on the developing magnet roller 45, and the development of the photosensitive drums 31a to 31d is performed. FIG. 7 is a cross-sectional view showing the developing device 34 cut perpendicularly from the upper conveying magnet roller 55 portion.
[0047]
The magnet roller 55 includes a cylindrical sleeve 62 having a diameter of 20 and has a magnet 63 inside the sleeve 62. The magnet 63 has an S2 pole (400G), an S1 pole (400G), and an N2 pole (300G) and is fixed, and the sleeve 62 is rotatably provided.
[0048]
The magnet roller 55 attracts the developer from the lower screw portion 43 by magnetic force at the position of the S2 pole of the magnet 63, and conveys the developer upward by the rotation of the sleeve 62. The developer T is transported into the upper screw 42 by making the developer T free from the magnetic force of the upper transport magnet roller 55 at the position where the magnetic force between the S1 pole and the S2 pole is the weakest.
[0049]
Since the developer T is peeled from the upper and lower transport magnet rollers 55 between the S2 pole and the S1 pole, the developer T is not transported after the S1 pole, and is transported to the lower screw 43 again after one rotation. Therefore, most of the developer T attracted by the S2 pole is conveyed into the upper screw 42.
[0050]
FIG. 8 is a side sectional view showing the developing device 34.
Due to the rotation of the upper screw part 42, the toner and the carrier are stirred and conveyed from the one end side toward the other end side, and then dropped downward from the first opening 50. The toner and carrier fall to one end portion of the lower screw portion 43 and are supplied to the developing magnet roller 45 while being stirred and conveyed toward the other end portion by the rotation of the lower screw portion 43. The developer T that has not been supplied is sent to the upper side by the rotation of the carrying magnet roller 55 and is sent to the upper screw part 42 through the second opening 51. Thereafter, the developer T is sequentially and continuously agitated and conveyed in the same manner and supplied to the developing magnet roller 45.
[0051]
When the toner is consumed by the supply of the developer T and the toner density is lowered, the toner is supplied from the toner supply hopper 56.
Incidentally, the supply pipe 56 a of the toner supply hopper 56 is inserted into the casing 81 and extends downward. The supply pipe 56a is extended to a portion that reaches the upper conveying magnet roller 55 after the image area of the lower screw portion 43 ends.
[0052]
When the toner is replenished, it is replenished from the replenishment pipe 56a of the toner replenishment hopper 56 to the portion of the lower screw portion 43 that faces the upper transporting magnet roller 55 as indicated by an arrow. The replenished toner is mixed with the developer T by the rotation of the lower screw portion 43 and is sent to the upper conveying magnet roller 55. The rotation of the magnet roller 55 causes the upper screw to pass through the second opening 51. It is conveyed to the part 42.
[0053]
Thereafter, similarly, the developer T is circulated and conveyed between the upper screw portion 42 and the lower screw portion 43, the toner and the carrier are contacted and charged, and the developer T is supplied to the magnet roller 45 by the rotation of the lower screw portion 43. Is done.
[0054]
Using the developing device 34 of this embodiment, after continuous printing of 20 full-page solid images on A3 size paper, a full-color white image was output and the fog was measured. However, it was performed in a normal temperature and humidity environment. The fog was 0.8%, which was a level with no problem. Even under an environment of 30 ° C. and humidity 80%, the fog was 1%, which was a low level.
[0055]
In the developing device of the conventional method (replenishing toner to the upper screw part 42) used as a comparison, the fog was at a level that could be 1% in a room temperature and humidity environment, but in an environment of 30 ° C. and humidity 80%. The fog increased to 4% and became quite noticeable.
[0056]
In this embodiment, by supplying toner to the lower screw portion 43, it is expected that the toner agitation process path becomes longer, the agitation action at the upper conveying magnet roller 55 part works, and the chargeability of the toner is improved. Is done.
[0057]
Further, an output test of 20,000 sheets of an A4 size image with a printing rate of 5% was performed.
Compared with a developing device using a conventional toner replenishing method for comparison, contamination due to toner scattering around the developing device after 20,000 sheets was extremely small and good.
[0058]
【The invention's effect】
Since the present invention replenishes the toner by the toner replenishing means upstream of the portion of the second agitating and conveying means that receives the developer dropped from the first agitating and conveying means, the first agitating and conveying means is provided. The heavy developer dropped from the conveying means can be dropped from above the light supply toner, and the mixing efficiency of the developer and the supply toner can be improved.
[0059]
Further, since the toner is replenished by the toner replenishing means downstream of the developer supply means (first magnet roller) of the second agitating and conveying means, the agitating and conveying distance of the replenished toner is increased. Thus, the efficiency of stirring and mixing with the developer can be improved.
[0060]
Therefore, even when the volume of the developing device is reduced, the replenished toner is sufficiently mixed and charged in the developer, and the fog on the image, particularly the fog on the white background after consuming a large amount of toner such as a solid image, or the high humidity There is an effect that a good image can be obtained with very little fogging in the environment and toner scattering when outputting a large number of images.
[Brief description of the drawings]
FIG. 1 is an external perspective view showing a developing device according to a first embodiment of the present invention.
FIG. 2 is a configuration diagram showing a four-tandem color electrophotographic copying apparatus.
FIG. 3 is a front sectional view showing a developing device.
FIG. 4 is a side sectional view showing a developing device.
FIG. 5 is an external perspective view showing a developing device according to a second embodiment of the present invention.
FIG. 6 is a cross-sectional view showing the developing device cut perpendicularly from a developing magnet roller.
FIG. 7 is a cross-sectional view of the developing device cut perpendicularly from an upper conveying magnet roller.
FIG. 8 is a side sectional view showing a developing device.
[Explanation of symbols]
42 ... Upper screw part (first stirring and conveying means)
43 ... Lower screw part (second stirring and conveying means)
45... First magnet roller (developer supply means)
31a to 31d: photosensitive drum (developed portion)
35 ... developer 50 ... first opening 51 ... second opening 55 ... second magnet roller (feeding means)
56. Toner supply hopper (toner supply means)
62 ... Sleeve 63 ... Magnet 69 ... Sleeve 70 ... Magnet

Claims (4)

Developer supply means for supplying a developer comprising toner and a carrier to the developing portion;
A first agitating and conveying means provided in the vicinity of the developer supplying means and supplying the developer to the developer supplying means while agitating and conveying the developer in a first direction;
The second agitating / conveying means is provided below the first agitating / conveying means, receives the developer unloaded from the first agitating / conveying means, and drops the developer in a direction opposite to the first direction. A second agitating and conveying means that conveys upward in a direction and then sends it to the first agitating and conveying means;
A toner replenishing means for replenishing toner to the upstream side of the second agitating and conveying means in the developer conveying direction from a portion of the second agitating and conveying means that receives the developer dropped from the first agitating and conveying means;
A developing device comprising:   The toner replenishing means passes through the toner containing chamber disposed above the first agitating and conveying means, and the second conveying means through the opposite side of the first conveying means to the developer supplying means. 2. A developing device according to claim 1, further comprising a toner supply pipe communicating with said means. Developer supply means for supplying a developer comprising toner and a carrier to the developing portion;
A first agitating and conveying means provided in the vicinity of the developer supplying means and supplying the developer to the developer supplying means while agitating and conveying the developer in a first direction;
The second agitating / conveying means is provided below the first agitating / conveying means, receives the developer unloaded from the first agitating / conveying means, and drops the developer in a direction opposite to the first direction. A second agitating and conveying means for agitating and conveying in the direction;
A feeding means for conveying the developer conveyed by the second agitating and conveying means upward and sending it to the first agitating and conveying means;
A toner replenishing means for replenishing toner on the upstream side of the second agitating and conveying means in the developer conveying direction from a portion of the second agitating and conveying means that receives the developer dropped from the first agitating and conveying means;
A developing device comprising: A first magnet roller for supplying a developer composed of toner and a carrier to the developing portion;
A first agitating and conveying means provided in the vicinity of the first magnet roller and supplying the developer to the first magnet roller while agitating and conveying the developer in a first direction;
The second agitating / conveying means is provided below the first agitating / conveying means, receives the developer unloaded from the first agitating / conveying means, and drops the developer in a direction opposite to the first direction. A second agitating and conveying means for agitating and conveying in the direction;
A second magnet roller for conveying the developer conveyed by the second agitating / conveying means upward and sending the developer to the first agitating / conveying means;
A toner replenishing means for replenishing toner on the upstream side of the second agitating and conveying means in the developer conveying direction from a portion of the second agitating and conveying means that receives the developer dropped from the first agitating and conveying means;
A developing device comprising:

Images