JP2021026213A - Developing device and image forming apparatus - Google Patents

Abstract

To provide a developing device that can satisfactorily prevent, compared with before, image density unevenness due to an insufficient amount of supplied developer or feeding of an insufficiently mixed developer to a developing area.SOLUTION: A developing device has: a developer carrier 12 that includes magnetic field generation means 12a therein, and carries a developer 10 including toner and a magnetic carrier, and conveys the developer to a developing area by rotation; a developer regulation member 13; and a developer supply conveyance path 15. The developing device further has an inhibition member 21 that ensures a supply path 20 for passing the developer in the developer supply conveyance path 15 toward the developer carrier 12 between the inhibition member and a side wall upper end 24 toward the developer carrier 12 on the developer supply conveyance path 15, and inhibits a developer whose passage is inhibited by the developer regulation member 13 from moving toward the surface of the developer carrier 12. A width W of the supply path in a direction orthogonal to the direction of the axis of rotation of the developer carrier 12 is set to 7% or more and less than 10% or less of the circumference length of the outer diameter of the developer carrier 12.SELECTED DRAWING: Figure 2

Description

The present invention relates to a developing device and an image forming device.

Conventionally, there is known a developing apparatus having a magnetic field generating means inside and having a developing agent carrier that carries a developing agent containing toner and a magnetic carrier and conveys it to a developing region by rotation.
For example, Patent Document 1 describes a developing apparatus of this type, in which a developer regulating member, a developer supply transport path, and a supply for passing the developer in the developer supply transport path to the developer carrier side are supplied. While ensuring a passage between the upper end of the side wall on the developer carrier side in the developer supply transport path, the developer blocked by the developer regulating member is prevented from moving to the surface side of the developer carrier. Those having a blocking member are described. Then, the peak position of the magnetic flux density in the normal direction of the pumping magnetic pole for pumping the developer beyond the upper end of the side wall provided by the magnetic field generating means is arranged below the lower end of the supply passage. It is said that the purpose of A layer of a developer in an insufficiently mixed state (hereinafter referred to as an insufficiently mixed developer) of the regulated retained developer and another developer pumped from the developer supply transport path is sent into the developing area. The purpose is to suppress the occurrence of such a situation and suppress the deterioration of image quality due to uneven image density.

However, in a conventional developing apparatus, the amount of the developing agent supplied may be insufficient or the mixing condition may be insufficient depending on the width of the supply passage in the direction orthogonal to the rotation axis direction of the developing agent carrier. There remains a problem that the agent is sent to the developing area and the image density unevenness cannot be completely suppressed.

In order to solve the above-mentioned problems, the present invention includes a developer carrier having a magnetic field generating means inside, carrying a developer containing a toner and a magnetic carrier and transporting the developer to a developing region by rotation, and a developer regulating member. The developer supply transport path and the supply passage for passing the developer in the developer supply transport path to the developer carrier side are connected to the upper end of the side wall of the developer supply transport path on the developer support side. A developing apparatus having a developing device that prevents the developer blocked by the developer restricting member from moving to the surface side of the developing agent carrier while securing the space between the developing apparatus. The width of the supply passage in a direction orthogonal to the rotation axis direction of the body is set to 7% or more and less than 10% of the outer diameter peripheral length of the developer carrier.

According to the present invention, it is possible to satisfactorily suppress image density unevenness due to insufficient supply of the developing agent and insufficient mixing of the developing agent being sent to the developing region as compared with the conventional case.

The schematic block diagram which shows the printer which concerns on embodiment. Enlarged view of the developing device. Another enlarged view of the developing device. Still another enlarged view of the developing device. Explanatory drawing of the flow of the developer of the developing apparatus. Another explanatory view of the flow of the developer of the developing apparatus.

Hereinafter, an embodiment of a printer that forms an image by an electrophotographic method as an image forming apparatus provided with a developing apparatus to which the present invention is applied will be described. The printer according to the embodiment described below is merely an example of an image forming apparatus to which the present invention is applied. The present invention is not limited thereto.

FIG. 1 is a schematic configuration diagram showing a printer according to an embodiment. The printer according to the embodiment includes a drum-shaped photoconductor 1 as an image carrier. The photoconductor 1 is rotationally driven by the driving means in the direction (clockwise) indicated by the arrow A in the drawing. A charging device 2, a developing device 3, a transfer device 4, a cleaning device 5, and a static elimination device 6 are arranged around the photoconductor 1 as uniform charging processing means. A resist roller pair 7 is provided below the photoconductor 1, an optical writing device 8 and the like are provided above the photoconductor 1. Further, a paper feed cassette 30, a paper feed roller 31, a fixing device 32, a paper discharge path 33, a paper discharge roller pair 34, a paper discharge tray 35, and the like are also provided.

The drum-shaped photoconductor 1 is uniformly charged by the charging device 2. The surface of the photoconductor 1 is light-scanned by the writing light L emitted from the optical writing device 8. In the entire area of the photoconductor 1, the region irradiated with the writing light L by optical scanning attenuates the potential and carries an electrostatic latent image.

Then, as the photoconductor 1 is driven to rotate, the electrostatic latent image enters the position facing the developing device 3. The developing apparatus 3 develops the electrostatic latent image to obtain a toner image by adhering toner to the electrostatic latent image of the photoconductor 1 in a developing region which is a region facing the photoconductor 1. The toner image developed in this way enters the transfer unit where the photoconductor 1 and the transfer device 4 face each other as the photoconductor 1 is driven to rotate.

On the other hand, the paper feed cassette 30 is mounted on the printer body. The paper feed roller 31 is in contact with the recording sheet P as the top transfer body in the sheet bundle housed in the paper feed cassette 30. A resist roller pair 7 is arranged near the end of the paper feed path. The resist roller pair 7 feeds the recording sheet P toward the transfer portion which is the opposite portion between the photoconductor 1 and the transfer device 4.

The transfer device 4 forms a transfer electric field that electrostatically moves toner from the photoconductor 1 side to the recording sheet P side between the recording sheet P sent to the transfer unit and the electrostatic latent image of the photoconductor 1. .. The toner image on the photoconductor 1 is transferred to the surface of the recording sheet P sent to the transfer unit by the action of the transfer electric field.

The recording sheet P that has passed the transfer unit is sent to the fixing device 32. The recording sheet P sent to the fixing device 32 is heated and pressurized in the fixing nip to fix the toner image on the surface.

On the other hand, the surface of the photoconductor 1 that has passed through the transfer portion enters the position facing the cleaning device 5. The cleaning device 5 includes a cleaning member. The transfer residual toner adhering to the surface of the photoconductor 1 is scraped off from the surface of the photoconductor 1 by a cleaning member. After that, the surface of the photoconductor 1 is statically eliminated by the uniform static elimination device 6. The surface of the statically eliminated photoconductor 1 is uniformly charged again by the charging device 2 to prepare for the next latent image formation.

The recording sheet P that has passed through the fixing device 32 is discharged to the outside of the machine via the paper ejection path 33 and the paper ejection nip of the paper ejection roller vs. 34. Then, it is stacked on the output tray 35 provided outside the machine.

FIG. 2 is an enlarged view of the developing device 3. FIG. 1 is a view seen from the opposite side of the paper. The basic configuration of the developing device 3 is the same as that of the developing device described in Patent Document 1. That is, a non-rotating magnet roller 12a as a magnetic field generating means is provided inside, and a developing agent containing a toner and a magnetic carrier is supported on the surface by the magnetic force generated by the magnet roller 12a and rotated to cause a photoconductor. A developing roller 12 is provided as a developing agent carrier that conveys the developing agent to the developing region facing the surface of 1. The developing sleeve of the developing roller 12 is rotated as shown by an arrow B (clockwise in the figure).

Further, a developer that forms a regulation gap between the surface of the developing roller 12 and the surface of the developing roller 12 for regulating the amount of the developer that is conveyed to the developing region by passing the developer supported on the surface of the developing roller 12. A doctor blade 13 as a regulating member is provided.

Further, the developer arranged adjacent to the surface of the developing roller 12 and supplied on the surface of the developing roller 12 is conveyed along the rotation axis direction of the developing roller 12 by the conveying screw member 14 as the developing agent supply and conveying member. At the same time, it is provided with a developer supply transport path 15 for collecting the developer that has fallen as shown by the arrow C in the figure, which is blocked by the doctor blade 13 from passing through the regulation gap.

The magnet roller 12a in the developing roller 12 extends the developer in the developing agent supply transport path 15 beyond at least the upper end (lower end of the supply passage) 24 on the developing roller 12 side of the developing agent supply transport path 15. It is provided with a pumping magnetic pole S2 for generating a pumping magnetic force for pulling to the side and pumping to the surface of the developing roller 12, and a regulating magnetic pole N2 for generating a regulating magnetic force for causing the developer passing through the regulating gap to stand. The pumping magnetic pole S2 and the regulating magnetic pole N2 are adjacent to each other in the developing roller surface moving direction and have opposite polarities to each other. In addition to this, the developing region is also provided with a developing main pole N1 and conveying magnets S1 and S3.

The lower conveying magnetic pole S3 and the pumping magnetic pole S2 of the developing roller 12 have the same magnetism, and the developing agent separates from the surface of the developing roller during this period and falls into the lower developing agent recovery path 28. A transport screw member 29 is housed in the developer recovery path 28. In the developer recovery path 28 and in the developer supply transfer path 15, the developer is conveyed in opposite directions in the axial direction of the developing roller, and is connected at the ends to form a developer circulation path. Toner is appropriately replenished from the toner replenishing device to the developer recovery path 28.

Then, between the upper end of the side wall (lower end of the supply passage) 24 of the developer supply transport path 15, the developer in the developer supply transport path 15 at least over the entire area in the developing roller rotation axis direction of the developing region is indicated by the arrow D in the drawing. As shown by, while securing the supply passage 20 for passing to the developing roller 12 side, the developing agent blocked from passing through the regulating gap by the doctor blade 13 is on the surface side of the developing roller 12 along the magnetic field lines of the regulated magnetic force. It is provided with a blocking member 21 that prevents the user from moving to.

As shown in FIG. 2, the lower end 24 of the supply passage 20 coincides with the upper end of the side wall. Further, the upper end 22 of the supply passage 20 coincides with the lower end of the blocking member 21. The width W of the supply passage 20 in the direction orthogonal to the rotation axis direction of the developing roller 12 is 7% or more and less than 10% of the outer diameter peripheral length of the developing roller 12. The developer is sufficiently supplied by setting the outer diameter to 7% or more of the peripheral length. By setting the outer diameter to less than 10%, it is possible to prevent the developing agent having a low density and not being mixed well on the inner upper side of the transport screw member 14 from being pumped up.

Further, as shown in FIG. 3, the upper end 22 of the supply passage 20 is set to a position lower than the height of the upper end 23 of the outer diameter of the transport screw member 14. As a result, it is possible to prevent the developing agent having a low density on the upper side of the transport screw member 14 from being pumped up, and it is possible to prevent the occurrence of unevenness. Further, the lower end 24 of the supply passage 20 is positioned above the rotation center 25 of the transport screw member 14. As a result, it is possible to prevent the developer from being pumped up under the developer supply transport path 15 having uneven density due to the blades of the transport screw member 14, which is caused by the uneven density of the developer due to the blades of the transport screw member 14. The occurrence of unevenness (august density) can be prevented.

Further, as shown in FIG. 4, the peak position of the magnetic flux density in the normal direction of the pumping magnetic pole (S2) 26 of the developing roller 12 is a line connecting the rotation center 27 of the developing roller 12 and the rotation center 25 of the transport screw member 14. It is upstream from L1 in the developer transport direction. Further, the lower end 24 of the supply passage 20 is located downstream of the center of the pumping magnetic pole 26 (a straight line from the center 27 to the peak position direction of the magnetic flux density in the normal direction of the pumping magnetic pole 26) in the direction of rotation of the developing roller 12. To do. As a result, the line connecting the rotation center 27 of the developing roller 12 and the rotation center 25 of the transfer screw member 14, that is, the portion where the blades of the transfer screw member 14 are closest to the developer supply portion, prevents the developer from being pumped up. As a result, it is possible to prevent pumping of the developer in a portion where pitch-like unevenness is formed in the density of the developer due to the tip of the blade of the transport screw member 14, and unevenness due to the pitch of the blade of the transport screw member 14 The occurrence of (august) can be prevented.

Table 1 shows the experimental results of the ratio (%) of the width W of the supply passage 20 to the outer diameter circumference of the developing roller 12 and the state of image density unevenness. At 6%, screw pitch unevenness occurred. At 10%, uneven image density occurred.

In Table 2, in addition to the ratio (%) of the width W of the supply passage 20 to the outer diameter circumference of the developing roller 12, the width of the blocking member 21 (width Y in the direction orthogonal to the rotation axis direction of the developing roller 12). It shows the experimental result of the state of the image density unevenness when the ratio (%) with respect to the outer diameter circumference length of the developing roller 12 (see FIG. 5) was made different.

In Table 2 as well, as in Table 1, there is an appropriate range of the width of the supply passage for screw pitch unevenness. Specifically, it was confirmed that screw pitch unevenness occurred at 5.3% or less and 10.7% or more. From this, in order to prevent screw pitch unevenness, it is desirable that the range is 6.4% or more and 10% or less. Then, it was found that "haze unevenness", which is a mottled image density unevenness, occurs depending on the width of the supply passage 20 and the width of the blocking member 21. This deteriorates the image quality, though not as much as the screw pitch unevenness. That is, if the width of the blocking member 21 is too small even in the range of 6.4% or more and 10% or less, which is an appropriate width of the supply passage 20 from the viewpoint of preventing screw pitch unevenness, specifically, 3 At .2% or less, "haze unevenness" occurred. Further, when the width of the supply passage 20 is too small, specifically, when the width is 5.3% or less, even if the width of the blocking member 21 is 6.4% or 8.5%, "haze unevenness" occurs.

After diligent research on the cause of "mist unevenness", the following was found. When the fluidity of the developer decreases in a high temperature and high humidity environment, the amount of the developer supplied to the developing roller 12 through the supply passage 20 decreases, and the developing agent on the developing roller 12 becomes insufficient. Then, the developer is attracted from the developer supply transport path 15 so as to get over the upper side of the blocking member 21 by the magnetic force of the developing roller 12, and the developer whose addition of the regulation gap is blocked by the doctor blade 13 is the developer supply transport path. The movement to return to 15 is restricted.

FIG. 5A is an explanatory view of the movement of the developer in a normal state, and FIG. 5B shows the movement of the developer when the developer is sucked from the developer supply transport path 15 so as to get over the upper side of the blocking member 21. It is explanatory drawing of. In these figures, only the developer supply transport path 15 of the developer supply transport path 15 and the developer recovery path 28 is shown. The movement of the developer attracted from the developer supply transport path 15 so as to get over the upper side of the blocking member 21 is indicated by an arrow E. Reference numeral G indicates a retention region of the developer whose addition of the regulation gap is prevented by the doctor blade 13.

The developer toner retained in the retention region G has a high charge amount, and the developer toner freshly pumped from the developer supply transport path 15 has a low charge amount. Since these pass through the doctor blade 13 while being mixed, uneven image density of "mist unevenness" occurs due to uneven mixing. The movement of the developer attracted from the developer supply transport path 15 so as to get over the upper side of the blocking member 21 (arrow E in FIG. 5B) increases as the width of the supply passage 20 decreases and the upper end position of the blocking member 21. The lower the value, the more likely it is to occur.

In Table 2, if the width of the blocking member is too large even in the range of 6.0% or more and 10% or less, which is an appropriate width of the supply passage 20 from the viewpoint of preventing screw pitch unevenness, specifically. At 13.8% or more, abnormal images of white streaks occurred over time. As shown in FIG. 6, the upper end of the blocking member was too high, and the developer in the retention region G could not be recirculated to the developer supply transport path 15 and solidified. By setting the width of the blocking member to 11% or less, preferably 10% or less, the circulation of the developer in the retention region G to the developer supply transport path 15 can be prevented from being hindered.

The image defect of the screw pitch on the upper right of Table 2 occurs because the upper end position of the blocking member 21 is high, the width of the supply passage 20 is small, and the amount of the developer supplied is small. The image defect of the screw pitch at the lower left of Table 2 is that the upper end position of the supply passage 20 is too high, and the developer that has passed from the retention region G above the blocking member 21 and reached above the developer supply transport path 15 is supplied as it is. It gets into the passage 20 and is supported by the developing roller 12. That is, it is generated because the original function of the blocking member 21 that prevents the developer blocked by the doctor blade 13 from moving to the surface side of the developing roller 12 cannot be fully exhibited. Conceivable.

From the results shown in Table 2, in order to prevent both screw pitch unevenness and "haze unevenness", the width of the supply passage is 6% or more and 10% or less, and the width of the blocking member is 6% or more, 11 The range of% or less (more preferably 6% or more and 10% or less) is preferable.

1: Photoreceptor 2: Charging device 3: Developing device 4: Transfer device 5: Cleaning device 6: Static elimination device 7: Resist roller pair 8: Optical writing device 12: Developing roller 12a: Magnet roller 13: Doctor blade 14: Conveyance Screw member 15: Developer supply transport path 20: Supply passage 21: Blocking member 32: Fixing device 23: Upper end 24: Side wall upper end 25: Rotation center 26: Pumping magnetic pole 27: Rotation center 28: Developer recovery path 29: Conveyor screw Member 30: Paper feed cassette 31: Paper feed roller 32: Fixing device 33: Paper discharge path 34: Paper discharge roller pair 35: Paper discharge tray N1: Developing main pole N2: Regulator magnetic pole S1: Conveying magnetic pole S2: Pumping magnetic pole S3: Conveying magnetic pole

JP 2015-22118

Claims (7)

A developer carrier having a magnetic field generating means inside, carrying a developer containing toner and a magnetic carrier, and transporting the developer to the developing region by rotation.
Developer control member and
Developer supply transport path and
The development while securing a supply passage for passing the developer in the developer supply transport path to the developer carrier side with the upper end of the side wall on the developer carrier side in the developer supply transport path. A developing apparatus having a developing device that prevents the developer blocked from passing by the agent regulating member from moving to the surface side of the developer carrier.
A developing apparatus characterized in that the width of the supply passage in a direction orthogonal to the rotation axis direction of the developer carrier is 7% or more and less than 10% of the outer diameter peripheral length of the developer carrier. Claim 1 is characterized in that the width of the blocking member in a direction orthogonal to the rotation axis direction of the developer carrier is set to 6% or more and 11% or less of the outer diameter peripheral length of the developer carrier. The developing apparatus according to. A developer carrier having a magnetic field generating means inside, carrying a developer containing toner and a magnetic carrier, and transporting the developer to the developing region by rotation.
Developer control member and
Developer supply transport path and
The development while securing a supply passage for passing the developer in the developer supply transport path to the developer carrier side with the upper end of the side wall on the developer carrier side in the developer supply transport path. A developing apparatus having a developing device that prevents the developer blocked from passing by the agent regulating member from moving to the surface side of the developer carrier.
The width of the supply passage in the direction orthogonal to the rotation axis direction of the developer carrier is set to 6% or more and 10% or less of the outer diameter peripheral length of the developer carrier.
A developing apparatus characterized in that the width of the blocking member in a direction orthogonal to the rotation axis direction of the developer carrier is 6% or more and 11% or less of the outer diameter peripheral length of the developer carrier. The developer supply transport path includes a screw member that transports the developer carrier along the rotation axis direction, and the upper end of the supply passage is at a position lower than the height of the upper end of the outer diameter of the screw member. The developing apparatus according to any one of claims 1 to 3. The developer supply transport path includes a screw member that transports the developer carrier along the rotation axis direction, and the lower end of the supply passage is located above the rotation center of the screw member. The developing apparatus according to any one of claims 1 to 4. The magnetic field generating means includes a pumping magnetic pole for pumping the developer beyond the upper end of the side wall, and the peak position of the magnetic flux density in the normal direction of the pumping magnetic pole is the rotation center of the developer carrier and the screw member. According to claim 4 or 5, the lower end of the supply passage is located above the center of the pumping magnetic pole, and is set on the upstream side in the developer transport direction from the line connecting the center of rotation of the above. The developing device described. An image forming apparatus including the developing apparatus according to any one of claims 1 to 6.

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