JP4079324B2 - Developing device in image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device in an image forming apparatus such as a copying machine, a printer, a facsimile, or a composite machine using an electrophotographic system, and more particularly, a developing device capable of continuously dropping toner from a toner container to the developing device. The present invention relates to a developing device in an image forming apparatus that prevents toner from becoming excessive in the developing device and prevents the toner from being sufficiently stirred to prevent poor charging.
[0002]
[Prior art]
In an image forming apparatus using an electrophotographic system, a developer agitating and conveying member is used to supply charged toner to a developing roller for developing a latent image formed on a photoreceptor. As a method for supplementing the toner consumed by developing the latent image on the photosensitive member, for example, Patent Documents 1 and 2 which are inventions of a developing device in an image forming apparatus using a two-component developer are disclosed. As described above, there is a sensor that detects the toner concentration and supplies toner from the toner container when the toner concentration decreases. However, the devices described in Patent Documents 1 and 2 require a toner concentration detection sensor and a device including a drive source and a control circuit for supplying toner when the toner concentration is lowered. It must be complicated and expensive.
[0003]
For this reason, in Patent Documents 3 and 4 that are inventions related to a developing device in an image forming apparatus using a two-component developer, a mechanism for reciprocating a toner cartridge that supplies toner is provided at one end of the toner cartridge. An apparatus has been proposed in which toner is moved to the vicinity of the discharge port, and the toner is freely dropped and supplied into the developing device. However, the devices described in Patent Documents 3 and 4 do not require a sensor or a driving source for supplying toner, but need a mechanism for reciprocating the toner cartridge, which must be expensive. Further, the vibration is transmitted to the image forming apparatus itself by the reciprocating mechanism, which may affect other mechanisms and cause image deterioration.
[0004]
For this reason, in the case of Patent Document 5 or the like, the present applicant stirs the toner from the toner receiving port provided at one end of the developing device, freely drops it onto the conveying member, and uses a special drive source, control circuit, and reciprocating mechanism. We have proposed a developing device that can replenish toner. Further, in such a developing device that stirs the toner without using a special drive source or control circuit and freely drops it on the conveying member, the amount of toner agitated on the developing device side and the amount of toner conveyed by the conveying member are uniform. In this case, even if the toner is supplied from the toner receiving port, it is immediately transported to be vacant, and further, the toner is replenished to cause excessive supply, resulting in toner clogging and hindering the circulation of the toner. May cause charge-up, fogging and density reduction, and if this condition continues, the toner pressure near the developing roller will rise, and the toner will adhere to the sleeve surface of the developing roller and become pitch-like. Abnormal images such as crests may occur, so agitation on the downstream side of the position where the toner falls in the developing device and the conveying ability of the conveying member Locally allowed reduced, it has been proposed to prevent clogging of the toner. In order to deal with such excessive supply of toner, it may be possible to reduce the shape of the toner replenishing port in advance. However, the total amount of toner in the developing device becomes small, and the amount of toner consumed and the amount of supply are reduced. The balance may be lost and printing may not be possible.
[0005]
Patent Document 6 discloses a developing device using a toner concentration sensor. However, in a developing device that stirs and charges toner with a helical stirring screw, the toner is immediately supplied to the toner concentration sensor from the toner supply port. When it is carried, the stirring performance becomes insufficient and the toner density varies, so the height of the shaft having the spiral stirring screw decreases as it moves away from the toner hopper side, and becomes the lowest at the toner density sensor, and then gradually. A plate-like developer agitating means is set up to increase the agitating performance of the replenished toner from large to small and the conveying performance from small to large, so that the replenished toner is well agitated with the developer. The developing device is shown to be conveyed.
[0006]
In Patent Document 7, in a developing device that stirs and charges a two-component developer with a spiral stirring screw, fluidity deteriorates and uniform mixing becomes difficult as the diameter of the toner or carrier decreases. For this reason, a first baffle plate is provided on the downstream side of the developer replenishment portion so as to project radially from the helical stirring screw shaft, thereby reducing the developer conveying ability in the axial direction from the other portions. A second stagnation part is provided on the downstream side at a predetermined distance from the stagnation part, with a similar rectifying plate protruding so that the developer conveying capacity in the axial direction is greater than that of the first stagnation part. 1 shows a developing device which can be stirred.
[0007]
[Patent Document 1]
JP 2000-112220 A [Patent Document 2]
JP 2000-112221 A [Patent Document 3]
JP 2002-72645 A [Patent Document 4]
JP 2002-99136 A [Patent Document 5]
Japanese Patent Laid-Open No. 2001-235933 [Patent Document 6]
Japanese Patent Laid-Open No. 10-123811 [Patent Document 7]
JP 2001-183899 A
[Problems to be solved by the invention]
In the developing device proposed in Patent Document 5, for example, when the maximum size of the recording medium handled by the image forming apparatus is about A4, the distance between the outer edge of the stirring / conveying member and the inner wall of the developing device is about 1 mm. Thus, the amount of toner falling from the replenishing port can be controlled by causing stagnation in the portion where the conveying ability of the agitating and conveying member is locally reduced. However, in the case of an image forming apparatus handling a large recording medium such as A3, since the stirring and transporting members are long, the distance between the stirring and transporting members and the inner wall of the developing device is from 1 mm in consideration of uneven rotation of stirring and transporting members As a result, it is necessary to spread the toner to 2 mm. Therefore, only the portion where the agitating and the conveying ability of the conveying member are locally reduced cannot obtain a sufficient amount of toner, so that the toner from the toner cartridge is free. The fall could not be prevented sufficiently. Further, when the distance between the outer edge of the stirring / conveying member and the inner wall of the developing device is increased in this way, the toner supplied between the inner wall and the stirring / conveying member is clogged and solidified, and it does not fall off. Stirring could not be performed, leading to problems such as poor charging and image unevenness. This phenomenon is not a problem because the fluidity is relatively good in the two-component developer, but it may be noticeable in a developing device using the one-component developer.
[0009]
The device described in Patent Document 6 is a developing device using a toner density sensor, and thus is expensive as described above. Further, the devices described in Patent Documents 6 and 7 are shafts having a helical stirring screw. Has a plate-like developer agitating means, which is for agitating the supplied toner until it reaches the toner concentration sensor. In the developing device using a one-component developer, the toner hardly moves along the outer wall of the developing tank, so that the toner is solidified and does not fall as described above. Is hindered, resulting in insufficient toner amount or insufficient stirring, resulting in poor charging, and problems such as image unevenness.
[0010]
Therefore, in the present invention, in the developing device that allows the toner to freely fall continuously from the toner container to the developing device without using an expensive member such as a toner concentration sensor, a drive source for supplying toner, or a control circuit. A simple and inexpensive construction of the developing device in the image forming apparatus that prevents the toner amount from being excessive in the developing device while reliably stirring the toner and prevents the toner from being poorly charged. It is a problem to provide in.
[0011]
[Means for Solving the Problems]
Therefore, in the present invention, the developing roller for developing the latent image formed on the photosensitive member has an agitating member that supplies the developer supplied from the supply port of the developing tank containing the developer while stirring. ,
The agitating member is formed by winding a spiral wall along the developer transport direction corresponding to the rotation of the rotation shaft, and outside the other spiral wall on the downstream side of the developer supply port in the developer transport direction. In the developing device in the image forming apparatus provided with the first portion in which the diameter is locally reduced and the conveyance capability is locally reduced,
The spiral stirring member locally extends a rib around the outer peripheral portion of the spiral wall located downstream in the developer transport direction following the first portion, and increases the stirring ability at the portion and transports the rib. A second portion with reduced ability is provided .
[0012]
Thus, the developer conveying direction downstream side, the first site locally reduce the carrying capacity by locally reducing the outer diameter than the other spiral wall provided from the developer supply port, further wherein A second rib that locally extends a rib on the outer peripheral portion of the spiral wall located downstream in the developer conveying direction following the first part, and increases the stirring ability and reduces the carrying ability at that part. in Rukoto provided site, while preventing the toner amount in the developing apparatus becomes excessive, increasing the distance between the inner wall of the developing device and the outer edge of the spiral wall to handle a large recording medium such as A3 Even so, the ribs hung around the outer periphery of the helical stirring member can stir the toner between the inner wall and the helical wall , preventing the toner from becoming insufficient or insufficiently charged. To prevent problems such as image unevenness and The developing device in the image forming apparatus capable of forming a good image, easy, can be provided with an inexpensive configuration.
[0013]
In addition, a third portion where a rib is locally spanned on the outer peripheral portion of the spiral wall with a spiral wall portion having no rib interposed therebetween on the downstream side of the developer transport direction of the second portion. by providing Rukoto, the toner amount in the developing apparatus can be further controlled, the developing device in sufficient toner agitation performed to prevent problems such as poor charge and image unevenness, always image forming apparatus capable of forming a good image Simple, inexpensive configuration can be provided.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be exemplarily described in detail with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention only to those unless otherwise specified. This is just an example.
[0015]
1 and 2 are schematic perspective views showing an embodiment of a helical stirring member constituting a developing device in the image forming apparatus according to the present invention, and FIG. 3 is a cross-sectional view of the developing device in the image forming apparatus according to the present invention. 4 is a cross-sectional view of a helical stirring member constituting the developing device in the image forming apparatus according to the present invention, and FIG. 5 is a plan view of the main body of the image forming apparatus according to the present invention.
[0016]
In the drawings, the same components are denoted by the same reference numerals, 1 being a helical stirring member constituting a developing device in the image forming apparatus according to the present invention, and 2 a helical wall portion constituting the helical stirring member 1. 3 because allowed to locally reduce the conveying capacity of the toner in the spiral agitating member 1, spiral agitating member 4, 5 and smaller outer diameter than the outer diameter of the helical wall portion 2 in the other part spiral agitating member 6 and 7, ribs 8, 8 is a shaft of a helical stirring member , 10 is a developing device in the image forming apparatus according to the present invention, 11 is a second helical stirring member , 12 is a developing roller, and 13 is a developing roller. The toner supply port 14 is formed in the developing chamber 15 so as to be shorter than the length in the axial direction so that both ends are vacant, and the upright walls 40, 41, 42, and 43 for separating the helical stirring members 1 and 11 are supplied. This is the direction in which the toner is conveyed.
[0017]
A developing device in an image forming apparatus according to the present invention, a cross-sectional view of a direction perpendicular to the axial direction of the spiral stirring member 3, an axial sectional view of a helical stirring member 4, 5 As shown in each of the plan views of the developing device main body, the main body of the developing device 10 includes the helical stirring members 1 and 11 and the developing roller 12, and the toner supplied from the toner supply port 13 (FIG. 3) is supplied. 5, as indicated by arrows 40, 41, 42, and 43 in FIG. 5, it is circulated while being stirred and supplied to the developing roller 12.
[0018]
Among spiral agitating member 1, Fig. 1, as shown in detail in FIG 2, FIG. 4, the helical wall portion 3 provided on the downstream side from just below the toner supply opening 13 of the other helical wall portion 2 It is made smaller than the outer diameter, and the spiral wall portion 6 that follows is provided with a rib around the outer peripheral portion as indicated by 4, and further, a downstream spiral shape spaced from the spiral stirring member 6. the wall portion 7, is shorter ribs 5 than that looped helically wall portion 6 is stretched. For this reason, the toner supplied from the toner supply port 13 first remains in this portion because the conveyance capability is reduced by the helical wall 3 having a small outer diameter provided immediately below the toner supply port 13 and downstream. It is possible to prevent the toner amount from becoming excessive.
[0019]
Then, since the rib 4 is provided in the spiral wall portion 6 which follow, the toner pushed out in the outer circumferential direction by the rotation of the spiral wall portion 6 a force in the rotational direction is provided by the rib 4 of the shaft 8 Even if the space between the outer edge of the helical stirring member and the inner wall of the developing device is increased in order to handle a large recording medium such as A3, it is supplied between the inner wall and the helical stirring member . The toner can be prevented from being clogged and solidified, and the toner can be sufficiently stirred and the conveyance speed in the conveyance direction 40 can be reduced. However, since the conveyance speed by the spiral wall portion 6 is faster than the toner conveyance speed by the upstream spiral wall portion 3, the amount of toner in this portion is reduced. And while sending to the toner in the helical wall portion 2 following normal speed it, because the same rib 5 and the helical stirring member 6 is provided in the spiral wall portion 7 which follow, the spiral wall portion As described above, in the portion 7 as well, the toner conveyance speed is slowed down and sufficient stirring is performed, and due to the presence of this rib, the upright wall 14 is formed so as to be shorter than the axial length and to be open at both ends. The toner is moved to the second helical stirring member 11 side from the position where the opening is opened.
[0020]
Accordingly, the toner supplied from the supply port 13 has a slow feeding speed in the portion of the small-diameter spiral wall portion 3, becomes faster than that in the portion of the spiral wall portion 6 provided thereafter, and is sufficiently stirred by the rib 4. In the spiral wall portion 2 that follows, the spiral wall portion 7 that follows the spiral wall portion 7 is sufficiently agitated by the presence of the rib 5 and is earlier than the portion of the spiral wall portion 6 but is immediately preceding the spiral wall portion 6. The feed speed is changed at each portion so as to be slower than 2, and the feed is sent to the second spiral stirring member 11 side. As a result, excessive supply of toner is suppressed in the portion of the spiral wall 3 and the second portion is generally shown in FIG. The amount of toner sent to the spiral stirring member 11 side is reduced.
[0021]
Therefore, the toner supplied between the inner wall of the developing device and the outer edge portion of the helical stirring member is clogged and solidified, and does not fall, hindering the supply to the helical stirring member , resulting in insufficient toner amount. It is possible to prevent agitation from occurring due to the inability to stir and to cause problems such as image unevenness, and the development chamber 15 on the side where the developing roller 12 is provided is provided in the spiral wall portion 6 and the spiral wall portion 7. Due to the presence of the ribs 4 and 5, only a necessary amount of toner that has been sufficiently stirred is supplied.
[0022]
In the developing device in the image forming apparatus according to the present invention configured as described above, when the helical stirring member 1 described above is used for the maximum toner capacity in the developing device 10 being 250 g, The amount of toner was always controlled to about 180 to 200 g. Further, when a toner such as yellow was mixed with black toner and the time until the yellow toner became visible on the developing roller 12 was measured, the case where the helical stirring member 1 described above was used was not used. In some cases, it was slower by 1 minute when used than when not used. That is, when the helical stirring member 1 described above is used, the stirring is performed well.
[0023]
【The invention's effect】
As described above, according to the present invention, the part where the conveying ability is locally reduced is provided downstream of the developer supply port, and further, the stirring ability is increased by extending a rib around the outer periphery of the helical stirring member. By providing a second part with locally reduced transport capacity while preventing the amount of toner from becoming excessive in the developing device, a helical stirrer is used to handle a large recording medium such as A3. even by increasing the distance between the inner wall of the outer portion and the developing device of the member, to stir the toner between the inner wall and the helical agitating member by a rib spanned in an outer peripheral portion of the spiral stirring member, the toner amount of It is possible to provide a developing device in an image forming apparatus that can always form a good image with a simple and inexpensive configuration by preventing shortage and insufficient stirring and preventing defects such as poor charging and image unevenness. it can.
[Brief description of the drawings]
FIG. 1 is a schematic perspective view showing an embodiment of a helical stirring member constituting a developing device in an image forming apparatus according to the present invention.
FIG. 2 is a schematic perspective view showing an embodiment of a helical stirring member constituting the developing device in the image forming apparatus according to the present invention.
FIG. 3 is a cross-sectional view of a developing device in the image forming apparatus according to the present invention.
FIG. 4 is a cross-sectional view of a helical stirring member constituting the developing device in the image forming apparatus according to the present invention.
FIG. 5 is a plan view of a developing device main body in the image forming apparatus according to the present invention.
[Explanation of symbols]
1 spiral stirring member 2, 6, 7 spiral wall 3 spiral wall having an outer diameter smaller than the outer diameter of the other spiral wall 4, 5 rib 8 rotating shaft 10 developing device 13 toner supply port 40 toner Transport direction

Claims (2)

A developing roller that develops the latent image formed on the photoreceptor, and a stirring member that supplies the developer supplied from the supply port of the developing tank containing the developer while stirring;
The agitating member is formed by winding a spiral wall along the developer transport direction corresponding to the rotation of the rotation shaft, and outside the other spiral wall on the downstream side of the developer supply port in the developer transport direction. In the developing device in the image forming apparatus provided with the first portion in which the diameter is locally reduced and the conveyance capability is locally reduced,
The spiral stirring member locally extends a rib around the outer peripheral portion of the spiral wall located downstream in the developer transport direction following the first portion, and increases the stirring ability at the portion and transports the rib. A developing device in an image forming apparatus, characterized in that a second portion with reduced capacity is provided . A third portion is provided on the downstream side of the developer transport direction of the second portion, with a rib portion locally spanning the outer peripheral portion of the spiral wall with a spiral wall portion having no rib interposed therebetween. The developing device in the image forming apparatus according to claim 1.

Images