JP2004279979A - Developing unit of image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing unit of a simple and inexpensive constitution for an image forming apparatus which prevents defective electrification of toner by securely agitating the toner while using none of expensive members such as a toner density sensor, a driving source for supplying toner, and a control circuit and preventing toner from being excessive in the developing unit. <P>SOLUTION: A section 3 which has locally decreased transport capacity is provided downstream from a developer supply port 13 of an agitating and transporting means 1, and a 2nd section 6 which has increased agitating capacity and locally reduced transport capacity by extending a rib 4 to the outer circumference of a spiral shape member is provided further downstream therefrom. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD 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, and a multifunction machine using an electrophotographic method, and more particularly, to 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 in which toner is sufficiently stirred while preventing an excessive amount of toner in the developing device, thereby preventing charging failure.
[0002]
[Prior art]
2. Description of the Related Art In an image forming apparatus using an electrophotographic method, a developer agitating and conveying member is used to supply charged toner to a developing roller for developing a latent image formed on a photoconductor. As a method of compensating for the toner consumed by developing the latent image on the photoreceptor, 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 in which a sensor for detecting the toner density is provided, and the toner is supplied from the toner container when the toner density 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 decreases. It must be complicated and expensive.
[0003]
Therefore, similarly, Patent Documents 3 and 4, which are inventions of a developing device in an image forming apparatus using a two-component developer, provide a mechanism for reciprocating a toner cartridge for supplying toner and provide the mechanism at one end in the toner cartridge. An apparatus has been proposed in which the toner is moved to the vicinity of a discharge port, and the toner is freely dropped and supplied into a 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 require a mechanism for reciprocating the toner cartridge, and thus must be expensive. Further, the vibration is transmitted to the image forming apparatus itself by the reciprocating mechanism, which may affect other mechanisms to cause image deterioration.
[0004]
For this reason, the applicant of the present application disclosed in Patent Document 5 and the like that toner was agitated from a toner receiving port provided at one end of a developing device, dropped freely on a conveying member, and used a special driving source, a control circuit, a reciprocating mechanism, and the like. Proposed a developing device capable of replenishing toner without using the toner. In a developing device that stirs toner without using a special drive source or control circuit and freely falls onto a 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, the toner is immediately conveyed to make an empty space, and the toner is replenished and the supply becomes excessive, causing the toner to be clogged and the toner circulation to be hindered. May cause charge-up, fogging or a decrease in density, and if this condition continues, the toner pressure near the developing roller will increase, and the toner will stick to the sleeve surface of the developing roller and form a pitch. Since abnormal images such as crests may occur, the agitation and transport capability of the transport member downstream of the toner drop position in the developing device Locally allowed reduced, it has been proposed to prevent clogging of the toner. To cope with such an excessive supply of toner, it is conceivable to reduce the shape of the toner supply port in advance. However, the entire amount of toner in the developing device becomes small, and the amount of consumed toner and the supplied amount of toner are reduced. The balance may be lost and printing may not be possible, which is not preferable.
[0005]
Patent Document 6 discloses a developing device using a toner concentration sensor. In a developing device in which toner is stirred and charged by a spiral stirring screw, toner is supplied to the toner concentration sensor immediately from a toner supply port. When the toner is transported, the stirring performance is insufficient, and the toner concentration varies.Therefore, the height of the shaft having the spiral stirring screw becomes lower as the distance from the toner hopper side decreases, and becomes the lowest at the portion of the toner concentration sensor, and thereafter gradually. , A plate-like developer agitating means is set up to increase the agitation performance of the replenished toner from large to small and the transport performance from small to large so that the replenished toner agitates well with the developer. The developing device is shown to be conveyed and conveyed.
[0006]
Patent Document 7 discloses that in a developing device in which a two-component developer is stirred and charged by a helical stirring screw, the flowability deteriorates and uniform mixing becomes difficult as the diameter of the toner or carrier is reduced. Therefore, on the downstream side of the developer replenishing section, a rectifying plate protruding in the radial direction on the spiral stirring screw shaft is provided to reduce the ability to transport the developer in the axial direction as compared with other parts. A similar rectifying plate is protrudingly provided on the downstream side further away from the stagnating portion by a predetermined distance to provide a second stagnating portion having a greater conveying capacity of the developer in the axial direction than the first stagnating portion. 2 shows a developing device capable of performing stirring.
[0007]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 2000-112220 [Patent Document 2]
Japanese Patent Application Laid-Open No. 2000-112221 [Patent Document 3]
Japanese Patent Application Laid-Open No. 2002-72645 [Patent Document 4]
JP 2002-99136 A [Patent Document 5]
JP 2001-235933 A [Patent Document 6]
Japanese Patent Application Laid-Open No. H10-123811 [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 and conveying member and the inner wall of the developing apparatus is about 1 mm. As a result, stagnation was generated in the portion where the conveying ability of the stirring and conveying member was locally reduced, and the amount of toner falling from the supply port could be controlled. However, in the case of an image forming apparatus that handles a large-sized recording medium such as A3, since the stirring and conveying members are long, the stirring and stirring are performed in consideration of the rotation unevenness of the conveying member, and the distance between the conveying member and the inner wall of the developing device is reduced from 1 mm. It is necessary to widen the toner to 2 mm. Therefore, sufficient toner accumulation cannot be obtained only in the portion where the agitation and the transporting ability of the transporting member are locally reduced due to the spread, and the toner can be freely released from the toner cartridge. Falling can no longer be prevented enough. Further, when the distance between the outer edge of the stirring and conveying member and the inner wall of the developing device is increased, the toner supplied between the inner wall and the stirring and conveying member is clogged and hardened, and the toner does not fall. Stirring could not be performed, and inconveniences such as poor charging and image unevenness sometimes occurred. This phenomenon does not cause much problem because the two-component developer has relatively good fluidity, but it sometimes appears remarkably in a developing device using a one-component developer.
[0009]
Further, the device described in Patent Document 6 is expensive as described above because it is a developing device using a toner concentration sensor, and the device described in Patent Documents 6 and 7 has a shaft having a spiral stirring screw. , Which stirs the supplied toner before reaching the toner concentration sensor, and further extends such a member over a long section. In the case of a developing device using a one-component developer, the toner hardly moves along the outer wall of the developing tank because the toner hardly moves down as described above. In some cases, the toner amount is insufficient or the toner cannot be sufficiently stirred, resulting in poor charging, causing problems such as image unevenness.
[0010]
Therefore, in the present invention, in a developing device that can continuously and freely drop toner from a toner container to a developing device without using expensive members such as a toner density sensor and a driving source and a control circuit for supplying toner. A simple and inexpensive configuration of a developing device in an image forming apparatus which is capable of reliably stirring the toner while preventing the toner amount from becoming excessive in the developing device and preventing the toner from being charged poorly. The challenge is to provide the
[0011]
[Means for Solving the Problems]
Therefore, in the present invention,
A stirring / conveying unit for supplying a developer supplied from a supply port of the developer accommodating unit to the developing roller for developing the latent image formed on the photoreceptor while stirring the developer; In a developing device in an image forming apparatus provided with a portion having a locally reduced transport capacity downstream of the supply port,
The stirring and conveying means has a spiral-shaped member erected from a shaft, and a rib is wrapped around an outer peripheral portion of the spiral-shaped member downstream of the portion where the conveying capacity is locally reduced to increase the stirring capacity. The present invention is characterized in that a second portion is provided, which is increased and locally reduced in transport capacity.
[0012]
In this way, a portion where the transport capacity is locally reduced is provided downstream of the developer supply port, and further downstream, a rib is wrapped around the outer peripheral portion of the helical member to locally increase the stirring capacity while increasing the stirring capacity. By providing a second portion with reduced toner amount, it is possible to prevent the toner amount from becoming excessive in the developing device, and to handle the outer edge of the agitating and conveying member and the developing device in order to handle a large recording medium such as A3. Even if the distance between the inner wall and the inner wall of the spiral member is increased, the toner between the inner wall and the agitating / conveying member can be agitated by the ribs extending over the outer peripheral portion of the spiral member, and the amount of toner may be insufficient or the agitation may not be sufficient. Thus, it is possible to provide a developing device in an image forming apparatus capable of always forming a good image with a simple and inexpensive configuration by preventing a problem such as charging failure and image unevenness.
[0013]
Further, a developing device is provided downstream of the portion where the second stirring ability is reduced, and further provided with a third transporting ability reduced portion in which a rib is extended around the outer periphery of the spiral stirring member. The developing device in the image forming apparatus, which can further control the amount of toner in the image forming apparatus, prevents a problem such as charging failure and image unevenness by sufficiently stirring the toner, and can always form a good image, has a simple and inexpensive configuration. Can be provided.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be illustratively 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 to them unless otherwise specified, and are merely mere descriptions. This is just an example.
[0015]
1 and 2 are schematic perspective views showing an embodiment of a stirring and conveying means constituting a developing device in the image forming apparatus according to the present invention, and FIG. 3 is a cross section of the developing device in the image forming apparatus according to the present invention. FIGS. 4 and 5 are cross-sectional views of a stirring and conveying means constituting a developing device in the image forming apparatus according to the present invention, and FIG. 5 is a plan view of an image forming apparatus main body according to the present invention.
[0016]
In the figure, the same components are denoted by the same reference numerals, 1 is a stirring and conveying means constituting a developing device in the image forming apparatus according to the present invention, 2 is a spiral-shaped member constituting the stirring and conveying means 1, Reference numeral 3 denotes a spiral member having an outer diameter smaller than the outer diameter of the spiral member 2 in other portions in order to locally reduce the toner transporting ability in the agitating / transporting means 1. 7, a rib provided on an outer peripheral portion of the apparatus, 8 is a shaft of a stirring and conveying means, 10 is a developing device in the image forming apparatus according to the present invention, 11 is a second stirring and conveying means, 12 is a developing roller, and 13 is a toner roller. The supply port 14 is formed shorter than the length in the axial direction in the developing chamber 15 and is erected so that both ends are free. Upright walls 40, 41, 42 and 43 for separating the agitation and conveyance means 1 and 11 are supplied. This is the toner conveyance direction.
[0017]
FIG. 3 is a cross-sectional view of the developing device in the image forming apparatus according to the present invention in a direction perpendicular to the axial direction of the stirring and conveying means, FIG. 4 is a cross-sectional view of the stirring and conveying means in the axial direction, and FIG. As shown in the plan views of the apparatus main body, respectively, the main body of the developing apparatus 10 has stirring, conveying means 1, 11, and a developing roller 12, and the toner supplied from the toner supply port 13 (FIG. 3) is As shown by arrows 40, 41, 42, and 43 in FIG. 5, the sheet is conveyed, circulated with stirring, and supplied to the developing roller 12.
[0018]
As shown in detail in FIGS. 1, 2 and 4, the agitating / transporting means 1 has a helical member 3 provided immediately below the toner supply port 13 on the downstream side and an outer diameter of the other helical member 2. The spiral member 6 is made smaller, and a rib is wrapped around the outer periphery of the spiral member 6 as shown at 4. Further, the downstream spiral member 7 spaced from the spiral member 6 has a rib. The rib 5 is shorter than that of the spiral member 6. For this reason, the toner supplied from the toner supply port 13 first remains in this portion because the conveying capacity is reduced by the spiral member 3 having a short outer diameter provided immediately below the toner supply port 13 and provided on the downstream side. An excessive amount of toner is prevented.
[0019]
Since the rib 4 is provided on the helical member 6 subsequent thereto, the toner extruded in the outer peripheral direction by the rotation of the helical member 6 is given a force in the rotational direction by the rib 4 to the shaft 8. Even if the distance between the outer edge of the agitating and conveying member and the inner wall of the developing device is increased to handle a large recording medium such as A3, the toner supplied between the inner wall and the agitating and conveying member is not removed. Clogging and hardening can be prevented, sufficient stirring is achieved, and the transport speed in the transport direction 40 is reduced. However, the transport speed of the spiral-shaped member 6 is faster than the transport speed of the toner by the spiral-shaped member 3 on the upstream side, so that the toner amount in this portion is reduced. Then, the helical member 2 that follows feeds the toner at a normal speed, but the helical member 7 that follows is provided with the ribs 5 similarly to the helical member 6. As described above, the toner is conveyed at a low speed and sufficient agitation is performed. In addition, due to the presence of the rib, the upright wall 14 formed shorter than the length in the axial direction and having both ends open is opened. Is moved to the second stirring / transporting member 11 side.
[0020]
Therefore, the toner supplied from the supply port 13 has a low feeding speed at the portion of the spiral member 3 having a small diameter, becomes faster at the portion of the spiral member 6 provided thereafter, and is sufficiently stirred by the ribs 4. In the following spiral-shaped member 2, it is further faster, and in the subsequent spiral-shaped member 7, the stirring is sufficiently performed by the presence of the rib 5, and it is faster than the spiral-shaped member 6 but slower than the immediately preceding spiral-shaped member 2. The feed speed changes in each part according to the condition, and is sent to the second stirring / transporting member 11 side. As a result, excessive supply of toner is suppressed in the portion of the helical member 3 and the toner is sufficiently agitated by the presence of the ribs 4 and 5, and in the subsequent portions, as a whole, the arrow 41 in FIG. The amount of toner sent to the stirring and conveying member 11 side is reduced.
[0021]
Therefore, the toner supplied between the inner wall of the developing device and the outer edge of the agitating and conveying member is clogged and hardened, so that the toner does not fall and the agitation and the supply to the conveying member are hindered. It is possible to prevent the agitation from being caused by the inability to stir, thereby preventing a problem such as image unevenness from occurring. In the developing chamber 15 on the side where the developing roller 12 is located, the spiral member 6 and the spiral member 7 are provided. 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 stirring and conveying unit 1 described above is used for the maximum toner capacity in the developing device 10 of 250 g, Was constantly controlled to about 180 to 200 g. Further, when a toner such as yellow was mixed with the black toner, and the time until the yellow toner became visible on the developing roller 12 was measured, and the stirring and conveying means 1 described above was not used and was not used. In some cases, the case where the method was used was about 1 minute later than the case where the method was not used. That is, when the stirring and conveying means 1 described above is used, the stirring is performed well.
[0023]
【The invention's effect】
As described above, according to the present invention, a portion where the transport capacity is locally reduced is provided downstream of the developer supply port, and further downstream, a rib is wrapped around the outer peripheral portion of the spiral member to increase the stirring capacity. However, by providing the second portion having a locally reduced transport capacity, it is possible to prevent the toner amount from becoming excessive in the developing device and to use a stirring and transporting member for handling a large recording medium such as A3. Even if the distance between the outer edge of the helical member and the inner wall of the developing device is increased, the ribs extending over the outer peripheral portion of the spiral member can stir the toner between the inner wall and the agitating / transporting member. It is possible to provide a developing device in an image forming apparatus capable of always forming a good image with a simple and inexpensive configuration, by preventing the occurrence of such a problem or insufficiency of stirring and preventing problems such as charging failure and image unevenness.
[Brief description of the drawings]
FIG. 1 is a schematic perspective view showing an embodiment of a stirring and conveying means 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 stirring and conveying means constituting a developing device in the image forming apparatus according to the present invention.
FIG. 3 is a 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 stirring / transporting unit that forms a 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]
DESCRIPTION OF SYMBOLS 1 Stirring and conveying means 2, 6, 7 Spiral member 3 Spiral member 4, 5 of which outer diameter is smaller than other outer diameter Rib 8 Axis 10 Developing device 13 Toner supply port 40 Toner conveying direction

Claims (2)

A stirring / conveying unit for supplying a developer supplied from a supply port of the developer accommodating unit to the developing roller for developing the latent image formed on the photoreceptor while stirring the developer; In a developing device in an image forming apparatus provided with a portion having a locally reduced transport capacity downstream of the supply port,
The stirring and conveying means has a spiral-shaped member erected from a shaft, and a rib is wrapped around an outer peripheral portion of the spiral-shaped member downstream of the portion where the conveying capacity is locally reduced to increase the stirring capacity. A developing device in an image forming apparatus, comprising: a second portion having increased and locally reduced transport capacity. An image characterized in that a third transport-reduced portion is provided downstream of the portion where the second stirring capability is reduced and a third transport capability is reduced by bridging a rib around the outer periphery of the spiral stirring member. A developing device in the forming device.

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