JP2005221852A - Developing apparatus and image forming apparatus using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To attain satisfactory circulation of developer by suppressing the fluctuation of developer quantity and developer distribution mainly caused by the inclined installation of a developing apparatus. <P>SOLUTION: In a state where the apparatus is provided with a developer circulating/ transporting mechanism 3 (stirring/transporting members 3a and 3b) and a trickle mechanism 4, and as the trickle mechanism 4, the apparatus is provided with a trickle discharge port 6 partly arranged on the downstream side in the transporting direction of the stirring/transporting member (for example, 3a) in a developing housing 1 and a back flow generating member 7 arranged corresponding to the trickle discharge port 6, and capable of transporting the developer in a direction opposite to the developer transporting direction by the member 3a so as to control the quantity of the developer discharged from the trickle discharge port 6, and a gap area 8 formed between the trickle discharge port 6 and the outer circumferential part of the back flow generating member 7 is set to have such a non-uniform distribution that the upper side of the back flow generating member 7 may become locally narrow. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a developing device used in an image forming apparatus such as a copying machine or a printer, and more particularly, to a developing device having a trickle mechanism for gradually replacing a new developer and an improvement of the image forming apparatus using the developing device. About.

Conventionally, various proposals have been made for developing devices used in image forming apparatuses such as copying machines and printers, depending on the type of developer to be used. Among them, a two-component developer that easily secures the toner charge amount is used. The two-component development method is widely adopted.
As shown in FIG. 12, for example, this type of two-component developing system developing device 240 includes a developing housing 300 that opens to face a latent image carrier 210 such as a photosensitive drum. The developer carrying member 310 is disposed facing the opening of the developing housing 300, and the developer circulating and conveying mechanism 320 is provided on the back side of the developer carrying member 310. is there.
Here, the developer circulation conveyance mechanism 320 causes the circulation conveyance paths (for example, both ends of the pair of conveyance paths 340 and 350) that are partitioned by the partition portion 330 in the developing housing 300 to communicate with each other through the communication ports 360 and 370. A pair of agitating and conveying augers 410 and 420 are provided in the conveying paths 340 and 350, and the developer in the developing housing 300 is agitated and conveyed by the agitating and conveying augers 410 and 420. However, it is conveyed to the developer carrier 310. Reference numeral 390 denotes a toner supply port.

In this embodiment, while the developer circulates in the developing device, the toner is consumed at any time along with the printing operation and replaced with new toner. However, the carrier is deteriorated while remaining in the developing device. Will cause a decline. For this reason, in the conventional developing device, it is necessary to periodically replace the developer.
Therefore, an additional mechanism called a trickle mechanism has been proposed that suppresses the deterioration of the developer by gradually replacing the developer in the developing device with a new one (see, for example, Patent Document 1).
As this kind of trickle mechanism, a developer reservoir portion whose height is regulated by a barrier is provided at the end portion of the developer circulation conveyance mechanism in the developing device, and the developer in that portion is discharged as needed, so that a new development can be performed. A method is adopted in which the developing ability of the developer can be maintained by sequentially replacing the developer.

On the other hand, in the conventional developing device, there is a technical problem that uneven conveyance of the developer easily occurs. This is due to a transport loss of the developer circulation transport mechanism 320, and the developer is locally biased to cause an image density gradient, or the developer is locally retained to reduce the effective developer amount. As a result, the deterioration of the developer is promoted and the life of the developer is reduced.
In order to solve such a problem, a technique for promoting smooth circulation in the developing device has been proposed. This is intended to solve the above-mentioned problems by providing a local difference in the transport force of the developer circulation transport mechanism and uniformizing the developer amount in the developer circulation transport mechanism (for example, Patent Document 2).

JP 2001-166593 A (Embodiment of the Invention, FIG. 4) JP 11-84874 A (Embodiment of the Invention, FIG. 2)

However, in the conventional developing device as described above, the amount of developer and the developer distribution in the developing device are very sensitive to inclination fluctuations caused by the installation state of the developing device and the image forming apparatus equipped with the developing device. There is a technical problem that it will fluctuate.
For example, as shown in Patent Document 1, in a developing device configured to provide a developer reservoir and discharge the developer as needed, the height of the developer at the barrier of the developer reservoir is constant. The developer amount changes. For this reason, the developer surface in the developing device is leveled when the developing device is provided with an inclination with respect to the axial direction of the developer circulation transport mechanism, for example, due to the installation of an image forming apparatus in an inclined position. It works to keep it. As a result, the developer distribution in the developing device is biased and the amount of developer fluctuates, which may cause various problems. For example, in the case of an inclination where the place where the height regulation of the developer as represented by the barrier is provided is on the upper side, the driving torque increases as the developer amount increases, making it difficult to drive the developing device. In contrast, if the inclination is such that the place where the developer height restriction is set down, the density gradient may occur due to the decrease in the developer amount and the uneven distribution of the developer. Or the shape pattern of the member that supplies the developer to the developer carrying member (for example, an auger mark is used when a stirring and auger is used as in this example) appears in the image. It causes the problem.

  On the other hand, as shown in Patent Document 2, even in a developing device having a configuration in which a difference is provided in the local transport force of the developer circulation transport mechanism and the amount of the developer is made uniform, The flow balance of the developer is lost, and the developer distribution in the developing device is also biased. That is, in this case as well, it can be said that the developing device is difficult to drive due to an increase in torque as described above, and image defects such as density gradients or auger marks are likely to occur.

  The present invention has been made to solve the above technical problems, and mainly suppresses fluctuations in the developer amount and developer distribution caused by the inclined installation state of the developing device, thereby achieving good developer circulation. The present invention provides a developing device and an image forming apparatus used therefor.

  That is, according to the present invention, as shown in FIGS. 1A to 1C, a developing housing 1 in which a two-component developer containing toner and a carrier is accommodated and a developing opening is opened, and the developing housing 1 A developer carrier 2 that faces the developing opening and carries a two-component developer, and a developer carrier 2 that is disposed on the back side of the developer carrier 2 in the development housing 1. A developer circulating / conveying mechanism 3 having a plurality of agitating / conveying members 3a and 3b extending in the axial direction and circulating and agitating the developer with these agitating / conveying members 3a and 3b, and a developer in the developing housing 1 In the developing device including the trickle mechanism 4 in which the old developer is gradually discharged and can be replaced with the new developer, as the trickle mechanism 4, the transport direction of the agitation transport member (for example, 3a) in the development housing 1 is used. downstream A trickle discharge port 6 opened at a part of the trickle discharge port 6 is disposed in correspondence with the trickle discharge port 6, and in order to regulate the discharge amount of the developer from the trickle discharge port 6, A reverse flow generation member 7 capable of conveying the developer in the direction opposite to the conveyance direction, and a gap region 8 between the trickle discharge port 6 and the outer periphery of the reverse flow generation member 7 is located above the reverse flow generation member 7. It is characterized by being set to a locally narrowed non-uniform distribution.

In such technical means, the present case is premised on an aspect including the developer circulation conveyance mechanism 3 and the trickle mechanism 4.
Here, the developer circulation conveyance mechanism 3 may be any one as long as it can circulate and convey the inside of a predetermined circulation path by a plurality of agitation conveyance members (usually using augers) 3a and 3b. A circulation mode in which communication ports are opened in the vicinity of both ends of the conveyance path can be mentioned. However, the present invention is not limited to this, and the developer circulation path may be constructed using three or more conveyance paths.

Further, the place where the trickle mechanism 4 is disposed may be at an arbitrary position in the developing housing 1, but is usually provided near the end in the axial direction of the developer carrier 2 in the developing housing 1.
Further, the trickle mechanism 4 may basically be provided with the trickle discharge port 6 and the backflow generating member 7, but the waste developer discharged from the trickle discharge port 6 is processed via a predetermined discharge path. In such a case, a discharge path forming member 4a communicating with the trickle discharge port 6 is provided, a discharge transport member 4b such as an auger is disposed in the discharge path forming member 4a, and one of the discharge path forming members 4a is provided. The design may be changed as appropriate, for example, by opening the discharge passage outlet 4c in the portion and discarding the waste developer from the discharge passage outlet 4c.

The trickle outlet 6 has a circular shape as a basic shape, but is not limited to this, and for example, a polygonal shape may be set as the basic shape.
Furthermore, the backflow generating member 7 may be any member as long as it transports in the direction opposite to the transporting direction of the developer in the developer circulation path, and can adopt the same configuration as the stirring transporting members 3a and 3b. However, the outer diameter and the auger transport pitch interval may be set arbitrarily.
Here, “the gap region 8 between the trickle discharge port 6 and the outer periphery of the backflow generating member 7 is set to a nonuniform distribution in which the upper side of the backflow generating member 7 is locally narrowed” The gap region 8 is not uniformly distributed with respect to the periphery of the backflow generating member 7, but the upper side of the backflow generating member 7 is narrowed, and the ratio of the gap region 8 above the backflow generating member 7 is reduced. It is intended to include widely.

In addition, a preferable layout of a locally narrow portion in the developer discharge gap region 8 distribution is locally narrow in the gap region 8 between the trickle discharge port 6 and the outer periphery of the backflow generating member 7. The portion may be a portion corresponding to at least a part of the upper part of the backflow generating member 7 that is not buried in the developer in a steady state when the developing housing 1 is horizontally disposed.
In this aspect, the situation where the developer is unnecessarily discharged as the developing device is inclined is effectively avoided.
As a typical aspect of the non-uniform distribution in the developer discharge gap region 8, the uppermost portion of the reverse flow generation member 7 in the gap region 8 between the trickle discharge port 6 and the outer periphery of the reverse flow generation member 7 is used. A mode in which the upper gap in the position is set narrower than the lower gap in the lowermost position of the backflow generating member 7 can be mentioned. Thus, if the ratio of the upper gap and the lower gap based on the uppermost position and the lowermost position of the backflow generating member 7 is selected, whether or not the gap area 8 is unevenly distributed. Is preferable in that it is easily determined.

Further, as a typical aspect of the shape of the trickle discharge port 6, the peripheral surface portion of the trickle discharge port 6 is formed in a curved surface shape, and at least the curvature of the peripheral surface portion of the trickle discharge port 6 positioned above the backflow generating member 7 Of the trickle discharge port 6 located on the periphery of the trickle discharge port 6, and the periphery of the trickle discharge port 6 is formed in a curved surface shape, and at least the periphery of the trickle discharge port 6 located above the backflow generating member 7 For example, an embodiment in which a flat portion is partially provided.
Further, as another typical aspect of the non-uniform distribution in the developer discharge gap region 8, a partial region of the trickle discharge port 6 formed of a circular hole formed in a part of the development housing 1 is shielded by a shielding member. The embodiment which was made is mentioned. According to this aspect, the shape of the trickle outlet 6 can be easily set by adding a shielding member.

Moreover, as a preferable aspect of the developer circulation conveyance mechanism 3, one provided with a cover member that covers the upper portions of the agitation conveyance members 3a and 3b along the shape of the outer peripheral portion thereof may be mentioned.
At this time, the cover member does not need to cover all of the agitating / conveying members 3a and 3b, and covers the developer as long as the developer circulation / conveyance property and the developer supply property to the developer carrier 2 are not impaired. It is necessary.
According to this aspect, covering with the cover member increases the rectification property of the developer in the developing device and further increases the developer propelling force in the developer circulation transport mechanism 3, which is accompanied by the inclined installation state of the developing device. It is possible to further improve the fastness to the uneven distribution of the developer in the developing device and the fluctuation of the developer amount.

Furthermore, this case is a chemical toner having a smooth surface shape and high fluidity (which is produced by a chemical manufacturing method instead of the conventional mechanical manufacturing method. In the case of using a toner manufactured by a technique), a higher technical effect is obtained than in the case of using a pulverized toner. This is particularly effective when a toner having a shape factor of 140 or less is used. It should be noted that shape factor = (maximum toner diameter ² / toner projected area) × (100π / 4).
That is, for example, a developer using toner having a shape factor of 140 or less has a smooth surface shape and high fluidity, and therefore, a deviation in the developer amount and developer distribution in the developing device due to the inclined installation of the developing device occurs. easy. Therefore, the present case, which is a means for solving such technical problems, can be said to be particularly effective.

In addition, the present invention is not limited to the above-described developing device, but also targets an image forming apparatus equipped with this type of developing device.
In this case, the present invention only needs to include an image carrier on which an electrostatic latent image is carried and the above-described developing device that develops toner on the electrostatic latent image on the image carrier.
In this embodiment, the image forming apparatus includes not only a model having one developing device but also a model having a plurality of developing devices.

As described above, according to the developing device of the present invention, the gap region between the trickle discharge port and the outer peripheral portion of the backflow generating member is set to a non-uniform distribution in which the upper side of the backflow generating member is locally narrowed. Therefore, the developer discharge is suppressed until the developer propulsive force increases to a force that resists the counter force generated by the backflow generating member and the developer friction force in the vicinity of the peripheral surface of the trickle discharge port. become.
That is, in the trickle mechanism according to the present invention, the magnitude of the developer driving force is more dominant than the effective developer height with respect to the developer discharge, and the developer with respect to the inclination amount of the developing device. Since the fluctuation amount is reduced, it is possible to secure a wider allowable range of the inclined installation state of the developing device than the conventional type. For this reason, even when the conventional type is biased in the developer distribution in the developing device due to the inclined installation state of the image forming apparatus or the amount of developer greatly fluctuates, the density This makes it difficult to cause image defects such as tilt and auger marks, and the inability to drive the developing device due to an increase in torque, making it possible to provide a system that is more robust than conventional types.

  Further, in the image forming apparatus equipped with the developing device described above, the trickle function of the developing device can be stabilized without being affected by the inclined installation state of the developing device. The device can be easily constructed.

Hereinafter, the present invention will be described in detail based on embodiments shown in the accompanying drawings.
Embodiment 1
FIG. 2 shows Embodiment 1 of an image forming apparatus to which the present invention is applied.
In the figure, the image forming apparatus employs, for example, an electrophotographic system. Around the photosensitive drum 21, a charging device 22 such as a corotron for charging the photosensitive drum 21 and a charged photosensitive drum 21. An exposure device 23 such as a laser scanning device for writing an electrostatic latent image thereon, a developing device 24 for developing toner on the electrostatic latent image on the photosensitive drum 21, and a toner image on the photosensitive drum 21 on a recording material 27 A transfer device 25 such as a corotron for transferring the toner and a cleaning device 26 for cleaning residual toner on the photosensitive drum 21 are sequentially arranged.

In the present embodiment, as shown in FIGS. 2 and 3, the developing device 24 has a developing opening that is opposed to the photosensitive drum 21 and contains a two-component developer containing toner and carrier. A developing roll 31 is disposed at a location facing the developing opening of the developing housing 30, and a developer circulation transport mechanism 32 is provided on the back side of the developing roll 31. Reference numeral 40 denotes a trimming member for regulating the developer layer thickness on the developing roll 31.
Here, the developing roll 31 includes a rotatable developing sleeve 31 a and a magnet roll 31 b in which a plurality of magnetic poles are arranged in a fixed manner. A predetermined gap is provided between the developing roll 31 and the photosensitive drum 21. The developing sleeve 31a is driven to rotate. Further, for example, a developing bias composed of a DC bias on which an AC is superimposed is applied to the developing sleeve 31a.

In the present embodiment, the developer circulation transport mechanism 32 divides the inside of the development housing 30 into a pair of linear transport paths 34 and 35 by the partition portion 33, and both longitudinal end portions of the partition portion 33. By forming the communication ports 36 and 37 respectively, the conveyance paths 34 and 35 are formed as circulation conveyance paths through which the developer can be circulated, and the agitation conveyance augers 41 and 42 (this example) are provided in the conveyance paths 34 and 35, respectively. The agitating / conveying auger 41 on the developing roll 31 side is hereinafter referred to as a supply auger, and the agitating / conveying auger 42 on the side away from the developing roll 31 is referred to as an admix auger).
In the present embodiment, a developer supply unit 38 is provided in the developer housing 30 on the upstream side of the admix auger 42 in the developer transport direction, and a developer supply port 39 is provided in the developer supply unit 38. Opened, one end side of the admix auger 42 is extended to the developer supply unit 38. The developer supply unit 38 may be supplied with a developer composed of toner and carrier as a whole, or may be supplied separately with toner and carrier. Further, although the developer supply unit 38 is installed on an extension line coaxial with the admix auger 42, the developer supply unit 38 may be installed as a single unit along with the developing housing 30.

In the present embodiment, a trickle mechanism 50 is provided in the developing housing 30 on the downstream side of the supply auger 41 in the developer transport direction. As shown in FIG. 4, the trickle mechanism 50 includes a waste developer restricting portion 50a for restricting the amount of waste developer discharged from the developing housing 30, and a waste developer restricted by the waste developer restricting portion 50a. And a waste developer transfer section 50b for transferring and discarding the toner.
In this example, the waste developer regulating portion 50 a opens a trickle discharge port 51 in the one end side vertical wall 30 a of the development housing 30, and the portion corresponding to the trickle discharge port 51 is opposite to the winding direction of the supply auger 41. A backflow generating auger 52 having a winding direction of 5 mm is provided coaxially with the supply auger 41.
In this example, the backflow generating auger 52 is installed on an extension line coaxial with the supply auger 41. However, the present invention is not limited to this, and the backflow generating auger 52 may be provided separately from the supply auger 41 in the developing housing 30. You may install in.
On the other hand, the waste developer transfer section 50 b has a transfer pipe 53 communicating with the trickle discharge port 51 connected to the outside of the development housing 30, and the supply auger 41 is coaxial with the backflow generating auger 52 in the transfer pipe 53. A transfer auger 54 having the same winding direction as that of the transfer pipe 53 is provided, and an outlet 55 is opened near the tip of the transfer pipe 53.

In particular, in the present embodiment, as shown in FIG. 5A, the gap region 60 between the trickle discharge port 51 and the outer periphery of the backflow generating auger 52 is locally located above the backflow generating auger 52. It is set to a non-uniform distribution narrowed. That is, in the gap region 60 between the trickle discharge port 51 and the outer peripheral portion of the backflow generating auger 52, at least a portion locally changed except for the portion buried in the developer is provided. Specifically, among the gap region 60 between the trickle outlet 51 and the outer periphery of the backflow generation auger 52, the upper gap region 61 at the uppermost position of the backflow generation auger 52 is the lowermost position of the backflow generation auger 52. It is set narrower than the lower gap area 62 of.
In the present embodiment, the trickle discharge port 51 peripheral surface portion is configured in a curved surface shape, and the trickle discharge port 51 peripheral surface portion located above the backflow generating auger 52 is configured as a curvature changing portion 63, and this curvature changing portion The curvature of 63 is set smaller than the curvature of the peripheral surface portion of the trickle discharge port 51 located below.
In the comparative form of FIG. 5B, the trickle outlet 51 is formed in a perfect circle. In this case, the gap region 60 between the trickle outlet 51 and the outer periphery of the backflow auger 52 is set as a uniform distribution. For example, the gap region 60 between the trickle outlet 51 and the outer periphery of the backflow auger 52 is set. In the gap region 60, the upper gap region 61 ′ at the uppermost position of the backflow generation auger 52 is set to be approximately the same as the lower gap region 62 at the lowermost position of the backflow generation auger 52.

Next, the operation of the developing device according to the present embodiment will be described.
In the present embodiment, as shown in FIG. 3, the developer replenished from the developer supply unit 38 is indicated by an arrow while being mixed and stirred by the admix auger 42 together with the developer stored in the developing housing 30. When it reaches the downstream end of the admix auger 42, it is pushed out from the communication port 36 and moves toward the supply auger 41. The moved developer is conveyed while being mixed and agitated by the supply auger 41, and a part of the developer is supplied onto the developing roll 31 and transferred to a developing site between the photosensitive drum 21.
The developer that is not supplied onto the developing roll 31 or returned through the developing portion is conveyed downstream while being mixed and stirred by the supply auger 41. When the developer reaches the downstream end of the supply auger 41, the developer is pushed out from the communication port 37, moves to the admix auger 42 side, and is conveyed again by the admix auger 42.

As described above, the developing device has a system that circulates in the developing housing 30 while always maintaining a constant developer amount. However, one of the excess developer obtained by subtracting the consumed amount from the replenished amount by the developer supplying unit 38. The part leaves the circulation conveyance path and is sequentially discharged by the trickle mechanism 50.
Here, the discharge of excess developer will be described in more detail. The developer that has reached the downstream end of the supply auger 41 is supplied to the developer flow generated by the supply auger 41 (developer) by the backflow auger 52 provided in the waste developer regulating section 50a as shown in FIG. A force (counter force F ₂ ) against the propulsive force F ₁ ) is applied, and works to stop the developer in a direction in which the developer is not discharged from the trickle discharge port 51.
In the trickle mechanism 50 having such a configuration, it is considered that there are mainly two discharge paths. First, the first discharge path is a path through which the developer moves over the upper part of the backflow auger 52 and moves to the waste developer transfer section 50b. This is because the backflow generating auger 52 acts as a regulating plate having a height for the developer. Actually, the volume of the developer in the developing housing 30 is substantially at the uppermost point of the backflow generating auger 52. It will be discharged by the amount exceeding the corresponding height. Next, the second discharge path is a discharge path from a portion embedded in the developer in a gap region 60 (clearance) formed by the trickle discharge port 51 and the outer peripheral portion of the backflow generating auger 52. This is discharged when the developer propulsive force F ₁ has a force sufficient to overcome the developer friction force in the vicinity of the counter force F ₂ and the trickle discharge port 51 peripheral surface.

Incidentally, the developer thrust F ₁ is changed by the inclination installation state of the developing device.
As shown in FIG. 6, when the developing device is inclined (positive inclination) in such a direction that the waste developer regulating portion 50a faces upward, the supply auger 41 (see FIG. 3) has a portion buried in the developer. since many developer packing becomes stronger, escape of developer to the surrounding supply auger 41 is reduced, so that the developer thrust F ₁ increases. On the other hand, when the developing device is inclined (minus inclined) in such a direction that the waste developer regulating portion 50a faces downward, the supply auger 41 has a smaller portion embedded in the developer and the developer packing is also weakened. Therefore, amount that the conveying force of the supply auger 41 escapes around the supply auger 41 not transmitted to the developer is increased, the developer thrust F ₁ so that the lower.

Therefore, as shown in FIG. 5A, the trickle discharge port 51 has a clearance between the trickle discharge port 51 and the outer peripheral portion of the backflow generation auger 52 so that the upper side of the backflow generation auger 52 is locally narrowed. In the aspect in which the curvature changing portion 63 is provided on the peripheral surface portion, the developer discharge from the first discharge path is suppressed, and the developer discharge from the second discharge path becomes dominant. That is, by reducing the action of the counterflow generating auger 52 as a restricting plate having a height, when the amount of developer in the developing housing 30 is small, the amount of developer increases and the developer propulsive force F ₁ is increased. The developer discharge is suppressed until it increases. Here, from the viewpoint of suppressing the developer discharge from the first discharge path, at least the portion where the clearance is narrowed at the curvature changing portion 63 of the trickle discharge port 51 is effective in which the backflow generating auger 52 acts as a restricting plate. It is applied to include as much as possible the part exceeding the height, that is, the part that is not buried in the developer when the developing device is installed horizontally and the steady state where the developer circulation and the developer discharge are antagonized. It is valid.

Thus, in the present embodiment, the curvature changing portion is formed on the peripheral surface portion of the trickle discharge port 51 so that the clearance between the trickle discharge port 51 and the outer peripheral portion of the backflow generating auger 52 is locally narrowed on the upper side. by was provided to 63, since the developer discharge the developer amount does not increase until the increased developer thrust F ₁ is not so, the variation of the developer amount relative to the inclination amount of the developing device in comparison with the conventional type Will be suppressed.
This effect is particularly effective when the curvature changing portion 63 is applied to the peripheral surface of the trickle discharge port 51 so as to include a portion that is not buried in the developer in a steady state when the developing device is horizontally installed. By suppressing the developer discharge, the variation in the developer amount with respect to the inclination amount of the developing device can be further suppressed.
In addition, by applying the curvature changing portion 63 to the upper portion of the peripheral surface of the trickle discharge port 51, most of the portion that is not buried in the developer in the steady state can be covered, which is more effective.

In the present embodiment, the curvature changing portion 63 is provided as the shape of the trickle discharge port 51. However, the present invention is not limited to this. For example, as shown in FIG. May be replaced. The flat surface portion 64 may be provided at a position that prevents the developer discharge from the first discharge path, like the curvature changing portion 63.
According to this aspect, for example, the flat surface portion 64 of the trickle discharge port 51 is disposed so as to protrude to a height equivalent to the height of the developer in a steady state when the developing device is horizontally installed, so that the first discharge path 51 Developer discharge is effectively suppressed.
As described above, by providing the flat surface portion 64 at a necessary and sufficient position to suppress the developer discharge amount from the first discharge path, it is possible to effectively suppress the change in the developer amount with respect to the inclination change of the developing device and to attach the flat portion 64. Even if the trickle discharge port 51 and the backflow generating auger 52 come into contact with each other due to an error, a manufacturing error, or a shaft runout of the backflow generating auger 52, the contact within a narrower range is sufficient. The occurrence of problems such as wear and grid of each member can be suppressed.

Embodiment 2
FIG. 8A shows a main part of a trickle mechanism used in the developing device according to the second embodiment.
In the figure, the shape of the trickle discharge port 51 is the same as that of the first embodiment, but unlike the first embodiment, the trickle discharge port 51 has a crescent-shaped shielding member in the upper region of a perfect circular hole. 65, and a portion corresponding to the curvature changing portion 63 is formed on the upper peripheral surface portion thereof, and a gap region 60 between the trickle discharge port 51 and the outer peripheral portion of the backflow generating auger 52 is The upper gap area 61 is locally narrower than the lower gap area 62.
Here, the shielding member 65 is typically made of a material that is less wearable than the material of the developing housing 30 or a material that causes less damage to the backflow auger 52, such as foam or rubber with a skin layer applied thereto. The elastic body is preferably used. When applying a skin layer on the shielding member 65, a polyethylene coating or the like is preferably used.

In the present embodiment, the shielding member 65 is used as a constituent element of the trickle discharge port 51 in addition to acting in substantially the same manner as in the first embodiment. Compared to the case of changing, it is possible to select a material with lower wear and a material with less damage to the backflow auger 52. In particular, by using an elastic body such as foam or rubber with a skin layer as the material of the shielding member 65, damage due to contact is reduced to extend the life of each member, or image defects due to generation of shavings, etc. Can be prevented. Furthermore, when a polyethylene coating is applied to the skin layer of the shielding member 65, sticking of the developer can be suppressed and occurrence of defects such as a grid can be prevented.
The shielding member 65 is not limited to the shape shown in FIG. 8A. For example, the shielding member 66 having the shape shown in FIG. 8B is provided, and the upper periphery of the trickle discharge port 51 is provided. The surface portion may have a shape corresponding to the flat surface portion 64 (see FIG. 7).

Embodiment 3
FIG. 9 shows a main part of the developing device according to the third embodiment.
In this figure, the basic configuration of the developing device is substantially the same as that of the first embodiment, but in addition to the first embodiment, the upper cover of the developing housing 30 of the developing device is further covered with a cover member 70 for developer rectification. It is constituted as follows. For example, as shown in FIGS. 9 and 10A and 10B, the cover member 70 includes cover portions 71 and 72 in which the upper sides of the supply auger 41 and the admix auger 42 are covered with the lower surface of the upper cover base plate 73 of the developing housing 30. Projecting downward.
In this example, the cover portions 71 and 72 of the cover member 70 are formed with a length corresponding to the partition portion 33 so as not to hinder the exchange of the developer between the supply auger 41 and the admixer auger 42. And it installs in the shape which does not block the communication ports 36 and 37 (refer FIG. 3). Further, the cover 72 corresponding to the admix auger 42 has a shape substantially covering the upper half of the admix auger 42, whereas the cover 71 corresponding to the supply auger 41 has a developer for the developing roll 31. In order not to hinder the supply, the upper quarter of the supply auger 41 is substantially covered so as to leave a space on the developing roll 31 side.
As a material for the cover portions 72 and 73 of the cover member 70, an elastic body such as a foam or rubber provided with a skin layer is preferably used. Similarly, when a skin layer is applied on the cover portions 71 and 72, a polyethylene coating or the like is preferably used. In the present embodiment, the cover member 70 is configured to cover both the supply auger 41 and the admix auger 42, but it may be installed on only one of them.

Therefore, in the present embodiment, in addition to acting in substantially the same manner as in the first embodiment, the cover member 70 is installed as the upper lid of the developing device, so that each auger 41, Since the developer escapes from the clearance around 42 is reduced, smooth developer circulation is realized.
With such a configuration, the escape of the developer around each auger 41, 42, in particular, the upper half of each auger 41, 42 is suppressed, and the circulation of the developer is promoted. The propulsive force F ₁ (see FIG. 4) is greatly improved. Moreover, due to the increased extent developer thrust F ₁ becomes position developer distribution is large, the bias of the developer is reduced compared with the case not including the cover member 70. In particular, when the cover member 70 is provided so as to cover the supply auger 41, the packing force of the developer delivery portion to the developing roll 31 is also improved, so that the robustness against auger mark generation is fundamentally increased.

(A) is explanatory drawing which shows the outline | summary of the image development apparatus concerning this invention, and an image forming apparatus using the same, (b) is the principal part explanatory drawing, (c) is an arrow view seen from C direction in (b). FIG. 1 is a schematic configuration diagram showing a first embodiment of an image forming apparatus to which the present invention is applied. FIG. 3 is a sectional view taken along line III-III in FIG. 2. FIG. 3 is an explanatory diagram showing a trickle mechanism of the developing device according to the first embodiment. (A) is explanatory drawing which shows the relationship between the trickle discharge port and backflow generation auger of Embodiment 1, (b) is explanatory drawing which shows the relationship between the trickle discharge port and backflow generation auger which concerns on a comparison form. It is explanatory drawing which shows the change of the developer driving force by the inclination of a developing device. FIG. 6 is an explanatory view showing a modified form of the trickle mechanism of the first embodiment. (A) is explanatory drawing which shows the principal part of the trickle mechanism of the developing device which concerns on Embodiment 2, (b) is explanatory drawing which shows the deformation | transformation form. FIG. 10 is an explanatory diagram illustrating a developing device according to a third embodiment. (A) is XX sectional view explanatory drawing in FIG. 9, (b) is explanatory drawing which shows an example of a circulation path cover. It is explanatory drawing which shows an example of the conventional developing device.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Development housing, 2 ... Developer carrier, 3 ... Developer circulation conveyance mechanism, 3a, 3b ... Agitating conveyance member, 4 ... Trickle mechanism, 4a ... Discharge passage formation member, 4b ... Discharge conveyance member, 4c ... Discharge passage Outlet, 6 ... trickle outlet, 7 ... backflow generating member, 8 ... gap area

Claims (9)

A developing housing in which a two-component developer containing toner and a carrier is accommodated and a developing opening is opened;
A developer carrying member disposed facing the developing opening of the developing housing and carrying a two-component developer;
The developing housing has a plurality of stirring and conveying members disposed on the back side of the developer carrying member and extending in the axial direction of the developer carrying member, and circulates and conveys the developer while stirring the developer with these stirring and conveying members. A developer circulation transport mechanism;
In a developing device including a trickle mechanism in which an old developer is gradually discharged from a developer in a developing housing and can be replaced with a new developer.
The trickle mechanism is provided in a part of the developing housing on the downstream side in the conveyance direction of the agitating and conveying member, and the trickle mechanism is disposed corresponding to the trickle outlet, and the developer discharge amount from the trickle outlet. A reverse flow generating member capable of transporting the developer in a direction opposite to the developer transport direction by the stirring transport member,
A developing device, wherein a gap region between a trickle discharge port and an outer peripheral portion of a backflow generating member is set to have a non-uniform distribution in which an upper side of the backflow generating member is locally narrowed. The developing device according to claim 1,
A locally narrow portion of the gap region between the trickle discharge port and the outer periphery of the backflow generating member corresponds to at least a part of the upper part of the backflow generating member that is not buried in the developer in a steady state when the developing housing is horizontally disposed. A developing device characterized by being a part. The developing device according to claim 1,
Of the gap area between the trickle outlet and the outer periphery of the backflow generating member, the upper gap area at the uppermost position of the backflow generating member is set to be narrower than the lower gap area at the lowermost position of the backflow generating member. A developing device. The developing device according to claim 1,
The trickle discharge port peripheral surface portion is formed in a curved surface shape, and at least the curvature of the trickle discharge port peripheral surface portion located above the backflow generating member is set smaller than the curvature of the trickle discharge port peripheral surface portion positioned below. A developing device. The developing device according to claim 1,
The developing device characterized in that the trickle discharge port peripheral surface portion is formed in a curved surface shape, and at least a part of the trickle discharge port peripheral surface portion located above the backflow generating member is provided with a flat surface portion. The developing device according to claim 1,
The trickle discharge port is a developing device characterized in that a partial region of a circular hole formed in a part of the developing housing is shielded by a shielding member. The developing device according to claim 1,
The developer circulation conveyance mechanism includes a cover member that covers an upper portion of the agitation conveyance member along an outer peripheral shape thereof. The developing device according to claim 1,
A developing device, wherein the developer uses toner having a shape factor of 140 or less.   9. An image forming apparatus comprising: an image carrier on which an electrostatic latent image is carried; and a developing device according to claim 1, which develops the electrostatic latent image on the image carrier with toner. apparatus.

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