JP6016521B2 - Developing device, process cartridge, image forming apparatus - Google Patents

Description

  The present invention relates to a developing device, a process cartridge including the developing device, and an image forming apparatus including the developing device.

2. Description of the Related Art Conventionally, in an electrophotographic image forming apparatus, there is known an electrophotographic image forming apparatus provided with an agitating means for agitating a developer in the developer container in order to suppress aggregation of the developer contained in the developer container. For example, Patent Document 1 discloses an agitation unit that includes an agitation shaft and a flexible agitation sheet, and agitates the developer in the developing container by rotating the agitation sheet as the agitation shaft rotates. Yes.
FIG. 5 is a schematic view showing a developing container and stirring means in a conventional developing device, and is a cross-sectional view when viewed from above in the vertical direction. Here, in FIG. 5, only the developing container 40, the stirring means 43, and the developing sleeve 41 as the developer carrying member are shown for easy understanding.
When the stirring shaft 43a is rotated in the direction of arrow D in FIG. 5 by a drive source (not shown) provided outside the developing container 40, the stirring sheet 43b fixed to the stirring shaft 43a is rotated accordingly, The developer is conveyed in a direction perpendicular to the stirring shaft 43a (in the direction of arrow α in FIG. 5).
The developer conveyed in the direction of the arrow α by the rotation of the stirring sheet 43 b moves toward the developing sleeve 41 and prepares for development in the vicinity of the developing sleeve 41.
The developing container 40 is provided with a developing opening for supplying a developer to the photosensitive member, and the developing sleeve 41 is rotatable with a part of the surface exposed to the inside of the developing container at the developing opening. Is provided.

JP 2009-288458 A

However, even if the developing device 4 having the conventional configuration rotates the stirring member 43 to create a circulation in which the developer in the developing container 40 is conveyed toward the developing sleeve 41, the developer remains at a specific location in the developing container 40. Sometimes it stays without circulating. Specifically, when the developer moves in the direction of the developing sleeve 41 by the rotation of the stirring sheet 43b, if there is a wall such as a developing container wall in the form of abutting in the moving direction, the movement of the developer is hindered by the wall. . The developer that hits the developing container wall or the like cannot move any more in the direction of the arrow α and stays at the wall.
Thereafter, a developer conveyed from the rear is further added to the staying developer near the wall, and the amount of the staying developer near the wall increases, but eventually reaches a saturation amount. In FIG. 5, the staying developer at the wall reaches the saturation amount and reaches the steady state, and the staying developer is indicated by β. Thus, the developer staying at the wall and reaching the steady state hardly moves afterwards even if the developing device 4 is continuously used, and stays at the wall in a substantially new state.
On the other hand, the developer other than the developer staying at the wall circulates in the developing container 40 by the rotation of the stirring sheet 43b, and the chargeability changes not a little in the process of repeating the circulation. This is because the developer resin in the developer container 40 is worn or deformed by mechanical rubbing while circulating. Alternatively, the external additive added to the surface is liberated or embedded in the developer resin. As a result, the chargeability of the developer other than the staying developer near the wall in the developing container 40 is different from that in the new container.
That is, when the conventional developing device 4 is used continuously, a developer whose chargeability has been changed by repeated circulation coexists with a developer that has stayed near the wall in a substantially new state. It becomes a state. This means that developers having greatly different charging characteristics coexist in the same developing container 40. In this state, for example, when a substantially new developer staying near the wall of the developing container 40 due to vibration caused by the image forming operation is mixed with a developer whose surrounding charging property has changed, developers having different charging properties are mixed with each other. As a result, a so-called low concentration may occur in which the concentration is partially reduced.

  Accordingly, an object of the present invention is to promote the circulation of the developer in the developing container and suppress the occurrence of a thin image density due to the retention of the developer.

In order to achieve the above object, the present invention
A developer container containing a developer and provided with a development opening;
A developer carrying member disposed in the development opening and capable of carrying a developer;
In the developing container, a rotating shaft having both ends pivotally supported on the side wall of the developing container, and a stirring portion provided on the rotating shaft are provided, and the stirring portion is rotated by rotating the rotating shaft. An agitating member capable of agitating the developer contained in the developing container and transporting the developer toward the developing opening in order to carry the developer on the developer carrying member;
In a developing device having
The side wall is inclined so that the distance between the side walls becomes narrower from the vicinity of the portion where the rotation shaft is pivotally supported toward the developing opening,
The distance between the side walls in the vicinity of the place where the rotating shaft is pivotally supported is Wa, the opening width of the developing opening in the axial direction of the rotating shaft is Wb, and the length of the stirring portion in the axial direction is Wc. When
It is characterized by satisfy | filling the relationship of Wa> = Wc> Wb.

The present invention also provides:
A developer container containing a developer and provided with a development opening;
A developer carrying member disposed in the development opening and capable of carrying a developer;
In the developing container, a rotating shaft having both ends pivotally supported on the side wall of the developing container, and a stirring portion provided on the rotating shaft are provided, and the stirring portion is rotated by rotating the rotating shaft. A plurality of agitating members capable of agitating the developer contained in the developing container and transporting the developer toward the developing opening in order to carry the developer on the developer carrying member;
In a developing device having
At least the rotation of the stirring member whose side wall between the vicinity of the rotation shaft of the stirring member provided at the position closest to the developing opening in the side wall and the developing opening is closest to the developing opening. From the vicinity of the place where the shaft is pivotally supported, it is inclined so that the distance between the side walls becomes narrower toward the development opening,
Wa (n) is the distance between the side walls in the vicinity of the portion where the rotating shaft of the stirring member provided n-th from the side closer to the developing opening is pivotally supported, and the developing opening in the axial direction of the rotating shaft. When the opening width is Wb, and the length of the stirring portion of the stirring member provided nth from the side closer to the development opening is Wc (n),
Wa (n + 1) ≧ Wc (n + 1) ≧ Wa (n) ≧ Wc (n)> Wb
It is characterized by satisfy | filling the relationship of these.

  The present invention is also detachable from the image forming apparatus, and is formed on the image carrier by supplying a developer to the image carrier through the image carrier and the development opening. And a developing device described above that develops an electrostatic latent image to form a developer image.

  Further, the present invention is an image forming apparatus including the developing device.

  According to the present invention, it is possible to promote the circulation of the developer in the developing container and to suppress the occurrence of a thin image density due to the retention of the developer.

Schematic sectional view showing the overall configuration of the image forming apparatus according to the present embodiment Schematic sectional view of the developing device according to this embodiment XX sectional view of the developing device shown in FIG. The figure which shows the example of the developing device provided with two stirring members Diagram showing a conventional developing device

  First, an outline of an image forming operation of an image forming apparatus 100 such as a laser beam printer according to the present embodiment will be described with reference to FIG. FIG. 1 is a schematic cross-sectional view illustrating the overall configuration of the image forming apparatus according to the present embodiment. As shown in FIG. 1, an image forming apparatus 100 includes an electrophotographic photosensitive member (hereinafter referred to as a photosensitive drum) 1 as a drum-shaped image carrier, a charging roller 2 as a charging member, an exposure device 3, a developing device 4, a transfer device. A roller 5, a cleaning device 6, a fixing device 7, and a paper feeding device 8 are provided. In this embodiment, the photosensitive drum 1 is provided to be rotatable in the direction of arrow A in FIG. In this embodiment, the process speed, that is, the peripheral speed of the photosensitive drum 1 is set to 240 mm / sec. Further, magnetic toner was used as the developer.

  First, the surface of the photosensitive drum 1 is uniformly electrostatically charged by the charging roller 2. Then, the exposure device 3 irradiates the charged surface of the photosensitive drum 1 with laser light corresponding to the image information. The charged charge is canceled at the portion of the surface of the photosensitive drum 1 irradiated with the laser beam, and an electrostatic latent image is formed on the photosensitive drum 1.

  The developing device 4 develops the electrostatic latent image and forms a toner image as a developer image on the photosensitive drum 1 (on the image carrier). Further, in synchronization with the formation of the toner image, the transfer material P such as paper is transported from the paper feeding device 8, and a voltage having a polarity opposite to the toner charging polarity is applied to the transfer roller 5. The toner image thus transferred is transferred onto the transfer material P.

  Thereafter, the transfer material P onto which the toner image has been transferred is conveyed to the fixing device 7 and the toner image is fixed to the transfer material P by heat and pressure. On the other hand, when the transfer from the photosensitive drum 1 to the transfer material P is performed, the toner remaining on the photosensitive drum 1 is scraped (removed) by a cleaning blade 60 as a cleaning member provided in the cleaning device 6 and discarded. The toner is stored in a waste toner container 61 as toner. Such a cleaning operation allows the photosensitive drum 1 to continue to form an image.

(Developer)
Next, details of the developing device according to the present embodiment will be described with reference to FIG. FIG. 2 is a schematic sectional view of the developing device according to the present embodiment. The developing device 4 is not limited to the configuration provided in the image forming apparatus 100 but may be configured in a process cartridge that is detachably attached to the image forming apparatus integrally with the photosensitive drum 1, the charging roller 2, and the cleaning device 6.

  The developing device according to the present embodiment stirs the developing container 40, the developing sleeve 41 as the developer carrying member, the regulating blade 42 that regulates the toner layer thickness on the developing sleeve 41, and the toner in the developing container 40. And a stirring member 43 that can be conveyed to the developing sleeve 41.

The developing container 40 includes a developing chamber 40a and a toner storage chamber 40b that stores toner T. The developing chamber 40a and the toner storage chamber 40b are gently partitioned by a partition 40c. The developing sleeve 41 and the regulating blade 42 are provided on the developing chamber 40a side, and the stirring member 43 is provided in the toner storage chamber 40b so as to be rotatable in the direction of arrow D in FIG. Further, the developing chamber 40 a is provided with a developing opening for supplying the toner in the developing container 40 to the photosensitive drum 1. The developing sleeve 41 is provided with a developing opening with a part of the surface exposed to the inside of the developing container 40.

  The developing sleeve 41 that can carry the toner on its surface is a non-magnetic sleeve composed of a pipe made of aluminum, stainless steel or the like, and its surface is processed to an appropriate roughness so that a desired amount of toner T can be conveyed. Yes. The developing sleeve 41 is rotatably provided in the direction of arrow C in FIGS. 1 and 2 and has a peripheral speed of 280 mm / sec. Further, the developing sleeve 41 has a magnet roller (not shown) in which a plurality of polarities are arranged.

  The regulating blade 42 is configured by fixing an elastic member 42a such as urethane rubber or silicone rubber to the support metal plate 42b, and is in contact with the developing sleeve 41 with a predetermined pressure. The toner T attracted to the developing sleeve 41 by the magnetic force of the magnet roller is frictionally charged and the layer thickness is regulated between the developing sleeve 41 and the regulating blade 42, and an appropriate charge is given.

  The stirring member 43 includes a rotating shaft 43a whose both ends are supported by the side wall of the developing container 40, and a stirring portion 43b provided on the rotating shaft 43a. Then, when the rotating shaft 43a rotates, the stirring unit 43b stirs the toner stored in the developing container 40 and conveys the toner toward the developing opening in order to carry the toner on the developing sleeve 41. The stirring unit 43b is a flexible sheet-like member, and for example, a resin such as PET (polyethylene terephthalate) can be used. Further, a resin such as polyacetal can be used for the rotating shaft 43a. The rotation speed of the stirring member 43 of this embodiment is 60 rpm.

(Position relationship of developer container and stirring member)
Next, the shape of the developing container 40 and the positional relationship between the side wall of the developing container 40 and the stirring member 43 will be described with reference to FIG. FIG. 3 is a cross-sectional view taken along the line XX of the developing device 4 shown in FIG. 2 and illustrates only the developing container 40, the developing sleeve 41, and the stirring member 43 for convenience of explanation.

  Here, among the walls constituting the developing container 40, the wall (inner wall) on which both ends of the rotating shaft 43a of the stirring member 43 are pivotally supported is referred to as a side wall. In the developing container 40 of the present embodiment, the distance between the side walls (inner walls) at a portion (hereinafter referred to as a mounting wall) in the vicinity of the rotation shaft 43a of the side walls and the axial direction of the rotation shaft 43a. The length of the opening width of the development opening is different.

  Specifically, when the distance between the side walls of the mounting wall is Wa and the length of the opening width of the development opening is Wb, the relationship of Wa> Wb is satisfied. In other words, the distance between the side walls is shorter at the position after the conveyance than at the position before the conveyance of the toner T by the stirring member 43. Further, as shown in FIG. 3, the side wall of the developing container 40 according to the present embodiment is inclined from the attachment wall having the inter-side wall distance Wa toward the developing opening, and the distance between the side walls becomes narrower toward the developing opening. It is configured as follows. Hereinafter, this inclined side wall is referred to as an inclined wall.

  The length of the stirring portion 43b that contributes to the conveyance of the toner T and the stirring in the axial direction of the rotating shaft 43a, that is, the effective stirring width Wc is the length of the opening width of the developing opening in the axial direction of the rotating shaft 43a. It is configured to be longer than Wb. Further, the effective stirring width Wc of the stirring portion 43b is configured to be equal to or less than the distance Wa between the side walls of the mounting wall. That is, in the present embodiment, the relationship between the side wall distance Wa, the opening width Wb, and the effective stirring width Wc in the mounting wall is configured such that Wa ≧ Wc> Wb.

By configuring the developing container 40 and the stirring member 43 so that Wa, Wb, and Wc have such a relationship, the circulation of the toner T in the developing container 40, particularly in the vicinity of the side wall, is promoted, and the toner T in the vicinity of the side wall is promoted. Can be prevented from staying. Hereinafter, the reason will be described by focusing on the circulation of the toner T near the inclined wall among the side walls.

(Toner circulation near the side wall)
The toner T conveyed in the direction perpendicular to the rotation shaft 43a by the stirring member 43 gradually advances in the direction of the developing sleeve 41 in the direction perpendicular to the rotation shaft 43a by the pressing force from the toner T sequentially conveyed from the rear. Go. The toner T transported near both ends of the stirring unit 43b hits the inclined wall, and beyond that, the toner T cannot travel in the direction perpendicular to the rotation shaft 43a, so the traveling direction must be changed. For this reason, the toner T hitting the inclined wall is conveyed toward the developing sleeve 41 while moving in the axial direction of the rotation shaft 43a along the inclined wall.

  Accordingly, focusing on the vicinity of the side wall, the toner flow in which the toner T conveyed in the direction perpendicular to the rotation shaft 43a by the stirring member 43 changes its traveling direction toward the center in the axial direction of the rotation shaft 43a steadily. Will occur. The flow of the toner T near the side wall at this time is indicated by a black arrow in FIG.

  Further, in this embodiment, since the effective stirring width Wc is configured to be wider than the opening width Wb of the developing opening, a part of the toner T conveyed by the stirring member 43 in the direction perpendicular to the axis is In the process of being transported to the developing sleeve 41, it always comes into contact with the inclined wall. Therefore, it is possible to surely create a toner flow that changes from the direction in which the toner travels and the direction perpendicular to the axial direction of the rotating shaft 43a toward the central portion of the rotating shaft 43a.

  As described above, in the developing device 4 of this embodiment, by creating a steady toner flow in the vicinity of the side wall, the circulation of the toner can be promoted and the retention of the toner T in the vicinity of the side wall can be suppressed. . As a result, the occurrence of low image density can be suppressed. In addition, in a present Example, it may be comprised so that the sheet-like stirring part 43b may contact an inclined wall. With such a configuration, the toner conveyed in the vicinity of both ends of the agitating portion 43b will more surely strike the inclined wall, and a toner flow near the center in the axial direction of the rotating shaft 43a is constantly generated. Can be made.

(Study results)
Since the development device according to the present embodiment and the development device having the conventional configuration were used to compare the occurrence state of the low density, the examination results will be described below. First, a conventional developing device was attached to the image forming apparatus 100 described in the present embodiment, and 10,000 horizontal line images with a 1% printing rate pattern were printed intermittently. This is done for the purpose of changing the chargeability of the toner in the developing device. After the printing is completed, the developing device is temporarily removed from the image forming apparatus 100, and the examiner shakes the developing device 10 times in the vertical direction and 10 times in the left and right directions to stir the toner in the developing device, and develops the image forming device 100 again. The device was installed. This study was performed in an environment at a temperature of 23 ° C. and a relative humidity of 50%. Then, the developing device according to this example was mounted on the image forming apparatus, and examination was performed under the same conditions. Then, all 5 black images were printed continuously, and the level of density thinness at this time was ranked in four levels by visual level. Specifically, “O” indicates no occurrence, “OΔ” indicates almost no occurrence, “Δ” indicates slight occurrence, and “X” indicates occurrence. The examination results are shown in Table 1 below.

  As shown in Table 1, in the developing device having the conventional configuration, a low density occurred due to the mixing of the toner whose charge was changed and the new toner in all the first to fifth images. On the other hand, in the developing device of this embodiment, a slight density thinness occurred on the first sheet, but almost no density thinness occurred on the second and subsequent sheets.

  As can be seen from the results of this study, in the developing device according to the present embodiment, the toner flow is created near the side wall, thereby promoting the circulation of the toner T and suppressing the toner T from staying near the side wall. be able to. As a result, when the charging property of the toner in the developing container changes with the use of the developing device, the occurrence of low density due to mixing of almost new toner with the toner having changed charging property in the developing container is suppressed. High-quality images can be provided throughout the life of the developing device.

  FIGS. 4A and 4B are diagrams illustrating an example of a developing device in which two stirring members are provided in the developing container. In the present embodiment, the developing device 4 in which one stirring member 43 is provided in the developing container 40 has been described, but the number of stirring members is not limited to one. As the capacity of the developing device 4 increases, the volume of the developing container 40 may be increased. Therefore, a plurality of stirring members may be provided in order to efficiently mix the toner in the developing container 40 as the volume increases.

  Even when a plurality of stirring members are provided, the distance Wa between the side walls, the development opening width Wb, and the effective stirring width Wc should satisfy the relationship described above for the stirring member provided at least at the location closest to the development opening. By configuring, the same effect can be obtained. That is, as shown in FIG. 4A, the relationship between the distance between the side walls, the development opening width, and the effective stirring width of the stirring member 501 provided closest to the development opening (Wa ≧ Wc> Wb) is described above. It is good to comprise so that it may satisfy | fill.

  Further, in the developing device 4 shown in FIG. 4B, unlike the configuration of FIG. 4A, the stirring member 502 and the mounting wall of the stirring member 503 provided at a location farther from the developing opening than the stirring member 502 are provided. The distance between the side walls was different. Here, the distance between the side walls of the mounting wall of the stirring member provided nth from the side closer to the developing opening is set to Wa (n), the opening width of the developing opening in the axial direction of the rotation shaft is set to Wb, and the side closer to the developing opening. Wc is the length of the stirring portion of the stirring member provided at the nth position. At this time, it is configured to satisfy the relationship of Wa (n + 1) ≧ Wc (n + 1) ≧ Wa (n) ≧ Wc (n)> Wb.

  Specifically, as shown in FIG. 4B, when the distance between the side walls of the mounting wall of the stirring member 502 is Wa2, and the distance between the side walls of the mounting wall of the stirring member 503 is Wa3, a relationship of Wa3> Wa2. It was made to become. Further, accordingly, the effective stirring widths of the stirring portions provided in the two stirring members 502 and 503 are configured to be different. Specifically, when the effective stirring width of the stirring member 502 is Wc2 and the effective stirring width of the stirring member 503 is Wc3, the relationship of Wc3> Wc2 is established.

Then, the inclined wall is configured so that the distance between the side walls becomes narrower from the mounting wall of the stirring member 503 toward the mounting wall of the stirring member 502. By configuring so that Wc3 ≧ Wa2 is satisfied, the toner conveyed in the vicinity of both ends of the stirring member 503 hits the inclined wall and moves in the axial direction of the rotation axis along the inclined wall. However, it will be conveyed in the direction of the stirring member 502. In this way, by forming the inclined wall in a stepwise manner corresponding to each of the agitating members 502 and 503, the circulation of the toner near the side wall can be further promoted, and the density reduction can be suppressed.

Development container ... 40, Development sleeve ... 41, Stirring member ... 43 Rotating shaft ... 43a, Stirring unit ... 43b,

Claims (7)

A developer container containing a developer and provided with a development opening;
A developer carrying member disposed in the development opening and capable of carrying a developer;
In the developing container, a rotating shaft having both ends pivotally supported on the side wall of the developing container, and a stirring portion provided on the rotating shaft are provided, and the stirring portion is rotated by rotating the rotating shaft. An agitating member capable of agitating the developer contained in the developing container and transporting the developer toward the developing opening in order to carry the developer on the developer carrying member;
In a developing device having
The side wall is inclined so that the distance between the side walls becomes narrower from the vicinity of the portion where the rotation shaft is pivotally supported toward the developing opening,
The distance between the side walls in the vicinity of the portion where the rotating shaft is supported is Wa, the opening width of the developing opening in the axial direction of the rotating shaft is Wb, and the length of the stirring unit in the axial direction is Wc. When
A developing device configured to satisfy a relationship of Wa ≧ Wc> Wb. A developer container containing a developer and provided with a development opening;
A developer carrying member disposed in the development opening and capable of carrying a developer;
In the developing container, a rotating shaft having both ends pivotally supported on the side wall of the developing container, and a stirring portion provided on the rotating shaft are provided, and the stirring portion is rotated by rotating the rotating shaft. A plurality of agitating members capable of agitating the developer contained in the developing container and transporting the developer toward the developing opening in order to carry the developer on the developer carrying member;
In a developing device having
At least the rotation of the stirring member whose side wall between the vicinity of the rotation shaft of the stirring member provided at the position closest to the developing opening in the side wall and the developing opening is closest to the developing opening. From the vicinity of the place where the shaft is pivotally supported, it is inclined so that the distance between the side walls becomes narrower toward the development opening,
Wa (n) is the distance between the side walls in the vicinity of the portion where the rotating shaft of the stirring member provided n-th from the side closer to the developing opening is pivotally supported, and the developing opening in the axial direction of the rotating shaft. When the opening width is Wb, and the length of the stirring portion of the stirring member provided nth from the side closer to the development opening is Wc (n),
Wa (n + 1) ≧ Wc (n + 1) ≧ Wa (n) ≧ Wc (n)> Wb
A developing device configured to satisfy the above relationship.   The developing device according to claim 1, wherein the stirring unit is configured by a sheet-like member.   The developing device according to claim 1, wherein the agitating unit is provided so as to contact an inclined portion of the side wall.   5. The developing device according to claim 1, wherein a part of the surface of the developer carrying member is exposed to the inside of the developing container at the developing opening. 6. It is detachable from the image forming apparatus,
An image carrier;
6. The developer image is formed by supplying a developer to the image carrier through the developing opening to develop an electrostatic latent image formed on the image carrier to form a developer image. A developing device,
A process cartridge comprising:   An image forming apparatus comprising the developing device according to claim 1.

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