JP5975630B2 - Development device - Google Patents

Description

  The present invention relates to a developing device used in an image forming apparatus using an electrophotographic system.

  An electrophotographic image forming apparatus is applied to a digital copying machine or printer, and develops an electrostatic latent image formed by exposing the outer peripheral surface of a uniformly charged photosensitive drum with toner. Thus, a visualized toner image is formed, transferred to a recording medium, and fixed. In such an image forming apparatus, for example, a two-component developer composed of toner and a carrier is used, and the charged toner is attached to the outer peripheral surface of the photosensitive drum via the developer carrier in the developing apparatus. The electrostatic latent image is developed.

  The developing device includes, for example, an agitation conveyance unit that agitates and frictionally charges while conveying toner in the developer, and a supply conveyance unit that supplies the charged toner to the developer carrying member while conveying the charged toner. For example, the agitation transport unit and the supply transport unit may be arranged in a horizontal direction, or may be arranged in a vertical direction. In the developing device in which the agitation conveyance unit and the supply conveyance unit are arranged vertically, for example, when the developer is conveyed to the end of the agitation conveyance unit by the conveyance screw, the developer is lifted upward by the conveyance pressure and supplied and conveyed. (For example, refer patent document 1). In addition, a technique for lifting the developer upward by magnetic force is also known in order to facilitate the delivery of the developer between the stirring conveyance unit and the supply conveyance unit arranged above and below (see, for example, Patent Document 2). ).

JP 2009-25724 A JP-A-10-31363

  However, for example, when the supply conveyance unit is arranged above the agitation conveyance unit, it is difficult to secure a sufficient amount of developer lift by conveyance pressure or magnetic force by the conveyance screw, and a large amount of developer is contained in the agitation conveyance unit. Tends to occur. For this reason, sufficient mixing and stirring of the developer is hindered, and there is a problem in that the image quality tends to deteriorate.

  The present invention has been made in view of the above points, and an object of the present invention is to make the developer stay smoothly in the agitating and conveying section by smoothly transferring the developer between the agitating and conveying section and the supply and conveying section. In other words, sufficient mixing and stirring of the developer can be easily performed.

The first invention is
A developer carrying member carrying a developer containing toner and a carrier;
An agitation transport unit that transports the developer in the first transport direction while stirring the developer;
The developer carrier disposed above the agitation conveyance unit and conveying the developer transferred from the agitation conveyance unit via the communication unit in a second conveyance direction opposite to the first conveyance direction. A supply conveyance section for supplying to
A developing device comprising:
The stirring and conveying unit is
A rotating shaft provided rotatably,
A first spiral blade formed on the rotating shaft and transporting the developer in the first transport direction;
A second spiral blade that is formed in multiple lines downstream of the first spiral blade in the rotation shaft in the first transport direction and transports the developer in the first transport direction;
A third spiral blade that is formed in multiple lines downstream of the second spiral blade in the rotation axis in the first transport direction and transports the developer in the second transport direction;
Have
The second and third spiral blades have the same number of strips and leads, and the positions in the rotational direction of the ends adjacent to each other are the same,
The communication part is
It is provided in the position corresponding to the 2nd and 3rd spiral blade | wing of the said stirring conveyance part.

  As a result, the developer in the agitation conveyance unit is conveyed while being agitated by the first spiral blade, and is conveyed to the positions of the second and third spiral blades. Therefore, the second and third spiral blades are spirals in opposite directions, have the same number of multiple strips (for example, two strips), and leads, and positions in the rotational direction of the ends adjacent to each other. Are formed in the same manner, the developer acts to be gathered toward the central portions of the second and third spiral blades and lifted upward. In addition, since the second and third spiral blades are formed in multiple stripes, the lifting action works several times during one rotation, and the developer is efficiently received by the supply and conveyance section via the communication section. Passed. Therefore, since the developer is smoothly transferred between the agitation conveyance unit and the supply conveyance unit, it is easy to obtain a stable developer flow by reducing the retention of the developer in the agitation conveyance unit. it can. Therefore, it is possible to easily improve the mixing / stirring performance by securing the length of the developer stirring region and / or to keep the length of the developing device short.

The second invention is
A developing device according to a first invention,
The outer diameters of the second and third spiral blades are formed larger than the outer diameter of a region excluding at least the vicinity of the communicating portion in the first spiral blade.

  As a result, the gap between the tips of the second and third spiral blades and the housing is kept small, and the distance between the supply and transport unit is kept short. Therefore, the transport loss is reduced, the ascending force acting on the developer is kept large, and the transport efficiency from the stirring transport unit to the supply transport unit is easily increased.

The third invention is
Any one of the first and second inventions,
The developer conveyance speed by the agitation conveyance unit is set to be higher than the developer conveyance speed by the supply conveyance unit.

  Thus, the agitation conveyance unit and the supply conveyance unit are circulated according to the developer conveyance capacity of the agitation conveyance unit and the supply conveyance unit and the amount of developer supplied to the developer carrier in the supply conveyance unit. Therefore, it is possible to easily maintain an appropriate flow rate balance of the developer.

The fourth invention is:
A developing device according to any one of the first to third inventions,
The supply conveyance unit is
A rotating shaft provided rotatably,
A spiral blade formed on the rotating shaft and transporting the developer in the second transport direction;
Have
The rotating shaft is characterized in that a shaft diameter of a portion corresponding to the communication portion in the supply / conveyance portion is set smaller than a shaft diameter of other portions.

  As a result, a larger receiving space is ensured in the supply and conveyance section for the developer pushed up by the second and third spiral blades of the agitating and conveying section, so that the developer can be delivered smoothly. it can.

  According to the present invention, the developer is smoothly transferred between the agitation conveyance unit and the supply conveyance unit, the amount of the developer staying in the agitation conveyance unit is reduced, and the developer is sufficiently mixed. Stirring can be easily performed.

FIG. 3 is a partial cross-sectional front view of the developing device according to the embodiment of the present invention. It is an enlarged view of the principal part of FIG. It is the III-III sectional view taken on the line of FIG. It is the IV-IV sectional view taken on the line of FIG.

  An example of a developing device according to an embodiment of the present invention will be described in detail with reference to the drawings. The developing device is provided in the image forming apparatus as a developing unit, for example, and forms a toner image by developing an electrostatic latent image formed by exposure of a photosensitive drum with a two-component developer including toner and a carrier. To do. The formed toner image is transferred to a recording medium via a transfer belt, for example, and fixed by heating. This will be specifically described below.

(Schematic configuration of the developing device 100)
As shown in FIGS. 1 to 4, the developing device 100 includes an agitating and conveying unit 110, a supply and conveying unit 120, and a developing roller 130. The agitation transport unit 110 agitates the developer in the left direction (arrow A direction) in FIG. 1 by a driving force transmitted from the outside of the developing device 100 through the gear box 150, for example. . The supply conveyance unit 120 is provided immediately above the agitation conveyance unit 110, and the developer delivered from the agitation conveyance unit 110 in the upward direction (arrow B direction) via the communication unit 142 is moved to the right in FIG. It is supplied to the developing roller 130 while being conveyed in the (C direction). When the remaining developer supplied to the developing roller 130 is conveyed to the end of the supply conveyance unit 120, it moves downward (in the direction of arrow D) via the communication unit 143 and is replenished as necessary. The toner is stirred and conveyed again by the agitating and conveying unit 110 together with the toner, and the circulation is repeated.

  The developing roller 130 includes, for example, a sleeve (not shown) and a magnet provided therein, and the developer supplied from the supply / conveyance unit 120 is predetermined by the developer layer regulating member 160 (FIGS. 3 and 4). After being regulated by the layer thickness of the photosensitive drum, it is carried to the vicinity of a photosensitive drum (not shown), and the electrostatic latent image formed on the peripheral surface of the photosensitive drum is developed with toner in the developer.

(Detailed configuration of stirring and conveying unit 110 and supply and conveying unit 120)
The agitating / conveying unit 110 includes a housing 140 in which a first rotating member 111 having a rotating shaft 111 a is rotatably provided via a bearing 112. A spiral blade 111b that stirs while transporting the developer is provided in a region excluding the vicinity of the downstream end of the rotation shaft 111a in the developer transport direction. Although not particularly limited, the spiral blade 111b is partially provided with a paddle 111c, for example, in order to further stir the developer.

  A forward double spiral blade 111d, a gap 111e, a reverse double spiral blade 111f, and a short lead reverse spiral blade 111g are provided in this order on the rotating shaft 111a downstream of the spiral blade 111b in the developer conveying direction. .

  The above-mentioned two-row spiral blade 111d and the reverse two-row spiral blade 111f are formed in two spirals opposite to each other and both have the same lead (ie, 1/2 pitch) as the spiral blade 111b. Yes. Moreover, the position of the rotation direction of the edge part which mutually adjoins in spiral blade 111d * 111f is formed in the same (same phase). The lengths of the spiral blades 111d and 111f are set to, for example, 1/2 or more of the lead (pitch) of the spiral blade 111b. The length of the gap portion 111e between the spiral blades 111d and 111f is set to, for example, ¼ or more and ½ or less of the lead of the spiral blade 111b, more specifically, for example, about 6 mm.

  The short lead reverse spiral blade 111g is provided between the reverse double spiral blade 111f and the bearing 112, and is formed at a shorter pitch than the spiral blade 111b, so that the developer is less likely to aggregate near the bearing 112. Yes.

  The spiral blades 111d and 111f, the short lead reverse spiral blade 111g, and the end of the spiral blade 111b on the side of the forward double spiral blade 111d (for example, a 1/2 pitch portion) are more than other portions of the spiral blade 111b. The large-diameter portion 111h having a large outer diameter is formed.

  The agitating / conveying unit 110 and the supply / conveying unit 120 disposed thereabove are partitioned by a partition wall 141 and communicate with each other via a communicating unit 142 formed at a position corresponding to the spiral blades 111d and 111f. It has become.

  On the other hand, the supply conveyance unit 120 includes a housing 140 in which a second rotation member 121 having a rotation shaft 121 a is rotatably provided via a bearing 122. The rotating shaft 121a is provided with a spiral blade 121b that supplies the developer to the developing roller 130 while conveying the developer. The outer diameter of the rotating shaft 121 a is set larger than the rotating shaft 111 a of the first rotating member 111, and the developer conveying speed by the second rotating member 121 is slower than that of the first rotating member 111. Yes. However, the outer diameter of the rotating shaft 121a in the vicinity of the communication portion 142 is set smaller than the other portions so that the developer flowing in from the communication portion 142 is easily delivered.

(Operation of the developing device 100)
In the developing device 100 configured as described above, the developer in the stirring and transporting unit 110 is transported in the direction of arrow A in FIG. 1 while being stirred by the spiral blade 111b. When the developer is conveyed to the position of the spiral blades 111d and 111f, the spiral blades 111d and 111f are formed in spirals in opposite directions, so that the developer is narrowed toward the gap 111e. The action of being gathered and lifted upward works. In addition, since the spiral blades 111d and 111f are formed in a double spiral, the lifting action works twice while the rotating shaft 111a makes one rotation, and the developer is efficiently supplied and conveyed through the communication part 142. Is passed on.

  Further, the spiral blades 111d and 111f, the short lead reverse spiral blade 111g, and the end portion (for example, a 1/2 pitch portion) of the spiral blade 111b on the side of the forward double spiral blade 111d are formed as the large diameter portion 111h. Therefore, the gap between the tips of the spiral blades and the housing 140 is kept small, and the distance between the spiral blades 121b of the supply conveyance unit 120 (from the tips of the spiral blades 111d and 111f to the partition wall 141). (Gap + thickness of partition wall 141 + gap from partition wall 141 to the tip of spiral blade 121b) can be kept short, so that transport loss is reduced, the ascending force acting on the developer is kept large, and transport efficiency is improved. Easily enhanced.

  Further, since the short lead reverse spiral blade 111g is provided at a position where the communication portion 142 is not formed (a position where the partition wall 141 exists) at the extreme end of the first rotating member 111, the vicinity of the bearing 112 The developer is surely pushed back in the right direction in FIGS. Therefore, the degree to which the bearing 112 is buried in the developer is reduced, and the developer can easily be prevented from entering the bearing 112 portion.

  On the other hand, the developer pushed up by the spiral blades 111 d and 111 f of the agitation transport unit 110 as described above is delivered to the supply transport unit 120 via the communication unit 142. Here, a small-diameter portion 121a ′ is formed in the vicinity of the communication portion 142 of the rotating shaft 121a of the supply conveyance portion 120, and a larger space for receiving the developer is secured, so that the developer is easily transferred smoothly. .

  A part of the developer delivered to the supply conveyance unit 120 is supplied to the developing roller 130 while being conveyed in the direction of arrow C in FIG. 1 by the spiral blade 121 b of the second rotating member 121. The developer conveying speed by the second rotating member 121 is slower than that of the first rotating member 111 because the outer diameter of the rotating shaft 121a is set larger than the rotating shaft 111a of the first rotating member 111. Become. Therefore, the flow rate balance of the developer circulating through the agitation transport unit 110 and the supply transport unit 120 is appropriately maintained. The developer conveying speed is not limited to the outer diameter of the rotating shaft as described above, but may be set based on the pitch of the spiral blade, the outer shape, the rotating speed, or a combination thereof.

  The developer conveyed to the end by the supply conveyance unit 120 moves in the direction of arrow D in FIG. 1 through the communication unit 143, and new toner is replenished as necessary near the communication unit 143. The agitating and conveying unit 110 stirs and conveys the material again, and circulation is repeated.

  As described above, the agitating / conveying unit 110 and the supplying / conveying unit 120 are provided in the vicinity of the communicating portion 142 where the developer is transferred from the agitating / conveying unit 110 to the supply / conveying unit 120. Since, for example, the developer is smoothly transferred to and from the developer, even when the length of the communication portion 142 is set to about 20 mm, the staying length of the developer in the stirring and conveying portion 110 is about 45 mm. And a stable developer flow can be easily obtained. Therefore, the agitating / conveying unit 110 and the supply / conveying unit 120 are arranged vertically so that the width of the developing device 100 can be kept small, and the length of the agitating region of the developer is ensured for mixing / stirring. The performance can be improved and / or the length of the developing device 100 can be easily reduced.

  Furthermore, since the retention of the developer is reduced, the formation of aggregates due to heat generation or rubbing around the bearing 112 buried in the developer is less likely to occur, so that the image quality is deteriorated due to adhesion or clogging of such aggregates. Can be easily prevented.

DESCRIPTION OF SYMBOLS 100 Developing apparatus 110 Stirring conveyance part 111 1st rotation member 111a Rotating shaft 111b Spiral blade 111c Paddle 111d Order 2 spiral blade 111e Gap part 111f Reverse 2 spiral blade 111g Short lead reverse spiral blade 111h Large diameter part 112 Bearing 120 Supply Conveying section 121 Second rotating member 121a Rotating shaft 121a 'Small diameter section 121b Spiral blade 122 Bearing 130 Developing roller 140 Housing 141 Partition wall 142 Communication section 143 Communication section 150 Gear box 160 Developer layer regulating member

Claims (7)

A developer carrying member carrying a developer containing toner and a carrier;
An agitation transport unit that transports the developer in the first transport direction while stirring the developer;
The developer carrier disposed above the agitation conveyance unit and conveying the developer transferred from the agitation conveyance unit via the communication unit in a second conveyance direction opposite to the first conveyance direction. A supply conveyance section for supplying to
A developing device comprising:
The stirring and conveying unit is
A rotating shaft provided rotatably,
A first spiral blade formed on the rotating shaft and transporting the developer in the first transport direction;
A second spiral blade that is formed in multiple lines downstream of the first spiral blade in the rotation shaft in the first transport direction and transports the developer in the first transport direction;
A third spiral blade that is formed in multiple lines downstream of the second spiral blade in the rotation axis in the first transport direction and transports the developer in the second transport direction;
Have
The second and third spiral blades have the same number of strips and leads, and the positions in the rotational direction of the ends adjacent to each other are the same,
The communication part is
A developing device, wherein the developing device is provided at a position corresponding to the second and third spiral blades of the agitation transport unit.   The developing device according to claim 1,
  The developing device according to claim 2, wherein the second spiral blade is formed to have a length of ½ pitch. The developing device according to claim 1 or 2 ,
2. A developing device according to claim 1, wherein an outer diameter of each of the second and third spiral blades is larger than an outer diameter of a region excluding at least the vicinity of the communicating portion in the first spiral blade.   The developing device according to claim 3,
  The developing device characterized in that the area where the outer diameter of the second and third spiral blades is formed is an area longer than the axial length of the rotating shaft in the communicating portion. A developing device according to any one of claims 1 to 4 ,
2. A developing device according to claim 1, wherein the developer conveying speed by the agitating and conveying unit is set to be higher than the developer conveying speed by the supply and conveying unit. A developing device according to any one of claims 1 to 5 ,
The supply conveyance unit is
A rotating shaft provided rotatably,
A spiral blade formed on the rotating shaft and transporting the developer in the second transport direction;
Have
The developing device according to claim 1, wherein a shaft diameter of a portion corresponding to the communication portion in the supply and transport portion is set to be smaller than a shaft diameter of another portion.   The developing device according to claim 6,
  The developing apparatus according to claim 1, wherein the spiral blade of the supply / conveyance unit is formed such that a pitch of an end portion on the side of the communication unit is longer than other regions.

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