JP2010282040A - Developing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing device capable of continuously and stably supplying only a necessary amount of a developer having appropriate toner density and a charge quantity from a developer storage unit to a developing unit. <P>SOLUTION: The developing device includes: the developing unit; the developer storage unit 40; a rotary feeder 50 provided below the developer storage unit to discharge the developer in the developer storage unit; and a developer circulation means for transferring the developer discharged from the rotary feeder by using air. The rotary feeder 50 includes: a stator 55; an inflow port 56 formed at the upper side of the stator through which the developer from the developer storage unit flows in; a discharge port 57 formed at the lower side of the stator through which the developer is discharged; and a rotatably supported rotor 51 disposed in a space of the stator and having a plurality of blades radially extending from a shaft. At least one of the inflow port and the discharge port of the rotary feeder is formed in a position shifted from a vertical center line drawn from the rotation axis of the rotor. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a developing device using a two-component developer composed of a toner and a carrier, and an image forming apparatus such as a copying machine, a printer, a plotter, a facsimile, or a complex machine including the developing device.

In an electrophotographic image forming apparatus such as a copying machine, a printer, a plotter, a facsimile, or a composite machine of these, a developing device for developing an electrostatic latent image formed on a latent image carrier such as a photosensitive member is provided. The developing device is a device that develops and visualizes an electrostatic latent image on a latent image carrier with toner of a developer using, for example, a two-component developer composed of toner and carrier.
In such a developing device using a two-component developer, the developer that has completed the developing process in the developing region and has consumed the toner is collected, mixed with the toner replenished from the toner hopper, toner cartridge, etc., and stirred. And again subjected to development. Further, the developer used in the developing device having such a configuration needs to maintain a constant toner concentration and charge amount in order to obtain a stable toner image. The toner density is adjusted by the amount of toner consumed during development and the amount of replenished toner, and the charge amount is given by frictional charging during mixing of the carrier and toner. The developing device sufficiently agitates the two-component developer composed of the toner and the carrier to make the toner density distribution uniform, and to charge the toner and stabilize the toner image.

  In a general developing device, the stirring effect due to the rotation of two developer mixing agitating members (for example, screws) is exerted for a short time until the replenished toner is pumped up to the developing roller as a developer carrying member. Since the toner is dispersed and charged using the toner, the replenished toner is pumped up to the developing roller without being sufficiently dispersed, particularly when there is a large amount of toner, resulting in background contamination and toner scattering. There was a problem that.

Therefore, in order to solve such a problem, a separate stirring unit is provided at a position away from the developing unit, and the developing unit and the stirring unit are connected by a developer circulation means, and the stirring unit is used according to the state of the developer. There has been proposed a developing device that appropriately adjusts the toner concentration and the charge amount by performing agitation, and then supplies the developer to the developing unit (for example, Patent Document 1 (Japanese Patent No. 3734096), Patent Document 2). (Japanese Patent No. 3349286) and Patent Document 3 (Japanese Patent Laid-Open No. 11-143196).
Further, the present inventors have previously proposed a developing device using a stirring system having the same configuration as described above and having a higher stirring performance (Patent Document 4 (Japanese Patent Laid-Open No. 2007-193301)). Document 5 (Japanese Patent Laid-Open No. 2008-299217), Patent Document 6 (Japanese Patent Laid-Open No. 2008-3561)).

A developing device that circulates a developer using air as described in Patent Documents 1 to 6 described above has the following problems.
When the developer is continuously conveyed through the pipe using air, the main configuration of the developing device is as follows: developing unit, developer storage unit, developer supply unit, developer circulation means (transport pipe, air supply source) It is. In this configuration, the developer is transported using the air pressure (positive pressure) and the flow velocity, so that a differential pressure is generated between the air transport source and the transport destination (atmospheric pressure). Further, in this developing device, the developer sent to the developing unit is collected from the developing unit to the developer containing unit and conveyed (circulated) again, so that the developer containing unit is also at atmospheric pressure.
Therefore, in order to transport the developer to the developing unit, it is necessary to seal the developer supply unit and the developer storage unit so that the air from the air supply source does not leak into the developer storage unit. If the air leaks, the pressure for transporting the developer decreases and the transport amount cannot be secured sufficiently. In addition, when air flows back to the developer storage section (pressure is applied to the developer storage section), the developer entering the developer supply section from the developer storage section is hindered by the backflowing air, and the discharge amount decreases, Variation occurs. In addition, the internal pressure rises due to the air flowing into the developer storage unit, which may hinder the inflow of the developer recovered from the development unit.

  A rotary feeder is generally used as a supply device constituting the developer supply unit. The rotary feeder is composed of a rotor having a plurality of rotating blades and a stator covering the rotor, and is a mechanism having excellent quantitative and controllability. However, when the sealing property is insufficient, the above-described air backflow occurs. As a method for ensuring the sealing performance, there is a method in which the blades of the rotor are used as an elastic body so that the rotor bites into the stator. However, deterioration over time (rotation of the rotor and the stator, etc.) becomes remarkable, which is not practical. In particular, since the carrier constituting the developer is iron or ferrite and has high hardness, it is difficult to obtain durability by this method.

  Therefore, as a method for solving this problem, the present inventors have proposed a method for preventing the backflow of air by optimizing the gap (clearance) between the rotor and the stator in Patent Document 5. However, this method requires processing accuracy of the rotor and the stator, and increases the cost.

  In addition, the present inventors previously proposed a method for retaining the developer in the clearance between the rotor and the stator without intentionally discharging a part of the developer as a means for improving the sealing performance of the rotary feeder. (Japanese Patent Application No. 2007-272944). However, in this method, since a part of the developer is not discharged, there is a problem (side effect) that the volumetric efficiency of the rotary feeder is lowered.

  The present invention has been made in view of the above-described points, and greatly reduces the amount of air entering from the air supply source into the developer accommodating portion via the rotary feeder, and reliably develops the inside of the rotary feeder. A developing device that can discharge the developer (improves volumetric efficiency) and can stably supply the developer having an appropriate toner concentration and charge amount from the developer accommodating portion to the developing portion continuously in an amount necessary for development. It is another object of the present invention to provide an image forming apparatus including the developing device.

In order to achieve the above object, the present invention employs the following solutions.
The first solving means of the present invention includes: a developing unit that develops a latent image on a latent image carrier with a developer; a developer accommodating unit that is provided outside the developing unit and accommodates a part of the developer; A rotary feeder that is provided below the developer storage unit and discharges the developer in the developer storage unit, and a developer circulation unit that transfers the developer discharged from the rotary feeder to the development unit using air. The rotary feeder includes a stator having a cylindrical space inside, and an inflow hole (opening portion) that is provided on the upper side of the stator and into which the developer from the developer storage portion flows. And a discharge hole (opening) provided on the lower side of the stator for discharging developer, and a plurality of blades arranged in the space of the stator and extending radially from the shaft portion. A rotor, At least one of the inlet hole and the discharge hole of Rifida is characterized in that provided at a position shifted with respect to the center line of the drawn from the rotational axis vertical direction of the rotor (claim 1).

  The second solving means of the present invention comprises: a developing unit that develops a latent image on a latent image carrier with a developer; a developer accommodating unit that is provided outside the developing unit and accommodates a part of the developer; A rotary feeder that is provided below the developer storage unit and discharges the developer in the developer storage unit, and a developer circulation unit that transfers the developer discharged from the rotary feeder to the development unit using air. The rotary feeder includes a stator having a cylindrical space inside, and an inflow hole (opening portion) that is provided on the upper side of the stator and into which the developer from the developer storage portion flows. And a discharge hole (opening) provided on the lower side of the stator for discharging developer, and a plurality of blades arranged in the space of the stator and extending radially from the shaft portion. A rotor, The center point of the discharge hole of Rifida, characterized in that provided at a position shifted in the rotation direction upstream side of the rotor with respect to the center line vertical drawn from the axis of rotation of the rotor (claim 2).

  The third solving means of the present invention comprises: a developing unit that develops a latent image on a latent image carrier with a developer; a developer accommodating unit that is provided outside the developing unit and accommodates a part of the developer; A rotary feeder that is provided below the developer storage unit and discharges the developer in the developer storage unit, and a developer circulation unit that transfers the developer discharged from the rotary feeder to the development unit using air. The rotary feeder includes a stator having a cylindrical space inside, and an inflow hole (opening portion) that is provided on the upper side of the stator and into which the developer from the developer storage portion flows. And a discharge hole (opening) provided on the lower side of the stator for discharging developer, and a plurality of blades arranged in the space of the stator and extending radially from the shaft portion. A rotor, The center point of the inlet of Rifida, characterized in that provided at a position shifted downstream in the rotation direction of the rotor with respect to the center line of the vertical drawn from the rotational axis of the rotor.

  The fourth solving means of the present invention comprises: a developing unit that develops a latent image on a latent image carrier with a developer; a developer accommodating unit that is provided outside the developing unit and accommodates a part of the developer; A rotary feeder that is provided below the developer storage unit and discharges the developer in the developer storage unit, and a developer circulation unit that transfers the developer discharged from the rotary feeder to the development unit using air. The rotary feeder includes a stator having a cylindrical space inside, and an inflow hole (opening portion) that is provided on the upper side of the stator and into which the developer from the developer storage portion flows. And a discharge hole (opening) provided on the lower side of the stator for discharging developer, and a plurality of blades arranged in the space of the stator and extending radially from the shaft portion. A rotor, The center point of the inflow hole of the feeder is provided at a position shifted to the downstream side in the rotation direction of the rotor with respect to the vertical center line drawn from the rotation axis of the rotor, and the center point of the discharge hole is set to the rotor Is provided at a position shifted to the upstream side in the rotational direction of the rotor with respect to the center line in the vertical direction.

  According to a fifth solving means of the present invention, in the developing device according to any one of the first to fourth solving means, the discharge hole has a vertical apex point of the rotor of 0 degree, If the rotation direction is positive, the rotation direction is between 90 and 180 degrees (Claim 5).

According to a sixth solving means of the present invention, in the developing device according to any one of the first to fifth solving means, the width W1 of the discharge hole (the length of the chord of the stator opening) is expressed by the following equation: It is characterized by satisfying.
W1> V / t
V: Peripheral speed of rotor tip (m / s)
t: Time required for the developer near the rotor axis to reach the outside of the rotor by free fall (s)
t = √ (2 (R · r) / g)
R: Radius of rotor (m)
r: Shaft radius of the rotor (m)
g: Gravitational acceleration (m / s ^ 2)

  According to a seventh solving means of the present invention, in the developing device according to any one of the first to sixth solving means, a part of the front end side of the blade of the rotor is opposite to the rotation direction of the rotor. It has an inclination in the direction (Claim 7).

  According to an eighth aspect of the present invention, there is provided an image forming apparatus including a latent image carrier and a developing unit that develops and visualizes the latent image on the latent image carrier. (7) A developing device according to any one of (7) solving means is provided.

In the developing devices of the first and second solving means, at least the center point of the discharge hole of the rotary feeder is shifted to the upstream side in the rotation direction of the rotor with respect to the vertical center line drawn from the rotation axis of the rotor ( When the developer filled in the rotor is discharged from the discharge hole (opening) on the lower side of the stator, the developer flows from the upper developer storage portion through the inflow hole of the stator. In addition, since the angle of the rotor blades passing through the discharge hole is not always 180 degrees (vertical) or more, with the top point of the rotor (above the vertical center line drawn from the rotor rotation axis) being 0 degrees, The developer falls faster than the center point of the discharge hole (opening) is at the center of the center line, and most of the developer filled in the rotor can be discharged from the discharge hole.
Further, in the section where the rotor blades return from the discharge holes to the inflow holes, since there is no developer in the rotor, air easily escapes from the clearance between the rotor and the stator (where the rotor blades are in contact with the stator). However, if the center point of the discharge hole is on the upstream side in the rotation direction of the rotor with respect to the vertical center line drawn from the rotation axis of the rotor, the number of clearance portions in the section from the discharge hole to the inflow hole is Therefore, the air hardly leaks and the air from the air supply source of the developer circulating means can be used effectively.

  In the developing devices of the first and third solving means, at least the center point of the inflow hole of the rotary feeder is shifted downstream in the rotation direction of the rotor with respect to the vertical center line drawn from the rotation axis of the rotor ( Since it is provided at the shifted position, the developer can easily flow into the rotor of the rotary feeder from the developer storage portion. Similarly to the second solving means, when the center point of the inflow hole is on the downstream side in the rotation direction of the rotor with respect to the vertical center line drawn from the rotation axis of the rotor, the discharge hole reaches the inflow hole. In the section, since the number of clearance portions (where the rotor blades are in contact with the stator) increases, the air hardly leaks, and the air from the air supply source of the developer circulating means can be used effectively.

  In the developing devices of the first and fourth solving means, the center point of the inflow hole of the rotary feeder is shifted to the downstream side in the rotation direction of the rotor with respect to the vertical center line drawn from the rotation axis of the rotor. And the center point of the discharge hole is provided at a position shifted to the upstream side in the rotation direction of the rotor with respect to the vertical center line drawn from the rotation axis of the rotor. The effect can be further improved.

  In the developing device of the fifth solving means, in addition to the effects of any of the first to fourth solving means, the discharge hole is a vertical top point of the rotor (a vertical center line drawn from the rotation axis of the rotor). If the rotation direction of the rotor is positive, the developer is in the range of 90 to 180 degrees, so that the developer receives a downward-to-horizontal force due to the rotation of the rotor blades. It is possible to shorten the time during which is discharged from the discharge hole.

In the developing device of the sixth solving means, in addition to the effects of any of the first to fifth solving means, the width W1 of the discharge hole (the length of the chord of the stator opening) is expressed by the formula:
W1> V / t
V: Peripheral speed of rotor tip (m / s)
t: Time required for the developer near the rotor axis to reach the outside of the rotor by free fall (s)
t = √ (2 (R · r) / g)
R: Radius of rotor (m)
r: Shaft radius of the rotor (m)
g: Gravitational acceleration (m / s ^ 2)
Since the developer is filled until the developer filled in the rotor has completely dropped from the discharge hole, the developer can be reliably discharged.

  In the developing device of the seventh solving means, in addition to the effect of any of the first to sixth solving means, a part of the tip side of the rotor blade is inclined in the direction opposite to the rotation direction of the rotor. By holding the blade, it is possible to positively apply the force of the blade in the direction toward the discharge hole (downward).

  In the image forming apparatus of the eighth solving means, the developing device according to any one of the first to seventh solving means is provided as a developing means, so that the circulation, mixing, stirring, and charging of the developer are stabilized. Therefore, image quality and image density can be stabilized.

1 is a schematic perspective view of a developing device showing an embodiment of the present invention. It is a schematic sectional drawing of the image development part (developing device) of the image development apparatus shown in FIG. FIG. 2 is a schematic configuration diagram illustrating an outline of a developer accommodating portion, a rotary feeder, and a developer circulation unit of the developing device illustrated in FIG. 1. It is a schematic sectional drawing for demonstrating the behavior of the developer in the conventional rotary feeder. It is a schematic sectional drawing for demonstrating the behavior of the developer in the conventional rotary feeder. It is a schematic sectional drawing of the conventional rotary feeder. It is a schematic sectional drawing which shows an example of the rotary feeder of this invention. It is a schematic sectional drawing which shows an example of the dimension of the rotor of the rotary feeder shown in FIG. It is a schematic sectional drawing which shows another example of the rotary feeder of this invention. It is a perspective view which shows an example of the rotor of a rotary feeder. 1 is a schematic configuration diagram of an image forming apparatus showing an embodiment of the present invention.

  Hereinafter, modes for carrying out the present invention will be described in detail based on the illustrated embodiments.

[Example of developing apparatus]
1 is a schematic perspective view of a developing device showing an embodiment of the present invention, FIG. 2 is a schematic sectional view of a developing section (developing device) of the developing device shown in FIG. 1, and FIG. 3 is a development of the developing device shown in FIG. It is a schematic block diagram which shows the outline of an agent accommodating part, a rotary feeder, and a developer circulation means.
As shown in FIGS. 1 and 2, the developing unit 10 of the developing device 3 includes a casing 15 that constitutes a developing device, and two casing screws 11 having spiral fins inside the casing 15, 12 and a developing roller 13 are rotatably provided. The developing roller 13 includes a rotating cylindrical developing sleeve and a plurality of magnets (or a magnet roller having a plurality of magnetic poles magnetized) fixedly disposed inside the developing sleeve.
A two-component developer composed of toner and carrier is accommodated in the casing 15 of the developing device 3, and this developer is conveyed from the front side to the rear side in FIG. A part is sucked up and attracted to the surface of the developing roller 13 by a magnet (not shown) provided inside the developing roller 13. The developer adsorbed on the surface of the developing roller 13 is made uniform on the surface of the developing drum 13 by the doctor blade 14 and then formed on the photosensitive drum 2 by contacting the photosensitive drum 2 as a latent image carrier. The formed electrostatic latent image is visualized.

  The developed developer is transported from a hole (not shown) provided at the end of the transport screw 12 to the developer inlet 43 of the developer storage section 40 via the circulation path 30. A toner concentration detection unit (not shown) is disposed at the most downstream position in the developer conveyance direction of the conveyance screw 12, and toner is replenished from the toner cartridge 20 based on a detection signal from the toner concentration detection unit. Toner supply from the toner cartridge 20 is performed by rotating a conveyance member (a coil, a shaftless screw, etc.) (not shown) provided in the toner supply path 22 by the motor 21. Toner replenishment is performed in the developer circulation path at a position immediately before the developer storage section 40, and the developer stored in the developer storage section 40 is mixed with the replenished toner to obtain an appropriate toner concentration and charge amount. A developer having is formed.

  As shown in FIGS. 2 and 3, the developer in the developer accommodating portion 40 flows into the inflow hole (the cylindrical shape of the stator 55) of the rotary feeder 50 that communicates with the discharge port disposed in the lower portion of the developer accommodating portion 40. It is carried into the rotary feeder 50 via an upper opening 56) communicating with the space. The developer transported into the rotary feeder 50 is transported downward when the rotor 51 provided in the stator 55 constituting the rotary feeder 50 is rotated by the motor 53, and the developer 55 discharge holes (stator 55 (Opening on the lower side communicating with the cylindrical space) 57) is discharged to the joint conduit 52. An air pump 60 that is an air supply source is connected to one side of the joint pipe line 52 via an air supply path 31, and a circulation path to the developing unit 10 is provided on the other side of the joint pipe line 52. A transport pipe 32 is connected. That is, as the developer circulating means, an air pump 60 is used as an air supply source, the air pump 60 and the joint pipeline 52 are connected by the air supply passage 31, and the joint pipeline is connected from the discharge hole 57 of the stator 55 of the rotary feeder 50. The developer that has fallen to 52 is transported to the developing unit (developing device) 10 through the transport pipe 32 serving as a circulation path by the air supplied from the air pump 60, and is supplied again into the casing 15 of the developing unit (developing device) 10. Is done.

  Next, the developer container 40 and the rotary feeder 50 will be described in more detail. FIG. 3 is a cross-sectional view schematically showing the developer accommodating portion, the rotary feeder, and the developer circulating means when cut along a plane perpendicular to the rotation axis of the rotor 51 of the rotary feeder 50. As shown in FIG. The developer container 40 includes a stirring screw 41 and a stirring blade 42. The stirring blade 42 is a plate-like member that is rotated by a motor 45, and a plurality of lattice-like spaces are provided as shown in the figure. The developer passes through the lattice-like space by the rotation of the stirring blade 42, whereby the developer is stirred and the replenished toner is dispersed in the developer. The stirring screw 41 rotates in a direction to move the developer upward, and the motor 45 is a driving source, like the stirring blade 42. The developer near the center is lifted upward by the stirring screw 41, and the developer enters the lower portion of the stirring screw 41 by the rotation of the stirring blade 42. In this way, the developer is sheared by the stirring blade 42 and the whole moves in a convection so that the toner is more quickly dispersed in the developer. The developer stirred in the developer container 40 in this way enters the rotary feeder 50 through the inflow hole 56 of the stator 55.

  The rotary feeder 50 includes a stator 55 having a cylindrical space inside, an inflow hole 56 that is an opening provided on the upper side of the stator and into which developer from the developer storage portion 40 flows, A discharge hole 57 which is an opening provided on the lower side and discharges the developer, and a plurality of blades 51b arranged in the space of the stator 55 and extending radially from the shaft portion (rotating shaft) 51a as shown in FIG. And a rotor 51 rotatably supported by the motor. As shown in FIG. 1, a rotor 51 of the rotary feeder 50 is rotatably supported by a rotating shaft 51a on a side wall of a stator 55, and one side of the rotating shaft is connected to a motor 53. In FIG. 53 is rotated clockwise about the rotation axis. In FIG. 3, the center point of the opening of the inflow hole 56 and the discharge hole 57 of the rotary feeder 50 is the upstream side in the rotation direction of the rotor 51 with respect to the vertical center line c drawn from the rotation axis of the rotor 51. Alternatively, it is provided at a position shifted (shifted) downstream. That is, in the example of FIG. 3, the center point of the opening portion of the inflow hole 56 of the rotary feeder 50 is shifted to the downstream side in the rotation direction of the rotor 51 with respect to the vertical center line c drawn from the rotation axis of the rotor 51. The center point of the opening portion of the discharge hole 57 is shifted to the upstream side in the rotation direction of the rotor 51 with respect to the vertical center line c drawn from the rotation axis of the rotor 51. It is provided at the (shifted) position.

Next, the rotary feeder 50 that is a feature of the present invention will be described in more detail.
FIG. 4 is a schematic cross-sectional view (cross-sectional view cut along a plane perpendicular to the rotation axis of the rotor 51) for explaining the behavior of the developer in the conventional rotary feeder exemplified for comparison. As shown in FIG. 4, an inflow hole 56 that is an opening provided on the upper side of the stator 55 (a portion surrounded by a broken line on the upper side in the drawing) and an opening provided on the lower side of the stator 55 (see FIG. 4). When the discharge hole 57, which is the part surrounded by the broken line on the lower side in the middle, is at the center of the vertical center line drawn from the rotation axis of the rotor 51, as shown in FIG. The developer is filled from the inflow hole 56 to the discharge hole 57, and there is no developer from the downstream side of the discharge hole 57 to the inflow hole 56. However, in this case, as described in “Problem to be Solved by the Invention”, since there is a slight gap between the blades of the rotor 51 and the stator 55, a part of the air (air) from the air pump 60 is present. The portion passes through this gap and flows into the developer storage portion 40. At this time, the right side in the drawing has a relatively high sealing property because the developer exists in the gap, but the left side has no developer, so air easily passes therethrough. Become.

In order to prevent this air leakage, it is preferable to make the gap (clearance) between the blades of the rotor 51 and the stator 55 as small as possible, but there is a limit in consideration of dimensional accuracy. In addition, this method requires processing accuracy of the rotor and the stator, and increases the cost.
Another method is to increase the number of blades of the rotor 51. By increasing the number of blades of the rotor 51, the proximity of the blades and the stator 55 increases, so that the air resistance increases and leakage is increased. Reduction (high sealing performance) can be achieved. However, if the number of blades of the rotor 51 is increased, the amount of developer filling in the rotor 51 is reduced by the thickness of the blades. To transport the same amount of developer, the outer diameter of the rotor 51 is reduced. There is a problem that the rotary feeder 50 needs to be enlarged and the rotary feeder 50 becomes larger.

  Further, as described in “Problems to be Solved by the Invention”, the present inventors intentionally remove a part of the developer as a means for improving the sealing performance of the rotary feeder 50 as shown in FIG. A method has been proposed in which the developer is retained in the clearance between the rotor 51 and the stator 55 without discharging. However, in this method, since a part of the developer is not discharged, there is a problem (side effect) that the volumetric efficiency of the rotary feeder 50 is lowered.

  Therefore, in the present invention, in order to obtain the same effect as increasing the number of blades without increasing the number of blades of the rotor 51, at least one of the inflow hole 56 and the discharge hole 57 of the rotary feeder 50 is provided with the rotor 51. It is provided at a position shifted with respect to the vertical center line drawn from the rotation axis. For example, in the embodiment of FIG. 3, the center point of the opening of the inflow hole 56 of the rotary feeder 50 is shifted downstream in the rotational direction of the rotor 51 with respect to the vertical center line c drawn from the rotational axis of the rotor 51. The central point of the opening of the discharge hole 57 is provided at a position shifted to the upstream side in the rotational direction of the rotor 51 with respect to the vertical center line c drawn from the rotational axis of the rotor 51. ing.

  In the embodiment of FIG. 3, the number of blades is eight, and the number of adjacent portions of the rotor 51 and the stator 55 in the portion (left side of the drawing) that is not filled with the developer during rotation is as shown in FIG. In the case of the configuration, there are 3 or 4 places. Therefore, in the present invention, as shown in FIG. 3, the center points of the openings of the discharge hole 57 and the inflow hole 56 are shifted to the right with respect to the vertical center line c drawn from the rotation axis of the rotor 51. As a result, the number of adjacent portions on the left side where air easily leaks increases to four or five, and air leakage from the developer discharge side to the inflow side of the rotary feeder 50 is reduced. For this reason, it becomes difficult for air to leak to the developer accommodating portion side, and the air from the air supply source (air pump) 60 of the developer circulating means can be used effectively.

Next, the effect of shifting the discharge hole 57 of the rotary feeder 50 to the upstream side in the rotation direction of the rotor 51 will be described in detail with reference to FIGS.
FIG. 6 is a schematic cross-sectional view of a conventional rotary feeder 50 (cross-sectional view cut along a plane perpendicular to the rotation axis of the rotor 51), with respect to a vertical center line c drawn from the rotation axis of the rotor 51. This is an example in which the center points of the openings of the discharge holes 57 (portions surrounded by a broken line on the lower side in the drawing) coincide with each other. That is, in FIG. 6, the center point of the opening of the discharge hole 57 with respect to the center line c in the vertical direction drawn from the rotation axis of the rotor 51 when cut along a plane perpendicular to the rotation axis of the rotor 51. (The center point between both ends a2 and b2 of the opening) coincides.
On the other hand, FIG. 7 is a schematic cross-sectional view of the rotary feeder 50 of the present invention (a cross-sectional view cut along a plane perpendicular to the rotation axis of the rotor 51), and shows a vertical direction drawn from the rotation axis of the rotor 51. With respect to the center line c, the center point of the opening of the discharge hole 57 (the portion surrounded by the broken line on the lower side in the figure) is shifted upstream in the rotational direction of the rotor 51 (clockwise direction indicated by the arrow in the figure). It is an example provided at the position. That is, in FIG. 7, the center point of the opening of the discharge hole 57 with respect to the center line c in the vertical direction drawn from the rotation axis of the rotor 51 when cut along a plane perpendicular to the rotation axis of the rotor 51. (A center point between both ends a1 and b1 of the opening) is provided at a position shifted to the upstream side in the rotation direction of the rotor 51 (clockwise direction indicated by an arrow in the figure).
In FIG. 7, both end portions a <b> 1, b <b> 1 of the opening of the discharge hole 57 are located on the upstream side in the rotation direction of the rotor 51 from the vertical center line c drawn from the rotation axis of the rotor 51. When the top point in the vertical direction of the rotor 51 (above the center line c in the vertical direction drawn from the rotation axis of the rotor) is 0 degree and the rotation direction of the rotor 51 is positive, it is between 90 and 180 degrees. .
The widths W2 and W1 of the openings of the discharge holes 57 in FIGS. 6 and 7 are equal. Further, both drawings show a certain point in time when the rotor 51 rotates clockwise and the developer is conveyed (developer is not shown), and one blade 511 of the rotor 51 is connected to the discharge hole 57. This is when it reaches the start point side ends a1 and a2 of the opening.

  Next, when the rotor 51 further rotates, the developer filled between the blades 510 and 511 freely falls to the opening of the discharge hole 57. At this time, the developer exerts a tangential force by the rotational force of the blades. receive. Here, in the case of FIG. 6, after the blade 511 passes through the vertical center line c, the developer receives a horizontal to upward force as shown in FIG. On the other hand, in FIG. 7, the position (180 °) of the center line c in the vertical direction of the rotor 51 is the position of the end point side end = b1 of the opening of the discharge hole 57, so the blades at this position are vertically downward. In other words, the developer does not receive a horizontal to upward force. For this reason, since the widths W1 and W2 of the openings of the discharge holes 57 in FIGS. 6 and 7 are equal, the time for the blade 511 to pass through the openings is the same in both FIGS. The developer is more likely to fall into the discharge hole 57 at the position, and the developer is efficiently discharged.

  In FIG. 6, it is sufficient that all the developer is discharged when the blade 511 reaches the center point of the opening of the discharge hole 57. However, if the developer still remains in the rotor, Since the agent receives a force due to the rotation of the blade 511 and is prevented from dropping, the agent may not be completely discharged when the blade 511 reaches the end point side end b2 of the opening of the discharge hole 57 (state of FIG. 5). . Therefore, as shown in FIG. 5, the developer is not completely discharged, and the developer remains in the section from the discharge hole 57 to the inflow hole 56. On the other hand, as shown in FIG. 7, when the blade | wing 511 of the rotor 51 exists in the position between 90 degrees-180 degrees, since the force of the blade | wing 511 is a downward direction-a horizontal direction, it assists a free fall. Will do. Therefore, in the configuration of FIG. 7, the developer is easily discharged quickly compared to the configuration of FIG. That is, if the opening width of the discharge hole 57 is the same, the time until the developer is completely discharged is shorter at the position of the discharge hole 57 in FIG. The developer can be discharged reliably. Further, if the time for discharging is short, there is an advantage that the opening width can be narrowed.

  Further, as in the configuration example shown in FIG. 9, it is preferable that a part on the tip side of the blades of the rotor 51 has an inclination in a direction opposite to the rotation direction of the rotor. That is, as shown in FIG. 9, when the shape of the tip of the blades of the rotor 51 is inclined in the direction opposite to the rotation direction of the rotor 51, as shown by the arrow in the figure, Since a force pushing the developer in the direction is applied, the developer is more easily dropped, and the developer can be more reliably discharged from the discharge hole 57.

  In the case of the conventional configuration example of FIG. 6 as well, the developer can be taken out if the opening width W2 is increased, but if the opening width W2 is increased, the number of adjacent portions between the rotor 51 and the stator 55 described above is increased. Is reduced, the sealing effect is reduced, and the amount of air leakage to the developer accommodating portion is increased.

In the case of the configuration example of the present invention shown in FIG. 7, if the opening width W <b> 1 of the discharge hole 57 is narrowed, the effect of the seal becomes higher, but if it is too narrow, the developer is not discharged.
Therefore, the opening width W1 of the discharge hole 57 is preferably set to a condition that satisfies the following expression.
W1> V / t
V: Peripheral speed of rotor tip (m / s)
t: Time required for the developer near the rotor axis to reach the outside of the rotor by free fall (s)
t = √ (2 (R · r) / g)
R: Radius of rotor (m)
r: Shaft radius of the rotor (m)
g: Gravitational acceleration (m / s ^ 2)

  As shown in the schematic cross-sectional view of the rotary feeder shown in FIG. 8 (cross-sectional view cut along a plane perpendicular to the rotation axis of the rotor 51), the diameter of the rotor 51 is 2R, and the shaft diameter of the rotation shaft in the rotor 51 The opening width W1 is set so that the vane does not pass through the opening of the discharge hole 57 before the developer near the rotating shaft in the rotor 51 reaches the outside of the rotor due to free fall when the value is 2r. It is. If the opening width W1 is equal to or smaller than this formula, the developer may not be discharged completely. However, in reality, as described above, since the rotational force of the blades of the rotor 51 is applied, the developer can be discharged even if it is slightly narrower than W1.

  As described above, by setting the center (the center point between both end portions a1 and b1) and the width W1 of the opening of the discharge hole 57 of the rotary feeder 50, the sealing performance of the rotary feeder 50 is enhanced and the pressure is ensured. Therefore, the developer can be efficiently conveyed (improvement of energy efficiency), and the amount of air leakage into the developer storage unit 40 can be greatly reduced. Further, since the volumetric efficiency of the rotary feeder 50 is increased, an effect of increasing the developer transport efficiency (transport amount to the developing unit / size of the rotary feeder) can be obtained.

  In the above description, the center position and width of the opening of the discharge hole 57 of the rotary feeder 50 have been described. However, the opening of the inflow hole 56 of the rotary feeder 50 is perpendicular to the rotation axis of the rotor 51. You may provide in the position shifted to the downstream of the rotation direction of this rotor 51 (shifted) with respect to the centerline c. That is, as in the example of FIG. 3, the center of the opening of the inflow hole 56 of the rotary feeder 50 (the center point between both ends of the opening) when cut in a cross section perpendicular to the rotation axis of the rotor 51. Is provided at a position shifted (shifted) to the downstream side in the rotation direction of the rotor 51 with respect to the vertical center line c drawn from the rotation axis of the rotor 51, thereby further improving the sealing performance of the rotary feeder 50. The pressure is reliably transmitted to the developer, and the developer can be transported more efficiently, and the amount of air leakage to the developer storage section 40 is greatly reduced.

[Example of Image Forming Apparatus]
Next, a configuration example of an image forming apparatus equipped with the developing device of the present invention described above will be described.
FIG. 11 is a schematic configuration diagram of an image forming apparatus according to an embodiment of the present invention.
In FIG. 1, an image forming apparatus 100 includes an intermediate transfer unit 6 having an intermediate transfer belt 4 and four primary transfer rollers 5Y, 5M, 5C, and 5Bk at a substantially central portion of the apparatus main body. Image forming portions 1Y, 1M, 1C, and 1Bk corresponding to the respective colors of yellow (Y), magenta (M), cyan (C), and black (Bk) are intermediately transferred at positions facing the lower surface of the intermediate transfer belt 4. The belt 4 is disposed in parallel with the traveling direction of the belt 4. Each of the image forming units 1Y, 1M, 1C, and 1Bk has the same structure except that the color of the toner used in the image forming process is different. Each of the image forming units 1Y, 1M, 1C, and 1Bk has a photosensitive drum 2Y, 2M, 2C, and 2Bk as a latent image carrier. A charging unit (not shown), an exposure unit (not shown), developing devices 3Y, 3M, 3C, 3Bk, a cleaning unit (not shown), and the like disposed around the photosensitive drums 2Y, 2M, 2C, and 2Bk are provided.
FIG. 11 shows an example of the configuration of a color copying machine in which a document image reading unit (scanner) 80 is installed on the upper part of the image forming apparatus main body. Or a local area network (LAN) or the like, it becomes a configuration of a digital color multifunction peripheral having functions of a copying machine, a printer, and a facsimile.

  In FIG. 11, the photosensitive drums 2Y, 2M, 2C, and 2Bk of the image forming units 1Y, 1M, 1C, and 1Bk are rotationally driven in the clockwise direction in the drawing by a driving unit (not shown), and the surfaces are unified by a charging unit (not shown). After being charged in this manner, the original image read by the image reading unit 80 provided on the upper part of the apparatus body (or an external line, LAN, etc.) is exposed by a laser beam or the like emitted from an exposure unit (not shown). An electrostatic latent image is formed on the surface based on the image information input via the. The electrostatic latent images formed on the photosensitive drums 2Y, 2M, 2C, and 2Bk are developed by the developing devices 3Y, 3M, 3C, and 3Bk (the developing unit 10 of the developing device 3 in FIG. 1) to obtain desired images. The toner image is visualized as a toner image. The surface of each of the photosensitive drums 2Y, 2M, 2C, and 2Bk faces the primary transfer rollers 5Y, 5M, 5C, and 5Bk via the intermediate transfer belt 4. When the ink reaches the part, the primary transfer rollers 5Y, 5M, 5C, and 5Bk are sequentially primary transferred onto the intermediate transfer belt 4 by the action of the primary transfer rollers 5Y, 5M, 5C, and 5Bk.

  Each of the primary transfer rollers 5Y, 5M, 5C, and 5Bk forms a primary transfer nip by sandwiching the intermediate transfer belt 4 with each of the photosensitive drums 2Y, 2M, 2C, and 2Bk. A transfer bias having a polarity opposite to that of the toner is applied to the transfer rollers 5Y, 5M, 5C, and 5Bk. The intermediate transfer belt 4 travels in the direction of the arrow in FIG. 11 and sequentially passes through the primary transfer nips of the primary transfer rollers 5Y, 5M, 5C, and 5Bk, so that the photosensitive drums 2Y, 2M, 2C, and 2Bk are moved upward. Are transferred onto the intermediate transfer belt 3 so as to be primarily transferred. After the primary transfer, when the surface of each photoconductive drum 2Y, 2M, 2C, 2Bk reaches a position facing a cleaning unit (not shown), the surface of each photoconductive drum 2Y, 2M, 2C, 2Bk is caused by the action of the cleaning unit. The remaining untransferred toner is collected. After cleaning, the surface of each of the photosensitive drums 2Y, 2M, 2C, and 2Bk is initialized with a potential by a static eliminator (not shown), and a series of image forming processes is completed.

A paper feeding unit 70 is disposed in the lower part of the apparatus main body 2, and a plurality of transfer papers P that are recording media are stored in the paper feeding unit 70. The transfer paper P is separated and fed one by one by a paper feeding roller 71 and a separation member (not shown) (separation roller, separation pad, etc.) in synchronization with the start of the image forming process, and the fed transfer The paper P is temporarily stopped by the registration roller pair 72 and is fed toward the secondary transfer nip at a predetermined timing after correcting the oblique shift.
Further, the intermediate transfer belt 4 onto which the toner images of the respective colors have been transferred in the image forming process reaches the secondary transfer nip that is the position facing the secondary transfer roller 73. The color toner image formed on the intermediate transfer belt 4 is transferred onto the transfer paper P conveyed to the secondary transfer nip position.

  The transfer paper P on which the color image is transferred at the secondary transfer nip position is conveyed to the fixing device 74, and the color image transferred to the surface of the transfer paper by the heat and pressure of the heating roller and pressure roller of the fixing device 74 is transferred. It is fixed. After the fixing, the transfer paper P is discharged and stacked by a paper discharge roller pair 75 onto a paper discharge unit 76 formed on the upper surface of the apparatus main body. In this way, a series of image forming processes in the image forming apparatus is completed.

  In the above embodiment, the color copying machine (or color multifunction peripheral) is described as an example of the image forming apparatus. However, the above-described developing device of the present invention forms a monochrome image having only one image forming unit. It goes without saying that it can be applied to the device.

  In the image forming apparatus of the present invention, since the developing device 3 having the above-described configuration is provided as the developing means, the developer circulation, mixing, stirring, and charging can be stabilized, so that the image quality and image density are stabilized. be able to.

1Y, 1M, 1C, 1Bk: Image forming section 2 (2Y, 2M, 2C, 2Bk): Photosensitive drum (latent image carrier)
3 (3Y, 3M, 3C, 3Bk): developing device 4: intermediate transfer belt 5Y, 5M, 5C, 5Bk: primary transfer roller 6: intermediate transfer unit 10: developing unit (developer)
11, 12: Conveying screws 11, 12
13: Developing roller 14: Doctor blade 15: Casing 20: Toner cartridge 21: Motor 22: Toner supply path 30: Circulation path 31: Air supply path 32: Transport pipe (circulation path)
40: Developer container 41: Agitation screw 42: Agitation blade 43: Developer inlet 45: Motor 50: Rotary feeder 51: Rotor 51a: Rotating shaft 51b, 510-512: Blade 52: Joint pipeline 53: Motor 55 : Stator 56: Inflow hole 57: Discharge hole 70: Paper feed unit 71: Paper feed roller 72: Registration roller pair 73: Secondary transfer roller 74: Fixing device 75: Paper discharge roller pair 76: Paper discharge unit 80: Image reading Part 100: Image forming apparatus P: Transfer paper

Japanese Patent No. 3733496 Japanese Patent No. 3349286 JP-A-11-143196 JP 2007-193301 A JP 2008-299217 A JP 2008-3561 A

Claims (8)

A developing unit that develops the latent image on the latent image carrier with a developer, a developer storage unit that is provided outside the development unit and stores a part of the developer, and is provided below the developer storage unit. In a developing device comprising: a rotary feeder that discharges the developer in the developer storage portion; and a developer circulation means that transfers the developer discharged from the rotary feeder to the developing portion using air.
The rotary feeder includes a stator having a cylindrical space therein, an inflow hole provided on an upper side of the stator and into which developer from the developer storage portion flows, and a developer provided on a lower side of the stator. At least one of the inflow hole and the discharge hole of the rotary feeder, and a rotor rotatably supported by a discharge hole that is disposed in the space of the stator and has a plurality of blades extending radially from the shaft portion. Is provided at a position shifted with respect to the vertical center line drawn from the rotation axis of the rotor. A developing unit that develops the latent image on the latent image carrier with a developer, a developer storage unit that is provided outside the development unit and stores a part of the developer, and is provided below the developer storage unit. In a developing device comprising: a rotary feeder that discharges the developer in the developer storage portion; and a developer circulation means that transfers the developer discharged from the rotary feeder to the developing portion using air.
The rotary feeder includes a stator having a cylindrical space therein, an inflow hole provided on an upper side of the stator and into which developer from the developer storage portion flows, and a developer provided on a lower side of the stator. And a rotor rotatably supported by a shaft having a plurality of blades disposed in the space of the stator and extending radially from the shaft portion, and the center point of the discharge hole of the rotary feeder is A developing device, wherein the developing device is provided at a position shifted to the upstream side in the rotational direction of the rotor with respect to a vertical center line drawn from the rotational axis of the rotor. A developing unit that develops the latent image on the latent image carrier with a developer, a developer storage unit that is provided outside the development unit and stores a part of the developer, and is provided below the developer storage unit. In a developing device comprising: a rotary feeder that discharges the developer in the developer storage portion; and a developer circulation means that transfers the developer discharged from the rotary feeder to the developing portion using air.
The rotary feeder includes a stator having a cylindrical space therein, an inflow hole provided on an upper side of the stator and into which developer from the developer storage portion flows, and a developer provided on a lower side of the stator. And a rotor rotatably supported by a shaft having a plurality of blades disposed in the space of the stator and extending radially from the shaft portion, and the center point of the inflow hole of the rotary feeder is A developing device, wherein the developing device is provided at a position shifted to the downstream side in the rotational direction of the rotor with respect to the vertical center line drawn from the rotational axis of the rotor. A developing unit that develops the latent image on the latent image carrier with a developer, a developer storage unit that is provided outside the development unit and stores a part of the developer, and is provided below the developer storage unit. In a developing device comprising: a rotary feeder that discharges the developer in the developer storage portion; and a developer circulation means that transfers the developer discharged from the rotary feeder to the developing portion using air.
The rotary feeder includes a stator having a cylindrical space therein, an inflow hole provided on an upper side of the stator and into which developer from the developer storage portion flows, and a developer provided on a lower side of the stator. And a rotor rotatably supported by a shaft having a plurality of blades disposed in the space of the stator and extending radially from the shaft portion, and the center point of the inflow hole of the rotary feeder is Provided at a position shifted to the downstream side in the rotation direction of the rotor with respect to the vertical center line drawn from the rotation axis of the rotor, and the center point of the discharge hole is set to the vertical center line of the rotor. A developing device provided at a position shifted to the upstream side in the rotational direction of the rotor. In the developing device according to any one of claims 1 to 4,
The developing device according to claim 1, wherein the discharge hole is between 90 and 180 degrees when a top point in a vertical direction of the rotor is 0 degree and a rotation direction of the rotor is plus. In the developing device according to any one of claims 1 to 5,
The width W1 of the discharge hole (the length of the chord of the stator opening) satisfies the following expression.
W1> V / t
V: Peripheral speed of rotor tip (m / s)
t: Time required for the developer near the rotor axis to reach the outside of the rotor by free fall (s)
t = √ (2 (R · r) / g)
R: Radius of rotor (m)
r: Shaft radius of the rotor (m)
g: Gravitational acceleration (m / s ^ 2) In the developing device according to any one of claims 1 to 6,
2. A developing apparatus according to claim 1, wherein a part of the rotor blade tip side is inclined in a direction opposite to a rotation direction of the rotor. An image forming apparatus comprising a latent image carrier and developing means for developing and visualizing the latent image on the latent image carrier,
An image forming apparatus comprising the developing device according to claim 1 as the developing unit.

Images