JP4570514B2 - Development device - Google Patents

Description

  The present invention relates to a developing device mounted on an electrophotographic image forming apparatus.

  In general, an image forming apparatus using an electrophotographic system includes a photoconductor as a latent image carrier and a charging device, an exposure unit, a developing device, a transfer device, a fixing device, and the like disposed around the photoconductor. The charging device uniformly charges the surface of the photoreceptor. The exposure unit exposes the charged photoconductor surface with light according to image information to form an electrostatic latent image. The developing device supplies toner constituting the developer from the developing roller to the electrostatic latent image formed on the surface of the photoconductor to form a toner image. The transfer device applies a charge having a reverse polarity to the toner to the recording material to transfer the toner image to the recording material. The fixing device fixes the toner image on the recording material by means such as heating and pressing. In the image forming apparatus, a desired image is formed on the recording material in this way.

  When the developing operation for developing the electrostatic latent image on the photosensitive member is repeatedly executed as described above, the toner is consumed for the development, so that the toner concentration in the developer in the developing device decreases. In particular, in a two-component developer containing a toner and a carrier, when the toner in the developer is consumed, the ratio of the remaining carrier increases and the toner density decreases. If an electrostatic latent image is developed in a state where the toner concentration in the developer is reduced, the developed image may have insufficient density, and the image cannot be stably developed so that the image has a sufficient density in terms of quality. There is a problem.

  Accordingly, a developing device mounted on an electrophotographic image forming apparatus is generally provided with a toner replenishing unit that replenishes toner, and the toner replenishing unit compensates for a decrease in toner density to develop the toner. The reduction of the image density is prevented. However, the toner replenishment operation is executed based on the detection result of a toner concentration sensor or the like that measures the toner concentration of the developer contained in the developer container of the developing device. Since the actual replenishment amount may be excessive or deficient with respect to the replenishment required amount due to the local measurement value, it is difficult to always keep the toner concentration stable and constant. As a result, there is a problem that it is difficult to stabilize the density of the developed image.

  As a conventional technique for coping with such a problem, when supplying toner to the developing device, a detecting means for detecting the toner supply amount is provided, and the toner supply amount is controlled based on the detection result of the toner supply amount. It has been proposed to obtain a stable toner replenishment amount and stabilize the developed image density (see, for example, Patent Document 1).

  However, as disclosed in Patent Document 1, even if accurate toner replenishment amount control is performed based on the detection result, stabilization of the toner concentration in the developer in the developing device may be hindered. .

  Hereinafter, an example in which the stabilization of the toner concentration in the developer in the developing device is hindered through the toner replenishing operation in the conventional developing device will be described. FIG. 4 is a perspective view schematically showing the configuration of the conventional developing device 1, and FIG. 5 is a cross-sectional view showing the configuration of the toner replenishing unit 2 provided in the developing device 1. The developing device 1 supplies a toner which is a developer component to an electrostatic latent image formed on a photosensitive member which is a latent image carrier and visualizes it, and replenishes the developing unit 3 with toner. And a toner replenishing unit 2.

  The developing unit 3 includes a developing casing 4, a developing roller 5 that is rotatably provided inside the developing casing 4, a first stirring member 6, and a second stirring member 7. The developing casing 4 is a container-like member, and a developer is accommodated in the internal space thereof. The developer in the developing casing 4 circulates in the direction indicated by arrows 8a and 8b in the developing casing 4 as the first and second stirring members 6 and 7 rotate. The developer circulating in the developing casing 4 is sent to the developing roller 5 which is a developer carrier provided near one end of the developing casing 4 and is held by the developing roller 5. When the developing device 1 is mounted on the image forming apparatus, the developer held on the developing roller 5 is transferred to the photosensitive member at a position facing the developing roller 5 by the action of an electric field, and the photosensitive member is statically moved. Visualize the electrostatic latent image.

  The developer in the developing casing 4 reduces the amount of toner in the developer as the electrostatic latent image is developed by supplying toner onto the photoconductor. Therefore, the toner supply amount becomes insufficient, which leads to a decrease in image density. Accordingly, the toner is supplied from the toner supply unit 2 to the developing casing 4.

  The toner replenishing unit 2 includes a toner container 11 that stores toner, and a toner transport unit 12 that transports the toner stored in the toner container 11 in a predetermined direction. The toner conveying unit 12 includes a rotation shaft member 13 that is rotatably provided in the toner container 11 and a screw blade member 14 that is attached to the outer periphery of the rotation shaft member 13. When the rotary shaft member 13 is rotated in the direction of the arrow 15 by a rotation driving means (not shown), the screw blade member 14 that rotates together with the rotary shaft member 13 causes the toner in the toner container 11 to move in the directions of the arrows 16a and 16b. Move to transport. The toner conveyed and moved in the toner container 11 by the toner conveying means 12 is replenished to the developing casing 4 through the toner replenishing port 17 formed in the toner container 11 facing the developing unit 3. The toner replenished from the toner replenishing section 2 to the developing casing 4 is sufficiently mixed with the developer already present in the developing casing 4 by the first and second stirring members 6 and 7 and conveyed to the developing roller 5. .

  When the toner concentration in the developer accommodated in the developing casing 4 decreases, for example, a detection signal is transmitted from a toner concentration sensor, the signal is given to the control unit, and the control unit provides the toner conveying means 12 of the toner replenishing unit 2. The toner conveying means 12 is rotated by controlling the operation of the rotation driving means for driving the toner. Normally, when the toner conveying means 12 rotates, the toner in the toner container 11 is conveyed toward the toner replenishing port 17 and falls from the toner replenishing port 17 as indicated by an arrow 9 in FIG. 4 is replenished.

  However, when the toner container 11 containing the toner is transported or stored, if the toner container 11 is left for a long time in an inferior environment such as high temperature and high humidity, or left vertically with the toner replenishing port 17 down, the toner is replenished. Cross-linked toner 18 may be generated near the mouth 17. Here, the term “crosslinked toner” refers to a toner in a state in which toner that is originally a powder and agglomerate aggregates to form a bridge across the toner supply port 17. When such a crosslinked toner 18 is generated in the vicinity of the toner replenishing port 17, the movement of the toner in the toner container 11 is obstructed even if an attempt is made to convey an accurate toner replenishment amount by controlling the rotation speed of the toner conveying means 12. As a result, the toner is not smoothly discharged from the toner replenishing port 17, so that the toner amount required by the developing unit 3 cannot be replenished within the required time. In addition, since the relationship between the rotation time of the toner conveying means 12 and the remaining amount of toner in the toner container 11 is deviated, it is impossible to accurately grasp the remaining amount of toner.

  Further, although the toner conveying means 12 is conveying toner, the toner density sensor continues to output a signal of insufficient density because the toner is not replenished in the developing casing 4 to a necessary amount. 12 will continue to rotate indefinitely. If the toner conveying means 12 is continuously rotated in a state where the crosslinked toner is formed in the vicinity of the toner replenishing port 17, that is, in a state where the toner is clogged in the vicinity of the toner replenishing port 17, torque applied to the toner conveying means 12 is increased. As a result, the toner conveying means 12 is locked. As a result, there are problems such as breakage of the rotating shaft member 13 of the toner conveying means 12, gear tooth skipping, or gear tooth missing. The same problem also occurs in the motor that is the rotation driving means of the toner conveying means 12.

JP 2003-5503 A

  An object of the present invention is to provide a developing device that can stably supply a necessary amount of toner even in a state where crosslinked toner is generated, and can stabilize the density of an image to be developed. .

The present invention
In a developing device including a developing unit that supplies toner as a developer component to an electrostatic latent image formed on a latent image carrier and visualizes the toner, and a toner replenishing unit that supplies toner to the developing unit.
The toner supply unit
A toner container for containing toner;
A toner conveying means that is provided in the toner container and conveys the toner contained in the toner container to the toner replenishing port ;
A toner replenishing port formed through the toner container wall at a position facing the developing portion of the toner container in order to replenish the toner conveyed by the toner conveying means to the developing portion;
A toner shearing means that is provided in the vicinity of the toner replenishing port and imparts a shearing force to the crosslinked toner formed on the downstream side in the toner conveying direction in the toner container;
The toner conveying means includes a rotary shaft member rotatably provided in the toner container, a screw blade member attached to the outer periphery of the rotary shaft member,
A plate-like protrusion formed so as to protrude in a substantially radial direction from the rotating shaft member,
The toner shearing means includes
A member of Nema other short cylindrical shape as a coil having elasticity, is provided in the vicinity of the toner conveying direction downstream side end portion of the toner container,
The coil spring is configured such that the upstream end portion in the toner conveying direction is in contact with the plate-like protrusion of the rotating shaft member, and the cylindrical member extends in a radial direction from the cylindrical portion. The receiving protrusion is configured to hit a plate-like protrusion provided in the rotating shaft member,
The toner shearing unit is a developing device that rotates following the rotation of the screw conveying member .

  In addition, the present invention is an image forming apparatus including any one of the developing devices.

  According to the present invention, the toner replenishing portion of the developing device is provided with toner shearing means for applying a shearing force to the toner in the toner container in the vicinity of the toner replenishing port of the toner container. As a result, the toner shearing means crushes the crosslinked toner even under conditions where the crosslinked toner is generated in the toner container, so that the movement of the toner in the toner container by the toner conveying means is not hindered. Further, the toner is smoothly supplied from the toner supply port to the developing unit. Therefore, the toner replenishment amount required by the developing unit can be accurately replenished from the toner replenishing unit to the developing unit, and development can be performed so that an image having a necessary and sufficient density can be stably obtained over a long period of time. .

Also, the toner shearing means has a ring-like or cylindrical shape, by being rotatably provided, crushing the crosslinked toner is realized with a simple configuration.

Also, the toner shearing means, members having elasticity, preferably a coil spring. This allows the toner shearing means to operate more effectively for crushing the crosslinked toner.

Also, conveying means is a screw conveyor member and a screw blade member mounted on the outer periphery of the rotary shaft member and the rotation axis member provided rotatably in the toner container, the toner shearing means, the screw conveyor member Since it is configured to be driven and rotated in accordance with the rotation drive, it is not necessary to provide a rotation drive unit dedicated to the toner shearing unit, and the configuration can be simplified.

According to the present invention, an image forming apparatus, since includes a pre-Symbol developing device, it is possible to stably form an image having a necessary and sufficient concentration over a long period of time.

  FIG. 1 is a cross-sectional view showing a simplified configuration of a toner replenishing unit 21 provided in the developing device according to the first embodiment of the present invention, and FIG. 2 is a cross-sectional view taken along the section line II-II in FIG. It is. The developing device of the present invention includes a developing unit and a toner replenishing unit 21, and the overall configuration thereof is the same as that of the developing device 1 shown in FIG. .

  The toner replenishing unit 21 provided in the developing device of the present embodiment includes a toner container 22 that stores toner, and an arrow 23 that is provided in the toner container 22 and has a predetermined direction for toner stored in the toner container 22. A toner conveying means 24 that conveys the toner container 22 in the direction shown, and a toner container wall 22a that penetrates the toner container wall 22a at a position facing the developing portion of the toner container 22 in order to supply the toner conveyed by the toner conveying means 24 to the developing portion. The toner supply port 25 includes a toner supply port 25 and a toner shearing unit 26 that is provided in the vicinity of the toner supply port 25 and applies a shearing force to the toner in the toner container 22.

  The toner container 22 is a hollow container-like member made of, for example, a synthetic resin. The shape of the toner container 22 is not particularly limited, but the appearance is formed in a columnar or prismatic shape. In the present embodiment, the toner container 22 is formed in a bottomed cylindrical shape, that is, a columnar appearance.

  The toner conveying means 24 includes a rotating shaft member 31 that is inserted in the interior space of the toner container 22 in the length direction and is rotatably provided in the toner container 22, and a screw blade member 32 that is attached to the outer periphery of the rotating shaft member 31. It is a screw conveyance member provided. Hereinafter, the toner transport unit 24 may be referred to as a screw transport member 24.

  The rotating shaft member 31 is a straight rod-like member, and is inserted through the inner space of the toner container 22 in the length direction as described above, and both end portions thereof are rotatably supported by the toner container 22. A plurality of screw blade members 32 are mounted on the rotary shaft member 31 in a predetermined direction at predetermined intervals. The screw conveying member 24 is rotated in the direction of the arrow 33 by receiving a rotational driving force from a driving source (not shown) connected to one end of the rotating shaft member 31 outside the toner container 22.

  As the screw conveying member 24 rotates in the direction of the arrow 33, the toner in the toner container 22 is conveyed in the direction of the arrow 23. A plate-like protrusion 34 is formed on the rotating shaft member 31 of the screw conveying member 24 so as to protrude from the rotating shaft member 31 in a substantially radial direction in the vicinity of the downstream end of the toner conveying direction. Therefore, the protrusion 34 rotates in the direction of the arrow 33 around the rotation axis along with the rotation operation of the rotation shaft member 31. The screw conveying member 24 is made of hard synthetic resin, metal, or the like, and the rotating shaft member 31, the screw blade member 32, and the protruding portion 34 are configured as an integral member.

  In the present embodiment, the toner shearing means 26 is made of metal, has a short cylindrical shape, and is formed with a plate-shaped receiving projection 35 extending inward in the radial direction from the cylindrical portion. The length of the receiving projection 35 extending inward in the radial direction is such that a portion of the screw conveying member 24 that overlaps with the projection 34 formed to extend outward in the radial direction from the rotary shaft member 31 is formed. In other words, the rotating projection 34 is set to contact the receiving projection 35.

  Since the toner shearing unit 26 is provided in the vicinity of the most downstream end portion in the toner transport direction in the toner container 22 without being restrained, the screw transport member 24 rotates in the direction of the arrow 33 as the screw transport member 24 rotates. The receiving projections 35 are pushed by the projections 34 of 24 and rotate in the direction of the arrow 36 which is the same direction as the screw conveying member 24. Thus, since the toner shearing means 26 is configured to be driven and rotated in accordance with the rotational drive of the screw conveying member 24, it is not necessary to provide a rotation driving means dedicated to the toner shearing means 26, and the configuration can be simplified. it can.

  An example of the dimensions and arrangement of the toner shearing means 26 is as follows. For example, when the inner diameter of the toner container 22 is 16 mm, the outer diameter of the cylinder of the toner shearing means 26 is formed to be 15.5 mm, and the thickness thereof is set to 0.1 mm. The end of the cylinder in the length direction is arranged at the same position as the edge of the toner replenishing port 25 or a position where it protrudes to the toner replenishing port 25 to the extent of 1 mm or less and slightly overlaps. Such toner shearing means 26 is rotated together with the screw conveying member 24 at a speed of about 16 rpm.

  Hereinafter, the crushing action of the crosslinked toner by the toner shearing means 26 will be described. When the crosslinked toner is formed on the most downstream side in the toner conveyance direction in the toner container 22, the toner shearing unit 26 rotates together with the screw conveyance member 24. A force to move in the direction of the arrow 36 works together with the inner wall of the rotating toner shearing means 26, and the rotational force by the screw blade member 32 hardly acts on the bridging toner around the rotating shaft member 31.

  Accordingly, a shearing force acts on the crosslinked toner in the direction around the rotation axis between the periphery of the rotating shaft member 31 and the tip portion of the screw blade member 32, causing the crosslinked toner to crack, thereby causing the crosslinked toner. Can be crushed. As a result, the cross-linked toner that exists in the vicinity of the toner supply port 25 and hinders smooth discharge of the toner from the toner supply port 25 is easily discharged as the crushed toner 37 from the toner supply port 25. Thus, the flow of replenishment becomes smooth without being obstructed, and an accurate amount of toner can be replenished.

  FIG. 3 is a cross-sectional view showing a simplified configuration of the toner replenishing unit 41 provided in the developing device according to the second embodiment of the present invention. The toner replenishing unit 41 provided in the developing device of the present embodiment is similar to the toner replenishing unit 21 provided in the developing device of the first embodiment, and corresponding portions are denoted by the same reference numerals and description thereof is omitted.

  The toner replenishing portion 41 is characterized in that the toner shearing means 42 is formed of a coil spring having elasticity. The coil spring 42 serving as the toner shearing means 42 has a shape in which a ring is spirally continuous. For example, when the inner diameter of the toner container 22 is 16 mm, the outer diameter is 15 mm and the number of turns is about 1 to 3 turns. Is done. The coil spring 42 is not particularly limited in material, but is preferably a spring steel material defined in JIS-G4801, a stainless steel wire for springs defined in JIS-G4314, or a copper alloy wire for springs. Used.

  The coil spring 42 is formed so that the end on the upstream side in the toner conveyance direction is bent inward in the radial direction, and the bent portion 43 hits the protruding portion 34 of the screw conveying member 24. That is, the bent portion 43 acts in the same manner as the receiving projection 35 of the toner shearing means 26 of the first embodiment. Therefore, when the screw conveying member 24 rotates in the direction of the arrow 33, the bent portion 43 of the coil spring 42 is pushed by the projection 34, and the coil spring 42 rotates.

  The coil spring 42 can shear the cross-linked toner by rotating together with the screw conveying member 24. Therefore, the cross-linked toner is crushed and easily discharged from the toner supply port 25, and the toner is smoothly supplied to the developing unit. Make it possible.

  Furthermore, the coil spring 42 can be elastically compressed / expanded and deformed in the direction of the arrow 44 that is the winding axis direction of the coil. Since the coil spring 42 is provided so that the end on the downstream side in the toner conveyance direction is in contact with the bottom wall 22b that forms the bottom portion of the toner container 22, the toner conveyed by the screw conveyance member 24 bottoms the coil spring 42. It acts to press toward the wall 22b and elastically compresses / extends in accordance with the amount of pressing force by the toner. Accordingly, the coil spring 42 can apply a shearing force not only to the circumferential direction around the winding axis but also to the direction of the arrow 44 that is the winding axis direction with respect to the crosslinked toner. The toner can be reliably crushed and discharged from the toner supply port 25.

  An image forming apparatus mounted for using the developing device of the first embodiment or the developing device of the second embodiment of the present invention for developing an electrostatic latent image formed on the surface of a photoreceptor, for example, electrophotographic copying Machines, printers, facsimile machines, and the like constitute other embodiments of the present invention.

FIG. 3 is a cross-sectional view showing a simplified configuration of a toner replenishing unit 21 provided in the developing device according to the first embodiment of the present invention. It is sectional drawing seen from the cut surface line II-II of FIG. It is sectional drawing which simplifies and shows the structure of the toner replenishment part 41 with which the developing device which is 2nd Embodiment of this invention is equipped. It is a perspective view which simplifies and shows the structure of the conventional developing device. 3 is a cross-sectional view illustrating a configuration of a toner replenishing unit 2 provided in the developing device 1. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Developing device 2,21,41 Toner replenishment part 3 Developing part 11,22 Toner container 12,24 Toner conveyance means 17,25 Toner replenishment port 18 Cross-linked toner 26 Toner shearing means 34 Protrusion 35 Receiving protrusion 42 Coil spring 43 Folding Music part

Claims (2)

In a developing device including a developing unit that supplies toner as a developer component to an electrostatic latent image formed on a latent image carrier and visualizes the toner, and a toner replenishing unit that supplies toner to the developing unit.
The toner supply unit
A toner container for containing toner;
A toner conveying means that is provided in the toner container and conveys the toner contained in the toner container to the toner replenishing port ;
A toner replenishing port formed through the toner container wall at a position facing the developing portion of the toner container in order to replenish the toner conveyed by the toner conveying means to the developing portion;
A toner shearing means that is provided in the vicinity of the toner replenishing port and imparts a shearing force to the crosslinked toner formed on the downstream side in the toner conveying direction in the toner container;
The toner conveying means includes a rotary shaft member rotatably provided in the toner container, a screw blade member attached to the outer periphery of the rotary shaft member,
A plate-like protrusion formed so as to protrude in a substantially radial direction from the rotating shaft member,
The toner shearing means includes
A member of Nema other short cylindrical shape as a coil having elasticity, is provided in the vicinity of the toner conveying direction downstream side end portion of the toner container,
The coil spring is configured such that the upstream end portion in the toner conveying direction is in contact with the plate-like protrusion of the rotating shaft member,
The cylindrical member is configured such that a plate-like receiving protrusion extending radially inward from the cylindrical portion hits a plate-like protrusion provided in the rotary shaft member,
The developing device according to claim 1, wherein the toner shearing means is driven to rotate in accordance with the rotational driving of the screw conveying member . An image forming apparatus comprising the developing device according to claim 1 .

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