JP5131049B2 - Developing device and image forming apparatus - Google Patents

Description

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

  An electrophotographic image forming apparatus includes an electrostatic latent image carrier that carries an electrostatic latent image on an outer peripheral surface, and a developing device that develops toner by attaching toner to the electrostatic latent image on the electrostatic latent image carrier And have.

  As a developing device, a type using a so-called two-component developer composed of a non-magnetic toner and a magnetic carrier has been proposed. When a two-component developer is used, only toner is consumed during development, so that new toner is replenished to the developer accommodating portion as the toner is consumed. The newly replenished toner is charged to a predetermined polarity by frictional contact with the carrier. In order to promote such frictional charging of the toner, the developing device is provided with a conveying member that conveys the toner and the carrier in a predetermined direction while stirring the developer and the carrier.

  Generally, a conveying screw provided with conveying blades is used as the conveying member. In this case, the developer in the developer container is transported and stirred by being pushed in a predetermined transport direction by the transport blades as the transport screw rotates. In addition, the developing device provided with such a conveying screw is disclosed in many documents such as Patent Document 1.

JP 2006-251158 A

  However, in the configuration in which the developer is conveyed by being pushed in by the conveyance blade as described above, the toner and the carrier are not sufficiently stirred, and the developer is subjected to strong stress or the developer is pressed and hardened. is there. As a result, the developer is deteriorated or aggregated, and the image quality may be lowered.

  Therefore, the present invention provides a developing device that can suppress deterioration and aggregation of the developer and can maintain good image quality over a long period of time, and an image forming apparatus including the developing device. With the goal.

In order to solve the above problems, a developing device according to the present invention provides:
A housing for containing the developer;
A transport member that transports the developer in a predetermined transport direction that is horizontal or substantially horizontal in the housing,
Conveying member, possess a cylindrical portion extending in the conveying direction, and a stirring means for stirring the developer in the manner inside the cylindrical portion Komu mix the developer and air,
The stirring means includes
A rib-like protrusion projecting in the form of a strip on the inner peripheral surface of the tubular part, and
The developer inside the cylindrical part can be stirred by rotating in the circumferential direction of the cylindrical part as the cylindrical part rotates, and
The developer in a state where the developer is lifted by the protrusion as the cylindrical portion rotates is provided at an angle so as to flow down from the upstream side to the downstream side in the transport direction.
It is characterized by that.

  Here, the “substantially horizontal direction” refers to a direction inclined to some extent with respect to the horizontal direction, and includes, for example, a direction inclined about 30 degrees with respect to the horizontal direction.

  An image forming apparatus according to the present invention includes the above-described developing device.

  According to the present invention, since the developer is agitated by mixing the developer and air inside the cylindrical portion provided in the conveying member, compared to the conventional case where the developer is agitated by a screw. The stirrability can be greatly improved. Further, according to the present invention, when the developer is agitated, the developer is not subjected to a large stress or pressed, so that aggregation and deterioration of the developer can be suppressed, and the developer can be maintained over a long period of time. Good image quality can be maintained.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described with reference to the accompanying drawings. In the following description, terms indicating a specific direction (for example, “up”, “down”, “left”, “right”, and other terms including them, “clockwise direction”, “counterclockwise” ”) Is used to facilitate understanding of the invention with reference to the drawings, and the present invention should not be construed as being limited by the meaning of these terms. In the image forming apparatus described below, the same reference numerals are used for the same or similar components.

  FIG. 1 shows a schematic configuration of an image forming apparatus 2 according to an embodiment of the present invention. However, in order to facilitate understanding of the invention by clarifying the characteristic portions of the present invention, the housing of the image forming apparatus is omitted from the drawings.

  The image forming apparatus 2 is an electrophotographic image forming apparatus such as a copying machine, a printer, a facsimile machine, or a multi-function machine having a combination of these functions. At present, various types of electrophotographic image forming apparatuses have been proposed, but the illustrated image forming apparatus is a monochrome image forming apparatus having only one developing device. However, the present invention is not only applied to this type of image forming apparatus, but is equally applicable to other types of image forming apparatuses, for example, so-called tandem type or four-cycle type color image forming apparatuses.

  The image forming apparatus 2 includes a cylindrical photosensitive member 4 as an electrostatic latent image carrier. Around the photoreceptor 4, a charger 6, an exposure device 8, a developing device 30, a transfer roller 12, and a cleaning member 14 are arranged in order along the rotation direction (clockwise direction in the drawing). A contact portion (nip portion) between the photosensitive member 4 and the transfer roller 12 forms a transfer region 22.

  In the embodiment, a charging roller is used as the charger 6. However, as the charger 6, a charger other than the charging roller may be used. For example, a scorotron charger may be used. In the embodiment, a plate-like blade is used as the cleaning member 14, and one end side thereof is in contact with the outer peripheral surface of the photoreceptor 4. However, the cleaning member 14 is not limited to a blade, and other cleaning members (for example, a fixed brush, a rotating brush, and a roller) can be used.

  A conveyance path 26 through which a recording sheet such as a sheet is conveyed passes through a nip portion 20 of the paper feed roller pair 16, a transfer region 22, and a nip portion 24 of the fixing roller pair 18 from a paper feeding device (not shown). It extends to the paper output section.

  An example of the image forming operation will be briefly described. First, the outer peripheral surface of the photosensitive member 4 that is rotationally driven at a predetermined peripheral speed is charged by the charger 6. Next, light corresponding to image information is projected from the exposure device 8 onto the outer peripheral surface of the charged photoconductor 4 to form an electrostatic latent image. Subsequently, the electrostatic latent image is made visible by the developer toner supplied from the developing device 30. The toner image formed on the photoconductor 4 in this way reaches the transfer area 22 by the rotation of the photoconductor 4.

  On the other hand, in accordance with the timing, the recording sheet accommodated in the sheet feeding device is sent to the conveyance path 26 by the rotation of the sheet feeding roller 16 and is conveyed to the transfer region 22. In the transfer area 22, the toner image on the photoreceptor 4 is transferred to the recording sheet. The recording sheet to which the toner image has been transferred is conveyed further downstream of the conveying path 26, and after the toner image is fixed on the recording sheet by the fixing roller 18, it is sent out to the paper discharge unit.

  When the toner remaining on the photosensitive member 4 without being transferred to the recording sheet reaches the contact portion between the photosensitive member 4 and the cleaning member 14, the toner is scraped off by the cleaning member 14, and from the outer peripheral surface of the photosensitive member 4. Removed.

  Next, the configuration of the developing device 30 will be described in detail.

  As shown in FIG. 2, the developing device 30 includes a housing 32 that stores a developer. In this embodiment, a two-component developer containing a nonmagnetic toner and a magnetic carrier is used as the developer. The housing 32 is provided with an opening 33 opened toward the photosensitive member 4, and a developing roller 34 is provided in a space near the opening 33.

  The developing roller 34 is disposed in parallel to the photosensitive member 4 and opposed to the outer peripheral surface of the photosensitive member 4 via a predetermined developing gap. The developing roller 34 includes a columnar fixed magnet 36 and a rotatable cylindrical sleeve (developer carrier) 38 provided so as to surround the fixed magnet 36. The fixed magnet 36 includes a magnetic pole N1, a magnetic pole S2, a magnetic pole N2, a magnetic pole N3, and a magnetic pole S1 in order along the rotation direction of the sleeve 38. The magnetic pole N 1 is disposed at a position facing the photoconductor 4, and the magnetic pole N 2 and the magnetic pole N 3 are disposed at positions facing the internal space of the housing 32. The sleeve 38 rotates in a so-called counter direction (clockwise direction in the drawing) with respect to the photosensitive member 4.

  The sleeve 38 is connected to a power source (not shown) as a bias applying device, and a predetermined developing bias is applied to the sleeve 38 by turning on the power source. For example, the developing bias is constituted by a voltage obtained by superimposing an AC voltage and a DC voltage. In this case, an oscillating electric field is formed between the sleeve 38 and the photosensitive member 4.

  On the side of the sleeve 38, for example, a plate-like developer regulating member 39 fixed to the housing 32 is disposed so as to oppose a predetermined regulating gap.

  As shown in FIGS. 2 and 3, in the space in the housing 32 behind the developing roller 34, the first transport chamber in which the developer is transported in the horizontal first transport direction by the first transport member 40. 62 and a second transport chamber 64 in which the developer is transported in the second transport direction opposite to the first transport direction by the second transport member 42. However, the first transport direction and the second transport direction are not necessarily horizontal, and may be directions inclined to some extent (for example, about 30 degrees) with respect to the horizontal direction.

  In the first transfer chamber 62, the first transfer member 40 is rotatably arranged, and in the second transfer chamber 64, the second transfer member 42 is rotatably arranged. The 1st conveyance member 40 consists of a structure provided with the cylindrical part 44 as mentioned later, and the 2nd conveyance member 42 consists of a screw provided with the spiral blade 58 similarly to the conventional conveyance member. A specific configuration of the first transport member 40 will be described later.

  A partition 66 that rises from the bottom surface of the housing 32 is provided between the first transfer chamber 62 and the second transfer chamber 64. The height of the partition portion 66 is the same as or lower than the rotation shafts 51 and 55 of the first transport member 40.

  As shown in FIG. 3, in the vicinity of both ends of the first transfer chamber 62 and the second transfer chamber 64, the partition 66 is removed to form communication passages 68 and 70. The developer that has reached the downstream end in the first transport direction (left direction in the figure) is sent to the second transport chamber 64 via the communication passage 68, and the second transport direction of the second transport chamber 64 (Right direction in the figure) The developer that has reached the downstream end is sent into the first transfer chamber 62 through the communication passage 70. As a result, the developer is circulated inside the housing 32. For example, in the first transfer chamber 62 in the internal space of the housing 32, a toner concentration sensor (not shown) is attached to the housing 32.

  Returning to FIG. 2, a toner hopper 80 containing toner is provided above the first transfer chamber 62. The toner hopper 80 is connected to the housing 32 via a connecting portion 82. The toner accommodated in the toner hopper 80 is appropriately replenished into the housing 32 based on the toner concentration (mixing ratio of toner and carrier) of the developer in the housing 32 detected by the toner concentration sensor. Thereby, the toner concentration of the developer in the housing 32 is kept constant. As shown in FIG. 3, the toner replenishing port 60 of the housing 32 is arranged at the most upstream portion in the first transport direction in the first transport chamber 62.

  The operation of the developing device 30 configured as described above will be described. As shown in FIG. 2, during image formation, the sleeve 38 of the developing roller 34 rotates in the clockwise direction in the drawing based on the driving of a motor (not shown). Moreover, the 1st conveyance member 40 and the 2nd conveyance member 42 rotate in the counterclockwise direction in the figure. Thereby, the developer in the housing 32 is agitated while being circulated and conveyed through the first conveyance chamber 62 and the second conveyance chamber 64. As a result, the toner and the carrier contained in the developer come into frictional contact with each other and are charged with opposite polarities. Specifically, for example, the carrier is charged with positive polarity and the toner is charged with negative polarity. In addition, toner appropriately supplied from the toner hopper 80 is mixed with the existing developer in the housing 32.

  The developer frictionally charged as described above is supplied to the developing roller 34 in the process of being conveyed through the second conveying chamber 64 by the second conveying member 42 and is carried on the outer peripheral surface of the developing roller 34. Specifically, the developer is attracted to the outer peripheral surface of the sleeve 38 by the magnetic force of the fixed magnet 36 of the developing roller 34. In this way, the developer carried on the sleeve 38 of the developing roller 34 is conveyed in the clockwise direction in the drawing based on the rotation of the sleeve 38. When the developer on the sleeve 38 is conveyed to a region (regulation region) facing the regulating member 39, the layer thickness of the developer passing through the regulation region is regulated to a predetermined amount. When the developer that has passed through the regulation region reaches the region (development region) facing the photosensitive member 4 based on the rotation of the sleeve 38, due to the presence of an electric field formed between the sleeve 38 and the photosensitive member 4, The toner adhering to the carrier is electrically supplied to the electrostatic latent image portion on the photoreceptor 4. As a result, the electrostatic latent image on the photoconductor 4 becomes obvious, and a toner image is formed on the photoconductor 4.

  Hereinafter, the configuration of the first transport member 40 will be specifically described.

  As shown in FIG. 3, the first transport member 40 includes, for example, a cylindrical tubular portion 44 that extends in the first transport direction. The developer conveyed by the first conveying member 40 is passed through the inner space of the cylindrical portion 44 so that the developer is conveyed in the first conveying direction while being stirred in the cylindrical portion 44. It is.

  In the embodiment, screws 50 and 54 are connected to both ends in the length direction of the cylindrical portion 44. Specifically, in the first transport direction, the first screw 50 is connected to the upstream end of the cylindrical portion 44, and the second screw 54 is connected to the downstream end of the cylindrical portion 44. Yes. The screws 50 and 54 are provided so as to be rotatable about rotation shafts 51 and 55 extending in the first conveying direction, respectively, and the cylindrical portion 44 is also rotated together with the screws 50 and 54. In the present invention, it is not always necessary to provide the screws 50 and 54 on the first conveying member 40, but by providing the first screw 50, the developer can be efficiently guided into the cylindrical portion 44. By providing the second screw 54, the developer can be efficiently discharged from the inside of the cylindrical portion 44.

  As shown in FIG. 3, the first screw 50 is disposed so as to pass through the vicinity of the toner supply port 60. Further, the cylindrical portion 44 is disposed on the downstream side of the toner supply port 60 in the first transport direction. Therefore, the toner replenished into the housing 32 from the toner replenishing port 60 is first transported in the first transport direction by the first screw 50 and reliably guided into the cylindrical portion 44. Therefore, the newly charged uncharged toner and the existing developer can be reliably stirred in the cylindrical portion 44.

  FIG. 5 is a cross-sectional view showing an upstream end portion of the cylindrical portion 44 in the first transport direction. As shown in FIG. 5, the rotating shaft 51 of the first screw 50 is connected to the upstream end of the cylindrical portion 44 so as to coincide with the radial center of the cylindrical portion 44. Although the structure which connects the 1st screw 50 to the cylindrical part 44 is not specifically limited, In embodiment, the 1st screw 50 is connected with the cylindrical part 44 via the connection member 90. FIG. The connecting member 90 includes an annular fixing portion 92, a shaft connecting portion 94 disposed at the center in the radial direction of the fixing portion 92, and a shaft portion 96 that connects the fixing portion 92 and the shaft connecting portion 94. 92 is fixed to the inner peripheral surface of the cylindrical portion 44, and the rotating shaft 51 of the first screw 50 is connected to the shaft connecting portion 94. The conveying blade 52 of the first screw 50 has a size that rotates on a track having a diameter substantially equal to the outer diameter of the cylindrical portion 44, and the developer conveyed in the first conveying direction by the conveying blade 52 is efficient. It is often guided inside the cylindrical portion 44. The upstream end surface 88 of the cylindrical portion 44 is an inclined surface that increases in diameter toward the upstream side in the first transport direction, and in particular, the cylindrical portion 44 at the lower end portion of the cylindrical portion 44. The end surface 88 of the developer is easy to get over.

  FIG. 6 is a cross-sectional view showing the downstream end portion of the tubular portion 44 in the first transport direction. As shown in FIG. 6, the rotating shaft 55 of the second screw 54 is connected to the downstream end of the cylindrical portion 44 so as to coincide with the radial center of the cylindrical portion 44. Although the structure which connects the 2nd screw 54 to the cylindrical part 44 is not specifically limited, In embodiment, the 2nd screw 54 is connected to the cylindrical part 44 via the connection member 90 similarly to the 1st screw 50. It is connected. The conveying blades 56 of the second screw 54 are positioned on the downstream side of the first conveying unit 84 and the first conveying unit 84 located at the upstream end of the second screw 54 in the first conveying direction. A second transport unit 86 is provided. The first transport unit 84 has a size that rotates on a track having a diameter that is the same as or slightly smaller than the inner diameter of the cylindrical part 44. In a state where the second screw 54 is connected to the cylindrical portion 44, the first conveying portion 84 is housed inside the cylindrical portion 44 and is developed to the downstream end within the cylindrical portion 44. It has a function of discharging the agent from the cylindrical portion 44. The second transport unit 86 has a size that rotates on a track having a diameter substantially equal to the outer diameter of the cylindrical part 44, and has a function of transporting the developer discharged from the cylindrical part 44 further downstream. . The downstream end surface 90 of the cylindrical portion 44 has an inclined surface that increases in diameter toward the downstream side in the first conveyance direction, and the developer is smoothly discharged from the inside of the cylindrical portion 44. It is supposed to be.

  FIG. 4 is a perspective view of the cylindrical portion 44 with the outer peripheral surface partially cut away so that the internal structure can be seen. In addition, the arrow in FIG. 4 has shown the 1st conveyance direction.

  As shown in FIG. 4, the first transport member 40 includes a stirring unit 46 that stirs the developer so as to mix the developer and air inside the cylindrical portion 44.

  In the embodiment, the stirring means 46 has a rib-like protrusion 48 that protrudes from the inner peripheral surface of the cylindrical portion 44. A plurality of protrusions 48 are arranged side by side in the first transport direction. Each protrusion 48 is formed in a strip shape extending in a direction inclined with respect to the length direction (first transport direction) of the cylindrical portion 44.

  When the cylindrical portion 44 rotates, the projection 48 also rotates in the circumferential direction of the cylindrical portion 44, so that the projection 48 can agitate the developer inside the cylindrical portion 44. During the rotation of the cylindrical portion 44, the protrusion 48 lifts the developer inside the cylindrical portion 44 in the process of rising from the state positioned at the bottom of the cylindrical portion 44 to the state positioned at the center in the height direction. In the process of rising from the state located at the center in the height direction of the cylindrical part 44 to the state located at the uppermost part, the lifted developer is gradually dropped. As a result, a large amount of air is mixed into the developer inside the cylindrical portion 44 when dropping from the protrusion 48, so that the agitation performance is greatly improved as compared with the case where the developer is agitated by a screw. Further, when the developer is agitated inside the cylindrical portion 44, the developer is not subjected to great stress or pressed, and thus aggregation and deterioration of the developer can be suppressed. Further, it is possible to loosen the soft agglomerated developer by embracing air in the developer.

Further, as shown in FIGS. 5 and 6, the protrusion 48 is configured such that the downstream end in the first transport direction is more than the upstream end in the state where the protrusion 48 is located at the center in the height direction of the cylindrical portion 44. Inclined to be lower. The inclination angle is such that the developer lifted by the protrusion 48 flows down from the upstream side to the downstream side in the first transport direction, so that the developer stirred by the protrusion 48 is stirred. While moving in the first transport direction. Therefore, the developer fed into the cylindrical portion 44 is transported in the first transport direction while being stirred by the protrusion 48.

  However, in the present invention, various changes can be made to the shape, arrangement, and number of the protrusions 48 constituting the stirring means 46. For example, as shown in FIG. 7, the positions of the protrusions 48 in the circumferential direction of the cylindrical portion 44 may be shifted for each protrusion 48, thereby improving the developer transportability in the cylindrical portion 44. It becomes possible to raise.

  While the present invention has been described with reference to the above-described embodiments, the present invention is not limited to the above-described embodiments.

  For example, in the above-described embodiment, the case where the cylindrical portion 44 is cylindrical has been described. However, in the present invention, the cylindrical portion 44 is not necessarily limited to a cylindrical shape as long as the cylindrical portion 44 has a cylindrical shape. It may be.

  Moreover, in the above-mentioned embodiment, although the case where the stirring means 46 was comprised by the protrusion 48 was demonstrated, the stirring means which consists of various structures can be used for this invention. For example, the stirring means may be constituted by a groove formed on the inner peripheral surface of the cylindrical portion 44 so that the developer inside the cylindrical portion 44 can be lifted and dropped as the cylindrical portion 44 rotates. Good.

1 is a diagram illustrating a schematic configuration of an image forming apparatus according to the present invention. 1 is a longitudinal sectional view showing a developing device according to the present invention. FIG. 3 is a transverse sectional view of the developing device shown in FIG. 2. It is a perspective view which shows the cylindrical part of a 1st conveying member. It is sectional drawing which shows the upstream edge part of a cylindrical part. It is sectional drawing which shows the downstream edge part of a cylindrical part. It is sectional drawing which shows the upstream edge part of the cylindrical part which concerns on other embodiment.

Explanation of symbols

2: image forming apparatus, 4: photosensitive member (electrostatic latent image carrier), 30: developing device, 32: housing of developing device, 34: developing roller, 40: first conveying member, 42: second conveying Member: 44: cylindrical portion, 46: stirring means, 48: rib-like projection, 50: first screw, 54: second screw, 60: toner supply port, 62: first transfer chamber, 64: Second transfer chamber, 66: partition, 80: toner hopper.

Claims (4)

A housing for containing the developer;
A transport member that transports the developer in a predetermined transport direction that is horizontal or substantially horizontal in the housing,
Conveying member, possess a cylindrical portion extending in the conveying direction, and a stirring means for stirring the developer in the manner inside the cylindrical portion Komu mix the developer and air,
The stirring means includes
A rib-like protrusion projecting in the form of a strip on the inner peripheral surface of the tubular part, and
The developer inside the cylindrical part can be stirred by rotating in the circumferential direction of the cylindrical part as the cylindrical part rotates, and
The developer in a state where the developer is lifted by the protrusion as the cylindrical portion rotates is provided at an angle so as to flow down from the upstream side to the downstream side in the transport direction.
A developing device. The developing device according to claim 1, wherein the conveying member includes a screw connected to the cylindrical portion. The developer includes a non-magnetic toner and a magnetic carrier,
The housing includes a supply port for supplying the non-magnetic toner,
Claim wherein the conveying member is to pass the vicinity of the supply port, that and, wherein said tubular portion downstream of the supply opening in the conveying direction are provided so as to be arranged 3. The developing device according to 1 or 2 . An image forming apparatus comprising the developing device according to claim 1 .

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