JP2005181805A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of restraining/preventing its inside from being soiled by scattered toner, using comparatively simple constitution. <P>SOLUTION: The image forming apparatus is equipped with a developing sleeve 30; a hollow photoreceptor drum 14 arranged facing the sleeve 30, supported rotatably about a shaft 76 and having an open end at one end in the shaft direction; through-holes 62 and 64, which are formed on the drum 14 and positioned nearer one end side and/or the other end side in the shaft direction than the outer peripheral surface area of the drum 14 facing the developer carrying area 61 of the sleeve 30 and through which the inside of the drum 14 communicates with the outer peripheral surface area of the drum 14; and a mechanism for generating air flow moving toward the inside of the drum 14 via the through-holes 62 and 64 from the outside of the drum 14 and moving toward the outside of the drum 14 via the open end. The mechanism is equipped with a driving means for rotating the shaft of the drum 14, and a blade 74, provided inside the drum 14 and fixed on the shaft so as to discharge the air inside the drum 14 to the outside, via the open end when the shaft is rotated by the driving means. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, or a complex machine of these.

  In general, an electrophotographic image forming apparatus forms an electrostatic latent image on an image carrier by uniformly charging the surface potential of the image carrier and selectively exposing the toner, and further developing toner from a developing unit. , The electrostatic latent image is developed to form a toner image, and the toner image is transferred to a sheet to form an image.

  In such an image forming apparatus, there is a known problem that reversely charged or zero-charged toner flying from the developing unit is scattered in the apparatus and contaminates the apparatus.

In order to solve such a problem, a method has been proposed in which a suction duct having a suction opening is formed on the lower side of the developing unit, and toner flying from the developing unit is sucked through the duct (for example, (See Patent Document 1).
Japanese Utility Model Publication No. 1-77669

  However, in the above-described configuration, the suction duct needs to have a sufficient volume in order to ensure a sufficient suction effect. For this reason, a sufficiently large space is provided below the developing unit, which increases the size of the apparatus. Invite.

  Accordingly, an object of the present invention is to provide an image forming apparatus capable of suppressing and preventing contamination in the apparatus due to scattered toner with a relatively simple configuration.

In order to achieve the above object, an image forming apparatus according to the present invention includes:
A developer carrier;
A hollow image carrier disposed opposite to the developer carrier, rotatably supported around a predetermined axis, and having an open end at least at one end in the axial direction;
An image carrier outer peripheral surface region and an image carrier formed on the image carrier and positioned on one end side and / or the other end side in the axial direction of the image carrier outer peripheral surface region facing the developer carrying region of the developer carrier A through hole communicating with the interior;
A mechanism for generating an air flow from the outside of the image carrier to the inside of the image carrier through the through hole and further to the outside of the image carrier through the open end;
An image forming apparatus.

  In such a configuration, the toner flying from the developer carrying member of the developing section is guided to the inside of the image carrying member from the outer peripheral surface end side region where the toner carrying image does not face the developer carrying region and thus does not form a toner image. Contamination of the apparatus with toner can be suppressed / prevented. In this way, since the space inside the image carrier is used as a suction duct, it is not necessary to provide a separate duct, and therefore the apparatus is not increased in size.

  In one embodiment, the airflow generation mechanism includes a driving unit that rotates the shaft of the image carrier and an inside of the image carrier. When the shaft is rotated by the driving unit, air inside the image carrier is passed through the open end. And a blade fixed to the shaft so as to be discharged to the outside. In this case, since the toner flying from the developer carrier can be guided to the inside of the image carrier using the rotation of the image carrier, a suction means such as a fan becomes unnecessary, and as a result, the airflow generation mechanism is simplified. Can be

  The air flow generating mechanism further includes a blade fixed to the inner wall portion of the image carrier in the vicinity of the through hole so that air outside the image carrier is sucked into the inside through the through hole when the shaft of the image carrier is rotated by the driving means. You may prepare. Thereby, the suction efficiency of the toner flying from the developer carrier into the image carrier can be further increased.

  In another embodiment, the airflow generation mechanism includes means for sucking air inside the image carrier through the open end. In this case, the suction force of the suction means may be variable according to predetermined information (for example, the usage time of the developing unit) related to the ease of toner flying from the developer carrier. As a result, the suction force is increased if the toner is easy to fly, and the suction force is lowered if the toner is difficult to fly, thereby increasing the collection efficiency of the flying toner and suppressing the power consumption associated with driving the suction means. it can.

  According to the present invention, toner diffusion in the apparatus can be effectively suppressed / prevented by a simple configuration using the space inside the image carrier as a suction duct.

  Embodiments according to the present invention will be described below with reference to the accompanying drawings. The same or similar components are denoted by the same reference numerals or the same reference numerals with appropriate subscripts throughout the drawings. Note that in this specification, terms indicating directions (for example, “up”, “down”, “right”, “left”, and other terms including these terms) are used as appropriate, but in the drawings used for explanation These terms are only intended to indicate the direction of the present invention, and the present invention should not be construed to be limited to these terms. In the following, an example in which the present invention is applied to a color image forming apparatus will be described, but the present invention is also applicable to a monochrome image forming apparatus.

  FIG. 1 is an overall configuration diagram of a color image forming apparatus (printer) 2 according to an embodiment of the present invention. The image forming apparatus 2 includes an intermediate transfer belt 4 at an almost central portion inside thereof. The intermediate transfer belt 4 is supported on the outer peripheral portions of the three rollers 6, 8, and 10 and is driven to rotate in the direction of arrow A. The roller 6 is a tension roller that applies tension to the intermediate transfer belt 4. The roller 10 is connected to a drive motor (not shown), and the rollers 6 and 8 are driven to rotate as the roller 10 rotates.

  Below the lower horizontal portion of the intermediate transfer belt 4, four process units 12 (12Y, 12M, 12C, 12C, 12C, 12C, 12C, 12C, 12M, 12M, 12C, respectively) corresponding to the respective colors of yellow (Y), magenta (M), cyan (C), and black (K). 12K) are arranged along the intermediate transfer belt 4 side by side. The process units 12Y, 12M, 12C, and 12K are detachably attached to the image forming apparatus 2.

  The process units 12Y, 12M, 12C, and 12K are photosensitive drums 14 (14Y, 14M, 14C, and 14C) that are rotationally driven around a shaft by a drive motor at an upper position in the state of being incorporated in the apparatus 2 as an image carrier. 14K). The configuration of the photosensitive drum 14 including the drive motor and the shaft will be described in detail later. Around each of the photosensitive drums 14 (14Y, 14M, 14C, 14K), a charger 16, a print head unit 18, a developing unit 20, and an intermediate portion are sequentially arranged along the rotation direction B (clockwise direction). A primary transfer roller 22 (22Y, 22M, 22C, and 22K) that faces the photosensitive drums 14Y, 14M, 14C, and 14K with the transfer belt 4 interposed therebetween, and a cleaner 24 are disposed. Each member 14, 16, 18, 20, 24 excluding the primary transfer roller 22 is disposed in the housing 26 of each process unit 12.

  Each developing unit 20 includes a storage unit 28 that stores a two-component developer composed of yellow, magenta, cyan, or black toner and a magnetic carrier, and an opening formed as a developer carrier on the right wall of the storage unit 28. And a developing sleeve 30 facing the photosensitive drum 14. The developing sleeve 30 can be driven to rotate clockwise by a motor (not shown). A magnet roll (not shown) having a plurality of magnetic poles arranged in the circumferential direction is fixed inside the developing sleeve 30. The developing unit 20 is also a doctor blade (not shown) so as to contact the outer peripheral surface of the developing sleeve 30 on the upstream side of the facing region (developing region) between the developing sleeve 30 and the photosensitive drum 14 with respect to the rotation direction of the developing sleeve 30. ) To regulate the amount of developer conveyed to the development area.

  The primary transfer roller 22 is in pressure contact with the photosensitive drum 14 via the intermediate transfer belt 4, and a nip portion between the primary transfer roller 22 and the intermediate transfer belt 4 is a primary transfer region 32.

  The secondary transfer roller 34 is pressed against the portion of the intermediate transfer belt 4 supported by the roller 10, and the nip portion between the secondary transfer roller 34 and the intermediate transfer belt 4 becomes a secondary transfer region 36. Yes.

  A belt cleaner 40 for scraping off toner remaining on the intermediate transfer belt 4 after the secondary transfer and collecting it in the waste toner box 38 is pressed against the portion of the intermediate transfer belt 4 supported by the roller 8. .

  A paper feed cassette 42 is detachably disposed below the image forming apparatus 2. The sheets S stacked and stored in the sheet cassette 42 are one sheet at a time from the uppermost one by the rotation of the sheet supply roller 44 disposed at a position facing the vicinity of the front end of the sheet S stacked in the sheet cassette 42. It is sent out to the conveyance path 46.

  The conveyance path 46 is provided on the upper surface of the apparatus 2 from the paper feed cassette 42 through the nip portion of the timing roller pair 48, the secondary transfer region 36, the nip portion of the fixing roller pair 50 and the nip portion of the paper discharge roller pair 52. The paper discharge tray 54 extends.

  Next, a schematic operation of the image forming apparatus 2 will be described.

  When an image signal is input from an external device (for example, a personal computer) to an image signal processing unit (not shown) of the image forming apparatus 2, the image signal processing unit color-converts the image signal into yellow, cyan, magenta, and black. A digital image signal is generated, and this signal is transmitted to the LED drive circuit for the print head. This drive circuit performs exposure by causing the print head unit 18 of each of the process units 12Y to 12K to emit light based on the input digital signal. As a result, electrostatic latent images for the respective colors are formed on the surfaces of the photosensitive drums 14Y to 14K.

  The electrostatic latent images formed on the photosensitive drums 14Y to 14K are developed by the developing units 20 to become toner images of the respective colors. Then, the toner images of the respective colors are primarily transferred in a superimposed manner on the intermediate transfer belt 4 that moves in the arrow A direction by the action of the primary transfer rollers 22Y to 22K.

  The superimposed toner image formed on the intermediate transfer belt 4 in this way reaches the secondary transfer area 36 as the intermediate transfer belt 4 moves. In the secondary transfer region 36, the superimposed toner images are collectively sent to the sheet S supplied from the sheet feeding cassette 42 to the conveyance path 46 by the action of the secondary transfer roller 34 and then supplied by the timing roller pair 48. Second transfer is performed. The toner remaining on the intermediate transfer belt 4 after the secondary transfer is collected by the belt cleaner 40.

  The sheet S on which the toner image is secondarily transferred is sent to the pair of fixing rollers 50 through the conveyance path 46 where the toner image is fixed on the sheet S. Then, the paper S is discharged to the paper discharge tray 54 via the paper discharge roller pair 52.

  Next, a mechanism for preventing contamination in the apparatus 2 due to toner scattering will be described mainly with reference to FIGS. This contamination prevention mechanism guides the toner flying from the developing sleeve 30 of the developing unit 20 to the inside of the opposing photosensitive drum 14.

  Specifically, the photosensitive drum 14 includes a cylindrical member 56 having one end and the other end in the axial direction that are opened, and flanges 58 and 60 that are respectively connected to one end and the other end of the cylindrical member. The cylindrical member 56 has a predetermined axial length, and is located on the axial end side with respect to the developer carrying region 61 (having a width substantially equal to the width of the magnet roll) of the developing sleeve 30 facing the cylindrical member 56. This region is provided with one or more (a plurality of through holes in the figure) through holes 62 and 64 along the circumferential direction of the cylindrical member 56. Blades 66 and 68 are fixed to inner wall portions of the cylindrical member 56 in the vicinity of the through holes 62 and 64, respectively. The shape of the blades 66 and 68 is such that when the cylindrical member 56 and thus the photosensitive drum 14 rotates in the B direction (clockwise direction in FIG. 1), the air outside the cylindrical member 56 is sucked into the inside through the through holes 62 and 64. Is set to

  The flange 58 includes a cylindrical portion 70 that forms a central hole, and one or more (preferably plural) blades 74 fixed to the cylindrical portion 70, and the cylindrical portion 70 is drivingly connected to a motor 75. A shaft 76 is inserted. The inside of the cylindrical member 56 communicates with the outside (further, outside the apparatus 2) via the flange 58 (that is, one end of the photosensitive drum 14 is open). The shape of the blade 74 is set so that the air inside the cylindrical member 56 is discharged to the outside through the flange 58 when the photosensitive drum 14 is rotated in the B direction. On the other hand, the flange 60 has a block shape that forms a center hole and closes the other end of the cylindrical member 56, and is rotatably supported by a shaft 80 inserted into the center hole.

  As shown in FIG. 3A, the flange 58 has an outer diameter that is substantially equal to the inner diameter of the cylindrical member 56, and includes a connecting portion that is fitted into the cylindrical member 56 and connects the flange 58 and the cylindrical member 56. The end portion of the connecting portion is located on the axial end side with respect to the through hole 62, and a filter 82 for collecting toner is attached to the end portion.

  Referring also to FIG. 4, in such a contamination prevention mechanism, when the photosensitive drum 14 rotates in the B direction during image formation, the space 84 between the housing unit right wall 28 a of the developing unit 20 and the photosensitive drum 14 is formed. The air flow 86 is generated from the lower side toward the upper side. The toner flows from the developing sleeve 30 by the air flow 86. One of the causes of the toner flying is that the charging characteristic of the toner deteriorates when the developing unit 20 is used for a long time, so that the toner receives a centrifugal force greater than the electrostatic force with the magnetic carrier by the rotation of the developing sleeve 30. Is mentioned. In particular, the amount of toner flying from both axial ends of the outer peripheral surface of the developing sleeve 30 (the outer peripheral surface positioned on the outer side in the axial direction of the developer carrying region 61 [FIG. 2B]) is large. The reason for this is that the magnet roller does not face the inside at both ends of the outer peripheral surface of the developing sleeve 30. Therefore, when the developer carried on the developing sleeve 30 is regulated by the doctor blade as the developing sleeve 30 rotates, This is because a part of the excess developer may move to both ends of the outer peripheral surface not facing the magnet roller and pass through the doctor blade. The toner carried in the region where the magnet roller does not face is likely to fly due to the centrifugal force accompanying the rotation of the developing sleeve 30.

  On the other hand, during image formation, as shown in FIGS. 3A and 3B, the photosensitive drum 14 rotates in the B direction from the outside of the photosensitive drum 14 to the inside through the through holes 62 and 64, and further photosensitive. In the body drum 14, an air flow is generated from the flange 60 side to the outside of the drum 14 through the flange 58, and the toner flying mainly from both axial ends of the outer peripheral surface of the developing sleeve 30 passes through the through holes 62 and 64. After being guided into the photosensitive drum 14, the dust is collected by the filter 82.

  As a comparative example, when the contamination prevention mechanism (air flow generation mechanism) as described above is not provided, the intermediate transfer belt 4 and the accommodating portion of the developing unit 20 are moved by the movement of the intermediate transfer belt 4 in the A direction as shown in FIG. An air flow 90 is generated from the left side to the right side mainly on the upper layer side of the space 88 between the upper wall 28b (the housing upper wall of the process unit 12). This air flow 90 and the air flow 94 generated from the lower side to the upper side in the space 84 between the accommodating portion right wall 28a and the photosensitive drum 14 merge in the vicinity of the upstream side of the primary transfer region 32, and the space 90 An air flow 96 is generated mainly from the right side to the left side of the lower layer side. The flying toner is guided to the space 88 between the upper wall 28b and the intermediate transfer belt 4 along with the air flow 96, falls in its own weight, accumulates on the upper wall 28b, and contaminates the outer surface of the process unit 12. . Further, since the airflows 90 and 96 collide with each other and turbulent flow is generated in the space 88, the flying toner does not accumulate much on the upper wall 28b. There is also a possibility that the components on the apparatus main body side or other components in the housing 26 may be contaminated.

  On the other hand, in the present embodiment, the flying toner is sucked into the photosensitive drum 14 through the through holes 62 and 64, thereby preventing contamination of the outer surface of the housing of the developing unit 20 and the like. Further, by using the internal space of the photosensitive drum 14 as a suction duct, it is not necessary to provide a separate suction duct, and the image forming apparatus 2 can be downsized. Further, since the filter 82 is provided in the photosensitive drum 14, when the process unit 12 is replaced with a new unit, the filter is also replaced at the same time, so that the work efficiency during maintenance can be improved.

  Japanese Patent Application Laid-Open No. 5-289590 discloses an image forming apparatus in which a filter for collecting toner is provided in a hollow portion of a photosensitive drum to generate an air flow from one end of the opened photosensitive drum to the other end. In this embodiment, the flying toner is guided into the photosensitive drum through the through holes 62 and 64, and is not guided into the drum through the open end as in the above-described conventional configuration. Further, in the conventional configuration, since the end portion of the photosensitive drum is not opposed to the developing portion, it is difficult to suck the toner flying from the developing portion by the rotation of the drum.

  The above description relates to an embodiment of the present invention, and the present invention is not limited to this and can be variously modified. For example, the present invention is not limited to the two-component developer as in the above-described embodiment, but can be applied to a one-component developer including only toner. In this case, the developer carrying area means an outer peripheral surface area of a developer carrying body (for example, a developing roller) on which toner charged by, for example, a charging blade is carried during image formation.

  In the above embodiment, the filter 82 is used as a means for collecting the toner guided into the hollow photosensitive drum 14. However, instead of or in addition to this, another toner dust collecting means may be used. Good. As an example, a toner adsorption tape is provided along the inner wall of the photosensitive drum.

  Further, instead of providing the through holes 62 and 64 in the cylindrical member 56 of the photosensitive drum 14, a through hole for communicating the inside and the outside of the photosensitive drum 14 may be provided in the flange 58 and / or 60.

  In addition, in the above embodiment, the flying toner is collected in the photoconductive drum 14 while image formation is being performed. However, when the photoconductive drum 14 is idled during non-image formation (for example, after completion of image formation), The recovery rate may be increased.

  Furthermore, in the above-described embodiment, the through holes 62 and 64 are provided along the circumferential direction of the photosensitive drum 14. However, in order to efficiently suck the flying toner, as shown in FIG. Covers 100 and 102 may be provided so as to cover the through holes 62 and 64 along the circumferential direction of the photosensitive drum 14 except for the region facing the surface of the photosensitive drum 14.

  In addition, one end of the through hole provided in the photosensitive drum 14 may be located in the outer peripheral surface region positioned on the axial end side with respect to the outer peripheral surface region facing the developer carrying region 61, and the other end (photosensitive member). The position of the end portion on the drum inner side may be on the inner wall portion at the same position as the outer peripheral surface region facing the developer carrying region 61 in the axial direction.

  Further, in the above embodiment, as the air flow generation mechanism (contamination prevention mechanism), a mechanism that generates an air flow that guides toner into the drum through the through holes 62 and 64 by the rotation of the photosensitive drum 14 is used. The toner may be more reliably guided into the drum by using a suction device such as a fan. An example of the configuration of such an airflow generating mechanism is shown in FIG.

  Unlike the above-described embodiment, the flange 58 ′ does not include the fixed blade 74, and the end of the photosensitive drum 14 ′ opposite to the side to be inserted into the cylindrical member 56 has a cylindrical shape. The duct 104 is rotatably supported by the duct 104 in a state of being partially accommodated at one end of the duct 104 provided in the process unit. A fan 106 is provided at the other end of the duct 104.

  In the example of FIG. 7, instead of providing the fixed blades 66 and 68, the flanges 58 ′ and 60 ′ have a portion that protrudes further into the drum than the through holes 62 and 64 from the connecting portion with the cylindrical member 56. As a result, a narrow air passage communicating with the through holes 62 and 64 is formed inside the cylindrical member 56. This is for increasing the collection efficiency of the flying toner by increasing the flow velocity when air is guided into the photosensitive drum 14 through the through holes 62 and 64.

  In such a configuration, when the photosensitive drum 14 'is rotated by rotating the motor 75 during image formation and suction is performed by the fan 106, the outer side of the photosensitive drum 14' is directed to the inside through the through holes 62 and 64, and further, In the photosensitive drum 14 ′, an air flow is generated from the flange 60 ′ side through the flange 58 ′ to the outside of the drum 14 ′ and further to the outside of the apparatus through the duct 104, and the toner flying from the developing unit passes through the through holes 62 and 64. Then, the dust is collected by, for example, a filter 82 ′ provided at the projecting end of the flange 58 ′.

  When the suction unit is provided as in the example shown in FIG. 7, the suction force of the suction unit (for example, the rotational speed in the case of a fan) is determined according to predetermined information related to the ease of toner flying from the developing unit. It may be variable. Examples of the predetermined information include development unit usage time, system speed, toner replenishment timing, usage environment (humidity, temperature, etc.), and the like. For example, if the developing unit is used for a long time, the toner is more likely to fly due to the deterioration of the toner, so the suction force is increased. In the case of a two-component developer, the toner is replenished to the developing device when the ratio of the toner to the carrier decreases. However, since the new toner is not sufficiently charged compared to the toner already in the developing device, As the amount supplied to the developing sleeve of the developing unit increases, the amount of toner flying increases. Therefore, after the toner is replenished, the suction force of the suction means is increased as compared to before the replenishment.

1 is a schematic configuration diagram showing an embodiment of an image forming apparatus according to the present invention. (A) The perspective view which shows the photosensitive drum of FIG. (B) The side view which shows the photosensitive drum and developing sleeve of FIG. (A) Sectional drawing of the photosensitive drum of FIG. (B) Sectional drawing along IIIb-IIIb of Fig.3 (a). FIG. 2 is an enlarged cross-sectional view showing the vicinity of the upper surface of the process unit of FIG. 1. The figure similar to FIG. 4 which shows the airflow when not providing a contamination prevention mechanism. The perspective view which shows the modification of a photoreceptor drum. FIG. 4 is a view similar to FIG. 3 showing another embodiment of a pollution control mechanism.

Explanation of symbols

2 Image forming apparatus 14 (14Y to 14K) Photosensitive drum (image carrier)
30 Development sleeve (developer carrier)
56 Cylindrical member 58, 60 Flange 61 Developer carrying area 62, 64 Through hole 66, 68 Blade 74 Blade 76, 80 Shaft 82 Filter

Claims (5)

A developer carrier;
A hollow image carrier disposed opposite to the developer carrier, rotatably supported around a predetermined axis, and having an open end at least at one end in the axial direction;
An image carrier outer peripheral surface region and an image carrier formed on the image carrier and positioned on one end side and / or the other end side in the axial direction of the image carrier outer peripheral surface region facing the developer carrying region of the developer carrier A through hole communicating with the interior;
A mechanism for generating an air flow from the outside of the image carrier to the inside of the image carrier through the through hole and further to the outside of the image carrier through the open end;
An image forming apparatus.   The air flow generating mechanism is provided inside the image carrier with the drive means for rotating the shaft of the image carrier, and when the shaft is rotated by the drive means, the air inside the image carrier is externally passed through the open end. The image forming apparatus according to claim 1, further comprising a blade fixed to the shaft so as to be discharged.   The airflow generating mechanism is fixed to the inner wall portion of the image carrier in the vicinity of the through hole so as to suck air outside the image carrier through the through hole when the shaft of the image carrier is rotated by the driving means. The image forming apparatus according to claim 1, further comprising a blade.   2. The image forming apparatus according to claim 1, wherein the air flow generating mechanism includes means for sucking air inside the image carrier through the open end. The image forming apparatus according to claim 1, wherein means for collecting developer is provided inside the image carrier.

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