JP5822093B2 - Image forming apparatus - Google Patents

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as an electrophotographic copying machine, a printer, and a facsimile using toner, and more specifically, an image forming apparatus that sucks and discharges discharge products and floating toner generated in a charging device. It is about.

In an electrophotographic image forming apparatus, a corona discharge method is generally widely used as a charging device. In the corona discharge method is a discharge product such as ozone or NO _X is produced. These discharge products adhere to the surface of the photosensitive member and disturb the uniform charging property of the surface of the photosensitive member, or weaken the electric field of corona discharge to inhibit the charging property of the surface of the photosensitive member. For this reason, in a corona discharge charging device, an exhaust fan is usually provided and discharge products are discharged out of the device through an ozone filter.

  On the other hand, in recent years, with the increase in the speed of the image forming apparatus, toner is likely to be scattered from the developing device. In addition, with the miniaturization of the image forming apparatus, the developing device and the charging device are arranged close to each other. For this reason, the floating toner scattered from the developing device easily flows into the charging device. When the floating toner flows into the charging device and adheres to the discharge wire or the like, there is a possibility that the charging of the photoreceptor becomes non-uniform.

  Therefore, in Patent Document 1, for example, an ozone collection duct is disposed on the back side of the charging unit, and a floating toner collection duct is disposed on the upstream side of the charging unit along the rotation direction of the photosensitive member. A technique has been proposed in which ozone and floating toner are collected in the same airflow through communication holes.

JP 2004-45569 A

  However, when ozone and floating toner are collected in the same airflow, if the wind speed at the suction port of the floating toner collection duct is slower than the wind speed at the suction port of the ozone collection duct, the floating toner flows into the charging device and discharge wire There is a risk of soiling. On the other hand, when the wind speed at the suction port of the floating toner collection duct is faster than the wind speed at the suction port of the ozone collection duct, the amount of air sucked from the charging device is reduced, and ozone recovery from the charging device is reduced. In order not to reduce the ozone recovery from the charging device, it is necessary to increase the size of the exhaust fan. However, the increase in the size of the exhaust fan is contrary to the market demand for downsizing and noise reduction of the device.

  The present invention has been made in view of such a conventional problem, and an object of the present invention is to provide an exhaust fan in an image forming apparatus that sucks and removes discharge products such as ozone and floating toner with the same exhaust fan. Without increasing the size, the inflow of floating toner to the charging device is suppressed, and at the same time, the discharge product from the charging device is effectively removed.

The image forming apparatus according to the present invention that achieves the above object includes a rotatable image carrier, a charging device that uniformly charges the surface of the image carrier, and the image carrier by irradiating the image with light. An exposure device for forming an electrostatic latent image on the surface of the carrier, and a developing device for making a visible image by attaching toner to the electrostatic latent image formed on the surface of the image carrier; And the developing device are adjacent to each other, wherein the developing device is opposed to the image carrier at a predetermined interval and rotates while carrying a developer on the surface thereof. A developing roller that supplies toner to the electrostatic latent image on the surface of the image carrier, and the charging device includes a shield case that is open on the image carrier side, and a discharge electrode that is disposed in the shield case. The shield case substantially parallel to the axial direction of the image carrier An exhaust duct is disposed adjacently, and the shield case and the exhaust duct communicate with each other through a communication hole. The exhaust duct is provided with an exhaust fan that exhausts the air in the exhaust duct to the outside of the apparatus. Is formed at a position facing at least one of both end portions of the developing roller, and the air sucked from the gap between the image carrier and the shield case and the suction port by the exhaust fan. The air is discharged out of the apparatus through the exhaust duct, and the suction air speed at the suction port is faster than the suction air speed in the gap between the image carrier and the shield case.

  Here, it is preferable that the suction air volume at the suction port is smaller than the suction air volume in the gap between the image carrier and the shield case.

  Further, when the developing device circulates and conveys the developer in the axial direction of the developing roller and replenishes the developing roller with the developer, the suction port is a toner for the developing roller in the axial direction. It is preferable to form on the side that begins to be replenished.

  In the image forming apparatus of the present invention, the suction air speed at the suction port for sucking the floating toner is made faster than the suction air speed in the gap between the image carrier and the shield case, so that the floating toner can be charged without increasing the exhaust fan. Inflow to the apparatus can be suppressed, and at the same time, discharge products from the charging apparatus can be effectively removed.

  Further, if the suction air volume at the suction port is made smaller than the suction air volume at the gap between the image carrier and the shield case, the decrease in the air volume for removing the discharge product in the charging device becomes small, and the discharge product. Can be more effectively removed.

And a developing roller that faces the image carrier at a predetermined interval and rotates while carrying the developer on the surface to supply toner to the electrostatic latent image on the surface of the image carrier. since those comprising, floating toner ease rather occur at the end portions of the developing roller, the suction port, by forming at least one opposed positions of both end portions of the developing roller, the more effectively airborne toner It can be collected.

  Further, when the developing device circulates and conveys the developer in the axial direction of the developing roller and replenishes the developer with the developer, the suction port is connected to the toner in the axial direction with respect to the developing roller. When the toner is formed on the side where the toner starts to be replenished, the floating toner can be collected more effectively.

1 is a schematic diagram illustrating an example of an image forming apparatus according to the present invention. The longitudinal cross-sectional view of an image forming unit. FIG. 2 is a schematic diagram illustrating an example of a charging device and an exhaust duct. FIG. 3 is a partial perspective view of the photoreceptor and the charging device on the rear side in the axial direction. FIG. 3 is a partial perspective view of the photoreceptor and the charging device on the rear side in the axial direction. FIG. 3 is a vertical perspective view of a photoconductor, a charging device, and an exhaust duct. The perspective view which shows an example of the exhaust duct from an image formation unit to an exhaust fan. FIG. 3 is an explanatory diagram showing a positional relationship between a developing roller and a suction port. Explanatory drawing which shows the positional relationship of a developing device and a suction opening.

  Hereinafter, the image forming apparatus according to the present invention will be described in more detail with reference to the drawings. However, the present invention is not limited to these embodiments.

  FIG. 1 is a schematic diagram showing an example of an image forming apparatus according to the present invention. The image forming apparatus shown in this figure is a so-called tandem color printer. The color printer D is provided with an electrically conductive endless intermediate transfer belt 70 at a substantially central portion and is suspended by rollers 71, 72, and 73. The roller 71 is connected to a motor (not shown), and rotates counterclockwise by driving the motor, whereby the intermediate transfer belt 70 and the rollers 72 and 73 in contact with the intermediate transfer belt 70 are driven to rotate. The roller 73 urges the intermediate transfer belt 70 outward by urging means (not shown) to apply tension to the intermediate transfer belt 70. The secondary transfer roller 74 is in pressure contact with the outside of the belt portion supported by the roller 71. The toner image formed on the intermediate transfer belt 70 at the nip portion (secondary transfer region) between the secondary transfer roller 74 and the intermediate transfer belt 70 is transferred to the conveyed paper P.

  A belt cleaning blade 75 for cleaning the surface of the intermediate transfer belt 70 is provided outside the belt portion supported by the roller 72. The belt cleaning blade 75 is in pressure contact with the roller 72 via the intermediate transfer belt 70, and removes and collects untransferred residual toner at the contact portion with the intermediate transfer belt 70.

  Below the intermediate transfer belt 70, four image forming units 10Y and 10M of yellow (Y), magenta (M), cyan (C), and black (K) are sequentially arranged from the upstream side in the rotation direction of the intermediate transfer belt 70. , 10C, 10K (hereinafter collectively referred to as “image forming unit 10”) are detachably disposed with respect to the apparatus main body D. In these image forming units 10, a toner image of a corresponding color is created using each color developer.

  FIG. 2 is a longitudinal sectional view of the image forming unit 10. The image forming unit 10 has a cylindrical photosensitive member (image carrier) 20 as a center, and a charging device 30, an exposure device 40, and a developing device 50 are sequentially arranged around the cylindrical photosensitive member (image carrier) along its rotation direction (clockwise direction). A primary transfer roller 21 and a cleaning device 60 are disposed. The primary transfer roller 21 is in pressure contact with the photoconductor 20 with the intermediate transfer belt 70 interposed therebetween to form a nip portion (primary transfer region). This configuration is the same regardless of the color.

  In order to charge the surface of the photoconductor 20, the charging device 30 includes a discharge electrode 32 that faces the surface of the photoconductor 20 and is stretched substantially in equilibrium with the rotation axis direction of the photoconductor 20, and the discharge electrode 32. It has a long and narrow box-shaped shield case 31 opened on the photoconductor 20 side, and a grid electrode 33 provided at the opening of the shield case. The discharge electrode 32 is formed of a conductive member such as a metal wire having a sawtooth shape on the side facing the photoconductor 20. A high voltage is applied from a power source (not shown), and the tip of the sawtooth serves as a discharge point. The photoconductor 20 is discharged.

  The developing device 50 includes a developing roller 51 in the vicinity of the photoconductor 20, and a conveying screw 52 and a conveying screw 53 that are circulated and charged while supplying a developer to the developing roller 51, and are housed in a case 54. .

  As shown in FIG. 1, a paper feed cassette 81 as a paper feed device is detachably disposed below the image forming unit 10. The sheets P stacked and accommodated in the sheet cassette 81 are sent out one by one to the transport path R sequentially from the uppermost sheet by the rotation of the sheet feed roller 82 disposed in the vicinity of the sheet cassette 81. The paper P sent out from the paper feed cassette 81 is conveyed to the registration roller pair 83, and is sent out to the above-described secondary transfer area at a predetermined timing.

  The image forming apparatus can be switched between a monochrome mode in which a monochrome image is formed using one color toner (for example, black) and a color mode in which a color image is formed using four color toners.

  An example of an image forming operation in the color mode will be briefly described. First, in each image forming unit 10, the outer peripheral surface of the photoreceptor 20 that is rotationally driven at a predetermined peripheral speed is charged by the charging device 30. Next, light corresponding to image information is projected from the exposure device 40 onto the surface of the charged photoconductor 20 to form an electrostatic latent image. Subsequently, the electrostatic latent image is visualized with toner as a developer supplied from the developing device 50. When the toner image of each color formed on the surface of the photoreceptor 20 in this way reaches the primary transfer region by the rotation of the photoreceptor 20, the intermediate transfer from the photoreceptor 20 is performed in the order of yellow, magenta, cyan, and black. It is transferred (primary transfer) onto the belt 70 and superimposed.

  Residual toner remaining on the photoconductor 20 without being transferred to the intermediate transfer belt 70 is scraped off by the blade 61 of the cleaning device 60 shown in FIG. 2 and removed from the outer peripheral surface of the photoconductor 20.

  The superimposed four color toner images are conveyed to the secondary transfer region by the intermediate transfer belt 70. On the other hand, the paper P is conveyed from the registration roller pair 83 to the secondary transfer area in accordance with the timing. Then, the four color toner images are transferred (secondary transfer) from the intermediate transfer belt 70 to the paper P in the secondary transfer region. The sheet P on which the four color toner images are transferred is conveyed to the fixing roller pair 84. In the fixing roller pair 84, the paper P passes through the nip portion between the fixing roller and the pressure roller. During this time, the paper P is heated and pressurized, and the toner image on the paper P is melted and fixed on the paper P. The paper P on which the toner image has been fixed is discharged by a discharge roller pair 85 to a paper discharge tray formed on the upper surface of the apparatus.

  On the other hand, residual toner remaining on the intermediate transfer belt 70 without being transferred onto the paper P is scraped off by the cleaning blade 75 and removed from the outer peripheral surface of the intermediate transfer belt 70. Thereafter, the rotational drive of each photoconductor 20 and the intermediate transfer belt 70 is stopped.

  FIG. 3 shows a schematic diagram of the charging device 30. As described above, the shield case 31 of the charging device 30 has a long and narrow box shape with the photosensitive member side opened. The shield case 31 is grounded and maintains the electric field surrounding the discharge electrode 32 to maintain a constant electric environment so that stable discharge is performed. The grid electrode 33 has a mesh shape, is provided at an opening position on the photosensitive body side of the shield case 31 and is insulated from the shield case 31. A bias voltage is applied by a power supply (not shown). The grid electrode 33 functions to alleviate even if the discharge from the discharge electrode 32 varies in the axial direction of the photoconductor 20 and to ensure the uniformity of the charged potential of the photoconductor 20.

  A cover member 37 is provided on a side wall of the shield case 31 facing the developing device 50 with a predetermined gap. A duct body 90 that forms part of the exhaust duct 9 is formed on the bottom surface of the shield case 31 by the housing 36 and the cover member 37. A communication hole 34 is provided between the duct body 90 and the shield case 31. In addition, a flexible film 35 for adjusting the gap B with the photoconductor 20 is attached to the ends of the opening of the shield case 31 on the upstream and downstream sides in the rotation direction of the photoconductor 20.

  4 and 5 are partial perspective views of the photoreceptor 20 and the charging device 30 on the rear side in the axial direction. This perspective view is a perspective view with the cover member 37 removed. On the side wall of the shield case 31, a square-string-like seal member 38 is stuck substantially parallel to the axial direction of the photoconductor 20 except for the rear side in the axial direction. In the portion where the seal member 38 is adhered, air is prevented from flowing into the duct body 90 from the gap between the side wall of the shield case 31 and the cover member 37. On the other hand, in the portion where the seal member 38 is not adhered, air flows into the duct body 90, and this is the suction port A.

FIG. 6 is a perspective view showing the flow of the charging device 30 and the surrounding air. When an exhaust fan 97 (shown in FIG. 7), which will be described later, is driven, the duct body passes through the shield case 31 from a gap B formed between the photoconductor 20 and the flexible film 35 in the axial direction of the photoconductor 20. Air flows into 90. At the same time, air also flows into the duct body 90 from the suction port A. What is important here is to make the suction air speed at the suction port A faster than the suction air speed at the gap B. As a result, most of the air Fa containing a large amount of floating toner flows into the duct body 90 from the suction port A, and the inside of the shield case 31 is suppressed from being contaminated with the floating toner. On the other hand, discharge products such as ozone and NO _X is discharged to the duct body 90 through the communication hole 34 by the air Fb flowing through the gap B in the shield case 31.

  The suction wind speed at the suction port A is preferably about 2 to about 3 times the suction wind speed at the gap B. The air volume at the suction port A is preferably about 1/10 times the air volume at the gap B. As a result, it is possible to effectively prevent the floating toner from flowing into the charging device 30 and discharge and remove the discharge product from the charging device 30.

  In FIG. 7, the perspective view which shows the whole structure of the exhaust duct 9 is shown. The exhaust duct 9 includes a duct main body 90, a connection duct portion 92, a collective duct portion 93, an L-shaped duct portion 94, and a relay duct portion 95. An exhaust fan 97 and an ozone filter 96 are provided at the downstream end of the relay duct 95 in the air flow direction. When the exhaust fan 97 is driven, air is sucked from the suction port A and the gap B, and the air flows through the duct body 90 from the discharge hole 91 (shown in FIG. 4) to the connection duct portion 92. Then, after passing through the collecting duct portion 93, the L-shaped duct portion 94, and the relay duct portion 95 and being purified by the ozone filter 96, it is discharged to the outside through the discharge hole 98.

Formation position of the suction port A is floating toner from the viewpoint of efficiently removed by suction, preferably formed at a position opposite to the axial end portions of the developing roller 51. This is because the floating toner is likely to be generated at both ends of the developing roller 51 in the axial direction. FIG. 8 is a schematic plan view showing the positional relationship between the developing roller 51 and the suction ports A1 and A2. Floating toner is likely to be generated at both axial ends C1 and C2 of the developing roller 51. Therefore, suction ports A1 and A2 are formed at positions facing the end portions C1 and C2 of the developing roller 51. In addition, the thickness and length of the arrow in the figure indicate the air volume and the air speed of the air flowing into the duct body 90 and the air flowing through the duct body 90. The thicker the arrow, the more the air volume and the longer the arrow. Wind speed is fast.

  Although the air Fa sucked from the suction ports A1 and A2 has a small air volume, the air speed is fast, and the floating toner generated from both axial ends of the developing roller 51 is effectively sucked from the suction ports A1 and A2. On the other hand, the air Fb sucked from the gap B elongated in the axial direction has a slower air velocity than the air Fa, but has a large air volume because the gap B has a large cross-sectional area, and the discharge product generated in the charging device 30 is generated by the air Fb. It is effectively discharged and removed. The amount of air flowing through the duct body 90 increases as it approaches the discharge hole 91, and the wind speed decreases.

  As shown in FIG. 9, when the developing device 50 is a device that circulates the developer by the conveying screw 52 and the conveying screw 53, that is, after the developer is conveyed to the left in the drawing by the conveying screw 53, When the apparatus is moved to the conveying screw 52 side, conveyed to the right in the figure by the conveying screw 52, and then moved again to the conveying screw 53 to circulate the developer, the developer is transferred from the conveying screw 52 to the developing roller 51. The floating toner is likely to be generated in the portion where the supply starts. Therefore, in the case of such a developing device, it is preferable to form the suction port A1 at a position facing the axial end C1 of the developing roller 51.

  The image forming apparatus of the present invention is useful because it can suppress the inflow of floating toner to the charging device without increasing the size of the exhaust fan, and at the same time can effectively collect ozone from the charging device.

9 Exhaust duct A Suction port B Gap 20 Photoconductor (image carrier)
DESCRIPTION OF SYMBOLS 30 Charging device 31 Shield case 32 Discharge electrode 34 Communication hole 40 Exposure device 50 Developing device 51 Developing roller 90 Duct body 97 Exhaust fan

Claims (3)

A rotatable image carrier, a charging device that uniformly charges the surface of the image carrier, and an exposure device that irradiates the image carrier with light to form an electrostatic latent image on the surface of the image carrier. And a developing device that visualizes the electrostatic latent image formed on the surface of the image carrier by attaching toner, and the charging device and the developing device are provided adjacent to each other. A forming device,
The developing device includes a developing roller that faces the image carrier at a predetermined interval, rotates while carrying a developer on the surface, and supplies toner to the electrostatic latent image on the surface of the image carrier,
The charging device has a shield case opened on the image carrier side, and a discharge electrode arranged in the shield case,
An exhaust duct is disposed substantially parallel to the axial direction of the image carrier and adjacent to the shield case,
The shield case and the exhaust duct communicate with each other through a communication hole,
The exhaust duct is provided with an exhaust fan for discharging the air in the exhaust duct to the outside of the apparatus, and a suction port for sucking floating toner is formed at a position facing at least one of both end portions of the developing roller ,
By the exhaust fan, the air sucked from the gap and the suction port between the image carrier and the shield case is exhausted out of the apparatus through the exhaust duct,
An image forming apparatus, wherein a suction air speed at the suction port is faster than a suction air speed in a gap between the image carrier and the shield case.   The image forming apparatus according to claim 1, wherein a suction air amount at the suction port is smaller than a suction air amount in a gap between the image carrier and the shield case. The developing device circulates and conveys the developer in the axial direction of the developing roller and replenishes the developing roller with the developer;
The suction port, the axial direction of the developing roller image forming apparatus according to claim 1 or 2 SL placing toner is formed on the side starts to be replenished against.