JP2010271354A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus in which air can be made to efficiently flow in a charger. <P>SOLUTION: The image forming apparatus includes a first opening section 54, provided on a casing 50 so that the air is allowed to flow into the charger 29 by being branched from a flow path 62; and a second opening section 55, provided on the casing 50 positioned on a more downstream side of the flow path than the first opening section 54 so that the air inside the charger 29 is returned to the flow path 62. The casing 50 and a duct wall 61 are configured so that the flow speed of the air flow is higher in the vicinity of the second opening section 55 than in the vicinity of the first opening section 54 and a distance B from the second opening section 55 to the duct wall 61 is shorter than a distance A from the first opening section 54 to the duct wall 61. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an image forming apparatus.

  In general, as an image forming apparatus to which an electrophotographic method is applied, a photosensitive drum charged by a charger provided with a charging wire is irradiated with laser light, and the potential of the portion irradiated with the laser light is lowered to be on the photosensitive drum. A laser printer that forms an electrostatic latent image and forms a predetermined image on a sheet by transferring the developer image formed by supplying toner as a developer to the electrostatic latent image is known. It has been.

  As such a laser printer, a printer having a scanner unit for scanning a laser beam and a process unit disposed below the scanner unit via a predetermined gap is conventionally known ( Patent Document 1).

JP 2005-292356 A

  In the above configuration, ozone is generated around the charging wire as it is discharged. There is a known problem that when the ozone adheres to the charging wire, the surface of the charging wire is oxidized, thereby causing uneven charging in the next image forming operation. In particular, ozone is heavier than air, and therefore ozone tends to stay around the charger, thus deteriorating the charging efficiency of the charging wire. Therefore, it has been necessary to introduce fresh air into the charger to disperse ozone. However, the space in the laser printer is limited, and it has been difficult to design the flow path so that air can efficiently flow into the charger.

  In view of the above problems, an object of the present invention is to provide an image forming apparatus capable of efficiently flowing air into a charger.

  In order to solve the above-described problems, an image forming apparatus according to the present invention includes a process unit that includes an image forming apparatus main body, and a photosensitive drum provided in the image forming apparatus main body, and a charger that charges the photosensitive drum. A wall portion that is provided in the image forming apparatus main body so as to face the casing and forms a flow path together with the casing, and an air flow generation means for generating an air flow in the flow path, A first opening provided in the casing so as to be upstream of the flow path and branch from the flow path to allow air to flow into the charger; and the flow from the first opening. A second opening provided in the casing so as to return the air in the charger to the flow path, and the casing and the wall are provided with the first opening. Part The wall from the second opening to the wall is greater than the distance A from the first opening to the wall so that the airflow velocity is greater near the second opening than near. The distance B is made small.

  According to a second aspect of the present invention, the process unit is provided with a guide member that guides air in the charger to the second opening, and the second opening is formed by the guide member. Further, it is provided downstream of the rotating direction of the photosensitive drum and upstream of the charger in the rotating direction of the photosensitive drum.

  The invention according to claim 3 is characterized in that the guide member is a collection member that contacts the photosensitive drum and collects the developer on the photosensitive drum.

  According to a fourth aspect of the present invention, the process unit is detachable from the image forming apparatus main body, and the wall portion restricts the flow path in the vicinity of the second opening. Proximity to the casing.

  According to a fifth aspect of the present invention, the air flow generating means is an exhaust fan that sucks air from the second opening and draws it out of the image forming apparatus main body.

  According to the present invention, the flow path is formed between the wall portion and the casing of the process unit, and an air flow is generated in the flow path by the air flow generating means. With respect to this flow path, the casing and the wall are arranged so that the distance B from the second opening to the wall is smaller than the distance A from the first opening to the wall. When the distance from the casing to the wall portion changes, the flow velocity of the air flow flowing through the portion changes. That is, the flow velocity near the second opening located on the downstream side is faster than the flow velocity of the air flow near the first opening located on the upstream side in the flow path.

  Accordingly, the pressure near the second opening located on the downstream side is lower than the pressure near the first opening located on the upstream side. Then, due to the pressure difference, the flow rate of the air flow that passes through the first opening and flows into the charger and flows to the second opening increases. Therefore, by making the distance B smaller than the distance A, fresh air can be efficiently flowed into the charger, so that ozone generated around the charger can be dispersed.

  According to the second aspect of the invention, the air flow in the process unit is guided to the second opening, so that the air can be efficiently returned to the original flow path. Therefore, the same air does not stay in the process unit.

  According to the invention described in claim 3, the recovery member serves as a guide for guiding the air flow to the second opening. Therefore, the air in the charger can be efficiently returned to the original flow path without providing a dedicated guide member such as a rib.

  According to the fourth aspect of the present invention, the flow path near the second opening is narrowed by bringing the wall side closer. Since the process unit side is not projected to narrow the flow path, the process unit is prevented from interfering with members in the image forming apparatus when the process unit is attached or detached. Therefore, the process unit can be easily attached and detached.

  According to the fifth aspect of the present invention, since the air flow is drawn by the exhaust fan, the air flow in the charger can be dispersed efficiently. In addition, it is possible to prevent the ozone from staying in the casing and to discharge the heat generated in the image forming apparatus main body.

It is principal part sectional drawing of a laser printer. FIG. 6 is an explanatory view showing a configuration of an air flow path 62 in the vicinity of the charger 29. 6 is a graph showing the relationship between the ratio B / A between the distance B and the distance A and the flow rate of air flowing from the flow path 62 through the first opening 54 into the charger 29. 6 is a graph showing a relationship between a ratio B / A between a distance B and a distance A and a flow rate of air returned from a charger 29 through a second opening to a flow path 62. It is the figure which showed the flow of the air around a charger.

[Schematic configuration of laser printer 1]
First, the overall configuration of a laser printer as an example of the image forming apparatus of the present invention will be briefly described.
In the drawings to be referred to, FIG. 1 is a side sectional view showing an embodiment of a laser printer as an example of an image forming apparatus of the present invention.

As shown in FIG. 1, the laser printer 1 forms an image on a feeder unit 4 for feeding paper 3 into a main body housing 2 as an image forming apparatus main body of the present invention, and on the fed paper 3. An image forming unit 5 is provided.
In the following description, the right side in FIG. 1 is referred to as the front side (the user side when using the laser printer 1), and is referred to as the left side and the back side.

  The feeder unit 4 is provided at the bottom of the main body housing 2 and accommodates the paper 3. The sheets 3 are fed one by one from the feeder unit 4, pass through various rollers, and then conveyed to the image forming unit 5.

  The image forming unit 5 includes a scanner unit 16, a process cartridge 17, a fixing unit 18, and the like. The scanner unit 16 is provided at an upper portion in the main body housing 2 and includes a laser light emitting unit (not shown), various lenses around the polygon mirror 19 that is driven to rotate, various mirrors, and the like. The lower wall 16 a of the scanner unit 16 faces the casing 50 of the process cartridge 17.

  The laser beam based on the image data emitted from the laser light emitting unit is reflected by the polygon mirror 19 as shown by a chain line, and passes or reflects through various lenses and mirrors, on the surface of the photosensitive drum 27 of the process cartridge 17. Irradiated at high speed.

  The process cartridge 17 as an example of the process unit of the present invention is disposed below the scanner unit 16 with a predetermined space interposed therebetween, and is configured to be detachably attached to the main body housing 2. The process cartridge 17 is mainly composed of a developing cartridge 28 and a drum unit 51.

  The developing cartridge 28 is detachably attached to the drum unit 51 and includes a developing roller 31, a layer thickness regulating blade 32, a supply roller 33, and a toner hopper 34. The toner in the toner hopper 34 is supplied to the developing roller 31 by the supply roller 33, and at this time, the toner is positively frictionally charged between the supply roller 33 and the developing roller 31.

  The toner supplied onto the developing roller 31 enters between the layer thickness regulating blade 32 and the developing roller 31 as the developing roller 31 rotates, and is carried on the developing roller 31 as a thin layer having a constant thickness. The

  The drum unit 51 mainly includes a photosensitive drum 27, a scorotron charger 29 as an example of a charger, a cleaning blade 56, and a transfer roller 30 in a casing 50.

  The photosensitive drum 27 is rotatably supported by the casing of the drum unit 51. The photosensitive drum 27 has a drum body grounded and a surface portion formed of a positively chargeable photosensitive layer. An exposure window 51 a formed in the shape of a hole in the casing of the drum unit 51 is disposed above the photosensitive drum 27.

  The scorotron charger 29 extends along the direction of the rotation axis of the photosensitive drum 27, and is located obliquely above the photosensitive drum 27 (specifically, on the back side and on the upper side of the photosensitive drum 27). So as not to come into contact with each other. The scorotron charger 29 (hereinafter also simply referred to as “charger 29”) is a positively-charged scorotron charger mainly composed of a charging wire 52 such as tungsten and a grid 58. The charging wire 52 is configured to generate corona discharge and uniformly charge the surface of the photosensitive drum 27 to a positive polarity.

  A first opening 54 is formed in the casing 50 obliquely above the charging wire 52. The first opening 54 is formed along the extending direction of the charging wire 52 in the width direction of the laser printer 1. In the charger 29, ion wind generated by corona discharge is generated in a direction from the charger 29 through the grid 58 toward the photosensitive drum 27.

  The transfer roller 30 is disposed below the photosensitive drum 27 so as to face and contact the photosensitive drum 27, and is rotatably supported by the casing of the drum unit 51. A transfer bias is applied to the transfer roller 30 by constant current control during transfer.

  The cleaning blade 56 as an example of the recovery member of the present invention is disposed on the downstream side of the transfer roller 30 and the upstream side of the charger 29 in the rotation direction indicated by the arrow A of the photosensitive drum 27, and one end is fixed to the casing 50. A plate-like member having substantially the same length as that of the photosensitive drum 27 in the width direction. Further, the other end of the cleaning blade 56 is in contact with the surface of the photosensitive drum 27, and foreign matter such as transfer residual toner attached to the surface of the rotating photosensitive drum 27 can be scraped off.

  In the casing 50, a second opening 55 is formed downstream of the cleaning blade 56 and upstream of the charger 29 in the rotational direction of the photosensitive drum 27. Similarly to the first opening 54, the second opening 55 is formed along the extending direction of the charging wire 52 in the width direction of the laser printer 1, and the space in the drum unit 51, the flow path 62, and the like. Is communicated.

  The surface of the photosensitive drum 27 is uniformly positively charged by the charger 29 and then exposed by high-speed scanning of the laser beam from the scanner unit 16. Thereby, the potential of the exposed part is lowered, and an electrostatic latent image based on the image data is formed. Here, the “electrostatic latent image” refers to an exposed portion of the surface of the photosensitive drum 27 that is uniformly positively charged and exposed to a laser beam to have a lowered potential.

  Next, when the developing roller 31 rotates, the toner carried on the developing roller 31 is supplied to the electrostatic latent image formed on the surface of the photosensitive drum 27 when it contacts the photosensitive drum 27. . The toner is visualized by being selectively carried on the surface of the photosensitive drum 27, whereby a toner image is formed by reversal development.

  Thereafter, the photosensitive drum 27 and the transfer roller 30 are rotationally driven so as to sandwich and convey the sheet 3 between them, and the sheet 3 is conveyed between the photosensitive drum 27 and the transfer roller 30, so The toner image carried on the surface of the drum 27 is transferred onto the paper 3.

  The fixing unit 18 is disposed on the downstream side of the process cartridge 17, and includes a heating roller 41 and a pressing roller 42 that is disposed to face the heating roller 41 and presses the heating roller 41. In the fixing unit 18 configured as described above, the toner transferred onto the sheet 3 is thermally fixed while the sheet 3 passes between the heating roller 41 and the pressing roller 42. The sheet 3 on which the toner transferred onto the sheet is thermally fixed by the fixing unit 18 is conveyed to a discharge roller 45 disposed on the downstream side of the fixing unit 18, and the discharge roller 45 onto the discharge tray 46. Sent out.

  Further, an exhaust fan 60 is provided between the fixing unit 18 and the scanner unit 16 as an air flow generating means of the present invention in order to release the heat in the apparatus to the outside. Further, a duct wall 61 is provided below the exhaust fan 60 and between the fixing unit 18 and the process cartridge 17 so as to face the casing 50 of the drum unit 51. By doing so, a flow path 62 through which air flows is formed between the duct wall 61 and the lower wall 16 a of the scanner unit and the casing 50. The length of the flow path 62 in the rotation axis direction (width direction) of the photosensitive drum 27 is constant. In the present embodiment, the wall portion of the present invention includes a duct wall 61 and a lower wall 16a of the scanner unit 16.

As described above, when the exhaust fan 60, the duct wall 61, the lower wall 16a of the scanner unit 16 and the casing 50 constitute the flow path 62 and the exhaust fan 60 is driven, an air flow is generated in the flow path 62. Further, the air between the drum unit 51 and the fixing unit 18 is sucked so as to be drawn to the exhaust fan 60 directly or through the flow path 62 and then discharged to the outside. Further, air between the process cartridge 17 and the scanner unit 16 is sucked into the exhaust fan 60 through the flow path 62 and then discharged to the outside. Furthermore, since the exhaust fan 60 sucks in air heated near the fixing unit 18 and discharges it to the outside, it also has a role of exhaust heat in the main body housing 2.
[Configuration around the flow path]
Next, the structure around the flow path 62 will be described in detail with reference to FIG. As shown in FIG. 2, an air flow path 62 is formed above the process cartridge 17 by a casing 50 and a duct wall 61 and a lower wall 16 a of the scanner unit 16 facing the casing 50.

  The casing 50 is formed so as to surround the photosensitive drum 27 in order to dispose the charger 29 and the cleaning blade 56 around the photosensitive drum 27. That is, the casing 50 is bent downward (gravity direction) on the way from the first opening 54 to the second opening 55, and the downstream side of the flow path 62 faces downward. Further, the second opening 55 is formed at a site from when the casing 50 is bent until it reaches a site where the cleaning blade 56 is fixed.

  By arranging each part in this manner, the air in the flow path 62 is drawn in the direction of the arrow by driving the exhaust fan 60 (see FIG. 1). Further, a part of the air that has flowed in from the upstream side of the air flow (on the exposure window 51a side in the flow path 62) passes through the flow path 62 as it is from the first opening 54 to the second opening 55. The flow partly branches at the first opening 54 and enters the charger 29. The air in the drum unit 51 is drawn into the flow path 62 through the second opening 55 by the exhaust fan 60.

  The flow path 62 is formed such that the distance B from the second opening 55 to the duct wall 61 is smaller than the distance A from the first opening 54 to the duct wall 61. Specifically, the duct wall 61 provided so as to face the casing 50 is formed to bend toward the casing 50 on the upstream side in the air flow direction with respect to the bent portion of the casing 50. As a result, the duct wall 61 comes close to the casing 50 and the flow path 62 near the second opening 55 is narrowed.

  By configuring the flow path 62 as described above, the following operation occurs. In the flow path 62, when the distance from the casing 50 to the duct wall 61 changes, the flow velocity of that part changes. That is, the flow velocity of the air flowing near the second opening 55 located on the downstream side is faster than the flow velocity of the air flowing near the first opening 54 located on the upstream side in the flow path 62.

  Accordingly, the pressure of air near the second opening 55 located downstream is lower than the pressure near the first opening 54 located upstream of the air flow. Then, due to the pressure difference, the flow rate of air passing through the first opening 54 and flowing into the charger 29 and flowing into the second opening 55 increases.

  The air flowing into the charger 29 from the flow path 62 through the first opening 54 forms an air flow toward the second opening 55 having a low pressure together with ozone generated in the vicinity of the charging wire 52. At this time, the air flow containing ozone is guided by the cleaning blade 56 and travels toward the second opening 55. Since the cleaning blade 56 is in contact with the photosensitive drum 27, the air flow containing ozone does not flow to the transfer roller side and moves toward the second opening 55 along the cleaning blade 56. Then, the air flow containing ozone is returned to the flow path 62 through the second opening 55 and discharged out of the drum unit 51.

  In the present embodiment, the following effects can be obtained. The flow path 62 is formed such that the distance B from the second opening 55 to the duct wall 61 is smaller than the distance A from the first opening 54 to the duct wall 61. The flow rate of air passing through the opening 54 and flowing into the charger 29 and flowing to the second opening 55 increases. Since fresh air can efficiently flow into the charger 29, ozone generated around the charger 29 can be dispersed.

  In particular, ozone has a greater specific gravity than air, and thus tends to accumulate in the charger 29. However, since fresh air actively flows into the charger 29 with the above-described configuration, ozone can be easily dispersed.

  Further, since the cleaning blade 56 guides the air in the process cartridge 17 to the second opening 55, the air in the charger 29 can be efficiently returned to the original flow path 62. Therefore, the same air does not continue to accumulate in the process cartridge 17 indefinitely. In addition, since the cleaning blade 56 also serves as a guide member, there is no need for a dedicated member (for example, forming a rib or the like) for guiding the air flow to the second opening 55, thereby reducing the manufacturing cost. Can be made.

  Furthermore, the flow path 62 in the vicinity of the second opening 55 is narrowed by bringing the duct wall 61 side closer. Since it is not necessary to project the flow path 62 toward the process cartridge 17 side, the process cartridge 17 is prevented from interfering with an apparatus (for example, a scanner unit) in the laser printer 1 when the process cartridge is attached or detached. Therefore, the process cartridge 17 can be easily attached and detached.

  Further, since the air flow is drawn by the exhaust fan 60, the air flow in the charger 29 can be dispersed efficiently. Moreover, since the air in the casing 50 is discharged out of the casing 50 by the exhaust fan 60, ozone is prevented from continuing to accumulate in the casing 50. At the same time, the heat generated in the main body housing 2 can be discharged.

  In addition, this invention is not limited to the said embodiment, It can utilize with a various form so that it may illustrate below. For example, in the above embodiment, the wall portion in the present invention is configured by the duct wall 61 and the lower wall of the scanner unit 16 to form the flow path 62, but the duct wall 61 is opposed to the casing 50, that is, The flow path may be formed so that the wall portion is configured only by the duct wall.

  In the above embodiment, the cleaning blade is used as the guide member. However, a cleaning roller arranged in contact with the photosensitive drum 27 may be used. Moreover, you may provide the rib which guides an airflow.

  In the above embodiment, a process cartridge that can be attached to and detached from the main body casing is applied as an example of the process unit. However, the process unit may be provided to the main body casing.

  In the embodiment, the exhaust fan is applied as the air flow generating means. However, an air supply fan that sends air to the flow path may be used.

  In the above-described embodiment, the present invention is applied to the laser printer. However, the present invention is not limited to this, and the present invention may be applied to other image forming apparatuses such as a copying machine and a multifunction machine.

  Examples of the above embodiment will be described below. Specifically, an embodiment showing an experimental result (simulation result) in which the relationship between the ratio B / A of the distance B and the distance A and the flow rate of air at a predetermined location is described.

In the experiment (simulation) according to this example, the exhaust fan 60, the charger 29, the first opening 54, the second opening 55, the cleaning blade 56, the duct wall 61, and the like are as in the above-described embodiment. Arranged. Other arrangements were the same as those of Brother Industries, Ltd. HL-2040. The exhaust flow rate by the exhaust fan 60 was 4.30 × 10 ⁻⁷ m ³ / s.

  Under such conditions, while the distance A is constant and the distance B is changed as shown in Table 1 below, the flow rate of air flowing from the first opening 54 to the charger 29 and the second opening The flow rate of air flowing from 55 to the flow path 62 was measured. As a result, experimental results as shown in Table 1 and FIGS. 3 and 4 were obtained. FIG. 5 shows the air flow around the charger 29 when B / A = 0.6.

  As described above, according to the present embodiment, the distance B from the second opening 55 to the duct wall 61 is smaller than the distance A from the first opening 54 to the duct wall 61 in the flow path 62. Thus, it was confirmed that the flow rate of air flowing from the flow path 62 to the charger 29 via the first opening 54 and the flow rate of air flowing from the second opening 55 to the flow path 62 were increased. Furthermore, it was confirmed that this tendency becomes more conspicuous as the distance B is made smaller (narrower) than the distance A. As described above, the flow path 62 is charged by making the distance B from the second opening 55 to the duct wall 61 smaller than the distance A from the first opening 54 to the duct wall 61. It was confirmed that fresh air can be efficiently introduced into the vessel 29.

  Further, as shown in FIG. 5, it was confirmed that the air was guided to the cleaning blade 56 in the process in which the air flowing into the charger 29 escapes to the second opening 55.

DESCRIPTION OF SYMBOLS 1 Laser printer 2 Main body housing | casing 17 Process cartridge 27 Photosensitive drum 29 Charger 50 Casing 54 1st opening part 55 2nd opening part 56 Cleaning blade 60 Exhaust fan 61 Duct wall 62 Flow path

Claims (5)

An image forming apparatus main body;
A casing of a process unit provided in the image forming apparatus main body and containing a photosensitive drum and a charger for charging the photosensitive drum;
A wall portion provided in the image forming apparatus main body so as to face the casing and forming a flow path with the casing;
An air flow generating means for generating an air flow in the flow path;
A first opening provided in the casing so as to be located upstream of the flow path and branch from the flow path so that air flows into the charger;
A second opening provided in the casing so as to return the air in the charger to the flow path, located on the downstream side of the flow path from the first opening;
With
The casing and the wall are
More than the distance A from the first opening to the wall so that the flow velocity of the air flow is greater near the second opening than near the first opening. An image forming apparatus characterized in that a distance B from the opening to the wall is reduced. The process unit is provided with a guide member for guiding the air in the charger to the second opening,
2. The second opening portion is provided downstream of the guide member in a direction in which the photosensitive drum rotates and upstream of the charger in the rotational direction of the photosensitive drum. The image forming apparatus described.   The image forming apparatus according to claim 2, wherein the guide member is a collection member that contacts the photosensitive drum and collects the developer on the photosensitive drum.   The process unit is detachable from the image forming apparatus main body, and the wall portion is close to the casing so as to restrict the flow path in the vicinity of the second opening. Item 4. The image forming apparatus according to any one of Items 1 to 3.   5. The image according to claim 1, wherein the air flow generation unit is an exhaust fan that sucks air from the second opening and draws it out of the main body of the image forming apparatus. Forming equipment.