JP4748273B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus including a plurality of photoconductors and a plurality of cleaning rollers that are in sliding contact with the plurality of photoconductors.

  In general, as an image forming apparatus such as a laser printer, a plurality of developing units that respectively store toners of different colors, a plurality of photosensitive drums to which toner is supplied from each of the plurality of developing units via a developing roller, 2. Description of the Related Art A belt having a belt disposed facing a photosensitive drum and a plurality of transfer units that draw toner held on a plurality of photosensitive drums toward the belt is known. In this image forming apparatus, when the paper conveyed by the belt passes between each photosensitive drum and each transfer device, a transfer bias corresponding to the charging polarity of the toner is applied to each transfer device. The toners of different colors held on the photosensitive drum are attracted by the respective transfer devices and sequentially transferred onto the paper, and color printing on the paper is performed.

  In such an image forming apparatus, in order to prevent the toner that has not been attracted by the transfer device from remaining on the photosensitive drum, the toner remaining on the photosensitive drum after the transfer (hereinafter referred to as “transfer residual”). A toner that collects the transfer residual toner with a developing roller is known (see Patent Document 1). In addition, as a technique for collecting the transfer residual toner, the voltage applied to the cleaning roller that is in sliding contact with the photosensitive drum is changed so that the transfer residual toner is temporarily held by the cleaning roller, and at a predetermined timing from the cleaning roller. A technique is also known in which transfer residual toner is moved to a photosensitive drum and the transfer residual toner is collected by a developing roller.

Japanese Patent Laid-Open No. 5-53482

  By the way, in each of the above-described techniques, when the toner is transferred to the paper, if the paper dust adhering to the paper is transferred to the photosensitive drum, the subsequent transfer is hindered by the paper dust and can be performed satisfactorily. In some cases, it was necessary to provide a mechanism for collecting paper dust in each technique. However, in the technique of providing the cleaning roller described above, in addition to providing the cleaning roller in each developing device, if a mechanism for collecting paper dust is provided in each developing device, the entire apparatus becomes large. there were.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus that can collect paper dust satisfactorily and contribute to downsizing of the apparatus in an apparatus having a plurality of cleaning rollers.

The present invention that solves the above-described problems includes a plurality of photosensitive members that are arranged in parallel along the moving direction of the transfer target and on which an electrostatic latent image is formed, and a plurality of different types of developers that are supplied to the respective photosensitive members. And a plurality of cleaning rollers that slidably contact each of the plurality of photoconductors and collect at least one of paper dust and developer adhering to the photoconductors. A paper dust adsorption shaft that draws and adsorbs paper dust from the cleaning roller is provided only for the uppermost cleaning roller that is in sliding contact with the most upstream photoconductor in the moving direction of the transfer object, For the cleaning roller other than the most upstream side, the paper powder adsorption shaft is not provided, and the uppermost stream side cleaning roller is more than the ability to collect the developer. Cleaning roller other than the upstream side is higher towards the ability to recover the developer, a developing unit of the most upstream side, as compared with other developing units are configured to transfer residual developer is minimized It is characterized by.

  Here, when the image forming apparatus is a direct tandem system, the “transfer object” is a recording sheet such as paper or an OHP sheet, or a conveying means (conveying belt) for the sheet material. In the case of the transfer tandem system, it means an intermediate transfer member (intermediate transfer belt).

  According to the present invention, since the paper dust adsorption shaft is provided only on the most upstream side, it is possible to satisfactorily clean the uppermost photoreceptor on which the influence of the paper dust is maximized. Further, since the paper dust adsorption shaft is not provided for the cleaning rollers other than the cleaning roller on the most upstream side, the apparatus can be reduced in size.

  According to the present invention, the paper dust adsorption shaft is provided only on the most upstream side, and the paper dust adsorption shaft is not provided for any cleaning roller other than the cleaning roller on the most upstream side. The upstream photoconductor can be cleaned well and the apparatus can be miniaturized.

1 is a cross-sectional view illustrating an overall configuration of a color printer as an example of an image forming apparatus. It is an expanded sectional view which shows the structure of a process cartridge. FIG. 6 is a cross-sectional view (a) illustrating the operation of the cleaning mechanism during printing, and a cross-sectional view (b) illustrating the operation of the cleaning mechanism at a predetermined timing other than during printing.

<Overall configuration of color printer>
Next, embodiments of the present invention will be described in detail with reference to the drawings as appropriate. In the drawings to be referred to, FIG. 1 is a cross-sectional view showing the overall configuration of a color printer as an example of an image forming apparatus, and FIG. 2 is an enlarged cross-sectional view showing the structure of a process cartridge.

  In the following description, the direction will be described with reference to the user when using the color printer. That is, in FIG. 1, the left side toward the paper surface is “front side”, the right side toward the paper surface is “rear side”, the rear side toward the paper surface is “left side”, and the front side toward the paper surface is “right side”. To do. In addition, the vertical direction toward the page is defined as the “vertical direction”.

  As shown in FIG. 1, the color printer 1 includes, in a main body housing 10, a paper feed unit 20 that supplies paper P as an example of a transfer target, and image formation that forms an image on the fed paper P. The unit 30 and a paper discharge unit 90 that discharges the paper P on which an image is formed are provided.

  An upper cover 12 that can be opened and closed is provided on the upper portion of the main body housing 10 so as to be rotatable up and down with a hinge (not shown) provided on the rear side as a fulcrum. An upper surface of the upper cover 12 serves as a paper discharge tray 13 that accumulates the paper P discharged from the main body housing 10, and a plurality of holding members 14 that hold the LED units 40 are provided on the lower surface.

  The paper feeding unit 20 is provided in the lower part of the main body housing 10, and a paper feeding tray 21 that is detachably attached to the main body housing 10, and conveys the paper P from the paper feeding tray 21 to the image forming unit 30. A paper supply mechanism 22 is mainly provided. The paper supply mechanism 22 is provided on the front side of the paper supply tray 21 and mainly includes a paper supply roller 23, a separation roller 24, and a separation pad 25.

  In the paper feed unit 20 configured in this way, the paper P in the paper feed tray 21 is separated one by one and sent upward, and passes through between the paper dust removal roller 26 and the pinch roller 27 in the process. After the powder is removed, the direction is changed backward through the conveyance path 28 and supplied to the image forming unit 30.

  The image forming unit 30 mainly includes four LED units 40, four process cartridges 500, 50,..., A transfer unit 70, and a fixing unit 80.

  The process cartridge 50 (500) is arranged side by side in the front-rear direction between the upper cover 12 and the paper feed unit 20, and as shown in FIG. 2, the drum unit 51 (510) and the drum unit 51 (510) are arranged. And a developing cartridge 61 as an example of a developing unit that is detachably mounted.

  Each developing cartridge 61 has the same configuration except that the color of toner T as an example of the developer stored in the toner storage chamber 66 is different. Here, in the present embodiment, the black toner T with the least transfer remaining is accommodated in the developing cartridge 61 arranged on the most upstream side in the conveyance direction of the paper P.

  The drum unit 51 (510) has a structure in which only a part of the drum unit 510 arranged on the most upstream side in the transport direction of the paper P is different, and the other configurations are the same. Note that portions of the drum unit 510 different from the other drum units 51 will be described in detail later.

  The drum unit 51 (510) mainly includes a drum frame 52, a plurality of photosensitive drums 53 as an example of a plurality of photosensitive members rotatably supported by the drum frame 52, and a charger 54. The drum unit 510 located on the most upstream side in the transport direction of the paper P is provided with the first cleaning mechanism 100, and the other three drum units 51 are provided with the second cleaning mechanism 200, respectively. The first cleaning mechanism 100 and the second cleaning mechanism 200 will be described in detail later.

  The drum frame 52 is provided with a developing cartridge 61 so that an exposure hole 55 that faces the photosensitive drum 53 from the outside is formed. The LED unit 40 is inserted into the exposure hole 55 so as to face the upper surface of the photosensitive drum 53.

  The developing cartridge 61 includes a developing frame 62, a developing roller 63 and a supply roller 64 that are rotatably supported by the developing frame 62, and a layer thickness regulating blade 65, and includes a toner storage chamber 66 that stores toner T. ing.

  As shown in FIG. 1, the transfer unit 70 is provided between the paper feeding unit 20 and each process cartridge 50, and includes a driving roller 71, a driven roller 72, a conveyance belt 73, a transfer roller 74, and a cleaning unit 75. Mainly prepared.

  The driving roller 71 and the driven roller 72 are arranged in parallel in a spaced manner in the front-rear direction, and a conveyance belt 73 formed of an endless belt is stretched between them. The outer surface of the conveyance belt 73 is in contact with each photosensitive drum 53. In addition, four transfer rollers 74 that sandwich the conveyor belt 73 between the photosensitive drums 53 are arranged inside the conveyor belt 73 so as to face the photosensitive drums 53. A transfer bias is applied to the transfer roller 74 by constant current control during transfer.

  The cleaning unit 75 is disposed below the conveyance belt 73, and is configured to remove the toner T adhering to the conveyance belt 73 and to drop the removed toner T into the toner storage unit 76 disposed below the cleaning belt 75. .

  The fixing unit 80 is disposed on the rear side of each process cartridge 50 and the transfer unit 70, and includes a heating roller 81 and a pressure roller 82 that is disposed to face the heating roller 81 and presses the heating roller 81.

  In the image forming unit 30 configured as described above, first, the surface of each photosensitive drum 53 is uniformly charged positively by the charger 54 and then exposed to light emitted from each LED unit 40. As a result, the potential of the exposed portion is lowered, and an electrostatic latent image based on the image data is formed on each photosensitive drum 53.

  Further, the toner T in the toner storage chamber 66 is supplied to the developing roller 63 by the rotation of the supply roller 64, and enters between the developing roller 63 and the layer thickness regulating blade 65 by the rotation of the developing roller 63 and has a constant thickness. Is carried on the developing roller 63 as a thin layer. Here, the toner T carried on the developing roller 63 is frictionally charged positively between the supply roller 64 and the developing roller 63 or between the developing roller 63 and the layer thickness regulating blade 65.

  The toner T carried on the developing roller 63 is supplied to the electrostatic latent image formed on the photosensitive drum 53 when the developing roller 63 comes into contact with the photosensitive drum 53. As a result, the toner T is selectively carried on the photosensitive drum 53 to visualize the electrostatic latent image, and a toner image is formed by reversal development.

  Then, the paper P supplied onto the conveyor belt 73 passes between each photosensitive drum 53 and each transfer roller 74 disposed inside the conveyor belt 73, whereby the toner formed on each photosensitive drum 53 is obtained. The image is transferred onto the paper P. When the paper P passes between the heating roller 81 and the pressure roller 82, the toner image transferred onto the paper P is thermally fixed.

  The paper discharge unit 90 mainly includes a paper discharge side transport path 91 formed so as to extend upward from the outlet of the fixing unit 80 and to be reversed to the front side, and a plurality of pairs of transport rollers 92 that transport the paper P. I have. The paper P on which the toner image has been transferred and heat-fixed is transported through a paper discharge-side transport path 91 by a transport roller 92, discharged outside the main body housing 10, and accumulated in the paper discharge tray 13.

<Detailed structure of cleaning mechanism>
Next, details of the most upstream drum unit 510, the first cleaning mechanism 100, and the second cleaning mechanism 200 will be described.

  As shown in FIG. 2, the first cleaning mechanism 100 is provided only in the drum unit 510 on the upstream side in the conveyance direction of the paper P, and mainly includes a cleaning roller 110, a paper dust adsorption shaft 120, and a paper dust removing member 130. ing.

  The cleaning roller 110 is rotatably provided so as to be in sliding contact with the photosensitive drum 53, and temporarily collects paper dust and toner T adhering to the photosensitive drum 53. Specifically, the cleaning roller 110 is applied with a negative voltage during printing, so that the positive toner T (hereinafter referred to as “transfer residual”) that remains on the photosensitive drum 53 without being transferred from the photosensitive drum 53 to the paper P. Also referred to as “toner T”).

  Further, when a positive voltage larger than the potential on the surface of the photosensitive drum 53 is applied to the cleaning roller 110 at a predetermined timing other than during printing, the transfer residual toner T held by the cleaning roller 110 is exposed to light. Returned to the drum 53. At this time, a positive voltage higher than the surface potential of the developing roller 63 is applied to the photosensitive drum 53, so that a positive transfer residual toner T is transferred from the photosensitive drum 53 to the developing roller 63. Is recovered.

  Further, at this time, the negatively charged paper dust adhering to the photosensitive drum 53 is attracted and held by the cleaning roller 110 to which a positive voltage is applied.

  The paper dust adsorption shaft 120 is rotatably provided behind the cleaning roller 110, and draws and adsorbs the paper dust held on the cleaning roller 110. Specifically, during printing, a negative voltage whose absolute value is smaller than the negative voltage applied to the cleaning roller 110 is applied to the paper dust adsorption shaft 120. As a result, the potential of the paper dust adsorption shaft 120 becomes higher than the potential of the cleaning roller 110, so that the positive transfer residual toner T on the cleaning roller 110 does not move to the paper dust adsorption shaft 120 having a high potential, It is held on the cleaning roller 110 well.

  At a predetermined timing other than printing, a positive voltage larger than the positive voltage applied to the cleaning roller 110 is applied to the paper dust adsorption shaft 120. As a result, the potential of the paper dust adsorption shaft 120 becomes higher than the potential of the cleaning roller 110, so that the transfer residual toner T remaining on the cleaning roller 110 does not move to the paper dust adsorption shaft 120 and the cleaning roller 110. Only the negative paper dust adsorbed above is attracted to and held by the paper dust adsorption shaft 120 having a high potential.

  The paper dust removing member 130 is formed of an elastic member such as sponge or felt, and is provided on the rear upper side of the paper dust adsorption shaft 120 so as to be in sliding contact with the surface of the paper dust adsorption shaft 120. Therefore, when paper dust is adsorbed on the paper dust adsorption shaft 120, the paper dust is peeled off by the paper dust removing member 130 and dropped downward. A bottomed cylindrical paper dust reservoir 51 </ b> A for receiving falling paper dust is formed as a part of the drum unit 510 below the paper dust removing member 130.

  The second cleaning mechanism 200 is provided in each of the three drum units 51 other than the drum unit 510 on the most upstream side, and includes a cleaning roller 210. The cleaning roller 210 is rotatably provided so as to be in sliding contact with the photosensitive drum 53. When a voltage similar to that of the cleaning roller 110 of the first cleaning mechanism 100 is applied, the transfer roller attached to the photosensitive drum 53 is left behind. The toner T is temporarily collected.

  The cleaning roller 210 is formed with a diameter larger than the diameter of the cleaning roller 110 of the first cleaning mechanism 100. Accordingly, the ability of the cleaning roller 210 other than the most upstream side to collect the transfer residual toner T is higher than the ability of the cleaning roller 110 on the most upstream side to collect the transfer residual toner T.

  Next, the operation of the first cleaning mechanism 100 and the second cleaning mechanism 200 will be described with reference to FIG. In the drawings to be referred to, FIG. 3 is a cross-sectional view (a) showing the operation of the cleaning mechanism during printing, and a cross-sectional view (b) showing the operation of the cleaning mechanism at a predetermined timing other than during printing.

  As shown in FIG. 3A, during printing, when the paper P reaches between the uppermost photosensitive drum 53 and the transfer roller 74, a black toner image is transferred to the paper P therebetween. The At this time, the toner T that has not been attracted by the transfer roller 74 remains as the transfer residual toner T on the photosensitive drum 53, but this transfer residual toner T is positioned on the downstream side in the rotation direction of the photosensitive drum 53 and is negatively charged. It is collected by the cleaning roller 110. Here, as described above, a negative voltage whose absolute value is smaller than the negative voltage applied to the cleaning roller 110 is applied to the paper dust adsorption shaft 120. It is held on the paper powder adsorption shaft 120 without moving to any of the paper powder adsorption shaft 120.

  At this time, if paper dust PP negatively charged is generated from the paper P, the paper dust PP adheres to the positively charged photosensitive drum 53. The paper powder PP on the photosensitive drum 53 moves together with the photosensitive drum 53 without moving to the cleaning roller 110 charged negatively.

  The negative paper dust PP moving with the photosensitive drum 53 has a high potential on the surface of the photosensitive drum 53 when the surface of the photosensitive drum 53 is charged by the charger 54 and exposed by the LED unit 40 (see FIG. 1). It is held in the non-exposed part. Here, since the potential of the non-exposed portion is set to a value higher than the surface potential of the developing roller 63 (the potential of the toner T) so that the toner T does not move from the developing roller 63, the paper dust PP When the toner reaches the position of the developing roller 63, the negative paper powder PP remains held in the non-exposed portion having a higher positive potential than the developing roller 63. That is, the paper powder PP remains adhered on the photosensitive drum 53 during printing.

  At this time, the second and subsequent cleaning rollers 210 from the most upstream side collect the transfer residual toner T in the same manner as the above-described most upstream cleaning roller 110. Since the paper dust PP of the paper P is almost collected by the most upstream side photosensitive drum 53, the paper dust PP hardly adheres to the second and subsequent photosensitive drums 53 from the most upstream side.

  When a predetermined timing other than printing (for example, immediately after printing is completed), a positive voltage larger than the surface potential of the photosensitive drum 53 is applied to the cleaning roller 110 as described above, and the paper dust adsorption shaft 120 is applied. In addition, a positive voltage larger than the voltage applied to the cleaning roller 110 is applied. As a result, as shown in FIG. 3B, the transfer residual toner T on the cleaning roller 110 moves to the photosensitive drum 53 side, and is conveyed by the photosensitive drum 53 and has a lower potential than the photosensitive drum 53. It is collected at. Similarly, the remaining transfer toner T is also collected by the developing roller 63 via the photosensitive drum 53 in the second and subsequent cleaning rollers 210 from the most upstream side.

  At this time, the negative paper dust PP held on the uppermost photosensitive drum 53 moves onto the positive cleaning roller 110 and then has a higher potential than the cleaning roller 110. Move up 120. Then, the paper powder PP on the paper powder adsorption shaft 120 is peeled off by the paper powder removing member 130, falls downward, and is received by the paper powder reservoir 51A.

According to the above, the following effects can be obtained in the present embodiment.
Since the paper dust adsorption shaft 120 is provided in correspondence with the most upstream photosensitive drum 53, the most upstream photosensitive drum 53 that is most affected by the paper dust PP can be cleaned well. Further, since the paper dust adsorption shaft 120 is not provided on the second and subsequent sides from the most upstream side, the apparatus can be downsized.

  By accommodating the black toner T with the smallest transfer residue in the development cartridge 61 on the most upstream side, a large amount of the transfer residual toner T does not adhere to the photosensitive drum 53, so that the transfer by the cleaning roller 110 is performed. It is possible to efficiently collect the residual toner T and the paper powder PP. In addition, since a large amount of untransferred toner T does not adhere to the photosensitive drum 53, the cleaning roller 110 can be made small, and the paper dust adsorption shaft 120 and the paper dust removing member 130 can be disposed well.

  Since the toner collecting capability of the cleaning roller 210 other than the most upstream side is higher than the toner collecting capability of the cleaning roller 110 on the most upstream side, the toner T of a color other than black is supplied to supply the toner T of the most upstream side. The second and subsequent photosensitive drums 53 to which more transfer residual toner T adheres than the photosensitive drums 53 can be cleaned well.

  Since the diameter of the second and subsequent cleaning rollers 210 is larger than the diameter of the cleaning roller 110 on the most upstream side, a large amount of untransferred toner T on the second and subsequent photosensitive drums 53 can be recovered and held satisfactorily. The structure on the most upstream side where the paper powder adsorption shaft 120 is provided can be downsized.

Since the paper dust removing member 130 is provided, the paper dust PP can be reliably peeled off from the paper dust adsorption shaft 120.
Since the paper dust reservoir 51A is provided below the paper dust removing member 130, the paper dust PP can be stored well by the paper dust reservoir 51A.

In addition, this invention is not limited to the said embodiment, It can utilize with various forms so that it may illustrate below.
In the above embodiment, the present invention is applied to the color printer 1. 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.

In the above-described embodiment, the paper P such as a thick paper, a postcard, and a thin paper is used as an example of the transfer target. However, the present invention is not limited to this, and may be a conveyance belt, an intermediate transfer belt, or the like.
In the above-described embodiment, the photosensitive drum 53 is employed as the photosensitive member. However, the present invention is not limited to this, and for example, a belt-shaped photosensitive member may be employed.

In the above embodiment, the paper dust adsorption shaft 120 is provided only on the most upstream side, but the present invention is not limited to this, and if it is other than the most downstream side, for example, it is also provided on the second or third position from the most upstream side. Also good. That is, it is only necessary to provide a paper powder adsorption shaft for at least the most upstream cleaning roller other than the most downstream cleaning roller.
In the above-described embodiment, the developing cartridge 61 including the developing roller 63 and the like is employed as an example of the developing unit. However, the present invention is not limited to this, and only the toner storage chamber is formed without the developing roller and the like. A toner cartridge or the process cartridge 50, 500 in the above embodiment may be employed.

In the above-described embodiment, the black toner T is used as an example of the developer with the least transfer residue. However, the present invention is not limited to this, and a toner other than black is appropriately used depending on the type of toner. Also good.
In the above embodiment, the toner collection capacity of the second and subsequent cleaning rollers 210 is made higher than that of the cleaning roller 110 on the most upstream side by changing the diameters of the cleaning rollers 110 and 210. However, the present invention is not limited to this. Instead, for example, the toner collecting ability may be changed by changing the material of the roller.

DESCRIPTION OF SYMBOLS 1 Color printer 50,500 Process cartridge 51,510 Drum unit 53 Photosensitive drum 61 Developing cartridge 71 Drive roller 72 Followed roller 73 Conveyor belt 100 1st cleaning mechanism 110 Cleaning roller 120 Paper dust adsorption shaft 130 Paper dust removal member 200 2nd cleaning mechanism 210 Cleaning roller P Paper PP Paper dust T Toner

Claims (4)

A plurality of photoconductors that are arranged in parallel along the moving direction of the transfer target and on which an electrostatic latent image is formed;
A plurality of developing units each supplying different types of developer to each photoreceptor;
A plurality of cleaning rollers that slide in contact with each of the plurality of photoconductors and collect at least one of paper dust and developer adhering to the photoconductors,
A paper dust adsorption shaft that draws and adsorbs paper dust from the cleaning roller is provided only for the uppermost cleaning roller that is in sliding contact with the uppermost photosensitive member in the moving direction of the transfer body,
For the cleaning roller other than the most upstream side, the paper dust adsorption shaft is not provided,
The ability of the cleaning roller other than the most upstream side to collect the developer is higher than the ability of the upstreammost cleaning roller to collect the developer ,
The image forming apparatus, wherein the most upstream developing unit is configured such that a developer transfer residue is minimized as compared with other developing units . The image forming apparatus according to claim 1 , wherein a black developer is accommodated in the most upstream developing unit.   The image forming apparatus according to claim 1, further comprising a paper dust removing member that contacts the paper dust adsorption shaft and peels off the paper dust adsorbed on the paper dust adsorption shaft. The image forming apparatus according to claim 3 , further comprising a paper dust reservoir that stores the paper dust removed by the paper dust removing member.

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