Image forming apparatus

Abstract

To provide an image forming apparatus that can effectively prevent occurrence of cleaning failure and color shift caused by aggregation of paper powder and loading material to execute stable image formation.SOLUTION: A scraper with different contact pressures in a longitudinal direction against an intermediate transfer belt is provided downstream of a cleaning blade.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an image forming apparatus such as a copier, a printer, a facsimile, or a multifunction machine having a plurality of these functions. [Background technology]

[0002] As image forming devices become faster, the mainstream full-color image forming device is a configuration in which multiple image forming units are arranged in parallel corresponding to the belt member, and the image creation process for each color is performed in parallel. For example, in electrophotographic image forming devices, there is a full-color tandem system using an intermediate transfer belt.

[0003] The full-color tandem method is an image forming method that obtains a full-color image by multiple image forming units arranged side by side. Specifically, toner images of different colors formed by each image forming unit are superimposed on an intermediate transfer belt and are primarily transferred, and the toner images on the intermediate transfer belt are then collectively secondary transferred to a recording material. The toner images transferred to the recording material are then fixed by a fixing device. This type of full-color image forming apparatus is equipped with a cleaning device that removes residual toner remaining on the intermediate transfer belt after secondary transfer.

[0004] A cleaning blade made of an elastic material such as rubber bonded to a supporting metal plate is widely used as the cleaning device. In particular, the counter type, in which the cleaning blade is brought into contact with the intermediate transfer belt in the driving direction, is generally adopted because of its high cleaning performance.

[0005] On the other hand, when the recording material comes into contact with the intermediate transfer belt during the secondary transfer, paper dust and fillers may be transferred from the recording material to the intermediate transfer belt. It is known that such paper dust and fillers tend to aggregate at the edge of the cleaning blade, causing cleaning defects.

[0006] Therefore, Patent Document 1 discloses a configuration in which a scraper member is provided downstream of the cleaning blade in the moving direction of the intermediate transfer belt, and the toner that has slipped through the cleaning blade is collected by the scraper. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2002-278319 A Summary of the Invention [Problem to be solved by the invention]

[0008] However, in the configuration of Patent Document 1, since both the cleaning blade and the scraper come into contact with the intermediate transfer belt, the transport load on the intermediate transfer belt increases, and there is a possibility that "color shift" will occur, which deteriorates the registration of a color image.

[0009] The present invention has been made in consideration of these problems, and aims to provide an image forming apparatus that can perform stable image formation by suppressing both poor cleaning and color shift caused by aggregation of paper powder and fillers. [Means for solving the problem]

[0010] The image forming apparatus of the present invention comprises a plurality of image carriers, an intermediate transfer belt onto which toner images are transferred from the plurality of image carriers, a cleaning member that contacts the surface of the intermediate transfer belt to clean the intermediate transfer belt, a scraper member that is arranged downstream of the cleaning member in the movement direction of the intermediate transfer belt and contacts the intermediate transfer belt, and a transport member that is arranged upstream in the recording material transport direction of a transfer section that transfers toner from the intermediate transfer belt to a recording material and transports the recording material toward the transfer section, and is characterized in that the scraper member is configured so that in a width direction intersecting the movement direction of the intermediate transfer belt, the contact pressure in a predetermined region corresponding to the region where the transport member is arranged is lower than the contact pressure in other regions. Effect of the Invention

[0011] According to the present invention, it is possible to effectively prevent poor cleaning and color shift caused by the aggregation of paper powder and fillers, and to perform stable image formation. [Brief description of the drawings]

[0012] [Figure 1] 1 is a schematic diagram of an image forming apparatus according to an embodiment of the present invention; [Diagram 2] FIG. 2 is an explanatory diagram of a longitudinal arrangement of the image forming apparatus according to the embodiment. [Diagram 3] 1 is an explanatory diagram of the longitudinal distribution of the amount of paper dust and filler supplied to the intermediate transfer member cleaning blade 102. FIG. [Figure 4] 1A is a schematic diagram of a scraper 116 in the first embodiment, and FIG. 1B is an explanatory diagram of contact pressure distribution. [Diagram 5] 11A is a schematic diagram of a scraper 116 in the second embodiment, and FIG. 11B is an explanatory diagram of contact pressure distribution. [Figure 6] 11A is a schematic diagram of a scraper 116 in the third embodiment, and FIG. 11B is an explanatory diagram of contact pressure distribution. [Figure 7] 1A and 1B are diagrams illustrating the occurrence of cleaning defects and color misregistration. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In this embodiment, only the main parts related to the formation / transfer of a toner image will be described, but the present invention can be embodied in various applications such as printers, various printing machines, copiers, FAX machines, and multifunction machines by adding necessary devices, equipment, and housing structures.

[0014] <Description of Image Forming Apparatus> Fig. 1 is an explanatory diagram of the configuration of an image forming apparatus. As shown in Fig. 1, image forming apparatus 100 is a tandem type intermediate transfer type full-color printer in which image forming units 109Y, 109M, 109C, and 109Bk for yellow, magenta, cyan, and black are arranged along intermediate transfer belt (ITB) 101.

[0015] In image forming unit 109Y, a yellow toner image is formed on a photosensitive drum serving as an image carrier, and this yellow toner image is transferred to intermediate transfer belt 101 serving as another image carrier. In image forming unit 109M, a magenta toner image is formed in a similar procedure to that of image forming unit 109Y, and is transferred and superimposed on the yellow toner image on intermediate transfer belt 101. In image forming units 109C and 109Bk, a cyan toner image and a black toner image are formed in a similar procedure to that of image forming unit 109Y, and are transferred and superimposed in order onto intermediate transfer belt 101.

[0016] The four-color toner images carried on the intermediate transfer belt 101 are transported to a secondary transfer section T2 and are collectively (secondarily) transferred onto a recording material P. The recording material P onto which the four-color toner images have been (secondarily) transferred is separated from the intermediate transfer belt 101 by curvature and sent to a fixing device 112. The fixing device 112 heats and presses the recording material P with a fixing roller 112a and a pressure roller 112b to melt the toner and fix the image onto the surface. Thereafter, the recording material P is discharged outside the apparatus body.

[0017] The image forming units 109Y, 109M, 109C, and 109Bk are substantially identical in configuration, except that the colors of toner used in the respective developing devices are different: yellow, magenta, cyan, and black. In the following, the toner image forming process of the black image forming unit 109Bk will be described, and duplicated descriptions of the other image forming units 109Y, 109M, and 109C will be omitted. Also, the symbols Y, M, C, and Bk representing the toner colors yellow, magenta, cyan, and black will be omitted as appropriate.

[0018] The image forming unit 109Bk includes a photosensitive drum 103, a charging roller 104, an exposure device 105, a developing device 106, a primary transfer roller 107, and a photosensitive drum cleaning blade 108 arranged around the photosensitive drum 103.

[0019] The photosensitive drum 103 has a photosensitive layer with a negative charging polarity formed on the surface of an aluminum tube, and is driven by a motor (not shown) in the direction of the arrow at a process speed of 0.3 m / s.

[0020] A negative DC voltage is applied to the charging roller 104, which negatively charges the surface of the photosensitive drum 103. The exposure device 105 writes an electrostatic image of an image on the surface of the photosensitive drum 103 by scanning a laser beam that is ON-OFF modulated based on scanning line image data obtained by developing a black separated color image, using a rotating mirror.

[0021] The developing device 106 frictionally charges a two-component developer containing a negatively charged non-magnetic toner and a magnetic carrier using an agitating member. The developer is transported by a transport member and carried on a developing sleeve. The developer carried on the developing sleeve has its thickness regulated by a regulating blade, and is then transported to a portion facing the photosensitive drum 103. The developing sleeve is held at a predetermined distance from the photosensitive drum 103. By applying an oscillating voltage, which is an AC voltage superimposed on a negative DC voltage, to the developing sleeve, the negatively charged toner is transferred to the exposed portion of the photosensitive drum 103, which has become relatively positive, and the electrostatic image is reversed and developed.

[0022] The toner used in this embodiment may be a known toner in which a coloring material, a charge control material, etc., is added to a binder resin. The toner may preferably have a volume average particle size of 5 μm or more and 15 μm or less. In this embodiment, toner with a volume average particle size of 6 μm is used for all colors of yellow, magenta, cyan, and black.

[0023] The primary transfer roller 107 forms a primary transfer portion T1 between the photosensitive drum 103 and the intermediate transfer belt 101. By applying a positive DC voltage to the primary transfer roller 107, the toner image carried on the photosensitive drum 103 is primarily transferred to the intermediate transfer belt 101.

[0024] The photoconductor cleaning blade 108 comes into contact with the photoconductor drum 103 so as to face the driving direction of the photoconductor drum 103, and collects the untransferred toner remaining on the photoconductor drum 103. The photoconductor cleaning blade 108 is composed of a plate-shaped elastic member and a supporting metal plate, and the elastic member is made of, for example, urethane rubber with a hardness of 77° (JIS-A) and a thickness of 2 mm.

[0025] The secondary transfer roller 111 comes into contact with the outer surface of the intermediate transfer belt 101 at a position downstream of the image forming unit 109Bk in the movement direction of the intermediate transfer belt 101 and upstream of the intermediate transfer body cleaning blade 102. The secondary transfer roller 111 comes into contact with the intermediate transfer belt 101, the inner surface of which is supported by an opposing roller (drive roller) 110, to form a secondary transfer portion T2. ​​By applying a positive DC voltage to the secondary transfer roller 111, the full-color toner image carried on the intermediate transfer belt 101 is secondarily transferred to the recording material P.

[0026] The intermediate transfer member cleaning blade 102 as a cleaning member abuts against the intermediate transfer belt 101 in the moving direction thereof with the tension roller 115 facing it, and collects the untransferred toner remaining on the intermediate transfer belt 101. The intermediate transfer member cleaning blade 102 is composed of a plate-shaped elastic member as an elastic blade that abuts against the surface of the intermediate transfer belt 101 along the width direction that is approximately perpendicular to the moving direction of the surface of the intermediate transfer belt 101, and a supporting metal plate. The elastic member is made of, for example, urethane rubber with a hardness of 77° (JIS-A) and a thickness of 2 mm. The supporting metal plate as a regulating part that regulates the free length of the elastic member regulates the free length of the elastic member at the base end side opposite to the free end of the elastic member.

[0027] The scraper 116 as a scraper member is provided downstream of the intermediate transfer member cleaning blade 102 in the moving direction (rotation direction) of the intermediate transfer belt 101 and upstream of the image forming unit 109Y so as to face the moving direction of the intermediate transfer belt 101. The scraper 116 contacts the intermediate transfer belt 101 to collect the transfer residual toner remaining on the intermediate transfer belt 101. The scraper 116 is composed of a plate-shaped inelastic member 116a as a contact member and a support member 116b. Metal or resin is used as the plate-shaped inelastic member 116a. The support member 116b is a regulating portion that regulates the free length of the inelastic member 116a in a direction intersecting with the width direction of the inelastic member 116a. The support member 116b regulates the free length of the inelastic member 116a at the base end side opposite to the free end of the inelastic member 116a. In this embodiment, the scraper 116 is brought into contact with the intermediate transfer belt 101 opposite the tension roller 115, but the opposing member may be a separate member, or the scraper 116 may be brought into contact with the intermediate transfer belt 101 at a position where there is no opposing member.

[0028] The intermediate transfer belt 101 is a belt member that is driven to be transported in the direction of the arrow R, and is tensioned by a drive roller 110 that is a drive member, tension rollers 113 and 114 that are tension members, and a tension roller 115 that applies a predetermined tension to the intermediate transfer belt 101. The drive roller 110 also functions as a secondary transfer inner roller disposed in the secondary transfer portion T2. ​​However, the number of rollers that tension the intermediate transfer belt 101 is not limited to the configuration in FIG. 1.

[0029] <Explanation of longitudinal arrangement> Fig. 2 is an explanatory diagram of the longitudinal arrangement of the main elements of the image forming apparatus 100. As shown in Fig. 2, the longitudinal width of the intermediate transfer body cleaning blade 102 and the scraper 116 is set to be larger than the longitudinal width of the developing device 106. This makes it possible to clean the toner on the intermediate transfer belt 101 even if longitudinal positional deviation occurs due to meandering of the intermediate transfer belt 101. The longitudinal widths of the intermediate transfer body cleaning blade 102 and the scraper 116 are set to be equal.

[0030] In this embodiment, a paper feed roller as a transport member and a transport roller as a transport member are arranged upstream of the secondary transfer portion T2 in the recording material transport direction. The paper feed roller and the transport roller are configured to contact the recording material P and transport the recording material P toward the secondary transfer portion T2. ​​The paper feed rollers and the transport rollers for transporting the recording material P are arranged in a dispersed manner to accommodate recording materials of various sizes. However, the longitudinal arrangement and the number of the paper feed rollers and the transport rollers are not limited to the configuration in FIG. 2.

[0031] <Explanation of cleaning failure> At the secondary transfer portion T2, when the recording material P comes into contact with the intermediate transfer belt 101, paper powder and fillers may be transferred from the recording material P to the intermediate transfer belt 101. These paper powder and fillers tend to aggregate at the edge of the intermediate transfer member cleaning blade 102, and depending on the type of recording material, the aggregates may push up the intermediate transfer member cleaning blade 102, causing poor cleaning.

[0032] On the other hand, when the recording material P comes into contact with the paper feed roller or the transport roller, the paper powder and the filler are also detached from the recording material P. For this reason, the amount of paper powder and the filler supplied to the intermediate transfer member cleaning blade 102 has a longitudinal distribution in which the amount is small in the areas corresponding to the paper feed roller or the transport roller and is large in other areas, as shown in Fig. 3. Therefore, cleaning defects due to the aggregation of paper powder and the filler are unlikely to occur in the areas corresponding to the paper feed roller or the transport roller, but are likely to occur in other areas.

[0033] Here, any toner that has slipped past the intermediate transfer member cleaning blade 102 due to the aggregation of paper powder or filler is collected by the scraper 116, so that the toner that has slipped past the intermediate transfer member cleaning blade 102 does not soil the image.

[0034] <Explanation of color shift> However, when both the intermediate transfer body cleaning blade 102 and the scraper 116 come into contact with the intermediate transfer belt 101, the driving load on the intermediate transfer belt 101 increases, and this may cause a "color shift" that deteriorates the registration of a color image.

[0035] On the other hand, as described above, in the portion of the surface of the intermediate transfer belt 101 corresponding to the area where the paper feed roller and the transport roller are arranged, cleaning failure by the intermediate transfer body cleaning blade 102 due to aggregation of paper powder and filler is unlikely to occur. Therefore, it is possible to set the contact pressure of the scraper 116 against the intermediate transfer belt 101 low in the portion corresponding to the paper feed roller and the transport roller. That is, the scraper 116 is configured so that the contact pressure in a predetermined area corresponding to the area where the paper feed roller and the transport roller are arranged is lower than the contact pressure in other areas. By providing a portion with a low contact pressure in this way, the total pressure over the entire longitudinal area of ​​the scraper 116 can be reduced, thereby suppressing the occurrence of color misregistration.

[0036] As described above, by using a scraper with a low contact pressure set for the portion corresponding to the paper feed roller or the transport roller, it is possible to suppress both poor cleaning and color misregistration caused by the aggregation of paper powder and filler. In the following, in the examples, a specific configuration for setting the scraper contact pressure partially low will be described.

[0037] [Example 1] FIG. 4(a) is a schematic diagram of the scraper 116 in this embodiment, and FIG. 4(b) is an explanatory diagram of the contact pressure distribution of the scraper 116. As shown in FIG. 4(a), the scraper 116 in this embodiment has a longitudinal distribution in the free length (the length from the bonded part with the support member 116b to the free end) of the inelastic member 116a due to the shape of the support member 116b. As shown in FIG. 4(b), the support member 116b is shaped so that the free length of the portion corresponding to the feed roller and the transport roller is long. This allows the contact pressure of the portion corresponding to the feed roller and the transport roller to be set lower than the contact pressure of the other portions.

[0038] [Example 2] Fig. 5(a) is a schematic diagram of the scraper 116 in this embodiment, and Fig. 5(b) is an explanatory diagram of the contact pressure distribution of the scraper 116. As shown in Fig. 5(a), the scraper 116 in this embodiment has a longitudinal distribution in the thickness of the non-elastic member 116a. As shown in Fig. 5(b), the thickness of the non-elastic member 116a is thinner in the portions corresponding to the feed rollers and the transport rollers. This allows the contact pressure of the portions corresponding to the feed rollers and the transport rollers to be set lower than the contact pressure of the other portions.

[0039] [Example 3] Fig. 6(a) is a schematic diagram of the scraper 116 in this embodiment, and Fig. 6(b) is an explanatory diagram of the contact pressure distribution of the scraper 116. As shown in Fig. 6(a), the scraper 116 in this embodiment has a non-elastic member 116a that is divided into multiple parts in the longitudinal direction. As shown in Fig. 6(b), the non-elastic member 116a contacts the intermediate transfer belt 101 only in the portion that does not correspond to the feed roller or the transport roller. This allows the contact pressure of the portion that corresponds to the feed roller or the transport roller to be set lower than the contact pressure of the other portions.

[0040] <Explanation of cleaning failure and color misalignment occurrence> The scrapers 116 having the configurations of Examples 1, 2, and 3 were mounted on the image forming apparatus 100, and a continuous paper feed test was carried out to confirm the effects of the present invention. In addition, the continuous paper feed test was also carried out with a configuration without a scraper as Comparative Example 1, a configuration using a scraper with a low contact pressure set over the entire lengthwise area as Comparative Example 2, and a configuration using a scraper with a high contact pressure set over the entire lengthwise area as Comparative Example 3.

[0041] FIG. 6 shows the occurrence of cleaning failures and color shifts in the continuous paper feed test. As shown in FIG. 6, neither cleaning failures nor color shifts occurred in the configurations of Examples 1, 2, and 3. In the configuration of Comparative Example 1, no color shifts occurred, but cleaning failures occurred in areas not corresponding to the paper feed rollers or transport rollers, and minor cleaning failures occurred in the corresponding areas. In the configuration of Comparative Example 2, no color shifts occurred, and no cleaning failures occurred in areas corresponding to the paper feed rollers or transport rollers, but minor cleaning failures occurred in the non-corresponding areas. In addition, in the configuration of Comparative Example 3, no cleaning failures occurred in areas corresponding to the paper feed rollers or transport rollers, and in areas not corresponding to them, but color shifts occurred.

[0042] From the above results, it was confirmed that by using a scraper with a low contact pressure set for the parts that correspond to the paper feed roller and transport roller, it is possible to suppress both poor cleaning and color misalignment caused by the aggregation of paper powder and fillers. [Explanation of symbols]

[0043] 100 Image forming device 101 Intermediate transfer belt 102 Intermediate transfer member cleaning blade 103 Photosensitive drum 104 Charging roller 105 Exposure equipment 106 Developing device 107 Primary transfer roller 108 Photoconductor cleaning blade 109Y, 109M, 109C, 109Bk Image forming unit 110 Drive roller 111 Secondary transfer roller 112 Fixing device 113, 114 Tension roller 115 Tension roller 116 Scraper

Claims

1. A plurality of image carriers; an intermediate transfer belt onto which toner images are transferred from the plurality of image carriers; a cleaning member that comes into contact with a surface of the intermediate transfer belt to clean the intermediate transfer belt; a scraper member disposed downstream of the cleaning member in a moving direction of the intermediate transfer belt and in contact with the intermediate transfer belt; a conveying member disposed upstream of a transfer portion that transfers toner from the intermediate transfer belt to a recording material in a recording material conveying direction, the conveying member conveying the recording material toward the transfer portion, An image forming apparatus characterized in that the scraper member is configured so that, in a width direction intersecting the movement direction of the intermediate transfer belt, the contact pressure in a specified area corresponding to the area in which the conveying member is arranged is lower than the contact pressure in other areas.

2. The scraper member includes a regulating portion that regulates the free length of the scraper member on a base end side opposite to the free end of the scraper member in a direction intersecting the width direction of the scraper member, In a width direction intersecting the recording material transport direction, the scraper member has a free length in a specified area corresponding to the area in which the transport member is arranged which is a first length, and a free length in the other area which is a second length shorter than the first length.

3. The scraper member is provided in a region in which the transport member is disposed in a width direction intersecting with a recording material transport direction, but is not provided in the other region.

4. The transport member includes a plurality of rollers that contact the recording material in the width direction and transport the recording material.

Images