JP2006138902A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus by which stable density detection is possible with little variation in density by stabilizing the distance between a density detecting means and an image carrier by preventing riding up of a belt member in a position carrying out a density detection by a density detecting means and soiling of a facing supporting roller. <P>SOLUTION: As shown in Fig 5, the width of the roller is made narrower than in other supporting rollers in the supporting roller 10 facing the density detecting means S and riding up on a guide is prevented at the supporting roller 510 and at the same time, a restricting member 512 is provided to prevent meandering of an intermediate transfer belt 501. Furthermore, A more stable density detection can be carried out by preventing variation in the diameter of the supporting roller 510 by providing a cleaning member 513 (Fig 7) for foreign matter/soiling attachment to the supporting roller 510 and a cleaning member 514 (Fig 8) cleaning a back surface of an intermediate transfer belt 501. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to an image forming apparatus such as a copying machine, a facsimile machine, and a printer, and more particularly to a transfer apparatus including an intermediate transfer member.

Conventionally, an image forming apparatus using a belt-shaped member as an image carrier or an intermediate transfer member is known. A system using a belt-like member is a system that is often used in recent years because it has a high degree of freedom in layout. Further, in general image forming apparatuses, a detection unit for detecting the amount of developer that forms an image, for example, toner in the case of electrophotography, is often provided, and a system using a belt-like member. In such a case, such a toner image adhesion amount detection may be performed on the belt-like member.
The belt-like member is usually rotated while being supported by a plurality of support rollers, and image formation is performed. For this reason, when uneven rotation of the belt-shaped member or meandering in a direction perpendicular to the rotation direction occurs, there arises a problem of image distortion or color misalignment. Therefore, for the meandering in the direction perpendicular to the rotation direction, there is a method for regulating the meandering of the belt on one side by providing a guide for regulating the meandering on the belt-shaped intermediate transfer member and hitting the support roller with the guide. Commonly used. In this case, the guide sometimes runs on the tension roller depending on the situation, but when it rides, the tension of the belt-like member on the riding section increases, so that it will naturally return after several turns. ing.

Meanwhile, in the recent market, the demand for image quality is very high, and the demand for density fluctuation is particularly severe. In particular, in a color image forming apparatus, even if the concentration of a part of the developer is slightly changed, it is easy to detect a difference in color as a human eye, which is likely to cause a problem. For this reason, in particular, in a color electrophotographic apparatus, it is general that density detection means is provided on an image carrier or an intermediate transfer body so that the density is controlled to be constant. The type of density detection means that is generally used is a type that detects reflected light. However, in such a type, the sensitivity changes as the distance between the density detection means and the image carrier changes. It is premised on detection at a position where the position of the carrier is fixed. Therefore, when a belt-like member is used, the density detection means is often installed at a position facing the support roller that supports the belt-like member.
However, conventionally, when such density detection is performed on a belt-shaped member, the following problems often occur. The problem is that when the above-mentioned riding phenomenon occurs at the timing of detection by the density detecting means, the distance between the belt-like member and the density detecting means changes depending on the way of riding, or the opposing support roller is soiled. Accumulation causes the distance between the belt-like member and the density detecting means to change, and accurate density control cannot be performed.

Patent Document 1 describes a device in which the distance between the end of the secondary transfer counter roller and the detent of the intermediate transfer belt is larger than that of the other rollers. With this method, it is possible to prevent contact between the roller adjacent to the position reading sensor and the detent. However, there is a disadvantage in that it is disadvantageous with respect to the belt meandering prevention in the vicinity of the roller. Further, the problem that the distance to the density detecting means changes due to dirt or foreign matter adhering to the opposing support roller has not been solved.
Japanese Patent Laid-Open No. 2000-231283

The present invention has been made in view of the above problems, and an object of the present invention is to prevent density detection means by preventing the belt-like member from running on the position where density detection is performed by the density detection means and contamination of the opposing support roller. It is an object of the present invention to provide an image forming apparatus in which the distance between the image carrier and the image carrier is stabilized, whereby stable density detection is possible and density fluctuation is small.

As means for solving the above problems, the present invention has the following features.
2. The image forming unit according to claim 1, comprising at least three supporting rollers and an image carrier supported by the supporting rollers, and the image forming unit or the image forming apparatus main body side where the image forming unit is introduced and installed. In the image forming unit in which the width of the support roller at a position facing the detection means for detecting the image density provided in is smaller than the width of the other support rollers,
When the image forming unit is installed in the main body of the image forming apparatus, a meandering regulating member for regulating the meandering of the image carrier is installed on both sides of the image carrier at a position facing the image density detecting means. It is characterized by being.
According to a second aspect of the present invention, the image forming unit further includes a cleaning member for the support roller at a position facing the image density detecting unit.
The image forming unit according to claim 3, further comprising a cleaning member that contacts and cleans the back side of the image carrier at a position upstream of the support roller at a position facing the image density detection unit. It is characterized by that.

As described above, according to the means for solving the above problem, the image forming unit according to the present invention can prevent the image carrier from riding on the support roller and perform accurate density detection, and the image with stable density. A forming apparatus can be provided.
Further, in the image forming unit of the present invention, it is possible to accurately detect the density by preventing the diameter change of the support roller, and to provide an image forming apparatus having a stable density.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows an embodiment in which the present invention is employed as a belt-shaped intermediate transfer member as an image carrier, and is an electrophotographic apparatus of a tandem type intermediate transfer system.
In the figure, reference numeral 1 is a tandem image forming apparatus, 2 is a writing optical apparatus, 3 is a paper feed table that supports the whole, 4 is a conveying / reversing apparatus, and 5 is a fixing apparatus that finally fixes an image to a transfer material. ing.

FIG. 2 is an enlarged view of the image forming portion of this figure. The tandem image forming apparatus 1 is provided with an endless belt-shaped intermediate transfer member 501 at the center. The intermediate transfer member 501 is made of rubber or resin having a single layer or multilayer structure.
The intermediate transfer member 501 is stretched by a secondary transfer bias roller 502 and support rollers 503, 508, 509, and 510, and can rotate counterclockwise in the illustrated example. Among these, an intermediate transfer body cleaning device 520 for removing residual toner remaining on the intermediate transfer body 501 after image transfer is provided on the left of the support roller 509.
The intermediate transfer body 501 and the intermediate transfer body cleaning device 520 are an integral unit, and when the unit life is reached, only the unit portion can be replaced from the apparatus main body. Further, on the opposite side of the support roller 510, density detecting means S is provided on the apparatus main body side.

The secondary transfer bias roller 502 can form an electric field of both positive and negative polarities by the secondary transfer electric field forming unit 901, and the secondary transfer roller is provided on the opposite side of the intermediate transfer body 501. 600 is installed.
Further, inside the intermediate transfer member 501 between the support roller 503 and the support roller 508, primary transfer bias rollers 504, 505, 506, and 507 that form an electric field at the time of primary transfer can contact the intermediate transfer member 501. Is arranged in.
Then, on the opposite side of the primary transfer bias rollers 504, 505, 506, and 507 across the intermediate transfer member 501, four photosensitive members 101, 102, and 103 of yellow, cyan, magenta, and black are arranged along the conveyance direction. , 104 are arranged side by side to constitute a tandem image forming apparatus.
Around each of the photoconductors 101 to 104, photoconductor charging units 201 to 204, photoconductor cleaning units 301 to 304, and developing units 401 to 404 are arranged, respectively. Write exposure on the photoconductor is performed by laser irradiation with an exposure device (not shown) at a position between the photoconductor charging units 201 to 204 and the developing units 401 to 404.
Under the secondary transfer roller 600, a registration roller 800 for feeding the transfer material to the secondary transfer unit is installed, and a fixing device 700 for fixing the image on the transfer material is provided above.

Now, when making a copy using this color electrophotographic apparatus, an image signal is first input from a personal computer or a scanner (not shown). At a predetermined timing after the signal is input, the photosensitive members 101 to 104 and the intermediate transfer member 501 are rotated by a drive motor (not shown).
Simultaneously with the photoconductors 101 to 104, a preliminary cleaning operation by the photoconductor cleaning units 301 to 304 is performed, and thereafter, a charging operation by the photoconductor charging units 201 to 204, an exposure operation by an exposure unit (not shown), and developing units 401 to 404. The developing operation is performed. The toner images formed on the photoconductors 101 to 104 in this way are formed on the intermediate transfer member 501 by forming an electric field having a polarity opposite to that of the toner on the primary transfer bias rollers 504 to 507 at predetermined timings, respectively. Transferred to form a single or multicolor visible image.

On the other hand, at a predetermined timing after the input of the image signal, the transfer material is fed out from a paper feed table (not shown), and abuts against the registration roller 800 to stop. Then, the registration roller 800 is rotated in synchronization with the visible image on the intermediate transfer member 501, and a transfer material is fed between the intermediate transfer member 501 and the secondary transfer roller 600.
At the same time, an electric field having the same polarity as the toner is formed on the secondary transfer bias roller 502 by the secondary transfer electric field forming means, and the visible image on the intermediate transfer member 501 is secondarily transferred to the transfer material.
Thereafter, the transfer material passes through the fixing device 700, and heat and pressure are applied to fix the visible image on the transfer material.
On the other hand, the intermediate transfer body 501 after the image transfer is removed by the intermediate transfer body cleaning device 520 to remove residual toner remaining on the intermediate transfer body 501 after the image transfer, to prepare for the image formation again.

Next, density detection control will be described.
The adjustment mode for performing density detection is performed when the power is turned on, when a predetermined number of sheets elapses, when a predetermined time elapses, or at an arbitrary timing. When density detection is performed, a 25 mm × 20 mm test patch is formed on the photoconductors 101 to 104. The test patches on the photoconductors 101 to 104 are primarily transferred onto the intermediate transfer member 501, and the test patches primarily transferred onto the intermediate transfer member 501 pass through a secondary transfer portion separated from the intermediate transfer member 501. Then, the density is detected by the density detecting means S installed at the position of the stretching roller 510. Then, based on the detection result, it is determined whether the current image density is light or dark, and information is fed back to toner supply, charging conditions, development conditions, and the like, and adjustment is performed to obtain a predetermined density. The test patch after the density detection is cleaned by the intermediate transfer member cleaning device 520.

At this time, in the prior art, when the guide of the intermediate transfer belt 501 rises at the position of the support roller 510, the distance between the density detection means S and the intermediate transfer belt 501 changes, and accurate density detection is performed. There was a problem that could not be performed (FIG. 3).
Therefore, as a countermeasure, the width of the support roller 510 facing the density detection means S is made smaller than that of the other support rollers. The details are as shown in FIG. 4, while the other support rollers have less play between both sides of the meandering prevention guide, whereas the width of the support roller 510 is such that the meandering restriction guide 511 does not ride on. Is made smaller. Accordingly, the distance between the density detection unit S and the intermediate transfer belt 501 can be kept constant by preventing the guide roller from climbing on the support roller 510 which is the position opposite to the density detection unit.
However, regarding the meandering behavior of the intermediate transfer belt 501 near the support roller 510, both sides of the support roller 510 are regulated by the support roller 502 and the support roller 509, but the distance between the support roller 502 and the support roller 509 is long. In such a case, preventing the meandering of the intermediate transfer belt 501 has been a problem.
In the present invention, the regulating member 512 is provided at the support roller 510 portion so that the intermediate transfer belt 501 does not meander. This is shown in FIG. 5 where a regulating member 512 is provided so that the both sides of the intermediate transfer belt 501 are regulated so as not to meander. In particular, in the case of an apparatus that performs color registration correction of a color image by the density detection means S, it is desirable to provide a regulating member 512.

Further, since the support roller 510 facing the density detecting unit stretches the intermediate transfer belt 501, if foreign matter or the like entering the apparatus adheres to the back surface of the intermediate transfer belt 501, the support roller 510 re-applies to the support roller 510 from there. As a result of adhesion and overlap, the support roller 510 becomes uneven, and in the prior art, the distance between the density detecting means S and the intermediate transfer belt 501 becomes unstable, and density detection cannot be performed accurately. (FIG. 6).
In the present invention, by providing the cleaning member 513 against foreign matter / dirt adhesion to the support roller 510, the diameter variation of the support roller 510 can be prevented and more stable density detection can be performed. As the cleaning member 513, as shown in FIG. 7, a rubber blade member or the like is used. In addition to the rubber blade member, a brush member or a mylar member can also be used.
It is noted that the sensitivity of the density detection means is deviated from contamination of the instruction roller 510, but the contamination is mainly attached via the intermediate transfer belt 501 as described above, and a member for cleaning the back surface of the intermediate transfer belt 501 is used. By providing it, it is possible to indirectly prevent the support roller 510 from being soiled. Accordingly, instead of providing the cleaning member 513 on the support roller 510, it is also effective to provide a cleaning member 514 that cleans the back surface of the intermediate transfer body 501 upstream of the support roller 510 in the rotation direction of the intermediate transfer body 501. (FIG. 8). When the cleaning members 513 and 514 are used, it is also necessary to prevent reattachment to the intermediate transfer belt 501 by providing a tray that receives the cleaned foreign matter and dirt.

Next, more specific conditions of the embodiment will be described. As the photoconductor drums 100 to 104, an organic photoconductor (OPC) is used, and light is written by irradiating a laser beam corresponding to the image of the original onto a member uniformly charged to -200 to -2000V by the charging roller 200. To form an electrostatic latent image. The toner is negatively positively developed using a negatively chargeable toner to form a toner image on the photosensitive drums 100 to 104. As the intermediate transfer member 501, an intermediate transfer belt made of a thermosetting resin having a thickness of 0.10 mm, a width of 246 mm, and an inner peripheral length of 796 mm was used, and the moving speed of the intermediate transfer belt 501 was set to 150 mm / sec.
When the volume resistivity of the entire intermediate transfer belt formed of such a material was measured, it was 10 ⁷ to 10 ¹² Ωcm. Each volume resistivity is measured by applying a voltage of 100 V for 10 seconds using the measuring method described in JIS K6911. The surface resistivity of the intermediate transfer belt 501 was 10 ⁹ to 10 ¹⁴ Ω / □ when measured with a resistance measuring instrument “HI-LESTAR IP” manufactured by Mitsubishi Yuka. The surface resistivity can be measured by the surface resistance measurement method described in JIS K 6911, in addition to using the resistance measuring instrument.
A meandering regulation guide 511 for regulating the meandering of the intermediate transfer belt 501 is provided at both ends of the back surface of the intermediate transfer belt 501. The meandering regulation guide 511 is made of urethane rubber having a width of 4 mm and a thickness of 1 mm. Using. As the support rollers 502 to 509, metal rollers or rubber rollers having a diameter of 12 mm to 26 mm were used, and the roller width was set to 236 mm in order to prevent the intermediate transfer belt 501 from meandering. The support roller 510 has a diameter of 12 mm and a width of 230 mm, and the width is smaller than other support rollers. For the support roller 510, a rubber blade 512 is provided as a cleaning member.
As the secondary transfer roller 600, a roller made of urethane foam resin having a diameter of 26 mm and a width of 230 mm was used. The density detection means S used a reflection type sensor, and the distance between the sensor and the intermediate transfer member 501 was set to 4 mm. In the density detection by the density detection means S, first, the background portion of the intermediate transfer body 501 without an image is measured, and the density is calculated by comparing the measured value with the measurement of the image portion.

In the above example, an example in which the image carrier is applied to the intermediate transfer belt 501 is shown. However, the configuration of the present invention can be similarly applied to a case where a photosensitive belt is used as the image carrier. . In this regard, the photoconductors 101 to 104 of the above-described embodiment are replaced with belt-like ones, and the description is replaced with a configuration in which the density detection means S is installed, and thus detailed description is omitted.
In the above example, the tandem type image forming apparatus has been described. However, the present invention can also be applied to a one-drum type image forming apparatus. FIG. 5 shows a schematic configuration diagram of the image forming apparatus when the tandem type example of FIG. 2 is developed into a one-drum type. This is merely a replacement of the tandem type embodiment with a one-drum type, and a detailed description thereof will be omitted.
Further, although the blade-shaped member is shown as an example of the cleaning member for the support roller 501 and the intermediate transfer belt 501, any other shape such as a brush member or a mylar member may be used.

1 is a schematic configuration diagram of a color image forming apparatus according to an embodiment. It is a schematic block diagram of the image creation part in this embodiment. FIG. 6 is a schematic diagram when a meandering restricting member of an intermediate transfer belt rides on a support roller. It is a figure for demonstrating the positional relationship of the support roller and meandering control member in this embodiment. . It is the schematic which showed an example of the structure of the meandering control member in this embodiment. FIG. 5 is a schematic diagram when foreign matter adheres to the back surface of the intermediate transfer belt and reattaches to the support roller. It is the schematic which showed an example of the structure of the support roller cleaning member in this embodiment. FIG. 4 is a schematic diagram illustrating an example of a configuration of an intermediate transfer belt cleaning member in the present embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tandem image forming apparatus 2 Photoconductor exposure means 3 Paper feed table 4 Conveying / reversing device 5 Fixing devices 100 to 104 Photoconductor drums 201 to 201 Photoconductor charging means 301 to 304 Photoconductor cleaning means 401 to 404 Developing means 501 Intermediate transfer Body 502 Secondary transfer bias roller 503, 508 to 510 Support roller 511 Meander regulation guide 512 Meander regulation member 513 Support roller cleaning member 514 Intermediate transfer belt back surface cleaning member 504 to 507 Primary transfer bias roller 520 Intermediate transfer body cleaning means 600 2 Secondary transfer roller 700 Fixing device 800 Registration roller 901 Secondary transfer electric field forming means

Claims (3)

It is composed of at least three support rollers and an image carrier supported by the support rollers,
The width of the support roller at the position facing the image density detection unit provided on the image forming unit or the image forming apparatus main body side where the image forming unit is introduced and installed is larger than the width of the other support rollers. In a small image forming unit,
When the image forming unit is installed in the main body of the image forming apparatus, a meandering regulating member for regulating the meandering of the image carrier is installed on both sides of the image carrier at a position facing the image density detecting means. An image forming unit. The image forming unit according to claim 1,
The image forming unit is characterized in that a cleaning member is provided for a support roller at a position facing the image density detecting means. The image forming unit according to claim 1 or 2,
The image forming unit is provided with a cleaning member that contacts and cleans the back side of the image carrier at a position upstream of a support roller at a position facing the image density detecting means.

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