JP2005173114A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inexpensive image forming apparatus without causing any cleaning deficiency and soiling by toner on a transfer material. <P>SOLUTION: Electric field of positive and negative polarities are applied to a secondary transfer bias roller 502 by a secondary transfer electric field generating means 901 according to predetermined electrified field intensity, timing, and time. Thereby, test patch toner on the secondary transfer 600 is transferred to an intermediate transfer body 501. The test patch toner transferred onto the intermediate transfer body 501 is detected by a detection means S in order to judge a cleaned state. By judging the cleaned state of the test patch, cleaning conditions are set so as to be optimized according to the state of the apparatus, environmental conditions, etc., through the selection of a combination of a required electric field intensity, timing, and time. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus applied to an image forming unit such as a copying machine, a printer, and a facsimile machine.

  In an image forming apparatus using electrophotography, the toner image formed on the image carrier is primarily transferred to the intermediate transfer member, and the toner image on the intermediate transfer member is secondarily transferred onto the transfer material. The thing which adopted the method is known.

  In such an image forming apparatus, as a means for performing secondary transfer, the transfer material is conveyed while being sandwiched between the intermediate transfer member and a roller member, and at the same time, an electric field is applied to transfer the toner image on the intermediate transfer member. A method of secondary transfer to a material is generally used.

  Although the roller member does not normally come into direct contact with the toner image, the toner image on the intermediate transfer member is transferred to the roller member when the background dirt toner transferred from the image carrier onto the intermediate transfer member or the transfer material jam occurs. Toner contamination may occur due to contact with the toner.

  If this stain is left unattended, the back surface of the transfer material will be soiled with adhering toner the next time image formation is performed, a means for cleaning the roller member is required.

  As a means for cleaning unnecessary toner adhering to the roller member, there are a blade cleaning method for scraping unnecessary toner by pressing the blade-like member against the roller member, and an unnecessary electric toner is re-applied to the intermediate transfer member using an electric field. An electrostatic cleaning type is known in which the roller member is cleaned by being transferred.

With respect to the latter method, the technique described in Patent Document 1 can be exemplified as a method for more reliably cleaning the roller member. Patent Document 1 discloses an electric field condition in which unnecessary toner on a roller member is re-transferred onto an intermediate transfer member, toner on the intermediate transfer member is detected by density detection means, and applied to the roller member based on the density detection information. There has been proposed an image forming apparatus characterized by determining the above.
JP 2003-140470 A

  However, the conventional techniques have the following problems and often have problems.

First, the degree of contamination of the roller member is very random depending on the shape of the toner image when the roller member is soiled. For example, when the roller member is contaminated in a line drawing, the density detecting means on the intermediate transfer member Since the range of contamination was smaller than the detection range (usually several mm ² ), accurate concentration detection could not be performed. In addition, since accurate density detection cannot be performed, optimum cleaning conditions cannot be applied to actual dirt, and the back dirt of the transfer material often occurs.

  Further, the location where the roller member is stained is very random because it depends on the shape of the toner image when the roller member is stained. Therefore, in order to completely detect dirt, it is necessary to provide density detection means over the entire area where an image is to be formed. The fact that dozens of expensive density detection means have to be installed is costly. It was a burden and not realistic.

  The present invention has been made in view of the above problems, and provides an image forming apparatus that does not cause insufficient cleaning and does not cause toner contamination of a transfer material, and realizes such an image forming apparatus at low cost. For the purpose.

  In order to achieve the above object, the invention described in claim 1 is characterized in that a single or a plurality of image carriers, a charging means for charging the image carriers, and a surface of the image carrier are exposed by exposing them. An exposure unit that forms an electrostatic latent image; a developing unit that develops a toner image by attaching toner to the electrostatic latent image; and a primary transfer for transferring the toner image on the image carrier to an intermediate transfer member. Means for detecting the amount of toner image adhering on the intermediate transfer member, intermediate transfer cleaning means for cleaning an unnecessary toner image on the intermediate transfer member, and transferring the toner image on the intermediate transfer member In an image forming apparatus including a secondary transfer unit that transfers to a material, a test pattern for determining the degree of cleaning of the secondary transfer unit is attached to the secondary transfer unit, and the test pattern is A test pattern image re-transferred from the secondary transfer means to the intermediate transfer body and re-transferred onto the intermediate transfer body is detected by the detection means, and the cleaning condition of the secondary transfer means is determined according to the detection result. For example, by selecting a combination of required electric field strength, timing, and time, cleaning conditions optimized for the apparatus state, environmental conditions, etc. at that time are set. be able to.

  According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the cleaning operation is performed on the test pattern image to be attached to the secondary transfer unit during the operation of cleaning the unnecessary toner attached to the secondary transfer unit. It is characterized in that it is changed in accordance with the content of the image forming operation immediately before it is performed. For example, when it is a single color black color, a single color black test patch is used, and when it is a two color color, two colors are superimposed. By applying the test patch, it is determined whether or not the cleaning of the maximum adhesion amount that the secondary transfer unit may be dirty has been completed properly and satisfactorily according to the immediately preceding image forming mode. Can do.

  According to a third aspect of the present invention, in the image forming apparatus according to the first aspect, the detecting means is an optical measuring means.

  According to a fourth aspect of the present invention, in the image forming apparatus according to the first aspect, the cleaning condition of the secondary transfer unit is a length of cleaning time.

  According to a fifth aspect of the present invention, in the image forming apparatus according to the first aspect, the cleaning condition of the secondary transfer unit is an electric field strength applied to the secondary transfer unit during cleaning.

  According to a sixth aspect of the present invention, in the image forming apparatus according to the first aspect, the cleaning condition of the secondary transfer unit is a timing when the cleaning polarity is switched.

  According to the present invention, the cleaning conditions optimized for the apparatus state, environmental conditions, etc. at that time are set by selecting the cleaning conditions of the secondary transfer means, for example, a combination of necessary electric field strength, timing, and time. Thus, it is possible to provide a low-cost image forming apparatus that does not cause insufficient cleaning and does not cause toner contamination on the transfer material.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic configuration diagram of a color electrophotographic apparatus of a tandem type intermediate transfer system according to an embodiment of the present invention. 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 device, and 5 is a fixing device for finally fixing the image onto the transfer material.

  FIG. 2 is a detailed configuration diagram of the tandem image forming apparatus 1 in FIG. 1, and an endless belt-like intermediate transfer member 501 is provided at the center. The intermediate transfer member 501 is composed of rubber or resin having a single layer or multilayer structure.

  The intermediate transfer member 501 is supported and stretched by a secondary transfer bias roller 502 and support rollers 503, 508, 509, and 510, and can rotate counterclockwise in the illustrated example. An intermediate transfer member cleaning unit 520 for removing residual toner remaining on the intermediate transfer member 501 after image transfer is provided on the left side of the support roller 509 arranged on the left of the support rollers 503, 508, 509, and 510. It has been.

  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 located on the opposite side of the intermediate transfer body 501. 600 is installed.

  Further, a detecting unit S for detecting the density of the toner image on the intermediate transfer member 501 is provided so as to face the secondary transfer bias roller with the intermediate transfer member 501 interposed therebetween.

  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 generate 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 form 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. Writing exposure to the photoconductor is performed by irradiating the photoconductor with a laser by an exposure device (not shown) at a position between the photoconductor charging units 201 to 204 and the developing units 401 to 404.

  Below the secondary transfer roller 600, a registration roller 800 for feeding the transfer material to the secondary transfer unit is installed, and above the fixing device 700 for fixing the image on the transfer material.

  Next, a copy operation in the color electrophotographic apparatus of this embodiment will be described. The following operations are controlled by a CPU (Central Processing Unit) (not shown) which is a control means mounted on the apparatus.

  First, an image signal is input to the CPU from a personal computer or a scanner (not shown). After the input of the image signal, the photosensitive members 101 to 104 and the intermediate transfer member 501 are rotated by a drive motor (not shown) at a predetermined timing.

  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 the exposure device, and a developing unit 401 to 404. Development operation is performed. The toner images formed on the photoconductors 101 to 104 in this manner are formed on the intermediate transfer body 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. Subsequent transfer forms a monochromatic or multicolored visible image.

  On the other hand, after the input of the image signal, the transfer material is fed out from a paper feed table (not shown) at a predetermined timing, and is abutted against the registration roller 800 and stopped. 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 at that time, heat and pressure are applied to fix the visible image on the transfer material.

  On the other hand, the intermediate transfer member 501 after the image transfer is removed by the intermediate transfer member cleaning unit 520 to remove residual toner remaining on the intermediate transfer member 501 after the image transfer, so as to prepare for image formation again.

  Further, the secondary transfer roller 600 is cleaned at an arbitrary timing after image formation, during image formation, when power is turned on, or when a transfer material jam occurs.

  The secondary transfer roller 600 is cleaned by retransferring unnecessary toner from the secondary transfer roller 600 to the intermediate transfer member 501 by forming an electric field of the same polarity and reverse polarity as the toner on the secondary transfer bias roller. The unnecessary toner that has been transferred to the intermediate transfer member 501 is then cleaned by the intermediate transfer member cleaning means 520.

  Next, details of a method for cleaning the secondary transfer roller 600, which is a feature of the present invention, will be described.

  First, the cleaning condition optimization operation is performed when the apparatus power is turned on, for a predetermined period, or at a timing when the predetermined apparatus operation ends.

The optimization operation is performed by the following procedure, for example.
(1) By the above-described image forming operation, a test patch is formed by the tandem image forming apparatus 1 and is primarily transferred onto the intermediate transfer member 501 and further directly onto the secondary transfer roller 600 instead of the transfer material. Next transfer.
(2) The test patch toner on the secondary transfer roller 600 is applied to the secondary transfer bias roller 502 by applying an electric field of both positive and negative polarities to the secondary transfer bias roller 502 at a predetermined electric field strength, timing, and time. Transfer to the intermediate transfer member 501.
(3) The test patch toner transferred onto the intermediate transfer member 501 is detected by the detection means S, and the cleaning state is determined. The test patch at this time is the maximum amount of toner patch image that can be generated by the apparatus (for example, a test patch in which full colors are superimposed).
(4) The above operation is repeated while changing the cleaning conditions.
(5) Optimum conditions that can be cleaned and are efficient are selected and used as initial conditions for subsequent cleaning operations.

  At this time, it is important that the test is formed at a position that can be detected by the detection unit S that detects the toner density on the intermediate transfer member 501. Also, the shape and size of the test patch is formed as a patch image larger than the detection range, for example, so that the detection means S can sufficiently detect it.

  An example of condition setting for determining the initial condition is shown in FIG. FIG. 3A is an initial condition determination execution table based on the relationship between the applied voltage and the application time unit, and FIG. 3B is a relationship diagram between the applied voltage and the cleaning time. By determining the cleaning property, the required combination of electric field strength, timing, and time is selected. Thereby, it is possible to set the cleaning conditions that are optimized according to the apparatus state, environmental conditions, and the like at that time.

When performing a normal cleaning operation, for example, the following procedure is used.
(A) By the above-described image forming operation, a test patch is formed by the tandem image forming apparatus 1 and is primarily transferred onto the intermediate transfer member 501 and further directly onto the secondary transfer roller 600 instead of the transfer material. Next transfer. As a result, in addition to unnecessary toner to be cleaned, toner from the test patch is present on the secondary transfer roller 600. Note that the test patch at this time is changed according to the content of the immediately preceding image forming operation.
(B) By applying a positive / negative bipolar electric field to the secondary transfer bias roller 502 by the secondary transfer electric field forming means 901 under the optimization conditions described above, the test patch toner on the secondary transfer roller 600 is transferred to the intermediate transfer member. 501.
(C) The test patch toner transferred onto the intermediate transfer member 501 is detected by the density detection means S, and the cleaning state is determined. (D) When it is determined that the cleaning is completed, the cleaning operation is terminated.
(E) If the cleaning operation condition at this time is different from the initial condition, the condition at this time is used as the initial condition thereafter.

  In the above (a), the test patch for the cleaning determination is changed according to the content of the immediately preceding image forming operation. For example, when the immediately preceding image forming mode is a monochrome black color, If the test patch is two colors, the test patch with two colors superimposed is applied. As a result, it is possible to determine whether or not the cleaning of the maximum amount of adhesion that the secondary transfer roller 600 may be dirty has been completed, and in a scene where the cleaning operation is terminated earlier than the initial condition, Time can be shortened.

  Next, specific conditions in the present embodiment will be described.

  As the photoconductor drum 100, an organic photoconductor (OPC) is used, which is uniformly charged to −200 to −2000 V by the charging charger 200, and laser writing corresponding to the image of the original is irradiated to perform optical writing. 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 drum 100. 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 as the intermediate transfer member 501, 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-Lester IP” manufactured by Mitsubishi Oil Corporation. This surface resistivity can be measured by the surface resistance measuring method described in JIS K 6911, in addition to using the resistance measuring instrument.

  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 detecting means S for detecting the density used a reflective sensor, and the distance between the sensor and the intermediate transfer member 501 was set to 4 mm. In the density detection by the 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, the tandem type image forming apparatus has been described. However, the present invention is of course applicable to a one-drum type image forming apparatus. FIG. 4 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 tandem type configuration example replaced with a one-drum type, and detailed description thereof is omitted. However, 100 is a photosensitive drum, 200 is a photosensitive member charging means, and 300 and 301 are photosensitive members. Cleaning means, 400 to 404 are developing means, 501 is an intermediate transfer member, 502 is a secondary transfer bias roller, 510 to 514 are support rollers, 520 and 521 are intermediate transfer member cleaning means, 600 is a secondary transfer roller, and 700 is A fixing device, 800 is a registration roller, 901 is a secondary transfer electric field forming unit, and 1000 is a conveying unit.

  The image forming apparatus according to the present invention is applied to an image forming unit such as a copying machine, a printer, and a facsimile machine, and is not limited to the above-described embodiment, and can be applied to all apparatuses using the technical idea of the present invention. In addition, the photosensitive member, the intermediate transfer member, and the secondary transfer unit, which are image carriers, which are constituent elements, may use any one of a belt shape, a drum shape, and a roller shape.

1 is a schematic configuration diagram of a color electrophotographic apparatus of a tandem type intermediate transfer system that is an embodiment of the present invention. 1 is a detailed configuration diagram of the tandem image forming apparatus in FIG. Explanatory drawing of the execution table at the time of initial condition setting in this embodiment Schematic configuration diagram showing an example of a one-drum type of a color image forming apparatus according to the present embodiment

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tandem image forming apparatus 2 Photoconductor exposure means 3 Paper feed table 4 Conveyance / reversing device 5 Fixing devices 100 to 104 Photoconductor drums 200 and 201 Photoconductor charging means 300 to 304 Photoconductor cleaning means 400 to 404 Developing means 501 Intermediate transfer Body 502 Secondary transfer bias rollers 503, 508 to 514 Support rollers 504 to 507 Primary transfer bias rollers 520 and 521 Intermediate transfer body cleaning means 600 Secondary transfer roller 700 Fixing device 800 Registration roller 901 Secondary transfer electric field forming means S Detection means

Claims (6)

An image carrier composed of one or more, a charging unit for charging the image carrier, an exposure unit for forming an electrostatic latent image by exposing the surface of the image carrier, and the electrostatic latent image Developing means for attaching toner to develop it as a toner image, primary transfer means for transferring the toner image on the image carrier to an intermediate transfer body, and detecting the adhesion amount of the toner image on the intermediate transfer body In an image forming apparatus, comprising: a detecting unit that performs cleaning; an intermediate transfer cleaning unit that cleans an unnecessary toner image on the intermediate transfer member; and a secondary transfer unit that transfers the toner image on the intermediate transfer member to a transfer material. ,
A test pattern for determining the degree of cleaning of the secondary transfer unit is attached to the secondary transfer unit, and the test pattern is transferred again from the secondary transfer unit to the intermediate transfer member, so that An image forming apparatus comprising: a control unit that detects the test pattern image re-transferred to the first position by the detection unit and controls a cleaning condition of the secondary transfer unit according to a detection result.   The test pattern image to be attached to the secondary transfer unit is changed in accordance with the content of the image forming operation immediately before the cleaning operation during the operation of cleaning the unnecessary toner attached to the secondary transfer unit. The image forming apparatus according to claim 1.   The image forming apparatus according to claim 1, wherein the detection unit is an optical measurement unit.   The image forming apparatus according to claim 1, wherein the cleaning condition of the secondary transfer unit is a length of cleaning time.   2. The image forming apparatus according to claim 1, wherein the cleaning condition of the secondary transfer unit is an electric field strength applied to the secondary transfer unit during cleaning.   The image forming apparatus according to claim 1, wherein the cleaning condition of the secondary transfer unit is a timing when the cleaning polarity is switched.

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