JP2011043683A - Image forming apparatus and image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an image forming apparatus that outputs an image of appropriate glossiness even when images are formed on various recording mediums different from one another in surface glossiness, smoothness, thickness, etc., without stopping the conveyance of a recording medium. <P>SOLUTION: The image forming apparatus includes: a fixing unit configured to convey a recording medium 9 to a nip formed between a fixing roller 122 and a pressure roller 126 firmly pressed against the fixing roller, thereby fixing a toner image on the surface of the recording medium 9; a recording medium heating device 121 for heating the recording medium at the prestage of the fixing unit; a glossiness measuring means 129 for measuring the glossiness of the surface of the recording medium 9 after fixing the toner image; and an alteration means for controlling the alteration of a heating condition for the recording medium heating device 121 based on the glossiness measured by the glossiness measuring means 129. The recording medium is heated by the emission of an infrared ray from the recording medium heating device 121. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus and an image forming method such as a copying machine, a facsimile machine, and a printer using toner, and in particular, image formation for forming images on various coated papers having different surface glossiness, smoothness, thickness, etc. The present invention relates to an apparatus and an image forming method.

  A fixing device used in an electrophotographic image forming apparatus such as a copying machine, a facsimile machine, or a printer includes a fixing roller controlled to a predetermined temperature, and a pressure roller that has an elastic body and presses the fixing roller. A heat roller fixing system in which an unfixed toner image on the surface of a recording medium is fixed by heating and pressurizing is widely used from a monochrome machine to a color machine.

  In order to improve mainly the quality and quality of color images, it is required to control the glossiness. Particularly in the case of a color image, it is preferable that the glossiness is high to some extent because the image density becomes high and the color gamut can be widened. On the contrary, if the glossiness is too high, the amount of reflected light increases, so that the character image has a drawback that it is difficult to read the character.

  In Patent Document 1 (Japanese Patent Application Laid-Open No. 06-175446), when a specific image quality mode such as a photographic mode is selected as an image glossiness control device in a heat roller fixing type image forming apparatus, An apparatus for increasing the pressure of the pressing means of the fixing device is described.

  Japanese Patent Laid-Open No. 11-119484 discloses an image forming apparatus that detects the gloss level of an image after fixing and resets gloss control parameters.

  On the other hand, in recent years, an electrophotographic image forming apparatus has been used in the field of light printing such as POD (Print On Demand), and is required to meet various needs regarding recording materials. For example, from high-gloss high-quality coated paper used for posters, catalogs, etc., low gloss recycled paper made of 100% used paper pulp, rough paper, etc., which is magazine paper.

  Patent Document 3 (Japanese Patent Laid-Open No. 07-311506) discloses a method for controlling the glossiness of various recording materials, and a recording material thickness detecting means and a recording material surface for detecting the surface gloss of the recording material. A device that changes the fixing condition in accordance with the output from the gloss detecting means is known.

  Further, in Patent Document 4 (Japanese Patent Laid-Open No. 2003-156969), it is assumed that the other glossiness is stably controlled even when the surface of the fixing roller changes with time due to long-term use of the fixing device. There is known an image forming apparatus that attempts to obtain the same image gloss as the initial image by controlling the fixing conditions corresponding to the surface glossiness detecting means.

  In Patent Document 5 (Japanese Patent Application Laid-Open No. 2007-334189), the glossiness of a non-image portion that does not have a toner image on the surface of a recording medium and an image portion that has a toner image are measured. Correspondingly, a reference value for the appropriate glossiness of the image area is set, and the pressure load of the pressure member to the fixing member and the conveyance speed of the recording medium so that the glossiness of the image area is within the reference value range Even when images are formed on various types of coated paper with different glossiness, smoothness, thickness, etc. by controlling the fixing conditions such as the control temperature of the fixing member and the fixing member, it is possible to output an image with appropriate glossiness An image forming apparatus can be obtained.

  However, in the image forming apparatuses described in Patent Document 1 and Patent Document 4, when image formation is performed on various types of paper having different surface gloss and thickness, the glossiness of the image after fixing is different. There's a problem.

  In other words, in a highly smooth paper such as gloss coated paper, the surface of the toner image formed on the surface becomes smooth and the glossiness becomes high. On the other hand, in the case of low smoothness paper such as recycled paper and rough paper, the surface of the toner image becomes rough and the glossiness becomes low. Further, since a large amount of heat is required for thick paper, the toner is not sufficiently melted at the time of fixing, so that the surface of the toner image formed on the paper becomes rough and the glossiness becomes low.

  In the image forming apparatus described in Patent Document 2, the image gloss control parameter is reset so that the glossiness of the image is within a specified value without considering the surface property of the paper, so that the smoothness is extremely high. When paper or low paper is used, there is a problem that the amount of parameter change becomes large and it is difficult to control the glossiness within a uniform specified value.

  Further, in the image forming apparatus described in Patent Document 3, since the fixing conditions are changed depending on the thickness of the recording material and the glossiness, the actual image glossiness after fixing is not reflected in the fixing conditions. For this reason, there is a problem that the actual image glossiness after fixing is not stable due to a change with time on the surface of the fixing roller or the influence of the surrounding environment at the time of image formation.

  In the image forming apparatus described in Patent Document 5, the pressing load of the pressing member to the fixing member and the control temperature of the fixing member are used as changing means in order to control the glossiness, and are changed when the glossiness is largely changed. It takes time to control the means, the conveyance of the recording medium is stopped, and the productivity of the printed matter is reduced. At this time, when the recording medium is continuous paper, since the recording medium is in the nip, an abnormal image due to excessive heating occurs in the image portion, and yellowing of the recording medium occurs in the non-image portion.

  In view of the above problems, the present invention has an appropriate glossiness even when image formation is performed on various recording media having different surface glossiness, smoothness, thickness, etc. without stopping the conveyance of the recording media. An object of the present invention is to obtain an image forming apparatus capable of outputting an image.

  In order to achieve the above object, according to a first aspect of the present invention, recording is performed in a nip portion formed between a fixing member controlled to a predetermined temperature by a heating unit and a pressure member pressed against the fixing member. A fixing device that conveys the medium and fixes the toner image on the surface of the recording medium; a recording medium heating device that heats the recording medium upstream of the fixing device; and a surface of the recording medium after the fixing of the toner image by the fixing device Glossiness measuring means for measuring the glossiness of the recording medium, and changing means for changing and controlling the heating conditions of the recording medium heating apparatus based on the glossiness measured by the glossiness measuring means, the recording medium heating apparatus Provides an image forming apparatus characterized in that a recording medium is heated by irradiation with far infrared rays.

  According to a second aspect of the present invention, as a second aspect, a nip formed between a fixing member that heats a recording medium being conveyed and is controlled to a predetermined temperature by a heating unit and a pressure member that is in pressure contact with the fixing member. The recording medium is transported to the section, the toner image on the surface of the recording medium is fixed, the glossiness of the surface of the recording medium after fixing the toner image is measured, and the recording medium being transported is measured based on the measured glossiness It is an object of the present invention to provide an image forming method characterized by changing and controlling the heating conditions when heating the film.

  According to the present invention, even when image formation is performed on various recording media having different surface glossiness, smoothness, thickness, etc. without stopping the conveyance of the recording medium, an image having an appropriate glossiness can be obtained. An output image forming apparatus can be obtained.

It is a figure which shows the structure of the form for implementing this invention It is a figure which shows the structure of the fixing part 12 of FIG. It is a figure which shows the structure of the glossiness measurement means 129 of FIG.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.
FIG. 1 shows the structure of a multi-color laser beam printer using a dry electrophotographic system, which is an embodiment for carrying out the present invention.

  As shown in FIG. 1, the multi-color laser beam printer 1 has image forming units 2 corresponding to toners of four colors of black (K), yellow (Y), magenta (M), and cyan (C), respectively. Hereinafter, when the image forming units 2 corresponding to the respective colors are referred to separately, they are referred to as image forming units 2K, 2Y, 2M, and 2C. The image forming unit 2 includes a photoreceptor 3, a charger 4, an optical unit 5, a developing device 6, and a transfer device 10.

  When a printing operation start signal is output from the controller, the photoconductor 3 having photoconductivity rotates at a speed corresponding to the printing speed, and when a negative (−) high voltage is applied by the charger 4, for example. The surface of the photoreceptor 3 is uniformly charged. Character data and graphic data converted into a dot image from the controller are transmitted to the printing apparatus as a laser beam ON / OFF signal, and the laser beam from the optical unit 5 is irradiated onto the surface of the photosensitive member 3 that is uniformly charged. The negatively charged toner is electrostatically attracted by the developing device 6 to the portion where the charge on the surface of the photoconductor 3 has disappeared due to the irradiation of the laser beam, and adheres to the photoconductor 3 to form an unfixed toner image 7. Form.

  The toner image formed on the photosensitive member 3 is transferred by the electrostatic attraction force of the transfer unit 10 onto the recording medium 9 which is conveyed while being kept at a constant tension by the paper guide 8. After the transfer of the unfixed toner image 7 has been completed, the photoreceptor 3 loses its surface charge uniformly, and then the residual toner is cleaned by the cleaner 11 and the charging process is started again.

  In the multi-color laser beam printer 1 shown in FIG. 1, the image forming process is performed in the image forming units 2 </ b> K, 2 </ b> C, 2 </ b> M, and 2 </ b> Y, and the unfixed toner image 7 is sequentially superimposed on the recording medium 9. Thereafter, the recording medium 9 is conveyed to the fixing unit 12, and the unfixed toner image 7 is heated and fixed on the recording medium 9.

  Next, the configuration of the fixing unit 12 will be described with reference to FIG. As shown in FIG. 2, the fixing unit 12 includes a recording medium heating device 121, a fixing roller 122, a fixing belt 123, a heating roller 124, a heating roller heater lamp 125, a pressure roller 126, a shutter 127, and a recording medium conveyance device 128. And 1211, and a glossiness measuring means 129. Further, as shown in FIG. 2, the unfixed toner image 7 is fixed on the recording medium 9 by the fixing unit 12, thereby forming a post-fixing toner 1210.

The recording medium heating device 121 includes a plurality of lamps that emit far-infrared rays and a reflector for increasing the heating efficiency of the lamps with respect to the recording medium 9. In this embodiment, 20 far-infrared lamps having a watt density of 0.033 W / mm ² are used. The heating area per lamp is 500 mm in the recording medium width direction and 55 mm in the recording medium conveyance direction. The fixing belt 123 is wound around a heating roller 124 heated by a fixing roller 122 and a heating roller heater lamp 125. The recording medium 9 is pressed by a fixing roller 122 and a pressure roller 126 via a fixing belt, and is conveyed together with the recording medium conveying devices 128 and 1211. The shutter 127 operates in parallel with the recording medium conveyance direction by a motor (not shown), and controls the number of lamps of the recording medium heating device that irradiates the recording medium. The time required to open the shutter 127 is 2 seconds to open all the lamps from the completely closed state.

  The unfixed toner 7 on the recording medium 9 is fixed by being pressed by a fixing roller 122 and a pressure roller 126 via a recording medium heating device 121 and a fixing belt 123 to become a toner 1210 after fixing.

  The glossiness of the post-fixing toner 1210 in the image portion on the recording medium 9 and the non-image portion of the recording medium 9 is measured by the glossiness measuring unit 129, respectively.

  An outline of the glossiness measuring means will be described with reference to FIG. The glossiness is defined by “Specular Glossiness—Measurement Method” of Japanese Industrial Standard JIS-Z8741. The glossiness measuring means 129 has a configuration conforming to the specular glossiness with the prescribed incident angle θ of 60 degrees.

Light from the light source 1291 is applied to the surface of the post-fixing toner 1210 and the recording medium 9 through the incident light optical system 1292. After fixing, the reflected light of the toner 1210 and the recording medium 9 is received by the light receiver 1294 via the reflected light optical system 1293. Each of the incident light optical system 1292 and the reflected light optical system includes a rectangular slit. For the specified incident angle θ (= 60 degrees) shown in the figure, the specular reflection light flux from the surface of the toner 1210 after fixing and the recording medium 9 is φ, the reflection light flux from the standard surface is φs, and the glossiness G is the following equation: It is represented by
G = (φ / φs) × (Glossiness of standard surface used)
Here, the glossiness of the standard surface used in advance is 100.0. Accordingly, the glossiness is represented by a numerical value of 100 or less.

Next, the operation of the image forming apparatus according to the embodiment of the present invention will be described.
First, the reference value of the glossiness of the image portion is set based on the glossiness of the non-image portion of the recording medium 9 measured by the gloss measurement unit 129. Regarding image gloss, there are portions related to personal preferences, but it is generally said that the difference in gloss between the image portion and the non-image portion is 15 deg. Therefore, ± 15 deg with respect to the reference value is stored in the control system as the target value of the image portion glossiness.

  For example, in the case of the recording medium 9 (hereinafter referred to as “paper A”) having a glossiness of 30 ° in the non-image area, the target glossiness of the toner 1210 after fixing may be within 15 ° to 45 °. When 20 lamps of the recording medium heating device 121 are turned on and 10 are blocked by the shutter 127 as a reference setting, and the image portion glossiness of the paper A is 10 ° under this setting condition, the target glossiness Therefore, control is performed so that the shutter 127 is opened and the number of irradiations to the recording medium 9 is increased. When the image portion glossiness is 50% under the above-described standard setting conditions, the shutter 127 is closed and control is performed so that the number of irradiations to the recording medium 9 is reduced because it is higher than the target glossiness. Since the shutter 127 is controlled, the gloss level can be controlled without stopping the conveyance of the recording medium 9. In addition, although the method of controlling the temperature of a heat roll and obtaining target glossiness is also considered, this method takes time and leads to the fall of productivity. Therefore, in the present embodiment, image gloss control is performed by shutter opening / closing control.

  As described above, the control system functions as a changing unit. The control system can be realized using ASIC (application specific integrated circuits) or the like.

  Next, the waiting time required for gloss control will be described. The waiting time required for controlling the glossiness by 5% takes 1 minute or more depending on the paper type, paper thickness, and NIP time of the fixing device in the conventional method of controlling the temperature of the heat roll. However, in this embodiment, since the time required from the state where the shutter 127 is completely closed to the opening is 2 seconds, the waiting time is obviously shorter in this embodiment.

  As described above, the conveyance of the recording medium is stopped by detecting the glossiness of the image area and the non-image area on the surface of the recording medium, and controlling the conditions of the recording medium heating device according to both measured values. Even when image formation is performed on various recording media having different surface glossiness, smoothness, thickness, etc., it is possible to obtain an image forming apparatus capable of outputting an image having an appropriate glossiness.

DESCRIPTION OF SYMBOLS 1 Multi-color laser beam printer 2 Image formation part 3 Photoconductor 4 Charging device 5 Optical part 6 Developer 7 Unfixed toner image 8 Paper guide 9 Recording medium 10 Transfer device 11 Cleaning machine 12 Fixing part 121 Recording medium heating device 122 Fixing roller 123 Fixing Belt 124 Heating Roller 125 Heating Lamp for Heating Roller 126 Pressure Roller 128 Recording Medium Conveying Device 129 Glossiness Measuring Unit 1210 Toner After Fixing 1211 Recording Medium Conveying Device 1291 Light Source 1292 Incident Light Optical System 1293 Reflected Light Optical System 1294 Light Receiver

Japanese Patent Laid-Open No. 06-175446 JP 11-119484 A Japanese Patent Application Laid-Open No. 07-311506 JP 2003-156969 A JP 2007-334189 A

Claims (6)

A fixing device that transports a recording medium to a nip formed between a fixing member controlled to a predetermined temperature by a heating unit and a pressure member that presses the fixing member, and fixes a toner image on the surface of the recording medium; ,
A recording medium heating device for heating the recording medium upstream of the fixing device;
Glossiness measuring means for measuring the glossiness of the surface of the recording medium after fixing the toner image by the fixing device;
Changing means for changing and controlling the heating conditions of the recording medium heating device based on the glossiness measured by the glossiness measuring means;
With
The image forming apparatus, wherein the recording medium heating apparatus heats the recording medium by irradiation with far infrared rays. The gloss measuring means measures reflected light between a non-image portion having no toner image and an image portion having a toner image,
The image forming apparatus according to claim 1, wherein the changing unit changes and controls the heating condition based on measured values of both the non-image portion and the image portion measured by the glossiness measuring unit.   The changing means changes and controls the heating condition based on a reference value set by a measured value of the non-image portion by the glossiness measuring means and a measured value of the image portion by the glossiness measuring means. The image forming apparatus according to claim 2, wherein the image forming apparatus is characterized.   The image forming apparatus according to claim 1, wherein the heating condition is at least one of a radiation amount and an irradiation area of a far-infrared recording medium.   The heating device has an open / close shielding member that can change the amount of radiation and the irradiation area of the far-infrared recording medium, and the changing means changes the heating condition by performing control to open / close the open / close shielding member. The image forming apparatus according to claim 4. Heat the recording medium being transported,
A recording medium is conveyed to a nip formed between a fixing member controlled to a predetermined temperature by a heating unit and a pressure member pressed against the fixing member to fix a toner image on the surface of the recording medium;
Measure the gloss of the surface of the recording medium after fixing the toner image,
An image forming method comprising: changing and controlling a heating condition when heating a recording medium being conveyed based on the measured glossiness.

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