JP2007271870A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus which secures the fixation of a halftone image, and also, prevents waste power consumption. <P>SOLUTION: Regarding image data read from a storing means 3, the image density of the image data for every area of a plurality of areas obtained by dividing an image formation area at prescribed distances in a direction vertical to a copying paper conveying direction is judged by a density judging means 16 as a normal area, a halftone area, a linear image area, or a blank sheet area. When the halftone area exists, the fixation control temperature is controlled to be 5°C higher than a normal control temperature by a fixation temperature control means 17, based on the judgement result, and when the halftone area does not exist, but the normal area exists, the fixation control temperature is controlled to be a normal control temperature, and when the halftone area and the normal area do not exist, but the linear image area exists, the fixation control temperature is controlled to be 5°C lower than the normal control temperature, and when only the blank sheet area exists, a fixation heater is turned off. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming apparatus, and more particularly, to an image forming apparatus capable of securing fixability by controlling a fixing temperature.

  In Patent Document 1 described later, the environmental temperature of the image forming apparatus is detected. When the temperature is higher than a preset temperature, multi-value image processing is performed, and when the temperature is low, image processing is performed with two values. Thus, a technique for ensuring halftone fixability is described.

However, in this conventional technique, the low density area and the high density area of the transfer paper are fixed at the same fixing temperature, so wasteful heat is applied in the low density area, and power is increased accordingly. It will be wasted.
Japanese Patent Laid-Open No. 10-20576

  SUMMARY OF THE INVENTION In consideration of such background art, an object of the present invention is to provide an image forming apparatus that can secure a fixing property in a halftone area and can be economically operated while reducing wasteful power consumption. To do.

  In order to achieve this object, the present invention provides a density determination means for determining image density for each of a plurality of areas obtained by dividing image formation areas at predetermined distances in a direction perpendicular to the copy paper conveyance direction. And a fixing temperature control means for controlling the fixing control temperature of the fixing heater based on the determination result of the density determination means.

  In the present invention, for example, in the case of a copying machine, raw image data output from a reading device that reads a document can be used as image data, but data obtained from a storage means for storing the raw image data. It is efficient to use

  The density determination means determines the image density of each area divided in the order perpendicular to the conveyance direction of the copy paper or simultaneously, and gives the determination result to the fixing temperature control means.

  The density determination means is not particularly limited to the fixing temperature control means, but the determination results of each region include, for example, normal image density normal, higher density halftone, and lower density line drawing than normal. And a determination result of four levels of blank paper.

  The density determining means determines the image density for each area obtained by dividing the image data of the image forming area in the direction perpendicular to the conveyance direction of the copy paper, so that the image density differs in the direction perpendicular to the conveyance direction of the copy paper. Even if a region, for example, a halftone region and a blank region are mixed, the halftone region can be reliably detected.

  The fixing temperature control means controls the fixing control temperature of the fixing heater based on the determination results of all the divided areas arranged in the direction perpendicular to the copy paper conveyance direction.

  Here, as the fixing heater, for example, a rod-shaped lamp or the like in which the fixing control temperature is controlled uniformly throughout the direction perpendicular to the conveyance direction of the copy paper is generally used. It is possible to employ one capable of controlling the fixing temperature for each portion divided in the direction perpendicular to the conveyance direction of the copy paper corresponding to the area.

  When controlling a general fixing heater, the fixing temperature control unit controls the fixing heater according to the determination result of the highest density among the determination results of all the regions given from the density determination unit, for example.

  That is, the fixing temperature control means determines whether there is a halftone area based on the given determination result of each area, whether there is no halftone area, whether there is a normal area, However, it is determined whether or not there is a line drawing area, and the fixing control temperature of the fixing heater is controlled based on the determination result.

  For example, when it is determined that there is a halftone area, the temperature is set to, for example, 5 ° C. higher than the normal fixing control temperature. When it is determined that there is no halftone area but there is a normal area, normal fixing control is performed. When it is determined that there is no halftone area or normal area but there is a line drawing area, the temperature is set to, for example, 5 ° C. lower than the normal fixing control temperature, and the halftone area is also normal. If it is determined that there is no area or line drawing area, the fixing heater is turned off.

  However, this determination is executed by the density determination means, and only the determination result is given to the fixing temperature control means instead of the determination result of each region, and the fixing temperature control means controls the fixing heater based on the determination result. You may comprise.

  In this way, when there is a halftone area, the fixing control temperature can be set higher than usual to ensure halftone fixability, while when there is no halftone, the fixing temperature is set lower than that. By setting or turning off the fixing heater, power consumption can be saved and the economy can be improved.

  By the way, the range in the copy paper transport direction of the image data to be determined by the density determination means is not limited to one page. For example, an image forming area of one page is set in a predetermined direction in the copy paper transport direction. Each area is divided into a plurality of areas, and the image data of each area obtained by dividing the image forming area of one page vertically and horizontally is divided from the storage means into the copy paper in the transport direction and the direction perpendicular thereto. The image density for each area may be determined.

  In this way, the fixing heater is controlled in response to a change in the image density in the copy paper conveyance direction, and the power consumption can be further saved.

  As a fixing heater capable of controlling the fixing control temperature for each portion divided in the direction perpendicular to the conveyance direction of the copy paper corresponding to the region, for example, the size of the region in the direction perpendicular to the conveyance direction of the copy paper is used. A heater array in which a plurality of heaters are assembled at a pitch corresponding to the height, or an optical scanning type fixing heater capable of controlling each image pixel is used.

  In this case, the fixing temperature control means may be configured to accumulate determination results of all the divided areas arranged in the conveyance direction of the copy paper and simultaneously control the fixing control temperature of each area of the fixing heater. Each time the determination result is given, the fixing control temperature of each region of the fixing heater may be controlled sequentially.

  Based on the determination result of the density determination unit, the fixing control temperature control unit sets a normal control temperature when it is determined to be normal, and a fixing control temperature when it is determined as halftone, for each region. For example, when the line drawing is determined to be 5 ° C. higher than the normal control temperature, for example, the fixing control temperature is 5 ° C. lower than the normal control temperature, and when it is determined to be blank paper, the fixing heater is turned off.

  According to the control of the fixing temperature control means, the fixing heater generates heat at a normal control temperature in a portion corresponding to the region determined to be normal, and 5 ° C. above the normal control temperature in a portion corresponding to the region determined to be halftone. Heat is generated at a high temperature, the portion corresponding to the region determined to be a line drawing generates heat at a temperature 5 ° C. lower than the normal control temperature, and the portion corresponding to the region determined to be blank paper does not generate heat.

  Accordingly, in the halftone area, the fixing heater generates heat by 5 ° C. higher than the normal control temperature, so that the fixing property is secured. In the area determined to be a line drawing and the area determined to be blank paper, the power for driving the fixing heater is increased. It is saved and wasteful power consumption is prevented.

  As described above, the present invention provides density determination means for determining image density for each of a plurality of areas obtained by dividing image formation areas at predetermined distances in a direction perpendicular to the conveyance direction of copy paper. The fixing temperature control means for controlling the fixing control temperature of the fixing heater based on the determination result of the density determination means is provided, and the following effects can be obtained.

  First, for a halftone image where the image density is higher than normal and a large amount of energy is required, the fixing control temperature is set to, for example, 5 ° C. higher than the normal control temperature, and the fixing heater is set higher than the normal control temperature. In addition, for example, it is possible to obtain an effect that the fixing property can be ensured by generating heat at a high temperature of 5 ° C.

  Also, for a line drawing that requires less energy than the normal image density, the fixing heater is heated to a temperature that is, for example, 5 ° C. lower than the normal control temperature, thereby reducing energy consumption. The effect that it can reduce can be acquired.

  Further, with respect to white paper having an extremely low image density and almost no required energy, it is possible to obtain an effect that it is possible to turn off the fixing heater to eliminate wasteful power consumption.

  The best mode for carrying out the present invention will be specifically described with reference to the drawings.

  In the drawings, FIG. 1 is a functional block diagram of an image forming apparatus according to an embodiment of the present invention, FIG. 2 is a flowchart of control executed by the image forming apparatus, and FIG. 3 is an embodiment of the present invention. FIG. 4 is a flow diagram of control executed by an image forming apparatus according to another embodiment of the present invention.

  As shown in FIG. 3, an image forming apparatus according to an embodiment of the present invention is incorporated in a copying machine and stores image data stored in a storage unit 3 from a reading unit 2 that reads a document placed on a document platen 1. An image is formed based on the above.

  The image forming apparatus includes a latent image carrier 4 formed of a rotating drum, and a charger 5, a developing device 6, and a transfer device 7 that are arranged around the latent image carrier 4 in the rotation direction.

  The image forming apparatus includes an exposure unit 8 and a mirror 9 that reflects the light beam of the exposure unit 8 to the surface of the latent image carrier 4 between the charging unit 5 and the developing unit 6. After the surface of the image carrier 4 is uniformly charged, a latent image is formed by neutralizing part or all of the surface of the latent image carrier 4 with a laser beam emitted from the exposure device 8.

  That is, the exposure unit 8 is turned on corresponding to the image pixel of the document based on the image data sequentially read from the storage means 3, and is turned off corresponding to the background of the document. The laser beam emitted from the exposure unit 8 is reflected by the rotating mirror 9 and irradiated to a position corresponding to the image pixel of the original document on the latent image carrier 4, and only the position is neutralized.

  The toner image is developed on the latent image carrier 4 by adsorbing toner from the developing device 6 to the latent image carrier 4 on which the latent image is formed in this manner, and the latent image is developed from the manual feed tray 10 and other paper trays 11. The toner image is transferred by the transfer unit 7 to a sheet supplied between the image carrier 4 and the transfer unit 7.

  The image forming apparatus includes a fixing heater 12 made of, for example, a rod-shaped halogen lamp, and the toner transferred on the copy paper is heated by the fixing heater 12 to fix the toner image on the copy paper.

  The image forming apparatus includes a fixing heater control unit 13 shown in FIG. 1 for controlling the heat generation temperature of the fixing heater 12, that is, the fixing temperature. The fixing heater control unit 13 includes a counter 15 and a density. A determination unit 16 and a fixing temperature control unit 17 are provided.

  For example, image data for one page is read from the storage means 3 by dividing it into image data of an area obtained by dividing the image forming area at predetermined distances in a direction (sub-scanning direction) perpendicular to the conveyance direction of the copy paper. It is.

  As shown in FIG. 2, the counter 15 sequentially counts the number of dots of image data in the area (S 1), and the density determination means 16 is divided based on the count number given from the counter 15. The image density of the area is determined (S2).

  For each divided area, the density determination means 16 has a normal image density of the area, a halftone with a higher density than normal, a line drawing with a density lower than normal, and a blank sheet. It is determined which of the four stages it belongs to.

  The fixing temperature control unit 17 controls the fixing control temperature of the fixing heater 12 for each page according to the following procedure based on the determination result of the density determination unit 16.

  That is, the fixing control temperature setting means 17 determines whether or not there is a halftone area in each area (S3), and if not, determines whether or not there is a normal area (S4). If there is neither a halftone area nor a normal area, it is determined whether or not there is a line drawing area (S5).

  As a result of these determinations, the fixing temperature control means 17 sets the fixing control temperature to 5 ° C. higher than the normal fixing control temperature when it is determined that there is a halftone area (S6). When it is determined that there is no area but there is a normal area, the normal fixing control temperature is set (S7), and when it is determined that there is no halftone area and normal area but there is a line drawing area. Is set to 5 ° C. lower than the normal fixing control temperature (S8), and when it is determined that there is no halftone, normal, or line drawing area, the fixing heater 12 is turned off (S9).

  The supply current of the fixing heater 12 is controlled by inverter control, for example, so as to generate heat at the fixing control temperature set by the fixing temperature setting means 17.

  As a result, for pages with halftone areas, the fixing control temperature is 5 ° C. higher than normal, so the fixing property is secured, and for normal, line drawings, or blank pages without halftone areas. The fixing control temperature is set to normal or 5 ° C. lower than normal, or the fixing heater 12 is turned off to save power consumption.

  In an image forming apparatus according to another embodiment of the present invention, the fixing heater 12 has a fixing temperature for each portion corresponding to the region, that is, a region divided by a predetermined distance in a direction perpendicular to the conveyance direction of the copy paper. Are configured so that they can be different.

  Here, the fixing heater 12 is not particularly limited, but is a line head type in which heating resistors are arranged so that temperature control can be performed for each section so that the fixing temperature can be changed in response to control quickly. A heating unit is used.

  In this embodiment, the fixing temperature control of the fixing heater 12 by the counter 15, the density determination means 16 and the fixing temperature control means 17 is as follows.

  That is, as shown in FIG. 4, the counter 15 reads the image data from the storage means 3, and calculates the number of dots of the image data in each of a plurality of areas divided by a predetermined distance in the direction perpendicular to the copy paper conveyance direction. Measure (S11). Based on this count number, it is determined whether or not the density determination means 16 is a halftone (S12). If it is determined that the density determination means 16 is not a halftone, it is determined whether or not the density determination means 16 is a line drawing (S13). If it is determined that the image is not a line drawing, it is further determined whether or not the density determination means 16 is blank (S14).

  The fixing temperature control means 17 given the determination result controls the fixing control temperature of each part of the fixing heater 12 every time the determination result is given.

  That is, the fixing temperature control means 17 sets the fixing control temperature to 5 ° C. higher than the normal control temperature (S15) when it is determined as halftone (Yes at S12), and when it is determined as a line drawing (S13). (Yes) sets the fixing control temperature to 5 ° C. lower than the normal control temperature (S16). If it is determined to be blank (Yes in S14), the fixing heater is not lit (S17), and is determined to be normal (S17). No in S14) sets the fixing control temperature to the normal control temperature (S18).

  Further, the fixing temperature control means 17 raises the current supplied to the fixing heater 12 to 5 ° C. higher than the normal control temperature while heating the region determined to be a halftone by, for example, an inverter control method. During heating of the area determined to be a line drawing, the current to be generated is heated to 5 ° C. lower than the normal control temperature while heating the area determined to be a blank image. During the heating of the region determined to be, the current is controlled to generate heat to the normal control temperature.

  In this way, the fixing property is ensured by heating the fixing heater 12 at the normal control temperature in the normal region, and the fixing heater 12 is heated to 5 ° C. higher than the normal control temperature in the halftone region. As a result, the fixing property is secured.

  Further, in the area determined to be a line drawing, the fixing heater 12 generates heat at a temperature 5 ° C. lower than the normal control temperature, thereby saving the power for driving the fixing heater 12 without impairing the fixing performance.

  Furthermore, in the area determined to be blank, the fixing heater 12 is not turned on, thereby preventing unnecessary power consumption.

  The present invention develops a toner image by irradiating a latent image carrier with a laser beam on the basis of image data to form an electrostatic latent image, and adsorbing the toner to the electrostatic latent image. It is used in an image forming apparatus that fixes a toner image on a copy sheet by heating the image after copying the image directly or via a transfer body onto the copy sheet.

It is a functional block diagram of the present invention. It is a flowchart of this invention. 1 is a configuration diagram of a copying machine using the present invention. It is a flowchart of this invention.

Explanation of symbols

3 Storage means 12 Fixing heater 15 Counter 16 Density determination means 17 Fixing temperature control means

Claims (5)

Density determination means for determining an image density for each of a plurality of areas obtained by dividing the image forming area at predetermined distances in a direction perpendicular to the copy paper conveyance direction;
Fixing temperature control means for controlling the fixing control temperature of the fixing heater based on the determination result of the density determination means;
An image forming apparatus comprising:   2. The image forming apparatus according to claim 1, wherein the fixing temperature control means controls the fixing control temperature of the fixing heater uniformly in a direction perpendicular to the conveying direction of the copy paper.   The density determination unit includes a density determination unit that performs determination in four stages: a normal image density is normal, a halftone having a higher density than normal, a line image having a lower density than normal, and a blank sheet for each region. When the fixing temperature control means determines that there is a halftone area based on the determination result for each area, the fixing control temperature is higher than the normal control temperature, and there is no halftone area. When it is determined that there is a normal area, the normal control temperature is set, and when there is no halftone area or normal area but there is a line drawing area, the fixing control temperature is set lower than the normal control temperature. The image forming apparatus according to claim 2, further comprising a fixing temperature control unit that controls the fixing heater to be turned off when it is determined that there is no halftone, normal, or line drawing area. The fixing heater is configured to be able to control the fixing temperature for each portion divided in a direction perpendicular to the conveyance direction of the copy paper corresponding to the region, and the fixing temperature control unit fixes the fixing heater for each portion. The image forming apparatus according to claim 1, wherein the control temperature is controlled. The density determination unit includes a density determination unit that performs determination in four stages: a normal image density is normal, a halftone having a higher density than normal, a line image having a lower density than normal, and a blank sheet for each region. The fixing temperature control means sets the fixing control temperature to a normal fixing control temperature in the portion corresponding to the area determined to be normal, and the fixing control temperature to the normal control temperature in the portion corresponding to the area determined to be halftone. Fixing temperature control means for controlling the fixing control temperature to be lower than the normal control temperature in a portion corresponding to a region determined to be a high temperature and a line drawing, and to turn off the fixing heater in a portion corresponding to a region determined to be blank paper An image forming apparatus according to claim 4.

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