JP2008203727A - Color image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a color image forming apparatus which enables stably continuing printing and maintains print quality of a character even when there leaves less coloring material of black and frequency of printing a character in black is high. <P>SOLUTION: When printing the character in black, the contour area of the character is printed in black with black toner, and the inside of the contour area of the character is printed in black by mixing magenta toner, cyan toner and yellow toner. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a color image forming apparatus such as a printer, a copying machine, and a facsimile machine that forms a color image.

  In color image forming apparatuses such as printers and copiers that form color images, it is common to use four types of color materials: magenta (M), cyan (C), yellow (Y), and black (K). is there. If magenta, cyan, and yellow are mixed, black is generated. However, it is difficult to generate complete black due to the characteristics of the color material, and therefore a black color material is used for printing in black.

  In color image forming apparatuses mainly used for business purposes, there is a problem that printing of black characters is frequently performed, and a large amount of black color material is consumed, resulting in insufficient printing.

  Therefore, Patent Document 1 proposes a method of printing black print data using magenta, cyan, and yellow color materials without using a black color material. If such a printing method is employed when the amount of black color material is reduced, the consumption of the black color material can be suppressed and printing can be continued even if the frequency of printing black characters is high.

Patent Document 2 discloses a method of printing black data using black color material for character data, and printing only graphic data using magenta, cyan, and yellow color materials without using black color material. Proposed.
JP 2004-209947 A JP 2004-202933 A

  However, in the printing method of Patent Document 1, since black characters are printed using magenta, cyan, and yellow color materials, the outline of the characters is generated by superimposing the three colors, and the physical properties of the three colors are mutually related. There is a problem in that the outline of a character is blurred due to the influence of a typical color shift and visibility is lowered.

  Moreover, in the printing method of the above-mentioned patent document 2, since the frequency of printing character data is high for business use, it is difficult to suppress the consumption of the black color material and it is difficult to continue printing.

  In view of the above problems, the present invention provides a color image formation that can continue stable printing and maintain the print quality of characters even when there are few black color materials and the frequency of printing black characters is high. An object is to provide an apparatus.

  In order to achieve the above object, when printing a black character, the color image forming apparatus of the present invention prints the outline region of the character in black with a black color material, and the inside of the outline region of the character is magenta. It is characterized by comprising printing means for printing in black by mixing a color material, a cyan color material, and a yellow color material.

  According to such a configuration, since the black color material is used only for printing the outline region of the character, the consumption of the black color material can be suppressed, the black color material is small, and the black character is printed. Even when the frequency is high, stable printing can be continued. In addition, physical color misregistration among magenta, cyan, and yellow can be buffered in the black portion of the outline region, and the print quality of characters can be maintained without degrading visibility.

  The color image forming apparatus according to the present invention further includes a detection unit that detects a remaining amount of the black color material in the storage unit in which the black color material is stored, and the black color material is transferred from the storage unit to the printing unit. When the color material is replenished and the remaining amount of the black color material detected by the detection unit is a predetermined amount or less, the printing unit prints black characters by the method.

  According to such a configuration, when there are few black color materials, it is possible to automatically perform printing while saving the black color materials.

  The color image forming apparatus of the present invention is characterized in that, in the above configuration, an operation unit is provided, and the printing unit prints black characters by the method when a predetermined setting operation is performed in the operation unit. .

  According to such a configuration, it is possible to perform printing while saving the black color material by the user's intention.

  The color image forming apparatus according to the present invention has the above-described configuration, wherein the first detection unit that detects the remaining amount of the black color material in the first storage unit in which the black color material is stored, and the magenta color material A second detection unit that detects the remaining amount of the magenta color material in the second storage unit to be stored, and a remaining amount of cyan color material in the third storage unit in which the cyan color material is stored A first detector; a third detector; a fourth detector for detecting a remaining amount of yellow color material in a fourth container in which a yellow color material is accommodated; and a display unit. A black color material, a magenta color material, a cyan color material, and a yellow color material are supplied to the printing unit from the first, second storage unit, third storage unit, and fourth storage unit. When the remaining amount of black color material detected by the first detection unit is 0, or magenta color material detected by the second detection unit When the remaining amount is 0, or when the remaining amount of cyan color material detected by the third detection unit is 0, or when the remaining amount of yellow color material detected by the fourth detection unit is 0 Moreover, the display unit displays a warning.

  According to such a configuration, it is possible to prevent a printing defect in a character outline region due to a shortage of black color material and a printing defect inside a character contour region due to a shortage of magenta, cyan and yellow color materials.

  According to the color image forming apparatus of the present invention, even when the black color material is small and the frequency of printing black characters is high, stable printing can be continued and the print quality of characters can be maintained.

  Embodiments of the present invention will be described below with reference to the drawings, taking a tandem color laser printer as an example.

  FIG. 1 is a block diagram of a tandem color laser printer according to the present invention. As shown in the figure, the color laser printer according to the present invention includes a host interface unit 1, an edge detection unit 2, an image processing unit 3, an exposure control unit 4, an engine control unit 5, a remaining toner amount. Detection units 6 a to 6 d, toner replenishing units 7 a to 7 d, a fixing unit 8, image forming units 9 a to 9 d, a paper transport unit 10, a display unit 11, and an operation unit 12 are provided. The image forming units 9a to 9d include LSUs (laser scanner units) 13a to 13d, chargers 14a to 14d, photosensitive drums 15a to 15d, transfer rollers 16a to 16d, and developing units 17a to 17d. Is done.

  Note that “a”, “b”, “c”, and “d” included in the reference numerals of the toner remaining amount detection unit, toner supply unit, image forming unit, LSU, charger, photosensitive drum, transfer roller, and developing unit are black. , Magenta, cyan, and yellow.

  The host interface unit 1 receives image data from a host such as a PC and outputs the image data to the image processing unit 3. The image processing unit 3 generates exposure data corresponding to each color of black, magenta, cyan, and yellow based on the image data input from the host interface unit 1 and outputs the exposure data to the exposure control unit 4 as will be described in detail later. To do. The edge detection unit 2 calculates edge strength based on the brightness data converted and output from the image data by the image processing unit 3, and outputs the calculation result to the image processing unit 3. The exposure control unit 4 causes each of the laser diodes of the LSUs 13 a to 13 d to emit light based on the exposure data corresponding to each color input from the image processing unit 3 and the exposure timing notified from the image processing unit 3.

  The engine control unit 5 controls each of the toner supply units 7 a to 7 d, the fixing unit 8, the image forming units 9 a to 9 d, and the paper transport unit 10.

  The paper transport unit 10 includes a transport roller and a motor that drives the transport roller, and transports the paper toward the image forming units 9a to 9d. The image forming units 9a to 9d are arranged in order in the paper transport direction. The LSUs 13a to 13d have a laser diode, a polygon mirror, a motor for rotating the laser diode, and the like, and generate laser latent images by irradiating the photosensitive drums 15a to 15d charged by the chargers 14a to 14d. The toners of the respective colors supplied from the developing units 17a to 17d adhere to the portions of the photosensitive drums 15a to 15d irradiated with the laser, and the adhered toner is transferred to the paper by the transfer rollers 16a to 16d to which a predetermined bias potential is applied. The The fixing unit 8 is disposed downstream of the image forming units 9a to 9d in the sheet conveyance direction, and heats and pressurizes the sheet to fix the toner on the sheet.

  In addition, a developing cartridge (not shown) is detachably attached to the laser printer according to the present invention, and the developing cartridge has toner storage portions that store toner of each color. Then, the toner of each color is supplied from each toner storage unit to the developing units 17a to 17d via the toner supply units 7a to 7d. The toner remaining amount detection units 6 a to 6 d detect the remaining amount of toner in each toner storage unit, and notify the engine control unit 5 of the detection result.

  The display unit 11 displays device setting information, operation details, error information, confirmation information for the user, and the like, and is configured by a liquid crystal display or the like. The operation unit 12 is a keyboard for the user to set the apparatus. The display unit 11 and the operation unit 12 may be integrally configured using a touch panel display or the like.

  Next, printing control in the laser printer according to the present invention having the above-described configuration will be described with reference to the flowchart of FIG.

  When the host interface unit 1 receives image data from the host and outputs the image data to the image processing unit 3, the process proceeds to step S1. Here, the image data includes RGB data for each dot, text attribute data for each dot in the character area, and graphic attribute data for each dot in the graphic area.

  In step S1, the image processing unit 3 separates the RGB data included in the image data into black, yellow, cyan, and magenta for each dot to generate KYCM data for each dot. Further, the image processing unit 3 performs HVC conversion on the RGB data included in the image data for each dot, and generates brightness data, saturation data, and tone data for each dot.

  Next, in step S2, the image processing unit 3 determines whether or not the target dot is white based on the RGB data and saturation data. If the target dot is white (Y in step S2), the process proceeds to step S11 to be described later, and white Otherwise (N in step S2), the process proceeds to step S3.

  In step S3, the image processing unit 3 determines whether or not the target dot is black based on RGB data or saturation data. If the target dot is black (Y in step S3), the process proceeds to step S4. N) in step S3, the process proceeds to step S9. In step S9, the image processing unit 3 creates exposure data corresponding to magenta, cyan, and yellow toners for printing the target dot with the color of the dot based on the KYCM data, and proceeds to step S11 described later.

  In step S4, the image processing unit 3 determines whether the setting information indicating that the black toner saving mode is set is stored in the engine control unit 4, and determines that the setting information is stored ( The process proceeds to step S5, and if not (Y in step S4), the process proceeds to step S8 described later. Here, when the engine control unit 5 determines that the remaining amount of black toner detected by the remaining toner detection unit 6a is equal to or less than a predetermined amount, the engine control unit 5 stores setting information indicating that the black toner saving mode is set. Further, even when the black toner saving mode setting operation is performed on the operation unit 12, the engine control unit 5 stores setting information indicating that the black toner saving mode is set.

  In step S5, the image processing unit 3 determines whether the attribute data of the target dot is text attribute data or graphic attribute data. If the target dot attribute data is text attribute data, it is assumed that the target dot is a constituent element of a character ( In step S5 (Y), the process proceeds to step S6. If the attribute data is graphic attribute data, the target dot is assumed to be a graphic component (N in step S5), and the process proceeds to step S10. In step S10, the image processing unit 3 creates exposure data corresponding to magenta, cyan, and yellow color toners for printing the target dots in black, and the process proceeds to step S11 described later.

  In step S <b> 6, the image processing unit 3 outputs brightness data corresponding to the target dot and each dot surrounding the target dot to the edge detection unit 2, and the edge detection unit 2 receives the brightness input from the image processing unit 3. The edge strength is calculated by calculating the differential value based on the data, and the calculation result is output to the image processing unit 3. Note that edge detection is a common technique in the field of image processing, and various methods can be employed (see, for example, Japanese Patent No. 3158498).

  In step S7, the image processing unit 3 determines whether the edge strength calculation result input from the edge detection unit 2 is equal to or greater than a predetermined value. If it is above (Y in step S7), the process proceeds to step S8. Otherwise, it is determined that the target dot is not on the outline area of the character, that is, inside the outline area (N in step S7), and proceeds to step S10 described above. .

  In step S8, the image processing unit 3 creates exposure data corresponding to black toner for printing the target dot in black, and the process proceeds to step S11.

  In step S11, the image processing unit 3 determines whether or not all the dots of the image data are the target dots. If all the dots of the image data are not the target dots (N in step S11), step S12 is performed. The target dot is changed to a new dot, and the process returns to step S2. If all the dots of the image data are the target dots in step S11 (Y in step S11), the process proceeds to step S13.

  In step S13, the engine control unit 5 controls the paper transport unit 10, the image forming units 9a to 9d, and the fixing unit 8, and the exposure data generated up to step S13 input from the image processing unit 3 by the exposure control unit 4. The laser diodes of the LSUs 13a to 13d emit light based on the exposure timing notified from the image processing unit 3, thereby forming electrostatic latent images on the photosensitive drums 15a to 15d and attaching the toners of the respective colors. The toner is transferred and fixed on the paper, and a color image is printed on the paper. This completes the flowchart of FIG.

  When the black toner saving mode is set, for black characters, the character outline area is printed in black with black toner, and the inside of the character outline area is black by mixing magenta, cyan, and yellow toners. Will be printed. When the black toner saving mode is set, black images on graphics are printed in black by mixing magenta, cyan, and yellow toners.

  Here, FIG. 3 shows the result of printing the entire character area in black by mixing magenta, cyan, and yellow toners (FIG. 3 (a), corresponding to Patent Document 1), and black toner by the laser printer according to the present invention. The printing result (FIG.3 (b)) of the black character in a saving mode is shown.

  As shown in FIG. 3A, when the entire character is printed in black by mixing magenta, cyan, and yellow toners, the outline is blurred due to physical misregistration between magenta, cyan, and yellow, and visibility is reduced. Resulting in. On the other hand, in the printing of black characters in the black toner saving mode by the laser printer according to the present invention, the physical color shift among magenta, cyan, and yellow is the black portion of the outline as shown in FIG. Can be buffered, and visibility is not lowered. And since black toner is used only for the outline, the consumption of black toner can be suppressed even when the remaining amount of black toner is low and the printing frequency of black characters is high, and stable printing can be continued. It becomes.

  2, when the remaining amount of black toner detected by the toner remaining amount detecting unit 6a is 0, or when the remaining amount of magenta toner detected by the remaining toner detecting unit 6b is 0. If the remaining amount of cyan toner detected by the toner remaining amount detection unit 6c is 0, or if the remaining amount of yellow toner detected by the toner remaining amount detection unit 6d is 0, the engine control unit 5 displays the display unit. 11 may display a message prompting the user to replace the toner. Thereby, it is possible to prevent printing failure of the character outline due to black toner shortage and printing failure inside the character outline due to lack of magenta, cyan and yellow toners.

  In this embodiment, a tandem color laser printer has been described as an example. However, the present invention can also be applied to other types of laser printers, inkjet printers, copiers, facsimiles, and the like.

FIG. 3 is a block diagram of a color laser printer according to the present invention. These are the flowcharts regarding the printing control in the color laser printer which concerns on this invention. (A) shows the result of printing the entire character in black by mixing magenta, cyan and yellow toners, and (b) shows the result of printing the black character in the black toner saving mode by the laser printer according to the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Host interface part 2 Edge detection part 3 Image processing part 4 Exposure control part 5 Engine control part 6a-6d Toner remaining amount detection part 7a-7d Toner replenishment part 8 Fixing part 9a-9d Image formation part 10 Paper conveyance part 11 Display Part 12 Operation part 13a-13d LSU
14a to 14d Charger 15a to 15d Photosensitive drum 16a to 16d Transfer roller 17a to 17d Developing unit

Claims (4)

  When printing a black character, the character outline area is printed in black with a black color material, and the inside of the character outline area is black by mixing a magenta color material, a cyan color material, and a yellow color material. A color image forming apparatus comprising printing means for printing on a color image. A detection unit that detects the remaining amount of black color material in a storage unit in which black color material is stored is supplied with black color material from the storage unit to the printing unit,
2. The color image forming apparatus according to claim 1, wherein when the remaining amount of the black color material detected by the detection unit is a predetermined amount or less, the printing unit prints black characters by the method.   The color image forming apparatus according to claim 1, further comprising an operation unit, wherein the printing unit prints black characters by the method when a predetermined setting operation is performed on the operation unit. . A first detection unit that detects a remaining amount of black color material in the first storage unit in which the black color material is stored; and a magenta color material in the second storage unit in which the magenta color material is stored A second detection unit for detecting a remaining amount, a third detection unit for detecting a remaining amount of cyan color material in a third storage unit in which cyan color material is stored, and a yellow color material are stored A fourth detection unit for detecting the remaining amount of the yellow color material in the fourth storage unit, and a display unit, wherein the first storage unit, the second storage unit, and the third storage unit A black color material, a magenta color material, a cyan color material, and a yellow color material are supplied to the printing means from the first and fourth storage portions,
When the remaining amount of black color material detected by the first detection unit is 0, or when the remaining amount of magenta color material detected by the second detection unit is 0, or the third detection unit When the remaining amount of cyan color material detected by is zero, or when the remaining amount of yellow color material detected by the fourth detection unit is 0, the display unit displays a warning. The color image forming apparatus according to any one of claims 1 to 3.