JP3835382B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to an image forming apparatus such as a color laser printer.
[0002]
[Prior art]
  In recent years, so-called tandem color laser printers, each equipped with a photosensitive drum corresponding to each color of cyan, magenta, yellow, and black, can form color images at the same speed as laser printers that form monochrome images. It is becoming popular as a color laser printer.
[0003]
  On the other hand, in Japanese Patent Application Laid-Open No. 11-134856, even if the row address is different, if the precharge time can be omitted, the precharge time can be omitted, and the operation speed can be increased. It has been proposed to improve the read / write speed using a plurality of DRAMs.
[0004]
[Patent Document 1]
  JP-A-11-134856
[Problems to be solved by the invention]
  In a color laser printer, the following method is adopted as a method for transferring color data memory for forming a color image.
[0005]
  That is, when image data for one page is input from a computer via an interface, the image data is stored in the DRAM. One page of image data stored in the DRAM is color data of three colors, cyan, magenta, and yellow.
[0006]
  Next, black color data is created from the three color data and is set as four color data.
[0007]
  The four color data is written again in the DRAM, and based on the four color data, cyan, magenta, yellow, and black toner images are formed on the photosensitive drum, respectively, and the color image is formed on the paper. It is formed.
[0008]
  However, although the address in the DRAM is specified by specifying the row address and the column address, the DRAM can be read and written quickly within the same row address, but in order to read and write sequentially from different row addresses. Since it needs to be precharged once, it has a characteristic that it takes time.
[0009]
  However, in the above-described color data memory transfer method, since the color data of cyan, magenta, and yellow are initially stored in the DRAM for each color data, When reading, since it is necessary to read the color data of the three colors corresponding to the address from different row addresses in the DRAM for each address, it takes a lot of time, and quick memory transfer, There is a problem that the image forming speed cannot be improved.
[0010]
  Therefore, when the proposal of Japanese Patent Application Laid-Open No. 11-134856 is adopted in a color laser printer, three color data of cyan, magenta, and yellow for one page of image data for creating black color data is obtained for each color. In other words, they must be stored in different DRAMs, resulting in an increase in cost and a problem of complicated control.
[0011]
  The present invention has been made in view of the above problems, and an object of the present invention is to form a color image at high speed by increasing the speed of the memory data transfer method. To provide an apparatus.
[0012]
[Means for Solving the Problems]
  In order to achieve the above object, an invention according to claim 1 is an image forming apparatus in which three color data consisting of cyan data, magenta data, and yellow data are converted for each color data.As continuous data that is continuousFrom the first area of the DRAM to be stored, the storage means independent of the DRAM having the first area, the second area of the DRAM independent of the storage means, and the first area, for each color data,A given amountReading means for reading continuous data into the storage means, and color data of three colors of cyan data, magenta data, and yellow data from the storage means within the same row address of the second area., Skip each memory addressWriting means for writing to be stored;Means for controlling cyan data, magenta data, and yellow data to be stored in consecutive storage addresses in the second area by repeating reading by the reading means and writing by the writing means for each color for three colors. When,Data conversion means for reading the color data of the three colors stored in the second area and converting the color data into four color data composed of cyan data, magenta data, yellow data, and black data. It is said.
[0013]
  According to such a configuration, the color data of the three colors stored in the first area is once read as continuous data into the storage means by the reading means, and then within the same row address in the second area by the writing means. Are written as color data of three colors. Therefore, when the three color data is converted into the four color data by the data conversion means, the three color data stored in the same row address can be read quickly. By speeding up the memory transfer method, a color image can be formed at high speed.
In the second area, cyan data, magenta data, and yellow data corresponding to one pixel are stored at consecutive storage addresses. Therefore, the data conversion means converts the three color data into the four color data. In the case of conversion to, it is possible to continuously read color data of three colors in the same row address for each pixel. Therefore, the speed can be further increased and a color image can be formed at a high speed.
[0014]
  According to a second aspect of the present invention, in the first aspect of the present invention, the first area and the second area are assigned to the same DRAM.
[0015]
  According to such a configuration, since the first area and the second area are assigned to the same DRAM, the cost can be reduced as compared with the case where they are separately used.
[0016]
  According to a third aspect of the present invention, in the first or second aspect of the present invention, the storage means is an SRAM.
[0017]
  According to such a configuration, since the storage means is an SRAM, the reading / writing speed is faster than that of the DRAM, so that the speed of the color data memory transfer method can be further increased, and a color image can be formed at high speed. can do.
[0018]
  According to a fourth aspect of the present invention, in the invention according to any one of the first to third aspects, the storage unit stores continuous data for one raster.
[0019]
  According to such a configuration, the reading unit and the writing unit can perform processing for each horizontal row of one page. Therefore, simplification of control can be achieved, and further increase in speed can be achieved.
[0020]
  According to a fifth aspect of the present invention, in the first aspect, the first area stores color data for one page for each color data. It is a feature.
[0021]
  According to such a configuration, since one page of color data is stored for each color data, the control can be simplified and the speed can be further increased.
[0022]
MaClaim6The invention described in the above is an image forming apparatus, in which three color data composed of cyan data, magenta data, and yellow data are converted for each color data.As continuous data that is continuousFrom the DRAM to store, the SRAM, and the DRAM, for each color data,A given amountReading means for reading continuous data into the SRAM so that the color data of three colors is stored, and reading continuous data of the three colors stored in the SRAM to obtain cyan data, magenta data, yellow data, and black data And a data conversion means for converting the color data into four color data.
[0023]
  According to such a configuration, the three color data stored in the DRAM is read into the SRAM as three color data by the reading means. For this reason, when the three color data is converted into the four color data by the data conversion means, the three color data stored in the SRAM can be quickly read. By speeding up the transfer method, a color image can be formed at high speed.
[0024]
  Claims7The invention described inAn image forming apparatus,Three color data consisting of cyan data, magenta data, and yellow data are stored for each color data.As continuous data that is continuousA first DRAM to be stored, a second DRAM independent of the first DRAM, and each color from the first DRAMA predetermined amount ofThree colors of color data, cyan data, magenta data, and yellow data, are stored in the same row address of the second DRAM.Skip each memory addressReading means for reading so as to be memorized,Means for controlling the cyan data, the magenta data and the yellow data to be stored in consecutive storage addresses of the second DRAM by repeating the reading by the reading means for each color for three colors;Data conversion means for reading color data of three colors stored in the second DRAM and converting the data into four color data consisting of cyan data, magenta data, yellow data, and black data; Yes.
[0025]
  According to such a configuration, the three color data stored in the first DRAM is read as three color data in the same row address of the second DRAM by the reading means. Therefore, when the three color data is converted into the four color data by the data conversion means, the three color data stored in the same row address of the second DRAM can be read quickly. By increasing the speed of the color data memory transfer method, a color image can be formed at high speed.
[0026]
  Claims8The invention described in claim 1 to claim 17In any one of the inventions, a photoreceptor and a developing device are provided for each of cyan, magenta, yellow, and black.
[0027]
  According to such a configuration, since each of the cyan, magenta, yellow, and black has a photoconductor and a developing device, each developing device forms a toner image corresponding to each color on each photoconductor. By sequentially transferring the color image, a color image can be formed at the same speed as an image forming apparatus that forms a monochrome image. In addition, in this image forming apparatus, since the speed of the method for transferring the color data memory is increased, the speed of color image formation can be further increased.
[0028]
DETAILED DESCRIPTION OF THE INVENTION
  FIG. 1 is a cross-sectional side view of an essential part showing an embodiment of a color laser printer as an image forming apparatus of the present invention. In FIG. 1, the color laser printer 1 includes a feeder unit 4 for feeding paper 3 into a main body casing 2, an image forming unit 5 for forming an image on the fed paper 3, and both sides of the paper 3. Are provided with a reversing conveyance unit 6 for forming an image.
[0029]
  The feeder unit 4 includes a sheet feeding tray 7 that is detachably attached to the bottom of the main body casing 2, a sheet feeding roller 8 that is disposed above one end of the sheet feeding tray 7, and a conveyance direction of the sheet 3. , A transport roller 9 disposed on the downstream side of the paper feed roller 8, and a registration roller 10 disposed on the downstream side of the transport roller 9. In the paper feed tray 7, a paper pressing plate 11 whose end facing the paper feeding roller 8 is movable in the vertical direction is provided, and the paper 3 is stacked on the paper pressing plate 11. ing. The sheet pressing plate 11 is urged from the back by a spring (not shown), and the uppermost sheet 3 on the sheet pressing plate 11 is pressed toward the sheet feeding roller 8 by the spring, and the sheet feeding roller 8. Is fed one by one by the rotation of. The sheet 3 fed by the sheet feeding roller 8 is sent to the registration roller 10 by the conveyance roller 9, and after the predetermined registration by the registration roller 10, a transfer position (secondary transfer roller 14 and first roller 28 described later). Sent to).
[0030]
  The image forming unit 5 includes a process unit 12, an intermediate transfer mechanism 13, a secondary transfer roller 14, a fixing unit 15, and the like.
[0031]
  The process unit 12 is provided for each color (four colors), and includes a developing cartridge 16 as a developing device, a photosensitive drum 17 as a photosensitive member, a scorotron charger 18, an LED array 19, a primary transfer roller 20, and The drum cleaner 21 is provided. In addition, the process units 12 are provided in parallel in the vertical direction at predetermined intervals.
[0032]
  The developing cartridge 16 includes four developing cartridges 16, which are detachably attached to the respective process units 12, that is, a yellow developing cartridge 16 Y, a magenta developing cartridge 16 M, a cyan developing cartridge 16 C, and a black developing cartridge 16 K. A storage chamber 22, a supply roller 23, a developing roller 24, a layer thickness regulating blade 25, and the like are provided.
[0033]
  Each toner storage chamber 22 stores yellow (Y), magenta (M), cyan (C), and black (K) positively charged non-magnetic single component toner. Examples of the toner include polymerizable monomers such as styrene monomers such as styrene, and acrylic monomers such as acrylic acid, alkyl (C1 to C4) acrylate, and alkyl (C1 to C4) methacrylate. Polymerized toners obtained by copolymerization by a known polymerization method such as suspension polymerization are used. Such a polymerized toner has a substantially spherical shape and extremely good fluidity. In addition, a colorant or wax corresponding to each color is blended with such a toner, and an external additive such as silica is added to improve fluidity, and the particle size is about It is about 6 to 10 μm.
[0034]
  The toner in the toner storage chamber 22 is discharged toward the supply roller 23 from the toner supply port opened to the side of the toner storage chamber 22 by the stirring of the agitator 26.
[0035]
  A supply roller 23 is rotatably disposed on the side of the toner supply port, and a developing roller 24 is rotatably disposed opposite the supply roller 23. The supply roller 23 and the developing roller 24 are in contact with each other in a state where the supply roller 23 is compressed to some extent.
[0036]
  The supply roller 23 has a metal roller shaft covered with a roller made of a conductive sponge member.
[0037]
  In the developing roller 24, a metal roller shaft is covered with a roller made of an elastic member made of a conductive rubber material. More specifically, the roller of the developing roller 24 is composed of an elastic roller portion made of conductive urethane rubber, silicone rubber, EPDM rubber or the like containing carbon fine particles, and urethane coated on the surface of the roller portion. It is formed of a two-layer structure with a coat layer, the main component of which is rubber, urethane resin, polyimide resin or the like.
[0038]
  A developing bias is applied to the developing roller 24 with respect to the photosensitive drum 17.
[0039]
  A layer thickness regulating blade 25 is disposed in the vicinity of the developing roller 24. The layer thickness regulating blade 25 includes a pressing portion having a semicircular cross section made of insulating silicone rubber at the tip of a blade body made of a metal leaf spring material. The pressing portion is supported by the developing cartridge 16 near 24 and is configured to be pressed against the developing roller 24 by the elastic force of the blade body.
[0040]
  The toner discharged from the toner supply port is supplied to the developing roller 24 by the rotation of the supplying roller 23. At this time, the toner is positively frictionally charged between the supplying roller 23 and the developing roller 24. Further, the developing roller The toner supplied onto the toner 24 enters between the pressing portion of the layer thickness regulating blade 25 and the developing roller 24 as the developing roller 24 rotates. Is carried on the developing roller 24 as a thin layer.
[0041]
  The photosensitive drum 17 is disposed on the side of the developing roller 24 so as to be rotatable in a state of being in contact with the developing roller 24. The photosensitive drum 17 has a drum main body grounded and a surface formed by a photosensitive layer of an organic photosensitive member mainly composed of polycarbonate.
[0042]
  The scorotron charger 18 is disposed on the side of the photosensitive drum 17 so as to face the photosensitive drum 17 with a predetermined interval therebetween. The scorotron charger 18 is a positively charged scorotron charger that generates corona discharge from a charging wire such as tungsten, and is configured to uniformly charge the surface of the photosensitive drum 17 to a positive polarity. ing.
[0043]
  The LED array 19 is provided on the side of the photosensitive drum 17 and between the scorotron charger 18 and the developing roller 24 in the rotational direction of the photosensitive drum 17. The LED array 19 is configured by arranging a large number of LEDs, and the surface of the photosensitive drum 17 is exposed and irradiated by light emission of LEDs based on image data.
[0044]
  The toner for each color is exposed and developed as follows. That is, first, the surface of the photosensitive drum 17 is uniformly positively charged by the scorotron charger 18 by the rotation of the photosensitive drum 17, and then exposed by light emission from the LED array 19, and image data (cyan, described later). Data, color data for each color of magenta data, yellow data or black data) is formed. Next, the electrostatic latent toner formed on the surface of the photosensitive drum 17 when the positively charged toner carried on the developing roller 24 contacts the photosensitive drum 17 by the rotation of the developing roller 24. An image, that is, a surface of the photosensitive drum 17 that is uniformly positively charged, is supplied to a portion where the potential is lowered by being exposed by the LED array 19, and is selectively carried to form a toner image. Thus, reversal development is achieved.
[0045]
  The primary transfer roller 20 is disposed on the downstream side of the developing roller 24 in the rotation direction of the photosensitive drum 17 so as to face the photosensitive drum 17 with the endless belt 30 interposed therebetween. The primary transfer roller 20 has a metal roller shaft covered with a roller made of a conductive rubber material. The primary transfer roller 20 is rotated by driving of the photosensitive drum 17, and a transfer bias is applied to the photosensitive drum 17. Applied. The toner image carried on the photosensitive drum 17 is transferred to the endless belt 30 while the endless belt 30 passes between the photosensitive drum 17 and the primary transfer roller 20.
[0046]
  The drum cleaner 21 is disposed between the primary transfer roller 20 and the scorotron charger 18 in the rotation direction of the photosensitive drum 17. The drum cleaner 21 has a box shape for collecting the remaining toner, and a portion facing the photosensitive drum 17 is opened. A tip portion of the drum cleaner 21 contacts the surface of the photosensitive drum 17. A scraping blade 27 is provided. The residual toner remaining on the surface of the photosensitive drum 17 after the transfer is scraped off by the scraping blade 27 and collected in the drum cleaner 21.
[0047]
  The intermediate transfer mechanism 13 is disposed in the vertical direction so as to face each photosensitive drum 17 in the main body casing 2, and includes a first roller 28 provided on the lower side, a second roller 29 provided on the upper side, The endless belt 30 is wound around the outer circumference of the first roller 28 and the second roller 29, and the surface to be transferred can be moved from the top to the bottom in the direction of the arrow.
[0048]
  Then, by rotating the first roller 28 and the second roller 29, the endless belt 30 is sequentially opposed to the respective photosensitive drums 17, so that the toner images of the respective colors formed on the respective photosensitive drums 17 are sequentially transferred to the endless belt 30. A color image is formed by superimposing it on top. That is, for example, when the yellow toner image formed on the photosensitive drum 17 by the yellow toner filled in the yellow developing cartridge 16Y is transferred onto the endless belt 30, the magenta developing cartridge 16M is then filled. A magenta toner image formed on the photosensitive drum 17 by magenta toner is transferred onto the endless belt 30 to which an image of yellow toner has already been transferred, and formed by the cyan developing cartridge 16C by the same operation. The cyan toner image to be formed and the black toner image formed by the black developing cartridge 16 </ b> K are superimposed and transferred, whereby a color image is formed on the endless belt 30.
[0049]
  The secondary transfer roller 14 is rotatably disposed at a position facing the first roller 28 of the intermediate transfer mechanism 13 with the sheet 3 interposed therebetween. In the secondary transfer roller 14, a metal roller shaft is covered with a roller made of a conductive rubber material, and a transfer bias is applied. The color image formed on the endless belt 30 is collectively transferred to the sheet 3 while the sheet 3 passes between the endless belt 30 and the secondary transfer roller 14.
[0050]
  The fixing unit 15 is disposed on the downstream side in the conveyance direction of the sheet 3 with respect to the secondary transfer roller 14, and a pair of heating rollers 31 and 32 that are pressed against each other, and the pair of heating rollers 31 And 32, a pair of transport rollers 33 provided on the downstream side in the transport direction of the sheet 3 is provided. The heating rollers 31 and 32 are made of metal and are provided with a halogen lamp for heating, and the color image transferred onto the paper 3 by the secondary transfer roller 14 is transferred to the pair of heating rollers 31 and 32. Then, the sheet 3 is heat-fixed while passing between the sheets, and then the sheet 3 is conveyed to the sheet discharge path 34 by the conveying roller 33.
[0051]
  The paper discharge path 34 is provided along the vertical direction of the main casing 2, and a pair of transport rollers 35 and 36 are provided so as to face the paper discharge path 34, respectively. A pair of paper discharge rollers 37 is provided.
[0052]
  The paper 3 sent to the paper discharge path 34 by the transport roller 33 of the fixing unit 15 is transported by the transport rollers 35 and 36 and discharged onto the paper discharge tray 38 by the paper discharge roller 37.
[0053]
  The reverse conveyance unit 6 includes a reverse conveyance path 39 and a flapper 40 that switches the conveyance direction. One end of the reverse conveyance path 39 is connected near the conveyance roller 35 of the paper discharge path 34, and the other end is connected to the paper path between the conveyance roller 9 and the registration roller 10. In addition, a pair of reverse conveyance rollers 41 and 42 are provided so as to face the reverse conveyance path 39, respectively.
[0054]
  The flapper 40 is swingably provided so as to face a branch portion between the paper discharge path 34 and the reverse conveyance path 39, and has a predetermined surface on one surface by excitation or non-excitation of a path switching solenoid (not shown). The sheet 3 on which the color image is formed can be switched between a direction toward the sheet discharge path 34 and a direction toward the reverse conveyance path 39 from the sheet discharge path 34.
[0055]
  When images are formed on both sides of the sheet 3, when the sheet 3 having an image formed on one side is sent from the sheet discharge path 34 to the sheet discharge roller 37, the sheet discharge roller 37 is The paper 3 is rotated forward in a state where the paper 3 is sandwiched, and the paper 3 is once transported toward the outside (the paper discharge tray 38 side), and most of the paper 3 is sent to the outside. When the sheet is sandwiched between the sheet discharge rollers 37, the forward rotation is stopped, and then the sheet discharge roller 37 is rotated in the reverse direction so that the flapper 40 conveys the sheet 3 from the sheet discharge path 34 to the reverse conveyance path 39. Switch the transport direction. As a result, the sheet 3 is conveyed in the reverse direction (downward) in the paper discharge path 34 by the reversely rotated conveying rollers 35 and 36 in the reverse direction, and is conveyed to the reverse conveying path 39 by switching the flapper 40. Is done. When the conveyance of the paper 3 in the reverse direction is completed, the flapper 40 is switched to the original state, that is, the state in which the paper 3 sent from the conveyance roller 33 is sent to the paper discharge path 34. Next, the sheet 3 conveyed in the reverse direction to the reverse conveyance path 39 is conveyed to the registration roller 10 by the reverse conveyance rollers 41 and 42. The paper 3 conveyed to the registration roller 10 is sent to the transfer position again in a reversed state after registration, whereby an image is formed on both sides of the paper 3.
[0056]
  Further, the color laser printer 1 is provided with a belt cleaner 43 for collecting the toner remaining on the endless belt 30 after the color images are collectively transferred onto the paper 3. The belt cleaner 43 is located on the side of the intermediate transfer mechanism 13 and in a cleaner casing 44 disposed between the first roller 28 and the second roller 29, and a cleaner brush 45, a recovery roller 46, and a recovery box 47. And a scraper 48.
[0057]
  The cleaner brush 45 is radially formed on a cylindrical main body, and is rotatably disposed in a state where the brush faces the endless belt 30 in a contact state. A bias is applied to the cylindrical main body so as to give a predetermined potential difference to the endless belt 30.
[0058]
  The collection roller 46 is made of a metal roller, and is disposed below the cleaner brush 45 so as to be rotatable in a state of facing the brush of the cleaner brush 45 in a contact state. Further, a bias is applied to the collection roller 46 so as to give a predetermined potential difference between the recovery roller 46 and the cleaner brush 45.
[0059]
  The collection box 47 has an opening at a portion facing the collection roller 46 below the collection roller 46, and a scraper 48 that is pressed onto the collection roller 46 is provided in the vicinity of the opening.
[0060]
  The toner remaining on the endless belt 30 after the color image is collectively transferred to the sheet 3 is scraped by the cleaner brush 45 when being opposed to the cleaner brush 45, and is applied by a bias applied to the cleaner brush 45. Adhere to the brush. After that, the residual toner attached to the cleaner brush 45 is attached to the collection roller 46 by a bias applied to the collection roller 46 when facing the collection roller 46, and then scraped off by the scraper 48 to the collection box 47. Collected.
[0061]
  FIG. 2 is a block diagram showing an electrical configuration of the color laser printer 1.
[0062]
  2, the color laser printer 1 includes an interface (I / F) 51, an engine 52, a control board 53, and the like, and is connected to a PC (personal computer) 54 as an external device via the interface 51. ing. The engine 52 is composed of various mechanical elements corresponding to the operation of the color laser printer 1.
[0063]
  The control board 53 is provided with a CPU 56, an ASIC 55, a ROM 57a, and a RAM 57b that form the center of control.
[0064]
  The CPU 56 includes a register 60 for calculation therein.
[0065]
  The ASIC 55 is an IC circuit for connecting the CPU 56 to the ROM 57 a, RAM 57 b, interface 51, and engine 52, and is connected to the CPU 56, ROM 57 a, and RAM 57 b through the bus 61 inside the control board 53. In the ASIC 55, an SRAM 62 as a storage unit is provided.
[0066]
  The SRAM 62 is set so as to be able to store color data for one raster of the color data constituting the image, that is, one column of horizontal data for one page. Note that the SRAM 62 sequentially reads and writes data in the same row address or in different row addresses, so there is no need to precharge or wait after designating the row address.
[0067]
  The ASIC 55 is connected to the interface 51 and the engine 52 by a bus 61. As a result, the PC 54 is electrically connected to the control board 53 of the color laser printer 1 via the interface 51, and a print job created by the PC 54 is input to the first DRAM 58 (described later) and stored in the program in the ROM 57a. Based on the control of the CPU 56, the operation of various machine elements inside the engine 52 is controlled via the ASIC 55.
[0068]
  The ROM 57a stores various programs for controlling the color laser printer 1, and stores a read program as a reading unit, a write program as a writing unit, a data conversion program as a data converting unit, etc., which will be described later. ing.
[0069]
  The RAM 57b is a memory for storing temporary numerical values, and includes, for example, a first DRAM 58 and a second DRAM 59, and each is connected to the ASIC 55 and the ROM 57a by a bus 61. The first DRAM 58 and the second DRAM 59 can sequentially read and write in the same row address, but in order to sequentially read and write from different row addresses, precharge and temporarily specify the row address. I need to wait later. The first DRAM 58 includes a first area 63 and a second area 64 which are independent memory areas. The first area 63 and the second area 64 are set so as to store color data of three colors including cyan (C) data, magenta (M) data, and yellow (Y) data, respectively.
[0070]
  The first area 63 is set so that one page of color data can be stored for each of the three color data of cyan data, magenta data, and yellow data.
[0071]
  The second area 64 is set so that cyan data, magenta data, and yellow data can be stored in the same row address. More specifically, cyan data, magenta data, and yellow data corresponding to one pixel are stored. It is set so that it can be stored continuously.
[0072]
  Next, a method for transferring color data memory for forming a color image in the laser printer 1 will be described.
[0073]
  The color data is data for specifying the color of an image to be printed, and is included in a print job for one page created by the PC 54. This color data includes three color data consisting of cyan data, magenta data, and yellow data for each pixel, and for each color data, a color level of 256 gradations, that is, 0 to 255 gradations. have.
[0074]
  When a print job for one page created by the PC 54 is input to the control board 53, three color data consisting of cyan data, magenta data, and yellow data in the print job are stored in the first DRAM 58. One area 63 is stored as continuous color data. More specifically, for example, as shown in FIG. 3, C00 to C99, which are cyan data for one page, are stored as continuous data. Further, one page of magenta data M00 to M99 and one page of yellow data Y00 to Y99 are stored as continuous data. When the three color data consisting of cyan data, magenta data and yellow data are stored as continuous data in the first area 63 of the first DRAM 58, each color data is then controlled under the control of the CPU 56 for starting the read program. Then, continuous data for one raster is read into the SRAM 62. Then, the continuous data for one raster for each color read into the SRAM 62 is written to a predetermined storage address in the same row address of the second area 64 of the first DRAM 58 under the control of the CPU 56 for starting the write program. .
[0075]
  More specifically, for example, as shown in FIG. 3, the CPU 56 causes the CPU 56 to first perform cyan data for one raster, for example, C00, C01 and cyan data for one raster in the first area 63. The continuous data of C02 is read, and the CPU 56 writes the read continuous data into the SRAM 62 by a write program. Then, the CPU 56 reads the continuous data from the SRAM 62 by the read program, and the CPU 56 writes it to a predetermined storage address in the same row address of the second area 64 of the first DRAM 58 by the write program. In the writing to the second area 64, the continuous data for one raster is divided into cyan data for each pixel, and is written in a skipped storage address without being continuous in the same row address. More specifically, each cyan data is written by skipping two storage addresses in the same row address.
[0076]
  In this way, when one raster of cyan data is stored in the second area 64 of the first DRAM 58, the CPU 56 then uses the read program again to cause the CPU 56 to read the magenta data M00, M01 and M02 for one raster. The continuous data is read, and the CPU 56 writes the read continuous data in the first area 63 by a write program. Then, the CPU 56 reads out the continuous data by the read program, and writes the data at a predetermined storage address in the same row address of the second area 64 of the first DRAM 58 by the write program. In the writing to the second area 64, the continuous data for one raster is divided into magenta data for each pixel, and is written in a skipped storage address without being continuous in the same row address. More specifically, each magenta data is written by skipping two storage addresses so as to be adjacent to cyan data of the same pixel in the same row address.
[0077]
  When one raster of magenta data is stored in the second area 64 of the first DRAM 58, the CPU 56 again reads the continuous data of Y00, Y01 and Y02, which is yellow data for one raster, by the read program. The CPU 56 writes the read continuous data in the first area 63 by the write program. Then, the CPU 56 reads out the continuous data by the read program, and writes the data at a predetermined storage address in the same row address of the second area 64 of the first DRAM 58 by the write program. In the writing to the second area 64, the continuous data for one raster is divided into yellow data for each pixel, and is written in a skipped storage address without being continuous in the same row address. More specifically, each yellow data is written by skipping two storage addresses so as to be adjacent to the magenta data of the same pixel in the same row address.
[0078]
  Thus, in the second area 64 of the first DRAM 58, cyan data, magenta data, and yellow data corresponding to one pixel are stored as one set for one raster.
[0079]
  Next, in this method, under the control of the CPU 56 in which the data conversion program is started, from the second area 64 of the first DRAM 58, from the cyan data, magenta data, and yellow data corresponding to one continuous pixel within the same row address. Are sequentially read into the register 60 in the CPU 56 for each set, and the register 60 converts the color data into four color data composed of cyan data, magenta data, yellow data, and black data. Thereafter, the data is sequentially written in the second DRAM 59 as color data of four colors of cyan data, magenta data, yellow data, and black data corresponding to one pixel.
[0080]
  The color data conversion in the register 60 is executed by an operation for generating black data from cyan data, magenta data, and yellow data.
[0081]
  More specifically, in this calculation, the lowest color level is extracted from the color levels of cyan data, magenta data, and yellow data, and the lowest color level is generated as black data. By subtracting the color level of the black data from the color level of the color data of the color, the color data of 4 colors is obtained. For example, if the color data of three colors consisting of cyan data, magenta data and yellow data read into the register 60 has 100 gradations, 10 gradations and 30 gradations, respectively, the magenta color level is Since it is the lowest, black data of 10 gradations that is the lowest color level is generated.
[0082]
  The generated 10 gradation black data is subtracted from the 100 gradation cyan data, the 10 gradation magenta data, and the 30 gradation yellow data to obtain 90 gradation cyan data and 0 gradation gradation data. Magenta data and 20 gradation yellow data are generated. As a result, new cyan data, magenta data, yellow corresponding to one pixel is obtained based on the three color data consisting of cyan data, magenta data, and yellow data corresponding to one pixel stored in the second area 64. Four color data consisting of data and black data is generated, and the second DRAM 59 stores four color data for each pixel for one page.
[0083]
  In this method, such processing is repeated for one page.
[0084]
  The color data for each color of cyan data, magenta data, yellow data and black data stored in the second DRAM 59 is controlled by the CPU 56 from the LED array 19 provided for each color to the electrostatic latent image 17 on each photosensitive drum 17. Each is written as an image.
[0085]
  At this time, the process actually executed in the control board 53 is, for example, the procedure of FIG. That is, in FIG. 4, in this process, first, in order to read the cyan data stored in the first area 63 of the first DRAM 58, the row address of the first area 63 is designated, and a predetermined waiting time has elapsed. The cyan data (C00, C01 and C02) for one raster stored in the row address are sequentially read out and written to the SRAM 62 in the ASIC 55 (processing A).
[0086]
  Then, after the first DRAM 58 is precharged and a predetermined standby time elapses, the row address of the second area 64 is designated, and after the predetermined standby time elapses, the cyan data stored in the SRAM 62 is read out. Then, it is written in the same row address in the second area 64 of the first DRAM 58 (process B).
[0087]
  Next, in order to read out the magenta data stored in the first area 63 of the first DRAM 58, after the first DRAM 58 is precharged and a predetermined waiting time has elapsed, the row address of the first area 63 is designated, After a predetermined waiting time has elapsed, magenta data (M00, M01 and M02) for one raster stored in the row address are sequentially read out and written to the SRAM 62 in the ASIC 55 (process C).
[0088]
  Then, after the first DRAM 58 is precharged and a predetermined standby time elapses, the row address of the second area 64 is designated, and after the predetermined standby time elapses, the magenta data stored in the SRAM 62 is read. Then, in the second area 64 of the first DRAM 58, it is written in the same row address as the row address in which the cyan data is written (process D).
[0089]
  When cyan data and magenta data are stored in the second area 64, yellow data (Y00, Y01 and Y02) for one raster is read from the first area 63 of the first DRAM 58 in the same manner as these. Are written in the SRAM 62 and then written in the same row address as the row address in which the cyan data and magenta data in the second region 64 of the first DRAM 58 are written (Processing E and F).
[0090]
  In this way, when the continuous color data of three colors of cyan data, magenta data, and yellow data are stored in one set for one pixel in the same row address of the second area 64, the first DRAM 58 is precharged. After a predetermined standby time has elapsed, the row address is designated, and after the predetermined standby time has elapsed, the three color data stored in the row address are read out and stored in the register 60. By writing and generating black data from the three color data, four color data is generated (process G).
[0091]
  Then, after the second DRAM 59 is precharged and a predetermined standby time elapses, the row address of the second DRAM 59 is designated, and after the predetermined standby time elapses, the four color data generated in the register 60 are stored. Are written in the second DRAM 59 (process H).
[0092]
  On the other hand, in the conventional color data memory transfer method, as shown in FIG. 5, three color data consisting of cyan data, magenta data, and yellow data stored in each address of the first DRAM 58 corresponds to one pixel. Each color data is read out and written in the register 60. Black data is generated from the three color data corresponding to one pixel, converted into four color data, and then written in the second DRAM 59. It is.
[0093]
  In such a conventional method, for example, as shown in FIG. 6, when color data of four colors for one raster is written in the second DRAM 59 (processing P to Z3), precharge is performed for each color in one pixel. Thus, it is necessary to specify a row address (for example, processing P to Z1, processing S to Z2, processing V to Z3). Therefore, in such a conventional method, the number of clocks required for the memory transfer is 19.5 clocks, and for example, an image is formed on A4 size paper composed of vertical and horizontal 1200 dpi, 8-bit multi-value data per pixel. In this case, assuming that the number of clocks of the CPU 56 and the RAM 57b is 100 MHz and the bus width is 64 bits, the data capacity for one raster is 10,000 bytes, and one screen of A4 size is 14000 rasters. The time T required for the memory transfer process is 3.4 seconds.
[0094]
  T = 10000 × 14000 × 19.5 × 10 (nS) / 8
    = 3.4 (S)
  On the other hand, in the processing shown in FIG. 4 described above, the color data for one continuous raster is read from the first area 63 of the first DRAM 58 and written to the SRAM 62, and the color data written to the SRAM 62 is read, and the data for one continuous raster is read. The number of clocks required for the memory transfer process when the color data is written to the second area 64 of the first DRAM 58 is 3.0 clocks. Then, color data for one raster of cyan data, magenta data, and yellow data stored in the second area 64 of the first DRAM 58 is read and written to the register 60, and the three color data is converted into four color data. Later, since the number of clocks written to the second DRAM 59 is 11.5 clocks, the number of clocks required for memory transfer for one raster is 14.5 clocks.
[0095]
  In the same manner as described above, the time T required for the memory transfer process when an image is formed on A4 size paper is 2.5 seconds from the following equation.
[0096]
  T = 10000 × 14000 × 14.5 × 10 (nS) / 8
    = 2.5 (S)
  From the above, when the memory of color data is transferred by this method, it can be shortened from the conventional 3.4 seconds to 2.5 seconds per A4 size sheet. Therefore, a color image can be formed at a high speed by increasing the speed of the color data memory transfer method.
[0097]
  That is, in the method shown in FIG. 3 described above, continuous data for one raster for each color data is read from the same row address in the first area 63, so that the reading speed in the first area 63 is high, and Since the continuous data is written to the SRAM 62 and the continuous data is read from the SRAM 62, the writing and reading speed in the SRAM 62 is high, and the continuous data read from the SRAM 62 is written in the same row address in the second area 64. Since the color data for each color written in the same row address is read out, the writing and reading speed in the second area 64 is fast, and further, the black data generated based on the color data of each color read from the register 60 The four color data including the data is stored in the second DRAM 59. Since writing in the row address, the write speed in the 2DRAM59 is fast, it is possible to achieve the speed of the transfer speed of the memory.
[0098]
  In the above-described method, since the first area 63 and the second area 64 are allocated to the same first DRAM 58, compared with the case where the first area 63 and the second area 64 are allocated to different DRAMs, respectively. Thus, the cost can be reduced.
[0099]
  In addition, since one page of color data is stored in the first area 63 of the first DRAM 58 for each color data, the CPU 56 can simplify the control and further increase the speed. be able to.
[0100]
  In this method, since the memory for temporarily storing the color data for each color is the SRAM 62, the read / write speed is faster than that of the DRAM, and the memory data transfer speed of the color data can be further increased. Can be formed at high speed.
[0101]
  In addition, since this SRAM 62 can store color data for one raster for each color, the color data for one column in the horizontal direction for one page is controlled by the CPU 56 by starting the read program or the write program. It can be processed easily. Therefore, simplification of control can be achieved, and further increase in speed can be achieved.
[0102]
  In addition, since the cyan data, magenta data, and yellow data corresponding to one pixel are continuously stored in the second area 64 of the first DRAM 58, the second area 64 is controlled by the CPU 56 that starts the data conversion program next. When converting the color data of the color into the color data of four colors, the color data of the three colors that are continuous in the same row address can be read sequentially and sequentially for each pixel as a set. Therefore, the speed can be further increased and a color image can be formed at a high speed.
[0103]
  From the above, in the tandem type color laser printer 1 that can form a color image at a speed similar to that of a monochrome image by such a color data memory transfer method, the color image formation is further accelerated. can do.
[0104]
  Next, processing of the above-described color data memory transfer method will be described with reference to FIGS.
[0105]
  In this process, when a print job including image data is input from the PC 54 (S1), cyan data, magenta data, and yellow data for one page of the image data are stored in the first area 63 of the first DRAM 58. It is continuously stored as color data for each color (S2).
[0106]
  Then, among the color data for each color stored in the first DRAM 58, first, cyan data for one raster is read and written in the SRAM 62 in the ASIC 55 (S3), and then the cyan data stored in the SRAM 62. Are read out and written in the same row address in the second area 64 of the first DRAM 58 (S4).
[0107]
  Next, out of the color data for each color stored in the first area 63 of the first DRAM 58, magenta data for one raster is read, written to the SRAM 62 in the ASIC 55 (S5), and then stored in the SRAM 62. The magenta data thus read is read out and written in a jump manner so as to be adjacent to each cyan data within the same row address as the cyan data written in the second area 64 of the first DRAM 58 (S6).
[0108]
  Further, among the color data for each color stored in the first area 63 of the first DRAM 58, yellow data for one raster is read out and written into the SRAM 62 inside the ASIC 55 (S7), and then stored in the SRAM 62. The yellow data is read out and written in the second area 64 of the first DRAM 58 so as to be adjacent to each magenta data in the same row address as the row address in which the cyan data and magenta data are written (S8). ).
[0109]
  Thus, when cyan data, magenta data, and yellow data for one raster are written in a continuous set corresponding to one pixel in the same row address of the second area 64 of the first DRAM 58, the data is stored in the second area 64. The cyan data, magenta data, and yellow data corresponding to the one pixel thus read are read out and written in the register 60 of the CPU 56 (S9). Then, black data K is generated by the operation of the register 60. As described above, the black data K is determined based on the color data having the lowest color level among the three color data, and based on the black data K, new cyan data C ′ and magenta data M are obtained. 'And yellow data Y' are generated. Then, the color data of four colors newly generated in this way is written in the second DRAM 59 (S10).
[0110]
  When the four colors of color data are written into the second DRAM 59, it is determined whether or not the color data for one raster has been converted (S11). If the processing for one raster is not completed (S11: NO), the processes of S9 and S10 are repeated until the processing for one raster is completed. If the processing for one raster has been completed (S11: YES), it is determined whether or not the color data for one page has been converted (S12). If the processing for one page has not been completed (S12: NO), the processing from S3 to S11 is repeated to execute the processing for the next one raster again. If the processing for one page is completed, newly generated cyan data C ′, magenta data M ′, yellow data Y ′ and black data K for one page stored in the second DRAM 59 are transferred to the engine 52. Then, it is subjected to the above-described image forming operation (S13), and a series of processing is completed.
[0111]
  In the above embodiment, the SRAM 62 is set so as to store color data for one color for one raster, data for one raster for each color is read from the first DRAM 58, written to the SRAM 62, and then Color data for one raster for each color is written in the same row address from the SRAM 62 to the second area 64. For example, as shown in FIG. 9, the SRAM 62 has three colors for one raster. The color data of the three colors corresponding to one pixel may be written directly from the SRAM 62 to the register 60.
[0112]
  That is, in such a method, first, among the color data for one color stored in the first DRAM 58, three color data for one raster, that is, cyan data for one raster, magenta data for one raster. The yellow data for one raster is read out and written in the SRAM 62 sequentially.
[0113]
  Next, cyan data, magenta data, and yellow data corresponding to one pixel are read from the three colors of color data for one raster written in the SRAM 62, written in the register 60, and in the register 60 as described above. Further, these three color data are converted into four color data.
[0114]
  Then, the converted four color data is written into the second DRAM 59 in the same manner as described above.
[0115]
  In this way, when the color data of 3 colors is converted to color data of 4 colors, the color data of 3 colors stored in the SRAM 62 can be read quickly (that is, the SRAM 62 differs from the DRAM in that it differs. Since each color data corresponding to one pixel can be read and written quickly from the row address), it is possible to form a color image at a high speed by increasing the speed of the color data memory transfer method.
[0116]
  In the above embodiment, the first area 63 and the second area 64 are allocated to the same first DRAM 58. For example, as shown in FIG. 10, the first area 63 is allocated to the first DRAM 58 and the second area May be assigned to the second DRAM 59.
[0117]
  That is, in such a method, first, each color data for one raster stored in the first area 63 of the first DRAM 58 is read and written in the same row address in the second DRAM 59. More specifically, first, cyan data for one raster stored in the first area 63 of the first DRAM 58 is read and written to the second DRAM 59 in a jump. Next, magenta data for one raster stored in the first area 63 of the first DRAM 58 is read out, and jumps adjacent to the cyan data within the same row address as the cyan data written in the second DRAM 59. Written. Further, yellow data for one raster stored in the first area 63 of the first DRAM 58 is read out, and jumps adjacent to the magenta data within the same row address as the row address where the cyan data and magenta data are written. Written.
[0118]
  Next, in this method, color data of three colors consisting of cyan data, magenta data, and yellow data corresponding to one pixel is read from the second DRAM 59 in the same row address, and sequentially written in the register 60. In the register 60, after being converted into color data of four colors including cyan data, magenta data, yellow data, and black data, the third area 65 different from the second area 64 of the second DRAM 59 corresponds to one pixel. Sequentially written as four color data of cyan data, magenta data, yellow data and black data.
[0119]
  In this way, when converting the three color data into the four color data, the three color data stored in the same row address of the second DRAM 59 can be quickly read. By speeding up data memory transfer, a color image can be formed at high speed.
[0120]
  As mentioned above, although embodiment of this invention was described, this invention can be implemented also in other embodiment. In the above embodiment, the tandem color laser printer 1 has been described as an example of the image forming apparatus. However, the present invention can be developed as an image forming apparatus, for example, from four developing devices to one photosensitive member. The present invention can also be applied to an intermediate transfer type color laser printer that forms an agent image and sequentially superimposes it on an intermediate transfer member to form a color image. In the above description, the SRAM 62 is provided in the ASIC 55. However, for example, a DRAM may be provided in the ASIC 55 as the storage unit.
[0121]
【The invention's effect】
  As described above, according to the first aspect of the present invention, when the three color data is converted into the four color data by the data conversion means, the three colors stored in the same row address are stored. Since the color data can be read quickly, a color image can be formed at a high speed by speeding up the color data memory transfer method.
[0122]
  According to the second aspect of the present invention, the cost can be reduced.
[0123]
  According to the third aspect of the present invention, it is possible to further speed up the color data memory transfer method, and to form a color image at high speed.
[0124]
  According to the fourth aspect of the present invention, processing can be performed for each row in the horizontal direction for one page, and a further increase in speed can be achieved by simplifying the control.
[0125]
  According to the invention described in claim 5, it is possible to further increase the speed by simplifying the control.
[0126]
ContractClaim6According to the invention described above, when the three color data is converted into the four color data by the data conversion means, the three color data stored in the SRAM can be read quickly. By increasing the speed of the color data memory transfer method, a color image can be formed at high speed.
[0127]
  Claim7According to the present invention, when the three color data is converted into the four color data by the data conversion means, the three color data stored in the same row address of the second DRAM is quickly converted. Therefore, it is possible to form a color image at a high speed by increasing the speed of the color data memory transfer method.
[0128]
  Claim8According to the invention described in (1), a color image can be formed at the same speed as an image forming apparatus that forms a monochrome image. In addition, in this image forming apparatus, since the speed of the method for transferring the color data memory is increased, the speed of color image formation can be further increased.
[Brief description of the drawings]
FIG. 1 is a side sectional view of an essential part showing an embodiment of a color laser printer as an image forming apparatus of the present invention.
FIG. 2 is a block diagram showing an electrical configuration of the color laser printer shown in FIG.
FIG. 3 is a block diagram showing an embodiment of a memory transfer process executed in the color laser printer.
4 is a diagram showing an actual process in the memory transfer process shown in FIG. 3 in order of steps.
FIG. 5 is a block diagram showing a conventional example of memory transfer processing executed in a color laser printer.
6 is a diagram showing an actual process in the memory transfer process shown in FIG. 5 in the order of steps;
FIG. 7 is a flowchart showing a memory transfer process of color data.
FIG. 8 is a flowchart showing a continuation of the memory transfer process shown in FIG. 7;
FIG. 9 is a block diagram showing another embodiment of the memory transfer process executed in the color laser printer (an aspect set so that three colors of color data for one raster can be stored in the SRAM);
FIG. 10 is a block diagram showing another embodiment of the memory transfer process executed in the color laser printer (a mode in which the first area is assigned to the first DRAM and the second area is assigned to the second DRAM).
[Explanation of symbols]
  1 Color laser printer
  16 Development cartridge
  17 Photosensitive drum
  55 ASIC
  56 CPU
  57a ROM
  57b RAM
  58 First DRAM
  59 Second DRAM
  60 registers
  62 SRAM
  63 1st area
  64 Second area

Claims (8)

A first area of a DRAM that stores three color data consisting of cyan data, magenta data, and yellow data as continuous data for each color data;
Storage means independent of the DRAM having the first area;
A second area of the DRAM independent of the storage means;
Reading means for reading a predetermined amount of continuous data from the first area into the storage means for each color data;
Writing means for writing the continuous data from the storage means into the same row address of the second area so that the three color data of cyan data, magenta data, and yellow data are stored by skipping storage addresses. When,
Means for controlling cyan data, magenta data, and yellow data to be stored in consecutive storage addresses in the second area by repeating reading by the reading means and writing by the writing means for each color for three colors. When,
Data conversion means for reading the color data of the three colors stored in the second area and converting the color data into four color data composed of cyan data, magenta data, yellow data, and black data. An image forming apparatus.   The image forming apparatus according to claim 1, wherein the first area and the second area are assigned to the same DRAM.   The image forming apparatus according to claim 1, wherein the storage unit is an SRAM. The image forming apparatus according to claim 1, wherein continuous data for one raster is stored in the storage unit.   5. The image forming apparatus according to claim 1, wherein one page of color data is stored in the first area for each color data. DRAM that stores three color data consisting of cyan data, magenta data, and yellow data as continuous data that is continuous for each color data;
SRAM,
Reading means for reading a predetermined amount of continuous data from the DRAM so that three color data are stored in the SRAM for each color data;
And data conversion means for reading continuous data of three colors stored in the SRAM and converting the data into four color data consisting of cyan data, magenta data, yellow data, and black data. , Image forming apparatus. A first DRAM for storing three color data consisting of cyan data, magenta data, and yellow data as continuous data continuous for each color data;
A second DRAM independent of the first DRAM;
A predetermined amount of continuous data of each color is read from the first DRAM so that the color data of the three colors of cyan data, magenta data, and yellow data are stored in the same row address of the second DRAM , skipping the storage addresses. Reading means;
Means for controlling the cyan data, the magenta data and the yellow data to be stored in consecutive storage addresses of the second DRAM by repeating the reading by the reading means for each color for three colors ;
Data conversion means for reading color data of three colors stored in the second DRAM and converting the data into four color data consisting of cyan data, magenta data, yellow data, and black data. An image forming apparatus. Cyan, magenta, yellow, and characterized in that it comprises a photoreceptor and a developing device for each color of black, the image forming apparatus according to any one of claims 1 to 7.

Images