JP3659257B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus that performs recording in a dot matrix format by relatively scanning a recording medium and a recording head, and more particularly to an image forming apparatus in which a plurality of recording elements are arranged in a scanning direction on a recording head, such as a color image forming apparatus. .

  Some serial-type image forming apparatuses that relatively scan a recording medium and a recording head have a plurality of recording elements arranged in the scanning direction in the recording head. For example, in an ink jet recording head, when forming a color image, nozzles for recording pixels of Y (yellow), M (magenta), C (cyan), and Bk (black) are equally spaced in the scanning direction. Is arranged.

  When the recording data is so-called raster data in the same direction as the scanning direction, 1 byte (8 bits) is read from the buffer memory in the raster direction, and 8 bits are stored in each storage means for each recording nozzle, for example, a shift register. A plurality of bits (for example, 4 bits) are set, and data of each shift register is recorded in parallel by each recording nozzle in synchronization with the recording timing signal.

  In the conventional recording head, the interval in the scanning direction of each recording nozzle is set to an integer multiple of 4 pixels (that is, 4 dots) corresponding to 4 bits set in the shift register. Data becomes empty at the same time, and the next data to be recorded must be read from the buffer memory to each shift register at once. In particular, when a plurality of recording nozzles for each color are provided in a direction orthogonal to the scanning direction of the recording head and a plurality of dot rows are recorded simultaneously, the data read from the buffer memory is (number of colors) × (number of nozzles in the orthogonal direction) X (8 bits). Since this large amount of data must be processed before the next recording timing is generated, the recording timing cycle must be increased by the time that can process the data, thus increasing the recording speed. I can't.

  The present invention solves the above-described conventional problems and provides an image forming apparatus capable of shortening a recording timing period, that is, increasing a recording speed by distributing data processing.

In order to achieve this object, an image forming apparatus according to claim 1 is provided for each of the recording elements, a recording head for recording in a dot matrix format, in which a plurality of recording elements are arranged in a predetermined direction. A plurality of storage means for storing recording data to be supplied to the recording element, scanning the recording head in the predetermined direction, and a plurality of dots along the predetermined direction in which the recording head is scanned. Each of the recording data is stored for each of the storage means, and when the stored recording data has been supplied to each of the recording elements, new recording data for the plurality of dots is stored in each of the storage means. as target to form a desired image by repeating, in particular, the division position in the predetermined direction of each of the plurality of dots of the recorded data, against the one of the recording element A same position even in the recording data, the interval in the predetermined direction between the recording element is characterized in that it is set to a distance corresponding to the non-integer multiple number of dots of the plurality of dots values.

In the present invention, the division position of the recording data in a predetermined direction for each of the plurality of dots is the same position in the recording data for any recording element , and the interval in the predetermined direction between the recording elements is a plurality of dots. Since the interval corresponding to a value that is not an integral multiple of the number is set, the recording data stored in the storage means is sequentially supplied to each recording element for a plurality of dots and recorded on the recording medium in a dot matrix format. Thus, the recording data for each recording element is written for each of a plurality of dots in the scanning direction at timings shifted from each other. As a result, the recording timing period can be shortened, that is, the recording speed can be increased. it can.

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

  FIG. 1 shows a structure of a main part of a color image forming apparatus. A recording head 30 is mounted on a carriage 31 and is scanned in a horizontal direction X in the drawing along a recording medium such as a recording sheet 33 by a scanning unit. . The scanning means has a known structure in which, for example, the carriage 31 is slidably supported on the guide shaft 32, and the carriage is reciprocally scanned via a belt by a driving source (not shown). The recording paper 33 is transferred in a direction Y (vertical direction in the drawing) substantially perpendicular to the scanning direction X by a transfer means 34 such as a roller. The recording head 30 and the recording paper 33 may be relatively scanned or transported.

  As shown in FIG. 2, the recording head 30 includes the recording units 30Y, 30M, 30C, and 30Bk for recording the three primary colors Y (yellow), M (magenta), and C (cyan) and Bk (black). They are arranged in the scanning direction X. Each recording unit has a large number of recording elements 30s arranged at equal intervals in a direction substantially orthogonal to the scanning direction X (that is, the Y direction). The recording elements 30s of the three primary color recording units 30Y, 30M, and 30C and the Bk (black) recording unit 30Bk are arranged on the same line in the scanning direction X. Note that the array in the Y direction of the multiple recording elements 30s may be an array inclined in the same direction.

  In the present embodiment, the scanning direction interval P (FIG. 2) of the recording elements 30s of the recording units 30Y, 30M, 30C, and 30Bk is the number of dots corresponding to the number of bits in the raster direction that can be stored in a shift register described later. That is, it is set to a width of an integer multiple of 4 dots + 1 dot.

  The recording head 30 is preferably an ink jet type. In this case, the recording element 30s is a nozzle that ejects ink of each color of Y, M, C, and Bk toward the recording paper. As the other recording head, a recording head for recording in a dot matrix format such as a thermal recording head using a heating element as a recording element 30s and an impact recording head using a batting wire as a recording element can be used.

  FIG. 3 shows a schematic configuration for control. Data transmitted in a raster format from a host computer or the like is stored in the buffer memory area 41b of the RAM 41 by the CPU 40. The CPU 40 drives the recording head 30 based on a program stored in the ROM 42 and controls a scanning drive source and a recording paper transfer drive source (not shown) to execute a recording operation.

  The data stored in the buffer memory area 41b of the RAM 41 is bit data that has a one-to-one correspondence with pixels or dots formed by the printing elements. This data is written in storage means provided for each recording unit 30Y, 30M, 30C, 30Bk, for example, shift registers 43Y, 43M, 43C, 43Bk. The CPU 40 functions as reading means from the buffer memory area and writing means from the shift register. Since the data in the buffer memory area 41b is raster data, when the CPU 40 reads it, it is read in units of 1 byte (8 bits) in the raster direction, but the shift registers 43Y, 43M, 43C, 43Bk are 4 in the raster direction. Since it has only the bit width, only the first 4 bits of the read 8 bits are written in the shift registers 43Y, 43M, 43C, 43Bk, and the latter 4 bits of data are discarded. When all the 4-bit data in the shift registers 43Y, 43M, 43C, and 43Bk are sequentially output to the recording unit, the same 8-bit data as described above is read again from the buffer memory area 41b, and the latter 4-bit data is read. Data is written to the shift registers 43Y, 43M, 43C, 43Bk. In this way, the data is sequentially read from the buffer memory area 41b in units of 8 bits in the raster direction, and the first half and the latter half of the 4-bit data are sequentially transferred to the shift registers 43Y, 43M, 43C, and 43Bk based on the timing signal 45 from the CPU 40. Written.

  The buffer memory area 41b and the shift registers 43Y, 43M, 43C, and 43Bk each have the number of bits corresponding to the number of recording elements 30s of each recording unit in the column direction (the direction perpendicular to the raster direction, that is, the vertical direction). At the reading and writing timings, reading and writing in the column direction are also sequentially performed.

  The data in the shift registers 43Y, 43M, 43C, 43Bk is output and stored in the latch circuits 46Y, 46M, 46C, 46Bk one column at a time based on the timing signal. The output data of the latch circuits 46Y, 46M, 46C, and 46Bk is output to the driver circuit 48 by the AND gate 47 based on the logical product with the timing signal. As a result, the recording element 30s of each recording unit is driven. For example, in an ink jet head, ink droplets are ejected toward a recording medium and recorded in a dot matrix format.

  4 schematically shows the buffer memory 41b of the present embodiment, FIG. 5 schematically shows the relationship between the shift registers 43Y, 43M, 43C, and 43Bk and the print unit, and FIG. 6 schematically shows the write timing to the shift register. , B7 to b0 in the figure represent raster direction bits.

  In the present embodiment, the interval P in the scanning direction of each of the recording units 30Y, 30M, 30C, and 30Bk is set to an integer multiple of 4 dots + 1 dot as described above. In FIG. 55, the interval P is set to 5 dots in order to simplify the drawing. Therefore, as shown in FIG. 5, when the Y recording unit 30Y records the data “b0” of the shift register 30Y, the M recording unit 30M performs the shift of the data “b5” of the shift register 30M, and the C recording unit 30C performs the shift. The data “b2” in the register 30C and the data “b7” in the shift register 30Bk are recorded by the Bk recording unit 30Bk, respectively. That is, data at positions shifted from each other by 1 bit within 4 bits of each shift register is supplied to each recording unit at each recording timing.

  Since each shift register stores 4 bits in the raster direction as described above, in the state of FIG. 5, the next recording is performed in the shift register 30Y for the Y recording unit until the next recording timing signal is generated. The power data b7 to b4 must be written. At this time, since data remains in the other shift registers 30M, 30C, and 30Bk, it is not necessary to write them yet. However, at this next recording timing, data b3 to b0 to be printed next must be written in the shift register 30M for the M recording unit. When the CPU 40 reads 8-bit data for the Y recording unit from the buffer memory 41b and writes 4 bits to the shift register 30Y, the CPU 40 reads the data for the Y recording unit from the data for the Y recording unit in the buffer memory 41b at the next recording timing. The 8-bit data for the M recording unit at a position separated by (integer multiple of 4 dots) in the interval P is read and 4 bits are written in the shift register 30M. In this way, the data of each color is read out from the buffer memory 41b by one timing at a time, and each shift register 43Y, 43M, 43C, 43Bk reads 1 from each other at the time indicated by the black mark in FIG. It will be written at different timings.

  Therefore, reading from the buffer memory 41b and writing to the shift register are performed for each color, that is, one recording unit at each timing, and processing of all color data is concentrated at one timing as in the prior art. There is nothing. In other words, by performing the processing in a distributed manner at each recording timing, the recording timing cycle can be shortened, and as a result, the recording speed can be increased.

  FIG. 7 shows another embodiment of the present invention. The same reference numerals are given to the same parts as those of the above-mentioned embodiment, and the description is omitted.

  In the embodiment, the CPU 40 reads data for each recording unit from the respective positions corresponding to the interval P in the buffer memory 41b. In this embodiment, the shift register is included in the interval P. The delay circuits 44Y, 44M, 44C, and 44Bk cause a delay corresponding to an integer multiple of the number of dots N in the raster direction that can be stored in the delay circuit 44.

  That is, when the interval P is (integer multiple of the dot number N) + (1 dot), the CPU 40 reads data for each recording unit from the same position in the buffer memory 41b at each recording timing. And output to the delay circuits 44Y, 44M, 44C and 44Bk. Each delay circuit performs a time corresponding to (integer multiple of the number of dots N) of the interval P to the adjacent recording unit, and writes data to the respective shift registers 43Y, 43M, 43C, and 43Bk. . Therefore, the same data as in the above embodiment is created in each shift register.

  The delay data of the delay circuits 44Y, 44M, 44C, and 44Bk is rewritten every time the scanning direction of the recording head 30 is reversed.

  Also in this embodiment, since the CPU 40 performs reading from the buffer memory 41b for each color, that is, one recording unit at each timing, the processing of all color data at one timing as in the prior art. Therefore, the same effect as in the above embodiment can be achieved.

  In both the above embodiments, the interval P in the scanning direction of each recording unit 30Y, 30M, 30C, 30Bk is set to an integer multiple of 4 dots + 1 dot, but when 8-bit data can be stored in the shift register. The same effect can be achieved by using an integral multiple of 8 dots + 2 dots. In short, the interval P is not an integer multiple of the number of dots N corresponding to the number of bits in the raster direction that can be stored in the shift register, for example, (integer multiple of the number of dots N) + (predetermined number of dots not equal to the number of dots N). By doing so, it is possible to avoid data reading and writing processing from being concentrated on one recording timing. Note that if the integer multiple of 4 dots + 2 dots or the integral multiple of 8 dots + 4 dots, the data processing for the two shift registers is overlapped. The number of dots equal to or smaller than the value divided by the number). That is, for example, by setting the integral multiple of 4 dots + 1 dot, the integral multiple of 8 dots + 2 dots, or the integral multiple of 8 dots + 1 dot, the data processing for the buffer memory and each shift register does not overlap as described above. Of course, the position where the CPU 40 reads data for different recording units in the buffer memory is changed in units of 8 dots in accordance with the size of the interval P.

  The present invention is not limited to the apparatus for recording the three primary colors + black as in the above-described embodiments, but also an apparatus having an arbitrary plurality of colors, or a plurality of one-color recording elements arranged in the scanning direction to form one row for each element. The present invention can also be applied to an apparatus for recording in a shared manner.

1 is a main part mechanism diagram of an image forming apparatus according to an embodiment of the present invention. The enlarged front view of a recording head. The block diagram of a control structure. FIG. 3 is a diagram schematically showing a buffer memory. FIG. 3 is a diagram schematically showing a relationship between a recording unit and a shift register. The figure which shows the write-in timing to a shift register graphically. The block diagram of the control structure of other embodiment.

Explanation of symbols

30 recording head 30s recording element 30Y, 30M, 30C, 30Bk recording unit 41b buffer memory 43Y, 43M, 43C, 43Bk storage means (shift register)

Claims (1)

A recording head for recording in a dot matrix format, in which a plurality of recording elements are arranged in a predetermined direction;
A plurality of storage means for storing recording data provided for each of the recording elements and supplied to each of the recording elements;
Scanning the recording head in the predetermined direction, storing the recording data for each of a plurality of dots along the predetermined direction in which the recording head is scanned for each storage means, and the stored recording data In the image forming apparatus for forming a desired image by repeatedly storing new recording data for the plurality of dots in the storage means when the supply to the recording elements is completed.
The division position in the predetermined direction for each of the plurality of dots of the recording data is the same position in the recording data for any recording element,
2. The image forming apparatus according to claim 1, wherein an interval between the recording elements in the predetermined direction is set to an interval corresponding to a value that is not an integral multiple of the number of dots of the plurality of dots .

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