JP2018138339A - Printer and printing control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a printer capable of performing high quality printing irrespective of sheet characteristics and printing density.SOLUTION: A printer comprises: a thermal head being disposed so as intersect with a conveyance direction of a sheet and printing a plurality of printing data for each line; a stepping motor of which driving is controlled by a driving signal and which relates to sheet conveyance; a correction value storage part storing a plurality of correction values; a correction value selection part selecting an appropriate correction value from the correction value storage part on the basis of sheet characteristics of the sheet input from the outside; a mean density value calculation part calculating a printing density mean value on the basis of the plurality of printing data including one printing data; a driving signal calculation part calculating the driving signal on the basis of the correction value selected and the printing density mean value calculated; and a driving control part controlling the driving of the stepping motor by the driving signal. The thermal head prints the one printing data on the sheet conveyed by the stepping motor of which the driving is controlled by the driving signal.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a printing apparatus and a printing control method, and more particularly to a paper conveyance technique.

  The stepping motor rotates by an angle corresponding to the number of pulses of the pulse signal input to the driver. Therefore, stepping motors are widely used in printing apparatuses because they can easily and precisely control the rotation of a rotating object without requiring feedback control.

  As described above, the stepping motor has an advantage that rotation control is easy, while it has a possibility of stepping out when excessive torque is applied from the outside during driving in the through region.

  In a color printer that prints multiple colors and outputs an image, if one stepping motor that controls the rotation of the transport roller steps out, printing for each color is possible even if the other stepping motors are driven normally. The position is misaligned and printing fails. Therefore, the color printer is required to have a margin for the stepping motor step-out.

  One method for securing a margin for step-out is to increase the drive current input to the stepping motor. However, when the drive current is increased, the vibration generated from the stepping motor is also increased. The stepping motor repeats driving and stopping for each pulse of the pulse signal. Therefore, when the torque increases, rotational fluctuations and vibrations due to acceleration changes associated with the driving and stopping operations increase. For example, rotational fluctuation or vibration of a stepping motor connected to an ink sheet or a conveyance roller is reflected in an image as density unevenness.

  In order to solve such a problem, for example, Patent Document 1 proposes a stepping motor drive control method capable of suppressing density unevenness while preventing the occurrence of stepping out of the stepping motor.

JP 2004-064898 A

  In the image forming apparatus described in Patent Document 1, the driving current supplied to the stepping motor is increased during acceleration / deceleration driving of the stepping motor, and the driving current is switched so as to be smaller than that during acceleration / deceleration driving during constant speed driving. Yes. Thus, the image forming apparatus can take a large margin for step-out during acceleration / deceleration driving, and can suppress vibration and rotation unevenness during constant-speed driving. However, since the paper conveyance load changes depending on the paper characteristics and printing density, there is a problem that the drive current must be set large even during constant speed driving.

  In addition, sticking, that is, skipping of printing or noise occurs due to adhesion between the print medium (paper and ink sheet) and the thermal head even at the boundary between the low and high image density lines. There is a problem that the driving current of the stepping motor must be set large in order to suppress the adhesion between the print media and the thermal head.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a printing apparatus that can cope with fluctuations in paper characteristics and printing density and can perform high-quality printing.

  The printing apparatus according to the present invention is arranged to have a longitudinal direction in a direction intersecting the paper transport direction, and a plurality of print data for each line corresponding to the longitudinal direction is arranged for each print data in the paper transport direction. A thermal head that prints on the sheet, a stepping motor whose rotation is controlled by a drive signal and rotating a roller that conveys the sheet, a correction value storage unit that stores a plurality of correction values of the drive signal according to a plurality of sheet characteristics, A correction value selection unit that selects at least one correction value from a plurality of correction values stored in the correction value storage unit based on the paper characteristics of the paper input from the outside, and a plurality of print data including one print data Based on the density average value calculation unit that calculates one print density average value, at least one correction value selected by the correction value selection unit, and one print density level calculated by the density average value calculation unit. Based on the value, it comprises a drive signal calculating unit for calculating a first drive signal, a drive control unit for controlling the driving of the stepping motor according to one of the drive signal calculated by the drive signal calculating section. The thermal head prints one print data on a sheet conveyed by a roller rotated by a stepping motor whose drive is controlled by one drive signal.

  According to the present invention, it is possible to provide a printing apparatus that can cope with fluctuations in paper characteristics and printing density and can perform high-quality printing. In particular, the printing apparatus of the present invention can optimally control the driving signal of the stepping motor in accordance with the load variation with respect to the paper characteristics and the printing density for each line, and the stepping motor can be stepped out or the ink sheet can be stuck. To prevent.

1 is a block diagram illustrating a configuration of a printing apparatus according to an embodiment. It is a figure which shows an example of the correction value table of the printing apparatus which concerns on embodiment. 1 is a diagram schematically illustrating a configuration of a processing circuit of a printing apparatus according to an embodiment. 1 is a diagram schematically illustrating a configuration of a printing apparatus according to an embodiment. 3 is a flowchart illustrating a printing control method of the printing apparatus according to the embodiment. FIG. 4 is a plan view illustrating an example of a print image printed by the printing apparatus according to the embodiment. It is a graph which shows the change of the drive current of the stepping motor when the printing apparatus which concerns on embodiment prints a printing image.

  Embodiments of a printing apparatus and a printing control method according to the present invention will be described.

  FIG. 1 is a block diagram showing a main configuration of a printing apparatus according to an embodiment of the present invention. In the present embodiment, the printing apparatus 1 can communicate with an external information terminal 2 such as a personal computer, for example, and includes an interface 3 for the communication.

  In FIG. 1, a printing apparatus 1 includes an interface 3 (hereinafter referred to as I / F 3), a system control unit 4, a print control unit 5, a thermal head 6, a drive control unit 7, a stepping motor 8, And an ink sheet conveying motor 9. The printing apparatus 1 performs printing by transferring ink on an ink sheet onto a sheet by a thermal head 6 controlled by a print control unit 5, a stepping motor 8 and an ink sheet transport motor 9 controlled by a drive control unit 7. Is. The thermal head 6 has a length in a direction intersecting with the sheet conveyance direction, and performs printing for each line corresponding to the length direction.

  Next, each component of the printing apparatus 1 will be described in detail.

  The I / F 3 can communicate with the information terminal 2 and receives and acquires print information from the information terminal 2. The I / F 3 is, for example, a USB interface. The print information acquired by the I / F 3 includes image data to be printed and information related to paper characteristics such as paper size. The paper characteristics are paper characteristics of the paper on which the image data included in the print information is printed. The paper size is a predetermined paper size that is made into a sheet, and is 8 × 4 inches, for example. These paper sizes correspond to the paper sizes conveyed in the printing apparatus 1 immediately before discharge.

  The system control unit 4 comprehensively controls each component of the printing apparatus 1 such as the print control unit 5 and the drive control unit 7 based on the print information received by the I / F 3. The system control unit 4 processes the image data and paper size information included in the print information, and generates a plurality of print data for each line. The system control unit 4 controls the print control unit 5 based on the print data, and further controls the driving of the thermal head 6 via the print control unit 5. Further, the system control unit 4 controls the drive control unit 7 based on the print data, and further controls the stepping motor 8 and the ink sheet transport motor 9 via the drive control unit 7. That is, the system control unit 4 controls image printing via the print control unit 5, and controls paper conveyance and ink sheet conveyance via the drive control unit 7.

  The system control unit 4 includes a correction table storage unit 4a that is a correction value storage unit, a correction value selection unit 4b, a density average value calculation unit 4c, a drive current calculation unit 4d that is a drive signal calculation unit, and an interline A density comparison unit 4e and a control signal output unit 4f are included.

  The correction table storage unit 4a stores a correction table including a plurality of correction values. The plurality of correction values correct the drive current that controls the driving of the stepping motor 8. FIG. 2 is a diagram illustrating an example of the correction table. The plurality of correction values are defined according to a plurality of sheet characteristics such as a plurality of predetermined sheet sizes or a plurality of sheet thicknesses. For example, each correction value α may be structurally calculated in consideration of the paper size or paper thickness, or compatibility with the grip roller 22 described later, or may be experimentally measured. The correction table storage unit 4a is an example of a correction value storage unit, and is not limited thereto.

  The correction value selection unit 4b selects at least one appropriate correction value from a plurality of correction values stored in the correction table storage unit 4a based on the sheet characteristics included in the print information received by the I / F 3. .

  The density average value calculation unit 4c includes, among a plurality of print data for each line, one print data corresponding to one line and a plurality of prints corresponding to the front or rear of the one line with respect to the paper transport direction. One print density average value is calculated from the data.

  The drive current calculation unit 4d, which is a drive signal calculation unit, is based on at least one correction value selected by the correction value selection unit 4b and one print density average value calculated by the density average value calculation unit 4c. Is calculated. The one drive current is a drive current input to the stepping motor 8 when one print data is printed.

  The inter-line density comparison unit 4e corrects one drive current based on one print density average value and another print density average value. Other print density average values are other print data corresponding to other lines located next to one line on which one print data is printed, and the front or rear of other lines with respect to the paper transport direction. The average value of the print density calculated from a plurality of print data to be printed. For example, when the difference between one print density average value and another print density average value is greater than or equal to a threshold value, the interline density comparison unit 4e corrects the one drive current calculated by the drive current calculation unit 4d.

  The control signal output unit 4f generates a control signal (pulse signal) corresponding to the drive current so that the drive current corrected by the interline density comparison unit 4e is output from the drive control unit 7 to the stepping motor 8. To the drive control unit 7.

  The drive control unit 7 outputs a drive current based on the control signal output from the control signal output unit 4 f to the stepping motor 8. That is, the drive control unit 7 controls the driving of the stepping motor by the drive current calculated by the interline density comparison unit 4e. Further, the drive control unit 7 controls the ink sheet transport motor 9 that winds up the ink sheet based on a signal output from the system control unit 4.

  The stepping motor 8 is rotationally driven by the drive current supplied from the drive control unit 7. The drive current supplied to the stepping motor 8 can be adjusted by a control signal output from the system control unit 4 to the drive control unit 7. Here, the drive current can be adjusted by variously adjusting the voltage level of the control signal via a D / A converter (not shown). Further, for example, the value of the drive current is set by a data value of a plurality of bits.

  The print control unit 5 generates drive data for the thermal head 6 based on the print data generated by the system control unit 4, and outputs the drive data to the thermal head 6.

  The thermal head 6 performs printing on a sheet based on drive data output from the print control unit 5.

  FIG. 3 is a diagram schematically illustrating a configuration of a processing circuit included in the printing apparatus 1. The system control unit 4, the print control unit 5, and the drive control unit 7 are composed of at least one processing circuit. The processing circuit includes a CPU (Central Processing Unit) 31 and a storage unit 32, and can input print information from the I / F 3.

  The storage unit 32 realizes the function of the correction table storage unit 4a. That is, the correction table is stored in the storage unit 32. Functions of the system control unit 4 such as the correction value selection unit 4b, the density average value calculation unit 4c, the drive current calculation unit 4d, the interline density comparison unit 4e, and the control signal output unit 4f, and the print control unit 5 and the drive control unit 7 The function is described as a control program. The control program is stored in the storage unit 32. When the CPU 31 executes the control program stored in the storage unit 32, the functions of the system control unit 4, the print control unit 5, and the drive control unit 7 are realized.

  The storage unit 32 includes a non-volatile memory such as a flash memory and a temporary storage memory such as a RAM (Random Access Memory). The nonvolatile memory stores a correction table, a control program for printing, various initial values, and the like. The temporary storage memory is a working memory, and temporarily stores data for storing and processing image data related to printing, such as print information, print data, drive data, and drive current being calculated.

  FIG. 4 is a diagram schematically showing a configuration of the printing apparatus 1 according to the present embodiment, and schematically shows a cross section. The printing apparatus 1 includes pinch rollers 21 and 23 and a grip roller 22, and a sheet 20 and an ink sheet 24 are mounted. The paper 20 may be roll paper or cut paper.

  The paper 20 mounted on the printing apparatus 1 is sandwiched between a pinch roller 21 and a grip roller 22. The grip roller 22 is connected to the stepping motor 8 controlled by the drive control unit 7 described above, and rotates by the driving force of the stepping motor 8. The paper 20 is transported in the paper transport direction indicated by the arrow by the rotation of the grip roller 22.

  The ink sheet 24 is supplied together with the paper 20 between the thermal head 6 and the pinch roller 23 facing the thermal head 6. The ink sheet 24 is supplied between the thermal head 6 and the pinch roller 23 as the ink sheet conveyance motor 9 controlled by the drive control unit 7 rotates. The paper 20 is pressed and heated together with the ink sheet 24 by the thermal head 6 and the pinch roller 23, and as a result, an image is printed on the paper 20.

  The thermal head 6 is arranged with a length in a direction intersecting with the conveyance direction of the paper 20. The longitudinal direction is the direction perpendicular to the paper surface in FIG. The thermal head 6 performs printing for each line corresponding to the longitudinal direction. That is, the printing apparatus 1 prints a plurality of print data for each line while conveying the paper 20 for each print data.

<Operation>
FIG. 5 is a flowchart illustrating a printing control method by the printing apparatus 1 according to the present embodiment. Specifically, the control operation of the printing apparatus 1 that controls the drive current of the stepping motor 8 is shown based on the correction value related to the paper characteristics, the print density average value calculated from a plurality of print data, and the inter-line density difference. ing.

  First, in step S1, the I / F 3 obtains print information including image data and paper characteristics such as paper width or thickness from the outside. Further, the system control unit 4 processes the print information acquired by the I / F 3 and generates a plurality of print data to be printed for each line.

  In step S2, the correction value selection unit 4b selects the correction value α from the correction table stored in the correction table storage unit 4a based on the sheet characteristics received by the I / F 3. For example, the correction value selection unit 4b selects a larger correction value α as the paper width or thickness is larger. Alternatively, for example, the correction value selection unit 4 b may select the correction value α according to the compatibility between the paper 20 and the grip roller 22. In the present embodiment, only one correction value α is selected, but the present invention is not limited to this, and a plurality of correction values may be selected. The above step S2 is a correction value selection step.

In step S3, the density average value calculation unit 4c presents the print data corresponding to the i-th line to be printed at the present time, that is, at that time, and a plurality of lines corresponding to the number of lines preceding the i-th line. The print density average value D _i is calculated from the print data and stored in the storage unit 32. Here, i = 1, 2,..., N, 1 is an initial value indicating the first line of an image printed by a plurality of print data, and n is a value indicating the final line of the image.

In step S4, the density average value calculation unit 4c prints the print density from the print data corresponding to the (i + 1) th line and a plurality of print data corresponding to several lines ahead from the (i + 1) th line. The average value D _{i + 1} is calculated and stored in the storage unit 32. The above steps S3 and S4 are density average value calculation steps.

In step S5, the drive current calculation unit 4d outputs print data to the i-th line based on the correction value α selected in step S2 and the print density average value D _i calculated in step S3. A drive current I _i of the stepping motor 8 at the time of printing is calculated. The following formula (1) is the calculation formula, and the conversion coefficient k converts the print density average value D _i to the drive current I _i . Here, the print density average value D _i of the image and the drive current I _i have a linear relationship, and in particular, here have a proportional relationship. The above step S5 is a drive signal calculation step.

In step S6, the inter-line density comparison unit 4e determines whether the difference between the i-th print density average value D _i and the (i + 1) -th print density average value D _{i + 1} is equal to or greater than a threshold value.

If the difference between the case in step S6 is YES i.e. above printing density average value is equal to or larger than the threshold value, in step S7, the line between the concentration comparing unit 4e corrects the driving current I _i. Specifically, in order to further increase the torque of the stepping motor 8, the inter-line density comparison part 4e adds the correction value β to the driving current I _i. The above steps S6 and S7 are inter-line density comparison steps.

In step S8, so that the drive current I _i calculated in step S7 is outputted from the drive control unit 7 to the stepping motor 8, the control signal output section 4f control signal (pulse signal corresponding to the driving current I _i ) To the drive control unit 7. The drive control unit 7 supplies a drive current I _i based on the control signal to the stepping motor 8. That is, the drive control unit 7 controls the driving of the stepping motor by the drive current I _i calculated by the interline density comparison unit 4e.

Alternatively, if NO in step S7, that is, if the difference between the print density average values is less than the threshold value, in step S8, the drive current I _i calculated in step S5 is supplied from the drive control unit 7 to the stepping motor 8. The control signal output unit 4 f outputs a control signal (pulse signal) corresponding to the drive current I _i to the drive control unit 7. The drive control unit 7 controls the drive by outputting a drive current I _i based on the control signal to the stepping motor 8. That is, the drive control unit 7 controls the driving of the stepping motor by the drive current I _i calculated by the drive current calculation unit 4d. The above step S8 is a drive control step.

  In step S9, the system control unit 4 determines whether printing has been performed up to the nth line which is the final line of the print image. If it is not the last line, the process proceeds to the next (i + 1) th line in step S10, and step S3 and subsequent steps are repeated. If it is the last line, the print control is terminated.

  Next, a print image printed by the printing apparatus 1 by the print control method from step S1 to step S10 and control data of the stepping motor 8 at the time of printing are shown. FIG. 6 is a plan view schematically showing an example of a print image 41 printed on the paper 20 by the printing apparatus 1. FIG. 7 is a graph showing changes in the drive current of the stepping motor 8 when the print image 41 is printed. 6 corresponds to the time indicated on the horizontal axis in FIG.

The printing apparatus 1 changes the drive current I _i of the stepping motor 8 according to the print density average value D _i of the print image 41. At that time, the printing apparatus 1 calculates the print density average value D _i up to several lines ahead for each line by the density average value calculation unit 4c.

  When printing a high density region 42 having a high print density as shown in FIG. 6, there is a risk that the conveyance load of the paper 20 increases or the ink sheet 24 sticks. Therefore, as shown in FIG. 7, the printing apparatus 1 sets the driving current of the stepping motor 8 to a large value, and conveys the paper 20 with a torque that does not cause step-out and sticking.

  On the other hand, when printing the low density region 43 having a low print density as shown in FIG. 6, the printing apparatus 1 sets the drive current to a small value as shown in FIG. Thereby, the printing apparatus 1 reduces the torque of the stepping motor 8 and suppresses the vibration and rotation fluctuation. As a result, the printing apparatus 1 can suppress density unevenness of the printed image 41.

The drive control unit 7 of the printing apparatus 1 may control the drive current for driving the ink sheet conveyance motor 9 in association with the drive current of the stepping motor 8 calculated by the drive current calculation unit 4d. In that case, in step S8 shown in FIG. 5, the drive control unit 7 controls the drive of the stepping motor 8 by outputting the drive current I _i calculated by the drive current calculation unit 4d to the stepping motor 8 and driving the stepping motor 8. A drive current based on the current I _i is output to the ink sheet transport motor 9 to control the drive of the ink sheet transport motor 9.

In the vicinity of the boundary between the high concentration region 42 shown in FIG. 6 and the low density region 43, and the print density average value D _i of the i-th line, then print (i + 1) Print density average of th line D _{i + 1} And the difference becomes larger. When the difference between the print density average values is large, printing skipping or noise called sticking occurs. Therefore, when the difference in the print density average values is equal to or greater than a certain threshold, the printing apparatus 1 sets the drive current of the stepping motor 8 to a large value as shown in FIG. Thereby, the printing apparatus 1 can suppress the sticking between the paper 20 or the ink sheet 24 and the thermal head 6.

The drive control unit 7 of the printing apparatus 1 may control the drive current for driving the ink sheet transport motor 9 in association with the drive current corrected by the interline density comparison unit 4e. In this case, in step S8 shown in FIG. 5, the drive control unit 7 controls the driving of the stepping motor 8 by outputting the driving current I _i corrected by the interline density comparison unit 4e to the stepping motor 8, and A drive current based on the drive current I _i is output to the ink sheet transport motor 9 to control the drive of the ink sheet transport motor 9.

Note that the printing apparatus 1 shown in the present embodiment includes the interline density comparison unit 4e, but in the case of a printing apparatus that does not include the interline density comparison unit 4e, step S4, step S6, and step S7 in FIG. Is omitted. A printing apparatus that does not include the interline density comparison unit 4e can change the drive current I _i of the stepping motor 8 according to the correction value α and the print density average value D _{i of} the print image 41. As a result, step-out and sticking can be suppressed when the high-density region 42 is printed, and density unevenness of the printed image 41 due to vibration and rotation fluctuation of the stepping motor 8 can be suppressed when the low-density region 43 is printed. .

<Summary of Embodiment>
In summary, the printing apparatus 1 according to the present embodiment is arranged with a length in a direction intersecting the conveyance direction of the paper 20, and a plurality of print data for each line corresponding to the length is sent to the paper 20. In the transport direction, a thermal head 6 that prints for each print data, a stepping motor 8 that is driven by a drive signal and rotates a roller that transports the paper 20, and a plurality of drive signals corresponding to a plurality of paper characteristics. Based on the correction value storage unit (correction table storage unit 4a) for storing correction values and the sheet characteristics of the sheet 20 input from the outside, at least one correction value is selected from the plurality of correction values stored in the correction table storage unit 4a. a correction value selection section 4b for selecting alpha, based on the plurality of print data including one of the print data, and the average density value calculation section 4c that calculates the one print density average D _i, the correction value At least one of the correction value α is selected by the selecting section 4b, based on the one print density average value D _i calculated by the average density value calculation section 4c, a drive signal calculating unit for calculating the one drive signal, And a drive control unit 7 that controls the driving of the stepping motor 8 by one drive signal calculated by the drive signal calculation unit. The thermal head 6 prints one print data on a sheet 20 conveyed by a roller rotated by a stepping motor 8 whose drive is controlled by one drive signal.

The drive signal for controlling the drive of the stepping motor 8 is the drive current I _i in the present embodiment, and the drive signal calculation unit is the drive current calculation unit 4d.

With the configuration as described above, the printing apparatus 1 optimally sets the drive current I _i of the stepping motor 8 according to the paper characteristics and the print density average value D _i , and performs step-out or ink with respect to load fluctuations during constant speed driving. The sticking of the sheet 24 can be prevented. Then, the printing apparatus 1 calculates the print density average value D _i for each line, and sets the drive current I _i to a small value when the print density average value D _i is low. Thereby, the printing apparatus 1 can form a high-quality image with little density unevenness due to vibration or rotation fluctuation of the stepping motor 8.

  Further, the printing apparatus in which the driving signal for controlling the driving of the stepping motor 8 is the driving voltage also has the same effect as that of the present embodiment. In this case, the drive current calculation unit 4d is a drive voltage calculation unit, and the drive control unit 7 controls the driving of the stepping motor 8 by the drive voltage calculated by the drive voltage calculation unit.

Further, the density average value calculation unit 4c of the printing apparatus 1 uses another print density average value D based on a plurality of print data including other print data printed on the line adjacent to one print data in the paper 20. _{i + 1} is further calculated. The printing apparatus 1 further includes an interline density comparison unit 4e that corrects one drive current I _i based on one print density average value D _i and another print density average value D _{i + 1} . The drive control unit 7 controls the driving of the stepping motor 8 by the one drive current I _i corrected by the interline density comparison unit 4e.

With such a configuration, the printing apparatus 1 sets the drive current I _i to a large value even when there is a large difference in the print density between the lines, that is, at the boundary between the low print density and the high line. As a result, sticking, that is, skipping of printing and generation of noise can be suppressed.

  When the drive signal for controlling the driving of the stepping motor 8 is a drive voltage, the interline density comparison unit 4e corrects the drive voltage, and the drive control unit 7 corrects the drive voltage corrected by the interline density comparison unit 4e. Thus, the driving of the stepping motor 8 is controlled.

The printing apparatus 1 further includes an ink sheet transport motor 9 that transports the ink sheet 24 supplied between the thermal head 6 and the paper 20. The drive control unit 7 controls the drive of the ink sheet conveyance motor 9 in association with one drive current I _i calculated by the drive current calculation unit 4d.

  With this configuration, the printing apparatus 1 causes the ink sheet transport motor 9 to step out and stick when printing the high density region 42, and the ink sheet transport motor 9 to print the low density region 43. It is possible to suppress density unevenness of the printed image 41 due to vibration and rotation fluctuation.

The printing apparatus 1 further includes an ink sheet transport motor 9 that transports the ink sheet 24 supplied between the thermal head 6 and the paper 20. The drive control unit 7 controls the drive of the ink sheet conveyance motor 9 in association with one drive current I _i corrected by the interline density comparison unit 4e.

  With such a configuration, the printing apparatus 1 can prevent sticking, that is, skipping of printing and generation of noise even when there is a large difference in print density between lines, that is, at the boundary between a line with a low print density and a high line. Can be suppressed.

Further, according to the printing control method in the present embodiment, the thermal head 6 having a length in the direction intersecting the transport direction of the paper 20 outputs a plurality of print data for each line corresponding to the length in the transport direction of the paper 20. And a print control method for printing for each print data, based on the sheet characteristics of the sheet 20 input from the outside, at least one of a plurality of correction values stored in the correction value storage unit (correction table storage unit 4a). Correction value selection step for selecting one correction value α, density average value calculation step for calculating one print density average value D _i based on a plurality of print data including one print data, and correction value selection step at least one of the correction value α is selected, based on the one print density average value D _i calculated by the average density value calculation step, one that controls the driving of the stepping motor 8 A driving signal calculating step for calculating a motion signal, a driving control step for controlling the driving of the stepping motor 8 by one driving signal calculated in the driving signal calculating step, and a stepping motor for which driving is controlled by one driving signal The thermal head 6 includes a printing step in which one print data is printed on the sheet 20 conveyed by the roller rotated by the roller 8.

The driving signal for controlling the driving of the stepping motor 8 is the driving current I _i in the present embodiment.

In the printing control method including such a configuration, the driving current I _i of the stepping motor 8 is set according to the paper characteristics and the printing density average value D _i, and the step-out with respect to the load fluctuation at the constant speed driving or the ink sheet The sticking of 24 can be prevented. Further, the printing control method calculates the printing density average value D _i for each line, and sets the driving current I _i to a small value when the printing density average value D _i is low. Thereby, according to this printing control method, it is possible to form a high-quality image with little density unevenness due to vibration or rotation fluctuation of the stepping motor 8.

  When the drive signal for controlling the drive of the stepping motor 8 is a drive voltage, the drive voltage is calculated in the drive signal calculation step, and the drive of the stepping motor 8 is controlled by the calculated drive voltage.

Further, the density average value calculating step of the print control method described above is based on a plurality of print data including other print data printed on the line adjacent to one print data in the paper 20, and other print density average values. _{Di + 1} is further calculated. The print control method further includes an inter-line density comparison step for correcting one drive current I _i based on the difference between one print density average value D _i and another print density average value D _{i + 1} . In the drive control step, the driving of the stepping motor is controlled by the drive current I _i corrected in the inter-line density comparison step.

According to the print control method including such a configuration, the drive current I _i is set to a large value even when there is a large difference in print density between lines, that is, at the boundary between a line with a low print density and a high line. By doing so, sticking, that is, printing skipping and noise generation can be suppressed.

  When the drive signal for controlling the driving of the stepping motor 8 is a drive voltage, the interline density comparison unit 4e corrects the drive voltage, and the drive control unit 7 corrects the drive voltage corrected by the interline density comparison unit 4e. Thus, the driving of the stepping motor 8 is controlled.

The drive control step of the printing control method controls the drive of the ink sheet transport motor 9 in association with the one drive current I _i calculated in the drive signal calculation step. According to the printing control method including such a configuration, the ink sheet conveyance motor 9 is stepped out and stuck when the high density area 42 is printed, and the ink sheet conveyance motor is printed when the low density area 43 is printed. 9 can suppress the density unevenness of the printed image 41 due to the vibration and rotation fluctuation of 9.

In the drive control step of the printing control method described above, the drive of the ink sheet transport motor 9 is controlled in association with one drive current I _i corrected by the inter-line density comparison step. According to the print control method including such a configuration, even when there is a large difference in print density between lines, that is, at the boundary between a line with a low print density and a high line, sticking, that is, print skipping and noise Occurrence can be suppressed.

  In the present invention, the embodiments can be appropriately modified and omitted within the scope of the invention. Although the present invention has been described in detail, the above description is illustrative in all aspects, and the present invention is not limited thereto. It is understood that countless variations that are not illustrated can be envisaged without departing from the scope of the present invention.

  1 printing device, 2 information terminal, 3 interface, 4 system control unit, 4a correction table storage unit, 4b correction value selection unit, 4c density average value calculation unit, 4d drive current calculation unit, 4e interline density comparison unit, 4f control Signal output unit, 5 Print control unit, 6 Thermal head, 7 Drive control unit, 8 Stepping motor, 9 Ink sheet transport motor, 20 Paper, 21 Pinch roller, 22 Grip roller, 23 Pinch roller, 24 Ink sheet, 41 Print image 42 High concentration region, 43 Low concentration region.

Claims (10)

A thermal head that is arranged with a length in a direction intersecting with the paper transport direction and prints a plurality of print data for each line corresponding to the length in the transport direction of the paper for each print data. When,
A stepping motor that is driven by a drive signal and that rotates a roller that conveys the paper;
A correction value storage unit that stores a plurality of correction values of the drive signal according to a plurality of paper characteristics;
A correction value selection unit that selects at least one of the correction values from the plurality of correction values stored in the correction value storage unit based on the paper characteristics of the paper input from the outside;
A density average value calculating unit that calculates one print density average value based on a plurality of the print data including the one print data;
A drive signal calculation unit that calculates one drive signal based on at least one correction value selected by the correction value selection unit and the one print density average value calculated by the density average value calculation unit When,
A drive control unit that controls the drive of the stepping motor by the one drive signal calculated by the drive signal calculation unit;
The thermal head is a printing apparatus that prints the one print data on the sheet conveyed by the roller rotated by the stepping motor whose driving is controlled by the one drive signal. The concentration average value calculation unit
Based on a plurality of the print data including other print data to be printed on the line adjacent to the one print data in the paper, further calculating another print density average value,
The printing apparatus includes:
Further comprising an inter-line density comparison unit for correcting the one drive signal based on the one print density average value and the other print density average value.
The printing apparatus according to claim 1, wherein the drive control unit controls the drive of the stepping motor by the one drive signal corrected by the interline density comparison unit. An ink sheet transport motor for transporting an ink sheet supplied between the thermal head and the paper;
The printing apparatus according to claim 1, wherein the drive control unit controls the drive of the ink sheet conveyance motor in association with the one drive signal calculated by the drive signal calculation unit. An ink sheet transport motor for transporting an ink sheet supplied between the thermal head and the paper;
The printing apparatus according to claim 2, wherein the drive control unit controls the drive of the ink sheet conveyance motor in association with the one drive signal corrected by the interline density comparison unit.   The printing apparatus according to any one of claims 1 to 4, wherein the drive signal for controlling the drive of the stepping motor is a drive current or a drive voltage. A print control method in which a thermal head having a length in a direction intersecting with the paper transport direction prints a plurality of print data for each line corresponding to the length for each print data in the paper transport direction. Because
A correction value selection step of selecting at least one correction value from a plurality of correction values stored in the correction value storage unit based on the paper characteristics of the paper input from the outside;
A density average value calculating step for calculating one print density average value based on a plurality of the print data including the one print data;
One drive for controlling the driving of the stepping motor based on at least one of the correction values selected in the correction value selection step and the one print density average value calculated in the density average value calculation step A drive signal calculating step for calculating a signal; a drive control step for controlling the driving of the stepping motor by the one drive signal calculated in the drive signal calculating step;
A printing control method comprising: a printing step in which the thermal head prints the one print data on the sheet conveyed by a roller rotated by the stepping motor whose driving is controlled by the one drive signal. The concentration average value calculating step includes:
Based on a plurality of the print data including other print data to be printed on the line adjacent to the one print data in the paper, further calculating another print density average value,
The printing control method includes:
A line-to-line density comparison step for correcting the one drive signal based on the one print density average value and the other print density average value;
The printing control method according to claim 6, wherein the driving control step controls the driving of the stepping motor based on the driving signal corrected in the inter-line density comparison step.   The print control method according to claim 6 or 7, wherein the drive control step controls the drive of the ink sheet conveyance motor in association with the one drive signal calculated in the drive signal calculation step.   The print control method according to claim 7, wherein the drive control step controls the drive of the ink sheet conveyance motor in association with the one drive signal corrected by the inter-line density comparison step. 10. The printing control method according to claim 6, wherein the driving signal for controlling the driving of the stepping motor is a driving current or a driving voltage. 11.

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