JP2011110729A - Thermal head control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermal head control device for controlling boring diameters by driving and controlling a thermal head based on multivalue data, by which miss or fluctuation of boring is suppressed. <P>SOLUTION: The thermal head control device controls boring such that the heating time of a heating element applying small boring smaller than large boring is longer than the heating time of a heating element applying the large boring to stancil plate base paper, and controls boring such that the temperature of the heating element applying the small boring is lower than the temperature of the heating element applying the large boring. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a thermal head control device that drives and controls a thermal head in which a large number of heating elements that perforate a stencil sheet are arranged.

  2. Description of the Related Art Conventionally, a thermal head device that makes a stencil sheet by making a large number of heating elements generate heat based on image data output from a scanner, a computer, or the like to make a plate has been used in a stencil printing system.

  As a stencil printing system as described above, for example, a stencil sheet punching system based on binary data has been proposed.

  However, when stencil printing is performed with perforation based on binary data, for example, when a solid image is printed, as shown in the upper left diagram of FIG. Since there are many overlapping parts, the finished printed matter is finished in a darker color than the designated color. In addition, there is a problem of solid filling in which isolated points are buried. Furthermore, when a photographic image is printed, as shown in the center left diagram of FIG. 19, there is a problem that the expression of thin lines and smooth lines becomes poor because dots are combined by dot gain. The lower part of FIG. 19 shows an example of punching when punching is performed based on binary data of a photographic image.

  In view of this, a technique has been proposed in which gradation representation is possible by controlling the perforation diameter for each pixel using multi-value data. If the perforation diameter is controlled using the multi-value data, the dot gain can be suppressed as shown in the upper right diagram and the middle right diagram in FIG. Tonality and smoothness of characters can be improved.

  For example, in Patent Document 1, as described above, as a method for controlling the perforation diameter of a stencil sheet, the pulse width (heat generation time) and applied energy of a control signal supplied to a heating element constituting a thermal head are set for each pixel. A control method has been proposed.

JP-A-8-90748

  However, in Patent Document 1, as shown in FIG. 20, when a small hole is punched, the applied energy is reduced or the heat generation time is shortened, so the contact time between the heating element and the stencil sheet is short. There is a problem that the variation in the perforation size is increased and the perforation failure rate is also increased.

  Further, when a large perforation is perforated, since the heat generation time is long, there is a problem that a variation in perforation size becomes large due to a so-called drag phenomenon. The drag phenomenon means that when punching is performed by a thermal head while moving the stencil sheet, the heat sensitive position in the stencil sheet is shifted due to the movement of the stencil sheet, and the punching position is shifted.

  In view of the above circumstances, an object of the present invention is to provide a thermal head control device that suppresses the occurrence and variation of perforation and has a linear relationship between the printing density.

  The thermal head control device of the present invention is a thermal head control device comprising a thermal head in which a large number of heating elements that perforate stencil paper are arranged, and a drive control unit that drives and controls the thermal head. The temperature of the heating element that controls the heat generating element that performs large perforation is controlled so that the heat generating time of the heating element that performs small perforation smaller than the large perforation is longer than the heat generation time of the heating element that performs large perforating on the stencil sheet. It is characterized by controlling so that the temperature of the heating element to which small perforations are applied becomes lower.

  In the thermal head control device of the present invention, the drive control unit can be controlled so that the temperature of the heating element for performing small perforations is lower than the melting point of the stencil sheet.

  Further, the drive control unit is controlled so that the heat generation energy of the heating element that performs small perforations is larger than the heat generation energy of the heat generation element that performs large perforations.

  In addition, the drive control unit outputs a pulse signal as a signal for controlling the driving of the heating element, and the duty ratio of the pulse signal supplied to the heating element that performs small perforation is set to the heating element that performs large perforation. The duty ratio of the supplied pulse signal can be made smaller.

  According to the thermal head control device of the present invention, while controlling so that the heat generation time of the heating element that performs small perforation smaller than the large perforation is longer than the heat generation time of the heating element that performs large perforation on the stencil paper, Since the temperature of the heating element that performs small perforations is controlled to be lower than the temperature of the heating element that performs large perforations, the contact time between the heating element and the stencil sheet is increased when drilling small perforations. As a result, it is possible to reduce the variation in the perforation size and reduce the perforation failure rate. Moreover, when drilling large perforations, since the heat generation time can be shortened, variations in perforation size due to the so-called drag phenomenon can be suppressed.

  Further, in the thermal head control device of the present invention, the duty ratio of the pulse signal supplied to the heating element that performs small perforation is set to be smaller than the duty ratio of the pulse signal that is supplied to the heating element that performs large perforation. In this case, it is possible to control the power applied to each heating element (heat generation temperature) with a simpler configuration.

Schematic configuration diagram of a stencil printing system using an embodiment of the thermal head control device of the present invention The figure which shows the structure of the plate-making part in the stencil printing system shown in FIG. The figure which shows an example of the control signal according to the plate-making data of 8 gradations The figure which shows the change of the heat_generation | fever temperature at the time of carrying out drive control (small perforation) of the heat generating body with the control signal of one Embodiment of this invention, and the heat_generation | fever temperature change when heat-generation time is controlled like a prior art. The figure which shows the piercing | piercing state and printing result at the time of carrying out drive control (small piercing | piercing) of a heat generating body with the control signal of one Embodiment of this invention, and the piercing | punching state and printing result when heat_generation | fever time is controlled like a prior art. The figure which shows the state of the stencil paper at the time of carrying out drive control (small punching) of the heat generating body with the control signal of one Embodiment of this invention, and the state of the stencil paper at the time of controlling heat generation like a prior art The figure which shows the change of the heat_generation | fever temperature at the time of carrying out drive control (large perforation) of a heat generating body with the control signal of one Embodiment of this invention, and the heat_generation | fever temperature when the heat_generation | fever time is controlled like a prior art. The figure which shows the piercing | punching state and printing result at the time of carrying out drive control (large piercing | punching) of the heat generating body with the control signal of one Embodiment of this invention, and the piercing | punching state and printing result when heat_generation | fever time is controlled like a prior art. The figure which shows the state of the stencil paper at the time of carrying out drive control (large punching) of the heat generating body with the control signal of one Embodiment of this invention, and the state of the stencil paper at the time of controlling heat generation like a prior art The graph which shows the non-occurrence rate and SN when the heating element is driven and controlled by the control signal of one embodiment of the present invention, and the non-occurrence rate and SN when the heat generation time is controlled as in the prior art. Table showing details of conditions for obtaining the graph shown in FIG. Perforation state in stencil paper when perforated heating element is driven and controlled by control signal of one embodiment of the present invention (perforation size 1 to 3) Perforated state in stencil sheet when perforated heating element is driven and controlled by control signal of one embodiment of the present invention (perforation size 4-6) Perforation state in stencil sheet when the heating element is driven and controlled by the control signal of one embodiment of the present invention (perforation size 7) Perforation state in stencil paper when the heat generation time is controlled as in the prior art (perforation size 1 to 3) Perforation state in stencil paper when heat generation time is controlled as in the prior art (perforation size 4-6) Perforation state in stencil paper when heat generation time is controlled as in the prior art (perforation size 7) The figure which shows other embodiment of the control signal of the thermal head control apparatus of this invention. Diagram for explaining the prior art The figure for demonstrating the control method of the drilling diameter of a prior art

  Hereinafter, a stencil printing system using an embodiment of a thermal head control device of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic configuration diagram of the stencil printing system.

  As shown in FIG. 1, the stencil printing system includes a computer 1 that outputs image data for single-sided printing or double-sided printing, and stencil printing that performs stencil printing and stencil printing based on the image data output from the computer 1. The apparatus 2 is provided. This stencil printing system has a feature in the drive control method of the thermal head in the stencil printing apparatus 2. First, the overall configuration of the stencil printing apparatus 2 will be described.

  As shown in FIG. 1, the stencil printing apparatus 2 is based on an image reading unit 10 that reads an image of a document and outputs image data, image data output from the computer 1, or image data read by the image reading unit 10. The first and second printing units 40 and 50 for performing printing on the printing paper P1 using the stencil sheet M that has been subjected to the plate making process on the stencil sheet M, and the first printing. The paper feeding unit 20 that feeds the printing paper P1 to the unit 40, the printing paper P2 that is printed on one side in the first printing unit 40 is temporarily stocked, and then fed to the second printing unit 50 at a predetermined timing. The intermediate stock unit 46, a paper discharge unit 70 for discharging the printing paper P3 printed on both sides by the second printing unit 50, and an operation panel 80 for receiving a predetermined setting input by the operator are provided.

  The image reading unit 10 includes a line image sensor that photoelectrically reads image information of an original, scans the original with the line image sensor, and outputs image data.

  The plate making unit 30 performs a plate making process on the stencil sheet M fed from the stencil sheet roll using a thermal head 31. FIG. 2 shows a more specific configuration of the plate making unit 30.

  As shown in FIG. 2, the plate making unit 30 includes the above-described thermal head 31, the conveyance device 3 that conveys the stencil sheet M, the image processing unit 35 that generates plate making data, and the plate making generated in the image processing unit 35. And a thermal head drive control unit 36 that drives and controls the thermal head 31 based on the data. The plate making unit 30 reciprocates between the first printing 40 and the second printing unit 50 as shown by arrows in FIG. 1 and is wound around the first printing drum 41. The stencil sheet M and the stencil sheet M wound around the second printing drum 51 are subjected to a plate making process.

  The thermal head 31 has a large number of heating elements that thermally perforate the stencil sheet M arranged in the main scanning direction (Y direction in the figure).

  The image processing unit 35 receives image data output from the image reading unit 10 or the computer 1, and generates plate making data of 2 gradations or 8 gradations (including 0) based on the received image data. This is output to the thermal head drive control unit 36. Note that the stencil printing system of this embodiment can perform both stencil printing with 2 gradations and stencil printing with 8 gradations, and one of these can be performed according to a selection instruction by an operator. Stencil printing is selected and executed.

  The thermal head drive control unit 36 outputs a drive control signal to each heating element of the thermal head 31 based on the input platemaking data of 2 gradations or 8 gradations. This will be described in detail later.

  The conveying device 3 moves the stencil sheet M in the sub-scanning direction (X direction in the figure) for each scanning line. The platen roller 32 that conveys the stencil sheet M and a drive that drives the platen roller 32 to rotate. A motor 34 and a gear 33 that transmits the rotational drive of the drive motor 34 to the platen roller 32 are provided. Specifically, the drive motor 34 is a stepping motor, and the gear 33 has a gear ratio set so that the stencil sheet M is moved in the sub-scanning direction by one scanning line every step.

  The first printing unit 40 is a first printing unit that presses the printing paper P1 against the first printing drum 41 with a predetermined press pressure with a cylindrical printing drum 41 that is permeable to ink, such as a porous metal plate or a mesh structure. A press roller 42 and a first stripping claw 43 that strips the single-side printed paper P2 from the first printing drum 41 are provided.

  Similarly to the first printing unit 40, the second printing unit 50 is configured to press the cylindrical second printing drum 51 and the printing paper P2 against the second printing drum 51 with a predetermined press pressure. A press roller 52 and a second peeling claw 53 for peeling the double-side printed paper P3 from the second printing drum 51 are provided.

  The paper supply unit 20 includes a paper supply base 21 on which the print paper P1 is placed, and a primary paper supply roller 22 that takes out the print paper P1 one by one from the paper supply base 21 and sends it to the secondary paper supply roller 23. The leading end of the printing paper P1 that is disposed downstream of the primary paper feeding roller 22 in the carrying direction is temporarily stopped, and the printing paper P1 is transferred to the first printing drum at a predetermined timing. A secondary paper feed roller 23 is provided between 41 and the first press roller 42.

  The paper discharge unit 70 is a paper discharge feeding belt unit 72 that conveys the double-sided printed printing paper P3 to the paper discharge table 71, and a paper discharge on which the double-sided printed printing paper P3 conveyed by the paper discharge feeding belt unit 72 is stacked. A stand 71 is provided.

  Further, a curved conveyance unit 44 is installed between the first printing unit 40 and the intermediate stock unit 46. As shown in FIG. 1, the curved conveyance unit 44 includes a guide plate having a curved surface along the conveyance path. On the curved surface of the guide plate, a conveyor belt provided with a suction port for sucking the printing paper P1 sent out from the first printing unit 40 is installed. A pulley 45 that circulates and moves the transport belt is provided. The curved conveyance unit 44 sucks the single-side printed paper P2 by the suction port of the conveyance belt, and conveys the single-side printed paper P2 by the conveyance belt along the curved surface of the guide plate by rotating the pulley 45. Is.

  Further, between the intermediate stock unit 46 and the second printing unit 50, a pickup roller 47 that picks up the single-side printed printing paper P <b> 2 carried out from the intermediate stock unit 46, and single-sided printing picked up by the pickup roller 47. There is provided a timing roller 48 that sequentially feeds the finished printing paper P2 between the second printing drum 51 and the second press roller 52 at a predetermined timing.

  The operation panel 80 accepts instruction inputs such as plate making and printing start instructions, and accepts input settings for predetermined printing conditions. An input of a selection instruction for performing stencil printing with two gradations or stencil printing with eight gradations is received.

  Next, the operation of the stencil printing system will be described.

  First, on the operation panel 80, the operator selects whether to perform double-sided printing or single-sided printing, and selects whether to perform 2-tone printing or 8-tone printing. Here, the operation when double-sided printing and 8-tone printing are selected will be described first.

  Then, the image data read by the image reading unit 10 or the image data for double-sided printing edited by the computer 1 is input to the image processing unit 35, and the image processing unit 35 outputs 8 data based on the input image data. Gray-scale plate making data is generated and output to the thermal head drive controller 36.

  On the other hand, the stencil sheet M is transported by the platen roller 32 of the transport device 3 and is disposed under the heating element of the thermal head 31. Then, the stencil sheet M is transported by the transport device 3, and each heating element of the thermal head 31 is driven by the thermal head drive control unit 36 to perform perforation processing for each scanning line.

  Here, the drive control method of the thermal head 31 by the thermal head drive control part 36 of this embodiment is demonstrated in detail.

  First, as described above, plate making data of 8 gradations is input to the thermal head drive control unit 36, and the thermal head drive control unit 36 supplies each heating element according to the plate making data of 8 gradations. The control signal to be switched is switched. FIG. 3 shows control signals corresponding to the 8-gradation plate making data.

  Specifically, in FIG. 3, perforation sizes 1 to 7 corresponding to plate making data of 8 gradations including 0 data are indicated by black circles, and are used to perforate the perforation sizes 1 to 7. Each control signal is shown to the right of the drilling size. In FIG. 3, 0 data is not shown. The control signal shown in FIG. 3 is used for one heating element to punch one hole. When the control signal is off, the heating element is turned on to generate heat, and the control signal is turned on. Sometimes the heating element is turned off and does not generate heat.

  As shown in FIG. 3, the control signal is set so that the heat generation time becomes longer as the perforation size is smaller, and the duty ratio (a / b) is smaller as the perforation size is smaller. . Here, in the present embodiment, the heat generation time is a heat generation time required for the heat generator to perforate one hole, and includes a time during which the heat generator is off as shown in FIG. Further, the duty ratio refers to the ratio of the off time a to the time b of one cycle of on / off of the control signal. The reason why the duty ratio (a / b) is set to be smaller as the perforation size is smaller is to reduce the heat generation temperature of the heating element as the perforation size is smaller. For the control signals corresponding to the perforation sizes 1 and 2, it is desirable to set the duty ratio so that the heat generation temperature of the heating element is lower than the melting point of the stencil sheet M.

  Here, the operation when the drilling size is controlled by driving and controlling the heating element of the thermal head 31 by the control signal described above, and the operation when the drilling size is controlled by controlling the heat generation time as in the prior art will be described below. Explained.

  First, for example, an operation in the case of drilling with a small drilling size such as the drilling size 1 shown in FIG. 3 will be described. FIG. 4 shows a change in the heat generation temperature when the heating element is driven and controlled by the control signal of this embodiment as the condition 1, and a change in the heat generation temperature when the heat generation time is controlled as in the conventional case as the condition 2. Yes.

  As shown in FIG. 4, in the case of condition 1, the temperature of the heating element gradually increases with time, but the highest temperature is lower than in the case of condition 2 and higher than the glass transition temperature. Heat generation time and duty ratio are set. On the other hand, in the case of Condition 2, the heat generation time is set shorter than that in Condition 1, and the temperature of the heating element gradually increases with time, but the highest temperature becomes the melting point of the stencil sheet M. Set to

  And, the perforation process in the stencil sheet when the temperature of the heating element changes under the condition 1 and the printing result by the perforation, and the perforation process and the printing result by the perforation in the stencil sheet when the temperature of the heating element changes according to the condition 2 As shown in FIG.

  The upper left diagram of FIG. 5 shows the perforation state at time I when the temperature of the heating element reaches the glass transition point in condition 1 and the perforation state at time II when the temperature of the heating element becomes the highest. . 5 is the moving direction of the stencil sheet M. On the other hand, the upper right diagram in FIG. 5 shows the perforation state at time I ′ when the temperature of the heating element reaches the glass transition point in condition 2 and the perforation state at time II ′ when the temperature of the heating element becomes the highest. Is shown.

  4 and 5 are analyzed, in the case of condition 2, since the perforation size is controlled by the heat generation time, it is necessary to raise the temperature of the heating element to the melting point of the stencil paper in a short heat generation time. Therefore, as a result, the perforation size becomes larger than the condition 1. Specifically, for example, if the printing interval is 600 dpi (42.3 μm), the printing cycle is 20 ms, and the heat generation time is 1 ms, a drag of about 2.1 μm is generated, and the perforation size is reduced by this drag. It gets bigger. Note that dragging means that the heat sensitive position in the stencil sheet is shifted due to the movement of the stencil sheet, and the punching position is shifted.

  Further, since the temperature difference between time I ′ and time II ′ is large, that is, the temperature range of whether the perforation opens or does not open is controlled in a short time, the occurrence of non-occurrence due to variations in the temperature of the heating element. Or, the variation in perforation size becomes large. Even if the highest temperature is lowered, non-occurrence increases, and even if the highest temperature is raised, the variation in perforation size becomes large.

  On the other hand, according to the condition 1, since the perforation size is controlled at a lower temperature than the case of the condition 2 and with a long heat generation time, the perforation size can be reduced. For example, when the printing interval is set to 600 dpi (42.3 μm), the printing cycle is set to 20 ms, and the heat generation time is set to 3 ms, the drag of about 6.3 μm, which is larger than that in the condition 2, is performed. Although it occurs, since the perforation size can be reduced as described above, it is not affected by dragging. Furthermore, since the temperature difference in time from time I to time II is small, the variation in perforation size can be reduced. Further, since the heat generation time is long, the possibility of opening holes that do not open in a short time can be increased, and the non-occurrence rate can be reduced.

  The left figure of FIG. 6 shows the state of the stencil sheet when perforated according to condition 1, and the right figure of FIG. 6 shows the state of the stencil sheet when perforated according to condition 2. is there. As shown by the circles in FIG. 6, it can be seen that condition 1 has a lower misfire rate than condition 2. The heating time under condition 1 is 3.4 ms, the applied voltage to the heating element is 10.4 V, the heating time under condition 2 is 0.94 ms, and the applied voltage to the heating element is 12.25 V.

  Next, for example, a description will be given of the operation in the case of drilling a large drilling size such as the drilling size 7 shown in FIG. FIG. 7 shows a change in the heat generation temperature when the heating element is driven and controlled by the control signal of the present embodiment as the condition 1, and a change in the heat generation temperature when the heat generation time is controlled as in the conventional case as the condition 2. Yes.

  As shown in FIG. 7, in the case of condition 1, the temperature of the heating element gradually increases with time, and the highest temperature is set to be higher than the melting point of the stencil sheet M, but the heating time is It is set to be shorter than before.

  On the other hand, in the case of condition 2, the temperature of the heating element gradually increases with time as in condition 1, and the highest temperature is set to be higher than the melting point of the stencil sheet M. The time is set to be longer than the condition 1.

  And, the perforation process in the stencil sheet when the temperature of the heating element changes under the condition 1 and the printing result by the perforation, and the perforation process and the printing result by the perforation in the stencil sheet when the temperature of the heating element changes according to the condition 2 As shown in FIG.

  The upper left figure of FIG. 8 shows the perforation state at time I when the temperature of the heating element reaches the glass transition point under condition 1, and the perforation state and heat generation at time II when the temperature of the heating element reaches the melting point of the stencil paper. The perforation state at time III when the body temperature is highest is shown. 8 is the moving direction of the stencil sheet M.

  On the other hand, the upper right diagram in FIG. 8 shows the perforated state at time I ′ when the temperature of the heating element reaches the glass transition point in condition 2 and the time II ′ when the temperature of the heating element reaches the melting point of the stencil paper. The perforated state and the perforated state at time III ′ when the temperature of the heating element becomes the highest are shown.

  Here, when FIGS. 7 and 8 are analyzed, in the case of Condition 2, since the perforation size is controlled by the heat generation time, the perforation is performed with a long heat generation time, and the influence of the drag described above is large. As a result, the variation in perforation size becomes large. Specifically, for example, if the printing interval is 600 dpi (42.3 μm), the printing cycle is 20 ms, and the heat generation time is 3 ms, a drag of about 6.3 μm is generated, and the perforation size is reduced by this drag. It gets bigger.

  On the other hand, according to the condition 1, since the heat generation time is shorter than that in the condition 2, the influence of drag can be reduced. For example, if the printing interval is 600 dpi (42.3 μm), the printing cycle is 20 ms, and the heat generation time is 1 ms, as in the condition 2 described above, the drag is approximately 2.1 μm. Therefore, it is possible to reduce the variation in perforation size.

  The left figure of FIG. 9 shows the state of the stencil sheet when perforated according to condition 1, and the right figure of FIG. 9 shows the state of the stencil sheet when perforated according to condition 2. is there. As indicated by the circles in FIG. 9, in Condition 1, the drilling is performed with an appropriate drilling size without any variation. However, in Condition 2, it can be seen that the variation in the drilling size is increased by dragging. The heating time under condition 1 is 1.12 ms, the applied voltage to the heating element is 15.45V, the heating time under condition 2 is 3 ms, and the applied voltage to the heating element is 12.25V.

  In addition, FIG. 10 shows the non-occurrence rate and SN when drilling holes 1 to 7 according to Condition 1 and the non-occurrence rate and S.N. when drilling holes 1 to 7 according to Condition 2. N. S.N. is an index indicating the variation in the perforation size, and the larger the S.N., the smaller the variation in the perforation size.

  As shown in FIG. 10, in the case of the conventional condition 2, it can be seen that the non-occurrence rate is larger in the case of small drilling than in the case of the condition 1. Further, it can be seen that the condition 1 has a larger SN in each drilling size than the condition 2, and the variation in the drilling size is smaller.

  Details of Condition 1 when acquiring the graph shown in FIG. 10 are shown in FIG. FIG. 11 shows the heat generation time, the duty ratio, and the applied energy (heat generation energy) when each perforation size is applied. Applied energy (heat generation energy) [mJ] is applied power [W / dot] × heat generation time [ms] (not including off time), and applied power is 0.55 W / dot (voltage 15.45V, heating element) Resistance value of 4371Ω). For condition 2, the applied power was 0.0687 W / dot, and the heat generation time was 0.18 ms to 0.38 ms.

  Further, perforation states in the stencil sheet when perforation sizes 1 to 7 are perforated according to the condition 1 are shown in FIGS. 12 to 14, and perforation states when the perforation sizes 1 to 7 are perforated according to the condition 2 Are shown in FIGS. In addition, the right figure of FIGS. 12-14 is a partially expanded view of the left figure.

  As shown in FIGS. 12 to 17, it can be seen that condition 1 has smaller non-occurrence rate and variation in the drilling size than condition 2, and small holes can be drilled with a stable hole size.

  In the description of the above embodiment, the heat generation temperature at each perforation size is controlled by controlling the duty ratio of the control signal. However, the present invention is not limited to this, and the power applied to each heat generator is controlled to generate heat. The temperature may be controlled. FIG. 18 shows the applied power, heat generation time, and control signal for each perforation size in that case. As shown in FIG. 18, in this case as well, the heat generation time (off time of the control signal) is set longer as the perforation size is smaller, and the applied power is smaller as the perforation size is smaller. Set to In the case shown in FIG. 18 as well, the applied energy is set to be larger as the perforation size is smaller.

  Then, based on the plate-making data for the front side and the plate-making data for the back side, the thermal head 31 is driven and controlled by the thermal head drive control unit 36 as described above, and the plate-making process is performed. The front side plate is wound around the first printing drum 41, and the back side plate is wound around the second printing drum 51 to execute the printing operation.

  Specifically, ink is supplied to the inside of the first and second printing drums 41 and 51 by an ink supply pump (not shown), and the first and second printing drums 41 and 51 are rotationally driven. Then, the printing paper P1 is fed out from the paper feed tray 21 by the primary paper feed roller 22 at a predetermined timing in synchronization with the rotation of the first and second print drums 41 and 51, and once the secondary paper feed roller 23 is reached. 1 is formed by the secondary paper feed roller 23 from the left to the right in FIG. 1 at a predetermined timing, and is supplied between the first printing drum 41 and the first press roller 42. The Then, the printing paper P1 is pressed against the printing paper P1 by the first press roller 42 against the stencil stencil sheet M wound around the outer peripheral surface of the first printing drum 41. Is done.

  Then, when the first printing drum 41 is rotated by a predetermined angle and the single-sided stencil printing on the printing paper P1 is completed, the single-sided printing paper P2 is peeled off from the first printing drum 41 by the peeling claw 43. The single-sided printed printing paper P <b> 2 that has been removed and peeled off is conveyed to the intermediate stock unit 46 by the curved conveyance unit 44.

  The single-side printed paper P2 is once stocked in the intermediate stock section 46, and then discharged from the intermediate stock section 46 with the printing surface facing downward (the unprinted surface is the upper side), and is picked up by a pickup roller 47. And is once abutted against the timing roller 48 to form a slack and then supplied between the second printing drum 51 and the second press roller 52 by the timing roller 48 at a predetermined timing.

  Then, the non-printed surface of the single-sided printed paper P2 is pressed against the stencil stencil sheet M wound around the outer peripheral surface of the second printing drum 51 by the second press roller 52, so that the single-sided printing is completed. Stencil printing is performed on the unprinted surface of the printing paper P2.

  When the second printing drum 51 rotates by a predetermined angle and stencil printing on the unprinted surface of the single-sided printed paper P2 is completed, the double-sided printed paper P3 is removed by the second nail 53 by the peeling claw 53. The double-sided printed printing paper P3 that has been peeled off from the printing drum 51 is transported to the paper discharge tray 71 by the paper discharge feed belt 72 and stacked on the paper discharge tray 71.

  Then, the printing paper P1 is again fed out from the paper feed tray 21, and double-sided stencil printing is performed on the printing paper P1 in the same manner as described above.

  The operation when performing double-sided printing and 8-tone printing has been described above. Next, the operation when performing double-sided printing and 2-tone printing will be described.

  When performing double-sided printing and two-tone printing, the operator selects double-sided printing and two-tone printing on the operation panel 80.

  Then, the image data read by the image reading unit 10 or the image data for double-sided printing edited by the computer 1 is input to the image processing unit 35. Based on the input image data, the image processing unit 35 outputs 2 Gray-scale plate making data is generated and output to the thermal head drive controller 36.

  On the other hand, the stencil sheet M is transported by the transport device 3, and each heating element of the thermal head 31 is driven by the thermal head drive control unit 36 to perform perforation processing for each scanning line.

  Two-tone plate making data is input to the thermal head drive control unit 36, and the thermal head drive control unit 36 switches control signals supplied to the respective heating elements in accordance with the two-tone plate making data.

  Here, the control signals corresponding to the two gradation plate making data are only the on data corresponding to the 0 data and the off data corresponding to the 1 data. A control signal corresponding to the drilling size 7 in the case is used.

  Then, perforation processing is performed for each scanning line based on the control signal. In the case of two-tone printing, a printing cycle (time from the start of heat generation of a predetermined scan line to the start of heat generation of the next scan line). Is set to be shorter than the printing cycle of 8-tone printing. For example, if the printing cycle of 8 gradation printing is 20 ms, the printing cycle of 2 gradations is set to 2 ms.

  Then, as in the case of 8-tone printing, a front plate and a back plate are formed and wound around the first printing drum 41 and the second printing drum 51, respectively. Stencil printing is started. The effect of stencil printing on both sides is the same as that in the case of the above-described eight gradation printing.

  As described above, the double-sided printing of 8 gradations and 2 gradations has been described. The single-sided printing of 8 gradations and 2 gradations is performed by selecting single-sided printing by the operator on the operation panel 80. The plate making process is the same as in the case of duplex printing except that only one side is performed. Single-sided printing is performed using the first printing drum 41 or the second printing drum 51.

  Further, in the stencil printing system of the above embodiment, the plate making process in the double-sided printing and the plate making process in the single-sided printing are performed in the same manner. However, the present invention is not limited to this. The perforated area may be smaller than the case. That is, the heat generation time for forming perforations in double-sided printing is longer than the heat generation time for forming perforations in single-sided printing, and the applied power for forming perforations in double-sided printing is more You may make it make it smaller than the applied power for forming perforation in printing. This is due to the occurrence of ink back-through in double-sided printing.

  Further, on the operation panel 80, the normal ink mode and the ink saving mode may be selectable. When the ink saving mode is selected on the operation panel 80, the punching area for the same plate making data may be smaller than that in the normal ink mode.

  Further, a temperature sensor or the like that detects the environmental temperature may be further provided, and the heat generation time may be controlled based on the environmental temperature detected by the temperature sensor. Specifically, the heat generation time may be shortened as the environmental temperature is higher.

  Further, the printing rate may be calculated based on the image data received by the image processing unit 35 or the plate making data generated based on the image data, and the heat generation time may be controlled based on the printing rate. Specifically, the heat generation time may be shortened when the printing rate is high.

  Further, based on the image data received by the image processing unit 35 or the plate making data generated based on the image data, thermal history control is further applied to the control signal of each heating element of the thermal head 31. Also good.

  Further, the remaining amount of the stencil sheet of the stencil sheet roll may be acquired, and the heat generation time may be controlled based on the remaining amount. Specifically, the heat generation time may be lengthened as the remaining amount of the stencil sheet of the stencil sheet roll decreases.

  Alternatively, the stencil sheet type of the stencil sheet roll may be detected, and the heat generation time may be controlled based on the stencil sheet type. As for the type information of the stencil sheet roll, for example, the type information input on the operation panel 80 or the computer 1 may be received, or stored in a storage unit such as a tag provided on the stencil sheet roll. The type information may be read out.

DESCRIPTION OF SYMBOLS 1 Computer 2 Stencil printing apparatus 30 Plate making part 31 Thermal head 32 Platen roller 35 Image processing part 36 Thermal head drive control part 41 1st printing drum 51 2nd printing drum 80 Operation panel

Claims (4)

In a thermal head control device comprising a thermal head in which a large number of heating elements for perforating stencil paper are arranged, and a drive control unit for driving and controlling the thermal head,
The drive control unit controls the heat generation time of the heating element for performing small perforations smaller than the large perforations to be longer than the heat generation time of the heating element for performing large perforations on the stencil sheet. With
A thermal head control device, characterized in that control is performed so that the temperature of the heating element for performing small perforations is lower than the temperature of the heating element for performing large drilling.   2. The thermal head control device according to claim 1, wherein the drive control unit controls the temperature of the heating element for performing the small perforations to be lower than the melting point of the stencil sheet.   3. The drive control unit controls the heating energy of the heating element that performs the small drilling to be larger than the heating energy of the heating element that performs the large drilling. The thermal head control apparatus as described. The drive control unit outputs a pulse signal as a signal for driving and controlling the heating element, and
2. The duty ratio of a pulse signal supplied to the heating element that performs the small perforations is made smaller than a duty ratio of the pulse signal that is supplied to the heating element that performs the large perforations. 4. The thermal head control device according to any one of 3 to 4.