JPH0624944U - Thermal head controller - Google Patents

Abstract

(57) [Abstract] [Purpose] In a thermal head, when the energization time for each heating element is subdivided and controlled, an increase in the number of print data is suppressed and high-speed printing is possible. An energization time for a heating element required for printing one line is divided into a plurality of different energization time units based on a binary system, and energization control of each heating element is performed for each of the divided energization time units. I do. As a result, it is possible to suppress an increase in the number of print data and to perform printing at high speed when the energization time to the heating element is finely controlled. Further, since the energization control is performed in the order of a predetermined energization time unit, printing can be efficiently performed.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a thermal head control device for printing on recording paper by energizing a heating element.

[0002]

[Prior art]

 In general, this type of thermal head is equipped with a plurality of heating elements, and each of the heating elements is energized to generate heat, thereby performing printing on recording paper. FIG. 5 is a block diagram showing the configuration of such a thermal head. In the figure, 1 is a thermal head (hereinafter, head), the head 1 is a common electrode 11, a plurality of individual electrodes 12A, 12B, and heat generation. It is composed of a plurality of heating elements 13 such as resistors, an AND circuit group 14 including a plurality of AND circuits, a latch circuit 15, and a shift register 16. A VRC (Vector Raster Converter) 2 connected to the head 1 outputs to the head 1 a data signal DT for selecting a desired heating element from a plurality of heating elements and energizing it. Command data CM from the host device is input and converted into vector data, this vector data is further converted into raster data (dot data corresponding to each heating element), and serial data is sent to the shift register 16 in the head 1. Output as signal DT.

Then, the shift register 16 inputs this signal DT bit by bit (1 dot) in synchronization with a clock signal CLK from a control circuit (not shown), and when a predetermined number of bits are input, outputs it to the latch circuit 15. Then, the latch circuit 15 holds this data by the latch signal LTH from the control circuit. Each bit of the data held by the latch circuit 15 is output to one input terminal of each AND circuit constituting the AND circuit group 14, and at this time, the strobe signal STB from the control circuit is input to the other input terminal. Then, the voltage corresponding to each bit output is applied to each individual electrode 12B. As a result, a current flows from the power source E connected to the common electrode to the individual electrode 12B side through the individual electrodes 12A and the individual heating elements, and the desired heating element is energized. Heat-sensitive recording paper, heat-fusible ink, and the like (not shown) are arranged on the facing surfaces of these heating elements, and an image is formed on the recording paper by the heat generated by the selected and energized heating elements.

In such a head, in order to obtain an image with a constant density, heat generation time is controlled in dot units, that is, in heat generating element units. Generally, when controlling the heat generation time (energization time) of each heat generating element, it is controlled in consideration of factors such as the temperature of the heat generating element itself, residual heat from past printing, and variations in the resistance value of the heat generating resistor. ing. FIG. 6 is a timing chart showing a situation in which the heat generation time of such a heat generating element is controlled, and is an example in which the energization time of each heat generating element is controlled in three steps, that is, in three gradations. In FIG. 6, (a) shows the clock signal CLK, (b) shows the data signal DT, (c) shows the latch signal LTH, and (d) shows the strobe signal STB. The time width of the strobe signal STB that determines the energization time is It is set to be equal at each timing. When printing the data of one line, first, as the first data DT (1-1), the dot data corresponding to each heating element is held in the latch circuit 14 by the clock signal CLK and the latch signal LTH. , Strobe signal S TB is used to energize each heating element for printing. Next, the same control is performed during the second and third data printing, and when the third printing is performed, the printing of the same line is completed and the printing of the next line is performed. Here, for example, when it is desired to give a normal heating time to a certain heating element, dot data corresponding to each data DT (1-1) to data DT (1-3) in one line is set. At the same time, when it is desired to give a 2/3 times energization time, for example, the dot data corresponding to the first data DT (1-1) and the second data DT (1-2) is set, and the third data is set. The data DT (1-3) is non-print data. In this way, the print density can be changed in three steps.

[0005]

[Problems to be solved by the device]

 In this way, when controlling the energization time of each heating element in consideration of the characteristics of each heating element, if the energization time is made finer and control is performed with 16 gradations, for example, data is printed when printing one line. Printing must be repeated 16 times, and the amount of print data per line increases, so the capacity of the memory that stores these data becomes large and the time required for data transfer becomes long. It had the drawback that it could not be done at high speed. When printing is attempted at high speed with this configuration, the clock signal CLK and the like must be speeded up to transfer data at high speed, and as a result, it becomes necessary to use an element compatible with high speed. As a result, there was a drawback that it resulted in high costs. Therefore, an object of the present invention is to suppress the increase in the number of print data and perform printing at high speed when subdividing and controlling the energization time to each heating element.

[0006]

[Means for Solving the Problems]

 In order to solve such a problem, the present invention provides a means for dividing the energization time of a heating element required for printing one line on a recording paper into a plurality of different energization time units based on a binary method, and Means for controlling energization of the heating element is provided for each divided energization time unit. In addition, when controlling the energization of the heating elements, a means for controlling the energization time unit order is provided.

[0007]

[Action]

 The energization time of the heating element required for printing one line is divided into a plurality of different energization time units based on the binary system, and energization control to the heating element is performed for each divided energization time unit. . Further, the energization control is performed in a predetermined energization time unit order.

[0008]

【Example】

 Hereinafter, the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing an embodiment of a thermal head controller according to the present invention. In the figure, the same parts as those of the conventional device of FIG. 5 are designated by the same reference numerals and the description thereof will be omitted. In FIG. 1, 3 is a strobe signal generation circuit for determining the time width of a strobe signal indicating the energization time for each heating element 13 in the head 1 based on information from a control circuit described later, 4 is a selector, 5 Is a memory for storing dot data for energizing each of the heating elements 13, and 6 is a control circuit.

Here, when the VRC 2 receives the command data CM, the VRC 2 converts the command data CM into 1-line raster data, that is, dot data. This dot data is sent to the strobe signal generation circuit 3, and the strobe signal generation circuit 3 determines the time width of the strobe signal, that is, the energization time for each heating element unit in the head 1. This energization time is 2 when printing is performed in 16 steps, that is, 16 gradations are printed. ⁰ ~ 2³ Is represented by a 4-bit binary number corresponding to. Incidentally, in determining the energization time, the printing history of each heating element, the temperature of the head 1 and the printing conditions such as the resistance value of the heating element are taken into consideration, and these information are given from the control circuit 6.

The dot data represented by such a binary number and having a fixed energization time is temporarily set in the memory 5 according to an instruction from the control circuit 6. Then, when such dot data is set in the memory 5 up to the dot data DT _n corresponding to the heat generating element 13 _n , one strobe unit data (energization time t, 2t, 4t, which will be described later) is stored in the memory 5. 8t data) is formed. When a predetermined unit of strobe-unit dot data is created, these strobe-unit data are read from the memory 5 according to an instruction from the control circuit 6 and sent to the head 1 as serial data via the selector 4. The selector 4 switches the dot data from the memory 5 to the head 1 in strobe units. When the strobe-unit dot data is set in the head 1 in this way, the control circuit 6 sends the latch signal LTH to the head 1 to hold the dot data, and at the same time, the time based on the information from the strobe signal generating circuit 3 is sent. The width strobe signal ST B is output to energize the heating elements 13 corresponding to the dot data, and as a result, printing is performed on the recording paper. When the dot data in strobe units is printed in this way, the next data in strobe units is read from the memory 5 and printed in the same manner.

FIG. 2 is a diagram showing a state of dot data stored in the memory 5 and corresponding to each heating element, and is represented by a binary number as described above. According to the example of FIG. 2, the heating element 13 ₁ corresponding to the dot “1” is not printed because the energization time is “0”, and the heating element 13 ₂ corresponding to the dot “2” is energized. Since the time is "10", when the maximum energization time when printing one line with 16 gradations is "16", only the energization time "10" is assigned. Further, since the heating element 13 ₃ corresponding to the dot “3” has the energization time of “8”, only the energization time of “8” is assigned through the printing of one line. Then, the writing and reading of the dot data with respect to the memory 5 are performed in the above strobe unit, that is, every energization time t, 2t, 4t, 8t.

Next, FIG. 3 is a timing chart showing a printing operation by each heating element 13. In the figure, (a) shows a clock signal CLK, (b) shows a dot data signal DT, (c) shows a latch signal LTH, (d) shows a strobe signal STB, and (e) and (f) show. 3 is a timing chart in which a clock signal CLK and a dot data signal DT are enlarged, respectively. FIG. 3 shows that when 1-line printing is performed with 16 gradations, the printing time (energization time) is time t, the time 2t is twice the time t, and the time is four times t. In this example, the time is divided into four, namely, the time 4t, the time 8t having an energization time 8 times the time t, and the printing is performed at timings of time t 2, 2t, 4t, 8t. That is, when the setting of the dot data for each energization time t, 2t, 4t, 8t to the memory 5 is completed, the control circuit 6 outputs the latch signal LTH1 as shown in FIGS. 3 (c) and 3 (a). At the same time, the clock signal CLK is subsequently output. As a result, the data DT corresponding to the timing t stored in the memory 5 is read out dot by dot through the selector 4 and sent to the head 1 to be set. This set dot data is either on (“1”) or off (“0”) for each dot corresponding to each heating element, as shown in FIGS. The selected clock signal CLK is successively updated at the rising edge of CLK. When the dot data DT corresponding to the energization time t is set in the latch circuit 15 in the head 1 in this way, the control circuit 6 outputs the latch signal LTH2 to hold the data DT as shown in FIG. Together, subsequently, the strobe signal STB corresponding to the time t is raised as shown in FIG. As a result, the dot data DT is output from the AND circuit group 14 in the head 1 and the corresponding heating elements 13 are energized for the time t 1.

The output of the latch signal LTH2 reads the dot data 2DT corresponding to the next energization time 2t and is set in the head 1. Further, the latch signal LTH 3 and the strobe signal LTB are used to cause the heating elements to be supplied to each heating element. The power is supplied for 2t. Hereinafter, the energization operation by the set of dot data 4DT, 8DT corresponding to the energization time 4t, 8t is similarly performed.

As described above, the present invention is based on the binary method such that the following equations (1) and (2) are established, where T is the time width of the strobe signal STB required for printing one line. The unit strobe time width (energization time) t is determined to control the heat generation time. That is, T = t + 2t + 4t + 8t (for 16 gradations) ... (1) T = t + 2t + 4t + 8t + 16t (for 32 gradations) ... (2)

In the above embodiment, an example in which the energization timing of the head 1 is given in the order of time t, 2t, 4t, 8t has been described. However, since this method first prints for a short time, The heat generated by the thermal head may not be transmitted effectively. That is, for example, when printing 9 gradations based on the timing chart of FIG. 3, if the order of energizing time is time t, 2t, 4t, 8t, the first printing is performed at time t, and No printing is performed at 2t and 4t, and the last printing is performed at the last energization time 8t. In this case, the heat generated by the heating element due to printing during the first energization time t is dissipated during printing during the energization time 8t and is not effectively transmitted.

Therefore, as shown in FIG. 4A, the printing timing is set in the order of time 8t, 2t, t 2, 4t. That is, the longest energization time 8t is applied to perform the first printing, the third longest energization time 2t is applied to perform the second printing, and the third printing is applied to the shortest energization time t. The last printing is performed by giving the second longest energization time 4 t. Here, T represents the printing time required for printing one line. By arranging the print timing with short energization time in the middle and the print timing with long energization time first or last, the residual heat from the first printing is retained by the last printing timing. Effective printing can be performed. Note that FIG. 4B shows the printing timing by 5 bits and shows the sequence of each printing timing when printing with 32 gradations.

[0017]

[Effect of device]

 As described above, according to the present invention, the energization time for the heating element required for printing one line is divided into a plurality of different energization time units based on the binary system, and the divided energization time is divided. Since the energization of the heating element is controlled for each unit, an increase in the number of print data can be suppressed when the energization time given to the heating element is finely controlled. Therefore, highly accurate printing control can be performed with a small memory capacity. It is possible to print at high speed. Further, since the energization control is performed in the order of the predetermined energization time unit, the printing control can be efficiently performed.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a thermal head controller according to the present invention.

FIG. 2 is a diagram for explaining a control situation of energization time of a thermal head of the apparatus.

FIG. 3 is a timing chart showing a printing operation of the above apparatus.

FIG. 4 is a timing chart showing an operation of another embodiment of the above apparatus.

FIG. 5 is a block diagram of a conventional device.

FIG. 6 is a timing chart showing a printing operation of a conventional device.

[Explanation of symbols]

 1 Thermal Head 2 VRC 3 Strobe Signal Generation Circuit 4 Selector 5 Memory 6 Control Circuit 11 Common Electrode 12A, 12B Individual Electrode 13 Heating Resistor 15 Latch Circuit 16 Shift Register CM Command Data DT Data Signal STB Strobe Signal LTH Latch Signal CLK Clock Signal

Claims (2)

[Scope of utility model registration request] 1. A controller for a thermal head that prints on a recording paper by sending print data corresponding to a plurality of heating elements provided in the thermal head and energizing each of the plurality of heating elements. Means for dividing the energization time of the heating element required for printing one line on the recording paper into a plurality of energization time units based on the binary system, and a unit for dividing the energization time unit for each of the divided energization time units. A thermal head control device comprising: means for controlling energization. 2. The thermal head controller according to claim 1, further comprising means for controlling energization control for each of the plurality of divided energization time units in a predetermined order. Control device.