JPH03290269A - Printing method by thermal head - Google Patents

Abstract

PURPOSE:To eliminate tailings or lack of heat, and unify printing density to improve printing or picture quality by a method wherein a transfer time interval for printing data sent from a vector raster converter to a thermal head is measured, and a printing time width is changed in response to the transfer time interval. CONSTITUTION:A function to measure the time interval every time to receive a data transfer completion information from a line buffer 2; read out a most suitable strobe width information from a memory 4 based on the time interval; and control a thermal head 3 by this information is added to a CPU 5. For this reason, strobe width data to correspond with time interval for the data transfer completion is previously stored in the memory 4. The decision of the strobe width may be originally calculated to obtain it by the CPU 5, using a table instead of the memory 4. Every time printing data is transferred from a vector raster converter VRC1, at the CPU 5, processes to measure the data transfer completion time interval, determine the strobe width by reading the strobe width data in response to the time interval from the memory 4, and give the data to the thermal head 3 are performed.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention sequentially supplies one line of data (referred to as line data) sequentially generated by a vector raster converter (hereinafter also abbreviated as VRC) to a thermal head. The thermal head is sequentially and selectively driven to print or draw (
(also simply referred to as printing).

[Conventional technology]

FIG. 3 shows a general example of a thermal head printing method.

In the same figure, ■ is shown in vector format, for example, CAD
VRC converts image data output from a device etc. into Rask format print data; 2 is a line buffer for storing this print data; 3 is a thermal head;
4 is a memory such as a ROM, and 5 is a control circuit (CPU).

That is, the data for printing or drawing is given from the host computer (for example, CAD), and the VRCI calculates the position on one main scanning line for each line from the given data, and transfers the data to the line buffer 2. to be memorized. For example, in black and white binary recording, the line buffer 2 corresponds to the position on the main scanning line where the black point is to be recorded.
Logic “1” is placed in the position, and “0” is placed in the other position.
" is written. Then, only the thermal head at the position corresponding to the memory element in which the logic "1" is written in the line buffer 2 is heated, and printing is performed one line at a time.

When one line of recording is finished, the paper is fed by a certain minute distance in the sub-scanning direction, and the next line of data is input to the line buffer 2, and the input data drives the thermal head 3. be done.

FIG. 4 shows the internal structure of the thermal head. In the figure, 11 is a heating resistor of the thermal head, 12 is a shift register, 13 is a launch circuit, 14 is a driver, 15 is a DC power supply, 16 is a common electrode, 17 is a power supply side wiring pattern, and 18 is a grounding side wiring pattern. It is. The shift register 12 receives the data signal from the line buffer 2 and the clock signal from the control circuit 5, and the launch circuit 13 receives a launch signal for controlling the timing of writing data from the shift register 12. A strobe signal for controlling the operating time of the driver 14 is input from the control circuit 5 and is also input to the driver 14 according to the logic of the corresponding latch circuit 13.
Input from

Shift register 12. Latch circuit 13 and driver 1
4, which of the plurality of lead conductors of the ground side wiring pattern 18 is selected to be grounded. For example, lead conductor 1 of the ground side wiring pattern 18 is selected.
If 8a is grounded, the current flows from 17a to 18a and from 17b to 18a, and the part 1 of the heating resistor 11
The portions 1a and 11b will generate heat. Note that by dividing the common electrode 16 into a plurality of parts, each line can also be divided into a plurality of blocks for recording.

Printing energy is controlled by controlling the time width of the strobe signal, but conventionally, the thermal head 3 of the image data output from the VRCI
Generally, the transfer time to the strobe is assumed to be constant, and the strobe time width is generally kept constant during printing.

[Problem to be solved by the invention]

By the way, as mentioned above, the VRC creates raster data for printing with the thermal head, but at this time, the internal processing time changes depending on the printing pattern, so the time interval of one line of data sent to the line buffer, That is, the printing speed changes. The relationship between printing speed and data transfer time is, for example, as shown in FIG. 5, the smaller the data transfer time interval, the faster the printing speed, and the larger the transfer time interval, the slower the printing speed (Tl
).

Therefore, if you print as is without changing the energy for printing (strobe time width), the print will be dark in areas where data is sent quickly due to heat accumulation, and the print quality will deteriorate in areas where it is not. It will end up being put away. In other words, as the transfer time interval of print data sent from the vector raster converter, that is, the printing speed, increases, the effect of heat accumulation becomes more likely to occur, and so-called tailing becomes more likely to occur.
Furthermore, if the applied power is reduced in order to suppress trailing, there will be a problem of insufficient heat during low-speed printing, making it impossible to print clearly.

Therefore, an object of the present invention is to eliminate trailing and insufficient heat, keep the print density constant, and improve the print or drawing quality.

[Means to solve the problem]

When one line of data sequentially generated by a vector raster converter is sequentially supplied to a thermal head, and this thermal head is selectively driven to print sequentially, the transfer time of the print data sent from the vector raster converter is The interval is measured, and the printing time width is changed according to this transfer time interval.

[Effect]

By measuring the transfer time interval of the print data sent from the vector raster converter, that is, the printing speed, and changing the printing time width according to this transfer time interval, the print density is kept constant and tailing and lack of heat are eliminated. Improve printing or drawing quality.

In addition, in this type of thermal head printing device, the data processing speed of the circuit of the thermal head section shown in Fig. 4 can be considered to be constant. In the present invention, it is sufficient to measure the transfer time of print data to this thermal head section.

〔Example〕

FIG. 1 is a flowchart for explaining the present invention in detail, and FIG. 2 is a characteristic diagram for explaining the relationship between printing speed and applied energy in the present invention. Note that the device configuration is the same as that in FIG. 3. However, each time the CPU 5 receives data transfer completion information from the line buffer 2, it measures the time interval, reads out optimal strobe width information from the memory 4 based on the time interval, and controls the thermal head 3 based on this information. Features are added. For this reason, strobe width data corresponding to the time interval at which data transfer ends is stored in the memory 4 in advance. Note that for determining this strobe width, a table may be used instead of the memory 4, and the CPU 5
You may also calculate it independently.

Therefore, as shown in FIG. 1, each time print data is transferred from the VRCI, the CPU 5 measures the data transfer end time interval (see (2)), reads the corresponding strobe width data from the memory 4, and determines the strobe width. (Refer to ■), and performs processing to apply this to the thermal head 3 (Refer to ■).

Note that this operation is repeated until printing is completed (
(Refer to ■) 6 The relationship between the data transfer end time interval, that is, the printing speed and the strobe width (applied energy) is, for example, the second
The data will be stored in the memory 4 of FIG. 3 as shown in the figure. That is, the applied energy (strobe width) is kept approximately constant until the printing speed is reached, and beyond that point, the applied energy, ie, the strobe width, is decreased in accordance with the printing speed. Although the figure shows a straight line that descends at a constant slope, in reality it can be lowered in stages or various other modifications can be made, and if it is changed in stages, more fine-grained control becomes possible.

〔Effect of the invention〕

According to this invention, even if the printing speed changes, there will be no trailing or insufficient heat, and the printing density will be kept almost constant, so there is an advantage that the printing quality will be improved.

In particular, more precise density control can be achieved by combining other constant density processing, such as history control that looks at the history of black and white data or ratio control that looks at the number of black and white data.

[Brief Description of the Drawings] Fig. 1 is a flowchart showing an embodiment of the present invention;
The figure is a characteristic diagram for explaining the relationship between printing speed and applied energy in this invention, Figure 3 is a block diagram showing a general printing method using a thermal head, and Figure 4 is an overview showing the internal configuration of the thermal head. FIG. 5 is an explanatory diagram for explaining the relationship between printing speed and data transfer speed. DESCRIPTION OF SYMBOLS 1... Vector raster converter (VRC), 2... Line buffer, 3... Thermal head, 4... Memory, 5... Host computer (CPU), 11.
...Resistance heating element, 12...Shift register, 13...
- Launch circuit, 14... Driver, 15... DC power supply, 16... Common electrode, 17... Power supply side wiring pattern, 18... Grounding side wiring pattern. 0! 7p2 figure

Claims (1)

[Claims] 1) When sequentially printing by driving a thermal head selectively using one line of data sequentially generated by a vector raster converter, the print data sent from the vector raster converter to the thermal head; A printing method using a thermal head characterized by measuring the data transfer time interval and changing the printing time width according to the data transfer time interval.