JPS62279964A - Thermal head controlling method - Google Patents

Abstract

PURPOSE:To make it possible to print with a fixed density even under variations in printing speed, by detecting a feed time for each dot line, and varying energy supplied to a thermal head based on the feed time being detected. CONSTITUTION:A counter 5 provided in connection with a head-driving circuit 3 is reset by a resetting signal supplied from the circuit 3, upon which the counter 5 restarts counting. The counter 5 counts time from the printing in the current dot line to the printing in the next dot line, namely, the feed time for one dot line. When performing the printing in the next dot line, count data is outputted from the counter 5 to a power source circuit 4, and the voltage of a voltage pulse supplied from the circuit 4 to a thermal head 1 through the head-driving circuit 3 is variably controlled according to the count data supplied from the counter 5.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention Technical Field The present invention relates to a thermal head control method in a line printer.

Conventional technology Conventionally, in a line printer using a thermal head, methods for controlling the thermal energy of the thermal head include, for example, a method of detecting the temperature of the thermal head and controlling the energy applied to the head based on that temperature, and a method of controlling the energy applied to the head based on the detected temperature. There is a method of controlling applied energy based on the history of dot lines and print information between adjacent dots on the left and right.

However, with such an energy control method, it is not possible to cope with local temperature changes in the thermal head caused by differences in feeding time for each dot line. That is, it is sufficient if the feeding time between each dot line is always constant, but if there is image data as well as character data, the feeding time for one dot line becomes longer and the heat storage state of the thermal head changes. Because it does. As a result, the printing state is such that the shading of the print is not constant depending on the transfer speed of the print data sent.

OBJECTS The present invention has been made in view of the above points, and an object of the present invention is to provide a thermal head control method capable of printing at a constant density even if the printing speed changes depending on the feeding time of each dot line.

Structure In order to achieve the above object, the present invention detects the feeding time for each dot line in a line printer using a thermal head, and varies the applied energy supplied to the thermal head based on the detected feeding time. It is characterized by this.

Hereinafter, a first embodiment of the present invention will be described based on FIG. This embodiment is applied to a device that controls a thermal head 1 using a pulse width modulation method. This thermal head 1 is for a line printer that prints on recording paper line by line.

The print data is then input to the history control circuit 2, which controls the pulse width of the applied energy applied to the thermal head 1 by referring to the history of the previous one dot line and the data between adjacent dots on the thermal head 1. and output to the head drive circuit 3. This head drive circuit 3 supplies a voltage pulse set in a power supply circuit 4 to the thermal head 1 to perform a printing operation. At this time, the counter 5 connected to the head drive circuit 3 is reset by receiving a reset signal from the head drive circuit 3, and from this point on, the counter 5 starts counting again, and from the current printing of one dot line to the next printing. The time until printing one dot line, that is, the feeding time of one dot line is counted and detected. Here, count data from the counter 5 is sent to the power supply circuit 3 when printing the next one-dot line, and voltage pulses are supplied from the power supply circuit 3 to the thermal head 1 via the head drive circuit 3. The voltage value is variably controlled in accordance with the count value data from this counter 5 (therefore, the feeding time data of one dot line).

As a result, for example, when the counter 5 detects that the time between printing a certain one-dot line and printing the next one-dot line is short, energy is supplied to the thermal head 1 at a lower voltage. and printed. On the other hand, when the counter 5 detects that it takes a long time to print the next one dot line after printing one dot line, the thermal head 1 is supplied with energy with a higher voltage. It will be printed. As a result, the thermal head 1 prints by being supplied with applied energy according to its heat storage state, so that good printing with constant density is achieved.

Next, a second embodiment of the present invention will be described with reference to FIG. In this embodiment, a head drive circuit 3 and a counter 5 are connected in a loop. As a result, the data from the history control circuit 2 (same as in the above embodiment) and the counter 5
Based on the counted value data (1 dot line feeding time data), the thermal head 1 is
By varying the number of pulses or the pulse width of the pulse voltage supplied to the device, the applied energy can be variably controlled. With this arrangement as well, it is possible to perform printing at a constant density, similar to the embodiment described above.

Effects As described above, in the present invention, the energy applied to the thermal head is varied in consideration of the feeding time of one dot line, so the applied energy is supplied according to the heat storage state of the thermal head, and the transfer time of print data etc. is reduced. Even if the density changes, it is possible to print at a constant density.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a first embodiment of the present invention, and FIG.
The figure is a block diagram showing a second embodiment of the present invention. 1... Thermal head applicant Rico Co., Ltd. - Atsushi Figures 1 to Z

Claims (1)

[Claims] 1. A method for controlling a thermal head in a line printer using a thermal head, characterized in that a feeding time for each dot line is detected, and energy applied to the thermal head is varied based on the feeding time.