JPS631557A - Thermal printer - Google Patents

Abstract

PURPOSE:To improve the printing quality, by comparing the current and past temperature levels of a thermal head and determining the width of pulse being applied onto the thermal head. CONSTITUTION:A thermistor 17 for detecting the temperature of a head is provided in a thermal head 6 arranged at a transfer section A. When a detection signal of current head temperature is inputted from the thermistor 17 to a CPU 13, the current head temperature is compared with a past head temperature being inputted predetermined time before and stored in a RAM 12 or a buffer RAM. If the comparison results, shows that the head temperature is lowering the CPU 13, determines the width of pulse being applied corresponding to the current head temperature. At the same time, a predetermined pulse width is subtracted from the pulse width corresponding to the head temperature so as to determine the width of pulse being applied actually onto the thermal head 6, then a signal is transmitted to a driver 15 so as to apply voltage onto the thermal head 6. If it is judged that the head temperature is increasing, the predetermined pulse width is added to the pulse width corresponding to the head temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thermal printer that can set a head temperature suitable for printing.

BACKGROUND OF THE INVENTION In conventional thermal printers, control of head temperature is very important. Currently, the head temperature is detected by replacing it with the resistance value of a thermistor, and the applied pulse width is adjusted based on the detection result to achieve an appropriate head temperature. While l is trying to dissolve,
By the way, according to the conventional means described above, there is a one-to-one correspondence between the head temperature detected by the thermistor (hereinafter referred to as detected temperature) and the applied pulse width, and if the detected temperature is the same, the same pulse is always applied. However, even if the detected temperature is the same, if the head temperature rises from a low temperature and conversely falls from a high temperature, the head voltage will vary for the same applied pulse width. Temperatures may vary. In actual printing, printing is often performed on multiple consecutive sheets, so the temperature of the platen roller, the temperature inside the printer, or the temperature of each motor increases or decreases, which may affect the head temperature. There is. Therefore, when the head temperature is decreasing, the actual head temperature may become higher than the optimum temperature, causing smearing in printing. On the other hand, if the head temperature is rising, the actual head temperature may become lower than the optimum temperature, resulting in blurring.

In view of these problems, it is an object of the present invention to provide a thermal printer configured to obtain good printing results by determining the temporal state of the head temperature and changing the pulse width applied to the head. With the goal.

Steps to Solve the Problems In order to achieve the above object, the present invention provides a temperature detection means for detecting the head and throat temperatures of a thermal head, and a method for detecting the current head temperature detected by the temperature detection means. The present invention is characterized by comprising a comparison means for comparing the head temperature with a past head temperature, and a means for determining the pulse width applied to the thermal head based on the comparison result.

According to the above, the voltage application pulse width to the thermal head is optimally set by determining whether the head temperature is rising or falling based on the current and past head temperatures, and the pulse width of the voltage applied to the thermal head is always set under the same conditions. Printing can be performed.

FIG. 1 is a schematic diagram of the area around the transfer section as an embodiment of the thermal printer of the present invention. The recording paper 1 is attached to a platen roller 2 constituting a transfer section A, and is configured to be sent in the direction indicated by a in the figure by a paper feeding drive section consisting of a pulse motor (not shown). In this embodiment, an ink film 3 is used as the ink sheet, stretched across an ink film supply roller 4 and an ink film take-up roller 5, and brought into close contact with the recording paper l at a part of the outer periphery of the platen roller 2. The ink film winding roller 5 is moved by an ink film feed motor (not shown), and winds up the ink film 3 in the direction b in the figure.

The transfer section A is provided with a thermal head 6 that transfers the heat-melting ink of the ink film 3 to the recording paper 1 by heating, and the thermal head 6 has a built-in thermistor (described later) that detects the head temperature. . A peeling roller 7 for peeling off the ink film 3 and the recording paper 1 is provided a predetermined distance ahead of the transfer portion A in the ink film feeding direction.

FIG. 2 is a block diagram of the control system of the printer, and FIG. 3 is a flowchart for determining the voltage application pulse width to be applied to the thermal head. In the figure, 11 is ROM, 12 is R
AM, 13 is a CPU, 14 is an I/O port, 15 is a driver for driving the thermal head 6, 16 is an A/D converter, and 17 is the above-mentioned thermistor.

From the thermistor 17 attached to the thermal head 6,
A detection signal that detects the head temperature is sent to the A/D through signal line l.
It is transmitted to the cpu 13 via the converter 16 and the I/O port 14.

Therefore, when a detection signal of the current head temperature H2 is input from the thermistor 17 to the CPU 13 (S2), it is input (S1) a certain period of time ago and is stored in the RAM 12 or buffer R.
It is compared with the past head temperature +1 stored in the AM (S3). As a result of this comparison, if it is determined that the head temperature is decreasing (Hl>82) (S4), the CPU
13 determines the applied pulse width corresponding to the current head temperature H2 (S5), and at the same time determines the applied pulse width of the head temperature H2 by the length of the specified shortened applied pulse width stored in advance. (S6) to determine the actual pulse width applied to the thermal head 6, and then
transmits a signal to and applies voltage to the thermal head 6 (
S7).

On the other hand, as a result of the comparison, the head temperature is rising (H, <82)
If it is determined (S8), the CPU 13 determines the applied pulse width corresponding to the current head temperature H2 (S9). , in addition to the applied pulse width of the head temperature H2 (SIO), the actual thermal head 6
The pulse width to be applied to the thermal head 6 is determined, a signal is transmitted to the driver 15, and a voltage is applied to the thermal head 6 (S7).

Also, as a result of the comparison, the head temperature is the same both now and in the past (l
II=H2) (S8), the CPU 13
determines the applied pulse width corresponding only to the current head temperature H2 (Sll). Then, a signal is transmitted to the driver 15 to apply voltage to the thermal head 6 (S7
).

FIG. 4 is a graph showing the relationship between the applied pulse width and the head/nod temperature. For example, the situation in which the applied pulse width is determined when the head temperature is t1 will be explained.

4. Predict the optimum applied pulse width for the head temperature when the head temperature is rising and when it is falling. If this is set, the width of the applied pulse corresponding to the detected head temperature tl can be determined as shown by the broken line.

Note that the printing operation by the thermal printer is well known and will therefore be omitted.

As described above, this printer compares and determines whether the current head temperature is increasing or decreasing with respect to the past head temperature and determines the optimal pulse width to apply based on this comparison result. The thermal melting temperature of No. 3 is set to the best condition, and the printing quality can be maintained at a high level.

Since the thermal printer of the present invention is configured as described above, it compares and determines whether the current head temperature is increasing or decreasing with respect to the past head temperature, and determines the optimum temperature based on this comparison result. Since the applied pulse width is determined, the thermal melting temperature of the ink film is set to the optimum state, so that the transfer can be performed better and the print quality can be maintained at a high level.

DETAILED DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram of the area around the transfer unit as an embodiment of the thermal printer of the present invention, FIG. 2 is a block diagram of the blink control system, and FIG. 3 is a diagram showing the voltage applied to the thermal head. A flowchart for determining the applied pulse width, and FIG. 4 is a graph showing the relationship between the applied pulse width and the head temperature.

1: Recording paper, 2: Platen roller, 3: Ink film, 6: Thermal head, 11.12,1
3: comparison means, applied pulse width determination means, 17: temperature detection means (thermistor), A: transfer section.

Patent applicant: Minolta Camera Co., Ltd. Figure 1 Figure 2 Figure 3 Figure 4 Hey...meal

Claims (1)

[Claims] (1) Temperature detection means for detecting the head temperature of the thermal head; comparison means for comparing the current head temperature detected by the temperature detection means with past head temperatures; A thermal printer comprising: means for determining the applied pulse width of;