JPH0316750A - Thermal printer - Google Patents

Abstract

PURPOSE:To automatically correct the dispersion of a temperature sensor at the replacement of a head to obtain an optimum printing density by providing a detachable reference temp. sensor, a comparison circuit, a reference temp. selection switch, a nonvolatile error memory circuit, and a correction data operation circuit. CONSTITUTION:A comparison circuit 5 compares an output of an A/D converter 3 of a reference temp. sensor 1 with an output of an A/D converter 4 of a head temp. sensor 2. The result is stored in a nonvolatile error memory circuit 7 on an output 6a when a reference sensor selection switch 6 is set to a reference sensor available side. The reference temp. selection switch 6 is set to a reference sensor available side when the reference temp. sensor 1 is mounted at the replacement of a head and set to a reference sensor unavailable side when the writing to the nonvolatile error memory circuit 7 is completed. An output 7a of the nonvolatile error memory circuit 7 is inputted to a correction data operation circuit 8. The output of the A/D converter 4 is connected to the other input terminal of the correction data operation circuit 9. An output 8a thereof is inputted to a PCONT terminal of a correction circuit 9. Depending on this value, the pulse width of an output PCONT terminal of the correction circuit 9 is determined and added to a head driver 10 to drive a thermal head 11.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for driving a thermal head in a thermal printer, and particularly to a circuit for correcting drive energy due to changes in head temperature.

[Conventional technology]

Conventionally, a temperature sensor is provided inside the thermal head, and the driving energy of the thermal head is corrected in accordance with the temperature change of this temperature sensor, thereby optimizing the print density. The correction value in this case was fixed.

[Problem to be solved by the invention]

For this reason, when the thermal head is replaced, the correction is insufficient or excessive due to variations (errors) in the temperature sensor, which adversely affects print quality.

[Means to solve the problem]

The thermal printer of the present invention includes a detachable reference temperature sensor, a comparison circuit for comparing the reference temperature sensor and the head temperature sensor, a reference sensor selection switch, the reference sensor selection switch, and the comparison circuit. Therefore, it is useful to have a non-volatile error circuit that memorizes the error difference, and a correction data calculation circuit that determines a correction value based on the error storage circuit and the output of the head temperature sensor. .

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a schematic diagram of the apparatus of the present invention, and FIG. 2 is an explanatory diagram of the operation.

1, the reference temperature sensor 1 is attached to the control board (
(not shown) is mounted with a socket etc. and is removable.
Implement when replacing the head. The temperature characteristics of the reference sensor l are known in advance, and the correction data is set based on this. The output 1a of the reference temperature sensor 1 is an A/D
Input to converter 3, output 3 of A/D converter 3
a is input to the comparison circuit 5. The head temperature sensor 2 is mounted inside the thermal head 11, and its output 2a is connected to the A/D
input to converter 4, output 4 of A/D converter 4
a is connected to one input of the comparison circuit 5. The comparison circuit 5 compares the A/D converter output of the reference temperature sensor 1 with the A/D converter output of the head temperature sensor 2, and when the reference sensor selection switch 6 is switched to the reference sensor use side, the comparison circuit 5a is output and stored in the nonvolatile error storage circuit 7. The reference sensor selection switch 6 is
When replacing the head, when the reference temperature sensor 1 is mounted, it is set to the side where the reference sensor is used, and when writing to the non-volatile error storage circuit 7 is completed, it is set to the side where the reference sensor is not used. In this case, the reference temperature sensor l is not used, the contents of the nonvolatile error storage circuit 7 are used as the error, and the reference temperature sensor may be removed. Non-volatile error storage circuit 7
The output 7a is input to the correction data calculation circuit 8. λ/
The output of the D converter 4 is connected to the other input of the correction data calculation circuit 8, and the correction data is calculated.The output 8a is the output PCON? of the correction circuit 9 according to the value input to the correction circuit 90PCON terminal. The pulse width of the terminal is determined and applied to the head driver lO, during which time the thermal head 111tK moves.

How the correction operation is performed in the above configuration will be explained with reference to FIG.

When the head is replaced when the ambient temperature is 20°C, the output of the A/D converter 3 of the reference temperature sensor 1 is "3", and the output of the A/D converter 4 of the head temperature sensor 2 is 15 g. Output. These are compared in the comparison circuit 5, and the result ``''-2'' (3-5=-2) is stored in the nonvolatile error storage circuit 7. When printing starts in this state, the output @-2'' of the nonvolatile error storage circuit 7 and the output ' of the A/D converter 4 of the head temperature sensor 2 at 20°C.
"5" is added by the correction data calculation circuit 8, and the result is "3".
"(-2+5=3) is added to the Pcosy terminal of the correction circuit 9. As a result, the output PoUT of the correction circuit 9 becomes @
The pulse width of PW3' is output and this is the head driver lO.
The head l1 is driven during this period. As a result of printing, the temperature of the thermal pad 11 rises, for example, 5
Assuming that the temperature is 0°C, the output of the A/D converter 4 will be "q" and the correction data calculation circuit 8 will be ``6'' (-
2+8=6) is output. As a result, the correction circuit 9 outputs a pulse width PW6 of 50° C., which is the same as that of the reference temperature sensor, and an optimum correction pulse width can be obtained.

〔Effect of the invention〕

As described above, in the present invention, by providing a detachable reference temperature sensor, a comparison circuit, a reference sensor selection switch, a non-incurable error storage circuit, and a correction data calculation circuit,
Variations in the temperature sensor when replacing the head can be automatically corrected, and the reference temperature sensor is required only when replacing the head and can be removed at other times.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is an explanatory diagram of the operation in D of the embodiment of the present invention. 1...Removable reference temperature sensor, 2...
・Head temperature sensor, 3...A/D converter, 4...A/D converter, 5...Comparison circuit, 6...Reference sensor Selection switch, 7.
...Non-volatile Ml4 difference memory circuit, 8...Correction data calculation circuit, 9...Correction circuit 1 lO...Head driver L l -n+●Thermal head.

Claims (1)

[Claims] A thermal printer is provided with a head temperature sensor in a thermal head, and prints by changing the driving energy of the thermal head by a correction circuit according to a temperature change of the head temperature sensor. A comparison circuit that compares the reference temperature sensor and the head temperature sensor, a reference sensor selection switch that determines whether or not to use the reference temperature sensor, and outputs of the comparison circuit and the sensor selection switch to reduce the error. What is claimed is: 1. A thermal printer comprising: a non-volatile error storage circuit for storing the error storage circuit; and a correction data calculation circuit for determining a correction value based on the error storage circuit and the output of the head temperature sensor.