Thermal printer

Abstract

To provide a thermal printer that is configured so that a high-temperature part thereof can be estimated to prevent the part from overheating, during continuous printing.SOLUTION: A thermal printer, which is configured to control printing speed and control start of printing, by comparing a detected temperature by a thermistor TH provided in a thermal head 100 with a threshold temperature, is provided with: a control part that divides all heating elements in the thermal head 100 into a plurality of groups G1-GX and controls printing by controlling energization for each group; a counting part that counts the number of cumulative energization-dots of each group up to each printing line; and a corrected-temperature calculating part that identifies the group GI whose cumulative energization dots are most, and calculates a corrected temperature corrected on the basis of a distance between the group GI and the thermistor TH.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a thermal printer including a thermal head having heating elements divided into a plurality of groups. [Background technology]

[0002] Some handheld terminals are equipped with a thermal printer and have an integrated printer model that prints input data on a form. In the thermal printer, a thermistor is placed in the center of the thermal head, which is arranged on a line, as a temperature detection element to detect the temperature of the heating element of the thermal head. In other words, the thermistor detects abnormal overheating caused by multiple heating elements in the thermal head, but usually only one thermistor is mounted on the printed circuit board, and it does not detect the temperature corresponding to each heating element based on the relative positions of the heating elements.

[0003] A conventional method, as disclosed in Patent Document 1, is known in which the pins (heating elements) in a print head are divided into multiple groups, the number of printed dots in each group is counted, the printing ratio relative to the total number of printed dots is calculated, and the printing ratio is compared with a certain threshold value to determine whether partial overheating has occurred. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 3607644 Summary of the Invention [Problem to be solved by the invention]

[0005] However, as described above, even if the printing ratio was compared with the threshold value, there was only one thermistor in the center, and it was difficult to detect the temperature of the actual overheated portion that was far from the thermistor. [Means for solving the problem]

[0006] In view of this problem, the thermal printer according to the present invention comprises: In a thermal printer, the detection temperature of a thermistor provided in a thermal head is compared with a threshold temperature to control the printing speed and stop printing. a control unit that divides all the heating elements in the thermal head into a plurality of groups and controls the energization of each group to perform printing control; A counting unit that counts the cumulative number of energized dots in each group up to each printing line; The temperature sensor further comprises a correction temperature calculation unit that identifies the group having the largest cumulative number of energized dots and calculates a corrected temperature based on the distance between the group and the thermistor. Effect of the Invention

[0007] According to the temperature control method of the present invention, the high temperature portion of the thermal head can be estimated during continuous printing, and overheating can be prevented. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a perspective view of a thermal head according to an embodiment of the present invention. [Diagram 2] 1 is a block diagram showing a configuration of a thermal printer according to an embodiment of the present invention. [Diagram 3] 4 is a printing flowchart of a thermal printer according to an embodiment of the present invention. [Figure 4] 6 is a graph showing a distance coefficient of the thermal printer according to the embodiment of the present invention. [Diagram 5] 5 is a graph showing a comparison function of a thermal printer according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Example 1 Hereinafter, an embodiment according to the present invention will be described with reference to the drawings, in which the same reference numerals are used throughout the drawings.

[0010] FIG. 1 is a diagram illustrating a thermal printer according to the present embodiment.

[0011] 1, a thermal head 100 provided inside a thermal printer is composed of a plurality of heating elements (printing dots), which are evenly divided into a plurality of groups. A thermistor TH is provided in the center.

[0012] 2 shows a block diagram of the thermal printer temperature control unit. The thermal printer is connected to a printer control unit 101 and a common control unit 102, and the signal line of the thermistor TH and the signal lines of each group G1 to GX are connected to the printer control unit 101 and the common control unit 102. The group located at the center of the thermal head is designated as GM. The common control unit 102 stores a correction coefficient table, threshold temperature T1, and threshold temperature T2. Hereinafter, the printer control unit 101 and the common control unit 102 may be collectively referred to as the control unit.

[0013] During continuous printing, the printer control unit 101 transmits energization data to the corresponding print dots of each group in the thermal printer to control printing (energization control). At the same time, the common control unit 102 counts the number of energized dots of each group and accumulates them for each line.

[0014] The common control unit 102 compares the cumulative number of energized dots for each group with the number in the center group GM for each line, and identifies the group with the largest cumulative number of dots during continuous printing. The common control unit 102 obtains the correction coefficient corresponding to the group with the largest cumulative number of dots from the correction coefficient table, and transmits it to the printer control unit 101 and the common control unit 102 together with the detected temperature (temperature information) of the center group GM detected by the thermistor TH.

[0015] Using the correction coefficient and detected temperature obtained here, the highest temperature within the thermal head 100 is calculated, and depending on the result compared with the threshold temperature, the printing operation, including print speed control and print temperature control for the next line, is controlled, or the printing operation is stopped.

[0016] FIG. 3 is a flow chart showing the flow of control operations between the thermal printer and the control unit according to this embodiment.

[0017] If all heating elements are divided into X groups and the number of lines for continuous printing is Y lines, the cumulative number of energized dots for each heating element group up to the target printing line can be shown in Table 1. [Table 1]

[0018] N1-1 is the cumulative number of energized dots in the first group G1 on the first line, N1-2 is the cumulative number of energized dots in the second group G2 on the first line, N1-M is the cumulative number of energized dots in the center group GM, and N1-X is the cumulative number of energized dots in the Xth group GX on the first line.

[0019] The temperature of the center group GM is detected by a thermistor, and this value is represented by TM. This temperature is used as the reference value for the correction coefficient, so in this embodiment the temperature correction coefficient for the center group GM is set to MM = 1. On the other hand, the corrected temperature for the kth group GK can be expressed as MK x TM using the temperature correction coefficient MK and the temperature TM detected by the thermistor, so the corrected temperature MK x TM for each heating element group is as shown in Table 2. In this embodiment, the temperature correction coefficient is calculated for the kth group GK using the following equation for the temperature correction coefficient MK, and the corrected temperature for each heating element group is calculated. [Table 2]

[0020] The temperature correction coefficient MK is expressed by the following formula. MK = MM × Lk × f (NY-K) Where: MM: Correction coefficient for the center group of the thermal head Lk: Distance coefficient of thermistor from each group (an example is shown below) f(NY-K): Comparison function of the cumulative number of energized dots between each group far from the thermistor and the central group (an example is shown below)

[0021] An example of the distance coefficient Lx is expressed by the following formula: This function is shown in Figure 4. Lk = A × l(k) Where: l(k): The distance between the kth group GK and thermistor TH A: A constant for normalizing l(x) An example of the comparison function f(NY-K) is expressed by the following formula (1). This function is shown in Figure 5.

number

[0022] In step S101, the common control unit 102 counts the number of energized dots in each group. Next, in step S102, i is set to 2 as an initial value. In step S103, the cumulative number of energized dots up to the Yth line is compared with that of the previous (i-1) group, and if it is greater (Yes in S103), the process proceeds to step S104, where the group with the largest cumulative number of energized dots during continuous printing is identified as the i-th group GI, and the cumulative number of energized dots NY-i of group GI is set to NYmax.

[0023] If the answer is No in step S103, the process proceeds to step S105, where i is incremented. Then, in step S106, it is determined whether i is X, and if it is less than X, the process returns to the determination in step S103, and if it is X, the process proceeds to step S107.

[0024] In step S107, it is determined whether the group with the largest cumulative number of energized dots (i-th group GI that became NYmax in step S104) is the center group GM, and if it is not the center group GM (No in step S107), the process proceeds to step S108. If it is the center group GM (Yes in step S102), the process proceeds to step S109.

[0025] In step S108, the temperature correction coefficient MI is calculated using the above-mentioned formula.

[0026] In step S109, the temperature correction coefficient MI is set to MM (=1).

[0027] In step S110, the common control unit 102 uses the temperature correction coefficient MI calculated in step S108 or step S109 to compare the corrected temperature (MI x TM) with the threshold temperature T1, and if the corrected temperature is equal to or higher than the threshold temperature T1 (Yes in step S110), the common control unit 102 transmits the result to the printer control unit 101 and proceeds to step S111. If the corrected temperature is lower than the threshold temperature T1 (No in step S110), the common control unit 102 transmits the result to the printer control unit 101, returns to S101, continues printing, and continues counting the number of energized dots in each group. Here, the threshold temperature T1 indicates a threshold value at which printing needs to be slowed down to continue printing, but not to the point where printing is stopped.

[0028] In step S111, printer control section 101 controls the printing speed to be reduced.

[0029] In step S112, the common control unit 102 compares the correction temperature (MI×TM) with the threshold temperature T2, and if the correction temperature is equal to or higher than the threshold temperature T2 (Yes in step S112), the common control unit 102 transmits the result to the printer control unit 101 and proceeds to step S113. If the correction temperature is lower than the threshold temperature T2 (No in step S112), the common control unit 102 transmits the result to the printer control unit 101 and returns to S101 to continue printing and continue counting the number of energized dots in each group.

[0030] In step S113, control is performed to stop printing.

[0031] As described above, according to this embodiment, the high temperature portion in the thermal head 100 can be estimated, and appropriate print control can be performed by using a correction temperature according to that position.

[0032] In addition, a plurality of heating elements may be divided into an even number of groups, the two central groups may be designated as GM1 and GM2, and the cumulative numbers of energized dots NY-M1 and NY-M2 may be averaged and used as NY-M.

[0033] It should be noted that the present invention is not limited to the above-described embodiment. For example, · Other functions suitable for thermal printers may be used as distance coefficients and comparison functions. Either of the cumulative energized dot counts of the two central groups GM1 and GM2 may be used as the cumulative energized dot count NY-M of the central group GM. The threshold value does not have to be based on the central group, but may be based on another group close to where the thermistor is located. When there are multiple thermistors, the above-described embodiment may be applied by dividing the thermistors into multiple parent groups centered on the area where the thermistors are arranged. [Explanation of symbols]

[0034] 100 Thermal Head 101 Printer control unit 102 Common control section

Claims

1. In a thermal printer, the detection temperature of a thermistor provided in a thermal head is compared with a threshold temperature to control the printing speed or stop printing. a control unit that divides all the heating elements in the thermal head into a plurality of groups and controls the energization of each group to perform printing control; A counting unit that counts the cumulative number of energized dots in each group up to each printing line; a correction temperature calculation unit that identifies a group having the largest cumulative number of energized dots, and calculates a correction temperature based on a distance between the group and the thermistor.

2. 2. The thermal printer according to claim 1, wherein the correction temperature is calculated by multiplying a temperature correction coefficient calculated for each group based on a distance from the thermistor by the temperature detected by the thermistor.

3. The correction temperature calculation unit 2. The thermal printer according to claim 1, wherein the correction temperature is calculated for each printing line.

4. The control unit is 2. The thermal printer according to claim 1, wherein the print speed is reduced when the correction temperature is equal to or higher than the first threshold temperature.

5. The control unit is 5. The thermal printer according to claim 4, wherein printing is stopped when the corrected temperature is equal to or higher than a second threshold temperature that is higher than the first threshold temperature.

Images