JPH069955U - Thermal recording device - Google Patents

Abstract

(57) [Summary] [Purpose] To increase the print density of the thermal recording device at low temperature. [Configuration] The control unit 1 sends received FAX data to be stored in a RAM to the thermal head 2 from a print data line C for one line, and print pulses by a latch signal and an energization signal for each heating element block from a and b lines. The data is sent out, and the power is supplied from the power supply unit 4 to perform printing. When the detection data of the sensor circuit 3 is lower than the predetermined value, the control unit 1 controls the pulse width of the normal print pulse, and the pulse width temperature control for each cycle of the print pulse controls the thermal head in the case of large synchronization. The difference in print density is eliminated by compensating for the temperature of the heating element of.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a thermal recording device, and more particularly to a device for adjusting the recording density of a thermal head at low temperature.

[0002]

[Prior art]

 FIG. 3 is a block diagram of a conventional thermal recording apparatus. The thermal head 101 is a head provided with heating elements for one line in a row. The control unit 100 serially inputs the print data for one line of the FAX data of the RAM to the shift register, and the latch signal from the control unit 100. The print data is recorded by the print pulse by the energization signal to the heating element group in units of 4 blocks. After recording one line, the platen 106 and the roller are driven by the motor 105 to feed the paper and move to the next print line.

FIG. 4 is a characteristic diagram of the temperature of the thermal head at a low temperature. When the temperature detected by the sensor (thermistor) that detects the temperature of the thermal head is low, such as 10 ° C. or less, the control unit 100 prints a pulse. The pulse width is controlled to increase the pulse width as shown in to (FIG. 4) to adjust the print density.

[0004]

[Problems to be solved by the device]

 However, in the conventional example shown in FIG. 3, the temperature is detected by the thermistor 103 on the thermal recording head 101, and when the temperature is low, the print pulse width is adjusted to increase the density, but as shown in FIG. In addition, when the cycle between the print pulses becomes large as T2, the temperature of the heating element that has once risen is cooled during the cycle T2, and when the pulse width to by the pulse width control, the thermal time constant (thermal inertia) causes There is a problem that the cycle cannot be followed, and as a result, a temperature difference tx with respect to the specified temperature tj of the thermal head temperature, which does not occur during the short cycle T1, occurs and density unevenness occurs.

The present invention has been made in view of the above-mentioned problems, and provides a thermal recording apparatus that does not cause a print density difference at low temperatures by performing control corresponding to the cycle of the print pulse depending on the detected temperature. The purpose is to do.

[0006]

[Means for Solving the Problems]

 In order to achieve the above object, in a thermal recording apparatus that controls the pulse width of the printing pulse sent to the thermal head to adjust the print density, a temperature detection circuit that detects the temperature of the thermal head and the temperature detected by the temperature detection circuit. When the temperature is lower than the set value, the control unit controls the duty ratio in accordance with the synchronization of the print pulse sent to the thermal head, and adjusts the print density.

[0007]

[Action]

 With the above configuration, if the temperature of the thermal head does not rise at low temperature and the low temperature is detected by the sensor of the thermal head, the control unit outputs the thermal pulse to the thermal head. Since the duty ratio control is also performed depending on the length, the print density difference due to the temperature drop of the thermal head can be eliminated even when the pulse period is large.

[0008]

【Example】

 An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, reference numeral 1 is a control unit for sending the FAX reception data stored in the RAM to the thermal head and controlling the whole.

Reference numeral 2 is a thermal head having a shift register, a latch circuit, and a heating element group divided into four blocks. Reference numeral 3 denotes a sensor (thermistor) circuit that detects the temperature of the thermal head 2, converts it into voltage, converts it into A / D, and sends it to the controller 1 as temperature data of the pulse width temperature controller 11 according to the detected temperature. Is a power supply unit that energizes the thermal element group when the thermal head 2 prints. The same configurations as those of the other conventional examples are designated by the same reference numerals and the description thereof will be omitted.

Next, the operation will be described. From the RAM storing the facsimile reception data, the control unit 1 serially inputs the print data for one line from the print data line c to the shift register in the thermal head 2, and the print data / latch signal from the latch line b. An energization signal designating the energization block of the heating element group in the thermal head 2 divided into 4 blocks is sent from the energization line a, and is supplied from the power supply section 4 by the printing pulse of the a and b lines. Print.

When the detected temperature of the sensor 3 does not reach the set value even at low temperature, the pulse width temperature control unit 11 of the control unit 1 judges the detection data from the sensor 3 and determines the pulse of the print pulse. Width control is performed to adjust print density.

FIG. 2 is a characteristic diagram of the thermal head temperature. As shown in FIG. 2, the control unit 1 sets the print pulse width to a large value by the pulse width temperature control unit 11 during normal temperature detection at the same time as normal. When the cycle of the print pulse is judged and compared with the short cycle T3 and the cycle is longer than T4, at the time of the next print pulse, the head temperature changes from the specified head temperature tj as shown by the thermal head temperature curve Z. Since it has been cooled considerably and has decreased, the duty ratio control is performed in which the pulse width t2 is set larger corresponding to the period T4 as compared with the previous pulse width t1, and the duty ratio is sent to the thermal head 2. Therefore, the printing pulse width t2 corresponding to the cycle T4 is set to be sufficiently large, and the heating element of the thermal head 2 can reach the specified temperature Tj by being energized for the period t2. Therefore, at the printing pulse width t1 and t2. There is no difference in printing density.

In this embodiment, when the thermal head 2 operates at a low temperature, the control unit 1 controls the pulse width at the time of the normal low temperature as well as the periodic data including the periodic data of the print pulse. Since the duty ratio is controlled, the print density difference at low temperature can be eliminated.

[0014]

[Effect of device]

 As described above, according to the present invention, the temperature detection circuit for detecting the temperature of the thermal head, and the duty corresponding to the cycle of the print pulse sent to the thermal head when the temperature detected by the temperature detection circuit is lower than the set value. Since the control unit for controlling the ratio and adjusting the print density is provided, the print quality of the thermal recording apparatus can be improved.

[Brief description of drawings]

FIG. 1 is a block diagram of a thermal recording apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing temperature characteristics of a thermal head of the embodiment shown in FIG.

FIG. 3 is a block diagram of a conventional thermal recording apparatus.

FIG. 4 is a diagram showing a thermal head temperature characteristic of the conventional apparatus shown in FIG.

[Explanation of symbols]

 1 control unit 2 thermal head 3 sensor circuit 4 power supply unit 11 pulse width temperature control unit

Claims (1)

[Scope of utility model registration request] 1. A thermal recording apparatus for controlling the print density by controlling the pulse width of a printing pulse sent to a thermal head, wherein a temperature detection circuit for detecting the temperature of the thermal head and a temperature detected by the temperature detection circuit are set. A thermal recording apparatus comprising a control unit for controlling a duty ratio control and adjusting a print density in response to synchronization of a print pulse sent to the thermal head when the temperature is lower than a predetermined value.