JPS61197257A - Thermal transfer type printer - Google Patents

Abstract

PURPOSE:To prevent a thermal head from being overheated even where high- density printing is continuously performed, by prolonging a non-current-passing time while maintaining a constant current-passing time when the temperature of a thermal head reaches a preset limit value. CONSTITUTION:A temperature-detecting circuit 10 converts an output from a thermistor 8 into temperature data, and supplies the data to a controlling part 11, which controls each part of a thermal transfer type printer, and outputs a printing pulse P. The pulse P is varied based on the temperature data supplied from the circuit 10. Namely, the controlling part 11 enlarge the pulse width of the pulse P when the temperature of the head 6 is low, and decreases the pulse width as the temperature of the head is raised. When the temperature of the head 6 is abnormally raised to exceeds the preset limit temperature, the controlling part 11 prolong the OFF duration of the printing pulse P while maintaining the energizing time to be constant, thereby prolonging a heat- releasing time.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a thermal transfer printer used as an output device for word processors, computers, and the like.

[Prior art]

As is well known, a thermal transfer printer uses a thermal head to apply a heat pattern to a transfer ribbon coated with heat-melting ink, melting the ink layer in a predetermined pattern, and transferring the melted ink to the transfer ribbon. This type of thermal transfer printer prints characters, figures, etc. by transferring them onto paper that is superimposed on the paper.When a large amount of data is printed continuously in this type of thermal transfer printer, the temperature of the thermal head rises. However, there is a problem in that the printing becomes darker and eventually becomes completely unclear. Therefore, in conventional thermal transfer printers, the temperature of the thermal head is measured using a thermistor or the like, and as the temperature of the thermal head increases, the energization time of the thermal head is shortened to maintain a constant print density.

[Problem that the invention seeks to solve]

However, despite the adoption of this method, conventional thermal transfer printers cannot prevent the thermal head from overheating when printing close to a peta, that is, printing with high density. The maximum printing limit was ~4 sheets, and if this was exceeded, the printing would become noticeably blurred and crushed.

SUMMARY OF THE INVENTION In view of the above circumstances, it is an object of the present invention to provide a thermal transfer printer that can maintain a constant print density even when high-density printing is performed continuously.

[Means to solve the problem]

In order to achieve the above object, the present invention provides a method for energizing the thermal head according to the rise in temperature while keeping the non-energizing time constant when the temperature of the thermal head has not reached a preset limit value. While shortening the time, if the temperature of the thermal head reaches the limit value, the non-energizing time is lengthened while the energizing time is kept constant.

[Effect]

When the head reaches the overheating state button, the heat dissipation time is increased by increasing the non-energization time while keeping the energization time constant.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a mechanical diagram showing the mechanical configuration of a thermal transfer printer according to an embodiment of the present invention. In this figure, l
is a transfer ribbon, the upper surface (the upper surface in the figure) of which is coated with heat-melting ink. The transfer ribbon 1 is sent out from the supply roller 2, passes through the printing section 3, and is wound up by the take-up roller 4. Further, reference numeral 5 denotes a transfer paper, the surfaces of which are coated with the ink of the transfer ribbon 1 are superimposed and passed through the printing section 3 together with the transfer ribbon 1. The printing section 3 includes a thermal head 6 and a platen roller 7, and the thermal head 6 is provided with a heat generating cell (not shown) that generates heat when energized. During printing, the thermal head 6 is urged toward the platen roller 7 to press the transfer ribbon 1 and the transfer paper 5 together, and the heating cell generates heat to melt the ink coated on the transfer ribbon 1&C. The image is transferred onto the transfer paper 5.

At this time, the platen roller 7 rotates by a small angle in the direction of the arrow Y, and moves the transfer ribbon 1 and the transfer paper 5 in translation in one-dot increments. The thermal head 6 also includes a thermistor 8.
is attached, and the temperature of the thermal head 6 is measured by this thermal star 8.

Next, FIG. 2 is a block diagram showing the electrical configuration of the thermal transfer printer, and partial sums corresponding to those in FIG. 1 are given the same reference numerals. In this figure, reference numeral 10 denotes a temperature detection circuit, which converts the output of the thermistor 8 into temperature data (digital data) and then supplies it to the control section 11. The control section 11 includes a CPU (central processing unit), a work memory, a program memory, etc., and controls each section of the thermal transfer printer and outputs printing pulses P. The pulse width of this printing pulse P is designed to change based on temperature data supplied from the temperature detection circuit 10. That is, when the temperature of the thermal head 6 is low, the control unit 11 calculates that the sum is
While the pulse width of the printing pulse P is widened, when the temperature of the thermal head 6 rises, the pulse width is narrowed as the temperature rises.

Further, when the temperature of the thermal head 6 abnormally rises and exceeds a predetermined temperature limit, the control unit 11 lengthens the time during which the print pulse P is turned off (hereinafter referred to as pulse off time). On the other hand, 12 is a motor drive circuit,
Under the control of the control section 11, the step motor 13 is driven to rotate the platen roller 7 by a small angle. Also, 14
is a print data memory that stores dot data supplied from an external computer or the like. This stored dot data is read out by the address signal ADR supplied from the control section 11 and supplied to the head drive circuit 15. The head drive circuit 15 includes the print data memory 1
The thermal head 6 is made to generate heat based on the dot data supplied from the thermal head 6, and is composed of the same number of registers and gate circuits as the heat generating cells of the thermal head 6. When the printing pulse P is supplied from 11, a specific heat generating cell of the thermal head 6 is energized to generate heat based on the stored dot data. In this case, the energization time of the heating cell and the pulse width of the printing pulse P are equal.

In the above configuration, when the print data memory 14 & c dot data is supplied from an external computer etc., the thermal head 6 is first urged toward the platen roller 7 side by a command from the control section 11, thereby causing the transfer ribbon l and the transfer paper 5 is pressed.

Next, the control unit 11 supplies the address signal ADR to the print data memory 14 and causes the dot data in the print memory 14 to be stored in the register of the head drive circuit 15 in sequence. Then, when the dot data is stored in all the registers of the head drive circuit 15, the control section 11 controls the print pulse P.
is supplied to the head drive circuit 15. As a result, the heating cell of the thermal head 60 generates heat, and the ink on the transfer ribbon 1 is melted and transferred onto the transfer paper 5. In the following steps, the control section 11 supplies a drive command to the motor drive circuit 12, rotates the platen roller 7 by a minute angle, and moves the transfer ribbon l and the transfer paper 5 in translation by a length corresponding to one dot. Next, the control unit 11 outputs a predetermined pulse P (after the pulse off time has elapsed, the dot data is transferred to the head drive circuit 15 again for printing).
The output state of is shown in Fig. 3 (a). That is, the printing pulse P has a pulse width of τO, and the pulse off time is T.

It is. Here, the pulse off time To is a time determined by the characteristics of the step motor 13, and is the minimum time during which the step motor 13 can follow the sum that causes step-out.

In this way, the pulse width τ. The printing pulse width τ (after applying pulse P and then again after a pulse off time of T6).

By repeating the operation of printing a printing pulse of The temperature is detected by the temperature sensor 8, and the detection result is converted into digital data by the temperature detection circuit IO and supplied to the control unit 41. As printing progresses, the temperature of the thermal head 6 begins to rise. The control unit 11 adjusts the pulse width of the printing pulse P according to the rise in temperature of the thermal head 6 as shown in FIG. 3 (←).

As shown in f→, r,′,r,,(τ.〉τ1〉τ,)
and gradually narrow it down. In this case, the pulse off tie J4fr0 is kept constant in order not to reduce the printing speed. In this way, by gradually narrowing the pulse width of the print pulse P, the heat generation time of the heat generating cells is shortened, and it is possible to prevent the thermal head 6 from overheating.

Now, if the printing density is normal, overheating of the thermal head 6 can be prevented by reducing the pulse width. However, when high-density printing is performed continuously, the temperature of the thermal head 6 continues to rise because the amount of heat stored is greater than the amount of heat released, even though the pulse width is at its narrowest at f. When the temperature of the thermal head exceeds a predetermined temperature limit, the control unit 11 sets the pulse off time to Ts while keeping the pulse width of the printing pulse at its narrowest, as shown in FIG. (To <To). Here, the above-mentioned limit temperature temperature and pulse off time T.

is a value determined by experiment. That is, high-density printing is performed with the pulse width of the printing pulse P set to τ3 and the pulse off time set to To. At this time, the temperature immediately before printing starts to bleed, fade, etc. is determined, and the temperature immediately before this is determined as the above-mentioned limit temperature temperature. In addition, the pulse off time at which the amount of heat radiation and the amount of heat storage match for a person at the limit temperature is determined, and this is set as the above-mentioned pulse off time T. Therefore, when high-density printing is performed, the temperature of the thermal head 6 reaches the limit temperature A and remains approximately constant at this limit temperature, as shown in FIG. Therefore, even when performing high-density printing, overheating of the thermal head 6 can be prevented.

〔Effect of the invention〕

As explained above, according to the present invention, when the thermal head has not reached a preset limit value, the non-energizing time is kept constant, and the energizing time is shortened according to the rise in temperature of the thermal head. On the other hand, when the temperature of the thermal head reaches the above-mentioned limit value, the energization time is kept constant and the de-energization time is increased, so even when performing continuous high-density printing, overheating of the thermal head can be prevented. It is possible to maintain consistent print quality without bleeding or crushing.

[Brief explanation of drawings]

FIG. 1 is a machine groove diagram showing the mechanical structure of a thermal transfer printer according to an embodiment of the present invention, FIG. 2 is a block diagram showing the electrical groove bottom of the thermal transfer printer, and FIG. , a waveform diagram showing the printing pulse P changing as the temperature rises;
FIG. 4 is a graph showing how the temperature of the thermal head changes. 6... Thermal head, 8... Surge star, 10 Temperature detection circuit (8 and 10 above are temperature detection means), 11... Control unit (judgment means, 1 energization control means, 2nd energization control means). Figure 1 Figure 8 Figure 4 Questions

Claims (1)

[Claims] A thermal transfer printer that maintains a constant print density by adjusting the ratio of energized time and non-energized time of the thermal head includes a temperature detecting means for detecting the temperature of the thermal head, and a temperature detecting means for detecting the temperature of the thermal head, the temperature of the thermal head being set in advance. determining means for determining whether or not the temperature of the thermal head has reached the limit value; a first energization control means that shortens the energization time accordingly; and a second energization control means that lengthens the non-energization time while keeping the energization time constant when the temperature of the thermal head reaches the limit value. A thermal transfer printer, characterized in that it is equipped with energization control means.