JPH0269280A - Thermal recorder - Google Patents

Abstract

PURPOSE:To reduce the possibility that a density may be increased with progressing recording by mounting a cooling fan in the vicinity of a thermal recording head, providing temperature sensors on the upstream and downstream part of the thermal recording head, and controlling the air flow rate of the fan in proportion to a difference between the temperature respectively detected by the temperature sensors. CONSTITUTION:A fan 17 is controlled by a control circuit for changing the rotating speed of the fan 17 under a voltage control, a frequency control, or the like in proportion to a difference (t2-t1) between temperatures t1 and t2 respectively detected by temperature detection elements 20, 21. When a heat generated in a recording head 5 simultaneously with the start of recording raises the temperature, a fin starts warming an air current, whereby the temperature t2 of the temperature detection element 21 on the downtream side starts increasing. Thus, the control circuit starts increasing the rotating speed of the fan 17 in proportion to (t2-t1) and, therefore, an air flow capacity is increased, a large amount of heat is released from the fin, and the temperature increase of the recording head 5 can be held small. As a result, though the temperature is increased by a small amount at the start of recording, the temperature can be kept constant thereafter.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a thermal recording device for recording an image on a television screen or a CRT display as a hard copy on paper or the like.

Conventional technology In thermal recording and thermal transfer recording, in order to faithfully produce hard copies of images with shading, it is necessary to apply even heat energy to all parts of a single recording sheet, but in general, As shown in Figure 1, due to the effects of heat accumulation, the density is usually light at the beginning of the recording and becomes darker towards the end, and the recorded hard copy is not the same as the original image (on a CRT). ), the fidelity becomes extremely poor.

In order to correct this, conventionally, the recording energy applied to the heating element is decreased as recording progresses, thereby keeping the recording density almost constant.

In order to make the temperature uniform in one hard copy, it is desirable that the peak temperature T0 of the heating element remains constant over time as shown in FIG. 2, but if recording energy is not controlled, As shown in Figure 3, the peak temperature is T1, T
, , T, . . . , the recording energy gradually becomes excessive and the recording density also increases.

As shown in Fig. 4, this means that heat from a plurality of heating elements 1 arranged linearly on the ceramic base
This is also to gradually increase the temperature of the metal base 3.

The temperature indicated by T in FIG. 3 indicates the temperature rise of these two bases.

By attaching a temperature sensor to the metal base 3 as shown in FIG.
As shown in the figure, recording energy is reduced to prevent a rise in peak temperature, or the total number of recording signals from the start of recording is totaled, and similar control is performed in proportion to this total number.

Problems to be Solved by the Invention However, these controls control the recording head as a whole, making it difficult to perform partial control.

For example, when making a hard copy as shown in Figure 6, almost uniform recording can be achieved with the control shown in Figure 5 from the start of recording to the point where people pass through, but at point A, the recording range shown by B is As shown in FIG. 7, the peak temperature Tm is equal to the peak temperature T! of FIG. 1, the recording in section B was very faint, and there was a problem that the overall density was unbalanced.

Means for Solving the Problems The present invention is a thermal recording device that obtains an image by transferring ink or dye on an ink film onto a receptor using thermal energy generated by a thermal recording head, the thermal recording device comprising: A fan for cooling the thermal recording head is provided, and a temperature sensor 1.2 is provided at least upstream and downstream of the thermal recording head in the flow path of the airflow generated by the fan, and the temperature sensor 1.2 The flow rate of the fan is controlled in proportion to the difference (tz-tl) of each detected temperature.

Effect of the present invention By controlling the air volume as described above, when the temperature of the recording head begins to rise, a difference in detected temperature appears, the air volume increases, and heat begins to be taken away from the recording head. The more excess heat is generated, the more heat is taken away by the fan, so it is possible to suppress the temperature rise of the recording head to a small extent.Therefore, even as recording progresses, the density is less likely to increase. Even if a pattern like this is drawn, almost uniform density can be obtained at any point.

Embodiment FIG. 1 is a schematic diagram of essential parts of an embodiment of the thermal recording device of the present invention.
FIG. 2 shows an explanatory diagram of the operation of FIG. 1.

The configuration of the thermal recording device of the present invention will be explained.

Recording head! is composed of a ceramic base 6 and a metal base 7. A platen g is pressed against the recording head via an ink film IO and a receptor made of paper, plastic film, or the like.

The receiver is further held between a capstan 11 and a pinch roller /2, and is fed from a roll /3. A roller l≠ is pressed onto the platen r via a receptor. Platen? is lightly driven between it and a drive unit (not shown) via a mounting board. The ink film /θ is wound onto the take-up reel lB supplied from the supply reel /J' with a light torque. A heating element is arranged at the contact portion between the recording head and the platen.

Before recording, press the recording head as shown in Figure 2! is released from platen ♂, and the receptor is moved by approximately one screen in the direction of arrow B by the driving force of platen r, capstan //, and pinch roller /2.

At this time, the outer circumferential speed of the platen is set slightly higher than the circumferential speed of the capstan //, and while the receiver is being transferred, the receiver is given a light tension between the platen r and the capstan/l. Never relax.

Next, as shown in Fig. 1, the recording head is pressed against the platen ♂ and the drive unit (not shown) starts to rotate in reverse, and the capstan l
The receiver is transported in the direction of the arrow A by the pinch roller /2. Thermal energy is applied to the recording head to transfer the ink on the ink film 10 onto the receptor. The receiver and the ink film 10 move at almost the same speed, the ink film IO is taken up on the take-up reel L, and the receiver moves on the capstan // and the roll 1.
It curls and accumulates between 3 and 3. Recording is completed when the receptor is conveyed by one screen. Although a negative color ink film is described here, recording can be completed by repeating the same process three or four times with three color or four color films including black.

FIG. 3 and FIG. 4 show schematic diagrams of main parts of the present invention.

FIG. 4 shows a cross-sectional view of FIG.

/7 indicates a variable air volume fan, and /11/ indicates the streamline of the airflow generated by the fan 17. 20°2/ indicates temperature detecting elements such as thermistors arranged upstream and downstream of the airflow recording head j, respectively. Reference numeral 22 denotes an airflow guide for guiding the airflow along the fin portion 7/ of the recording head j.

Fan 7 rotates at a constant low speed when not recording, and a small amount of airflow flows through the recording head j, but the recording head! Since no heat is generated in the temperature sensing elements 20, 2
/ is detecting the same temperature.

The fan 17 detects each temperature 1. It is controlled by a control circuit (not shown) that changes the number of revolutions of the fan/7 in proportion to the difference between the two (t2tl) by voltage control, frequency control, etc., and heat is generated in the recording head j at the start of recording. When the temperature starts to rise, the fin 7/ starts to warm the airflow, and the temperature t of the temperature sensing element 2/ on the downstream side starts to rise (t2tl).
The control circuit begins to increase the rotation speed of the fan 17 in proportion to
Therefore, the amount of air increases, the heat taken away from the fins 7/ increases, and the temperature rise of the recording head j remains at a small value. As a result, as shown in FIG. 5, although there is a slight temperature rise at the start of recording, the temperature is kept constant thereafter.

Effects of the Invention In the present invention, with the above configuration, almost the same recording energy is applied to the entire screen, so even in a recording pattern as shown in FIG. 11, every point can be recorded with the same density. , it is possible to obtain a high-quality record with uniform density throughout.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of the main parts of an embodiment of the thermal recording device of the present invention;
2 is an explanatory diagram of an example of the operation shown in FIG. 1, FIG. 3 is a front view of an embodiment of the recording head section of the present invention, and FIG. 4 is a cross section taken along line xx' in the center of FIG. 3. 5 is a temperature change diagram of the heat generating element obtained by the thermal control of the present invention, FIG. 6 is a hard copy diagram, FIG. 7 is an ideal temperature change diagram of the heat generating element of the recording head, and FIG. A temperature change diagram of the heating element without thermal control; FIG. 9 is a cross-sectional view of a recording head with conventional thermal control;
Figure 1O is a temperature change diagram of a heating element under conventional thermal control, Figure 11 is an example of a recording pattern that could not be resolved with conventional thermal control, and Figure 12 is a partial heating element under conventional thermal control. A temperature change diagram is shown. J-: recording head, 6: ceramic base, 7: metal base, t nib platen, ta: receptor, lO: ink film, ll: capstan, 12: pinch roller,
13: Roll, /! : Roller, /j: Supply reel, 16: Take-up reel, /7: Fan, 20.2/ :
Temperature sensing element, 22 Ni guide.

Claims (1)

[Claims] A thermal recording device that obtains an image by transferring ink or dye on an ink film onto a receptor using thermal energy generated by a thermal recording head, the thermal recording device comprising a fan for cooling the thermal recording head in the vicinity of the thermal recording head. Temperature sensors 1 are provided at least upstream and downstream of the thermal recording head in the flow path of the airflow generated by the fan.
, 2 are provided, and each temperature t detected by the temperature sensor is
A thermal recording device characterized in that the flow rate of the fan is controlled in proportion to the difference (t_2-t_1) between _1 and t_2.