JPH01139281A - Thermal recording device - Google Patents

Abstract

PURPOSE:To shorten a warming-up time upto a normal operating state and eliminate a density unevenness in a linear direction by driving for instance, two heater systems simultaneously or driving a heater with a larger heat generating ability during a warming-up operation, and selecting the blowing direction of an air blower each time a fixed temperature is reached. CONSTITUTION:A warming-up time is shortened by driving two heater systems 6a, 6b in a larger heat generating state during a warming-up operation than during a normal operation. After the warming-up operation, the ambient temperature of a thermal head is kept at near a set temperature T2 by controlling the switching ON/OFF of the heater 6b with the set temperature used as a target temperature. In the meantime, a temperature controller drives blower fans 8a, 8b to a normal rotating direction. Consequently, an atmospheric air is taken into a heat sink 7 from an direction A, and when the temperature becomes lower than Ta, the temperature controll stops driving the blower fans 8a, 8b. When the ambient temperature of the thermal head exceeds T2 again, the temperature controller drives the blower fans 8a, 8b to a rotating direction. Consequently, an atmospheric air is introduced into the heat sink 7 from a direction B.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a thermal recording device.

[Conventional technology]

A thermal recording device heats an ink donor film with a thermal head and transfers an image corresponding to the heating pattern onto recording paper, but even if the thermal head is driven for the same amount of time with the same power, when the ambient temperature is low, The recording density is not light, but becomes dark when it is high.

Therefore, as shown in Japanese Patent Application Laid-Open No. 58-185278, the ambient temperature of the thermal head is detected,
The printing area of the recording paper is heated to a predetermined temperature before printing starts to obtain a uniform temperature, or as shown in Japanese Patent Application Laid-open No. 58-160169, the temperature around the thermal head is If the temperature drops below a predetermined value, the thermal head is temporarily moved away from the platen roller, all pixels of the thermal head are driven, the temperature is raised by the thermal head itself, and then the normal printing state is restored to prevent uneven printing. In addition, Japanese Patent Application Laid-open No. 59-14
As shown in Publication No. 0075, a heat dissipation plate is attached to the back of the thermal head to maintain the surrounding temperature constant, or a heater is installed on the back of the thermal head and a blower blows outside air to the entire thermal head. There are known configurations in which the temperature around the thermal head is maintained at a constant temperature using a fan.

(The problem that Hikari is trying to solve) However, since both of them only perform temperature control during steady operation, there is a long warm-up time for the thermal head to reach the temperature in steady operation after the device is powered on. The problem is that it takes a long time.

In addition, even with a blower fan, the blowing direction is fixed in one direction, so in a linear thermal head with a large number of heating elements arranged in one line, a temperature gradient occurs in the line direction, and the temperature near the inlet of outside air and There is a problem in that density unevenness occurs near the exit.

SUMMARY OF THE INVENTION An object of the present invention is to provide a heat-sensitive recording device that has a short warm-up time until it reaches a steady operating state and can eliminate density unevenness in the line direction.

[Means for solving problems]

The present invention provides at least two
system heater, a blower fan that sends outside air around the thermal head, and a temperature detection element that detects the temperature around the thermal head. At the start of operation, the heaters of the two systems are driven to generate more heat than during steady operation, and When the temperature around the thermal head detected by the temperature detection element reaches the steady operating temperature, the heaters of the two systems are driven to generate heat during steady operation, and each time the temperature around the thermal head reaches the set temperature higher than the steady operating temperature. is provided with a control means for controlling the switching of the air blowing direction of the air blowing fan, and during warm-up, for example, the temperature around the thermal head can be controlled in a short time by driving two heaters at the same time or by driving the heater with a larger heat generation capacity. The temperature gradient in the line direction is made uniform by allowing the temperature to reach a steady operating temperature and then switching the blowing direction of the blower each time the temperature reaches a certain temperature.

[Effect]

During warm-up, two systems of heaters are driven simultaneously, or the one with greater heat generation capacity is driven to heat the temperature around the thermal head. As a result, when the temperature around the thermal head reaches the steady operating temperature, only one of the two heater systems, or the one with the smaller heat generation capacity, is driven.

When a set temperature higher than the steady operating temperature is reached, the blowing direction of the blower is switched to the opposite direction.

〔Example〕

FIG. 1 is a perspective view of the overall configuration showing one embodiment of the present invention, in which an ink donor film 2 is in sliding contact with the light-heat side of a line-shaped thermal head 1 and is transferred from a supply reel 3 to a take-up reel 4. It is designed to be rolled up. A back roller 5 is provided on the back side of the ink donor film 2, and the recording paper 6 is in sliding contact with the surface of the ink donor film by the back roller 5, and an image is transferred by the ink melted from the ink donor film 2. It is designed to receive. In addition, on the back of the summer head 1, there are two heater systems, one divided in the line direction as shown in FIG. 2(a), or the other divided in the sub-scanning direction as shown in FIG. 2(b). 5a.

When the heater 6 consisting of 6b is installed, the heater 6
A heat dissipation plate 7 is disposed on the back surface of the device. Furthermore, two ventilation fans 8a are provided near both ends of the heat sink 7 in the line direction.
8b is provided and configured to send outside air in the direction of the arrow to the heat sink 7.

FIG. 3(a) is an enlarged sectional view showing the structure of the heat sink 7, and FIG. 3(b) is a sectional view viewed from the direction. As shown in the figure, the heat sink 7 has a shape in which the heat radiation efficiency is low at both ends in the line direction, and the heat radiation efficiency is high at the central portion. Further, a thermistor 9 is provided at the outer edge of the thermal head °1.

FIG. 4 is a block diagram showing the configuration of the control system, in which the temperature around the thermal head is detected by a thermistor 9 placed around the thermal head 1, and depending on the detection result, the heaters 6a, 6b and the blower fans 8a, 8b are It has a temperature controller 10 that drives the.

In the above configuration, when the device is powered on, the temperature controller 10 drives the two systems of heaters 6a and 6b regardless of the temperature detected by the thermistor 9. In this case, if the heaters 6a and 6b have the same heat generation capacity, both heaters 6a and 6b are driven at the same time. However, when the heat generating capacities are different, the one with the larger heat generating capacity is driven.

After that, the ambient temperature of the thermal head 1 will be monitored by the temperature controller 10i thermistor 9.
When the steady operating temperature T1 is reached as shown in the graph of FIG. 5, the heater 6a is turned off.

One of the heaters 6b or the heater with a smaller heat generation capacity, for example 6b, is driven. When the set temperature T2 (>TI) is reached in this driving state, the heater 6b
Stops driving. That is, after warm-up, the temperature around the thermal head is maintained near T2 by on/off control of the heater 6b with the set temperature T2 as the target temperature. On the other hand, the blower fans 8a and 8b remain off until reaching T2, but once T2 is reached, the temperature controller 10 drives the fans 8a and 8b in the forward rotation direction.

As a result, outside air is taken into the heat sink 7 from the direction shown in FIG. As a result, the temperature around the thermal head 1 gradually decreases via the heat sink 7 as shown in the temperature change curve in FIG. Stop driving.

As a result, the temperature around the thermal head starts to change in the rising direction again, but once T2 is exceeded, the temperature controller 10 now drives the blowers 8a and 8b in the reverse rotation direction. to this. Therefore, outside air is taken into the heat sink 7 from eight directions in FIG.

That is, the air blowing direction exceeds T2. direction and 8
direction. This equalizes the temperature difference between both ends in the line direction. At this time, the heat dissipation plate 7 is shaped so that the heat dissipation efficiency in the center part in the line direction is 8, so even if the temperature of the outside air passing through this center part is slightly higher than the temperature at both ends, it is still high. The temperature at both ends is maintained at the same level due to heat dissipation efficiency.

In this way, during warm-up, two systems of heaters 5a, (
By driving 3b in a state where it generates more heat than during steady operation, the warm-up time can be shortened. Furthermore, during steady operation, by alternately switching the blowing direction of the blower fan, it is possible to make the temperature gradient in the line direction uniform and eliminate density unevenness in the line direction.

Note that if the thermistor 9 fails, the heating state by the heater 6a or 6b continues for a long time, which may cause damage to the thermal head itself. Therefore, the heater 6a or 6b
If the output of the thermistor 9 does not change for a certain period of time or more after the start of driving, it is determined that a failure of the thermistor has occurred, and it is more effective to issue an alarm.

[Effect of excuse]

As explained above, in the present invention, during warm-up, the two heater systems are driven to generate more heat than during steady operation, so the warm-up time can be shortened. Further, since the blowing direction of the blower fan is alternately switched, it is possible to make the temperature gradient in the line direction uniform and eliminate unevenness in the line direction by e degrees.

[Brief explanation of the drawing]

Fig. 1 is a perspective view of the overall configuration showing one embodiment of the present invention, Fig. 2 is a view showing an example of the II structure of the heater, Fig. 3 is a sectional view showing the structure of the heat sink, and Fig. 4 is the control. FIG. 5, which is a block diagram showing the configuration of the suburban system, is a graph for explaining the operation of the embodiment. DESCRIPTION OF SYMBOLS 1... Thermal head, 2... Ink donor film, Mu, 5... Back roller, 6a, 6b... Heater, 7... Heat sink, 8a, 8b... Ventilation fan, 9...
...Thermistor, 10...Temperature controller. Figure 1 Figure 3

Claims (1)

[Scope of Claim] A thermal recording device that heats an ink donor film with a thermal head and transfers an image corresponding to the heating pattern onto recording paper, comprising: at least two systems of heaters that heat the temperature around the thermal head; A blower fan that sends outside air around the thermal head, a temperature detection element that detects the temperature around the thermal head, and at the start of operation, the two heaters are driven to generate more heat than during normal operation, and the temperature detection element detects the temperature. When the ambient temperature of the thermal head reaches the steady operating temperature, the two heaters are driven to generate heat during steady operation, and
1. A thermal recording device comprising: control means for controlling the blowing direction of the blowing fan to be switched each time the temperature around the thermal head reaches a set temperature higher than a steady operating temperature.