JPS61195860A - Thermal head control - Google Patents

Abstract

PURPOSE:To reduce stand-by time attributable to a soaring head temperature and further eliminate stand-by time by increasing pause time of applied pulse to a thermal head according to a temperature increase of the thermal head. CONSTITUTION:A microprocessor circuit 1 detects the temperature of a thermal head 4 by a head thermister 4h on a thermal head 4, and calculates an applied pulse width according to a preset thermal head temperature-printing pulse width characteristic. The microprocessor circuit 1 calculates a thermal head temperature-pause time characteristic preset based on the previously detected thermal head temperature. The microprocessor circuit 1 transfers printing data of a single scan line to the thermal head 4 when completing calculation of an applied pulse width and pause time, and sequentially outputs applied pulses STB1-STB4 based on the previously obtained applied pulse width and pause time. Then the circuit repeats the operation until monochromatic printing is completed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a method for controlling a thermal head in a thermal transfer device, and more particularly to control of the pause time of applied pulses.

[Conventional technology]

In a multicolor thermal transfer device, a recording paper is placed on the ink layer of an ink carrier coated with thermally transferable ink, and the ink carrier is heated in accordance with the recording pattern using a thermal head from the opposite side of the ink layer. Recording is performed by transferring to recording paper. In this thermal transfer method, at least yellow (Y), magenta (M
), cyan (q), and cyan (q) can be repeatedly applied to make it easy to record in multiple colors.

Conventionally, when performing multicolor recording using this method, a method is known in which the printing density is controlled by controlling the width of the pulse applied to the thermal head.

FIG. 7 is a block diagram of a conventional device using this method.
2 is a microprocessor circuit, and 2 is an ink sheet position detection circuit. Reference numeral 3 designates an ink donor sheet, which is composed of four colors of ink 3b coated on an ink carrier 3a such as a polyester film, and markers 3c attached corresponding to each ink color. Here, the ink 3b includes each color of yellow (Y), magenta (CM), cyan (C), and black (B), and is applied on the ink carrier 3a in this order. 4 is a thermal head, which includes a dot resistor 4c and a shift register 4a that receives a printing data pattern.
have. To thermal “rad 4 dot resistor 4C
is divided into four blocks, and the dot resistor 4c of each block receives an applied pulse 5TBI (4
d), 5TB2 (4e), 5TB3 (4f), ST
Controlled by B4 (4g). moreover,
It has a head thermistor 4h for detecting the temperature of the thermal head 4.

FIG. 8 is a flowchart showing an outline of the control method in this conventional device, and FIGS. 9 and 10 show the applied pulse (
FIG. 4 is a timing diagram of STBI~4).

Next, details of a conventional method of controlling applied pulses of a thermal head will be described using FIGS. 7 to 1O.

The microprocessor circuit 1 uses the ink sheet position detection circuit 2 to detect the marker 3C on the ink donor sheet 3, thereby recognizing the ink color to be printed,
The printing data corresponding to the ink color is converted into serial data and transferred to the thermal head 4 together with a clock signal. To thermal ・RAD 4 stores this serial data in shift register 4a.

Next, the microprocessor circuit 1 applies pulses 5TBI (4d), 5TB2 (4e), 5 to each dot resistor block of the thermal head 4 in order to perform printing.
TB3 (4f), 5TB41:4g) were given sequentially, and N
An AND element (4b) performs a NAND operation on the output of the shift register 4b and these applied pulses, and applies the result to the dot resistor 4c of each block. As a result, current flows through the dot resistor 4C of each block for the application pulse time described later, and the dot resistor 4c generates heat.

The heat thus generated melts the ink applied to the ink donor sheet 3. As a result, the printer paper (
(not shown), the ink is fused and printing is completed.

Here, the applied pulse width is generally determined as shown in the flowchart of FIG. That is, the microprocessor circuit 1 detects the temperature of the thermal head 4 by the head thermistor 4h on the thermal conductor 4 (step 5a), and generates a printing pulse based on a predetermined thermal head temperature-printing pulse width characteristic. Calculate the width (step 5b).

Next, step 5c) transfers data for one scanning line to the thermal head 4, and then applies pulses 5TB1 to 5TB.
Apply TB4 (step 5d). Then, application pulses STB 1 to 5 TB4 are applied to the thermal head 4 with the same pulse width until printing of one ink color is completed. This makes it possible to change the density for each ink color.

According to such application pulse width control, as shown in FIG. 9, when the temperature of the head 4 is low, the application pulse STB 1
is output for Ta (ms), and after the pause time ta has elapsed, applied pulses 5TB2, 5TB3, and 5TB4 are output next. Thereafter, as the head temperature rises as printing continues, the applied pulse width is shortened from the graph of thermal head temperature vs. printing pulse width characteristics, and as shown in FIG. 10, the applied pulse width Tb (ms ), pause time tb(m
Imprinting begins in step s). In this case, the pause time is generally ta=tb.

[Problem that the invention seeks to solve]

In the case of thermal transfer, there are many opportunities to print graphic images displayed on a television monitor of a personal computer, and the rate of printing one screen (printing rate) is high compared to facsimile machines and the like.

For this reason, if printing close to the entire surface continues, the temperature of the thermal head will rise significantly. Therefore, it is possible to radiate heat by attaching a heat dissipation plate, but due to conditions such as increasing household demand in the future, miniaturization will be required. Forced air cooling using a fan motor becomes difficult.For this reason, in order to protect the thermal head, a control method that stops printing and waits for the head temperature to drop when the temperature exceeds a certain level can be considered, but once Waiting for the increased temperature of the thermal head to cool down is undesirable as it takes time and forces the user to spend unnecessary waiting (unusable) time.Furthermore, if the ambient temperature is high, the above-mentioned waiting time This happens frequently and is extremely inconvenient.

The present invention was made in order to solve such problems, and an object of the present invention is to provide a thermal head control method that can shorten the standby time associated with an increase in head temperature, and further eliminate the standby time. It is said that

[Means for solving problems]

In the present invention, the pause time is changed according to the temperature rise of the thermal head.

Further, in another invention, the pause time is controlled based on the difference between the temperature of the thermal head and the ambient temperature.

(Function) As the temperature of the thermal head increases, the downtime becomes longer, and the rate of temperature rise is suppressed.Furthermore, the downtime is adjusted in relation to the ambient temperature.

〔Example〕

Hereinafter, the present invention will be explained with reference to Examples.

FIGS. 1 and 2 are timing diagrams of applied pulses STB1 to STB4 in the first embodiment of the present invention.

Note that the hardware configuration is the same as before. In Fig. 1, when the head temperature is relatively low a°C, the applied pulse width is Ta'' (ms), and the pause time is ta' (m
s).

Figure 2 shows that when the head temperature rises and reaches b'c as the number of sheets printed increases, the applied pulse width becomes short to Tb' (ms) and the pause time becomes tb' (ms). It shows. In both Figures 1 and 2, pulses 5TBI and 5T are applied to thermal-\RAD 4 with the above applied pulse width and pause time.
B2, 5TB3, and 5TB4 are sequentially output, indicating that an applied voltage is applied to the dot resistor 4C.

Next, the control operation of the present invention will be explained according to the flowchart shown in FIG. The microprocessor circuit 1 detects the temperature of the thermal head 4 using the head thermistor 4h on the thermal head 4 (step 6a), and calculates the applied pulse width based on a predetermined thermal head temperature-application pulse width characteristic (step 6a). 6b).

This calculation method is as follows: ■Applied pulse width Ta' -
A method of calculating the applied pulse width as a function of f (head temperature), or ① Prepare a correspondence table between the head temperature and the corresponding applied pulse width in the memory of the microprocessor circuit 1, and calculate the applied pulse width at an arbitrary head temperature. One possible method is to read the pulse width from memory.

Next, the microprocessor circuit 1 calculates a pause time based on a predetermined thermal head temperature integral pause time characteristic from the previously detected thermal head temperature (step 6C). In this example, when the head temperature increases,
The idea is to suppress the rate of increase in head temperature.
In order to suppress the ratio of applied pulse output time per unit time, it has a characteristic of increasing the pause time. That is, in FIGS. 1 and 2, when the head temperature increases from a''c to b'c, the applied pulse width is Ta'(ms)>
Tb' (ms), while the pause time is formed as t a' (ms) < t b' (ms)
and increase.

As a method for calculating this pause time, it is possible to calculate it using a function or a correspondence table, similar to the case of calculating the applied pulse width described above.

After the microprocessor circuit 1 finishes calculating the applied pulse width and rest time in this way, it then transfers the printing data for one scanning line to the thermal head 4 (step 6d), and calculates the applied pulse width calculated previously. and sequentially output applied pulses 5TBI to 5TB4 based on the pause time (
Step 6e). Then, the above operations (step 6d) and (6e) are repeated until printing of one color is completed.

Next, another embodiment of the present invention will be described in which an ambient temperature thermistor for detecting the ambient temperature is added and the downtime is controlled including the ambient temperature condition. Figures 4 and 5
The figure is a timing diagram of applied pulses in another embodiment. In FIG. 4, when the head temperature is relatively low a''C and the ambient temperature is A'C, the applied pulse width is set to ta''A (ms), and the rest time is ta''A (m
s).

FIG. 5 is a timing diagram when the head temperature rises to bt' as the number of sheets to be printed increases and the ambient temperature is B'C. At this time, the applied pulse width is Tb''B (ms
), and the pause time is set to tb''B (ms).

Next, FIG. 6 is a flowchart for performing such control, in which the microprocessor circuit 1 first detects the temperature of the thermal head 4 using the head thermistor 4h on the thermal head 4 (step 7a), and then detects the temperature using the ambient temperature thermistor. Detect the ambient temperature (step 7b).

Next, in the same manner as in the first embodiment, the applied pulse width is calculated based on the predetermined thermal head temperature-applied pulse width characteristic.

Next, the microprocessor circuit 1 calculates the strobe rest time based on the ambient temperature and the thermal head temperature according to the following procedure. In the embodiment, first, the pause time at the reference ambient temperature (20° C. in the embodiment) is derived from the characteristic table 7d showing the thermal head temperature fixation time.

Next, a pause time coefficient corresponding to the normal ambient temperature is derived from the characteristic table 78 showing the pause time coefficient with respect to the ambient temperature,
By multiplying the rest time at an ambient temperature of 20° C. derived from the characteristic table 7d by this rest time coefficient (7f), the rest time for a more optimal thermal rad temperature and ambient temperature is determined. In characteristic table 7e, the rest time coefficient is set to 1 at an ambient temperature of 20°C, and as the ambient temperature rises, the rest time coefficient increases to suppress the amount of heat generated per unit time.Conversely, when the ambient temperature is 10°C, When the time is reduced as shown in FIG. For example, consider a case where the ambient temperature is A.degree. C. and the thermal head temperature is a degree. First, the pause time when the thermal head temperature is a degree is determined from characteristic table 7d as t't, 20, which is the pause time when the ambient temperature is 20 degrees Celsius. Next, find the rest time coefficient K (A) at ambient temperature A'C from characteristic table 7e and find the rest time ta''A=K
(A) By calculating the formula of X t%, 2D using the microprocessor circuit 1, the optimum pause time is determined.

In the above, the characteristic tables 7d and 7e are calculated by the microprocessor circuit 1 as a function. Alternatively, it is conceivable to prepare a correspondence table in the memory of the microprocessor circuit 1 and retrieve it.

Next, 7g) to transfer one line of data to the thermal head 4, and 7c and 7d described above to print.

Pulses are sequentially applied to strobe signals STB1 to STB5TI34 based on the head strobe width and pause time determined in step 7e (7h). Then, repeat steps 7g and 7h until one color of printing is completed.

For example, the above is Y (yellow), 2M (magenta).

By overlapping printing with C (cyan) and black, color printing is performed as multiple thermal transfer.

〔Effect of the invention〕

As explained above, in the present invention, since the pause time of the applied pulse to the thermal head is controlled by the head temperature condition, the pause time becomes longer when the temperature is high, and as a result, the ratio of the applied pulse time per unit time is suppressed. , an increase in head temperature is suppressed.

Moreover, if the above control is performed in relation to the ambient temperature, more accurate control according to the ambient temperature becomes possible.

This makes it possible to shorten the standby time of the printing device as the number of sheets to be printed increases. Furthermore, it is also possible to delete the standby state.

Therefore, a particularly effective effect can be obtained when the printing rate per screen is high for color images and the load on the thermal head is large, as in the case of multicolor thermal transfer.

[Brief explanation of drawings]

1 and 2 are timing diagrams of applied pulses in one embodiment of the present invention, FIG. 3 is a flowchart showing a control method in one embodiment of the present invention, and FIGS. 4 and 5 are diagrams of other embodiments of the present invention. FIG. 6 is a flowchart showing a control method in another embodiment, FIG. 7 is a configuration diagram of main parts of a conventional thermal transfer recording apparatus, and FIG. 8 is a diagram showing a conventional control method. Flowchart showing,
9 and 10 are timing diagrams of applied pulses in the conventional method. DESCRIPTION OF SYMBOLS 1... Microprocessor circuit, 2... Ink sheet position detection circuit, 3... Ink donor sheet, 4...
・Thermal head. Agent Masuo Oiwa (and 2 others) Figure 1
Figure 2 Figure 3 Figure 7 Figure 8

Claims (2)

[Claims] (1) In a thermal transfer device that heats ink with a thermal head that operates based on applied pulses and transfers the ink to recording paper, the pause time of the applied pulse applied to the thermal head is increased in accordance with the rise in temperature of the thermal head. A thermal head control method characterized by: (2) In a thermal transfer device that heats ink with a thermal head that operates based on applied pulses and transfers the ink to recording paper, the above-mentioned application is applied to the thermal head in response to a rise in temperature of the thermal head and a rise in ambient temperature. A thermal head control method characterized by lengthening a pulse pause time.