JPS6273964A - System for driving thermal printing head - Google Patents

Abstract

PURPOSE:To prevent the generation of phenomena in which density irregularity is generated at the time of printing, power consumption is excessive in spite of uniform density and the life of a heat generating resistor element shortened, by applying energy to the heat generating resistor element so that no printing to recording paper is performed and preheating the element. CONSTITUTION:It is detected whether there is an L-level picture element signal for one line and, when there is the L-level picture element signal, the pulse width of a timing pulse is set to d1. When one line consists entirely H-level picture element signals, the pulse width of the timing pulse is set to d2 and two pulses are generated per one picture element and, further, the L-level picture element signal is outputted in place of the H-level picture element signal. Furthermore, the respective transistors 31 of block drivers 3a-3n are turned ON in all of said drivers. By this method, for one line performing no printing of the picture element signals, all of heat generating resistor elements 1 are heated by the melting pulse of the pulse width d2.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an improvement in a driving method for a thermal print head that can be applied to facsimile machines and the like.

[Technical background of the invention and its problems] Conventionally, in facsimile machines, etc., one line is printed by a thermal printing head with a length corresponding to the width of recording paper, and this is not repeated in the vertical direction sequentially. By doing so, printing is performed on recording paper pages. Such a thermal printing head is equipped with a plurality of heating resistor elements, and printing is performed by causing the heating resistor elements to generate heat in correspondence with pixels to be printed in each line.

By the way, if we consider printing on recording paper, the heating resistor element generates heat in each line where characters, figures, etc. are printed, but in the lines (white areas) where characters, figures, etc. are not printed, The heating resistor bundler cannot generate heat. Specifically, as shown in FIG. 6, when the print start signal S arrives, the print head drive unit prepares for printing, and prints one line of image signals @Pi, P2, . . . When the signal E arrives, the corresponding heating resistor element generates heat, and furthermore, when the printing end signal E arrives, printing ends.

However, according to such a conventional thermal printing head drive method, in front of one line of image signals P1 to P5, etc., the heating resistor elements either do not generate heat or do not generate heat for a long time. is empty and the temperature is lower than that of the thermal print head at other locations. For this reason,
The first line of printing, after the white image continued for a while, had the disadvantage that the other lines were printed in a lighter color than 'I3 (blue printing).

In order to cope with this, it is conceivable to increase the energy given to all the heat generating resistor elements and to make the color darker even in the printing of the first line opened above or the one line after the white image continues. However, not only does this method increase overall power consumption, but it also increases the overall power consumption, especially for ultra-high-speed printing (
For example, 1mS/1ine, 2ms/1ine)
If this is done, a considerable amount of heat is always stored in the heating resistor element, which has the disadvantage of shortening the life of the heating resistor element.

``Object of the Invention'' The present invention has been made in view of the drawbacks of the conventional heating '1i11 head drive method as described above. However, the power consumption does not increase that much, and
It is an object of the present invention to provide a driving method for a thermal printing head that does not shorten the life of a heating resistor element.

[Summary of the Invention] Therefore, in the present invention, when the thermal printing head is in a position where no printing is performed on the recording paper, energy is applied to the heating resistor element so that printing on the recording paper does not occur, and the heating resistor element is The above object is achieved by preheating the body element.

[Embodiment of the Invention] FIG. 1 shows a principle diagram of an embodiment of the present invention. In this embodiment, one line of image signal P1. Front position A1 of P5 etc. Although printing does not occur on recording paper such as A2, it is shown that energy can be applied to the extent that the heating resistor element is warmed to preheat it.

In order to adopt this J:Una drive system, a configuration as shown in FIG. 2 is used. In FIG. 2, 21 indicates a print control section. The print control section 21 receives a power supply from a power supply section 22 via a power line 23 and provides a predetermined control signal to the thermal printing head 25 via a control line 24 based on the image signal. The thermal printing head 25 receives power from the power supply section 22 via the power line 26, and
Heat is generated by a control signal given from the print control section 21. Therefore, the print control section 21 receives the print start signal S.
or when printing of one line of image signal is finished but the next one line of image signal is your own drawing (for example, after one line of image signal P4), it will be different from normal printing. A control signal is given to the thermal print head 25 in a different manner to heat the heating resistor element to the extent that printing does not occur on the recording paper. In other cases, for example, in FIG. 1, one line of image signal P2.
P3. P4. . . , P, etc., the printing control section 21 performs printing by applying a normal control signal.

More specific examples are shown below in FIGS. 3 to 5.

FIG. 3 shows a recording apparatus using a thermal printing head 2 constructed by arranging a large number of heating resistor elements 1 in a line. A large number of heating resistor elements 1 are grouped into one block every five adjacent elements, and constitute N blocks as a whole. One terminal of the heating resistor element 1 is grouped into blocks and connected to output terminals O of block drivers 3a to 3n provided corresponding to the blocks.

Further, the other terminal is connected to each heating resistor element arranged at the same position in each block via a backflow prevention diode 4, and connected to the corresponding bit driver 5a to 5e.

The block drivers 3a to 3n each include a head drive source that supplies current to the heating resistor element 1. This head drive source is
A switch 6 consisting of a meter contact and a diode 7 for preventing backflow are connected to the control input terminal C of the block drivers 3a to 3.
It operates when earth air is not being supplied through the block selection circuit 8 and when an H level block selection signal is being supplied to the input terminal (2) from the block selection circuit 8. Further, the bit drivers 5a to 5e operate according to the pixel signal supplied from the pixel register 9 while the timing pulse is supplied.

FIG. 1 shows the specific configuration of the block driver 3if5 and the bit driver 5. The block driver 3 turns on when the block selection signal output from the block selection circuit 8 (Fig. 3) is at TTL or DTL level and is 1'' (approximately 10 VCC pol I~), and is turned on when the block selection signal output from the block selection circuit 8 (Fig. 3) is 1'' (approximately 10 VCC pol I~). It is composed of a transistor 31 which is turned off at times, and transistors 32 and 33 which are Darlington connected and which perform a switching operation according to the state of the bit driver 5 only when the transistor 31 and the switch 6 are turned off.

Further, the bit driver 5 includes a NOR gate 41 that performs a NOR between the pixel signal output from the pixel signal register 9 and a timing pulse, and a transistor 42 that performs a switching operation based on the output of the NOR gate.

The output of the pixel signal register 9 becomes L level when recording is performed, and becomes H level when recording is not performed. Therefore, when a pixel signal of one level is output from the pixel signal register 9 when the head is energized, the output of the NOR gate 41 becomes T (level) and the transistor 42 is turned on.

Therefore, in this embodiment, whether or not there is an L level pixel signal for one line is detected (within the print control unit 21 in FIG. 2), and when there is an L level pixel signal, the pulse width of the timing pulse is Let be dl as shown in Fig. 5 (a>).

Further, when all one line has H level pixel signals, the pulse width of the evening timing pulse is set to d2, and
Two pulses are generated per pixel, and an L level signal is output as shown in FIG. 5(b) instead of an H level pixel signal. Further, each transistor 31 is turned on in the block drivers 38 to 3n. As a result, when printing one line without pixel signals,
All heating resistor elements] are heated by a timing pulse with a pulse width of d2 (assuming that no printing occurs on the recording paper at d2).

Note that whether or not there is an L level pixel signal in one line is determined by L.
A level signal counter counts before the pixel signal arrives at the pixel register 9. Then, when all the pixel signals for one line are at the H level, a fifth pixel signal at the L level is sent as the pixel signal by means not shown.
In addition to providing the timing pulse as shown in FIG.
A code for selecting all block drivers 3a to 3n is also given to C.

In this way, according to this embodiment, the heating resistor element 1 can be preheated by changing the width of the timing pulse.

Furthermore, as another method, the voltage of 10 V applied to the Darlington-connected transistor 32 may be made lower than that during printing. In this embodiment, all the heating resistor cords 1 are preheated, but it is necessary that the power required for preheating the main parts does not increase. j) However, if the power source is not large enough, preheating may be performed every block or every few blocks. Note that the recording paper may be of a heat-sensitive type, or the carbon may be of a heat-sensitive type (thermal transfer type).

[Effects of the Invention] As explained above, according to the present invention, when the thermal printing head is placed at a position where printing is not performed, it is preheated, so that printing at the next position after the position where printing is not performed is possible. However, unevenness in density does not occur. Furthermore, since the energy used during preheating is lower than that during printing, power consumption does not increase significantly and the life of the heating resistor element does not become short.

[Brief explanation of drawings]

FIG. 1 is a diagram for explaining the principle of an embodiment of the present invention.
Fig. 2 is a block diagram for explaining an embodiment of the present invention, Fig. 3 is a block diagram of main parts of a thermal printing device to which the present invention is applied, and Fig. 4 shows specific details of a block driver and a bit driver. 41 is a circuit diagram showing the circuit configuration, FIG. 5 is a diagram showing an embodiment for realizing the system of the present invention in the thermal printing apparatus shown in FIG. 3, and FIG. This is a diagram for

Claims (2)

[Claims] (1) In a method of driving a thermal print head that sequentially prints on a recording paper by generating heat in the heat generating resistor elements of a thermal print head including a plurality of heat generating resistor elements, the heat generating resistor elements are connected to the recording paper. A driving method for a thermal printing head, characterized in that the heating resistor element is preheated by applying energy such that printing does not occur on the heating resistor element. (2) When printing on recording paper, the heating resistor element is energized with a first pulse width to cause the heating resistor element to generate heat, and when the heating resistor element is preheated, the heating resistor element 2. The method of driving a thermal printing head according to claim 1, wherein energization is performed using a second pulse width narrower than the first pulse width.