JPS6367162A - Driving method of line type thermal head - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for driving a line-type thermal head, and more particularly to a method for driving a thermal head suitable for extending the life of the thermal head.

[Conventional technology]

In printing devices that use conventional line-type thermal heads (hereinafter simply referred to as "thermal heads"), data for one line is stored in multiple small blocks (hereinafter referred to as "strobes") determined by the thermal head. ). Based on that data, when firing the corresponding heating resistor, one line is fired by simultaneously firing two to four strobes out of the four to eight strobes divided above. In order to print, a method was used in which the printing was divided into multiple fire groups.

This means that if you fire all the dots for one line at the same time,
This method has been adopted because the amount of heat generated and power consumption thereby becomes extremely large, making it difficult to obtain a predetermined print quality, and increasing the power supply capacity, leading to high costs.

This will be explained in more detail below.

For example, an A4-width thermal head has 1,728 resistors even if the resistor density is 8 resistors/mm, so at maximum, that is, all drivers 1-fire,
When drawing a horizontal line, the power consumption of one resistor is approximately 0.
．． 7mW x 1. ．． 728=1,200W.

In addition, the current peak value is 60A, which is the power supply capacity.

Not only does the amount of heat generated become enormous, but the resulting drop in power supply voltage results in a shortage of printing energy.

Therefore, the simultaneous firegroup of these resistors should be 2 to 4.
By dividing the printer into groups and printing at slightly different times, it is possible to reduce power consumption 9 and reduce the amount of heat generated.

For example, in the above example, if the resistors are divided into four groups and fired, the power consumption and current peak values will be 1/4, 300 mW and 15 A, respectively.

Note that related devices of this type include, for example,
A device disclosed in Japanese Unexamined Patent Publication No. 59-54580 is known.

[Problem that the invention seeks to solve]

Although the above-mentioned conventional technology has a certain effect on reducing power consumption and heat generation, the upper limit of the number of simultaneous fire groups is determined by the relationship between printing speed and fire pulse width.

That is, as shown in FIG.
is less than or equal to Nmax in the following equation at most.

In general, T = 4-5 +++s, τ = 0.8-1
There are many ms thermal heads, and the above Nmax is 4 to 6.

In the example shown in FIG. 4, the number of strobes is 8. An example in which the number of simultaneous fires is 4 has been shown, but when the correspondence between simultaneous fire groups and strobes is fixed in this way, the following problems arise.

That is, in the example shown in FIG. 4, for each strobe -1,
There are many dots of 1-2, and the lobe l-3,1 to s1
Even if there are almost no -4 dots, the pulse widths of simultaneous firegroups A and B are the same. Therefore, the power supply voltage drop amount of A is larger than that of B, and the density of A is lower than that of B, resulting in shading. Here, as mentioned above, since there is an upper limit on the number of simultaneous fire groups, the number of heating resistors that one fire group can handle in Fig. 4 is 43.
2 dots, and the maximum voltage drop amount at this time (4
The difference between the minimum voltage drop amount (when printing 32 dots) and the minimum voltage drop amount (when printing only 1 dot) directly becomes the difference in input power and causes printing shading.

Further, in this example, the current value in each fire group is the maximum value in A, while it is almost O in B, so that there will be groups in which the peak current value is extremely large.

The present invention has been made in view of the above circumstances, and its purpose is to solve the above-mentioned problems in conventional thermal head drive methods, and to provide a thermal head capable of suppressing the amount of heat generated and the peak current value. The objective is to provide a drive system for this purpose.

[Means for solving problems]

The above-mentioned object of the present invention is to provide a line-type thermal printer that selectively drives a plurality of resistors of a thermal head to form character figures, in which a plurality of print data blocks of a thermal head are divided in advance. A means for counting the number of resistors and a fire timing control means for each block of the divided thermal head are provided, and a block with the largest number of fire resistors, a block with the smallest number, and a block with the second largest number are provided. This is achieved by a line-type thermal head drive system characterized by simultaneously firing every combined block, such as the second least number of blocks, etc.

[Operation] In the present invention, the number of data for each strobe is counted when stored in the shift register, and based on the result, a simultaneous fire group is determined each time, and the heating resistor to be fired in each fire group is determined. This is to combine them so that the number of bodies is averaged.

In other words, the number of data for each strobe is ranked n□
, n2. ..., n, (in the case of 8 strobes), then every strobe firing simultaneously is 02 and n? 1. The power of each fire group is determined by simultaneously firing those with a large number of data and those with a small number of data, such as n3 and n, , n4 and 05.

It averages out voltage drops.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 2 is a configuration diagram of a thermal head drive section showing an embodiment of the present invention. In the figure, 7 is a thermal head, and a line buffer 1.7 for capturing one line of print data. A shift register 42 for storing the data, a clock pulse signal input (CP) 5 for synchronizing the fire timing of the heat generating resistor, data latching timing, etc., a thermistor terminal 6, and a heat generating resistor (not shown). It consists of a driver for the fire. Further, 2 indicates a counter, which will be described later, and 3 indicates a thermal head control section.

1. In the line buffer 1, one line is divided into a plurality of strobes 1-1 to 1-n (here, n=8). Before the print data is taken into the buffer, the counter 2 counts the number of dots to be printed on each of the blocks 1 to 1. According to this count result, the thermal head control section 3 determines the firing timing of each of the strobes 1-1 to 1-8 as follows.

FIG. 1 is a flowchart of the fire timing determination process of the thermal head control section 3, and FIG. 3 is a diagram showing an example of the relationship between the count result by the counter 2 and the fire timing.

In the following explanation, the number of dots of each strobe 1-1 to 1-8 is n1 to nl1 (however, n□〉n2〉...)
n 7 > n s).

The thermal head control unit 3 controls each step 1 to 1 by the counter 2.
Step 1: Enter the result of counting the number of dots on the lobe.
1) Sort this in ascending or descending order (step)
2). Next, for the count results that have been sorted, 1. from the beginning and end. Take them one by one and combine them in sequence (step 13).

This creates a fire group E- as shown in FIG.
H is formed. After this, each fire group E-
A tarok pulse is applied to sequentially fire H (step 14).

That is, in the above process, a pulse is first sent so as to simultaneously fire the strobe 1-2 with the largest number of data and the strobe 1-6 with the smallest number of data, and then the second Strobes 1-1 and 2 with many
A pulse is sent so that strobes 1 to 5 having the smallest number of data fire simultaneously. Thereafter, those with a large number of data and those with a small number of data are combined and driven in the same manner to sequentially fire four blocks.

As a result, the number of heat-generating resistors that fire simultaneously is averaged, and the heat-generating resistors that are fired at the same time are not concentrated in a specific fire group, so the peak current value can be suppressed, and the amount of heat generated by the thermal head 7 can also be made smaller.

When using the conventional fire method shown in FIG. 4, the count result as shown in FIG. 3 is =8− as shown in FIG. 5, fire group A has a very large number of fire resistors, Fire group A becomes very low and unbalanced, resulting in a very high peak current in fire group A.

According to the above embodiment, since the data of one line of drive 1 can be counted in advance and the groups to be fired simultaneously can be determined accordingly, the peak current during printing can be suppressed and the amount of heat generated can be reduced. The following effects can be obtained.

(1) Even with the same printing duty (number of fire resistors), the temperature rise of the thermal head can be reduced, so the life of the head can be extended.

(2) Generally, when the temperature of the thermal head exceeds a certain level, it is necessary to stop printing to protect the head.
Since the upper limit printing duty is higher than in (1) above, continuous high-duty printing becomes possible.

(3) Since the peak current is small, the power supply can be made smaller or the cost can be reduced.

(4) Since the amount of drop in the power supply voltage is smoothed out, printing shading is reduced and printing quality can be improved.

In the above embodiment, the counter 2 has a count of 1
Although an example has been shown in which the fire timing of each of the strobes 1-1 to 1-8 is determined by software by the thermal head control unit 3 according to the result, this can be done by a combination of hardware. is also possible.

〔Effect of the invention〕

As described above, according to the present invention, in a line type thermal printer that selectively drives a plurality of resistors of a thermal head to form character figures, a plurality of print data blocks of a thermal head are divided in advance. means for counting the number of fire resistors in each block, and fire timing control means for each block of the divided thermal head; By simultaneously firing each combination of blocks, such as the largest block and the second smallest block, it is possible to realize a thermal head drive method that can suppress the amount of heat generated and the peak current value. This has the following effects.

[Brief explanation of drawings]

FIG. 1 is a flowchart of fire timing determination processing of a thermal head control section showing one embodiment of the present invention;
The figure is a block diagram of a thermal head drive section showing an embodiment of the present invention, FIG. 3 is a diagram showing an example of the relationship between the count result by the counter 2 and the fire timing, and FIG. 4 is a diagram showing a conventional thermal head drive system. FIG. 5, which is a diagram showing a fire timing determination method, is an explanatory diagram comparing the conventional technology and the embodiment of the present invention. 1 line buffer 1.2: Counter, 3: Thermal head control section, 4: Shift register, 5: Clock pulse signal input, 6: Thermistor terminal, 7: Thermal head. T process 1 line printing time 5th Conventional technology C

Claims (1)

[Claims] 1. In a line-type thermal printer that selectively drives multiple resistors of a line-type thermal head to form character figures, the number of fire resistors in multiple print data blocks of the thermal head that are divided in advance is determined. Counting means and fire timing control means for each block of the divided thermal head are provided, and the block having the largest number of fire resistors, the block with the least number, the block with the second largest number, and the second smallest number are provided. block,·
A line-type thermal head drive system characterized by simultaneous firing of each combined block as shown in...