JPH0379357A - Recorder - Google Patents

Abstract

PURPOSE:To enable printing irregularity and printing inferiority to be effectively canceled even through a thermal head and a platen roller are bent and a pressure contact force short position partially exists by a method wherein an applied pulse width to a heating element existing midway between a spring device and a spring device is set to be longer than the applied pulse width to the heating element near the spring device. CONSTITUTION:Pulse widths of strobes 1, 2, 7, 8 to be applied to two sets of heating blocks I, II, VII, VIII near both ends of a thermal head are set to be short, and pulse width of strobe signals 3 to 6 to be applied to heating blocks III to VI of a central part excepting those are set to be long. That is, the heating blocks, I, II, VII, and VIII at the head end part are structurally good in pressure contact with a platen roller. Besides, the heating blocks III to VI between spring pressing positions P1 and P2 are apt to be short in pressure contact force. Therefore, length of the pulse width to be applied is so adjusted that heating energy of the heating element is effectively transmitted to thermosensible paper or an ink film according to this pressure contact force. Thereby, printing density can be uniformed even for both a low pressure contact force position and a high pressure contact position.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention has a line-type thermal head and a platen roller to which the thermal head is pressed, and thermal paper or ink film and plain paper are conveyed between them. The present invention also relates to a recording device that performs printing using a thermal transfer method.

As shown in FIG. 5, a method of press-contacting a line-type thermal head to a platen roller, which has required a small amount of effort in the past, involves attaching a plurality of guide shafts 2.2 attached to the back surface of the thermal head 1 to the main body 3 of the apparatus. A method is adopted in which the thermal head 1 is slidably inserted and pressed against the platen roller 5 by the elastic force of springs 4, 4 which are fitted onto the respective guide rods 2, 2. Generally, two guide rods 2 and springs 4 are used as shown in the figure, but three may be used.

According to the above structure, the platen roller 5 is supported at both ends, and the thermal head 1 is supported by the spring 4.
4, the thermal head 1 and platen 5 are bent as shown in FIG. 6, which is slightly exaggerated. The thermal head portion 1a will not be pressed sufficiently against the platen roller, and the pressing force will be concentrated on the portion 1b immediately below the spring, resulting in excessive pressure. If printing is performed in this state, there will be problems such as the print density being too light or printing blurring in areas where there is insufficient pressure contact, and the print density being too dark in areas where there is excessive pressure contact.

One solution to this problem is to increase the number of springs that press the thermal head, but this would make it extremely difficult to adjust the balance of pressure between the springs and increase the number of springs, resulting in high costs. Furthermore, even if the number of springs is increased, the platen roller cannot be prevented from bending, so it is not possible to completely eliminate printing defects and density unevenness.

In view of these points, the present invention provides a useful record that can effectively eliminate printing unevenness and printing defects even if the thermal head and platen roller are curved as described above and there are parts where the pressure contact force is insufficient. The purpose is to provide equipment.

In order to achieve the above-mentioned object, the present invention provides a recording device that prints by pressing a line-type thermal head in which heating elements are arranged in a line against a platen roller by two or more bullets. The pulse width applied to the heating element located between the aircraft and the aircraft is set to be longer than the pulse width applied to the heating element near the aircraft.

In a thermal type recording device or a thermal transfer type recording device, the print density is proportional to the applied pulse width. However, this applies when the pressure contact state between the thermal head and the platen roller is constant, and if the pressure contact force is weak, the print density will not become much higher even if the applied pulse width is increased. Therefore, as in the present invention, the pulse widths applied to the heating element at the contact point of the bullet that presses the thermal head against the platen and the heating element located at a location between the bullets are adjusted to lengthen or shorten. By doing so, it becomes possible to make the print density uniform in both areas where the pressing force is low and where the pressure is high.

1 shows a thermal head 1 used in the recording apparatus of the present invention. Heating elements 121 to 12. . For example, 2048 4Is are arranged. One end of each heating element 12+... is connected to the common electrode 13, and the other end is connected to the IC driver circuit 14... Total heating element IL~12□. 4 is divided into eight heat generating blocks (1) to (4) in this embodiment, and each block is driven in turn.

The drive of each heat generating block is selected by a strobe signal, which signal is shown by a solid line in FIG. According to this figure, the strobe signal ■■■■ applied to the two sets of heat generating blocks ■■, ■■ near both ends of the thermal head has a short pulse width, and the strobe signal applied to the other heat generating blocks ■～■ in the center part Signals ■ to ■ are set to have long pulse widths.

The pulse width of the strobe pulse determines the energization time of the heating element, in other words, the heat generation energy.The reason why the pulse width of the strobe signal is made different for each block as shown in FIG. 2 is as follows. The position where the thermal head is pressed against the platen roller by the spring is determined by Pt in the longitudinal direction of the head, as shown in Figure 1.
Assume that the position is Pi. Since this position corresponds to the second heat generating blocks (2) and (2) from the end of the head, these two heat generating blocks (2) are in good pressure contact with the platen roller. Also, the heat generating block at the end of the head■,■
Since the platen roller has a structure in which both ends are supported as explained in the prior art section, the pressure contact with the platen roller is good.

On the other hand, the pressing force of the spring acts only indirectly on the heat-generating blocks ■ to ■ located between the spring pressing positions P+ Pg, and since they face the center of the platen roller, the pressing force with the platen roller is insufficient. I tend to do that. Therefore, the second heating block I, If from each end of the thermal head.

Even if the pulse width of the strobe signals applied to (2) and (4) is shortened, the pressure contact force with the platen roller is high, so the heat generated energy of the heating element is effectively transmitted to the thermal paper or ink film, and clear printing is possible. -The remaining heat generating block■
Unless the strobe signal applied to ~■ increases the heat generation energy by increasing the pulse width, the heat generation energy will not be effectively transmitted to the thermal paper or ink film due to the weak pressure contact force. For the above reasons, the pulse width of the strobe signal ■■■■ applied to the heat generating blocks I, n, ■, ■ on both sides of the thermal head is shortened, and the pulse width of the strobe signal ■■■■ is applied to the heat generating blocks I, n, ■, ■ on both sides of the thermal head.
The pulse width of the strobe signal applied to ~■ was increased.

However, the pulse width of the strobe signal applied to the heat generating blocks (1) to (4) is changed depending on the difference in the pressing force between each heat generating block and the platen roller. Note that the strobe signal indicated by the broken line in FIG. 2 is a pulse at equal intervals used in a conventional thermal printer.

FIG. 3 shows a circuit for generating strobe signals ① to ① shown in solid lines in FIG. This circuit uses eight preset counters 01-C8.

The first preset counter C1 starts counting clock pulses when a print command is input from a control unit (not shown), and the second preset counter C2 starts counting clock pulses when a carry signal is input from the first preset counter C1. Start. Hereinafter, the n-th (where n is an integer smaller than 8) preset counter Cn is the n-th preset counter Cn.
The first preset counter C9-1 starts counting clock pulses by inputting the carry signal.

A pulse is output to the output lines a to h of each of the preset counters 01 to C8, which changes to the H level when counting starts, and changes to the L level when the count value matches the preset value. Then, the preset value of each counter is set to a desired value, and thereby the strobe signal ■ is sent from the output line a of the first preset counter C1, the strobe signal ■ is sent from the output line of the second preset counter C2, and the strobe signal strobe signal from output line C of preset counter C3.
, a strobe signal ■ from the output line d of the fourth preset counter C4, a strobe signal ■ from the output line e of the fifth preset counter C5, a strobe signal ■ from the output line f of the sixth preset counter C6, A strobe signal (2) is obtained from the output line g of the seventh preset counter C7, and a strobe signal (2) is obtained from the output line gh of the eighth preset counter C8. Note that the carry signal of the eighth preset counter C8 is sent to the control section as a print end signal.

FIG. 4 shows a thermal head drive circuit.

Image data for one line to be printed next is input to the shift register 21 through a control section (not shown). The line buffer 12 holds one line of image data transferred from the shift register 21 and currently to be printed. Both the shift register 21 and the line buffer 22 have 2048 output lines, which is equal to the number of heating elements of the thermal head 1. Each output line of the line buffer is an AND circuit A1
= Connected to the input side of A z @l. The AND circuits A and ~Azoatr are divided into 8 groups of 256 circuits each, and each group receives strobe signals
is added as a gate signal. The output line of AND circuit A+”Az.1 is the heating element 21~22°4
8 and the IC driver 4 inserted between the drive power supply element B.
~4□. It is connected to 4°.

Next, to explain the operation of printing one line using the circuit shown in Fig. 3.4, first, when printing of one preceding line is completed, a print end signal is issued from the counter C8 of the strobe generating circuit shown in Fig. 3 to the control section. Upon receiving this, the control section inputs the image data of one line ahead to the shift register 21. At this time, the line data held by the shift register 21 until then is transferred to the line buffer 22. At the same time, a print command is sent from the control unit to the first preset counter CI.
is input to start strobe signal creation. When the strobe signal ■ is generated, the AND circuit A of the first group
1~AzH opens the gate, then line buffer 2
The first 1/8 of the 1 line data stored in 2
The data (256 dots) are the AND circuits A1 to A,
, and are added to the IC drivers 41 to 4□. Here, since the image data is binary data of 0 or 1, the IC driver to which the data of O is applied is not conductive, but the IC driver to which the data of 1 is applied is conductive. When the IC driver becomes conductive, a driving power supply voltage is applied to the heating element connected to it, and the heating element generates heat. This heat generation continues until the pulse of the strobe signal ■ falls. At the same time as the strobe signal ■ falls, the strobe signal ■ is generated, and this time, the AND circuit A23. of the second group ■ is generated. ~A, 1. opens the gate. Therefore, of the line data stored in the line buffer 12, the next 1/
8 data passes through AND circuit A□F~ASI□ to IC
Driver 4! S,~4,1! , and controls the heat generation of the heat generating element of the second heat generating block (2) based on the image data.

Hereafter, each time the strobe signals ■, ■, ■, etc. are issued, the group of AND circuits that open the gates changes, and as a result, the line data stored in the line buffer is
8 are outputted at a time, and the heat generation of the heating element is controlled in units of one heat generating block. Then, the strobe signal ■ is emitted, the last 1/8 of the line data is output, and the heating block ■
When the heat generation control of the heating element is finished, the platen roller
It rotates by a line and conveys the recording paper (thermal paper or ink film and plain paper) in the sub-scanning direction. Thereafter, the same operation is repeated again to print one line at a time.

In this printing operation, the strobe signal is
As shown in (2), since the pulse widths are different, the heating time of the thermal head is different for each heat generating block. As described above, this difference is related to the pressing force with the platen roller, so a clear image with uniform density can be printed regardless of the magnitude of the pressing force.

In the above embodiment, the springs of the thermal head press at two locations, but it is of course possible to apply pressure to three or more locations.

Further, although the thermal head is divided into eight heat generating blocks and driven, it is also possible to drive the thermal head divided into four or any other number of heat generating blocks.

As explained above, according to the present invention, due to the mechanism for pressing the thermal head against the platen roller, even if the pressing force between the two is not uniform over the entire length g, it is possible to press the thermal head against the heating element. Since the heat generation energy of the printer is adjusted accordingly, printing can be performed with uniform density and clarity, and printing quality can be greatly improved.

[Brief explanation of drawings]

FIG. 1 is a plan view of a thermal head to which the present invention is applied;
Figure 2 is a waveform diagram showing the strobe signal, Figure 3 is the strobe signal generation circuit, Figure 4 is the thermal head drive circuit, Figure 5 is the thermal head and its surroundings, and Figure 6 is the conventional It is a figure explaining the problem of. 1... Thermal Herado, 12. ~12□. 4. ...
Heating element, ■～■... Strobe signal.

Claims (1)

[Claims] (1) In a recording device that prints by pressing a line-type thermal head in which heating elements are arranged in a line against a platen roller by two or more bullets, the heating element located between the bullets is A recording device characterized in that an applied pulse width is set longer than an applied pulse width to a heating element near a bullet.