JP2708285B2 - Drive control device for thermal head - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive control device for a thermal head, and more particularly to a device for generating a control signal for driving a heating element.

[0002]

2. Description of the Related Art A thermal head has a plurality of heating elements corresponding to print dots arranged side by side. By selectively energizing each heating element of the arranged heating element group based on print data. Printing is performed directly on thermal paper or via an ink ribbon. In this type of thermal head, when the printing speed is increased, the next energization is started before the temperature of the heating element does not decrease, so that there is a problem that the surface temperature of the thermal head increases and printing unevenness occurs. Further, when the heat storage temperature of the head increases, cracks and bubbles are generated in the head due to thermal stress, and there is a problem that the life of the head is shortened. Therefore, conventionally, the past heat history of each heating element is detected to control the energization time to the heating element.

FIG. 5 shows an example of a conventional drive control device. In a shift register 1 in which print data is stored based on a clock signal, gate circuits 3a to 3n are provided via a latch circuit 2. Connected to the gate circuits 3a to 3d.
A plurality of heating elements 4 corresponding to print dots are connected to 3n. According to this circuit, the print data sequentially stored in the cyst register 1 is output to the gate circuit 3 as the previous print data after being held by the latch circuit 2, and is directly output from the cyst register 1. The current print data is output to the gate circuit 3. Therefore, the gate circuits 3a to 3n form a print control signal to the heating element 4 based on the current print data, the previous print data, and the gate signal. For example, if the print data is “Hi” (printing state) not only this time but also the previous time, the pulse is shorter than when this time is “Hi” and the previous time is “Low” (blank state). It becomes a control signal. As a result, the heating element 4 is given an appropriate energizing time in consideration of the past heat generation state, and good printing can be performed. Note that in the above case, the history of the last two times can also be considered.

[0004]

However, in the conventional thermal head drive control device, as shown in FIG. 6, when a half-staggered half-pattern printing or the like is performed, blank portions are blurred and collapsed. There is a problem that a high quality printing state cannot be obtained sufficiently. Therefore, when controlling the driving of each heating element, it is necessary to take into account not only the history information of the printing element at the previous and two previous times but also printing data adjacent to the element. In this case, the control is not complicated, and it is required to perform efficient history control with a simple circuit configuration.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and a first aspect of the present invention is to provide a thermal head drive control device capable of performing high-quality printing of staggered half patterns. Secondly, it is possible to obtain history information up to two times before the adjacent heating element with a simple circuit configuration, and thirdly, with a simple circuit configuration, the history processing performed based on the information of the adjacent heating element can be performed. It is intended to be performed in a short time.

[0006]

To achieve the above object of the Invention The present invention provides a drive control apparatus for a thermal head driving control based on a plurality of heating elements which are arranged in the printing information, the drive to the heater element Store current print information of group
A first shift register, and a previous shift register of the heating element group.
A second shift register for storing history print information;
A third shift for storing history print information of the thermal element group two times before
And the first, second and third shift registers
History print information of the heating element to be processed,
Print information and history print information of the heating element adjacent to the heating element
Is entered and the history of the heating element is
A history processing unit that performs processing, wherein the history processing unit includes:
The logic of the previous and two previous history print information of the adjacent heating element
The sum is processed as history print information of adjacent heating elements .

[0007]

[0008]

[0009]

According to the present invention , the history processing is performed based on not only the history print information of the heating element but also the print information of the adjacent heating element and the history print information. The drive control signal can be formed in consideration of the print history of the range. That is, as shown in FIG. 7, when drive control is performed on the heating element of the print dot DA, the print dots DD and DG
Not only the history print information but also the adjacent print dots DB,
DC print information and print dots DE, DF, DH, DI
In consideration of the history print information of the adjacent portion of
By controlling the drive voltage and drive time of the heating element,
It is possible to obtain print dots having an appropriate density.

Further, the printing information sequentially supplied corresponding to the heating element group which are juxtaposed is first stored in the first shift register, then to the second shift register, and the third shift register The first shift register stores the current print information, the second shift register stores the previous history print information, and the third shift register stores the previous print information. Will be stored. Then, the print information of the heating element to be subjected to the history processing and the print information of the adjacent heating element are sent to the history processing unit from the second shift register, and the heating element and the adjacent heating element are sent from the second shift register. And the third register sends the history printing information of the last two times before the heating element and the adjacent heating element. Therefore,
Much information necessary for history processing is extracted with a simple configuration without using a latch circuit or the like.

Then, the print information of the adjacent heating element obtained by the above configuration and the history print information of the heating element and the adjacent heating element at the previous and two previous times are collectively determined and subjected to the history processing. The history processing can be easily performed with the circuit omitted. That is, as shown in FIG. 7 described above, when all the print information and the history print information other than the heat generating element are considered, there are eight dot bits to be considered. In this case, the circuit configuration becomes very complicated, and the transfer of control data in a short time is practically impossible. Therefore,
In the present invention, by performing the collective processing, complicated control can be simplified.

[0012]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows a basic configuration of a drive control circuit for a thermal head according to an embodiment.
A first shift register 14 for storing current print data is connected to a shift register 10 for storing print data on the user area side via a selector 12, and the first shift register 14 is connected to the first shift register 14 via a selector 16. A second shift register 18 for storing the previous print data is connected, and a third shift register 22 for storing the print data two times before is connected via the selector 20 to the second shift register 18. Then, each shift register 1
At 4, 16, and 22, the stored print data is connected via each of the selectors 12, 16, and 20 so as to rotate sequentially in the shift register. Further, a level setting unit 24 for starting and inputting a printing process is provided, and a history processing unit 26 is connected to the level setting unit 24. In the history processing unit 26, predetermined positions of the first shift register 14, the second shift register 18, and the third shift register 22,
In this embodiment, the print data A, B, C, D, E, F, G,
H and I are output. FIG. 2 shows the interrelationship of the data for performing the history processing. Considering the case similar to FIG. 7 described above, the data of the heating element (print dot) which is the current processing target is represented by A. Then, the print data of the adjacent heating elements becomes B and C, the previous history print data of these three heating elements becomes D, E, F, and the history print data of the last two times becomes G, H, I. Therefore, in this case, the data B to H are used to determine the print information of the A data, and these information are stored in the shift register 1.
The history processing of all the heating elements can be performed by being sequentially converted by the movement of 4, 18, and 22.

FIG. 3 shows a specific circuit configuration in the history processing unit 26. In FIG.
To SI indicate storage cells of the shift registers 14, 18, and 22 corresponding to the print data of the heating elements shown in FIG. Then, the outputs of both the storage cells SD and SG become history dot data as they are. Further, an OR circuit 32 for ORing the outputs of both the memory cells SF and SI and an OR circuit 33 for ORing the outputs of both the memory cells SE and SH are provided. The output of the OR circuit 32 is an AND circuit. 34, while the output of the OR circuit 33 is
Output to An on / off signal for switching the control state between low-speed printing and high-speed printing is supplied to the AND circuits 34 and 35, and the logical product of the on / off signal and the outputs of the OR circuits 32 and 33 is provided. It is configured to take. Further, there are provided an OR circuit 36 for calculating the logical sum of the output of the memory cell SC and the output of the AND circuit 34, and an OR circuit 37 for calculating the logical sum of the output of the memory cell SB and the output of the AND circuit 35. , These OR circuits 3
The adjacent dot data is output from 6, 37.

The embodiment has the above configuration, and its operation will be described below. In FIG. 1, when the power is first turned on and a reset signal is input, the first shift register 14, the second shift register 18, and the third shift register 22 are cleared, and the shift register 10 in the user area is cleared. Is input by the user with print data. When there is a load input, the print data is transferred from the shift register 10 in the user area to the selector 12 (101).
The print data moves to the first shift register 14 via (→→ 102), moves from the first shift register 14 to the second shift register 18 via the selector 16 (104 → 106), and The shift register 18 sequentially moves to the third shift register 22 via the selector 20 (108 → 110). Therefore, the current print data and the second shift register 1 are stored in the first shift register 14.
8 stores the previous print data, and the third shift register 22 stores the print data two times before.

Next, when the first start input is input to the level setter 24, the level setter 24 is set to level 1 and the first, second and third shift registers 14, 1 are set.
Data in 8, 22 are 103 → 105, 107 → 10
At the same time, the print data A to I are supplied to the history processing unit 26 while moving while rotating in the direction of 9, 111 → 112.

Then, the OR circuits 32 and 33 of FIG.
In the above, the logical sum of the print data of the previous heating element and the previous two-time printing data of the adjacent heating elements is calculated, and the outputs of the storage cells SG and SD are output as they are as the history dot data. On the other hand, OR circuit 3
The output of 2 is an AND circuit 34, and the output of the OR circuit 33 is ANDed with an on / off signal for determining whether or not to perform history processing in the AND circuit 35. At this time, when high-speed printing is performed, since the ON signal (Hi) is output to the AND circuits 34 and 35, the OR circuits 32 and 3 are output.
When the output of No. 3 is “Hi”, the outputs of the AND circuits 34 and 35 become “Hi”. Next, the outputs of the ANDs 34 and 35 are ORed with the print data of the adjacent heating elements in OR circuits 36 and 37, and the adjacent dot data is output from the OR circuits 36 and 37. Therefore, as for the history information of the heating element, the "Hi" and "LOW" are output as the history dot data as they are, and the OR circuits 36 and 37 output the printing data of the adjacent heating element and the three printing data of the history printing data. If at least one of the data is "Hi", "H"
The adjacent dot data of "i" is output. In this way, when the level 1 history processing is completed, a start signal of the next level is output, and levels 2 to 6 are sequentially raised by the level setting unit 24, and the history processing unit 26 performs the same processing as described above. Output history data together with the clock signal.

As described above, the history information and the 4-bit output of the OR circuits 36 and 37 output the print data of the heat-generating element, the history information of the previous element and the previous two times, and the print information and history of the adjacent heat-generating element. A signal for controlling the applied energy of the heating element is formed with reference to the information. For example, as shown in FIG. 4, the types of driving pulses can be divided into six levels and formed.
When A to F are set to a predetermined time, when the history dot data and the adjacent dot data are “Low”, a drive pulse having the maximum length (A to F) shown in level 1 is formed. Is "Hi" (heat generation state), a drive pulse determined by BF is formed as in level 2. The level 3 is obtained by subtracting the B time when the dot data of the last two times of the heating element is “Hi”, and the level of C to 3 is obtained.
A drive pulse consisting of the F time, level 4 is a drive pulse consisting of the D to F time when the dot data and the adjacent dot data are “Hi”, and a level 5 is a case where the previous dot data is “Hi”. The drive pulse composed of the E and F times, and the level 6 indicates that the previous dot data and the adjacent dot data are “H”.
In the case of "i" or the like, the driving pulse is composed of the F time, and the above-described driving pulse is formed and given to the heating element according to the heat generation state of the element other than the heating element.

The history information of the adjacent heating elements is not considered when the previous adjacent dot data is "Hi" during low-speed printing (off state), for example, as shown at level 3. However, as shown in level 4, when the previous adjacent dot data is “Hi” during high-speed printing (ON state), a short drive pulse of DF time, which is obtained by subtracting C time, is formed. Will be.

According to the history processing section 26 composed of the logic circuit shown in FIG. 4, high-speed operation can be performed and history processing can be performed at a speed of several nsec / bit, and the history information of adjacent heating elements is taken into consideration. Therefore, even in high-speed printing, high-quality printing can be performed by performing the narrowing-down drive control. The print data used for the history processing is rotated by the shift registers 14, 18, and 22, and the history processing unit 26 serially performs the history processing in synchronization with the rotation of the data. be able to. That is, when the above-described history processing is performed by applying the circuit shown in FIG. 5, many gate circuits must be combined, which not only complicates the configuration but also forms the IC circuit. As the chip size increases, the cost increases.

When the thermal head is used for low-speed printing, an off signal is applied to the other ends of the inputs of the AND circuits 34 and 35. Therefore, the OR circuits 32, 3
3 are blocked by AND circuits 34 and 35, and only the print data of the adjacent heating elements are output from the OR circuits 36 and 37. In this case, the control of the energy applied to the heating elements is performed by controlling the print data of the adjacent heating elements. This is performed based on the history print information of the heating element, and simple print control can be performed.

In the above embodiment, as shown in FIG.
The print information and history print information of the adjacent heating elements on the left and right
Although the two pieces of information are considered together, the print information of the adjacent heating element and the history print information of the adjacent heating element may be separately extracted and subjected to the history processing. Further, the history print information of the adjacent heating elements takes into account the information of the previous time and the information before the previous time, but it is also possible to perform the history processing only with the information of the previous time.

[0022]

As described above, according to the present invention,
In a drive control device for a thermal head that drives and controls a plurality of heating elements arranged side by side based on print information, not only the history print information of the above-described heating elements, but also the print information of an adjacent heating element and the history print information of the previous and two previous times. Therefore, high-quality printing can be performed even for the printing of the staggered half pattern.

Further, according to the present invention, the first shift register for storing the current print information of the group of driven heating elements and the second shift register for storing the previous history print information of the group of heated elements are provided. A third shift register for storing the history print information of the heating element group two times before, a history print information of the heating element to be processed, and a mark of the adjacent heating element from the first, second, and third shift registers. A history processing unit for inputting character information and history print information and performing a history process;
Is provided, print information up to two times before the adjacent heating element can be obtained quickly and easily with a simple circuit configuration.

[0024] Then, according to the present invention, in the history processing section. Thus to process a logical sum of Printout information last two of the adjacent heat-generating elements as the history information of the adjacent heating elements, the adjacent heating elements The history processing performed based on this information can be performed with a simple circuit configuration and in a short time.

[Brief description of the drawings]

FIG. 1 is a circuit block diagram illustrating a drive control circuit of a thermal head according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing print data necessary for history processing in the embodiment.

FIG. 3 is a circuit diagram illustrating an internal configuration of a history processing unit according to the embodiment.

FIG. 4 is an explanatory diagram showing an example of a drive pulse formed in the embodiment.

FIG. 5 is a circuit block diagram illustrating an example of a drive control circuit for a conventional thermal head.

FIG. 6 is a diagram illustrating a print example of a hound's tooth half pattern.

FIG. 7 is a diagram illustrating print dots that are considered in the history processing.

[Explanation of symbols]

 1,10 shift register 4 heating element 12,16,20 selector 14 first shift register 18 second shift register 22 third shift register 24 level setter 26 history processing unit SA to SI storage cell 32,33,36 , 37 OR circuit 34, 35 AND circuit

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-61-143153 (JP, A) JP-A-63-319163 (JP, A) JP-A-63-207663 (JP, A) JP-A-63-63 278870 (JP, A)

Claims (1)

(57) [Claims] A drive control device for a thermal head for driving and controlling a plurality of heating elements arranged in parallel based on printing information stores current printing information of a group of heating elements to be driven.
A first shift register, and a previous shift register of the heating element group.
A second shift register for storing history print information;
A third shift for storing history print information of the thermal element group two times before
And the first, second and third shift registers
History print information of the heating element to be processed,
Print information and history print information of the heating element adjacent to the heating element
Is entered and the history of the heating element is
A history processing unit that performs a process, wherein the history processing unit performs the previous and next previous times of the adjacent heating element.
The logical sum of the history print information is added to the history print information of the adjacent heating elements.
Drive control apparatus for a thermal head, which comprises the processing.