JPS6321156A - Printing control system in thermal printer - Google Patents

Abstract

PURPOSE:To uniform a printing density and to enable a high-speed printing, by a method wherein the conduction to heating elements is commanded by a heat hysteresis pulse for every heating element and the conduction to the respective heating elements is commanded on the basis of a printing pulse signal which was chipped by a chipping pulse. CONSTITUTION:A first control means 1A forms a heat hysteresis pulse signal having a time width proportional to a time elapsed from the last black dot printing in the printing data range up to 3 (=n) preceding dots for every heating elements H1, H2,...H24. The printer functions so that the heating elements H1, H2,...H24 are respectively heated by this heat hysteresis pulse signal to uniform substantially temperatures at the start of heating in printing. A second control means 1B forms a chopping pulse having a duty ratio inversely proportional to a black dot printing ratio in a total heating element portion H in the printing range of at least 106 (=m) preceding dots. The printer functions so that heating elements H1, H2,...H24 are heated for printing on the basis of a printing pulse signal chopped by this chopping pulse.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a printing control method for a thermal printer, and particularly to a printing control method for a thermal printer that controls the heat generation temperature of a heating element for printing according to various conditions. Regarding the method.

[Conventional technology]

It is generally known that the print density of dots in a thermal printer changes depending on various thermal conditions, such as being proportional to the peak temperature of a heating element when the environmental temperature is constant. This is because the ink on the ink ribbon melts differently depending on the temperature of the heating element. The main thermal conditions in this case are environmental temperature, temperature changes in the thermal head and the printer itself due to continuous energization, and heat accumulation in a heating element that has generated heat in the relatively recent past.

Therefore, in order to keep the print density constant, various methods have been conventionally adopted. For example, for the former of the above thermal conditions, the environmental temperature or the temperature of the thermal head is detected, and the energy applied to the heating element of the thermal head is controlled by a control signal corresponding to this detected value. This method is known. Also, regarding the latter heat storage,
There is a method of adding one thermal history pulse to the current printing pulse based on whether the data printed last time was a white dot or a black dot. Furthermore, a method has been adopted in which the printer is driven at an extremely slow printing cycle to prevent heat accumulation, thereby giving the heating element sufficient cooling time.

[Problem that the invention seeks to solve]

However, in the above-mentioned conventional techniques, even if each of these techniques is implemented independently, the effect is small, and there is still a problem that macroscopic or microscopic variations in print density occur.

In addition, especially when performing low-speed printing in consideration of heat accumulation, there is a disadvantage that it goes against the recent demand for high-speed printing.

[Purpose of the invention]

The present invention has been made in view of the disadvantages of the prior art, and an object of the present invention is to provide a print control system for a thermal printer that can uniformize print density and perform high-speed printing.

[Failure to solve the problem]

In the present invention, in a thermal printer that has a predetermined number of heating elements for printing and generates heat by energizing each heating element based on a predetermined pulse signal, the last black mark in the print data range up to n doors in the past is used. Forming a thermal history pulse having a time width proportional to the time elapsed since dot printing,
Accordingly, a first control means is provided which instructs energization of each heating element for each heating element. Furthermore, a chopping pulse having a duty ratio inversely proportional to the black dot printing rate of the entire heating element in the past printing range of at least m dots (m>n) is formed, and based on the chopped printing pulse signal, A method such as providing a second control means for instructing energization to each of the heating elements is adopted.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIGS. 1 to 6.

The embodiment shown in FIG. 1 has a heating element section H in which heating elements for printing H to H24 are arranged in rows. For this heating element section H, input printing data is processed and each heating element H,, H2゜...H24 is set to +V.
The printer is equipped with a printing control section 1 that is energized by a drive power source and generates heat. Functionally, this print control section 1 has a first
．． Second. and third control means IA, IB, and IC
In addition to the normal print control functions, this printer also has

The first control means IA controls each heating element H,, H2゜...
. . . Every H24, a thermal history pulse signal having a time width proportional to the elapsed time from the last black dot printing in the print data range up to the past 3 (=n) dots is generated. The heating element H+, H2, .

The second control means IB controls the past at least 10106 (
= A chino-knoping pulse is formed having a duty ratio inversely proportional to the black dot printing rate of the entire heating element H in the dot printing range. Based on the printing pulse signal chopped by this chopping pulse, each heating element H1, H2, . . . H24 is heated to print.

The third control means IC includes the first control means IC. Second control means IB
, acts on the IC. It also has a function of varying the time width of the thermal history pulse and the duty ratio of the chopping pulse in accordance with the environmental temperature.

The print control section 1 is specifically configured as shown in FIG.

The print control section 1 shown in FIG. 2 has a control mechanism 2 that controls the entire thermal printer. This control mechanism 2 is configured with a central processing unit (hereinafter simply referred to as "CPUJ") 4, a read-only memory (ROM) 6, a read/write memory (RAM) 8, etc.
The CPU 4 can perform predetermined calculations and control according to programs stored in the ROM 6 in advance.

As shown in the figure, the control mechanism 2 transfers print data output from a host device such as a computer to an interface circuit 1.
0 and the reception buffer 12. Furthermore, for the CPU 4, the temperature detection means 14
A detection signal from the sensor is output. This temperature detection means 14 has a function of detecting temperature and outputting a detection signal corresponding to the temperature. In this embodiment, the temperature detection means 14 is configured to detect the temperature of the environment where the thermal printer is placed.

On the output side of the control B mechanism 2, as shown in the figure, a timer 16 is provided.
．． N register 18. A pulse width register 20 is provided. The outputs of N register 18 and pulse width register 20 are configured to reach pulse generator 22 . The outputs of the timer 16 and the pulse generator 22 are configured to reach the Nant gate section G via the OR gate 24.

On the other hand, each heating element H,, H2,..., H2 of the print head
A driving voltage of +■ is applied to one end of each of the gates 4, and the other end reaches the output end of each Nant gate C+, Ct, . . . , G24 of the Nant gate section G responsible for switching. The output of the OR gate 24 is applied to one H active input terminal of each of the Nant gates G, , G, . Data is supplied to each. This register 26 latches print data from the register 28 in response to a latch signal from the CPU 4. Print data is written into this register 28 from the CPU 4 at appropriate timing.

By the way, as mentioned above, the CPU 4 starts the timer 1 for each print.
6 to output thermal history pulses P, , Pb, and PC for the past 3 (=n) dots (Fig. 3 (1)
). At the same time, calculations are performed based on a predetermined algorithm, and the calculated values are output to the register 28 at a predetermined timing.

The algorithm executed here is as follows. The print data from the day before last, the day before last, and the previous time are each A.
(A +, A z, ..., Azz), B
(B+.

B2. ..., BZ4), C(C+, Cz,
..., Cza), and the print data that is currently being printed is D (Dl, B2..., Dz-). When the strobe pulse of the first thermal history pulse P is generated from the timer 16, data obtained by calculating [X·B −C−D] is set in each bit of the register 28 for each bit. Similarly, in the case of the second thermal history pulse Pb, calculate [100 Koku D], and in the case of the third thermal history pulse PC, calculate (CD),
The results are sequentially set in the register 28. As a result, as will be described later, a pulse proportional to the elapsed time since the last black bit among the three previously printed bits is applied to each heating element H1, H2, . . . .

124, and thereby each heating element H1, H2,..., H24 generates heat (see Fig. 4 (1)).
) or 3)).

The CPU 4 further generates thermal history pulses P,,P,.

Following Pc, commands are sent to the N register 18 and pulse width register 20 as described above. Then, the N register 18 is caused to output 4 (=N) pulse signals ((2) in FIG. 3). In addition, the pulse width register 20 is set to
Output the pulse width signal specified by (Figure 3 (3)
). As a result, the pulse generator 22 is energized by these commands to form four (=N) chopping pulses P1 to P4 at the designated duty ratio,
This is output continuously (Fig. 3 (4)).

At the same time, the print data D that is currently to be printed is sent to each bit of the register 28. In this case, the chopping pulse P.

The duty ratio of P4 is for each heating element)! , H2゜..., H24, the total number of dots in the past 106 dots is 2544 dots (in this example, 24 dots).
Since it is assumed that the character is composed of the sub-capital of dot, 106
It is determined based on the ratio of black dot printing (black dot printing rate) performed in X24). In other words, the duty ratio is determined to be inversely proportional to the black dot printing rate.

Further, the CPU 4 A/D converts the detection signal output from the temperature detection means 14 to determine the temperature.

Based on this, the thermal history pulse P-=Pb.

The time width of the PC and the duty ratio of the chopping pulses P to P4 are varied based on the environmental temperature θ.

Specifically, when the environmental temperature θ is low, the fifth
As shown in FIG. 1, the time width of the thermal history pulse Pa+Pb+PC is extended, and the chopping pulse P.

Or the duty ratio of P4 increases. When θ is high, the opposite is true (see FIG. 5(2)).

Next, the operation of this embodiment will be explained.

When trying to print the print data D, the CPU 4
Calculate the environmental temperature information at that time. This determines the time width of the thermal history pulses P3°P, PC to be output and the duty ratio of the chopping pulses P1 to P4.

First, the CPU 4 sends a command to the timer 16 to generate three thermal history pulses P, , Pt, , P, taking into account the environmental temperature.
Output C. This pulse P8゜Pb, PC is passed through the OR circuit 24 to the Nant gates GI, Gz, . . . , G2
4.

In this case, the first thermal history pulse P is the Nandt gate G
,,G2. ..., when output to G24, each bit of register 28 contains A, B-C.
-D=E, and data E determined by E is set. This data E3 is written to the register 26 by a latch signal from the CPU 4, and
．． . . . are respectively output to G24. The Nant gates G, , G, . . . , G24 perform a logical operation on the NAND of the data based on the pulse signal P and the data E, and energize the heating elements H1, H2, . . . , H24. Each one decides what to do.

For example, when the first bit (E a l) of the data E1 is logic "1", the output of the Nant gate Gl that prints the first line of dots becomes a logic low level, and the +V drive power supply drives the heating element H0. is energized, and the heating element Hl is made to generate heat. On the other hand, when Ea is logic "0", the heating element H3 is not made to generate heat. Heat generation control based on this thermal history pulse P1 is performed for each dot, that is, for each heating element H+, Hz,
..., is carried out every H24.

Next, for the second thermal history pulse P, the Nandt gates G +, G 2 . ..., G24, a NAND operation is performed based on data E determined by B-C-D = E b.

As a result, it is determined whether or not to generate heat for each heating element H+, Hz, . . . , H24. Furthermore, the same process is performed for the third thermal history pulse PC based on CD=Ee.

As a result, as shown in Fig. 4, if all the past three dots of a certain heating element are white dots, it is energized by each of the three heat history pulses Pm1Pb+PC to generate heat ((1) in the same figure). reference). Also, of the past three dots, the first (
If the previous two times) is black dot printing, two pulses P
, , P (see (2) in the same figure). Furthermore, if the second slot (two times before) is black dot printing, one pulse P is applied. (See (3) in the same figure).

Furthermore, if the third (previous) print is a black dot, the thermal history pulse is not involved (see (4) in the same figure). That is, as a result, the shorter the time that has passed since the heating element was previously generated, the more heat is already stored in the heating element, and the preheating time is reduced.

As a result, even if there is a difference in heat storage between the heat generating elements during printing of the past three dots, as shown in Fig. 6 fl) and +21, the heat generated at the start of printing will vary depending on the addition of thermal history pulses P, Pb, and PC. The temperature is adjusted and approximately equalized. In this control, as the printed dots progress, the past three dots are checked each time.

As described above, when preheating is completed by the combination of thermal history pulses P, , Pb, P, the control mechanism 2 and the N register 18 . Palace width register 20. Pulse generator 22
Accordingly, chopping pulses P1 to P4 are formed. The chopping pulses P+ to P4 are outputted via the OR gate 24 to the Nandt gates G1 to G24. At this time, the print data D is set in the register 28 as described above. Therefore, the print data D
is latched and output to each of the Nant gates G to G24, and at each output, the print data D is subjected to four chopping steps ((1) in FIG. 6).

(See ■ in (2)). As a result, the heating elements H,,H,,
....

The current flowing through each H24 is also intermittent, and the heat generation temperature is also
As shown in Figures 11 and 21 (■), the temperature rises and falls repeatedly until it reaches a plateau.

Therefore, for example, by setting the driving voltage of 10 to a high value, the rise of heat generated by the thermal history pulses P, , P, , PC can be made more steep. Therefore, since the energization time can be set short, high-speed printing becomes possible.

Further, the duty ratio of the chopping pulses P to P4 is updated for each printing based on the past black dot printing rate. Therefore, changes in print density due to heat accumulation in the thermal head within a row are corrected moment by moment, resulting in more uniform print density. Here, the number of chopping pulses is N=4
It is not limited to , and may be any appropriate one.

On the other hand, the environmental temperature θ is constantly monitored. Therefore, if the environmental temperature changes while printing according to the above-described procedure, the time width of the thermal history pulse and the duty ratio of the chopping pulse are adjusted as needed, as described above. Thereby, even if the environmental temperature such as indoor temperature changes, the print density can be kept substantially constant. Here, the temperature detection means 14
The sensing element may be provided at a position where the temperature within the printer body can be detected, and the temperature rise caused by continuous operation of the printer may be considered as the environmental temperature. Thereby, the print density can be made more completely uniform.

Therefore, in this embodiment, for example, for crowded printing such as Chinese characters with a large number of strokes, the thermal history pulse is effective in preventing collapse and the like. In addition, chopping pulses are particularly effective against variations in black dots at the beginning and end of a line within a line. In other words, the heat generation temperature of the heating element is comprehensively corrected from a microscopic perspective due to the thermal history pulse, from an intermediate perspective due to the chopping pulse, and from a macroscopic perspective considering environmental temperature and the like. Therefore, the print density is approximately equalized. In addition to this, since a chopping pulse is provided, high-speed printing is also possible.

By the way, in the past, in order to secure cooling time and perform high-speed printing, a method was adopted in which two rows of heating elements were installed in the thermal head and the heating elements were alternately generated, but this example solves this problem. The need disappears.

In addition, when high-speed printing is performed by setting the power applied to the heating element high and printing with a short pulse width, the temperature of the heating element may rise too much and burn out, resulting in a shortened lifespan of the heating element. There was also. However, in this embodiment, since a chopping pulse is provided, there is an advantage that burnout of the heating element can be prevented and the life of the heating element can be extended. Furthermore, the present invention can also be applied to a single-line head used when printing on paper with poor smoothness.

In the above embodiment, the environmental temperature is also taken into account when controlling the heat generation temperature of the heating element, but if there is a condition such as using the device indoors at a relatively constant temperature, it may be necessary to take measures against the environmental temperature. The structure may be simplified by removing the third control means. Further, the values of the numbers n and m of dots are not necessarily limited to those mentioned above, and may be set to appropriate values.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to stabilize the heat generation temperature for printing by comprehensively considering printing conditions in the relatively recent past and printing conditions in the distant past, and to prevent excessive temperature of the heating element. Since the increase is prevented, it is possible to provide a printing control system for a thermal printer that is unprecedented and excellent in that a substantially constant printing density can be obtained and high-speed printing is possible.

Furthermore, the invention described in claim 2 has the advantage that the above-mentioned effects can be maintained even if the environmental temperature changes.

[Brief explanation of the drawing]

Fig. 1 is a functional block diagram showing one embodiment of the present invention;
The figure is a block diagram showing the specific configuration of Figure 1, and Figure 3 (1
) to 5) are timing charts showing output examples of each part in FIG. 2, FIG. 4 (1) to 4) are explanatory diagrams showing algorithms for thermal history pulses, and FIG.
11, (21 is an explanatory diagram of each pulse accompanying a change in environmental temperature, and FIG. 6 (11, +21 is an explanatory diagram showing an example of temperature rise of an arbitrary heating element, respectively. H,, H2, . . . , H24... heating element, P,
,P. PC...Heat history pulse, Pl to P4...
...Chopping pulse, IA...First control means, IB...Second control means, IC...
...Third control means. Patent applicant Japan Electric Co., Ltd. Figure 1 Ht, Hz, ---, H2a Transport B'y% Figure 3 Figure 4 (4)○○○-rto Figure 5 Figure 6

Claims (2)

[Claims] (1) In a thermal printer that has a predetermined number of heating elements for printing and generates heat by energizing each heating element based on a predetermined pulse signal, the last black dot in the print data range up to the past n dots. a first control means for forming a thermal history pulse having a time width proportional to the elapsed time from printing, and thereby instructing energization of each of the heating elements for each of the heating elements; forming a chopping pulse having a duty ratio inversely proportional to the black dot printing rate of the entire heating element in the printing range of m>n), and energizing the heating element based on the chopped printing pulse signal; 1. A printing control method for a thermal printer, comprising: a second control means for issuing commands. (2) In a thermal printer that has a predetermined number of heating elements for printing and generates heat by energizing each heating element based on a predetermined pulse signal, the last black dot in the print data range up to the past n dots. a first control means for forming a thermal history pulse having a time width proportional to the elapsed time from printing, and thereby instructing energization of each of the heating elements for each of the heating elements; forming a chopping pulse having a duty ratio inversely proportional to the black dot printing rate of the entire heating element in the printing range of m>n), and energizing the heating element based on the chopped printing pulse signal; a second control means for issuing a command, and a third control means for varying the time width of the thermal history pulse signal and the duty ratio of the chopping pulse according to the environmental temperature. Printer control method.