JPH0684086B2 - Thermal printer - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a print control method for a thermal printer, and more particularly, a print control for a thermal printer that controls the heat generation temperature of a heating element for printing according to various conditions. Regarding the scheme.

[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 the heating element when the environmental temperature is constant. This is because when the temperature of the heating element changes, the ink melting degree of the ink ribbon changes. The main thermal conditions in this case are the environmental temperature and the temperature change of the thermal head and the printer body itself due to continuous energization, and the heat storage of the heating element that has been generated in the relatively recent past.

Therefore, various techniques have been conventionally used to keep the print density constant. For example, for the former one of the above-mentioned 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 the control signal corresponding to the detected value. That method is known. Also, for the latter heat storage,
There has been a method in which one thermal history pulse based on whether the previously printed data is a white dot or a black dot is added to the current printing pulse. Further, a method has also been adopted in which the heating element is driven at an extremely low printing cycle so as not to easily accumulate heat and a sufficient cooling time is given to the heating element.

[Problems to be solved by the invention]

However, in the above-mentioned conventional techniques, even if each of these techniques is carried out independently, the effect is small, and there is a problem in that the print density varies in a macro or micro manner. Further, in particular, when low-speed printing is performed in consideration of heat storage, there is a disadvantage that it is against the recent demand for high-speed printing.

[Object of the Invention]

The present invention has been made in view of the inconveniences of the prior art, and an object of the present invention is to provide a print control system for a thermal printer capable of uniforming print density and performing high-speed printing.

[Means for solving problems]

According to the present invention, in a thermal printer which has a predetermined number of heating elements for printing and energizes each of the heating elements based on a predetermined pulse signal to generate heat, the last black dot in the print data range up to n dots in the past. Form a thermal history pulse having a time width proportional to the elapsed time from printing,
Thus, there is provided a first control means for instructing the heating element to be energized for each heating element. Furthermore, a chopping pulse having a duty ratio inversely proportional to the black dot printing rate of each heating element in the past printing range of at least m dots (m> n) is formed, and based on the chopping pulse signal by this chopping pulse. For example, a method of providing a second control unit for instructing the energization of each heating element is adopted.

Example of 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 portion H in which heating elements H ₁ to H ₂₄ for printing are arranged in a row length. For the heating element H, a printing control unit 1 for processing the input print data and heating each heating element H ₁ , H ₂ , ... H ₂₄ by energizing them from the + V drive power source is provided. There is. The print control unit 1 is functionally provided with first, second, and third control means 1A, 1B, and 1C in addition to the normal print control function.

The first control means 1A, for each heating element H ₁ , H ₂ , ... H ₂₄ ,
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 formed. The heat history pulse signal causes each of the heating elements H ₁ , H ₂ , ... H ₂₄ to generate heat, and has a function of making the temperature of the heating elements at the start of printing substantially uniform.

The second control means 1B forms a chopping pulse having a duty ratio inversely proportional to the black dot printing rate of the entire heating element H in the past printing range of at least 106 (= m) dots. The heating elements H ₁ , H ₂ , ... H ₂₄ generate heat based on the print pulse signal chopped by the chopping pulse to print.

The third control means 1C acts on the first and second control means 1B, 1C. It also has a function of varying the time width of the thermal history pulse and the duty ratio of the chopping pulse according to the environmental temperature.

The print controller 1 is specifically configured as shown in FIG.

The print control unit 1 shown in FIG. 2 has a control mechanism 2 that controls the entire thermal printer. This control mechanism 2
Is a central processing unit (hereinafter simply referred to as "CPU") 4, read-only memory (ROM) 6, read / write memory (RAM) 8
And so on. Therefore, the CPU 4 can perform predetermined calculation and control according to the program stored in the ROM 6 in advance.

As shown in the figure, the control function 2 sends the print data output from a host device such as a computer to the interface circuit 10
And receive via the receive buffer 12. Further, a detection signal from the temperature detecting means 14 is output to the CPU 4. This temperature detection means
14 has a function of detecting the temperature and outputting a detection signal corresponding to the temperature. In this embodiment, the temperature detecting means 14 can detect the environmental temperature in which the thermal printer is placed.

The output side of the control mechanism 2 is equipped with a timer 16, an N register 18, and a pulse width register 20, as shown in the figure. The outputs of the N register 18 and the pulse width register 20 are configured to reach the pulse generator 22. And the timer
The outputs of 16 and the pulse generator 22 reach the NAND gate G via the OR gate 24.

On the other hand, a driving voltage of + V is applied to one end of each of the heating elements H ₁ , H ₂ , ... H ₂₄ of the print head, and the other end of each of the NAND gates of the NAND gate section G is responsible for switching.
G _1, G _2, to the output terminal of the ...... G _24. NAND gate G ₁ ,
The output of the OR gate 24 is applied to one H active input end of each of G ₂ , ..., G ₂₄ , and the other H active input end is supplied with data from the register 26 for latching print data. It is like this. The register 26 latches print data from the register 28 in response to a latch signal from the CPU 4. For this register 28, CPU4
The print data is written at an appropriate timing.

By the way, as described above, the CPU 4 sends a command to the timer 16 for each printing, and the thermal history pulse P _{a for} the past 3 (= n) dots,
Output P _b and P _c (Fig. 3 (1)). At the same time, calculation is performed based on a predetermined algorithm, and the calculated value is output to the register 28 at a predetermined timing.

Here, the algorithm executed is as follows. Print data before last time, before last time and last time print data A
(A ₁ , A ₂ , ..., A ₂₄ ), B (B ₁ , B ₂ , ..., B ₂₄ ), C (C ₁ ,
C _2, ..., and C _24), the print data that is trying to present printed _{D (D 1, D 2,} ..., and D _24). And the first
When the strobe pulse of the th thermal history pulse P _a is generated from the timer 16, [...
The data obtained by calculating D] is set in each bit of the register 28. Similarly, in the case of the second thermal history pulse P _b a [· · D], in the case of the third thermal history pulse P _c calculates the [· D], this result sequentially register Set to 28. As a result, as will be described later, a pulse proportional to the elapsed time from the last black bit printing among the three bits printed in the past is formed for each heating element H ₁ , H ₂ , ..., H ₂₄ . The heating elements H ₁ , H ₂ , ..., H ₂₄ are caused to generate heat (see FIGS. 4 (1) to (3)).

CPU4 further heat history pulse P _a, P _b, subsequent to P _c,
As described above, the commands of the N register 18 and the pulse width register 20 are sent. Then, the N register 18 is made to output 4 (= N) pulse signals ((2) in FIG. 3). Further, the CPU 4 of the pulse width register 20 outputs a pulse width signal designated by the CPU 4 ((3) in FIG. 3). As a result, urged by these commands, the pulse generator 22 causes the chopping pulse P _1
4 to P ₄ (= N) are formed at a specified duty ratio, and these are continuously output (FIG. 3 (4)).

At the same time, the print data D to be printed at present is set in each bit of the register 28. In this case, the duty ratio of the chopping pulse P ₁ to P _4, each heating element H _1, H _2, ..., the dots of total 2544 dots (in this embodiment in the range of the past 106 dots for each of the H ₂₄
Since it is supposed to be composed of characters with a column length of 24 dots, 106
It is determined based on the ratio of black dot printing (black dot printing ratio) performed in (24). That is, the duty ratio is set to be inversely proportional to the black dot printing rate.

Further, the CPU 4 determines the temperature by A / D converting the detection signal output from the temperature detection means 14. Then, based on this, the time width of the thermal history pulses P _a , P _b , and P _c and the duty ratio of the chopping pulses P ₁ to P ₄ are varied based on the environmental temperature θ.

As a result, specifically, when the environmental temperature θ is low, the fifth
As shown in FIG. 1A, the time width of the thermal history pulses P _a , P _b and P _c is extended and the duty ratio of the chopping pulses P ₁ to P ₄ is increased. When θ is high, the opposite is true (see FIG. 5 (2)).

Next, the operation of this embodiment will be described.

When printing the print data D, the CPU 4 calculates the environmental temperature information at that time. This determines the time width of the thermal history pulses P _a , P _b , and P _c to be output and the duty ratio of the chopping pulses P ₁ to P ₄ .

Then, first, CPU 4 sends a command to the timer 16, three thermal history pulse P _a in consideration of environmental temperature, P _b, and outputs the P _c. The pulses P _a , P _b , and P _c reach the NAND gates G ₁ , G ₂ , ..., G ₂₄ via the OR circuit 24.

In this case, the first thermal history pulse P _a is the NAND gate G ₁ ,
G _2, ..., when it is output to G _24, in the corresponding respective bit of the register 28, bit by bit, data E _a which is determined by · · · D = E _a are respectively set. This data E _a is CP
Written to register 26 by the latch signal from U4,
Output to NAND gates G ₁ , G ₂ , ..., G ₂₄ , respectively. The NAND gates G ₁ , G ₂ , ..., G ₂₄ perform a logical operation of the NAND of the data based on the pulse signal P _a and the data E _a to generate the heating element H ₁ ,
Decide whether to energize H ₂ , ..., H ₂₄ .

For example, when the first bit (E _a1 ) of the data E _a is logic “1”, the output of the NAND gate G ₁ that prints the dots of the first line becomes a logic low level, and the heating element H is generated from the + V drive power supply. ₁ is energized and the heating element H ₁ is made to generate heat. Conversely
When E _a1 is logic “0”, the heating element H ₁ cannot be made to generate heat. The heat generation control based on the thermal history pulse P _a is performed for each dot, that is, for each of the heating elements H ₁ , H ₂ , ..., H ₂₄ .

Next, similarly for the second thermal history pulse P _b , in each of the NAND gates G ₁ , G ₂ , ..., G ₂₄ ,
.. Based on the data _Eb determined by D = _Eb ,
NAND operation is performed. As a result, the heating elements H ₁ , H ₂ , ..., H
Every ₂₄ hours it is decided whether or not to generate heat. Further, the third thermal history pulse _Pc is similarly _processed based on .D = Ec.

As a result, as shown in FIG. 4, when all the past three dots of a certain heating element are printed with white dots, heat is generated by being urged by each of the three thermal history pulses P _a , P _b , and P _c. (See (1) in the figure). Further, when the first (two before the last) of the past three dots is black dot printing, heat is generated based on the two pulses P _b and P _c (see (2) in the same figure). Furthermore, when the second (previously before) black dot printing is performed, heat is generated only based on one pulse P _c (see (3) in the same figure). Furthermore, 3
When the second (previous) time is black dot printing, the thermal history pulse is not involved (see (4) in the same figure). That is, as a result of this, the shorter the time that has elapsed since the heat was generated in the past, the more pre-heating time is reduced, assuming that more heat is already stored in the corresponding heating element.

As a result, as shown in FIGS. 6 (1) and 6 (2), even if there is a difference in heat storage between the heating elements in the past printing of 3 dots,
By adding the heat history pulses P _a , P _b , and P _c , the temperature of the heating element at the start of printing becomes substantially uniform. In this control, the past 3 dots are checked each time the print dot advances.

As described above, when the preheating is completed by the combination of the thermal history pulses P _a , P _b , and P _c , the control mechanism 2, the N register 18, the palace width register 20, and the pulse generator 22 generate the chopping pulses P ₁ to P _4. It is formed. The chopping pulses P ₁ to P ₄ are output to the NAND gates G ₁ to G ₂₄ via the OR gate 24. At this time, register 28
As described above, the print data D is set in the.
Therefore, the print data D is latched, and each NAND gate is
When output to G ₁ to G ₂₄ , the print data D is subjected to four choppings at each output (see FIGS. 6 (1) and 6 (2)). As a result, the heating element H ₁ ,
The current flowing through each of H ₂ , ..., H ₂₄ is also interrupted, and the heat generation temperature rises and falls repeatedly as shown in FIGS.

Thus, for example, been set to a higher driving voltage of + V, the thermal history pulse P _a, can be P _b, keep the steeper the rise of the heat generated by the P _c. Therefore, since the energization time can be set short, high-speed printing is possible.

Further, the duty ratio of the chopping pulses P ₁ to P ₄ is updated for each printing according to the past black dot printing rate. Therefore, the change in print density due to the heat accumulation of the thermal head in each row is corrected every moment, and the print density becomes more uniform. Here, the number of chopping pulses is not limited to N = 4 and may be any appropriate number.

On the other hand, the environmental temperature θ is constantly monitored. Therefore, if the environmental temperature changes during printing according to the procedure described above, the time width of the thermal history pulse and the duty ratio of the chopping pulse are adjusted at any time, as described above. As a result, the print density can be kept substantially constant even if the environmental temperature such as the room temperature changes. Here, the detection element of the temperature detection means 14 may be provided at a position where the temperature can be detected in the printer main body, and the temperature rise due to continuous operation of the printer may be taken into consideration as the environmental temperature. As a result, the print density can be made more uniform.

For this reason, in the present embodiment, for example, for a print in which Chinese characters or the like having a large number of strokes are congested, the thermal history pulse is prevented from being crushed and the effect is exerted. Further, the chopping pulse is particularly effective for the variation of the black dots at the beginning and the end of the line. That is, the heat generation temperature of the heat generating element is comprehensively corrected from the viewpoint of miracles due to the thermal history pulse, from the intermediate viewpoint due to the chopping pulse, and from the macro viewpoint considering the environmental temperature and the like. Therefore, the print density is made substantially uniform. At the same time, since the chopping pulse is provided, high-speed printing is also possible.

By the way, conventionally, in order to secure high-speed printing while ensuring a cooling time, a method of providing two rows of heating elements in the thermal head to alternately generate heat has been adopted, but according to this embodiment, this is necessary. Disappears. In addition, when the power applied to the heating element is set high and printing is performed with a short pulse width for high-speed printing, the temperature of the heating element rises too much and burns out, which shortens the life of the heating element. There was also. However, since the chopping pulse is provided in the present embodiment, there is an advantage that the burnout of the heating element can be prevented and the life can be extended. Furthermore, the present invention can be applied to a single-row head used when printing on paper with poor smoothness.

In the above embodiment, the environmental temperature is also taken into consideration in the heat generation temperature control of the heating element. However, when there is a condition that it is used at room temperature of a relatively constant temperature, it is necessary to deal with the environmental temperature ( The configuration may be simplified by removing the third control means). Further, the values of the dot numbers n and m are not necessarily limited to those described above, and may be appropriate values.

〔The invention's effect〕

As described above, according to the present invention, the heat generation temperature for printing is made constant by comprehensively considering the relatively near past printing situation and the far past printing situation, and the excessive temperature of the heating element is also taken into consideration. Since the rise is prevented, it is possible to provide an unprecedented excellent print control method for a thermal printer that can obtain a substantially constant print density and enable high-speed printing.

Further, the invention according to claim 2 has an advantage that each of the above-mentioned effects can be maintained even if the environmental temperature changes.

[Brief description of drawings]

FIG. 1 is a functional block diagram showing an embodiment of the present invention, and FIG.
FIG. 3 is a block diagram showing the specific configuration of FIG. 1, FIGS. 3 (1) to 3 (5) are timing charts showing the output examples of the respective parts of FIG. 2, and FIGS. 4 (1) to 4 are Explanatory drawing which shows the algorithm for each heat history pulse, 5th
FIGS. 1 (1) and (2) are explanatory diagrams of each pulse according to a change in environmental temperature, and FIGS. 6 (1) and 6 (2) are explanatory diagrams showing examples of temperature rises of arbitrary heating elements. H ₁ , H ₂ , ..., H ₂₄ , ... heating element, P _a , P _b , P _c ... thermal history pulse, P ₁ to P ₄ ... chopping pulse, 1A ... first control means, 1B ...... Second control means, 1C ...... Third control means.

Claims (2)

[Claims] 1. In a thermal printer having a predetermined number of heating elements for printing and energizing each heating element based on a predetermined pulse signal to heat the heating elements, the temperature of the heating elements at the start of printing is substantially uniform. As described above, a heat history pulse having a time width proportional to the elapsed time from the last black dot printing in the print data range up to the past n dots is formed, thereby energizing each heating element for each heating element. The first control means for instructing and preheating, and the black dot printing rate of the entire heating element in the past printing range of at least m dots (m> n) after the preheating by the first control means is completed. A second chopping pulse having a duty ratio inversely proportional to, and instructing energization to each of the heating elements based on a printing pulse signal for performing chopping printing. Thermal printer characterized by comprising a control means. 2. In a thermal printer having a predetermined number of heating elements for printing and energizing each of the heating elements based on a predetermined pulse signal to generate heat, the temperature of the heating elements at the start of printing is substantially uniform. As described above, a heat history pulse having a time width proportional to the elapsed time from the last black dot printing in the print data range up to the past n dots is formed, thereby energizing each heating element for each heating element. First control means for instructing and preheating, and after completion of preheating by the first control means, black dot printing rate of all the heating elements in the past printing range of at least m dots (m> n) A second chopping pulse having a duty ratio inversely proportional to, and instructing energization to each of the heating elements based on a print pulse signal for performing chopping printing. With a control unit, thermal printer, characterized in that the duty ratio of the chopping pulse and duration of the thermal history pulse signal with a third control means allowed to variably in accordance with the environmental temperature.