JPH0371025B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for driving a thermal head in a thermal recording apparatus using a thermal head.

[Conventional technology]

2. Description of the Related Art A thermal recording apparatus that performs recording using thermal recording paper or an ink sheet having a heat-melting ink layer usually uses a thermal head in which heating elements are arranged in a row. These thermal recording devices perform recording by causing a heating element to generate heat corresponding to input recording information and applying thermal energy to a thermal recording paper or a thermal transfer ink sheet.

When recording as described above, the time required for recording can be shortened by applying a signal corresponding to recording information to all the heating elements of the thermal head and simultaneously recording one line. However, in this case, the power supply capacity must be increased so that all the heating elements can be driven.

Therefore, there is a method of dividing one line of recording information into a plurality of blocks and recording each block one by one.
Although this method allows the power supply capacity to be reduced, the recording time increases by the number of divisions.

In order to solve this increase in recording time, conventional thermal recording devices count the number of black dots of recorded information included in each divided block, add the number of black dots for each block, and calculate the sum of the black dots for each block. A method is adopted in which recording is performed on these blocks at one time within a range that does not exceed a value determined by the capacity. This method will be specifically explained with reference to FIG.

The drawings show an example of division of recorded information and a driving time chart of the thermal head. Let the number of heating elements of the thermal head be N (generally N is about 2048). In other words, one line of recorded information is N dots. This recorded information is divided into M (in the example of this figure, M=
8), and each block will be called B ₁ , B ₂ , B ₃ . . . B ₈ in order.

Next, set the number of black dots included in the block to 100, 80, 0, 10, 200, 0, 10, 50 in order from B ₁ ,
The number of black dots P (P is determined by the power supply capacity) that can be recorded at one time is 256. Here, add the number of black dots included in each block in order from _B1 ,
The combination of blocks whose sum does not exceed P is B ₁
~ _B4 and _B5 ~ _B7 and _B8 .

In this way, the number of black dots of the recording information is counted and the blocks _B1 to B8 are divided into groups consisting of one or more blocks, that is, the blocks B1 to _B8 , so that the number of black dots recorded at one time is below a _certain value P. _B4 and _B5
By dividing into groups _B7 and _B8 and recording by sequentially selecting these groups, the number of times the thermal head is driven can be reduced (in the example shown in this figure, eight times are reduced to three times) and the recording time can be shortened. It is being shortened.

By the way, problems related to recording using a thermal head include problems in recording quality in addition to power supply capacity and recording time.

Heat accumulation in the heating element is the main cause of recording quality deterioration. In other words, if the same heating element is driven several times in succession for each line for a certain period of time, heat will accumulate in each heating element during high-speed recording when sufficient cooling time cannot be taken. As a result, the recording density increases toward later lines, and recording quality deteriorates.

In order to solve this uneven recording density, there is a method of correcting the energization time of the heating elements of the current line by referring to past recorded information. This method will be specifically explained with reference to FIG.

The past record information to be referred to is usually two lines before the current line. In the figure, D _0,-1 , D _0,0 and D _0,1 are the recorded information of the current line, and D _1,-1 ,
Record information before D _1,0 and D _1,1 lines, D _2,-1 ,
D _2,0 and D _2,1 are two lines of previous recorded information.

Here, in order to obtain a certain recording quality,
The corrected heating element energization time T _0,0 for D _0,0 is:
It is determined by the following equation (1) with reference to the recorded information of 9 dots shown in FIG.

T _0,0 = [T-( ₂ 〓 ⁱ⁼⁰ ₁ 〓 ^j=1 Wi.j・Di・j)] D _0,0 ...(1) T is the maximum energization time of the heating element before correction, Di .j is reference recording information, which is 1 when it is a black dot and 0 when it is not a black dot, i indicates the position in the line direction, j indicates the position in the row direction of the heating elements, and Wi.j is This is the weighting amount of the reference record information shown.

In addition, among the recorded information two lines ago, D _2,-1 and D _2,1
Since this information has little influence on the recording dot D _0,0 , both W _2,-1 and W _2,1 are 0 in the weighting amount shown in FIG.

Now, equation (1) is usually calculated using a digital circuit.

That is, the maximum energization time T of the heating element is divided to determine the energization time corresponding to equation (1). In the example of FIG. 7, the maximum energization time T is divided into five parts, and the length corresponding to the corrected energization time determined by equation (1) is selected. In other words, the energization time is the minimum S ₀
Only, S ₀ to S ₁ , S ₀ to S ₂ , and maximum S ₀ to S ₄ are selected from five levels.

[Problem that the invention seeks to solve]

However, the above-mentioned conventional method can achieve a satisfactory recording speed when the recorded information does not have a large number of black dots, such as characters and sentences.
If the recorded information includes a large number of black dots, such as diagrams and pictures, in the worst case, all of the recorded information will be black dots, and the time it takes to drive the thermal head to record one line will increase significantly. As a result, there was a problem in that the recording speed became extremely slow.

[Means to solve the problem]

In order to solve such problems, the present invention has the following features:
The heating elements of the thermal head capable of recording dots for a line are divided into multiple blocks, and a fixed number of heating elements that can simultaneously record dots is determined depending on the power supply capacity, and the maximum energization time of the heating elements is determined. is divided into a plurality of times, recording information up to a predetermined line in the past is stored for each heating element, the recording dots of the line to be recorded are counted for each block, and the heating element corresponding to the recording dot is Select a plurality of blocks by dividing them into groups of one or more blocks such that the number of heating elements is equal to or less than the above-mentioned fixed number of heating elements, and set the energization time for each heating element corresponding to the recording dots of the selected group as described above. A thermal recording device that calculates a value based on recording information, selects a value corresponding to the calculation result from a plurality of energizing times based on a combination of the divided times, and performs recording by driving a heating element at the selected energizing time. In the method of driving a thermal head in
It is determined at each of the above divided times whether or not the energization of all the heating elements of the block corresponding to the recording dots of the currently driven group has ended, and if the energization has ended, the next group is immediately started. The feature is that the heating element is energized.

[Effect]

According to the present invention having such a configuration, recording is performed by driving the heating elements for each group consisting of one or more blocks with a current application time based on a correction value, and the current application to the heating elements of the group currently being recorded is performed. Immediately after completion of this process, power is started to be applied to the heating elements of the next group, and this process is repeated to record one line.

Therefore, according to this, even if the elapsed time has not reached the time assigned to that group, that is, the maximum energization time of the heating elements, recording of the next group can be started, thereby reducing the time required for recording. Since the time can be shortened, the recording speed can be significantly improved.

In particular, in the case of a recording pattern that includes a large number of black dots that are continuous in the line direction, the same heating element must be energized continuously for each line, so the energization time should be shortened. As a result, the recording time can be significantly shortened.

Furthermore, when dividing and driving so that the number of black dots included in one group is below a certain value,
If the number of black dots is very large, the number of groups will increase accordingly, but according to the present invention, since the current application time is controlled to be short, the recording time can be significantly shortened.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings. Figure 1 is a block diagram, where 1 indicates recorded information;
Reference numeral 2 denotes a RAM which records input recording information 1 for one line (current line). 3 is RAM
It is connected to RAM2 and stores the recorded information of the previous line. 4 is a RAM, which is similarly connected to the RAM 3 and stores information recorded two lines before.

5 is a counter which counts the number of black dots in the input recorded information 1, and the heat generating element of the thermal head, which will be described later, is connected to the block B ₁ as shown in FIG.
When divided into 8 blocks of ~ _B8 , the number of black dots is counted for each block, and the number is calculated by the control circuit 6.
Enter. This control circuit 6 is a circuit using a microprocessor and is controlled by a program.
The control circuit 6 divides the blocks B ₁ to _{B 8} into groups of one or more blocks, such as B ₁ to B ₄ , so that the number of black dots recorded simultaneously for each block is below a certain constant value P. and B ₅
~ Divide into groups B ₇ and B ₈ and select this group sequentially.

When the input of the recording information 1 of the current line is completed, the control circuit 6 starts reading RAM2, RAM3, and RAM4 simultaneously.

7 is a 3-bit shift register connected to the output of RAM2, and D _0,-1 , D _0,0 and D _0,1 in FIG.
Record information corresponding to is stored. Similarly, shift register 8 is connected to the output of RAM 3, and as shown in FIG.
Corresponding to D _1,-1 , D _1,0 , D _1,1 , the shift register 9 is
Connected to the output of RAM4, D _2-1 , D _2,0 ,
Corresponds to D _2,1 .

On the other hand, the control circuit 6 sets in the register 10 3-bit data (that is, a numeric value from ₀ to ₄ can be expressed in decimal notation) representing the energization states S0 to S4 shown in FIG.

11 is a ROM, which performs the calculation of equation (1). That is, equation (1) is calculated from the outputs of shift registers 7, 8 and 9 representing the 9-dot recording information shown in FIG. 5 and the weighting amounts shown in FIG. At this time, according to the energization state S ₀ to _{S 4} indicated by the register 10,
The ROM 11 corrects the energization time. In other words,
If the recorded dot Do, 0 is a black dot and no correction has been made, the ROM 11 outputs a signal 1 representing energization for all states S ₀ to _{S 4} . Also, if D _0,0 is a black dot and there is a correction, the ROM 11 outputs 1 from So to Sk according to the amount of correction,
Signal 0 indicating that no current is applied from S _k+1 to S ₄
(0≦k≦3). If D _0,0 is a white dot, the ROM 11 outputs 0.

A shift register 12 converts the output of the ROM 11 from serial data to parallel data.

A latch driver 13 stores (latches) recorded data converted into parallel data and drives the heating element 14. The shift register 12, latch driver circuit 13, and heating element 14 constitute a thermal head 15.

The control circuit 6 outputs a block selection signal 16 to the latch driver circuit 13 for selecting blocks included in the group to be simultaneously recorded according to the number of black dots in each block, so that only the selected blocks are energized.

The control circuit 6 repeats the cycle of reading the RAMs 2, 3, and 4 and energizing the heating element 14 from _S0 to _S4 . However, at this time, the heating element energization time is
Since it is corrected using equation (1), you do not need to proceed to S ₄ .
The ROM 11 may output 0 (no current) to all recording dots in the selected block.

The control circuit 6 outputs a recording dot valid signal 17 when the recording dots of the selected block, such as Do and o, are being read from the RAM 2. This recording dot valid signal is sent to the 2-bit shift register 18.
and is synchronized with the recording dot Do,0.

ROM11 output and 2-bit shift register 1
The output of 8 is logically ANDed with the AND gate 19,
Flip-flop 2 when both outputs are 1
Set to 0.

Note that the flip-flop 20 has a control circuit 6.
Reset when starting to read RAM2, 3 and 4.

The control circuit 6 operates during the energization cycle (each S _k , k in Fig. 7).
=0...4) is completed, the output of the flip-flop 20 is referred to. The flip-flop 20 is set to 1 if one or more of the recording dots in the selected block is energized, and remains reset if all of the recording dots in the selected block are not energized. be.
Therefore, when the flip-flop 20 has been reset, the control circuit 6 knows that the recording of the blocks in the currently selected group has been completed, even if it has not reached the energized state _S4 , and therefore starts recording the blocks in the next group. Select to start recording immediately. Start recording the remaining groups. If there are no remaining blocks, the control circuit 6 starts recording the next line.

The respective recording times when recording is performed using this method and when recording is performed using the conventional method will be explained with reference to FIG.

FIG. 3 is a time chart during recording, and () shows the conventional method and corresponds to FIG. 4, and () shows the method according to this embodiment and corresponds to FIG. 2. There is.

As seen in this figure, in the conventional method, the heating elements 1 of the group consisting of blocks B ₁ to B ₄ are first
4 is energized for S ₀ hours to record dots, and after time T has elapsed, the next group of heating elements 14 consisting of blocks B ₅ to B ₇ is energized for S ₀ , S ₁ , S ₂ hours. Record dots. Then, after time T has elapsed (time 2T has elapsed since the start of energization in the first group), block _B8 energizes the heating elements 14 of the next group for times S ₀ and S ₁ to record dots. After time T has elapsed (time 3T has elapsed since the start of energization for the first group), recording of one line is completed.

On the other hand, in the method according to this embodiment, _S0 is first applied to the heating elements 14 of the group consisting of blocks _B1 to _B4 .
Electricity is applied for a time to record dots, and immediately after the lapse of this S ₀ time, electricity is applied to the heating elements 14 of the next group consisting of blocks B ₅ to B ₇ for S ₀ , S ₁ , and S ₂ hours. Immediately after the lapse of S ₀ , S ₁ , and S ₂ hours, the next group of heating elements 14 is activated by block B ₈ .
Dots are recorded by energizing S ₀ and S _{for 1} hour, and one run-in recording is completed after S ₀ and S for ₁ hour. Therefore, in the conventional method, it takes 3T to record one line, that is, to finish driving the heating elements 14 of all blocks of the thermal head 15.
With the method according to this embodiment, driving of the heating elements 14 of all blocks of the thermal head 15 can be completed in less than 2T.

〔Effect of the invention〕

As explained above, the present invention performs recording by driving heating elements for each group consisting of one or more blocks with a current application time based on a correction value, and the current application to the heating elements of the group currently being recorded is As soon as the heating elements of the next group are energized, even if the elapsed time has not reached the time allotted to that group, that is, the maximum energization time of the heating elements, the next group Since the time required for recording can be shortened, the recording speed can be significantly improved.

In particular, in the case of a recording pattern that includes a large number of black dots that are continuous in the line direction, the same heating element must be energized continuously for each line, so that the energization time is shortened. As a result, an excellent effect can be obtained in that the recording time can be significantly shortened.

Furthermore, when dividing and driving so that the number of black dots included in one group is below a certain value,
If the number of black dots is very large, the number of groups will increase accordingly, but according to the present invention, since the current application time is controlled to be short, the recording time can be significantly shortened.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing an embodiment of the present invention, Fig. 2 is an example of dividing recorded information according to the invention and a driving time chart of a thermal head, Fig. 3 is a driving time chart of a thermal head, and Fig. 4 is a conventional one. 5 is an explanatory diagram of the reference information tail of recording dots. FIG. 6 is an explanatory diagram of the weighting amount of the reference storage information in FIG. 5. FIG. 2 is a diagram showing an example of division of heat generating element time. 1... Input record information, 2, 3, 4... RAM,
5... Counter, 6... Control circuit, 7, 8, 9...
...Shift register, 10...Register, 11...
ROM, 12...Shift register, 13...Latch driver, 14...Heating element, 15...Thermal head, 16...Block selection signal, 17...
Recording dot valid signal, 18...shift register,
19...AND gate, 20...flip-flop.

Claims (1)

[Scope of Claims] 1. The heat generating elements of a thermal head capable of recording one line of dots are divided into a plurality of blocks, and a fixed number of heat generating elements capable of simultaneously recording dots is determined depending on the power supply capacity. Divide the maximum energization time of the heating element into multiple times, store recording information up to a predetermined past line for each heating element, count the recording dots of the line to be recorded for each block, Select a plurality of blocks by dividing them into groups of one or more blocks so that the number of heating elements corresponding to the recording dot is equal to or less than the above-mentioned certain number of heating elements, and corresponding to the recording dot of the selected group. The energizing time for each heating element is calculated based on the recorded information, the value corresponding to the calculation result is selected from a plurality of energizing times based on the combination of the divided times, and the heating element is driven with this selected energizing time. In a method for driving a thermal head in a thermal recording device that performs recording, it is determined at each of the above-mentioned divided times whether or not the energization of all heating elements of the block corresponding to the currently driven group of recording dots has ended. A method for driving a thermal head in a thermal recording device, characterized in that, if the above-mentioned energization has ended, energization is immediately carried out to the heating elements of the next group.