JPH0813549B2 - Thermal recorder - Google Patents

Description

Detailed Description of the Invention [Industrial applications]

The present invention relates to a thermal recording device used in a facsimile.

[Prior art]

FIG. 3 is a block connection diagram showing a conventional thermal recording apparatus disclosed in, for example, Japanese Patent Laid-Open No. 61-50464, in which 1 is a transfer clock for transferring an image signal (hereinafter, referred to as a transfer clock).
A signal input terminal for inputting TCK), a signal input terminal 2 for inputting an image signal (hereinafter abbreviated as PIX), and a signal input terminal 3 for inputting a recording cycle signal for one line (hereinafter abbreviated as LINE) 4 is a signal output terminal for outputting a 1-line recording end signal (hereinafter abbreviated as FIN), 5 is a PIX during transfer,
For example, a signal input terminal for inputting a high-level "H" signal (hereinafter abbreviated as TNSO), 6 is a black pixel counter as black pixel counting means for counting the number of black pixels in one line of the PIX, and 7 is transferred. A transfer pixel counter as a pixel counting means for counting the number of PIXs of one line, 8 is a collective recording block detection unit as a dividing method determining means for determining a dividing method of 1 line, and 9 is a recording for selecting a block to be recorded. Block selection unit, 10 is a division number counter as a division number determining means, 11 is a recording pulse width signal (hereinafter abbreviated as ENB)
Output counter, 12 applied pulse width generator, 13 PI
A strobe generator for latching X in the latch circuit of the thermal head, 14 is an AND gate, and 15 is a thermal head. Next, the operation will be described with reference to the timing charts of the signals of the blocks shown in FIG. First, PIX, TCK, and TNSO are input in synchronization with the rising edge of the line. Here, it is assumed that corresponding black pixels are distributed such that the first line of the PIX does not need to be divided, the second needs to be divided into two, and the third needs to be divided into three. When the above PIX and TCK are input, the black pixel counter 6,
The transfer pixel counter 7 starts counting black pixels and transfer pixels respectively, and the black pixel counter 6 needs to divide (n-1) divided signals OV when one line needs to be divided into n and recorded.
Output R. Then, the collective recording block detection unit 8 determines a division method for one line from the division signal OVR and the transfer pixel counter 7. At the same time, the division number counter 10 that receives the division signal OVR inputs the division number,
For example, the division number signal BDT indicating 1, 2, 3, ... Is output.
ENB output count counter 11 that receives this division count signal BDT
Presets the number of divisions and applies the applied pulse width
Trigger signal TRIG to output pulse width signal ENB from 12
Occurs. Further, the applied pulse width generation unit 12 to which the division number signal BDT is input determines the pulse width according to the division number and outputs the pulse width signal ENB in synchronization with the trigger signal TRIG. As shown in FIG. 4, the pulse width of the pulse width signal ENB becomes larger as the number of divisions increases like T _A <T _B <T _C. Next, the recording block selection unit 9 decodes the data of the block to be collectively recorded, and inputs the data to each block of the thermal head 15 via the AND gate 14. In addition, the ENB output number counter 11 that receives the pulse width signal ENB has a preset value (BDT) which is a division number signal.
Each time the output of the pulse width signal ENB is completed, the number of pulses (trigger signal TRIG) corresponding to the number of divisions is output until the pulse width signal ENB matches. Then, when the preset value and the output frequency of the pulse width signal ENB match, the 1-line recording end signal FIN is output. The strobe generator 13 outputs the 1-line recording end signal FI.
From N and TNSO, a strobe signal STB for latching the PIX to be recorded next in the latch circuit of the thermal head 15 is output. On the other hand, the sub-scan feed of the recording paper is performed by rotating a stepping motor by generating a predetermined drive current by a stepping motor driver (not shown) in synchronization with the rising of the line. The above operation is sequentially repeated to complete the recording of one page.

[Problems to be Solved by the Invention]

Since the conventional thermal recording apparatus is configured as described above, if lines with a lot of black and lines with a small amount of black appear alternately, the recording cycle of one line changes greatly according to the size of the number of divisions. Since the feed timing is fixed to the rising edge of the line, the recording interval of each block changes significantly line by line, causing "white spots" and "black streaks" in the sub-scanning direction, and the quality of the recorded image is large. There is a problem in that noise is increased due to a decrease or a large change in the stepping motor feed speed. The present invention has been made in order to solve the above problems, and it is a high quality recording that does not cause "white spots" or "black streaks" even if lines with a lot of black and lines with a little black appear alternately. It is an object of the present invention to obtain a thermal recording device that can obtain an image and suppress noise.

[Means for Solving the Problems]

The thermal recording apparatus according to the present invention uniquely determines the generation interval and the number of sub-scanning feed pulses based on the recording time predicted by the recording cycle predicting means, and generates the sub-scanning feed pulse synchronized with the applied pulse. It is generated at every interval.

[Action]

In the thermal recording apparatus according to the present invention, the generation interval and the number of sub-scan feed pulses are uniquely determined based on the recording time predicted by the recording cycle predicting means, and the sub-scan feed pulse synchronized with the applied pulse is generated at the interval. Since it is generated for each sub-scan feed pulse, the sub-scan feed pulse is generated at an interval according to the number of black pixels included in the image signal of one line.

Examples of the invention

An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, reference numeral 21 denotes a recording cycle predicting unit as a recording cycle predicting means, which predicts the cycle of a line to be recorded from the number of divisions of one line and the block selection time per one time. 22 is a sub-scan feed calculation unit (sub-scan feed calculation means),
The period output from the recording period predicting unit 21 is divided by the number N of sub-scanning feed pulses of the recording paper to determine the interval of sub-scanning feed pulses. 23 is a sub-scanning feed pulse generating means for performing block drive and sub-scanning feed pulse generation,
An applied pulse to each block and a sub-scan feed pulse synchronized with this applied pulse are generated from the number of times of division recording of one line output from the division number counter 10 and the output of a comparison circuit 25 described later. A sub-scan feed counter 24 counts the number of sub-scan feed pulses. Reference numeral 25 is a comparison circuit for comparing the contents of the ENB output number counter 11 and the sub-scan feed counter 24. In response to this result, the sub-scan feed pulse generation means
In step 23, the pulse applied to each block and the sub-scan feed pulse are synchronized with each other, and both pulses are controlled to be output without excess or deficiency. 26 is a stepping motor driver, 27
Is a stepping motor. It should be noted that 1 to 13 are the same as the conventional example, and the duplicated description will be omitted. FIG. 2 is a timing chart for explaining the operation of the block connection diagram of FIG. 1, in which the thermal head 15 is capable of 4-division recording (each block is indicated by ENB1 to ENB4) and sub-scan feed of one line. It shows the case of performing with 4 pulses. That is, in the case of G3 standard facsimile, the paper feed pitch of one line is one pulse. However, in this embodiment, one pulse Paper feed shall be performed. ENB1 to ENB4 are signals that indicate the drive timing of each block of the thermal head, PMDRV is a signal that indicates the sub-scanning paper feed pulse that is composed of each pulse 31 to 39, and as described above, it is one pulse. Paper feeding is performed. Therefore, the paper feeding of the first line is performed by the four pulses of the pulses 31 to 34, and the second feeding is performed by the four pulses of the pulses 35 to 38.
Paper will be fed on the line. Next, the operation of the present invention will be described. PI on the first line
When X and TCK are input from the signal input terminals 2 and 1, respectively, the collective recording block detection unit 8 receives the signals from the black pixel counter 6 and the transfer pixel counter 7, and performs 1
Decide how to divide lines. Also, the division counter
Reference numeral 10 outputs a division number signal BDT indicating the number of divisions of one line. The recording cycle predicting unit 21 outputs the number of divisions of one line and the output from the sub-scan feed pulse generating means 23 described later.
The recording time per line, that is, the period t of LINE is predicted by referring to the applied pulse width per time (in FIG. 2,
The first cycle is represented by t ₁ , and the second cycle is represented by t _2. )
The sub-scan feed calculation unit 22 determines the period τ of the sub-scan feed pulse from the result of the above period, for example, And ask. The sub-scan feed pulse generation means 23 uses the division number signal BD
Receiving the signals from T, the sub-scan feed calculating unit 22 and the ENB output number counter 11, the signals ENB1 to ENB4 for driving the recording blocks of the thermal head 15 and the signal PMDRV for driving the stepping motor driver 26 are Output by the method described in. First, after outputting the pulse 31 with the signal PMDRV, the signals ENB1 and ENB2 are simultaneously output to T ₁ in synchronization with this timing.
During the period, it is selectively driven. Here, the number of heating elements selectively driven by the signals ENB1 and ENB2 is set to a predetermined value or less that does not exceed the power supply capacity. After τ ₁ , pulse 32 is output, but T ₁ > τ
If it is ₁ , the signals ENB1 and ENB2 are subsequently selected. The signals ENB and PMDRV are accumulated by the ENB output counter 11 and the sub-scan feed counter 24, respectively, and the comparison circuit 25 compares the two, and the pulses are controlled so as to output just enough pulses. It That is, the signal PMDRV
Then, when the pulse 33 is output, the cumulative value of the pulse of the signal PMDRV becomes “3”, while the cumulative value of the ENB pulse is “2”, so at this timing, the signals ENB3 and ENB4 change to T ₁ Driven selectively. At the timing when the pulse 34 is obtained, the cumulative value of the ENB pulse is "4" and the cumulative value of the pulse in the signal PMDRV is "3", so only the pulse 34 is output.
When the recording of one line is completed, the ENB output counter 11 and the sub-scan feed counter 24 are reset to the initial value 0. Now, in the second line, the LINE cycle is predicted to be t ₂ , so The period of the signal PMDRV is determined so that after the pulse 35 is output, the signals ENB1 and ENB2 are selectively driven for T ₂ . Where ENB
Since the cumulative value of the pulse is “2” and the cumulative value of the pulse in the signal PMDRV is “1”, only the pulse 35 is output in the signal PMDRV and the ENB is not driven. Further, in the pulses 35 and 36, the signal PMDRV and the signal ENB are driven, respectively, and the recording of the second line is completed. In this way, by repeating the above operation,
Complete page recording. Although the number of recording blocks of the thermal head 15 is "4" and the sub-scanning feed pulse for one line is "4" in the above-mentioned embodiment, each value may be "2" or more. Has the same effect.

【The invention's effect】

As described above, according to the present invention, the generation interval and the number of sub-scan feed pulses are uniquely determined based on the recording time predicted by the recording period predicting means, and the sub-scan feed pulse synchronized with the applied pulse is generated. Since it is configured to occur at every occurrence interval, a line containing a lot of black,
Even if lines containing a lot of white appear alternately, it is possible to obtain a high-quality recorded image in which "white spots" and "black streaks" do not occur and to suppress noise. .

[Brief description of drawings]

FIG. 1 is a block connection diagram showing a thermal recording apparatus according to an embodiment of the present invention, FIG. 2 is a timing chart of signals of respective blocks showing the operation of the present invention, and FIG. 3 is a block showing a conventional thermal recording apparatus. The connection diagram and FIG. 4 are timing charts of signals of respective parts of the block showing the operation of the conventional example. 6 is a black pixel counting means (black pixel counter), 7 is a pixel counting means (transfer pixel counter), 8 is a division method determination means (collective recording block detection unit), 10 is a division number determination means (division number counter), 21 Is a recording cycle predicting means (recording cycle predicting section), 23 is a sub-scanning feed pulse generating means, 26 is a stepping motor driver, and 27 is a stepping motor. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A black pixel counting means for counting the number of black pixels included in an image signal of one line, and a division number for determining the number of divisions of one line based on the number of black pixels counted by the black pixel counting means. Determining means, recording cycle predicting means for predicting recording time for one line from the number of divisions of one line determined by the number of divisions determining means and pulse width of an applied pulse output to the thermal head; The recording time predicted by the prediction means is divided by the number of sub-scan feed pulses for one line to determine the sub-scan feed pulse generation interval, and the sub-scan feed pulse synchronized with the applied pulse. A sub-scanning feed pulse generating means that is generated at each generation interval determined by the sub-scanning feed calculating means, and a sub-scanning feed pulse generated from the sub-scanning feed pulse generating means. Thermal recording apparatus having a stepping motor driver for driving the stepping motor in accordance with.