JPH0465788B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a thermal recording device used in facsimiles, printers, etc., and more particularly to a recording device designed to reduce noise.

[Background of the invention]

A recording device that uses a thermal head to perform thermal recording does not require a developing or fixing mechanism.
Because it is small and can be manufactured at low cost, fax,
Widely used in printers, etc.

With the spread of OA (office automation), the field of use of these devices is rapidly expanding to general offices, and there is a strong demand for the development of low-noise, inexpensive equipment from the standpoint of preserving the office environment. It is being The noise of this type of recording apparatus includes not only the drive sound of the motor for conveying the recording paper but also the sound of the adhesive peeling off between the thermal head and the heat-sensitive layer of the recording paper. FIG. 6 shows the temperature change of the heating element during thermosensitive recording. When the heating element receives the heating pulse signal at point A, it is rapidly heated and then gradually cooled down. In this process, the heat-sensitive layer of the recording paper that is in contact with the heating element reaches its melting point near point B and reaches its freezing point near point C, and is colored and recorded. Since the recording paper reaches a temperature above its melting point, it fuses with the surface of the thermal head and
It solidifies and sticks over time.

The adhesive force between the thermal head and the recording paper is inversely proportional to the surface temperature of the thermal head. In order to achieve high-speed recording performance, thermal recording devices perform recording operations and paper feeding operations simultaneously.

On the other hand, in order to reduce the size of the recording power supply, the recording operation is performed by dividing one line into multiple blocks and performing the recording in a time-division manner, so compared to the recording time of one line, the time the recording paper is moving is relatively small. Becomes shorter. As a result, in some blocks in one line, the recording operation is performed while paper feeding is stopped, so that the thermal head and the heat-sensitive layer of the recording paper solidify and stick together before the next line of recording and paper feeding operation.

FIG. 7 shows the relationship between the surface temperature of the thermal head and the peeling force when peeling recording paper from the thermal head.

This peel force is inversely proportional to the temperature of the thermal head. The adhesive peeling sound is generated as a result of the recording paper and the thermal head being vibrated by the peeling operation.

FIG. 8 shows the results of frequency analysis of noise in a thermal facsimile. The broken line in the figure shows the characteristics of the driving sound of the motor, etc., and the solid line shows the composite characteristics of this driving sound and the adhesive peeling sound.
As is clear from this characteristic curve, the adhesive peeling sound is
The main component is a harsh high frequency component of 1000 Hz or more, and if the ambient temperature of the device is low or the
This is particularly noticeable when paper feeding is performed after recording is interrupted, that is, when paper feeding is performed after a relatively long cooling time. Moreover, this peeling force is a main cause of an increase in motor load, and is the biggest factor hindering the miniaturization and cost reduction of motors.

In the conventional apparatus, measures for sound absorption, sound insulation, and noise reduction have been taken at the thermal head and the recording paper outlet opening, as disclosed in, for example, Japanese Patent Application Laid-Open No. 59-214373. However, no consideration was given to improving the noise generation source itself. Also, JP-A-58-
Publication No. 118277 states that in order to equalize the recording density of each recording line, the first printing operation is performed twice after the recording operation has been interrupted for a predetermined period of time, but regarding noise countermeasures, was not taken into account.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a thermal recording device that reduces peeling noise caused by adhesion between a thermal head and recording paper, and achieves low noise.

[Summary of the invention]

In the present invention, a recording paper is moved in a direction intersecting the longitudinal direction of a heating element built into a thermal head, the surface of the thermal head is pressed against the recording paper, and a heating pulse is applied to this heating element to print. In a thermal recording device that performs recording, if paper feeding is interrupted for a predetermined time or longer after a heating pulse is applied to the thermal head and a recording operation is performed, at least one person involved in the recording operation is The above object is achieved by providing means for applying a heating pulse to a heating element and heating the heating element to a temperature higher than the melting point of the recording paper.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to FIGS. 1 to 5.

FIG. 1 is an explanatory diagram for explaining the recording operation of this embodiment. It is an example in which one line is divided into multiple blocks and recorded in time division, and the start timing of one line recording and paper feeding operation are the same. This is the case.
This condition is for achieving miniaturization of the recording power source and high-speed recording as described above.

In the figure, it is assumed that the recording operation for the first line is started at time _t1 . As shown in (b), one line is divided into four blocks D ₁₁ , D ₁₂ , D ₁₃ , by the timing of the drive start pulse of the paper feed motor that is synchronized with the recording start pulse in (a) (see (c)). D Divide into ₁₄ times and record by dividing the time, and as shown in (d), record paper is divided into 1
Sub-scanning is performed by the line interval l. On the other hand, the timer constantly monitors the elapsed time from the motor drive start pulse (in this case, time _t1 is the starting point), and within a predetermined time (hereinafter referred to as set time), the next line of recording paper is When the feed start pulse is input, the timer is reset at time _t2 , and the same recording and paper feeding operations as for the first line are performed.

Next, if the above elapsed time is longer than the set time,
If the paper feed sub-scanning operation is interrupted for longer than the set time, the timer circuit outputs a pulse as shown in (e) at time _t3 after the set time elapses from time _t2 . Depending on the timing of this pulse, the recorded information on the line immediately before the interruption (blocks D ₂₃ and D ₂₄ in the figure)
In other words, the blocks recorded when paper feeding was stopped are overwritten again. In this case, the heat-sensitive layer of the recording paper does not necessarily have to be heated to a temperature higher than the recording density, but it is sufficient to heat it to approximately the melting point. Therefore, in this setting, it is sufficient to apply the heating pulse only to a part of the heating elements involved in the recording operation. Alternatively, this can be achieved by lowering the voltage of the heating pulse or by shortening the width of the heating pulse than when performing a normal printing operation. Next, immediately after the overwriting is completed, the recording of the next line and the paper feeding operation are repeated.

Cases in which the above elapsed time is longer than the set time include communication with a foreign country where the S/N ratio cannot be sufficiently high in the case of facsimile, communication of original documents that contain densely recorded information and require a long time to decode, and G standards. This frequently occurs when communicating with low-speed recording devices such as.

The timer is started using timing corresponding to the paper feed timing signal, the output signal of the decoding circuit, the temperature of the thermal head or the thermal layer of the thermal paper of the recording paper, or the cooling time.

In the above embodiment, one line is divided into four blocks and time-division recording is performed, and the case is explained in which the motor activation pulse moves a distance l at once. The present invention can also be applied to the case where the paper is fed in batches.

Furthermore, in order to accurately specify the block in which a recording operation is to be performed after the paper feed has stopped, this can be realized using a sensor that monitors the movement of the paper feed axis, such as an encoder output and a recording timing signal for each block.

Further, the setting time of the above-mentioned timer can be selected to be an appropriate length in consideration of the level of adhesive peeling sound and performance such as recording unevenness.

FIG. 2 is a block diagram of a receiving section of a thermal facsimile to which the present invention is applied. In the figure, a demodulator 1 demodulates a modulated signal transmitted via a telephone network 2 from a facsimile transmitter (not shown) and converts it into an original digital signal. For example, in the international standard G facsimile, this digital signal is MH
(Modified Huffman) code. The decoder 3 decodes this MH code into an image signal.

The recording driver 4 inputs the image signal and drives the thermal head 5 to record the image signal on the recording paper 6. The control unit 7 manages the timing of the entire device,
The timing of the printing pulse (heating pulse) to the recording driver 4 and the driving pulse to the pulse motor 8 is determined by the generation timing of the image signal. The timing of generation of this image signal varies greatly depending on the amount of information contained in the image signal. For example, in the international standard thermal facsimile (MH code, minimum transmission time 20ms/line, transmission speed 4800bps, 1 line 1728 pixels), the time required to transmit an image signal for one line varies from 20ms to 1.08s. The control unit 7 of the present invention has a function of performing an overwriting operation when the drive interval of the pulse motor 8 is longer than a set value.

Next, control of this overwriting operation will be explained.

FIG. 3 is a block diagram of the facsimile circuit configuration, in which the received signal 2 is demodulated by the demodulator 1,
The MH code is stored in the code buffer 9.
The MH code is sent from the code buffer 9 to the decoder 3, which converts the MH code into an image signal and stores it in the line buffer 10. When the decoder 3 finishes decoding one line of image signals, it instructs the microcomputer (hereinafter referred to as microcomputer) 11 to finish. The microcomputer 11 inputs the elapsed time from the start of recording of the previous line from the timer 12, and determines whether recording of the previous line has ended or whether the elapsed time is longer than a predetermined value. If the elapsed time is longer than a predetermined value, the microcomputer 11 outputs a print pulse via the interface (hereinafter referred to as I/O) 13 to drive the recording driver 4 again, and outputs the image signal of the previous line in the recording driver 4. After overwriting, a transfer command is output to the decoder 3 and the line buffer 10 is
Based on the signal information inside, the image signal of the next line is transferred to the recording driver 4 for one line. When the decoder 3 completes the transfer, it instructs the microcomputer 11 to complete the transfer. When the microcomputer 11 receives the transfer end signal, it outputs a print pulse to the recording driver 4 via the I/O 13, outputs a drive pulse to the pulse motor 8, and resets the timer 2.

The above series of operations is repeated until the end of recording.

Note that 14 is a control program for controlling the entire device.

FIG. 4 is a block diagram of the control program.

In the figure, the microcomputer 11 is the control program 1
By executing step 4, the entire system is controlled. The control program is initialization 15, communication control 1
6, decoding control 17, and recording control 18, and a scheduler 19 manages the activation and status of these four tasks.

An example of the procedure of the recording control program will be explained using the flowchart of FIG. 5.

When the recording control 18 is activated by the scheduler 19, in step 1, the timer value is input. Regarding this input value, in step 2 it is determined whether recording of the previous line has been completed. If the recording has not ended, the process returns to the scheduler 19, but if the recording has ended, it is determined in step 3 whether or not there is a new image signal for one or more lines in the line buffer 10. New image signal is 1
Scheduler 1 if there are no more than the number of lines.
Returning to step 9, if the timer exists, it is determined in the next step 4 whether or not the elapsed time from the printing of the previous line is greater than the set value than the timer value. If the timer value is smaller than the set value, proceed to step 6. If the timer value is greater than the set value, the process proceeds to step 5, where a print pulse is output to the recording driver 4 to overwrite the image signal of the previous line. In step 6, a transfer command is issued to the decoder 3 to transfer one line of new image signals from the line buffer 10 to the recording driver 4. In step 7, the completion of the transfer is confirmed. In step 8, a print pulse is output to the recording driver 4 and a drive pulse is output to the pulse motor 8 to perform recording. Then, in step 9, the timer is reset and the process returns to the scheduler 19.

〔Effect of the invention〕

As explained above, according to the present invention, when paper feeding is interrupted for a predetermined time or longer after a recording operation, a heating pulse is applied to the heating element before moving the recording paper to the next line after the interruption, so that recording can be performed. It is possible to feed the paper with a small paper peeling force, and as a result, the adhesive peeling noise can be significantly reduced, so that the noise of the recording apparatus can be reduced to only the driving sound of the motor. Furthermore, this allows the use of a smaller and cheaper drive motor for paper feeding than conventional products.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram for explaining the recording operation in the recording apparatus of the present invention, FIG. 2 is a configuration diagram of a receiving section of a thermal facsimile to which the present invention is applied, and FIG. 3 is a circuit configuration of the facsimile of FIG. 2. 4 is a block diagram of the control program shown in FIG. 3, FIG. 5 is a flowchart showing the procedure of the control program shown in FIG. 4, and FIG. 6 is an explanatory diagram showing temperature changes of heating elements in thermosensitive recording. FIG. 7 is an explanatory diagram showing the relationship between the surface temperature of the thermal head and the peeling force when peeling recording paper from the thermal head, and FIG. 8 is a frequency analysis diagram of noise in a thermal facsimile. 1... Demodulator, 3... Decoder, 4... Recording driver, 5... Thermal head, 6... Recording paper, 7
...Control unit, 8...Pulse motor, 9...Sign buffer, 10...Line buffer, 12...Timer, 14...Control program.

Claims (1)

[Scope of Claims] 1. A recording paper is moved in a direction intersecting the longitudinal direction of a heating element built into a thermal head, the surface of the thermal head is pressed against the recording paper, and a heating pulse is applied to the heating element. In a thermal recording device that performs print recording by applying a heating pulse to the thermal head, if paper feeding is interrupted for a predetermined period of time or more after a heating pulse is applied to the thermal head and the recording operation is performed, the above-mentioned heating pulse is applied immediately before moving the recording paper to the next line after the interruption. applying a heating pulse to at least the heating element involved in the recording operation;
A thermal recording apparatus characterized by comprising means for heating the heating element to a temperature higher than the melting point of the recording paper. 2. The thermal recording according to claim 1, wherein the voltage of the heating pulse first applied to the heating element after paper feeding is interrupted is lower than the voltage of the heating pulse when performing a normal printing operation. Device. 3. Claim 1 or 2, characterized in that the width of the heating pulse first applied to the heating element after paper feeding is interrupted is shorter than the width of the heating pulse when performing a normal printing operation. A thermal recording device.