JP3067931B2 - Thermal head preheating method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for preheating a thermal head which shortens the time required to complete the preheating of the thermal head at a low temperature.

[0002]

2. Description of the Related Art Recently, printing apparatuses using a thermal head have been widely used in facsimile apparatuses and the like.
Generally, in a printing apparatus using a thermal head, a voltage based on line data is applied to each heat-generating resistance element of the thermal head, and a recording paper (thermal paper) is colored by its heating action.

That is, since the thermal head causes the recording paper to be colored by the heat-generating action of each heat-generating resistive element, the print density may be uneven depending on the temperature of the heat-generating resistive element. In other words, the thermal head basically has a lower sensitivity when the temperature is lower, so that when the temperature is lower, the print density is lower, and in some cases, color may not be generated unless the energy supply amount is increased, This is a cause of uneven print density.

In a facsimile machine, the communication speed is sequentially processed according to a predetermined communication procedure in accordance with a communication speed set with a partner facsimile machine, regardless of the printing capability of the printing device. . for that reason,
If the communication data is processed in real time without a buffer, the printing speed cannot keep up with the communication speed, and a situation may occur in which all communication contents cannot be printed.

Such a situation occurs when the ambient temperature at the start of communication is low (for example, 0 degrees, 5 degrees, 10 degrees, etc.), and does not occur when the ambient temperature is high (for example, 20 degrees or more). That is, in other words, even if the ambient temperature is low, such a situation does not occur if the temperature of the head (the temperature of the portion in contact with the recording paper) is high.

Focusing on this point, a technique for eliminating unevenness in print density by preheating a heating resistor element has been disclosed in, for example, JP-B-60-22630 and JP-B-63.
Japanese Patent Publication No. 26712, Japanese Patent Publication No. 3-72470, and Japanese Patent Publication No. 4-39433.
However, the preheating techniques proposed in the above publications are all during a printing operation, and are not techniques for performing appropriate preheating in a standby state before performing a printing operation.

Therefore, the present inventor has proposed a preheating method for preheating the thermal head to a predetermined temperature during a standby period in which a printing operation is not performed. In this method, when the temperature of the thermal head is low when the power is turned on (that is, when the ambient temperature is low and the temperature is low), the thermal head performs a printing operation to a degree that does not cause coloration, and gradually raises the thermal head to a certain temperature. , And then control to be within a predetermined temperature range.

According to this method, regardless of the ambient temperature,
It is possible to perform a good printing operation without density unevenness from the start of the facsimile receiving operation. However,
In this method, if the ambient temperature is low and facsimile reception occurs immediately after turning on the power,
There has been a problem that the preheating operation has not been sufficiently performed yet, which may hinder the printing operation. For example, when the ambient temperature is extremely low (0 degrees), it takes several tens of minutes to complete the preheating.

In view of the above problems, the present invention is a further improvement of the proposed preheating method, in which a black printing operation is performed at all times such as when the power is turned on, and the thermal head is quickly brought into a predetermined temperature range. It is an object of the present invention to provide a method for preheating a thermal head, which is capable of performing a good printing operation for facsimile reception immediately after the power is turned on by raising the power.

[0010]

In order to solve the above-mentioned problems, a method for preheating a thermal head according to the present invention is directed to a heating resistor element for one line to which a strobe signal for controlling an applied voltage is applied to one of terminals. A shift register that outputs line data for printing to each of the other terminals of the heating resistor elements to drive the heating resistor elements, and a temperature sensor that detects the temperature of the entire head including the heating resistor elements. In a thermal head with
Immediately after the power is turned on or immediately after the recording paper is replaced, the entire black printing operation is performed for a fixed length or for a certain period of time to print the entire black on the recording paper. Is repeatedly performed so as to keep the temperature within a preset temperature range.

[0011]

When the power is turned on or immediately after the replacement of the recording paper, the entire black printing operation is performed for a predetermined length or for a predetermined period of time to perform the full black printing on the recording paper. As a result, even when the ambient temperature of the installation location is low, the entire black printing operation is performed when the power is turned on, so that the temperature of the thermal head quickly rises to a predetermined temperature range. That is, it is possible to shorten the time until the preheating of the thermal head is completed.

As a result, a favorable printing operation can be performed even for facsimile reception immediately after the power is turned on. Also,
By performing black printing on the entire surface, it is also possible to confirm printing omission due to damage to the thermal head or the like. In the present invention, the same printing operation is performed immediately after the recording paper is replaced. This makes it possible to check the mounting state of the recording paper, and also to check for missing prints due to damage to the thermal head or the like, as described above.

[0013]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an electrical configuration when a thermal head to which the preheating method of the present invention is applied is mounted on a facsimile machine.

In FIG. 1, a buffer circuit 3 for matching transfer units and transfer speeds is connected to a modem 2 connected to a telephone line 1, and an output of the buffer circuit 3 is used to control the operation of the entire apparatus. It is connected to the CPU 4 that performs control. The CPU 4 stores an R in which an operation program is stored.
The OM 5 and the RAM 6 for temporarily storing received data are connected bidirectionally. In addition, the output of the preheating data creation circuit 10 for creating preheating data and the like is guided to the CPU 4 and the output of a temperature sensor 13 described later is guided to the CPU 4. The output of the temperature sensor 13 is A / D converted and taken into the CPU 4.

The output of the CPU 4 is a print pulse generating circuit 7 for outputting a strobe signal, a print data buffer 8 for outputting print data (line data) for one line.
And a data transfer clock generating circuit 9 for outputting a clock signal for data transfer.

On the other hand, the thermal head 11 has one line (for example, 1024) of heating resistance elements R1, R2,... Rn to each of which one terminal is supplied with a strobe signal from the print pulse generation circuit 7. A shift register 12 that outputs line data for printing to each of the other terminals of the heating resistance elements R1, R2,.
And a temperature sensor 13 composed of, for example, a thermistor for detecting the temperature of the entire head including the heating resistance elements R1, R2... Rn.
Line data which is an output of the print data buffer 8 and a clock signal from the data transfer clock generation circuit 9 are provided. That is, the shift register 12 sequentially transfers the applied line data according to the speed of the clock signal.

The preheating data generated by the preheating data generating circuit 10 is a continuous signal of a pulse indicating black data and a pulse indicating white data. Heating resistance elements R1, R2 ...
This signal is set to a length that does not cause the recording paper to develop color due to the heat generated by Rn. Specifically, for example, the heating resistance element R
When R1,..., Rn are driven in four divisions, the pulse width of each strobe signal for obtaining a sufficient density when the ambient temperature is about 20 degrees is about 1.5 ms.
The pulse width indicating the black data of the preheating data is 1/5 of that.
It is set to about 1/10 to about 200 to 300 μs.

In addition, the preheating data creation circuit 10 also generates heat radiation data indicating only white data and print data indicating only black data (data for performing full black printing described later). create. When such preheat data is given to the shift register 12, the shift register 12 sequentially transfers the preheat data according to the speed of the clock signal. Then, only the time when the black data stays in each storage location (configured by a binary element) of the shift register 12 is turned on, and the corresponding heating resistor element is heated, so that preheating is performed. The ON time at this time is a short time that does not cause the recording paper to develop color as described above.

Next, the operation of the facsimile apparatus having the above-described configuration will be described by dividing it into (1) a normal facsimile reception operation, and (2) an operation from power-on or immediately after the exchange of recording paper to preheating control. FIG. 2 is a timing chart at the time of the preheating operation, and FIG. 3 is an operation flowchart at the time of the preheating operation, which will be appropriately referred to in the description of the preheating operation.

(1) Normal Facsimile Reception Operation Image data sent from the other party's facsimile apparatus via the telephone line 1 is usually MH (Modifid Huffman).
The data is transmitted in a band-compressed state by an encoding method or an MR (Modifid Read) encoding method. The transmitted image data is converted into a digital signal by the modem 2, temporarily stored in the buffer circuit 3, taken into the CPU 4, and stored in the RAM 6.

In accordance with the operation program stored in the ROM 5, the band-compressed image data is decoded and converted into print data suitable for printing by the thermal head 11. That is, if one line is composed of 1728 heating resistance elements R1, R2,... Rn, and one set is divided into 432 four blocks, the 1728 heating resistance elements R1, R2 ... Rn
Are converted to 1728 line data of black (energized) or white (non-energized) corresponding to

The line data is written into a print buffer storage area (not shown) in the CPU 4. Thereafter, the written line data is transferred to the print data buffer 8 by serial communication, and transmitted from the print data buffer 8 to the shift register 12 by serial communication. The shift register 12 sequentially transfers the input line data according to the speed of the clock signal from the data transfer clock generation circuit 9.

On the other hand, when divided into four blocks, the print pulse generating circuit 7 sequentially outputs four strobe signals corresponding to each block to each block. As a result, when the strobe signal is in the ON state, the heating resistor element to which the signal (energization signal) indicating the black data is supplied from the shift register 12 generates heat, and the printing operation for one line is performed.

By repeating such a printing operation for one line for all line data of the transmitted data signal, image data is printed on the recording paper.

(2) Operation from Power-on or Immediately after Exchange of Recording Paper to Preheating Control First, the following conditions are set as preconditions for the preheating operation.
That is, since thermal paper, which is recording paper, usually develops color at about 70 degrees, in this embodiment, the upper limit temperature of preheating is set to 25 degrees in controlling the preheating operation. In addition, since the problem in the relationship between the communication speed of the facsimile and the printing speed is at a low temperature of 10 degrees or less, in this embodiment, the lower limit temperature of the preheating is set to 20 degrees.

The preheating operation is started under such conditions. That is, when the power of the facsimile machine installed at a predetermined place is turned on or the recording paper is replaced (step S1), the CPU 4 first checks whether or not the recording paper is loaded (step S2). ), A printing operation is performed on the recording paper so that the entire surface is black (step S3).

That is, at time t1 when the power is turned on, the CPU 4 causes the print pulse generation circuit 7 to output a strobe signal in an on state. Further, the CPU 4 reads out the print data (indicated by reference numeral 21 in FIG. 2C) indicating only the black data created by the preheating data creation circuit 10 and transfers the read data to the print data buffer 8. The print data 21 is continuously supplied to the shift register 12 so that all the heat generating resistance elements R1, R2
... Rn is driven for printing.

After such a printing operation is performed for a predetermined length or a predetermined time, the printing operation is stopped at time t2 (steps S4 and S5). Here, the certain length is the length of the black print portion on the recording paper. The certain time is a time required for the temperature of the thermal head 11 to reach an arbitrarily set specified temperature (for example, 75 degrees).

As a result, the recording paper is printed in black on the entire surface when the power is turned on or when the recording paper is replaced. Therefore, the user of the facsimile apparatus can visually check the black printing to make the thermal head 11 It is possible to check for missing printing due to damage or the like and to check the mounting state of the recording paper.

Thereafter, after confirming that the CPU 4 is on standby other than the printing operation (step S6), the CPU 4 keeps the strobe signal from the printing pulse generating circuit 7 in the ON state [see FIG. 2 (b)]. ], Each heating resistance element R1, R2
... Continue to supply to Rn (step S7). After this,
The CPU 4 detects the temperature of the thermal head 11 with the temperature sensor 1
3 is determined based on the temperature data. At this time (time t2), since the thermal head 11 has exceeded the upper limit temperature of preheating of 25 degrees, the operation proceeds from step S8 to step S12 in this case.

That is, the CPU 4 outputs heat release data indicating only white data from the preheat data creation circuit 10 [FIG.
(Indicated by reference numeral 22 in (c)) is transferred to the print data buffer 8, and the heat dissipation data 22 is continuously supplied from the print data buffer 8 to the shift register 12 to generate each of the heating resistance elements R1, R2,. Is in a heat radiation state. As a result, the temperature of the thermal head 11 exceeding the upper limit temperature gradually decreases due to the heat radiation effect from the time t2. This temperature drop is caused by the temperature sensor 1
The CPU 4 constantly monitors the temperature data provided by the CPU 3.

When the temperature of the thermal head 11 drops to the lower limit temperature at which preheating is required again at the time t3, the CPU 4 proceeds to the continuous preheating data of black and white created by the preheating data creation circuit 10 [FIG. (Indicated by reference numeral 23 in (c)) is again read and transferred to the print data buffer 8, and the preheat data 23 is continuously supplied from the print data buffer 8 to the shift register 12 so that each of the heating resistance elements R1, R2,. Preheating drive of Rn (steps S6, S7, S8, S9).

As a result, the thermal head 11 moves at time t.
The temperature gradually increases from 3. This temperature rise is constantly monitored by the CPU 4 based on temperature data provided from the temperature sensor 13. Then, when the temperature of the thermal head 11 reaches the upper limit temperature at which no preheating is required at time t4, the CPU 4 continuously supplies the heat release data 22 indicating only the white data to the shift register 12 again, and Element R1, R2 ... R
n is set to a heat radiation state (steps S10, S11, S1).
2).

As a result, the temperature of the thermal head 11 that has reached the upper limit temperature gradually decreases due to heat radiation from time t4. Hereinafter, step S
By repeating the operations of 6 to S12, the thermal head 11 is in the standby state other than the printing operation, regardless of the ambient temperature, regardless of the ambient temperature, the lower limit temperature of preheating is 20 degrees and the upper limit temperature is 25 degrees.
It will be controlled between degrees.

As a result, when the facsimile apparatus equipped with the thermal head 11 starts the receiving operation, even if the ambient temperature is low, since the thermal head 11 is already in a printable state, the communication speed is reduced. The combined real-time printing becomes possible.

According to the preheating method of the present invention, during the preheating operation, the strobe signal is always in the ON state, and only the operation of transferring the print data 21, the heat radiation data 22, and the preheat data 23 to the shift register 12 is sufficient. Therefore, the control for the preheating operation is also simplified.

In the above embodiment, the thermal head 1
When the temperature of No. 1 reaches the upper limit temperature that does not require preheating, the shift register 12 displays heat release data 2 indicating only white data.
2 is continuously supplied, but separately, the heat generating resistance elements R1, R2,... Rn can be set to a heat radiation state (non-operation state) by stopping a clock signal. It is possible. In the above embodiment, the lower limit temperature of preheating is set to 20 degrees and the upper limit temperature is set to 25 degrees. However, the present invention is not limited to these temperatures.

[0038]

The method of preheating a thermal head according to the present invention performs a black printing operation on a recording paper by performing a black printing operation for a predetermined length or for a fixed time immediately after the power is turned on or immediately after the recording paper is replaced. During the subsequent standby period, the printing operation is performed so that the recording paper does not develop color within the preset temperature range, so that the thermal head quickly rises to the predetermined temperature range. Time to complete the preheating of
Good printing operation can be performed even for facsimile reception immediately after the power is turned on. Also, since printing is performed entirely in black, it is possible to check for missing prints due to damage to the thermal head, etc.
This has the effect that the mounting state can be checked immediately after the replacement of the recording paper.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an electrical configuration when a thermal head to which a preheating method of the present invention is applied is mounted on a facsimile apparatus.

FIG. 2 is a timing chart during a preheating operation.

FIG. 3 is an operation flowchart during a preheating operation.

[Description of Signs] 10 Preheating data creation circuit 11 Thermal head 12 Shift register 13 Temperature sensor

Claims (1)

(57) [Claims] 1. A heating resistor element for one line to which a strobe signal for controlling an applied voltage is supplied to each of one terminals, and line data for printing is output to each of the other terminals of the heating resistor elements. When a power supply is turned on or immediately after the recording paper is replaced, a black print is made on the entire surface of the thermal head including a shift register that drives each heating resistor element and a temperature sensor that detects the temperature of the entire head including the heating resistor element. The operation is performed for a fixed length or for a fixed period of time to print black on the entire surface of the recording paper, and during the subsequent standby period, a printing operation that does not cause coloring of the recording paper is repeated so as to be kept within a preset temperature range. A method for preheating a thermal head.