JPH07304204A - Thermal recording control method - Google Patents

Abstract

PURPOSE:To suppress temperature increase of a thermal head to properly keep a printing density by a method wherein when the temperature of the thermal head is increased, a printing strobe pulse for driving the thermal head is made intermittent within a predetermined printing strobe pulse width. CONSTITUTION:A head temperature value 2a detected by a head temperature detection means (sensor) 2 is inputted to a strobe signal control means 3. In this control means 3, on the basis of the head temperature value 2a, a printing strobe signal 3a and a stepping motor exciting signal 3b are respectively transmitted to a heating resistor drive circuit 4 and a stepping motor drive circuit 6. At this time, if a head temperature is high, the strobe pulse control means 3 generates and issues a pulse signal, that is reduced to zero only in a pulse stop period T2 within a period of a pulse width T1 of a printing strobe signal 3a, thereby suppressing the temperature increase of a thermal head and always keeping a printing density proper.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-sensitive recording control method for controlling an improper print density due to a temperature rise of a heat-sensitive head.

[0002]

2. Description of the Related Art A device such as a facsimile machine for recording with a thermal head is widely used. The thermal recording by such a thermal head operates as follows. That is, in the case of a facsimile or the like, the print data signal and the print strobe signal for one scanning line, which are received via a communication line or the like and are stored in the RAM, are arranged corresponding to one scanning line of the thermal head. By adding to the heating resistor, the resistor of the thermal head is heated and driven, and one scanning line is recorded on the recording paper. More specifically, a print data signal (for example, "H" level when it is desired to record heat on a heating resistor at a certain position to record black, or "1", and when it is desired to record white without heat generation, "L" level , Or "0") and a print strobe signal (for example, when recording to a thermal head, the signal is "H" level, or "1")
Since each heating resistor of the thermal head operates by the logical product of and, only the heating resistors whose input print data signal is "1" generate heat during the period of the print strobe signal being "1" and the recording paper is black. It will be recorded in. As described above, the heating resistor is caused to generate heat by passing a current according to the print data signal through the thermal head during the printing strobe period, and the heat causes the thermal recording paper to develop color. In order to obtain an appropriate density of color development, it is necessary to use energy of, for example, about 0.5 millijug per heating resistor, but there is a limit to the capacity of the power supply and drive circuit, so all heating resistors should be It cannot be driven at one time. For example, when it is desired to record the print data in almost black over one scanning line, it is inconvenient because most of the heating resistors of the thermal head are driven at once. Therefore, by dividing into several blocks (for example, 2, 4, 8 divisions) and sending the print strobe signal in sequence, even if there are many black recordings, for example, in the case of 4 divisions, the maximum is 1/4. Since the electric power can be limited, the configuration in which the division driving is performed is general. In the following, a configuration in which the blocks are divided into four blocks B1 to B4 will be described as an example.

FIG. 4 shows the timing relationship between the print strobe signal for each block B1 to B4 in the case of one line scanning period and four divisions in the conventional thermal recording, and the timing of the excitation signal of the stepping motor. In the figure, the print strobe signal 10a having the standard pulse width Tst at the standard head temperature is shown.
However, the first block B1 to the fourth block B of the thermal head
One line is printed by sequentially driving up to 4.

The print strobe cycle and the stepping motor excitation cycle are set in synchronization with each other, and in synchronization with the two print strobe signals 10a and 10a for driving the first and second blocks (B1 and B2). One stepping motor excitation signal 10b (Nth order in the figure) is driven. Further, in synchronization with the two print strobe signals 10a, 10a for driving the third and fourth blocks (B3 and B4), the next one stepping motor excitation signal 10b is generated.
(N + 1 order in the figure) is driven. With this timing, proper print density and proper paper feeding without print distortion or step out are realized.

[0005]

By the way, when the thermal head temperature is in an appropriate state, an appropriate print density can be obtained under this driving condition. However, if the thermal head temperature rises, the print density increases, and if If the head temperature rises excessively, the print density becomes excessive and the image quality deteriorates.

Therefore, conventionally, as shown in FIG. 5, the pulse width Thi of the print strobe signal 11a at a high head temperature is made shorter than the standard pulse width Tst, and the print strobe cycle is shortened, so that the power to the thermal head is reduced. Attempts have been made to reduce the input amount to prevent the head temperature from rising and improve the print density. However, as is clear from the figure, the stepping motor excitation period 11b is also shortened, so the stepping motor and drive The mechanism could not follow, so that there was a problem such as print distortion due to insufficient paper feed due to step out. Further, there is a method of using a high-order specification stepping motor and a drive mechanism that follows it, but the cost is increased.

The present invention solves such a problem, and its purpose is to suppress an increase in the temperature of the thermal head to maintain an appropriate print density, and at the same time, cause a step out or a distortion by a conventional stepping motor. It is another object of the present invention to provide a method for controlling thermal recording that can realize proper printing without any problem.

[0008]

In order to achieve the above object, a thermal recording control method according to the present invention drives a stepping motor that feeds a recording sheet at a predetermined stepping motor excitation period, and the predetermined stepping motor excitation period. In the method of controlling the thermal recording in which the thermal head is driven by the logical product of the print strobe signal of the predetermined width and the print data signal sequentially input during the period of the print strobe cycle synchronized with When the voltage rises above a predetermined value, the predetermined width signal output is made zero within the predetermined width printing strobe signal period.

[0009]

When the temperature of the thermal head rises, the thermal recording control method according to the present invention has a predetermined width print strobe signal during a predetermined print strobe cycle. Since there is a period during which the signal becomes zero, the thermal head is not driven during the period of zero, and the thermal head is not driven, resulting in intermittent drive. As a result, the temperature rise of the thermal head is suppressed, the print density is maintained properly, and at the same time, the predetermined stepping motor excitation cycle is also maintained, and it is not necessary to shorten the motor excitation cycle depending on the print density, so that proper paper feeding is possible. Maintained.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will now be described with reference to FIGS.
It will be described with reference to FIG. FIG. 1 is a timing chart for explaining a thermal recording control method according to an embodiment of the present invention. FIG. 2 is a perspective view of a main part of a thermal printing apparatus that implements the control method of the present invention, and FIG. 3 is a block configuration diagram of the thermal printing apparatus that implements the control method of the present invention.

FIG. 2 is a perspective view of a main part of the thermal printing apparatus 1 for carrying out the control method of the present invention. The recording paper 9 is arranged on the platen roller 8, and the platen roller 8 is rotated by the driving of the stepping motor 7. As a result, the recording paper 9 is fed in the paper feed direction W. Each block B1 of the thermal print head 10 for pressing the recording paper 9 against the platen roller 8 from above
.About.B4 are sequentially driven to generate heat and color the recording paper 9. Since the paper is slightly fed during this period, dots having a predetermined area are printed on the recording paper 9. A head temperature sensor 2 attached to the thermal print head 10 detects the temperature of the print head.

FIG. 3 is a block diagram of the thermal printer 1 for carrying out the control method of the present invention. Head temperature value 2a detected by the head temperature detecting means (sensor) 2
Is received by the strobe signal control means 3. The strobe signal control means 3 sends the print strobe signal 3a to the heating resistor drive circuit 4 and the stepping motor excitation signal 3b to the stepping motor drive circuit 6 based on the head temperature value 2a. The heating resistor drive circuit 4 is based on the print strobe signal 3a and the print data signal 5a.
The print head blocks B1 to B4 are sequentially driven. When the head temperature is high, the strobe pulse control means 3 creates and outputs a pulse signal in which the signal is zero during the pulse stop period T2 adapted to the state during the pulse width T1 of the print strobe signal 3a. .

Referring to FIG. 1, in a thermal recording control method according to an embodiment of the present invention, a stepping motor for feeding a recording sheet is driven for a predetermined stepping motor excitation period T3 and synchronized with the predetermined stepping motor excitation period T3. The thermal head is driven with the pulse width T1 of the print strobe signal 3a. That is, the stepping motor excitation period T3 is set to twice the pulse width T1 of the print strobe signal 3a. In this stepping motor excitation period T3, the stepping motor is driven by the 1-pulse stepping motor excitation signal 3b. Further, when the temperature of the thermal head rises and the print density increases, a pulse stop period (signal zero period) T2 is provided within the pulse width T1 of the print strobe signal 3a for driving the thermal head. .

That is, the pulse stop (zero signal) period T
Only 2 is set to zero within the pulse width T1 period of the print strobe signal 3a. As a result, the amount of electric power applied to the thermal head is reduced, the temperature rise of the thermal head is suppressed, and the pulse width T1 of the print strobe signal 3a is maintained. As a result, the predetermined stepping motor excitation period T3 synchronized with the pulse width T1 of the print strobe signal 3a can also be maintained. As a result, the print density is properly maintained, and at the same time, proper paper feeding is also maintained. Therefore, print unevenness and print distortion can be eliminated.

[0015]

As described above, the method for controlling heat-sensitive recording according to the present invention, when the temperature of the heat-sensitive head rises,
Since the print strobe pulse for driving the thermal head is intermittent within the predetermined print strobe pulse width, the temperature rise of the thermal head is suppressed by this, and the print density is maintained at the same time, and at the same time, the predetermined print strobe pulse is obtained. By maintaining a predetermined stepping motor excitation cycle that is synchronized with the cycle, proper paper feeding is maintained. As a result, it is not necessary to use a high torque stepping motor, and it is possible to realize good printing quality with an inexpensive popular type stepping motor.

[Brief description of drawings]

FIG. 1 is a timing diagram illustrating a method of controlling thermal recording according to the present invention.

FIG. 2 is a perspective view of a main part of a thermal printing apparatus that implements the control method of the present invention.

FIG. 3 is a block configuration diagram of a thermal printing apparatus that implements the control method of the present invention.

FIG. 4 is a timing diagram illustrating a conventional method for controlling thermal recording.

FIG. 5 is a timing diagram illustrating a conventional method of controlling a high temperature head for thermal recording.

[Explanation of symbols]

 3a Print strobe signal to each block 3b Stepping motor excitation signal T1 Pulse width of print strobe signal T2 Zero signal width in pulse width T1 Stepping motor excitation period B1 to B4 Thermal head block

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[Procedure amendment]

[Submission date] September 1, 1994

[Procedure Amendment 1]

[Document name to be corrected] Drawing

[Correction target item name] All drawings

[Correction method] Change

[Correction content]

[Figure 1]

[Fig. 2]

[Figure 3]

[Figure 4]

[Figure 5]

Claims (1)

[Claims] 1. Print data for driving a stepping motor for feeding a recording sheet at a predetermined stepping motor excitation cycle, and sequentially inputting a print strobe signal of a predetermined width during a print strobe cycle synchronized with the predetermined stepping motor excitation cycle. In a method of controlling thermal recording in which a thermal head is driven by a logical product of a signal and a signal, when the temperature rises above a predetermined value by a temperature detecting means of the thermal head, a predetermined width signal within the predetermined width print strobe signal period is output. A method for controlling thermal recording, characterized in that the output is set to zero.