JPH02219660A - Printer - Google Patents

Abstract

PURPOSE:To obtain a printer of excellent printing quality by preventing printing density of copying paper from decreasing at low temperature by a method wherein the title printer is so constructed that different time is established according to a value detected with a temperature detecting device arranged near a printing platen. CONSTITUTION:A thermistor 1 is arranged near a printing platen 3. When use environment of a printer reaches low temperature, the thermistor detectors the temperature and its resistance value is varied. Electric potential between the resistance value and a value of a resistor 2 is compared with reference voltage to be given by resistors Ra1,..., Ran..., Rb1..., and comparator C1,..., Cn is selectively outputted according to the detected temperature. Then, output of the comparator C1,..., Cn is read with an input port 9 before printing operation, and a temperature condition near a printing platen 3 is grasped. Then a value preliminarily established according to the value is written in a timer, and a printing data is written in a register 13. Thereafter, by actuating the time 12, time while a transistor 15 and Tr1,..., Trn are being on is altered by the time established with the timer 12. Therefore, ample printing density can be obtained at low temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a printer, and particularly to a printer with good printing characteristics at low temperatures.

(Prior Art) Conventionally, wire dot printers, which drive a print wire to strike a print medium through an ink ribbon and use that force to print on the print medium, are relatively inexpensive and can print on many types of print media. Because it can perform the following functions, it is used in many fields including output devices of information processing systems and the like.

In the print head of the wire dot printer, the dot pin solenoid is generally energized so that it can print on about 4 to 6 sheets of copy paper. When printing on a thin medium such as single paper, the energization time can be set short to increase the printing speed, and when printing on copy paper or thick media, the energization time can be set longer.

(Problem to be Solved by the Invention) However, in the conventional printer described above, when using copy paper, it is possible to set the solenoid energization time for the dot pin to be long, but it is difficult to respond to changes in the usage environment of the printer. It is not possible to set the energization time sufficiently; in other words, at low temperatures, not only the temperature characteristics of the carbon used in the copying medium of the copy paper changes, but also the frictional resistance of the dot pin increases. Unable to obtain sufficient print density.

Therefore, when used in winter or in a cold region, printing may fade at the start of operation.

In response to this, a device has been proposed in which the printing speed can be slowed down or sped up in multiple stages according to the heat generation temperature of the print head (Japanese Patent Laid-Open No. 17257/1983).
(Refer to Publication No. 3), the slow speed control is performed by a print head containing a thermistor and a microprocessor that controls the print head. When the temperature of the print head increases due to heat generation, the print duty decreases and the print time is shortened.

However, since the slow speed control described above is intended to prevent damage to the print head itself due to heat generated by the print head, it cannot cope with changes in print characteristics when used in winter or in cold regions.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned problem that the print density of copy paper decreases at low temperatures and to provide a printer with excellent print quality.

(Means for Solving the Problems) For this purpose, the present invention provides a printer that performs printing by selectively driving a plurality of dot pins by applying current to a solenoid of a print head based on print data stored in a register. A temperature detection element is disposed near the printing platen, and different times are set depending on the value detected by the temperature detection element.

Then, as the temperature detected by the temperature detection element becomes lower, the energization time of the current flowing through the solenoid is changed by the set time, and the dot pin driving force is increased.

(Function) According to the present invention, a temperature detection element is disposed near the printing platen, different times are set according to the value detected by the temperature detection element, and the solenoid of the print head is activated for only the set time. When the energization time of the flowing current is changed and the temperature in the vicinity of the platen decreases, the driving force of the print head is increased, so that it is possible to prevent a decrease in the driving force of the print head due to a decrease in temperature.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

Fig. 1 is a circuit diagram of a printer showing an embodiment of the present invention, Fig. 2 is a perspective view of the print head section showing the thermistor installation location, Fig. 3 is a drive current waveform diagram of the print head, and Fig. 4 is a diagram of the print head drive current waveform. FIG. 3 is a flow diagram showing the operation of the print head.

In FIG. 1, l is a temperature detecting element, such as a thermistor, placed near the printing platen, and 2 is the thermistor 1.
This is a resistor installed in series with .

Resistance Raj 1''+ Ra6 is resistance Rh, , ・
, Rb, and the comparator C1
, . . . A reference voltage of l cm is formed. The comparators C1, . and constitutes n circuits.

The thermistor 1 is connected to the printing platen 3 as shown in FIG.
The temperature of the printing medium 4 such as copy paper is indirectly measured.

9 is an input port for inputting the outputs of the comparators C+, . . . , Cn, and the comparators C1+, .
..., n input signal terminals P+ according to the number of outputs of Cn.

...It is equipped with P. 10 is a microprocessor, and 11 is a memory that stores programs for the microprocessor 10.

Reference numeral 12 is a timer for controlling the time of the output signal according to instructions from the microprocessor 10, and reference numeral 13 is a register for temporarily storing print data. The timer 12 has an amplifier 1
4 are connected.

15 is a transistor for supplying current to the print head 16 for a certain period of time. The transistor 15 is connected to the print head 16 solenoid 31 . ...1 g+11, and is turned on according to the output from the amplifier 14 to send a drive current to the solenoid S+,...l ss, where m indicates the number of head pins of the print head, and , 1 transistor Tr++ is provided for each solenoid Sr, .

Therefore, the solenoid 51. . . . The printing waveform of ss is controlled by the transistor 15 and Tr, . . . + Trlj.

By the way, in the printer configured as described above, when the environment in which the printer is used becomes low temperature, the thermistor 1 detects the temperature and its resistance value changes. The potential between them determined by the resistance value of the thermistor l and the value of the resistor 2 is the resistance Rat,
. . . l Ra and the reference voltages provided by resistors Rbl, . . . Rh, and the comparators C1+ .

Here, before starting the printing operation, the outputs of the comparators C1, . . . , lCn are read by the input port 9,
The temperature state in the vicinity of the print platen 3 can be known at the 0th order, and a preset value is written into the timer 12 based on that value, and print data is written into the register 13.

Thereafter, by starting the timer 12, the time during which the transistors 15 and Tr+, . . . +Trwa are on is changed by the time set by the timer 12. That is, the transistor 15 and the transistors Trl, . Perform printing operation.

FIG. 3 shows the print head drive current waveform obtained in the printer configured as described above.

As shown in the figure, the write value T of the timer 12,...T
, the current waveform changes. That is, the temperature detected by the thermistor 1 installed near the printing platen 3 becomes low, and the value written by the timer 12 becomes i.

When it changes from T to T, the ON time of the transistor 15 and the transistors Tr++...+Tr becomes longer, and the striking operation time of the dot pin becomes longer, so that a stronger driving force can be obtained. FIG. 3(a) shows a current waveform when the on-times of the transistors Tr++, . . . , Tra are constant and the on-time of the transistor 15 is made variable. In addition, FIG. 3(b) shows the transistor 1
While keeping the on time of transistor 5 constant, the transistor Tr,
,...+ This is a current waveform when the on-time of Trs is made variable.

The above-mentioned detection of the temperature state and setting of the timer 12 are repeated for each new line.

FIG. 4 shows a flowchart for controlling the energization time. Comparators C8, . . . C, are selectively turned on according to the temperature, and their outputs are
．． ... +Pa is input. The input port P+,・
. . l ta The timers Tin, .

Note that the present invention is not limited to the above embodiments (
Various modifications are possible based on the spirit of the present invention, and these are not excluded from the scope of the present invention.

(Effects of the Invention) As explained above, according to the present invention, the energization time of the solenoid of the print head is controlled depending on the ambient temperature condition of the print platen, and the operating force of the dot pin can be controlled, so high-speed operation is possible. Moreover, it is possible to realize a printer that can obtain sufficient print density even at low temperatures.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram of a printer showing an embodiment of the present invention, Figure 2 is a circuit diagram of a printer showing an embodiment of the present invention.
FIG. 3 is a perspective view of the print head section showing the locations where the thermistors are installed, FIG. 3 is a drive current waveform diagram of the print head, and FIG. 4 is a flow diagram showing the operation of the print head. DESCRIPTION OF SYMBOLS 1... Thermistor, 2... Resistor, 3... Printing platen, 4... Printing medium, 9... Input port, 10...
...Microprocessor, 11...Memory, 12...
・Timer, 13...Register, 16...Print head. Patent Applicant: Oki Electric Industry Co., Ltd. Agent, Patent Attorney: Makoto Kawai (1 other person) Figure 4

Claims (1)

[Scope of Claims] In a printer that prints by applying current to a solenoid of a print head and selectively driving a plurality of dot pins according to print data stored in a register, there is provided a printer that (a) is arranged near a printing platen; (b) means for setting different times according to the value detected by the temperature detection element; and (c) means for setting different times according to the value detected by the temperature detection element; 1. A printer comprising means for increasing dot pin driving force by changing the energization time of a current flowing through a solenoid.