JPH06255133A - Wire dot printer - Google Patents

Abstract

PURPOSE:To always perform printing of stable quality regardless of ambient temp. CONSTITUTION:A thermistor 62 measuring the circumferential temp. of a printing head 1 is provided and a pulse variable means is constituted of first and second one-shot ICs 61, 63 and an OR gate 64 and, when the circumferential temp. measured by the thermistor 62 is low, the ON-time of the head current supply pulse (a) outputted from an I/O port 56 is made long to supply the pulse (a) to a head driver 65.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wire dot printer for printing data by turning on / off the power supply to a print head.

[0002]

2. Description of the Related Art For example, a plunger type wire dot printer is provided with a print head composed of a plurality of wire dot pins and a plunger type solenoid corresponding to each wire dot pin, and a head generated based on print data. The solenoid is selectively energized by an energizing pulse to drive the wire dot pin, and a pixel is ejected at the tip of the pin to print data. Therefore, the time for the pixel ejection operation by the wire dot pin corresponds to the on time of the head energizing pulse.

In this type of conventional printer, the on time of the head energizing pulse is always constant. Therefore, when the air temperature is low, such as below freezing, the drive of the wire dot pin accompanying the energization of the solenoid becomes dull, and the pixel ejection operation time becomes shorter than the on time of the head energization pulse, resulting in a dark print. There was a chance

[0004]

As described above, in the conventional printer of this type, since the ON time of the head energizing pulse is always constant regardless of the temperature change, the print density is low at low temperature. Therefore, there is a problem that the print quality is deteriorated.

Therefore, the present invention is intended to provide a wire dot printer which can always print with stable quality regardless of fluctuations in ambient temperature.

[0006]

SUMMARY OF THE INVENTION According to the present invention, in a wire dot printer for printing data by turning on / off energization of a print head by a head energizing pulse generated based on print data, the ambient temperature of the print head is measured. Temperature measuring means and pulse varying means for varying the ON time of the head energizing pulse long when the ambient temperature measured by the measuring means is low.

[0007]

According to the present invention having such a configuration, when the ambient temperature is low and the ambient temperature of the print head measured by the temperature measuring means is low, the ON time of the head energizing pulse can be changed longer than when it is high. Therefore, the head energization time becomes longer than that at high temperature.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing a schematic configuration of a wire dot printer. This wire dot printer is
A print head 1 including a plurality of wire dot pins and a plunger-type solenoid corresponding to each wire dot pin, and a carriage on which the print head 1 is mounted is reciprocally moved in a direction orthogonal to a paper feeding direction to scan the print head 1. A carriage motor 2, a paper feed motor 3 for stepwise feeding the recording paper in a direction orthogonal to the scanning direction of the print head 1, and a ribbon feed for winding an ink ribbon interposed between the print head 1 and the recording paper. Motor 4 and controller 5 for controlling these to perform printing operation
Composed of.

The controller 5 includes a CPU (central processing unit) 51 constituting the control unit main body, and a program ROM in which program data to be executed by the CPU 51 is stored.
(Read-only memory) 52, CG (character generator) that stores dot patterns of various characters
-ROM 53, RAM (random access memory) in which an image memory for dot-developing print data is formed
54, an interface 55 for receiving print data output from the host device, and an I / O port 56 are connected by a bus line 57 such as an address bus and a data bus.

The print head 1 is connected to the I / O port 56 via the head drive circuit 6, and the motors 2, 3, 4 are connected to the motor drive circuits 7, 8, 9 respectively.
Connected through.

When the CPU 51 takes in the print data via the interface 55, it refers to the CG-ROM 53 and develops the print data into dots in the image memory of the RAM 54.
Then, the program is constructed so that the contents of the image memory are sequentially read out, a solenoid selection signal and a head energizing pulse are given to the print head 1, and the drive of each motor 2, 3, 4 is controlled to print data.

FIG. 2 is a block diagram showing a main configuration of the head drive circuit 6. This head drive circuit 6 is
The B input terminal is connected to the P1 output terminal of the O port 56, and when the input to this B input terminal rises to a high level, a pulse signal whose ON time is determined by the time constant of the fixed resistor r and the capacitor c1 is output to the Q output terminal. Output first one-shot IC (integrated circuit) 61 and the first one-shot IC
The A input terminal is connected to the Q output terminal of, and when the input to this A input terminal falls to the low level, a pulse signal is output from the Q terminal, the ON time of which is determined by the resistance of the thermistor 62 and the time constant of the capacitor c2. Second one-shot IC to do
63, and the Q output terminal of the second one-shot IC 63 is connected to one input terminal, and the I / O port 56
Is connected to the other input terminal, and an OR gate 64 for calculating the logical sum of inputs to both input terminals, and an output signal from the OR gate 64 are inputted as a head energizing pulse to the I / O port. A head driver 65 that energizes the solenoid selected by the solenoid selection signal output from the P2 output terminal of 56 for the on time of the head energizing pulse.

The thermistor 62 is attached to a carriage or the like for measuring the ambient temperature of the print head 1.

In the head drive circuit 6 having such a configuration, when the head energizing pulse a is output from the P1 output terminal of the I / O port 56, the first one is synchronized with the rising of the head energizing pulse a. A pulse signal b whose on-time is determined by the time constant of the fixed resistor r and the capacitor c1 is output from the Q output terminal of the shot IC 61. Then,
In synchronization with the fall of the pulse signal b, a pulse signal c is output from the Q output terminal of the second one-shot IC 63, whose on-time is determined by the time constant of the resistance value of the thermistor 62 and the capacitor c2. Then, the logical sum of the pulse signal c and the head energizing pulse a is calculated by the OR gate 64, and the head driver 65 is set as the head energizing pulse d.
Entered in.

Here, the head energizing pulse a output from the controller 5 via the I / O port 56 has a constant on-time. Further, the ON time of the pulse signal b output from the first one-shot IC 61 is also constant, and is set shorter than the ON time of the head energizing pulse a by the fixed resistor r and the capacitor c1.

On the other hand, the ON time of the pulse signal c output from the second one-shot IC 63 varies depending on the resistance value of the thermistor 62. That is, since the thermistor 62 has a characteristic that the resistance value increases as the temperature decreases, a pulse signal c having a relatively short ON time is output when the ambient temperature of the print head 1 is high, and the pulse signal c decreases as the temperature decreases. The on time of the signal c becomes long.

In this embodiment, when the ambient temperature of the print head 1 is low, the ON time T3 of the pulse signal c1 output from the second one-shot IC 63 is the head energizing pulse a as shown in FIG. 3A. 3 is set to be sufficiently larger than the width obtained by subtracting the on-time T2 of the pulse signal b output from the first one-shot IC 61 from the on-time T1 of the above, and to be decreased conversely as shown in FIG. Is set to the thermistor 62 and the capacitor c2.

Therefore, the ON time T of the head energizing pulse d output from the OR gate 64 is as shown in FIG.
As shown in (a), it becomes longer than the constant on-time T1 of the head energizing pulse a output from the controller 5,
At high temperature, as shown in FIG. 3B, it becomes equal to the constant ON time T1 of the head energizing pulse a output from the controller 5.

Here, the thermistor 62 constitutes temperature measuring means for measuring the ambient temperature of the print head 1, and the first and second
The one-shot ICs 61, 63 and the OR gate 64 constitute pulse changing means for changing the ON time of the head energizing pulse long when the ambient temperature measured by the thermistor 62 is low.

As described above, in this embodiment, when the ambient temperature of the print head 1 is low, the ON time of the head energizing pulse d supplied to the head driver 65 is changed longer than when it is high.

For example, the ON time T1 of the head energizing pulse a output from the controller 5 is set to 270 μs, and the first
The ON time of the pulse signal b output from the one-shot IC 61 is set to 255 μs. When the resistance value R at the measurement temperature of 0 ° C. is 30 kΩ and the resistance value R at the measurement temperature of 40 ° C. is 6 kΩ and the capacitor c2 is 2200 pF, the second one-shot I
ON time T3 of the pulse signal c output from C63 (=
k × c2 × R) is about 30μ when the measurement temperature is 0 ° C.
s, when the measurement temperature is 40 ° C., it becomes about 6 μs. In addition,
The constant k is an output pulse width constant determined by the one-shot IC, and is 0.46 in this embodiment.

Therefore, the pulse time T of the head energizing pulse d output from the OR gate 64 becomes 285 μs, which is the sum of the on time of the pulse signal b of 255 μs and the on time of 30 μs of the pulse signal c at the measurement temperature of 0 ° C. The on-time of the head energizing pulse a that is output is changed to be longer than 270 μs.

On the other hand, when the measured temperature is 40 ° C., the ON time 27 of the head energizing pulse a outputted from the controller 5 is longer than the time 261 μs in which the ON time 6 μs of the pulse signal c is added to the ON time 255 μs of the pulse signal b.
Since 0 μs is longer, it is equal to the on time 270 μs of the head energizing pulse a.

In the case of a wire dot printer, when the ambient temperature of the print head 1 becomes low, the drive of the wire dot pin becomes slow due to the energization of the solenoid, and the pixel ejection operation time is shorter than the on time of the head energization pulse. May be. However, in the present embodiment, since the ON time of the head energizing pulse is changed to be long at a low temperature, even if the time of the pixel ejection operation is shorter than the ON time of the head energizing pulse, printing of an appropriate density can be obtained. It is possible to secure the time for the pixel ejection operation. As a result, it is possible to obtain the effect that printing can always be performed with stable quality regardless of fluctuations in ambient temperature.

In the above embodiment, the pulse changing means is composed of the hardware of the one-shot ICs 61, 63 and the OR gate 64. However, the CPU 51 is constituted by digitally converting the signal from the thermistor 62 and fetching it. When the ambient temperature of the print head 1 is low, the on-time of the head energizing pulse may be automatically changed to be long by the software processing described above. However, it goes without saying that the hardware configuration as in the present embodiment can reduce the load on the controller 5 and can improve the processing efficiency.

[0027]

As described above in detail, according to the present invention, the ambient temperature of the print head is measured by the thermistor, and when the ambient temperature is low, the ON time of the head energizing pulse can be varied for a long time. Thus, it is possible to provide a wire dot printer that can always print with stable quality regardless of fluctuations in ambient temperature.

[Brief description of drawings]

FIG. 1 is a block diagram showing a schematic configuration of an embodiment of the present invention.

FIG. 2 is a block diagram showing a main configuration of a head drive circuit shown in FIG.

FIG. 3 is a timing chart showing main signal waveforms of respective parts shown in FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Print head, 5 ... Controller, 61, 63 ... 1st, 2nd one-shot IC (pulse changing means), 64 ... OR gate (pulse changing means), 62 ... Thermistor (temperature measuring means).

Claims (1)

[Claims] 1. A wire dot printer for printing data by turning on / off energization of a print head by a head energizing pulse generated based on print data, and temperature measuring means for measuring an ambient temperature of the print head. A wire dot printer comprising pulse changing means for changing the ON time of the head energizing pulse long when the ambient temperature measured by the measuring means is low.