JPH05112018A - Method for supplying electricity to head of impact printer - Google Patents

Abstract

PURPOSE:To improve the difference in density of printing generated when switched to a driven period which is longer than an ordinary printing period caused by restriction on temp. rise a printing head. CONSTITUTION:A printing head 50 is detected by means of a temp. detecting device 51 and in accordance with extension of a printing period transmitted from a printing control part 31 when temp. reaches a specified temp., a printing wire speed by which the same printing concn. as that at an ordinary printing period pulse 32. As it is possible thereby to obtain a printing wire speed by which the same density obtd. even if the driving period is switched, no difference in the printing density is generated thereby.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for energizing a print head of an impact printer.

[0002]

2. Description of the Related Art In a print head of an impact printer, a voltage is applied to a drive coil to excite or demagnetize the print coil to selectively eject a print wire for printing. At this time, since the drive coil generates heat, a temperature detection means is provided to prevent the drive coil from being burned due to a large amount of printing.
When the temperature reaches a predetermined temperature, the printing cycle is lengthened to limit the printing amount and prevent the temperature from rising.

[0003]

However, as shown in FIG.
As shown in (a), in the normal printing cycle, during continuous printing, when the print wire reciprocates and collides with the damper member and rebounds, the timing of the next energization coincides, so the rebound speed becomes the printing speed of the next print wire. In addition, the printing wire speed after the second shot is increased and high density printing can be obtained. On the other hand, as shown in FIG. 6B, when the printing cycle becomes longer due to the temperature rise, the rebound speed does not coincide with the next energization timing, so that the rebound speed is not added and the printing becomes thin. Therefore, there is a problem that a print density difference occurs when the print cycle is switched. Particularly at high temperatures, the damper member made of resin is softened and rebound becomes large, resulting in a significant difference in concentration, which is a problem.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to solve the above problems and to provide an impact printer in which a print density difference does not occur even if the print cycle becomes longer during printing due to temperature rise.

[0005]

SUMMARY OF THE INVENTION The head energizing method for an impact printer according to the present invention is provided with a print head for applying a voltage to a drive coil for a predetermined energizing time to drive a print wire for printing. The temperature detecting means is provided, and the printing cycle becomes longer and the energization time becomes longer at a predetermined temperature.

[0006]

In the above impact printer, when the printing cycle is long and the rebound speed is not applied, the energization time is long and the printing speed is high, so that the same printing wire speed as before the printing cycle is long can be obtained. As a result, it is possible to obtain good print quality without causing a print density difference.

[0007]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view of a print head according to a first embodiment of the present invention, FIG. 2 is a schematic view of the first embodiment of the present invention, and FIG.
FIG. 3A is a diagram showing a normal state, FIG. 3B is a diagram showing an energization time when a temperature rises, a current flowing through a drive coil, a displacement of a print wire, and a speed in the first embodiment. The structure of the print head 50 in FIG. 1 will be described. The armature 6 to which the print wire 2 slidably held by the wire guide 1 (which has a large number of print wires, but one print wire and its drive section are shown for convenience in the drawing) is
It is rotatably held on the fulcrum shaft 3. The fulcrum shaft 3 is sandwiched between the yoke A13 and the holder 11 with a metal spacer 19 having high wear resistance interposed therebetween, and is positioned by the yoke B14. The yoke A13 is in contact with the frame 12, and the core 5 is circumferentially arranged on the frame 12 and integrated with the frame 12. Coil bobbin 17 on core 5
The drive coil 4 wound on the substrate is inserted, soldered to the substrate 15, and connected to the driver circuit 30 through the flexible printed board 16. The temperature detecting means 51 is adhered to the outer periphery of the frame 12 by a heat conductive resin 53 such as silicon rubber, and is connected to the print control section 31 shown in FIG. In this embodiment, a thermistor is used as the temperature detecting means 51.
The heat dissipation member 52 is joined to the outer periphery of the frame 12 with a heat conductive resin such as silicon rubber. The armature 6 is pressed by the return spring 10 during standby and is positioned by the damper 18 made of resin supported by the holder 11.

Next, the printing operation and the energizing method will be described with reference to FIGS.

In a normal printing state in which continuous printing with the printing cycle T1 is possible, the energizing pulse 32 is set to the H level by the print controller 31 for a predetermined energizing time A1, and the transistor 33 is provided.
When is turned on, the voltage of the power supply 34 is applied to the drive coil 4 and the current I1 flows, and when the energizing pulse 32 becomes L level, the current I1 flows through the flyback circuit composed of the Zener 35, the transistor 33, and the diode 36, and the current value sharply increases. Goes down. A magnetic flux is generated in the drive coil 4 by this current I1, and the core 5, the frame 12, the yoke A13, and the yoke B1 are generated.
4. A magnetic flux flowing through the armature 6 in a closed loop flows, the armature 6 is attracted to the core 5, the print wire 2 projects, and the print medium 9 supported by the platen 8 via the ink ribbon 7
And collide with and print. After printing, the printing wire 2 collides with the damper 18 due to the repulsive force at the time of collision and the spring force of the return spring 10 and returns to the standby state after rebound, but during continuous printing, the energizing pulse 32 is turned on during rebound and the printing wire 2 projects. Rebound speed is added, and Fig. 3
As shown in (a), the printing wire speed increases after the second shot.

When a large number of prints are made, the temperature of the print head 50 rises, but the temperature detecting means 51 detects that the print head 50 has reached a predetermined temperature, and the print control section 31 sets the print cycle to T2 and switches the energization time to A2. At this time, T1 <T
2, and A1 <A2. By increasing the rate of increasing T2 rather than the rate of increasing A2, it is possible to reduce the amount of heat generation and prevent an increase in temperature.

By setting A1 <A2 in this way, the magnetic flux generated in the drive coil 4 becomes large, so the print wire 2
The printing wire speed of the printing wire 2 remains the same even if the printing cycle becomes longer due to the temperature rise as shown in FIG. 3 (b). It is possible to obtain excellent print quality.

When printing ordinary characters, not all printing wires continuously print, so the speed of the first printing wire in normal printing is v1, and the second and subsequent printing wires in continuous printing. The print wire speed v3 when the temperature rises is set in the range of v1 <v3 <v2, and uniform print quality can be obtained.

FIG. 4 is a schematic diagram of a second embodiment of the present invention, FIG. 5 is a diagram showing the second embodiment (a) is a normal state, (b) is an energizing time when the temperature rises, and a current flowing through the exciting coil. FIG. 3 is a diagram showing the displacement and speed of a printing wire. Since the print head is the same as the head shown in FIG. 1, this embodiment will be described based on FIGS. 1, 4, and 5.

The driver circuit 30 includes a transistor 38 for controlling the energization time B1 for applying the voltage of the power supply 34 to the drive coil 4 and a transistor 39 for controlling the time C1 during which the current flows through the first flyback circuit. Have The energization time B1 is changed by the voltage detection unit 37 according to the voltage so that the printing wire speed becomes constant. When the energizing pulse 41 is at the L level and the energizing pulse 42 is at the H level at the same time, the transistors 38 and 39 are turned on.
N, the voltage of the power supply 34 is applied to the drive coil 4,
A current I3 flows through the drive coil 4. When the energizing pulse 41 becomes H level after the time B1, the transistor 38 is turned off.
Then, the current I3 flows through the first flyback circuit that goes around the drive coil 4, the transistor 39, and the diode 40. When the energizing pulse 42 becomes L level after the time C1, the drive coil 4, the Zener diode 43, and the transistor 3
9. The current I3 flows through the second flyback circuit that goes around the diode 40, and the current value decreases sharply due to the action of the Zener diode 43 as compared with when the current flows through the first flyback circuit.

A magnetic flux is generated in the drive coil 4 by this current I3, the armature 6 is attracted to the core 5, and the printing wire 2 projects and collides with the printing medium 9 supported by the platen 8 via the ink ribbon 7 to perform printing. After printing, the printing wire 2 collides with the damper 18 due to the repulsive force at the time of collision and the spring force of the return spring 10 and returns to the standby state after rebound, but during continuous printing, the rebound and energizing pulses 41 and 42 turn on the transistors 38 and 39. Since the timing overlaps, the rebound speed is added, and the printing speed increases after the second shot. In this embodiment, since the energization time B1 changes in accordance with the voltage fluctuation so that the printing wire speed becomes constant, it is possible to obtain printing without shading with respect to the voltage fluctuation.

When a large number of print wires are driven, the temperature of the print head 50 rises, but the temperature detecting means 51 detects that the print head 50 reaches a predetermined temperature, and the print control section 31 sets the print cycle to T3. At this time, the energization time B1 does not change and only C1 switches to C2. At this time, T1 <T3, and
C1 <C2. The currents flowing through the first and second flyback circuits do not consume the power of the power supply 34 because they are supplied from the magnetic energy stored in the drive coil 4.
Therefore, the energization time C1 of the first flyback circuit is set to C2.
Since B1 does not change even if it is set to be extremely long, the power consumption per print does not change, and the power consumption can be reduced. Further, by increasing C1 to C2, the current I4 flowing through the drive coil 4 increases and the printing wire speed also increases, so that it is possible to obtain the same print density as in the normal state, and the print density difference does not occur. Further, since the energization time B1 changes with the voltage so that the print density becomes constant, it is possible to obtain a print with no difference in the print density even when the voltage changes, and to obtain a uniform print in any use situation. You can Further, since the value of the energization time B1 with respect to the fluctuation of the voltage is the same regardless of the driving cycle, it can be realized by a simple circuit.

Although a thermistor is used as the temperature detecting means in this embodiment, it is not particularly limited as long as it can detect the temperature. For example, a method of detecting the temperature by changing the resistance value of the drive coil is also possible.

[0019]

As described above, according to the present invention, since the print driving cycle becomes longer and the energization time becomes longer due to the temperature rise, the print density difference does not occur and good print quality can be obtained.

[Brief description of drawings]

FIG. 1 is a sectional view of a print head according to a first embodiment of the present invention.

FIG. 2 is a schematic view of the first embodiment of the present invention.

FIG. 3A is a diagram showing a normal state in the first embodiment of the present invention, and FIG. 3B is a diagram showing an energization time at a temperature rise, a current flowing through a drive coil, a displacement of a print wire, and a speed.

FIG. 4 is a schematic diagram of a second embodiment of the present invention.

5A is a diagram showing a normal state, and FIG. 5B is a diagram showing an energization time at a temperature rise, a current flowing through an exciting coil, a displacement of a printing wire, and a speed in the second embodiment of the present invention. ..

FIG. 6A is a diagram showing a normal state, FIG. 6B is a diagram showing an energization time at a temperature rise, a current flowing through an exciting coil, a displacement of a printing wire, and a speed.

[Explanation of symbols]

 2 printing wire 4 driving coil 30 driver circuit 31 printing control section 37 voltage detecting means 50 print head 51 temperature detecting section

Claims (1)

[Claims] 1. A print head for applying a voltage to a drive coil for a predetermined energizing time to drive a print wire and performing printing, and a temperature detecting means for the print head. A method for energizing a head of an impact printer, which is characterized in that energization time is extended.