JPH0313353A - Impact dot head - Google Patents

Abstract

PURPOSE:To print at a high speed in a stably printing quality and to reduce power supply energy by so altering printing time that the printing force of a printing wire becomes constant in response to a voltage value applied to a driving coil, and maintaining the sum of time for applying a voltage to the coil and time for supplying a current of the coil to a first flyback circuit constant irrespective of the voltage. CONSTITUTION:A current flowing to a driving coil 4 rises at a current I1 at time T1 in which the voltage of a power source 38 is applied to the coil 4, falls at a current I2 at time T2 in which a first flyback circuit is turned ON, and abruptly falls from the I2 when a current I3 flows to a second flyback circuit. Since the voltage E applied to the coil 4 is varied according to an irregularity in the component rating of the source 38, variation due to temperature and a decrease in an applying voltage due to an increase in capacity, only the time T1 is altered according to the voltage E to obtain a predetermined impact force, and (T1+T2) is maintained constantly.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to energization conditions for an impact dot head of an impact printer.

[Conventional technology]

The impact dot head selectively protrudes the printing wire by energizing the drive coil and attracting excitation, and prints using the impact force when the printing wire collides with the printing medium. Figure 9 shows the impact dot head. A schematic diagram is shown.

When the drive coil 101 is energized by the driver circuit 100, the core 102, yoke 103, and armature 104
The magnetic flux is mixed up, the armature 104 is attracted to the core 102 and rotates around the fulcrum 105, and the printing wire 106 that is in contact with the tip of the armature 104 protrudes and collides with the printing medium 109 via the ink ribbon 108. Print a dot. After printing, the printing wire 108 returns to the standby position by the reaction force at the time of collision and the return force of the return spring 107.

Conventionally, the driving method of the drive coil 101 has been a constant voltage driving method such as the current wave carving shown in FIG. 10(a). FIG. 10(b) shows an example of such a constant voltage driver circuit 100. In response to a print command, the energizing pulse 110 becomes H level, the transistor 111 is turned on, and the voltage E is applied from the power supply 114 to the drive coil 101. When the energization pulse 110 becomes L level after 0 energization time Tw when current flows through the drive coil 101, the transistor 1
11 is 0FFL, the back electromotive force generated at this time is absorbed by the Zener diode 112 and the transistor 113, and the current flowing through the drive coil 101 falls sharply.

The energization time Tw varies depending on the fluctuation of the voltage applied to the drive coil in order to obtain a constant impact force.Tw is longer when the voltage is low. Tw must be changed so that Tw becomes shorter when the voltage increases.

[Problem to be solved by the invention]

However, there is a problem in that when the current application time Tw becomes long at low voltage, the return of the printing wire 106 is delayed due to residual magnetic flux.

As shown in FIG. 11, when Tw becomes longer, the printing wire 106 hits the printing medium 109 (even when the core 106 hits the printing medium 109).
2. Since the magnetic flux Φ remains between the armatures 104 and the attraction continues, the return of the print wire 106 is delayed, and the print wire 106 does not return until the next energization starts, resulting in poor response and printing failure. I couldn't speed it up.

In addition, if Tw is shortened, a large magnetic flux enters for a short period of time, which increases the occurrence of eddy current loss, which requires a large amount of power supply energy, which increases the cost due to the large capacity of the power supply, and generates heat in the impact dot head. There were major drawbacks such as the printing time being limited to III due to the increase in .

The present invention has been made in view of these problems, and its purpose is to provide an impact dot head that is capable of high-speed printing with consistently stable print quality and that requires less power supply energy.

[Means to solve the problem]

The impact dot head of the present invention has a drive coil that projects a printing wire by excitation and attraction and prints on a print medium supported on a platen, and when flyback of the drive coil occurs, the drive coil A first flyback circuit and a second flyback circuit are provided for current switching, and the application of voltage to the drive coil is OF.
In an impact dot head in which the current flowing through the drive coil flows through a first flyback circuit as nf increases, and the current flowing through the drive coil is switched from the first flyback circuit to the second flyback circuit.
fff The time during which the dynamic drive coil pressure is applied is T1, the first
Let T2 be the time during which the current of the drive coil is flowing through the flyback circuit, T1 is set to a predetermined value so that the printing force of the printing wire is constant according to the voltage value applied to the drive coil. It is characterized in that T1+T2 is constant regardless of the voltage.

〔Example〕

Embodiments of the present invention will be described below based on the drawings. 1st
The figure is a sectional view of an infected head showing one embodiment of the present invention, Figure 2 is a circuit diagram of a driver circuit 30, and Figure 3 is a circuit diagram of a driver circuit 30.
(a) of the figure shows the current wave engraving and the energization pulse, and (b) shows the energization time T1 and (T1+) for the applied voltage E to the drive coil.
FIG. 4A is a diagram showing T2), and (a) of FIG.
(b) is a diagram showing current flow, magnetic flux Φ, and printing wire behavior at high voltage.

The structure and operation of the impact dot head will be explained based on FIG. An armature 6 to which a printing wire 2 held by a plurality of wire guides 1 is fixed is rotatably held on a fulcrum shaft 3. The fulcrum shaft 3 is held between a yoke A13 and a holder 11 with a metal spacer 19 having good wear resistance in between, and is positioned by a yoke B14.

The yoke A13 is in contact with the frame 12, and the core 5 and the frame 12 are integrated. A driving coil 4 wound around a coil bobbin 17 is inserted into the core 5, and the substrate 1
5 and is connected to a driver circuit 30 through a flexible printed circuit board 16. amateur 6
is pressed by a return spring 10 during standby and is positioned by a damper 18 supported by a holder 11.

When the drive coil 4 is energized by the driver circuit 30, the core 5, frame 12, yoke A13, yoke B14,
A magnetic flux with the armature 6 in a closed loop is generated, the armature 6 is attracted to the core 5, and the printing wire 2 protrudes and collides with the printing medium 9 supported by the platen 8 via the ink ribbon 7 to perform printing.

The operation and energization method of the driver circuit 30 will be explained based on FIG. 2.

A drive coil is attached corresponding to each printing wire, but here we will explain one drive coil 4. When the 0 energization pulse A39 and the energization pulse B40 become H level at the same time, the transistors 32 and 33 are turned on.
Therefore, the voltage of the electric fi 38 is applied to the drive coil, and the electric current 1 flows to the drive coil 4 for 1 hour T l f & 3
f! When the 1-electric pulse A39 becomes L level, the transistor 32 is turned off, and the drive coil 4 and the transistor 33 are turned off.
, a power W is applied to the first flyback circuit around the diode 34.
1 After 0 time T2 when I2 flows, energization pulse B40 becomes L
Become a level! - The transistor 33 turns off, and the drive coil 4, diode 35, and Zener diode 37
, a transistor 36, a power supply 38, and a diode 34, and a second flyback circuit is supplied with power. At this time, the current that crushes the drive coil 4 is as shown in Fig. 3 (a),
Time T during which the voltage of the power supply 38 is applied to the drive coil 4
1, the current generator 1 rises, and the current generator 2 falls during the time T2 when the first flyback circuit is ON, and when the current I3 flows through the second flyback circuit, it rises more steeply than the current generator 2. Go down.

Since the voltage E applied to the drive coil 4 fluctuates due to variations in component ratings of the power source 38, fluctuations due to temperature, and a drop in the applied voltage due to overcapacity, in order to maintain a constant impact force, the third As shown in (b) of the figure, only the energization time T1 is changed depending on the applied voltage E, and T1+
72 is constant.

By keeping T1+T2 constant regardless of the voltage as shown in FIG. 4, the residual magnetic flux at the time of collision of the printing wire 2 is small even when the applied voltage E is low or high.
The return time of the printing wire 2 is short, making it possible to increase the printing speed. Further, since the electric current generator 2 with no load can be effectively used as the power source 38, the power supply energy can be reduced.

It goes without saying that the energization pulse width TI, T1+T2 will vary due to temperature changes and variations in the ratings of the component circuit parts, and even if the set value for the applied voltage E of T1 changes stepwise, this will not be considered as the gist of the present invention. Needless to say, it does not come off and has the same effect.

The energization time T1 is T 1 =-RCX In (1-/
E) is a setting suitable for obtaining a certain impact force. Here, RC is a constant, and E is the voltage applied to the drive coil.If the unit of one energization time T1 is (μS) and the unit of applied voltage E is (V), then the value of K is 3 to 30.
, furthermore, ni = 3 to 15, and further ni = 8 to 12,
When RC=200 to 800, or even 400 to 600, a T1 curve suitable for obtaining a constant impact force regardless of the value of the applied voltage E can be obtained.

In addition, the longer T2 is, the more effectively the electrician 2 can be used, and the smaller the power supply energy is required, but the longer T2
If T2 becomes longer, the residual magnetic flux will increase and poor response will more likely occur. Therefore, T2 cannot be made unnecessarily large;
When setting I/(T1+T2)=0.5 to 0.9, the power supply energy is small and no response failure occurs.Also, considering the fluctuations in the applied voltage E, at the center value of the fluctuations in the voltage E, TI/( By setting T1+T2)=0.6 to 0.8, the power supply energy can be reduced regardless of the applied voltage E. Furthermore, it is preferable to set (TI + T2) to 0.25 to 0.5 of the drive period, and more preferably 0.25 to 0.4.

In this example, the printing wire drive cycle is set to 617 (μS), the impact force is set to enable copying rIF force for three sheets, and the applied voltage E is in the range of 35 (V) ± 5 (V) (7). Fluctuation, RC=500. TI(μ5) as =10
--500x In (1-10/E), Tl/(
71+T2=240 so that TI+T2)=0.7
(μS). This setting makes it possible to increase the speed and reduce input energy by 30% compared to conventional drive systems. Additionally, durability has also been improved.

In addition, if there are multiple printing wire drive periods, T1 and T1+T are determined according to each printing wire drive period as described above.
It is best to set 2. Especially, depending on the detection position of the printing paper thickness, the adjustment position between the head and the platen, or the position of the carriage, the printing speed is slowed down on the side where there are many sheets of printing paper, and the impact force is improved. Suitable for settings when

In this embodiment, TI and T2 are adjusted by detecting the voltage applied to the drive coil 4, but the power supply voltage can also be used instead.

Further, it goes without saying that the driver circuit of the present invention is not limited to this embodiment, and that driver circuits having similar power supply waveforms also have similar effects.
Figure, Figure 7, Figure 81! 1 shows an example of another driver circuit in which the present invention can be implemented.

〔Effect of the invention〕

As described above, according to the present invention, only T1 is changed depending on the voltage applied to the drive coil, and T1 + T2 is kept constant, so that the residual magnetic flux between the core and armature at the time of printing wire collision is small regardless of the voltage. Therefore, the return time of the printing wire is shortened, and high-speed printing becomes possible.

Furthermore, since the power that can be used to drive the printing wire can also be used to drive the printing wire, the power that can be used to run the flyback circuit of YJI, which does not impose a load on the power supply, makes it possible to obtain the necessary printing power with less power supply energy.

[Brief explanation of drawings]

Fig. 1 is a sectional view of an impact head showing an embodiment of the present invention, Fig. 2 is a driver circuit diagram showing an embodiment of the invention, and Fig. 3(a) is a current waveform of an embodiment of the invention. FIG. 3(b) is a diagram showing the setting of T1 and T1+T2, and FIG. 4(a) is a diagram showing the current pulse at low voltage. Q? Figure 4(b) is a diagram showing the current waveform, magnetic flux, and printing wire behavior at high voltage.
(a) and (b) of FIG. 5, FIG. 6, FIG. 7, and FIG. 8 are diagrams showing examples of other driver circuits for realizing the present invention. Figure 9 is a schematic diagram of a conventional impact dot head. FIG. 10(a) is a conventional current waveform, FIG. 10(b) is a driver circuit diagram, and FIG. 11 is a diagram showing power supply, magnetic flux, and print wire behavior at low voltage under conventional energizing conditions. 2... Printing wire 4... Drive coil 5 River core 7... Ink ribbon 8... Platen 30... Driver circuit 32.33.36... Transistor 34.35... Diode 37. ... Zener diode 38... Power supply 39... Energizing pulse A 40... Energizing pulse B That's all

Claims (1)

[Claims] (1) It has a drive coil that projects a printing wire by excitation and attraction to print on a print medium supported on a platen, and a first switch for switching the current flowing through the drive coil when flyback of the drive coil occurs. and a second flyback circuit, when the voltage application to the drive coil is turned off, the current flowing through the drive coil flows through the first flyback circuit, and the current flows from the first flyback circuit to the first flyback circuit. In the impact dot head in which the current flowing through the drive coil is switched to the second flyback circuit, the time during which voltage is applied to the drive coil is T1, and the current of the drive coil is flowing through the first flyback circuit. When time is T2, T1 takes a predetermined value so that the printing force of the printing wire is constant according to the voltage value applied to the drive coil, and T1+T2 is constant regardless of the voltage. Features an impact dot head.