JPH047308B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of driving an impact type wire dot printer head using an electrostrictive element,
The purpose is to suppress residual vibration in the wire.

Wire dot printers, which print using the mechanical impact of wires, can make simultaneous copies on plain paper.
Since characters are composed of a collection of pixels, it has excellent flexibility in recording kanji and figures in addition to alphabetical characters, and is widely used because it has the advantage of being inexpensive. Conventionally, wire dot printers have been mainly driven by an electromagnetic drive system, but this has been an obstacle to speeding up the printer because it requires a large amount of driving power and increases temperature due to overcurrent. On the other hand, impact type wire dot printers using electrostrictive elements are attracting attention because they can theoretically eliminate the drawbacks of the electromagnetic type.

However, in order to print at high speed with either the electromagnetic or electrostrictive method, it is necessary for the flying wire to hit the platen through the ink ribbon and paper, and to restore its original shape and start the next flight at the same time.
It is important to minimize residual vibration when the wire collides with the recording medium and stops. That is,
When starting the second flight, the larger the residual vibration, the greater the kinetic energy of the wire because the kinetic energy and strain energy of the printer head due to the previous flight are superimposed. In this way, the print density becomes higher from the second time onwards, and it becomes impossible to obtain a homogeneous print.

DESCRIPTION OF THE PREFERRED EMBODIMENTS A conventional electrostrictive printer head and its driving method will be described below with reference to the drawings.

FIG. 1 shows an example of an impact type wire dot printer head using an electrostrictive element, which has an electrostrictive element 101 held on a head base 102, and a first lever 107 and a second lever 108 are connected to hinges 103 and 108, respectively. 104 and 105, 106
It is connected to the electrostrictive element and the head base via. Further, the third lever 112 is connected to the hinge 111,1.
The third lever has an arm portion 117, and a wire 114 is connected to the arm portion. A stopper 118 is also formed on the head base 102. 115 is an ink ribbon, 116 is paper, and 117 is a platen. 1st
The principle of operation of the print head shown in the figure will be described. When a voltage is applied to electrostrictive element 101, electrostrictive element 101 is expanded, hinges 104 and 105 are compressed, and hinges 103 and 106 are expanded. As a result, the first lever 107 and the second lever 108 rotate in the directions indicated by the arrows. This movement causes the third lever 11 to move through the hinges 110 and 111.
2 and is further transmitted to the wire 114 via the arm portion 113. Then, the wire 114 moves straight in the direction of the arrow and hits the ribbon 115, paper 116, and platen 117 to perform printing. Due to the repulsive force of this impact and the restoring force of the hinge, the wire 114
returns to its original position and completes one reciprocating movement.

Conventionally, an electrostrictive printer head is driven by a rectangular voltage wave, and the applied voltage is reduced to zero when the wire hits the recording medium and returns to its original position (the time up to this point is defined as one cycle T). However, since it is difficult to minimize the mechanical strain energy within the printer head, residual vibrations are generally noticeable. As a conventional example, a printer head having the shape shown in Fig. 1 (period T = 0.48 msec) was used.
Figure 2 shows the time response characteristics of the wire tip displacement when driven by a rectangular voltage wave. Figure 2A shows the time response of the wire tip displacement, and Figure 2B shows the driving voltage waveform of the electrostrictive element.The voltage is reduced to zero at a time of 0.48msec (one cycle T) when the wire returns to its original position. . The head used in Figure 2 has a wire tip and
The gap between the ribbon, paper, and platen is 0.40 mm, and the electrostrictive element is a longitudinal effect laminated ceramic vibrator (width 3 mm, depth 2
mm, length 18 mm), and the displacement magnification rate of the head is 42
It's double. That is, when a printer head is driven with a conventionally used rectangular voltage wave, the mechanical system of the printer head cannot easily follow sudden electrical changes such as an instantaneous drop in voltage. Significant strain energy is stored in the hinge, base, and electrostrictive elements within the head. Therefore, residual vibrations are noticeable. As is well known, when the voltage is reduced to zero at a point away from the vicinity of one cycle T of the printer head,
Residual vibration with a larger amplitude than the residual vibration characteristics shown in FIG. 2 occurs, making it impractical.

In view of this, an object of the present invention is to provide a method for driving an electrostrictive printer head that can minimize the residual vibration of the printer head when the wire attempts to return to its original position.

That is, in the present invention, the strain of the electrostrictive element caused by voltage application is transmitted to the lever part via the hinge,
In an electrostrictive printer head driving method in which the displacement of the lever section is transmitted to the wire via the arm section, and the wire strikes the recording medium to perform printing, the wire strikes the recording medium after voltage is applied. The time it takes to return to the original position after hitting the ball is T.
The voltage at the start of application is V ₀ , the time is t,
When the minute time interval is ΔT, the applied voltage V is: When 0<tT-ΔT, V=V ₀ When T-ΔT<t<T+ΔT, V=-(V ₀ /2ΔT)(t-T)+1/2V This is a method of driving an electrostrictive printer head characterized by setting the head to _zero .

FIG. 3 shows a driving voltage waveform of a printer head using an electrostrictive element according to the present invention. In the drive voltage waveform shown in Figure 3, the rising part is the same as the conventional rectangular wave, but in the falling part, the voltage decreases in proportion to the passage of time from a time ΔT shorter than the period T of the printer head. Then, point P(T,
1/2V ₀ ), and the voltage becomes zero at time T+ΔT. When the drive voltage falls slowly in this way, the mechanical system of the printer head easily follows, and for the reason mentioned above, residual vibrations are suppressed to a minimum.

Next, as an embodiment of the present invention, residual vibration suppression was verified using the printer head shown in FIG. 1 in the same manner as in FIG. 2. This is shown in Figure 4. The characteristic shown by the solid line in FIG. 4A is the wire tip displacement characteristic using a driving voltage wave according to the present invention. Further, the dotted line indicates the wire tip displacement characteristic when the conventional rectangular drive voltage wave shown in FIG. 2B is used. Fourth
Figure 9 shows an example of the drive voltage waveform according to the present invention, where the voltage falls from a constant voltage of 235V in 0.42msec to 117.5V with a fall period of 0.48msec, and the voltage becomes zero in 0.54msec. As is clear from FIG. 4, according to the present invention, the residual vibration of the printer head is suppressed to one-third or less compared to when a conventional rectangular drive voltage waveform is used. Incidentally, the fall of the drive voltage should be done in consideration of the period T of the printer head, and it is not sufficient to reduce it unnecessarily and gently. For example, when the printer was driven with a voltage waveform passing through point Q in FIG. 3, there was no effect of suppressing residual vibrations in the printer head.

Incidentally, the drive circuit of this printer head is shown in FIG. That is, this drive circuit has an opening/closing circuit 120 connected to apply the voltage of a power source 122 to both terminals 123 and 124 of the electrostrictive element 127, and a short-circuit between both terminals 123 and 124 of the electrostrictive element 127. This circuit is constituted by a connected opening/closing circuit 121 and is controlled by a printing control signal Va and a signal inverted by an inverter circuit 126. Here, in order to control the fall time of the driving voltage described above, a resistor 125 is connected in series between the electrostrictive element terminals 123 and 124 and the switching circuit 121, and the braking capacity of the electrostrictive element 127 and the resistor 125 are connected in series. This can be realized by providing a time constant determined by the resistance value of .

As detailed above, according to the present invention, the residual vibration of the wire tip displacement can be suppressed to a minimum, and the second wave can be continuously input immediately after the first wave of the drive voltage is input. This method is effective for increasing the speed and print quality of wire dot printers.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of an impact type wire dot printer head using an electrostrictive element. FIG. 2A is a time response characteristic diagram of the displacement of the wire tip when the printer head shown in FIG. 1 is driven with a conventionally used rectangular voltage wave, and FIG. 2B is a diagram of the drive voltage waveform of the electrostrictive element. FIG. 3 is a drive voltage waveform diagram according to the drive method of the present invention, and FIG. 4 is a diagram showing the difference in printer head wire tip displacement between the drive voltage wave according to the present invention and the conventional rectangular drive voltage wave. Figure 4A is a wire tip displacement characteristic diagram using a driving voltage wave according to the present invention. FIG. 4B is a diagram showing an example of a driving voltage waveform according to the present invention. FIG. 5 is a diagram showing a printer head drive circuit according to the present invention. In the figure, 101 and 127 are electrostrictive elements, 10
2 is head base, 103, 104, 105, 1
06, 110, 111 are hinges, 107, 10
8, 112 are the first lever, the second lever,
3rd lever, 113 is the 3rd lever arm part, 1
14 is a wire, 115 is an ink ribbon, 116
is paper, 117 is platen, 118 is stopper,
120, 121 are switching circuits, 122 is a power supply, 12
3, 124 is the terminal of the electrostrictive element, 125 is the resistor, 1
26 is an inverter circuit.

Claims (1)

[Claims] 1. Distortion of the electrostrictive element caused by voltage application is transmitted to the lever section via the hinge, displacement of the lever section is transmitted to the wire via the arm section, and the wire hits the recording medium. In a method of driving an electrostrictive printer head that performs printing, T is the time from when voltage is applied until the wire hits the recording medium and returns to its original position, and the voltage at the start of application is V ₀ When the time is t and the minute time interval is ΔT, the applied voltage V is: When 0<tT−ΔT, V=V ₀ When T−ΔT<t<T+ΔT, V=−(V ₀ /2ΔT)(t -T) +1/2V _0. A method for driving an electrostrictive printer head.