JPH0253230B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to impact printer heads.

A conventional printer head that utilizes the transverse effect of piezoelectric or electrostrictive ceramics includes a transverse effect type electrostrictive vibrator 1 and a transverse effect type electrostrictive vibrator 1, as shown in FIGS.
The pin 2 is attached to the tip 1a of the pin 2. In such a configuration, in order to obtain a predetermined displacement and speed, a bias voltage is applied in advance to displace the tip 1a of the electrostrictive vibrator 1 in a direction opposite to the platen 7 to a position α, and then a bias voltage opposite to the bias voltage is applied. A voltage of β is applied to the tip 1a of the electrostrictive vibrator 1.
The pin 2 is caused to collide with the platen 7 by displacing the pin 2 to the position shown in FIG.

However, such printer heads
Although it has the advantages of low driving power and a simple structure, it has the drawbacks of slow printing speed and a large required volume of the piezoelectric or electrostrictive ceramic.

SUMMARY OF THE INVENTION It is an object of the present invention to eliminate the above-mentioned disadvantages and to provide an impact printer head which requires less piezoelectric or electrostrictive ceramic volume and has a higher printing speed.

In order to achieve the above object, the printer head of the present invention includes an L-shaped support and a piezoelectric element fixed to one side of the L-shape of the support, each of which has a longitudinal effect. a means for transmitting the telescopic motion of the piezoelectric body; and a lever having one end fixed to the other side of the L-shaped support and transmitting the telescopic motion via the transmitting means in the vicinity of the fixed end. , a plurality of printing units each including a printing pin attached to the other end of the lever, and an amplitude limiting means disposed at the tip of the lever to limit movement of the lever; and the plurality of printing units. and a unit fixing means for fixing the pins of each unit and guiding the pins of each unit.

A feature of the present impact printer head is the use of longitudinal effect piezoelectric or electrostrictive ceramics. The piezoelectric or electrostrictive ceramics mentioned here include piezoelectric materials represented by zircon and lead titanate, and strain materials such as manganese and lead niobate. The difference between piezoelectric materials and electrostrictive materials is that the former causes polarization, whereas the latter does not. These piezoelectric or electrostrictive ceramics are usually used for two physical phenomena: transverse effect and longitudinal effect. The transverse effect means a strain effect in a direction perpendicular to the direction of an electric field applied to the electrostrictive material, and the longitudinal effect means a strain effect in a direction parallel to the direction of the electric field.

The magnitude of distortion due to the transverse effect and the longitudinal effect is approximately the ratio of Poisson's ratio, that is, approximately 1:3 when comparing the same materials. If this is compared with the mechanical energy stored in piezoelectric or electrostrictive ceramics, it will be the square of the strain, that is, a ratio of 1:9. Therefore, conversely, the volume of piezoelectric or electrostrictive ceramic required to store the required energy is the inverse ratio of the above ratio, that is, 9:1. That is, the volume of piezoelectric or electrostrictive ceramic required to obtain the same mechanical energy is 1/9 when using the longitudinal effect compared to when using the transverse effect.

Next, the present invention will be explained in detail with reference to the drawings.

FIG. 2 is a diagram explaining the principle of the present invention. In Figure 2, a longitudinal effect piezoelectric or electrostrictive ceramic 1
The mechanical strain generated at 0 is transmitted to the vicinity of one end of the lever 14 and the fixing member 15 by the first connecting mechanism 11 and the third connecting mechanism 12, respectively. On the other hand, the first
A second connecting mechanism 13 joined closely to the connecting mechanism 11 is arranged between the lever 14 and the fixing member 15. The pin 16 is joined to one end of the lever 14. Excitation electrode terminals 18 and 19 are bonded to both sides of the piezoelectric or electrostrictive ceramic 10,
A predetermined voltage is applied. The stopper 17 limits the movement of the lever 14 within a predetermined range, and
used to prevent destruction of

Next, the effect of the stopper 17 will be explained using FIGS. 3a to 3c.

FIG. 3a shows a transient phenomenon of the movement of lever 14 in the direction of arrow A. Lever 1 is moved by stopper 17.
The amplitude of the motion of 4 is limited to A1 to A2. FIG. 3b shows the time course of the force applied to the piezoelectric body 10 in connection with this. When a voltage is applied from the outside, the piezoelectric body 10 tries to expand and is therefore subjected to a compressive force F1, but in response to the movement of the lever 14, the compressive force is gradually relaxed and it continues to receive a tensile force.

In this case, the presence or absence of the stopper 17 acts to control the maximum value of the tensile force. That is, stopper 1
7 does not exist, the maximum tensile force F2
is approximately equal to the compressive force F1, but if the stopper 17 is present, the maximum value F3 of the tensile force is a fraction of F2. FIG. 3c shows the applied voltage at this time.

As a specific numerical example, when the impact energy of the impact member is 6000 ergs, F ₂ = 20Kg and F ₃ is 5Kg. On the other hand, if the cross-sectional dimensions of a piezoelectric body are 2 mm x 3 mm, the strength of a normal piezoelectric body is
If calculated using 300Kg/cm ² , the strength will be 18Kg,
At _F2 , the piezoelectric material is destroyed, but at _F3 , it is not destroyed even if it is repeatedly applied.

As described above, the presence or absence of the stopper 17 is of decisive importance for an impact printer head using a longitudinal effect piezoelectric material.

Generally, when this impact printer head is installed in a printer, if the impact printer head is in a normal state, the collision member hits the paper even if the stopper 17 is not present, so that it has the same effect as a stopper and there is no problem.
However, when operating only with the head, or when adjusting the distance between the head and the platen to set the appropriate printing pressure, the arm is in a free state or a state close to it, so if the stopper 17 is missing, This makes it inappropriate as a practical printer.

FIG. 4 is a perspective view of a basic unit 100 constituting the head of the present invention. In the figure, a piezoelectric or electrostrictive ceramic 10 is sandwiched between a first connection mechanism 11 and a third connection mechanism 12. The first and third connection mechanisms 11 and 12 are connected to the fifth connection mechanism 11 and 12.
As shown in the figure, it has a cap structure and is firmly fixed to a piezoelectric or electrostrictive ceramic 10 by adhesive or soldering. This structure is very effective in preventing deterioration of strength at the bonded portion for relatively fragile materials such as piezoelectric or electrostrictive ceramics. Referring again to FIG. 4, the first and third connecting mechanisms 11 and 12 each have a lever 14
and is joined to the fixing member 15. A second connecting mechanism 13 is joined to a lever 14 in proximity to the first connecting mechanism 11 , and the other end of the second connecting mechanism 13 is joined to a fixing member 15 . A pin 16 is connected to one end of the lever 14. Stoppa 1
7 is attached to a fixed member 15, and its tip is arranged so as to maintain a predetermined space with respect to the lever 14.

FIG. 6 shows a state in which the unit 100 shown in FIG. 4 is fixed to the mounting member 21. As shown in FIG. unit 100
The pin 16 is disposed through a hole provided in a stopper 17 which also serves as a guide for the pin 16.

FIG. 7 is a diagram illustrating the operation of the unit 100 shown in FIG. 4. A is the case when no voltage is applied between the external terminals 16 and 17, and b is the case when the same voltage is applied. Due to the voltage application, the piezoelectric body 10 generates an elongation strain, and as a result, the lever 14 is pushed up and θ
Excite rotation of direction. Here, let's say stopper 1
When the lever 7 is not present, the lever 14 goes through an angle of rotation corresponding to the elongation strain of the piezoelectric body 10, and a strong tensile force is generated on the piezoelectric body.

In the case of FIG. 7, since it hits the stopper 17, there is no need to apply extra tensile force to the piezoelectric body.

FIG. 8 shows the structure of the piezoelectric or electrostrictive ceramic 10, in which figure a shows the structure of the piezoelectric material and figure b shows the structure of the electrostrictive material. In Figure 8a,
Electrodes 22 and 23 are arranged alternately on a piezoelectric material such as lead gyricotitanate, and are connected to external electrodes 24 and 25, respectively. Reference numeral 26 indicates the polarization direction;
This direction is reversed layer by layer. External terminal 18
The direction of the electric field due to the voltage applied between .

FIG. 8b shows the case of a manganese-lead niobate isoelectrostrictive material.

The difference from FIG. 8a is that there is no polarization.
In this case, the electrostrictive material stretches as the voltage is applied, regardless of the direction of the voltage between the external terminals 18 and 19. A feature of electrostrictive materials is that they have no hysteresis. In piezoelectric or electrostrictive ceramics having a layered electrode structure as shown in FIGS. 8a and 8b, the required strain can be obtained with a low applied voltage.

As described above, according to the present invention, since the longitudinal effect of voltage or electrostrictive ceramic is utilized, an impact printer head with a simple structure and low driving power can be obtained.

[Brief explanation of the drawing]

Figures 1a and b are perspective views showing a conventional impact printer head, Figure 2 is a principle diagram of the basic unit used, Figures 3a to c are diagrams illustrating the effect of the stopper, and Figures 4 and FIG. 5 is a perspective view showing the basic unit and an explanatory view of its parts, FIG. 6 is a perspective view showing an embodiment of the present invention, FIGS. 7 a and b are views explaining the operation of the basic unit, and FIG. 8 a
and b are perspective views showing piezoelectric and electrostrictive ceramics. In FIG. 6, 21... unit mounting member;
14... Lever, 10... Piezoelectric or electrostrictive ceramic, 15... Fixing member, 11-13... Connection mechanism, 16... Pin, 17... Stopper.

Claims (1)

[Scope of Claims] 1. An L-shaped support, a piezoelectric body consisting of a laminate of piezoelectric elements each having a longitudinal effect and fixed to one side of the L-shape of the support, and expansion and contraction of the piezoelectric body. a means for transmitting a motion; a lever having one end fixed to the other side of the L-shaped support and to which the telescopic motion is transmitted via the transmitting means in the vicinity of the fixed end; a plurality of printing units each including an attached printing pin and an amplitude limiting means disposed at the tip of the lever to limit the movement of the lever; and a unit fixing means for guiding the pins of the impact printer head.