JPS59202864A - Wire dot printing head - Google Patents

Abstract

PURPOSE:To obtain a stroke necessary for printing and to attain to enhance reliability and prolong life by a small piezoelectric element, by driving a printing wire without almost imparting vibration to the piezoelectric element by applying an anti-resonant theory in vibration engineering. CONSTITUTION:A piezoelectric element 1 has spring coefficient k1 at the position of a connector 2 having mass m1 attached to one end thereof while one end of a leaf spring having spring coefficient k2 is connected to the other end of the piezoelectric element 1 through the connector 2 and the trailing end of a printing wire 4 having mass m2 is connected to the other end of said spring 3. One end of the piezoelectric element 1 is held between a fixed base 5 and a fixed piece 6 and fixed by a non-conductive screw 7 so as to be supported in a cantilevered state. When printing is not performed, the printing wire 4 and the leaf spring 3 having spring coefficient k2 at the position of this wire 4 as well as the connector 2 having mass m1 and the piezoelectric element 1 having spring coefficient k1 at the position of the connector 2 are fixed and an anti-resonant state is held. Therefore, the piezoelectric element 1 and the connector 2 are not almost vibrated and the leaf spring 3 and the wire 4 are vibrated minutely.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technique I: Field J] The present invention relates to a wire dot print head that drives a print wire using a piezoelectric element with high electrical-to-mechanical conversion efficiency.

[Conventional Wave 61ir] Conventionally, the technology of using a piezoelectric element as a driving source for a printing wire is a method that utilizes the transverse vibration of a known piezoelectric element (for example, Patent Application No. 30517 of 1972,
No. 99717, No. 103217, etc.) and a method using known pressure itl and longitudinal vibration of the element (for example, No. 29318, patent issued in 1978). It can be roughly divided into types.

The print head according to the former method uses a piezoelectric element as a cantilever bending element, and fixes one end of this piezoelectric element.7. There is a configuration in which the printing wire is fixed to the other end or -1/ is touched, but in this configuration, the length of the piezoelectric element must be increased in order to obtain the necessary stroke of the printing wire.
However, it is necessary to increase the voltage applied to the piezoelectric element, and the printing operation is slow.

On the other hand, the print head using the latter method has the disadvantage that it cannot take a sufficient stroke necessary for printing, and it is extremely difficult to perform stable printing.

Furthermore, the essential drawbacks of printheads using both of the above methods are:
As a drive source for the printing wire, a non-metallic piezoelectric element with low fatigue strength is used, but repeated use can cause damage to the piezoelectric element due to fatigue, and the electrode pattern can become brittle, reducing reliability. In addition, the lifespan of the print head is also short.

[Purpose of the invention]

The present invention was made in order to solve the above-mentioned drawbacks of the prior art, and it is possible to obtain a sufficient stroke necessary for printing with a small piezoelectric element, do not require high applied voltage, and can print at high speed and stability. The object of the present invention is to obtain a wire dot print head that can perform /ζ printing and also achieve improved reliability and extended life.

[Invention, tI+) formation]

In order to achieve the above-mentioned object, the present invention connects one end of a leaf spring to the other end of a piezoelectric element whose one end is fixed in a cantilever shape, and fixes or contacts a printing wire to the other end of the leaf spring. By applying the principle of anti-resonance in vibration engineering, the printing wire can be fully driven with almost no vibration applied to the piezoelectric element.

〔Example〕

First, before explaining the configuration of the embodiment of the wire print head according to the present invention, we will explain the principle of anti-resonance in vibration engineering. Figure 1 shows a vibration model of a two-degree-of-freedom system based on vibration engineering. In the explanatory diagram shown, one end of a first spring A having a bending coefficient of 1 at a point of mass 77L1 is fixed, a mass 77L1 is provided at the other end, and this mass rn1 has a bending coefficient of 1 at a point of mass m2. When one end of a second spring B having a spring coefficient of 12f is connected, and the other end of the second spring B is provided with a spring B and a spring m2, the mass η11 has an amplitude of the excitation frequency III. It becomes F.

Therefore, when a sinusoidal excitation force f'c is applied.

1" -? is established between the mass 77L2 and the spring coefficient n2 of the second spring B, the mass n11 and the first spring A do not vibrate, and the mass 77L2 has an amplitude of F/n. 1 sine wave vibration.

FIG. 2 is a partially cutaway side view showing an embodiment of the wire dot print head according to the present invention, which applies the principle of anti-resonance.First, the structure thereof will be explained.

In the figure, 1 is a piezoelectric element, one end of which is fixedly supported by being sandwiched between a fixed base and a fixed piece, which will be described later.This piezoelectric element 1 is attached to the other end of a connector 2 having a mass 7n1. It has a spring coefficient of 1.

3 is a temporary spring with a spring coefficient of 2, one end of which is connected to the other end of the piezoelectric element 1 via the connector 2, and the rear end of the printing wire 4 having a mass m2 is connected to the other end. ing.

Note that the piezoelectric element 1 can be considered to have an equivalent mass at the point where it connects to the leaf spring 3, so depending on the shape of the piezoelectric element 1,
A certain equivalence! If @-1 is provided, there is no need to use all the connectors 2 with masses Il and l9, and the plate spring 3 may be directly connected to the piezoelectric element 1.

Furthermore, in the present invention, the connection between the leaf spring 3 and the printing wire 4 means that they are fixed together by brazing or the like, that they are both supported 1/1 by rotation with a T-pivot, etc., and that the printing wire 4 is connected to the printing wire 4. This includes pressing and supporting the plate spring 3 by using a coil spring or the like in contact with the plate spring 3.

5 is a fixed base which also serves as a common electrode for a plurality of piezoelectric elements 1 integrated with the leaf spring 3 and the 10-shaped wire 4 as described above; 6;
is a fixed piece that also serves as an individual electrode corresponding to each piezoelectric element 1, and one end of each piezoelectric element 1 is bent downward between the fixed base 5 and the fixed piece 6, and is fixed with a non-conductive screw 7. It is supported in a cantilevered manner.

Reference numeral 8 denotes a damper piece that vibrates upwardly when the leaf spring 3 and printing wire 4 return to their home positions 111J, and is attached to the center of the fixed base 5 having a U-shaped cross section. A damper film 9 made of a viscoelastic material or the like is provided on the surface.

A front head cover 10 is made of a non-conductive material 1 and formed into a predetermined shape, and is integrally fixed to the fixing base 5 and the fixing piece 6 by the screws 7. A cylindrical guide portion 11 is formed in the center of the front head cover 10. Wire guides 12 and 13 are provided within the guide portion 11 to form the trajectory of the printing wire 4. There is.

14 is a substrate attached to the back surface of the front head cover 10, and this substrate 14 includes a fixed base 5 which also serves as a common electrode for a plurality of piezoelectric elements 1, and a fixed piece which also serves as an individual electrode corresponding to each piezoelectric element 1. 6 or 2t are electrically connected to each other.

A rear end cover 15 has an electrically insulating function and is provided to cover the outer periphery of the fixed base 5 and the fixed piece 6.

Next, the printing operation of the above-described structure will be explained with reference to FIGS. 3 and 4.

In Figures 3 and 4, normally when printing is not done, the fixed base 5 is o(v)', and the fixed piece 6 is
(As shown in Fig. 4(a), a rectangular wave with a voltage V1 (for example, about 2O-100V) with an appropriate amplitude of the print drive period W is continuously applied. At this time, a print with a mass m2 is A wire 4, a plate spring 3 having a spring coefficient of 2 at the position of this printing wire 4, a mass 1114'd: 2, and a piezoelectric element 1 having a spring coefficient of 1 at the position of this connector 2. In between is the ID explained in Figure 1.
/J11.2 The relationship between /J11.2 has ended,
The anti-resonance state is generally maintained.

Therefore, the piezoelectric element 1 and the connector 2 hardly vibrate,
The leaf spring 3 and the printing wire 4 are slightly vibrating as shown in FIG. 4(b). The amplitude of this weak vibration is given as F1/n1 by the force F1 generated on the digit of the connector 2 by the application of a rectangular wave by the voltage VIK and the spring coefficient n1 of the piezoelectric element 1, and the printing operation It is designed so that it does not pose a substantial obstacle to carrying out the operation.

Next, when the printing wire 4 ff: "drives to print", the voltage V2 (for example, 3
00 to rooov) at an appropriate time as shown in FIG. 4(c). Then 5. In synchronization with the weak vibration when no printing is performed, HI is activated as shown in Figure 4(d).
A large amplitude is generated in the leaf spring 3 by the voltage 2, and the printing wire 4 is pivoted, and its tip collides with a printing medium (not shown), resulting in efficient printing. Then, printing is completed. The printing wire 4 is moved to the home position 7 due to the repulsion of the collision.
The vibration of the collision is effectively absorbed by the damper film 9 shown in FIG. 2, while the voltage v2 becomes O as shown in FIG.
Since the voltage V1 is applied at the same time as the FF becomes FF, the anti-resonance state is set again to prepare for the next printing operation.

〔Effect of the invention〕

As explained above, the present invention fixes one end of a piezoelectric element, connects one end of a leaf spring to the other end directly or via a connector, and connects all printing wires to the other end of this leaf spring. Since the printing wire is driven by fully applying the principle of anti-resonance in vibration engineering, the following effects can be obtained.

In other words, the piezoelectric element hardly vibrates regardless of whether printing is performed or not.In other words, the piezoelectric element does not directly perform the printing operation, and the printing operation is performed by the leaf spring and the printing wire, so it is not possible to use the conventional method. The essential drawback of the method of fully driving the printing wire by vibrating the piezoelectric crystal made of non-metallic material is that it rarely causes fatigue of the piezoelectric element [such as breakage, mB2 "" turn length, etc.: L7 I can lose it, Konnyo 9 Jinrei j
It is possible to make the print head more flexible and to make the print head wider.

In addition, as mentioned above, since the piezoelectric element hardly vibrates, there is no need to take into account the problem of breakage due to fatigue in the shape of the piezoelectric element, and the piezoelectric element can be made entirely small, resulting in small and lightweight wire dot printing. In order to perform the printing operation using a temporary spring and a printing wire instead of using a tape scraper, a small piezoelectric element can secure enough stroke length necessary for printing, and it also uses a low voltage. It is possible to make one-stroke movement.

Furthermore, in the present invention, since the printing operation is started in synchronization with the slight vibration when printing is not being performed, the printing wire has good acceleration, has excellent electrical-to-mechanical conversion efficiency, and provides high-speed and stable printing. -7- Can do everything.

Furthermore, as described above, the present invention has the advantage that even though a ringing voltage is applied to the piezoelectric element due to the principle of anti-resonance, the piezoelectric element is hardly vibrated or assisted, and the temporary springs etc. connected to the piezoelectric element are Since the present invention applies vibration to a vibration system, it can be widely applied to submersible sonic oscillators, ultrasonic cleaners, etc. that require reliability, and it is also possible to provide a highly reliable vibration source.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing a vibration model with two degrees of freedom based on vibration engineering, Fig. 2 is a partially cutaway side view showing an embodiment of the wire dot print head according to the present invention, and Fig. 3 is an implementation of Fig. 2. FIG. 4 is a waveform diagram showing the relationship between the electrical drive method and the operation of the printing wire in the embodiment of FIG. 2. 1... Piezoelectric element 2... Connector 3... Leaf spring 4... Printing wire 5... Fixed base 6... Fixed piece 7... Screw 8... Damper piece 9
... Damper film 10 ... Front head cover 11 ... Guide part 12.13 ... Wire guide
14... Board 15... Rear hand cover 1- Nene 2= Bit 3= ■ 1 Dragon 4 pieces

Claims (1)

[Claims] 1. In a wire dot print head that uses a piezoelectric element as a driving source and prints by driving a printing wire by applying voltage to the piezoelectric element, one end of the piezoelectric element is fixed, and one end of a leaf spring is connected to the other end. , and the rear end of the printing wire is fully connected to the other end of this temporary spring.