JPH0519912B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a piezoelectric actuator that serves as a drive source for drive devices such as printers and relays.

[Conventional technology]

Conventionally, electromagnetic actuators have been widely used as drive sources for printers, relays, and the like. This electromagnetic actuator generates a magnetic field by passing a current through the coil, and uses the magnetic force to drive the movable member, which not only causes copper loss and iron loss, but also requires a large amount of energy.
There were problems such as heat generation and magnetic interference. In recent years, a printing hammer for printers, as shown in Figure 4, has been reported, which uses a piezoelectric element that has good electrical/mechanical energy conversion efficiency, low power consumption, low heat generation, and no magnetic interference (Research Department of Mechanical Engineering, Institute of Electronics and Communication Engineers). Meeting materials
EMC84−49). FIG. 4 is a schematic side view of a printing hammer for a printer showing an example of a printing mechanism using a conventional piezoelectric actuator. In the same figure, the printing hammer is moved in the direction of the elongation operation of the piezoelectric element 4 (arrow A
A flight hammer 19 supported by a leaf spring 18 is arranged so as to be in contact with the tip of the blade (direction). The flight hammer 19 is provided with a printing wire 1 for printing dots. In this printing hammer, when a voltage is applied to the piezoelectric element 4, the flight hammer 19 is accelerated by receiving a force from the piezoelectric element 4 due to the high-speed expansion operation of the piezoelectric element 4, and flies away from the piezoelectric element 4. Then, the printing wire 1 collides with the platen 8 via the ink ribbon 10 and the paper 9 in front, and prints a dot on the paper 9. After that, the flight hammer 19 receives the repulsive force from the platen 8 and the leaf spring 1.
It returns to the piezoelectric element 4 by the restoring force of 8.
By repeating this action, characters and figures are expressed as a collection of dots.

[Problem that the invention seeks to solve]

In the conventional printing hammer for printers described above, in order to speed up the printing operation, the leaf spring 1
8, the flight hammer 19, and the printing wire 1, it is necessary to increase the natural frequency of the vibration system, and for this purpose, the spring constant of the leaf spring 18 must be increased. However, when the spring constant of the leaf spring 18 is increased, the proportion of the energy transmitted from the piezoelectric element 4 to the flight hammer 19 that is spent on deforming the leaf spring 18 increases, so the kinetic energy of the flight hammer 19 decreases. , the density of the printed dots becomes lighter. Therefore, in order to achieve faster printing operations without reducing print density, it is necessary to increase the energy transmitted from the piezoelectric element 4 to the flight hammer 19. By increasing this transmitted energy, the spring constant of the leaf spring 18 can be increased to increase the speed and ensure the desired print density. In order to increase the transmitted energy, the energy generated by the piezoelectric element 4 may be increased, and the applied voltage may be increased. However, when the applied voltage is increased, the acceleration of the piezoelectric element 4 increases, and the tensile stress generated by the inertial force of the piezoelectric element 4 itself increases. In particular, the flight hammer 19 is a piezoelectric element 4.
When the flight hammer 18 is supported by the piezoelectric element 4 of the leaf spring 18, the piezoelectric element 4 of the leaf spring 18 supporting the flight hammer 18
Since there is no pressing force against the piezoelectric element 4, the tensile stress becomes maximum and there is a problem that the piezoelectric element 4 may be damaged. SUMMARY OF THE INVENTION An object of the present invention is to solve these problems and provide a reliable high-speed printing head that has a simple structure and prevents destruction of the piezoelectric element.

[Means for solving problems]

The piezoelectric printing head according to the present invention includes a first leaf spring having a printing needle on the front surface of the free end facing the platen, and a second leaf spring disposed corresponding to the rear surface of the first leaf spring. and a substrate for fixing fixed ends of the first leaf spring and the second leaf spring and for sandwiching a piezoelectric element between the second leaf spring, and the second leaf spring has at least The spring constant is larger than that of the first leaf spring, and is arranged so as to constantly apply a compressive force in the direction of expansion and contraction of the piezoelectric element, and to transmit the force generated by the piezoelectric element to the first leaf spring.

[Effect]

In the piezoelectric printing head of the present invention, the first leaf spring, which is a free end and has a printing needle on the front surface facing the platen, has a fixed end with a second leaf spring arranged so as to correspond to and overlap with the rear surface thereof. is fixed to the board. Further, the second leaf spring sandwiches a piezoelectric element near its free end so as to always apply a compressive force to the substrate. Further, the second leaf spring is arranged so as to transmit the force generated by the piezoelectric element to the first leaf spring, and the spring constant of the second leaf spring is set so as to overcome the first reaction force when transmitting the force. It is larger than the first leaf spring. In such a print head, the second leaf spring constantly applies compressive force to the piezoelectric element even when it is driven, so that the piezoelectric element, which is weak against tension, is not destroyed, and reliability is greatly improved. In the print head constructed in this manner, a voltage is applied to the piezoelectric element, and the excitation of the piezoelectric element causes the second leaf spring to operate. Furthermore, the motion is transmitted from the second leaf spring to the first leaf spring, and the first leaf spring flies freely due to the action, that is, the impact force, and can perform a printing operation.

〔Example〕

The present invention will be described in detail with reference to the drawings.

FIG. 1 is a schematic sectional view of a print head showing a first embodiment of the present invention. In FIG. 1, a first leaf spring 2 having a free end and a printing wire 1 on its front surface facing the platen 8 is arranged so as to overlap its rear part, and its fixed end is connected to a second leaf spring 3. fixed at the fixed end. Further, the second leaf spring 3 is sandwiched between the piezoelectric element 4 near the free end and the substrate 5 so as to compress the piezoelectric element 4 in the direction of expansion and contraction, and the fixed end is fixed to the substrate 5. The spring constant of the compressive force is determined by the thickness and shape of the second leaf spring 3, and
The first spacer 6 is inserted into the fixed portion of the second leaf spring 3, and the restoring force is determined by the bending deformation of the second leaf spring 3. The second leaf spring 3 is arranged so that the operation of the piezoelectric element 4 can be transmitted to the first leaf spring 2, and the gap adjustment or contact pressure between the first leaf spring 2 and the second leaf spring 3 is adjusted. is carried out with the second spacer 7 at the fixed end. Furthermore, the spring constant of the second leaf spring 3 in the bending direction is greater than that of the first leaf spring 2, and a compressive force is always applied even when the piezoelectric element 4 is driven. In such a configuration, when a voltage is applied to the piezoelectric element 4, the piezoelectric element 4 causes a high-speed displacement operation,
The displacement is transmitted to the second leaf spring 3. At the same time, the motion is transmitted from the second leaf spring 3 to the first leaf spring 2, and the first leaf spring 2 performs a free flight motion. Therefore, the printing wire 1 held in the first leaf spring 2 is connected to the front platen 8, the paper 9, and the ink ribbon 1.
0 is struck, a character is drawn by the dot matrix, and then it returns to its original position due to the repulsion of the printing operation and the return force of the spring. Here, the first leaf spring 2 flies freely, but the second leaf spring 3 is always connected to the piezoelectric element 4.
is compressed, and the tensile stress of the piezoelectric element 4 that occurs when the first leaf spring 2 is in free flight is suppressed, so that the piezoelectric element 4 is not damaged, and a highly reliable printing head can be obtained.

Next, Figures 2a and 2b show a second embodiment of the present invention; Figure 2a is a partial perspective view of a serial printer print head, and Figure 2b is a cross-sectional view of the serial printer print head shown in Figure 2a. It is a diagram. In the same figure, a plurality of second leaf springs 12 are fixed to a cylindrical base plate 11 with a fixed end in common and radial toward the inside, and each of the plurality of second leaf springs 12 is connected to the base plate. A piezoelectric element 4 is connected between 11 and 11.
is pinched and compressed. Further, a first leaf spring 13 is arranged corresponding to the second leaf spring 12 and fixed to the fixed end. A printing wire 1 is provided at each free end of the first leaf spring 13, and the printing wire 1 is bundled by a wire guide 14 at its tip. In such a configuration, the second leaf spring 12 always applies compressive force to the piezoelectric element 4 and transmits the movement of the piezoelectric element 4 to the first leaf spring 13, so that the first leaf spring 13 is free. Damage to the piezoelectric element 4 can be prevented during printing operations caused by flying. Furthermore, spacers 6 and 7 are interposed between the fixing portions of the first leaf spring 13, the second leaf spring 12, and the substrate 11, so that the compressive force of the piezoelectric element 4 can be adjusted. Such a configuration has the effect of reducing the size because a plurality of heads can be configured on the same circumference within the cylindrical ring-shaped substrate 11.

Next, FIG. 3 is a schematic cross-sectional view of a serial printer print head showing a third embodiment of the present invention. In FIG. 3, a plurality of springs are formed radially with the cylindrical substrate of the second leaf spring 15 as the outer diameter, and a cover 1 is inserted from behind through a spacer 17.
At the same time, the piezoelectric element 4 is compressed and fixed by being sandwiched inside. In addition, the second leaf spring 1
Print wire 1 is placed in front of 5, that is, on the platen side.
A first leaf spring 13 having a shape is arranged and fixed to the fixed end via a spacer 7. Also, the printing wire 1
are bundled at the tip by a wire guide 14. Even in this configuration, the piezoelectric element 4 is always compressed, and a highly reliable printing head without damage can be obtained. It goes without saying that the purpose of the spacers 6, 7, 17 can be achieved even if they are not provided if the substrates 5, 11 and the second leaf springs 3, 15 can be processed with high accuracy.

〔Effect of the invention〕

As explained above, according to the present invention, a second leaf spring is provided between the first leaf spring having the printing wire serving as the output end and the piezoelectric element serving as the drive source, and the second leaf spring causes the piezoelectric By compressing the element, there is no damage to the piezoelectric element, and a highly reliable, compact, high-speed printing head can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a print head showing a first embodiment of the present invention, FIGS. 2a and b show a second embodiment of the invention, FIG. 3 is a schematic sectional view of a print head according to a third embodiment of the present invention, and FIG. 4 is a schematic side view of a conventional print head. Each symbol in the figure indicates the following content. 1... Printing wire, 2, 13... First leaf spring, 3, 12, 15... Second leaf spring, 4... Piezoelectric element, 5, 11... Substrate, 6, 7, 17... Spacer, 8...Platen, 9...Paper, 10...
Ink ribbon, 14...Wire guide, 16...
...Cover, 17...Leaf spring.

Claims (1)

[Claims] 1. In a piezoelectric printing head which is arranged opposite to a platen through printing paper and an ink ribbon and performs printing by causing a printing stylus to fly freely by the expansion and contraction movement of a piezoelectric element, the free end and the front surface on the platen side are A first leaf spring having a printing needle, a second leaf spring disposed corresponding to the rear surface of the first leaf spring, and fixed ends of the first leaf spring and the second leaf spring are fixed. and a second leaf spring for sandwiching the piezoelectric element therebetween, and the second leaf spring is always compressed in the direction of expansion and contraction of the piezoelectric element to a degree greater than the spring constant of the first leaf spring. A print head characterized in that it is arranged to apply a force and to transmit a force generated by a piezoelectric element to said first leaf spring.