JPH04251756A - Head for impact dot printer - Google Patents

Abstract

PURPOSE:To provide a piezoelectric element type small-sized head having low power consumption for an impact dot printer. CONSTITUTION:a) a piezoelectric element unit 12 elongated by applying voltage, b) a block type lever 14 magnifying the displacement of the piezoelectric element unit 12 and using the displacement as second stage displacement, c) a first V-shaped lever 15 forming third stage displacement enlarging second stage displacement, d) a second V-shaped lever 16 forming fourth stage displacement extending third stage displacement and driving an impact dot wire 17 are provided. The displacement of the piezoelectric element unit 12 is magnified at the three stages of the block type lever 14, the first V-shaped lever 15 and the second V-shaped lever 16 and transmitted over the wire 17. The direction of the displacement of the piezoelectric element unit 12 is varied approximately vertically by the first and second V-shaped levers respectively, thus finally extruding the wire in the opposite direction to the direction of the elongation of the piezoelectric element unit.

Description

[Detailed description of the invention]

0001

FIELD OF THE INVENTION This invention relates to printheads for impact dot printers.

0002

2. Description of the Related Art Impact dot printers print characters and the like by striking a large number of wires (impact dot wires) onto a sheet of paper through an ink ribbon. Conventionally, electromagnets have been used to drive this wire, but this electromagnetic drive mechanism has drawbacks such as: 1) high power consumption, 2) high heat generation, and 2) limitations in speeding up. Ta. In order to overcome these drawbacks, wire drive mechanisms using piezoelectric elements have been developed in recent years. However, since the amount of displacement of the piezoelectric element itself is very small, we first utilize the longitudinal strain effect of the piezoelectric element, and then use a multilayer piezoelectric element, which is a stack of many thin piezoelectric elements.
The aim is to obtain a large amount of displacement. Even this is still far insufficient for the stroke of the wire required to hit the paper, etc., so a displacement magnification mechanism as shown in FIG. 4 is used. The mechanism shown in FIG. 4 is called a differential two-stage displacement amplifying mechanism. One end of the laminated piezoelectric element 30 is fixed to the center of the bottom arm of the U-shaped frame 31, and there is a space between the other end (free end) of the piezoelectric element 30 and one arm of the frame 31. A first lever 32 and a second lever 34 are stretched between the free end of the piezoelectric element 30 and the other arm of the frame 31, respectively. Both the first lever 32 and the second lever 34 extend their arms in a direction perpendicular to the displacement direction of the piezoelectric element 30, and have a first hinge 35 and a second hinge 3 at their other ends, respectively.
6 is installed. The first and second hinges 35, 36 both have a third hinge at the other end.
It is attached to a lever 37, and a printing wire 38 is fixed to the third lever 37. This displacement magnification mechanism performs the following operations. When the piezoelectric element 30 expands by applying a voltage to the laminated piezoelectric element 30, the first lever 32 is pushed up at the force point 321, and the connection point 3 with the frame 31 is pushed up.
22 as a fulcrum and rotates in the direction of arrow 323. On the other hand, the second lever 34 is pushed up by a force point 341 and rotates in a direction opposite to the rotational direction of the first lever 32 (arrow 343) using a connection point 342 with the frame 31 as a fulcrum. Therefore, at these other ends, the first lever 32 moves upward and the second lever 34 moves downward (differential).
. Note that here, the displacement of the laminated piezoelectric element 30 is
Depending on the lever ratio of the levers 32 and 34, first stage expansion is performed. The movements of the first and second levers 32 and 34 in mutually opposite directions are converted into the movement of rotating the third lever 37 via the first and second hinges 35 and 36, respectively, and the rotational movement of the third lever 37 causes the wire 38 is pushed out in the direction of arrow 381 and hits the paper. Here, the third lever 38
performs the second stage displacement expansion. The above is the operation of the differential two-stage displacement amplifying mechanism.

0003

[Problem to be Solved by the Invention] To prevent a wire from leaving ink traces on the paper by strongly striking the paper through the ink ribbon when printing, and by firmly separating from the ink ribbon when not printing. In order to achieve this, the operating stroke of the wire must be at least about 0.5 mm. However, even if the conventional displacement magnification mechanism (FIG. 4) is used, the magnification is only about 50 times at most, so the amount of displacement of the laminated piezoelectric element needs to be about 10 μm. In order to obtain such a displacement amount with a piezoelectric element, it was necessary to increase the number of laminated layers and to increase the size of the piezoelectric element itself. Therefore, conventional piezoelectric element type printer heads are large in size, which hinders miniaturization of printers. Furthermore, the power consumption of the piezoelectric element is large, making it difficult to drive it with a battery. The present invention has been made in view of the current situation, and its purpose is to:
An object of the present invention is to provide a piezoelectric element type head for an impact dot printer that is small in size and consumes low power.

0004

[Means for Solving the Problems] The impact dot printer head of the present invention includes a piezoelectric element unit that expands by applying a voltage, and a second stage displacement in approximately the same direction by expanding the displacement of the piezoelectric element unit. A simple lever to generate,
The end of one arm is fixed, and by receiving the second stage displacement in the longitudinal direction of the arm at the end of the other arm, the second stage displacement is expanded approximately vertically at the joint of both arms. The first V-shaped lever that generates the third-stage displacement and the end of one arm are fixed, and the end of the other arm receives the third-stage displacement in the longitudinal direction of the arm. 3rd approximately vertically at the joint
It is characterized by comprising a second V-shaped lever that generates a fourth step displacement that is an enlarged step displacement and drives the impact dot wire.

[0005]

[Operation] The displacement of the piezoelectric element unit is controlled by a simple lever, the first
The V-shaped lever and the second V-shaped lever are expanded in three stages and transmitted to the wire. Therefore, the amount of displacement of the piezoelectric element unit to obtain the displacement of the wire necessary for printing can be small. Further, since the displacement direction of the piezoelectric element unit is changed to be substantially perpendicular by the first and second V-shaped levers, the wire is finally pushed out in a direction opposite to the direction in which the piezoelectric element unit is extended.

[0006]

EXAMPLES The present invention will be explained below with reference to examples. FIG. 2 shows a front view of a piezoelectric element type printer head according to an embodiment of the present invention, and FIG. 3 shows a cross-sectional view taken along line 9--9. This printer head is for 24 dots, and each of the 24 wires is provided with a wire drive unit shown in FIG. As shown in FIG. 2, the 24 wire drive units are arranged in a fan shape of 12 each, and all the wires driven by each wire drive unit are concentrated in the central convergence part. The 24 wires 17 are arranged in the direction of movement of the printer head (horizontal direction in FIG. 2) in the focusing section.
(Figure 3).

FIG. 1 shows an enlarged view of one wire drive unit 25. As shown in FIG. The wire drive unit 25 includes a frame body 10 having a substantially U-shape, a laminated piezoelectric element unit 12, a piezoelectric element cap 13, and a block-type lever 14 (
(equivalent to the "simple lever" described in the claims)
, a first V-shaped lever 15, a second V-shaped lever 16, and a wire 17. Among these, the frame body 10, the block type lever 14, the piezoelectric element cap 13,
In addition, the first V-shaped lever 15 has a thickness of about 0.8 to 1.6
It is integrally constructed from a steel plate of mm. Here, there are narrow channels 18 and 19 between the frame body 10 and the block-type lever 14, and between the block-type lever 14 and the piezoelectric element cap 13, respectively.
The block-type lever 14 has flexibility with respect to the frame body 10, and the piezoelectric element cap 13 has flexibility with respect to the block-type lever 14 within the plane of the frame steel plate (the plane of the paper in FIG. 1). (See enlarged image below). The first arm 20 of the first V-shaped lever 15 is connected to the block-shaped lever 14,
The second arm 21 is connected to the frame body 10, and the first V-shaped lever 15 as a whole extends parallel to the displacement direction of the piezoelectric element unit 12 (in the vertical direction in the plane of the drawing). The first arm 22 of the second V-shaped lever 16 is pivotably held at the apex of the first V-shaped lever 15, which is the connecting portion of both arms, so as to be rotatable within the plane of the unit. The second arm 23 of the second V-shaped lever 16 is similarly pivoted to the frame body 10, and the second V-shaped lever 16 as a whole is connected to the first V-shaped lever 16.
perpendicularly to the shape lever 15, that is, the piezoelectric element unit 1
It extends in a direction perpendicular to the displacement direction of No. 2 (left-right direction in the plane of the paper). A wire 17 is fixed to the apex of the second V-shaped lever 16, which is the connecting point of both arms, in a direction perpendicular to the second V-shaped lever 16. Therefore, the wire 17 is ultimately parallel to the direction of displacement of the piezoelectric element unit 12. The piezoelectric element unit 12 is placed in the cove of the U-shaped frame 10, with one end (fixed end) attached to one arm 11 of the frame.
The other end (free end) is fixedly disposed on the cap 13.

The operation of the wire drive unit 25 constructed in this manner will be described next. Piezoelectric element unit 12
When the rated voltage is applied to , each thin film piezoelectric element is displaced vertically in the plane of the paper, and the cap 13 (as a whole piezoelectric element unit 12) is displaced by about 60 degrees with respect to the frame body 10.
．． Push up 5 μm (arrow a). This displacement of the cap 13 pushes up the block lever 14 with the channel 19 as the point of force and the channel 18 as the fulcrum (arrow b). At this time, the displacement of the cap 13 is determined by the distance between the fulcrum 18 and the point of force 19 and the base (point of action) of the fulcrum 18 and the first arm 20.
The first arm is enlarged with a magnification equal to the ratio of the distance between
Push up 0 (arrow c). In the case of this embodiment, the displacement magnification rate of this first stage is about 5 times. In the first V-shaped lever 15, the tip of the first arm 20 is connected to the block-shaped lever 1.
4 pushes up as shown by arrow b, but the second arm 2
1 remains fixed by the frame 10. Therefore, the second arm 21 is pushed laterally (arrow d),
The apex of the first V-shaped lever 15 is displaced in a direction (arrow e) perpendicular to the direction of displacement of the first arm 20. At this time, the magnitude of the lateral displacement (arrow e) is the displacement of the block lever 14 (arrow b) magnified by a magnification according to the length of the arm of the V-shaped lever 15 and the distance between the tips of both arms. becomes. In this embodiment, the magnification ratio of this second stage is about 6 times. Regarding the second V-shaped lever 16, the direction of the displacement (e) of one arm 22 is converted vertically (forces f, g correspond to the forces c and d of the first V-shaped lever 15, respectively), their magnitudes are magnified and converted into the displacement (h) of the wire 17. The magnification ratio (third stage) at this time is also approximately 6 times.

As described above, in the printer head of this embodiment, the displacement of the laminated piezoelectric element unit is enlarged in three stages, so that the overall enlargement ratio can be made very large (in the case of this embodiment, (about 5 x about 6 x about 6 = about 180 times). Therefore, in order to finally obtain the required displacement amount of 0.5 mm for the wire, the displacement amount of the piezoelectric element unit 12 only needs to be about 2.8 μm. Since this is much smaller than the required displacement amount of the piezoelectric element of a conventional printer head, the size of the piezoelectric element unit can be reduced accordingly. For this reason, it is possible to make the piezoelectric element unit as thin as the thickness of the frame and to arrange it so that it is concentrated in a fan shape very close to the wire convergence part, as shown in FIG. Therefore, although the printer head in the above embodiment was for 24 dots, as can be seen from FIG. 2, 12 wire drive units were additionally placed in the upper and lower fan-shaped spaces. According to
It is also possible to configure a 48-dot printer head with approximately the same size. Another important feature of this embodiment is that the displacement of the piezoelectric element unit is ultimately translated into just the opposite direction, so as to displace the wire. Therefore, the total length of the printer head (the distance from the tip of the wire to the rear end of the printer head) is shortened, and the printer head is further miniaturized. Furthermore, as the volume of the piezoelectric element unit becomes smaller, power consumption also decreases, and it becomes possible to drive it with a battery. For these reasons, the printer head according to the present invention is particularly suitable for portable printers.

0010

In the printer head of the present invention, the displacement of the piezoelectric element unit is magnified in three stages and transmitted to the wire. As a result, the amount of displacement of the piezoelectric element unit to obtain the displacement of the wire necessary for printing can be small, so the size of the piezoelectric element unit can be reduced and power consumption can also be reduced. This makes the printer head of the present invention suitable for small-sized printers, and particularly suitable for battery-powered portable printers. Furthermore, since the direction of displacement of the wire is approximately parallel (opposite) to the direction in which the piezoelectric element unit extends, a large number of piezoelectric element units can be arranged to surround the bundled wire. As a result, the length of the printer head (the distance from the tip of the wire to the rear end of the printer head) can be reduced, further contributing to miniaturization of the printer head. The three-stage displacement magnification mechanism of the present invention can be used not only for downsizing the piezoelectric element unit, but also for increasing the amount of displacement of the wire. For example, it can be used in a printer for making a large number of carbon copies, a special printer for adding irregularities to paper, etc.

[Brief explanation of the drawing]

FIG. 1 is a plan view of a wire drive unit that constitutes a printer head according to an embodiment of the present invention.

2 is a front view of a printer head configured by a collection of 24 wire drive units shown in FIG. 1. FIG.

FIG. 3 is a 9-9 cross-sectional view of the printer head in FIG. 2.

FIG. 4 is a plan view of a conventional wire drive unit.

[Explanation of symbols]

Claims (1)

[Claims] Claim 1: A piezoelectric element unit that expands by applying a voltage, a simple lever that expands the displacement of the piezoelectric element unit to generate a second stage displacement in approximately the same direction, and an end of one arm that is fixed. By receiving a second-stage displacement in the longitudinal direction of the arm at the end of the other arm, a third-stage displacement is generated which is an expansion of the second-stage displacement in a substantially vertical direction at the joint of both arms. The 1V-shaped lever and the end of one arm are fixed, and by receiving the third stage displacement in the longitudinal direction of the arm at the end of the other arm, the third stage is moved in the approximately vertical direction at the joint of both arms. A head for an impact dot printer, comprising a second V-shaped lever that generates a fourth stage displacement that is an enlarged third stage displacement to drive an impact dot wire.