JP3010986B2 - Print head for wire dot printer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a print head for a wire dot printer for selectively driving a plurality of print wire elements by a piezoelectrically driven actuator, and more particularly to a piezoelectric element laminate of a piezoelectrically driven actuator in an annular frame. The present invention relates to a print head for a wire dot printer of a type directly assembled.

[0002]

2. Description of the Related Art As is well known, wire dot printers are typical of impact printers, and their print heads have a number of print wire elements, each print wire element being incorporated into an individual actuator. For example, 24x
When characters and symbols are recorded as a 24-matrix dot image, the print head is provided with 24 print wire elements and 24 actuators for driving each of these print wire elements. By selectively driving based on image data, characters, symbols, and the like are recorded as a dot image of a 24 × 24 matrix.

Conventionally, as an actuator for driving a printing wire element, an electromagnetically driven actuator is generally used. However, an electromagnetically driven actuator consumes a large amount of power, and the development of a higher printing speed is limited. In recent years, piezoelectric-driven actuators have been attracting attention as an alternative to electromagnetically-driven actuators. As one form of this type of piezoelectrically driven actuator, a type in which a piezoelectric element laminate in which a large number of piezoelectric elements are integrally laminated together with a support block body is known. More specifically, the piezoelectric element laminate is disposed adjacent to the support block, and the rear end of the piezoelectric element laminate is fixedly supported by the support block. On the other hand, on the front end side of the piezoelectric element laminate, there is provided an enlargement mechanism for enlarging a fine displacement amount of the piezoelectric element laminate as a desired drive amount required for the printing wire element. The beam element is supported by the front end of the piezoelectric element stack and the support block through the leaf spring element, and a print wire element is fixed to the free end of the beam element. When a predetermined drive voltage is applied to the piezoelectric element laminate,
Its height or length is increased by about 14 to 15 μm,
This fine driving amount is transmitted to the beam element via the leaf spring element on the piezoelectric element laminate side, and at this time, the beam element is turned around a substantially middle point of the span length of the leaf spring element on the support block body side, As a result, the leaf spring element is driven with a drive amount or stroke of 280 to 300 μm required for dot recording.

A predetermined number of the above-described piezoelectrically driven actuators, for example, 24, are prepared, and these piezoelectrically driven actuators are individually assembled to the annular frame of the print head, whereby the print head is assembled. The piezoelectric actuator is supported on the annular frame by its support block. The unitized piezoelectric drive actuator has the advantage that not only its assembly but also its disassembly can be performed relatively easily, and that the drive test of each piezoelectric drive actuator can also be performed advantageously. There is. However, on the other hand, in order to unitize the piezoelectric drive actuator, a support block is required for each piezoelectric drive actuator, and such an increase in the number of parts naturally increases the manufacturing cost of the print head. become.

In order to reduce the cost of the print head, a print head has been developed in which the piezoelectric drive actuator is not unitized and the piezoelectric element laminate is directly assembled to the annular frame of the print head. Have been. In this type of print head, a plurality of piezoelectric element laminates are arranged annularly along the inner wall surface of an annular frame, and each piezoelectric element laminate is directly mounted on the bottom of the annular frame. On the other hand, on the front side of the annular frame, magnifying mechanisms for enlarging the fine driving amount of the piezoelectric element laminate to a desired driving amount required for the printing wire element are arranged in a ring shape. Partially supported by More specifically, the enlargement mechanism itself has the same configuration as that described above, but its beam element is supported by the front end of the piezoelectric element laminate and the annular frame via a pair of leaf spring elements. According to such a configuration, the annular frame of the print head functions as a common support structure for all the piezoelectric actuators, and therefore, as in the case of the above-described print head, for each piezoelectric actuator, No support block is required, which can provide a low cost print head.

[0006]

However, when the annular frame of the print head is used as a common support structure for all the piezoelectric actuators, a drive voltage is applied to the piezoelectric element laminate of each piezoelectric actuator. When this occurs, local distortion deformation occurs in the annular frame, and this distortion deformation affects the driving characteristics of the piezoelectrically driven actuator adjacent to the piezoelectrically driven actuator. That is, when the local strain deformation generated in the annular frame is transmitted to the adjacent piezoelectric drive actuator, the minute strain deformation changes the print wire element via the enlargement mechanism of the piezoelectric drive actuator. That is, even if a drive voltage is applied to the piezoelectric element laminate of the piezoelectric drive type actuator during the fluctuation, the print wire element cannot be properly driven. Needless to say, such a phenomenon becomes more remarkable as the printing speed is increased.

Another problem is that, because of the partial support of each enlargement mechanism to the annular frame, a part of the enlargement mechanism is fastened to the annular frame with a single set screw due to space constraints. However, at this time, it is pointed out that the enlargement mechanism is displaced due to the fastening torque applied to the set screw, and excessive stress is applied to the leaf spring element and the like to cause breakage.

Accordingly, a first object of the present invention is a print head for a wire dot printer of a type in which a piezoelectric element laminate of a piezoelectric drive actuator is directly assembled to an annular frame. The present invention is to provide a print head for a wire dot printer configured to substantially prevent local distortion deformation occurring in an annular frame when a drive voltage is applied to the wire frame. A second object of the present invention is a print head for a wire dot printer of the type described above, wherein a part of each magnifying mechanism is provided with a single set screw for partial support of the magnifying mechanism with respect to the annular frame. An object of the present invention is to provide a print head for a wire dot printer which is configured to prevent a displacement of an enlargement mechanism that occurs when fastening is performed.

[0009]

According to the present invention, in order to achieve its first object, an annular frame and an inner wall surface of the annular frame for selectively driving a plurality of printing wire elements. Comprising a plurality of piezoelectrically driven actuators arranged in a ring, each piezoelectrically driven actuator is mounted on the bottom of the ring-shaped piezoelectric element laminate,
An enlarging mechanism for enlarging the fine driving amount of the piezoelectric element laminate to a desired driving amount required for the printing wire element, wherein the enlarging mechanism is partially supported by an annular frame for a wire dot printer. In the print head,
It is characterized in that a plurality of reinforcing rib elements are integrally attached at predetermined intervals to one or both of the outer wall surface and the inner wall surface of the annular frame.

According to the present invention, in order to achieve the second object, an annular frame and a plurality of printing wire elements are annularly arranged along an inner wall surface of the annular frame to selectively drive the plurality of printing wire elements. A plurality of piezoelectrically driven actuators, each piezoelectrically driven actuator being mounted on the bottom of an annular frame, and a fine drive amount of the piezoelectrically stacked body required for a printing wire element. A magnifying mechanism for enlarging to a desired driving amount, wherein the magnifying mechanism is partially supported by the annular frame. When a part of the enlargement mechanism is fastened to the annular frame with a single set screw, all the enlargement mechanisms are common between the part of the enlargement mechanism and the set screw. That is interposed an annular washer element is characterized.

[0011]

As is apparent from the above description, the first aspect of the present invention.
In the print head for a wire dot printer configured to achieve the above object, a plurality of reinforcing rib elements are integrally attached at predetermined intervals to one or both of the outer wall surface and the inner wall surface of the annular frame. Therefore, distortion deformation generated in the annular frame when the piezoelectric element laminate of each piezoelectric drive actuator is driven is prevented.

In a print head for a wire dot printer configured to achieve the second object of the present invention, a part of the enlargement mechanism is provided for partially supporting each enlargement mechanism with respect to an annular frame. When the is fastened to the annular frame with a single set screw, an annular washer element common to all the expanding mechanisms is interposed between a part of the expanding mechanism and the annular frame. When a part of is temporarily fastened with the corresponding set screw and then equally fastened to the entire set screw with a predetermined fastening torque, the presence of the annular washer element prevents the displacement of the individual enlargement mechanisms.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of a print head for a wire dot printer according to the present invention will be described with reference to FIGS. FIG. 1 is a vertical sectional view schematically showing a print head embodying the present invention.
FIG. 2 is a partial cross-sectional view taken along the line II-II in FIG. 1. In FIGS. 1 and 2, a part thereof is simplified by imaginary lines (two-dot chain lines) in order to avoid complicating the drawing.

The print head comprises an annular frame 10,
The annular frame 10 is preferably formed of a metal material having a low coefficient of thermal expansion, for example, an iron-chromium-nickel alloy called Super Invar. A circular opening 12 is formed in a central area of the bottom of the annular frame 10, and a peripheral area thereof is an annular bottom 14. In addition, in this embodiment, the bottom of the annular frame 10 is opened by the circular opening 12, but the bottom can be formed as a closed bottom as required. The front side of the annular frame 10 is opened, and the outer flange 1
6 are integrally protruded.

The print head includes, for example, twenty-four piezoelectrically driven actuators 18, which are housed in an annular flange 10 and are arranged in an annular shape at substantially equal intervals along the inner wall surface. You. In FIG. 2, only one of the 24 piezoelectric actuators 18 is shown. Each of the piezoelectric actuators 18 includes a piezoelectric element stack 20, and the piezoelectric element stack 20 is composed of a large number of piezoelectric elements that are integrally laminated and sintered. Block pieces 22 and 24 are attached to both ends of the piezoelectric element laminate 20, and the two block pieces 22 and 24 are connected to each other by a tie band (not shown) extending along the side surface of the piezoelectric element laminate 10, Thereby, the integrity of the piezoelectric element laminate 20 is guaranteed. Each piezoelectric element laminate 20 is disposed adjacent to the inner wall surface of the annular frame 10, and the block piece 22 at the rear end thereof is fixed on the annular bottom portion 14 of the annular frame 10. Electrode terminals are formed on opposing side surfaces on the rear end side of the piezoelectric element laminate 10, and lead pins 26 are soldered to the respective electrode terminals. As shown in FIG. 1, the lead pins 26 pass through the annular bottom portion 14 of the annular frame 10, and the lead pins 26 are insulated from the annular frame 10 at this time. On the other hand, the block piece 24 on the front end side of each piezoelectric element laminate 20 is adjacent to the front opening edge of the annular frame 10 and protrudes forward beyond the front opening edge.

Each piezoelectric actuator 20 includes a magnifying mechanism 28 provided at a front end thereof, and the magnifying mechanism 28 includes a beam element 30 arranged radially with respect to a center axis of the annular frame 10. I do. Beam element 3
0 is elastically supported by the annular frame 20 and the piezoelectric element laminate 20 via a pair of parallel leaf spring elements 32 and 34. That is, one end of the pair of parallel leaf spring elements 32 and 34 is connected to the outer end of the beam element 30 while the other end of one leaf spring element 32 is fixed on the outer flange 16 of the annular frame 10. And the other leaf spring element 34
Is connected to the block piece 24 of the piezoelectric element laminate 20. A print wire element 38 is secured to the free or inner end of the beam element 30.

When a driving voltage is applied to each piezoelectric element stack 20 through its pair of lead pins 26 so as to increase the height, that is, the length, the beam element 30 becomes the span length of the outer leaf spring element 32. The print wire element 3 is rotated about the intermediate point in the direction of arrow A in FIG.
Reference numeral 8 is driven forward toward the printing position to perform dot recording. When the application of the drive voltage to the piezoelectric element stack 28 is completed, the printing wire element 38 is returned to the non-printing position, that is, the initial position shown in FIG. 1 due to the elastic force of the parallel leaf spring elements 54 and 56. According to such a configuration of the piezoelectric drive type actuator 26, even if the height, that is, the increment of the length due to the application of the drive voltage to the piezoelectric element laminate 20, is as fine as about 14 to 15 μm, As the increment is amplified by beam element 30, print wire element 38 can be driven from the non-print position to the print position with a stroke of about 280 to about 300 .mu.m required for dot recording.

The 24 print wire elements 38 are guided to the print surface of the print head through appropriate guide means (not shown), and the free ends of the 24 print wire elements are at a predetermined pitch on the print surface. In this case, the free ends included in one row are vertically shifted by half the pitch with respect to the free ends included in the other row, and the half pitch is a 24 × 24 matrix. Corresponds to the dot pitch when recording characters or symbols as a dot image.

When a driving voltage is applied to each piezoelectric element laminate 20 so as to increase the height, that is, the length, the annular frame 10 is locally deformed.
For example, when a driving voltage is applied to the left piezoelectric element laminate 20 in FIG. 1, the annular frame 10 undergoes distortion deformation as shown by a broken line at the place where the piezoelectric element laminate 20 is installed. When subjected to such strain deformation, the piezoelectric element stack adjacent to the piezoelectric element stack is displaced, and therefore, the print wire element fluctuates via the enlargement mechanism incorporated in the adjacent piezoelectric element stack. If a driving voltage is applied to the adjacent piezoelectric element laminate during the fluctuation, the printing wire element cannot be properly driven.

According to the present invention, one of the outer wall surface and the inner wall surface of the annular frame 10 is used to prevent the deformation of the annular frame 10 when the individual piezoelectric actuators 18 are operated. Alternatively, a plurality of reinforcing rib elements 40 and 42 are integrally attached to both at predetermined regular intervals. The reinforcing rib elements 40 and 42 may be integrally formed when the annular frame 10 is formed, or may be fixed by brazing or the like after the formation of the annular frame 10. When 24 piezoelectric actuators 18 are arranged in the annular frame 10, it is preferable to provide 24 reinforcing rib elements 40 and 42, respectively. In this case, the reinforcing rib elements 40 and 42 each have 15 degrees. It is preferable that they are arranged at equal angular intervals. When the reinforcing rib elements 40 and 42 are provided on both the outer wall surface and the inner wall surface of the annular frame 10,
As shown in FIG. 2, the arrangement pitch of the reinforcing rib elements 40 and 42 is preferably shifted by a half pitch (15/2 degrees). Further, when the reinforcing rib elements 40 are provided only on the outer wall surface of the annular frame 10, each of the reinforcing rib elements 40 is preferably provided at a location corresponding to the installation location of the electrically driven actuator 18, which means that the annular frame The same can be said for the case where the reinforcing rib element 42 is provided only on the inner wall surface 10. The above-described solid reinforcing rib element 40,
By providing the ring frame 10 with the ring frame 10, distortion deformation generated in the ring frame 10 when each of the piezoelectric actuators 18 is actuated can be prevented, so that a higher printing speed can be achieved.

According to another feature of the invention, the expansion mechanism 28
A single set screw 44 is used to secure the block piece 36, which forms part of the
The set screw 44 is connected to the outer flange 16.
An annular washer element 46 common to all 24 block pieces 36 when screwed into the block piece 36 and the set screw 44
Intervened between. In order to arrange the 24 piezoelectric actuators 18 and the enlarging mechanism 28 in a print head having a relatively small size and shape, the block piece 36 becomes extremely small.
It is difficult to screw and assemble 6 with two set screws, and the use of two set screws increases the number of parts accordingly. Therefore, a single set screw 44 is used to fix each block piece 36 on the outer flange portion 16 of the annular frame 10. At this time, the set screw 44 is used without the annular washer element 46 interposed. When the fastening torque is applied, the enlargement mechanism 28 is displaced by the fastening torque, and excessive stress is applied to the leaf spring elements 32 and 34 and the like, which may cause breakage. However, according to the present invention, the annular washer element 46 is connected to the 24 block pieces 36 and the set screws 44.
, It is possible to apply a fastening torque to all of the twenty-four set screws 44 without causing a shift in the individual enlargement mechanisms 28. More specifically, first, the block pieces 36 forming a part of the individual enlargement mechanism 28 are temporarily fixed with set screws 44, and then, while gradually applying the tightening torque to the individual set screws 44, all the block pieces 36 are fixed. By finally tightening, it is possible to prevent the occurrence of displacement in the enlargement mechanism 28.
This is because the frictional force of the set screw 44 is directly transmitted to the block piece 36 by the annular washer element 46 while the block piece 36 is temporarily fixed with the set screw 44 and the fastening torque is gradually and uniformly applied to the set screw 44. This is because that is suppressed.

[0022]

As is apparent from the above description, according to the present invention, a plurality of reinforcing rib elements are integrally attached at predetermined intervals to one or both of the outer wall surface and the inner wall surface of the annular frame. Since the deformation of the annular frame during the driving of the piezoelectric element laminate of each piezoelectric drive type actuator is prevented, a print head for a wire dot printer capable of high-speed printing at low cost can be realized. Further, according to the present invention, when a part of the enlargement mechanism is fastened to the annular frame with a single set screw for partial support of each enlargement mechanism with respect to the annular frame, a part of the enlargement mechanism is used. By interposing an annular washer element common to all the expansion mechanisms between the set screw and the set screw, a part of each of the expansion mechanisms is temporarily fixed with the corresponding set screw, and then evenly set to the entire set screw. Since the presence of the annular washer element prevents the displacement of the individual enlargement mechanisms when fastening with the fastening torque, the assembling work of the print head for the wire dot printer can be speeded up and the efficiency can be improved. It is possible.

[Brief description of the drawings]

FIG. 1 is a vertical sectional view of a print head for a wire dot printer embodying the present invention.

FIG. 2 is a sectional view taken along line II-II in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Annular frame 12 ... Circular opening 14 ... Annular bottom part 16 ... Outer flange part 18 ... Piezoelectric drive type actuator 20 ... Piezoelectric element laminated body 22/24 ... Block piece 26 ... Lead pin 28 ... Magnifying mechanism 30 ... Beam element 32 34 ... leaf spring element 36 ... block piece 38 ... printing wire element 40/42 ... reinforcing rib element 44 ... set screw 46 ... annular washer element

────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Masayoshi Kageyama 1405 Daimaru, Inagi-shi, Tokyo Fujitsu Isotec Co., Ltd. (56) References JP-A-4-363257 (JP, A) JP-A-3-71856 (JP, A) JP-A-3-224747 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B41J 2/295

Claims (2)

(57) [Claims] An annular frame (10) and a plurality of piezoelectrically driven actuators (18) arranged annularly along an inner wall surface of the annular frame to selectively drive a plurality of printing wire elements (38). And a piezoelectric element stack (20) in which each piezoelectric actuator is mounted on the bottom of the annular frame, and a fine drive amount of the piezoelectric element stack is required for a print wire element. An enlarging mechanism (28) for enlarging the driving amount of the annular frame (10), wherein the enlarging mechanism is partially supported by the annular frame. A plurality of reinforcing rib elements (4
0, 42) are attached integrally at a predetermined interval. 2. An annular frame (10) and a plurality of piezoelectrically driven actuators (18) arranged annularly along an inner wall of the annular frame to selectively drive a plurality of printing wire elements (38). And a piezoelectric element stack (20) in which each piezoelectric actuator is mounted on the bottom of the annular frame, and a fine drive amount of the piezoelectric element stack is required for a print wire element. And a magnifying mechanism (28) for enlarging the driving amount of the annular frame (10), wherein the magnifying mechanism is partially supported by the annular frame. )
When the part (36) of the enlargement mechanism is fastened to the annular frame with a single set screw (44) for partial support of the part (36) of the enlargement mechanism (44) A print head for a wire dot printer, wherein an annular washer element (46) common to all enlargement mechanisms is interposed between the print head and the enlargement mechanism.