JPH05212880A - Printing head - Google Patents

Abstract

PURPOSE:To inhibit occurrence of noise by making assembly fitting easy by a method wherein wiring between a piezoelectric element of a printing unit and a head substrate is performed with an FPC. CONSTITUTION:An FPC 37 of a printing unit 20 passes through a corresponding slit 61 of a head substrate 59, and a part of its tip projects outside. A connection part 37c of the FPC 37 is opposed to a feed path 59c in contact with the slit 61 under this state. Then, the feed path 37c is soldered to the connection part 37c. Further, the FPC 37 between a piezoelectric element and the substrate is made slightly bent under the soldered state. Therefore, vibration generated in the printing unit 20 is difficult to be transmitted to the head substrate 59.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a print head which uses expansion and contraction of a piezoelectric element as a drive source.

[0002]

2. Description of the Related Art Japanese Patent Application No. 3-21 filed by the applicant earlier
The specification and drawings attached to the application of No. 0968 describe a print head in which a print unit and a head substrate are connected by a conductive pin and a conductive wire. The structure of the print head 100 will be described below with reference to FIG.

First, the structure of a printing unit 110 for driving a single printing wire 102 will be described. Piezoelectric element 1
The reference numeral 12 is laminated in the left-right direction in the drawing and extends and contracts in the left-right direction. The piezoelectric element 112 is supported by a U-shaped support frame 114 at its rear end (right side in the drawing) and side surface. The piezoelectric element 1 is mounted on the support frame 114.
A motion changer 11 for converting expansion and contraction of 12 into tilting motion
6, the motion converting device 116 tilts the arm 118 having the print wire 102 attached to the tip thereof.

A socket 120 is provided at the rear end (right side in the figure) of the support frame 114, and two conductor pins 122 are erected on the socket 120. Each conductor pin 1
22 has a diameter of 0.5 mm, and its base is connected to each electrode of the piezoelectric element 112 by a conductive wire 124.

The print head body 130 is composed of the print wire 10.
It has a nose body 132 for guiding the 2 and a disc portion 134 for supporting the printing unit 110. A large number of printing units 110 are radially attached to the disc portion 134. At this time, all the conductor pins 122 face the rear of the print head (right side in FIG. 12).

A side cover 140 having a through hole 138 formed in the bottom is attached to the print head body 130 to cover the side of the print unit 110. At this time, the conductor pin 122 projects from the through hole 138. This through hole 1
38 is closed by the head substrate 142. Through holes having a diameter of 1.5 mm are formed in the head substrate 142 at positions corresponding to the conductor pins 122, and conductors formed by printed wiring communicate with the through holes. The conductor pin 122 and the conductor communicating with the through hole 138 are soldered.

The head substrate 142 is attached by inserting the conductor pins 122 into the through holes 138 of the head substrate 142 with the print unit 110 and the side cover 140 attached to the print head body 130. Done.

[0008]

However, soldering the conductive wire to the piezoelectric element is very troublesome and difficult to mass-produce. For example, in a 24-pin print head, the total number of conductor pins is 48.
It is extremely difficult to arrange all the conductor pins in parallel because of the problem of assembling books and the assembling accuracy. Therefore, the step of inserting the conductor pin into the through hole of the head substrate becomes extremely difficult. Therefore, there is a problem that the assembling efficiency cannot be increased.

Further, the printing unit vibrates along with the printing operation. This vibration is transmitted through the conductor pin having high rigidity and vibrates the head substrate. As a result, the soldered portion to the head substrate may come off, and the head substrate itself or the side cover in contact with it may be vibrated, resulting in a large amount of noise.

The present invention has been made in view of the above problems, and it is an object of the present invention to improve the assembly efficiency of a print head by improving the mechanism for feeding power to the piezoelectric element of each piezoelectric unit.

A further object of the present invention is to provide a print head having a contact portion such as a soldering portion with high durability and low noise.

[0012]

In order to achieve this object, a print head according to the present invention transmits a piezoelectric element which expands and contracts by applying a voltage and a stretching wire of the piezoelectric element to a print wire which stamps a print medium. In a print head having a plurality of printing units including a motion transmission mechanism for moving the piezoelectric element and a support frame supporting the motion transmission mechanism, the print head has two conductor portions extending in the longitudinal direction, and each conductor A flexible sheet member attached to the printing unit so that one end of the portion is electrically connected to each electrode of the piezoelectric element, and a slit-shaped hole into which the flexible sheet member is inserted are provided, and the flexible sheet member is inserted into the slit-shaped hole. It is characterized in that it has a substrate having a power feeding path that conducts with the conductor portion of the flexible sheet member in the opened state.

[0013]

In the print head of the present invention having the above structure, each electrode of the piezoelectric element is connected to the conductor portion of the flexible sheet member. At this time, by attaching one end of one flexible sheet member, wiring can be performed for both electrodes. Then, the other end of the flexible sheet is inserted into the slit-shaped hole of the substrate. At this time, the flexible sheet has only two bending directions, and is sufficiently flexible in that direction. Therefore, it is possible to easily insert all the flexible sheet members into the predetermined slit-shaped holes.

Further, since the flexible sheet is less likely to transmit vibrations than the conventionally used conductor pins and the like, the durability of the connecting portion such as soldering is dramatically improved.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

First, the structure of the printing unit will be described. As shown in FIG. 2, a plurality of piezoelectric ceramics 11 each having a thickness of about 100 μm are laminated on a piezoelectric element 10 used in the present printing unit, and an internal electrode 12 is interposed between the piezoelectric ceramics 11. ing.

On every other side surface A, an electric insulating material 13 is applied to the exposed portions of the internal electrodes every other layer, and the external electrodes 14 are formed on the exposed surfaces of the internal electrodes from substantially the upper end to the lower end of the piezoelectric element 10. .. Therefore, the internal electrodes are connected to the external electrodes every other layer. The external electrode 14 extends from the lower end of the side surface A to the lower surface C and has an area less than half of the lower surface C.

On the side surface B forming a pair with the side surface A, the electric insulating material 13 is applied to the exposed portion of the internal electrode 12 in every other layer with a displacement from the side surface A by one layer. Similarly, the external electrodes 14 are formed from the upper end to the lower end of the piezoelectric element 10 and to an area less than half of the lower surface C. Then, each external electrode 14 portion on the lower surface C becomes a power feeding position.

The two external electrodes 14 are insulated from each other. Since the piezoelectric ceramics 11 are polarized in a predetermined direction in advance, when a voltage is applied to these two external electrodes 14 as positive and negative electrodes, respectively, a voltage is applied to the upper and lower surfaces of each piezoelectric ceramic 11 to extend in the stacking direction. .. Therefore, the piezoelectric element 10 as a whole is displaced in the stacking direction.

As shown in FIG. 3, the support frame 21 of the printing unit 20 is made of Invar alloy and has a U-shape. The support frame 21 has the bottom portion 21a on which the piezoelectric element 1 is provided via a temperature compensation material 22 made of aluminum.
The main strut portion 21b and the sub strut portion 21c extend along the side surface while supporting the rear end of 0. And the sub-column 21
A parallel link mechanism 23 by a leaf spring is attached to c, and the parallel link mechanism 23 supports a mover 25 attached to the other end of the piezoelectric element 10 so as to be movable only in the expansion / contraction direction of the piezoelectric element 10. A leaf spring 27 is provided upright on the main column portion 21b of the support frame 21. Further, the leaf spring 29 is similarly attached to the movable element 25 by the leaf spring 27.
The leaf springs 27 and 29 are connected to each other by a connecting portion 31. An arm 33 is attached to the connecting portion 31, and a print wire 35 is attached to the tip of the arm 33.

Power is supplied to the piezoelectric element 10 of the printing unit 20 from a flexible printed circuit board (hereinafter referred to as FPC).
37). This FPC 37 is shown in FIG.
As shown in FIG. 3, two conductor portions 37a and 37b are formed in a strip shape in the longitudinal direction. Those conductor parts 3
7a and 37b are covered with an insulating material, leaving the connecting portions 37c and 37d at both ends thereof.

One end of the FPC 37 is bent substantially at right angles so that the conductors 37a, 37b and the connecting portion 37c are on the outside and the connecting portion 37d on the end side is on the fold side. .. The connecting portions 37d on the fold side are connected to the external electrodes 14 on the lower surface C of the piezoelectric element 10.
The folds are sandwiched between the piezoelectric element 10 and the temperature compensating material 22 in a state of being bonded so as to come into contact with each other. The pressure contact between the temperature compensating member 22 and the piezoelectric element 10 ensures the conduction between the connecting portion 37d and the external electrode 14.

A resin having high expansion and contraction characteristics and heat dissipation characteristics is applied and fixed around the piezoelectric element 10. This resin also serves to prevent the bent portion of the FPC 37 from returning to the original bent portion.

Next, the overall structure of the print head 40 using the print unit 20 will be described with reference to FIG.

The print head main body 41 includes a disk-shaped portion 41a which also serves as a front housing of the print head 40 and the disk-shaped portion 41.
A cylindrical nose 41b protruding from the center of one surface of a is integrally formed. A guide plate 43 and a front guide plate 45 having 24 small holes formed in the nose portion 41b.
Is attached.

Further, mounting rings 49 are adhesively fixed to the other surface of the disk-shaped portion 41a at four locations via hard rubber 47. Twenty-four printing units 20 are bonded to the mounting ring 49, welded by an electron beam, or fastened by screws. The printing units 20 are arranged radially with respect to the mounting ring 49 at substantially equal intervals.

The printing wire 35 of each printing unit 20 is
The front guide plate 4 is inserted through the small holes of the guide plate 43.
3, the tip of the piezoelectric element 10 extends and retracts from the front guide plate 45 due to the expansion of the piezoelectric element 10.

The base 51 has a ring shape for fixing the bottom portions 21a of the supporting frames 21 over a plurality of printing units 20 in order to suppress the deformation of the supporting frame 21 that occurs when the piezoelectric element 10 expands by applying a voltage. It is a metal piece that improves the printing characteristics of the print head. Base 5
The fixing method of 1 is performed by adhesion or welding such as electron beam welding.

A bowl-shaped side cover 53 having a hole 53a at the bottom is attached to the print head body 41. The side cover 53 is adhered only to the print head main body 41 and does not contact the attachment ring 49 and the print unit 20. In addition, the printing unit 20
Each of the FPCs 37 of the above protrudes outward from the hole 53a at the bottom.

A head substrate 59 is attached to the hole 53a via a substrate spacer 57. As shown in FIG. 6, the head substrate 59 has a shape having an arcuate portion 59a corresponding to the side cover 53 and a rectangular portion 59b connected to the arcuate portion 59a. Corresponding to the mounting state of the printing unit 20, the slits 61 are formed radially with a slight angle to the radial direction. This angle is provided corresponding to the side surface of the support frame 21 because the support frame 21 of the printing unit 20 is formed with a slight angle so that the center becomes narrow.

In the portion of the slit 61 which is close to the arc-shaped portion 59a, the outside is open to the arc-shaped portion 59a. Others have a long hole shape. The length of this long hole is slightly longer than the width of the FPC 37. The substrate spacer 57 of the head substrate 59
A power supply path 59c (see FIG. 1) is formed by a printed wiring on the surface on which is not formed. The head substrate 59 is attached to the side cover 53 so that the printed wiring surface is on the outside.

The FPC 37 of the printing unit 20 passes through the corresponding slit 61 as shown in FIG. In this state, FPC37
The connecting portion 37c of is opposed to the power feeding path 59c in contact with the slit 61. Then, the power feeding path 59c and the connecting portion 37c are soldered. In the soldered state, the FP between the piezoelectric element 10 and the head substrate 59 is reduced.
C37 is in a slightly flexed state. Therefore, the vibration generated in the printing unit 20 is hard to be transmitted to the head substrate 59.

A socket 63 is soldered to the rectangular portion 59b, and a signal line bundle for transmitting a print signal from the printer body is connected to the socket 63.

Print head 40 including this head substrate 59
The rear end is covered with a rubber cap. A resin for heat dissipation is filled inside the cover.

The operation of the print head configured as described above will be described below.

The print signal is supplied to the power feeding path 59c on the head substrate 59 through the socket 63, and the power feeding path 59c.
And to the piezoelectric element 10 via the conductor portions 37a and 37b of the FPC 37. The piezoelectric element 10 receives the signal and expands. Then, the mover 25 moves upward in FIG. 5 and moves the leaf spring 29. Then both leaf springs 27, 2
When 9 bends, the connecting portion 31 tilts, the printing wire 35 at the tip of the arm 33 projects, and the printing medium is printed through the ink ribbon. In this way, the desired printing unit 2
Printing is performed by appropriately driving 0.

The vibration generated in the printing unit 20 is transmitted to the mounting ring 49, but is hardly transmitted to the print head main body 41 because it is blocked by the hard rubber 47. Further, since the FPC 37 is flexed, this vibration is not transmitted to the head substrate 59. Therefore, the vibration generated in the print unit 20 is hardly transmitted to any of the print head main body 41, the side cover, and the head substrate 59 that form the casing of the print head 40. Therefore, the noise emitted from the print head 40 is significantly suppressed.

Next, a process of assembling the print head 40 described above will be described.

First, one end of the FPC 37 is bent substantially at right angles so that the conductors 37a and 37b and the connecting portion 37c are on the outside and the connecting portion 37d on the end side is on the fold side. And each connection portion 37 on the fold side
The folds are sandwiched between the piezoelectric element 10 and the temperature compensating material 22 in a state in which d is bonded so as to be in contact with the external electrodes 14 on the lower surface C of the piezoelectric element 10. The pressure contact between the temperature compensating material 22 and the piezoelectric element 10 ensures the conduction with the external electrode 14. Alternatively, the external electrodes 14 and the connecting portions 37d may be individually bonded using a conductive adhesive.

After the piezoelectric element 10 is assembled in this way, a resin having high expansion and contraction characteristics and heat dissipation characteristics is applied around the piezoelectric element 10 and the bent portion of the FPC 37, and then solidified and fixed. With this solidified resin, F
The PC 37 surely faces downward in FIG.

Next, 24 printing units 20 are attached to the attachment ring 49. And its mounting ring 49
Is attached to the print head body 41. At this time, the printing wire 35 of each printing unit 20 is attached to the guide plate 4 by using a jig.
Pass through the small hole of 3. Also in that state the base 51
Attach. After that, the side cover 53 is attached to the print head main body 41.

In this state, the FPCs 37 of the printing unit 20 have side walls 5 depending on their strength.
It is in a state of protruding from the hole portion 53a at the bottom of No. 3. Further, the head substrate 59 and the substrate spacer 57 are adhered in a state where their shapes are matched with each other in advance. The head substrate 5 in which the substrate spacer 57 is adhered to the side cover 53.
Attach 9. At this time, FP for each slit 61
Pass through the end of C37. The FPC 37 is substantially limited in the degree of freedom of deformation in two directions (front and back directions) as compared with a conventionally used conductor pin (122 in FIG. 12) and has sufficient flexibility in that direction. Therefore, the work is much easier than the case of connecting via pins. After inserting all the FPCs 37 into the slits 61, the substrate spacers 57 and the side covers 53 are bonded. After that, the FPC 37 is slightly bent, and the FPC 37 is pushed back until the connection portion of the FPC 37 comes close to the power feeding path 59c of the head substrate 59, and then the substrate and the FP
Solder with C37. Then, after that, the rear end is covered with a rubber cap, and the inside is filled with a resin for heat dissipation.

Next, another embodiment of the piezoelectric element 10 will be described with reference to FIG. In this embodiment, the piezoelectric element 70
An insulating layer 71 having a predetermined thickness is provided in advance between the power feeding positions of the both outer electrodes 14 on the lower surface C. Then, the external electrode 14 is provided thereafter. By doing so, it is possible to reliably prevent a short circuit between both electrodes when the external electrode 14 is formed, so that it is possible to improve the yield at the time of manufacturing and also to suppress the generation of leakage current. There is.

The insulating layer 71 may be provided after forming the external electrode 14. Even in this case, the generation of leakage current can be surely suppressed.

Further, the shape of the external electrode 14 is not limited to the above example, and may be, for example, the shape shown in FIG.

Next, another embodiment of the shape of the FPC 37 will be described with reference to FIGS. 9 and 10. In the piezoelectric element 80 used in this embodiment, the feeding position 81 of the external electrode 81
a is a position below the side of the piezoelectric element 80. Also FPC8
3 has a substantially T-shape as shown in FIG. In this example, by bending both arms 83a of the FPC 83 as shown in FIG. Adhere with a conductive adhesive so that both contacts are not short-circuited. By doing so, even if the resin is not coated around the FPC 83 as in the previous embodiment,
The other end of the FPC surely faces the slit 61.

If the FPC is made longer and is inserted into the slit 61 and then the surplus portion is cut off, the inserting step becomes easier.

Others The present invention can be variously modified without departing from the spirit thereof.

[0049]

As is apparent from the above description, the print head of the present invention can greatly improve the assembly efficiency of the print head by improving the mechanism for supplying power to the piezoelectric element of each piezoelectric unit. It is possible.

Further, the present invention has an excellent effect that the contact portion such as a soldering portion has a high durability and the noise is small.

[Brief description of drawings]

FIG. 1 is a perspective view for explaining a connection state between a print unit and a head substrate according to an embodiment of the present invention.

FIG. 2 is a perspective view for explaining the shape of the piezoelectric element of the above embodiment.

FIG. 3 is a perspective view illustrating the configuration of the printing unit according to the above embodiment.

FIG. 4 is a perspective view illustrating the shape of the FPC in the above embodiment.

FIG. 5 is a cross-sectional view illustrating the overall configuration of the print head of the above embodiment.

FIG. 6 is a front view for explaining the shape of the head substrate in the above embodiment.

FIG. 7 is a perspective view illustrating another embodiment of the piezoelectric element.

FIG. 8 is a perspective view showing another embodiment of the piezoelectric element.

FIG. 9 is a perspective view illustrating another embodiment of the piezoelectric element.

FIG. 10 is an FPC applied to the piezoelectric element shown in FIG.
FIG.

11 is a perspective view showing the shape of a printing unit applied to the piezoelectric element shown in FIG.

FIG. 12 is a sectional view illustrating the configuration of a conventional print head.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Piezoelectric element 21 Support frame 27,29 Leaf spring which comprises a motion transmission mechanism 31 Connection part which comprises a motion transmission mechanism 33 Arm which comprises a motion transmission mechanism 35 Printing wire 37 FPC 37a, 37b corresponding to a flexible sheet member Conductor 59 Head substrate 59c Power supply path

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[Procedure amendment]

[Submission date] May 22, 1992

[Procedure Amendment 1]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 1

[Correction method] Change

[Correction content]

[Figure 1]

[Procedure Amendment 2]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 6

[Correction method] Change

[Correction content]

[Figure 6]

Claims (1)

[Claims] 1. A piezoelectric element that expands and contracts when a voltage is applied, a motion transmission mechanism that transmits the expansion and contraction movement of the piezoelectric element to a print wire that stamps a print medium, and a piezoelectric element and the motion transmission mechanism are supported. In a print head having a plurality of printing units including a supporting frame, the printing head has two conductor portions extending in the longitudinal direction and is attached to the printing unit so that one end of each conductor portion is electrically connected to each electrode of the piezoelectric element. A flexible sheet member, a slit-shaped hole through which the flexible sheet member is inserted, and a power supply path that is electrically connected to the conductor portion of the flexible sheet member inserted in the slit-shaped hole A print head having a substrate.