JPH0584932A - Printing head device - Google Patents

Abstract

PURPOSE:To improve a printing quality, by accelerating attenuation of vibration of a printing mechanism such as an arm after application of voltage to a piezoelectric element. CONSTITUTION:A wedge type supporting side stopper 16 is slid and moved in front of an auxiliary stay part 6b on a part fading on a stopper 15 of an arm side on the back of an arm 8, through which the tip side of a posture of the arm 8 is moved forward a little in the direction of a nose part 3 at a part of the stopper 15 of the arm side. With this construction, a return position of the arm 8 after application of voltage to a piezoelectric element 5 is controlled and attenuation of vibration of the arm is accelerated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a so-called dot impact print head device in which a piezoelectric element is expanded / contracted by applying a voltage, and the expansion / contraction motion is transmitted to a print wire that strikes a print medium such as paper. It is about.

[0002]

2. Description of the Related Art The present applicant has previously filed Japanese Patent Application No. 2-26721.
In the application of No. 9, the front end of the print wire that is printed on the print medium is configured to project and retract forward from the nose portion of the head body, and the base portion of the print wire is fixed to the front end portion of the print mechanism. We proposed a printing unit with a piezoelectric element that expands and contracts when a voltage is applied to one end.

More specifically, as shown in FIGS. 1 to 3, the print head comprises a head body 1 having a substantially disk shape in a front view and a cylindrical cover 2 covering the back surface thereof. The nose portion 3 is made to project from the central portion of the front surface of 1. A plurality of printing units 4 are radially arranged in the head body 1. Each printing unit 4 is provided with a piezoelectric element 5 which is formed by adhering piezoelectric ceramics in a laminated form and has a long front and rear direction, and is attached to the front end of the piezoelectric element 5 so as to expand the expansion and contraction motion of the piezoelectric element and transmit it to the printing wire 7. Printing mechanism 9 and this interlocking transmission mechanism 9
And a support frame 6 extending rearward from the back surface of the head body 1 for supporting the piezoelectric element 5. The support frame 6 surrounds both sides of the piezoelectric element 5 in the longitudinal direction and the rear end portion of the piezoelectric element 5, so that the main strut portion 6a, the sub strut portion 6b, and the rear end portion 6 are provided.
and c are integrally formed in a U shape.

The printing mechanism 9 converts expansion and contraction of the piezoelectric element 5 into rotational movement of the arm 8 so that the amount of movement of the printing wire 7 attached to the tip of the arm 8 is increased. The printing mechanism 9 for this purpose uses an Eden spring composed of two parallel leaf springs. That is, one ends of the first plate spring body 12 and the second plate spring body 13 are integrally connected to the connecting portion 10 made of a rigid body, and are connected in a so-called Π shape in a side view. The base end of the first plate spring body 12 is brazed and fixed to one side surface of the support frame 6, while the base end of the second plate spring body 13 is also brazed and fixed to a mover 14 attached to the front end of the piezoelectric element 5. To do. Then, the extending direction of the first leaf spring body 12 and the second leaf spring body 13 is set to be parallel to and opposite to the extending direction of the printing wire 7.

In the above-mentioned prior art, as shown in FIG. 2, the piezoelectric element 5 and the mover 14 are moved by the arrow B when a voltage is applied.
When it extends in the direction, the connecting portion 10 at the tip of the leaf springs 12, 13 is pivotally displaced in the direction of arrow A (see the chain double-dashed line in FIG. 2). As a result, the print wire 7 on the tip side of the arm 8 is
Moves forward in the direction of the nose portion 3. When the voltage application to the piezoelectric element 5 is stopped, the tip side of the arm 8 is moved to the above-mentioned two leaf spring bodies 1.
Due to the restoring force of the elastic deformation of Nos. 2 and 13, it retracts from the nose section 3.

An arm-side stopper 15 is provided on the back surface of the arm 8 in a stationary state, and a support-side stopper 16 is provided at the front end of the sub strut portion 6b.

In this case, conventionally, the arm side stopper 15 is fixed to the arm 8 in advance, and then the stopper 1 is attached.
The gap between 5 and the support side stopper 16 should be "0", or a very small gap (for example, 20 microns).
The support side stopper 16 is fixed to the front end of the sub strut portion 6b with an adhesive.

[0008]

Thus, the gap between the arm-side stopper 15 and the support-side stopper 16 is zero,
Alternatively, if there is a very small gap, the following problems occur. That is, when the arm 8 is in a stationary state (neutral state), there is no external force acting on both the first leaf spring body 12 and the second leaf spring body 13. When a voltage is applied to the piezoelectric element 5 in this state and the arm 8 is driven to rotate, a state in which the tip side of the arm 8 is positioned in front so that the gap between the stoppers 15 and 16 becomes large, The front end side retreats and the state in which the rear surface of the arm side stopper 15 collides with the front surface of the support side stopper 16 is repeated to return to the initial neutral state. In that case, when the vibration is damped to some extent and a gap is always present between the stoppers 15 and 16, there is no choice but to wait for the natural damping of the elastic deformation of the leaf spring bodies 12 and 13. Then, the print quality becomes uneven. That is, when a voltage is applied to the piezoelectric element 5 while the print wire 7 is moving forward (the tip side of the arm 8 is moving toward the nose portion 3),
The arm 8 is accelerated so that its tip end side approaches the nose portion 3, so that the print becomes dark. On the other hand, when a voltage is applied to the piezoelectric element 5 with the print wire 7 retracted (the tip side of the arm 8 is moving in a direction away from the nose portion 3), the tip end side of the arm 8 approaches the nose portion 3. What should be operated in this way is canceled by the force in the opposite direction, and the print becomes lighter in density. This phenomenon becomes more prominent as the printing speed increases.

Further, if the neutral position is set so that there is a gap between the arm-side stopper 15 and the support-side stopper 16, the setting of the gap tends to be erratic for each printing unit 4, causing an error. Printing wire 7
However, when the tip of the printing wire 7 is polished along the surface of the cylindrical platen, it is difficult to align the tips of the printing wires 7 with each other. The present invention aims to solve these technical problems.

In order to achieve the above-mentioned object, according to the present invention, a printing mechanism, to which a printing wire is attached and which is elastically supported by an elastic body, is moved forward by the displacement of a piezoelectric element by the application of a voltage to perform printing, In the print head device that comes into contact with the stopper when the mechanism retracts,
The contact surface of the stopper is provided in front of the rear surface of the printing mechanism when the elastic body is in an inelastically deformed state.

[0011]

EXAMPLE Next, an example will be described. The basic structure of the print head device is substantially the same as that of the conventional example shown in FIG. That is, reference numeral 1 denotes a head body having a substantially disk shape in a front view, and the cover 2 has a cylindrical portion 2 integrally extending from the outer peripheral edge of the substantially disk-shaped connecting portion 2a toward the back surface side of the head body 1.
b and the head body 1 and the cover 2 are made of aluminum alloy.

Reference numeral 4 is a printing unit, and a plurality (24 in the embodiment) of printing units 4 are radially arranged on the back side of the head body 1. On the front surface of the head body 1, a hollow nose portion 3 in which a predetermined number of guide plates 22 for moving and guiding the print wires 7 in each print unit 4 are installed is provided.

The printing unit 4 is mounted on the front end of the piezoelectric element 5 which is formed by adhering piezoelectric ceramics in a laminated form, and is attached to the front end of the piezoelectric element 5 to expand the expansion and contraction motion of the piezoelectric element and transmit the expanded movement to the printing wire 7. And a support frame 6 extending rearward from the back surface of the head body 1 for supporting the printing mechanism 9 and the piezoelectric element 5. The support frame 6 is integrally formed in a U-shape by a main strut portion 6a, a sub strut portion 6b, and a rear end portion 6c so as to surround both sides in the longitudinal direction and the rear end portion of the piezoelectric element 5. In addition,
The sub strut portion 6b may be brazed and fixed to the rear end portion 6c.

When a voltage is applied, the piezoelectric element 5 expands and contracts in the stacking direction (longitudinal direction), and the piezoelectric element 5 shrinks as the temperature rises. The compensator 25 is inserted between the rear end portion 6c of the support frame 6 and the rear end of the piezoelectric element 5 and fixed by an adhesive.

The printing mechanism 9 has a substantially triangular arm 8 as viewed from the side, which is formed by brazing the base of the printing wire 7 to the tip, and a plate-shaped first plate extending rearward in the longitudinal direction of the main support 6a. The spring body 12 and the second plate spring body 1 which is also plate-shaped
3 and a rigid connecting portion 10 that connects the ends of the spring bodies 12 and 13, and the connecting portion 10 is fitted and fixed to the base end portion of the arm 8 by brazing or the like. The base end portion of the first leaf spring body 12 is fixed to the side surface of the main strut portion 6a by brazing, while the base end portion of the second leaf spring body 23 is fixed to the front end surface of the piezoelectric element 5 by brazing or the like. It is also fixed to the side surface of the mover 14 by brazing or the like.

Then, as shown in FIG. 2, when the piezoelectric element 5 expands in the direction of arrow B by applying a voltage, the both leaf spring bodies 1 are
The connecting portions 10 of 2 and 13 are rotationally displaced in the direction of arrow A, the displacement amount is enlarged by the arm 8, and the printing wire 7 is driven so as to project from the nose portion 3. When the voltage application is released, the elastic force of both spring bodies 12 and 13 causes the arm 8 to rotate in the opposite direction, and the arm-side stopper 15 made of resin or the like abuts the support-side stopper 16 and damps while repeating vibration. Then stop.

By the way, a voltage is applied to the piezoelectric element 5 to elastically deform the first leaf spring body 12 and the second leaf spring body 13 to rotate and drive the arm 8, and then the arm 8 is in an initial state. In order to promote the damping of vibration when returning to
In the present invention, the arm side stopper 15 or the support side stopper 16 is fixed in a state where the arm 8 which is a part of the printing mechanism 9 is advanced in the printing direction.

The first embodiment is shown in FIGS. 2 and 4. In this embodiment, the arm-side stopper 15 made of metal, ceramic, synthetic resin, or the like is fixed to the back surface of the arm 8 with an adhesive or the like in advance. On the other hand, the inclined guide surface 1 is formed such that the front end surface of the sub-column portion 6b extends along the longitudinal direction of the arm 8 and approaches the rear surface of the arm 8 as the arm 8 extends toward the base end side.
Form 7. The support-side stopper 16 that is fixed after being moved along the inclined guide surface 17 is formed in a wedge shape such as a trapezoid in a side view or a triangle. An adhesive is applied in advance to the contact surface of the inclined guide surface 17 and / or the support side stopper 16, the support side stopper 16 is moved along the inclined guide surface 17, and the arm side stopper 15 is provided on the front surface of the support side stopper 16. The support side stopper 16 with the arm 8 slightly advanced by pushing the back side of the
Fix the position of. In the embodiment, the length of the arm 8 is about 16
mm, a support-side stopper 16 is installed at a position about 10 mm from the base end of the arm 8, and the support-side stopper 16 is forcibly pushed so that the tip of the arm 8 advances from the free state by about 20 microns.

In this case, as shown in FIG. 4 (a) or (b), a ridge portion 18 is formed on the front end surface of the auxiliary column portion 6b, and the inclined guide surface 17 is formed on the ridge portion 18. On the other hand, on the back surface of the support-side stopper 16, a groove portion 19 slidably fitted in the ridge portion 18 is formed. By doing so, the work of mounting and moving the support-side stopper 16 can be facilitated, and the adhesion area between the support-side stopper 16 and the sub-column portion 6b can be increased.

5 and 6 show the arm-side stopper 15
In the embodiment in which the arm 8 is moved slightly with respect to the position-fixed support side stopper 16 so that the tip side of the arm 8 approaches the nose portion 3, the back side of the arm 8 becomes closer to the base side. An inclined guide surface 20 of a stepped ridge that approaches the stopper 16 is formed, while a groove portion 21 slidably fitted to the inclined guide surface 20 is formed on the front surface of the arm-side stopper 15.

Reference numeral 23 shown in FIG. 3, which is a cross-sectional view taken along the line III-III in FIG. 2, indicates a portion 4 which is arranged across the other side of the mover 14 and the sub-column 6b. The four-node link mechanism member 23 is made of an elastic material such as a spring plate, and the wide side plate portions 23a, 23a thereof are substantially H-shaped in a side view.
A notch hole 24 having a shape such as a hole is formed, and the left and right wide side plate portions 23a and 23a are provided on the outer diameter side of the notch hole 24 and the auxiliary strut portion 6b.
When the piezoelectric element 5 expands and contracts by applying a voltage by brazing and fixing it to the front and back side surfaces of the movable element 14 and the front and back side surfaces of the movable element 14, respectively, the left and right wide side plate portions 23a, 2 of the four-node link mechanism member 23
3a is elastically deformed into a parallelogram shape in a side view so that the movable element 14 can be moved in parallel along the longitudinal direction of the positionally fixed sub-column portion 6b.

In this way, if the mover 14 is constructed so as to move in parallel along the longitudinal direction of the sub strut portion 6b, in other words, linearly along the longitudinal direction of the piezoelectric element 5, the piezoelectric ceramic will be formed. Bending force does not act on the laminated adhesive surface, and the laminated portion and the adhesive surface are not inadvertently peeled off.

According to each of these embodiments, the arm 8 is previously prepared.
Is lifted so that the tip end side approaches the nose portion 3 side, and the return side amplitude when the arm 8 vibrates by the first leaf spring body 12 and the second leaf spring body 13 is regulated so as to be small. be able to. Therefore, it is possible to accelerate the damping of the vibration of the arm 8 after driving the piezoelectric element 5.

The arm side stopper 15 may be integrally formed on the arm 8 or the support side stopper 16 may be integrally formed on the head main body side such as the auxiliary column portion 6b. Also, the arm side stopper 1 in the arm 8
One or a plurality of through holes 8a as shown in FIG. Then, the arm 8 is set so that the through hole 8a is located in the cavity (cavity) hollowed out in the shape of the arm-side stopper 15 in the molding die, and synthetic resin is injected into the molding die. Since the synthetic resin is cured in the through hole 8a as well, the mounting strength of the arm side stopper 15 can be improved. By applying a voltage to the piezoelectric element 5 that corresponds to the distance that brings the tip of the arm 8 closer to the nose portion 3, at a position where the stoppers 15 and 16 come into contact with each other while the arm 8 is forcibly advanced. You may fix it. The fixing means may be welded instead of the adhesive. The positions of the both stoppers are not limited to the arm 8 and the position facing the arm 8 and can be provided at appropriate positions of the printing mechanism 9.

Further, as means for accelerating the vibration damping of the arm 8 or reducing the secondary bound of the arm 8,
After assembling the stoppers 15 and 16, the stoppers 15 and 16 may be connected to each other by a connecting member having elasticity and resistance to expansion and contraction. At this time, if silicone rubber having a low viscosity is used, it can be injected between both stoppers with a syringe or the like by utilizing the low surface tension without using a molding die or the like. However, it is needless to say that it is necessary to use a silicone rubber having a high heat resistance because the temperature increases due to the driving of the print head for a long time.

[0026]

As described above, according to the present invention, the stopper is fixed at the position where the printing mechanism and the stopper come into contact with each other while the printing mechanism such as the arm is forcibly advanced in the printing direction. By doing so, damping of vibration of the printing mechanism can be promoted. Therefore, it is possible to eliminate unnecessary movement of the print wire after driving the piezoelectric element, and it is possible to improve print quality.

[Brief description of drawings]

FIG. 1 is a side sectional view of a print head.

FIG. 2 is an enlarged side view of a main part.

3 is a sectional view taken along the line III-III of FIG.

4A is an embodiment shown in a sectional view taken along the line IV-IV in FIG. 2, and FIG. 4B is another embodiment shown in a sectional view taken along the line IV-IV in FIG.

FIG. 5 is a side view of an essential part showing another embodiment.

6 is a cross-sectional view taken along the line VI-VI of FIG.

FIG. 7 is a side view of an essential part showing still another embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Head main body 3 Nose part 5 Piezoelectric element 6 Support frame 6b Sub strut part 7 Printing wire 8 Arm 9 Printing mechanism 12 1st leaf spring body 13 2nd leaf spring body 15 Arm side stopper 16 Support side stopper 17 and 20 Inclination guide surface 18 ridges 19 and 21 grooves

Claims (1)

[Claims] 1. A printing mechanism, to which a printing wire is attached and which is elastically supported by an elastic body, is moved forward for printing by displacement of a piezoelectric element due to application of a voltage, and is brought into contact with a stopper when the printing mechanism retracts. In the print head device as described above, a contact surface of the stopper is provided in front of a rear surface of the printing mechanism when the elastic body is in an inelastically deformed state.