JPH0517034B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a print head for a wire dot printer, and more particularly to a so-called spring charge type print head in which a wire is projected by elastic energy stored in a leaf spring.

In order to improve the printing speed of a dot printer, it is necessary to increase the response frequency of the print head.
The spring charge method has more stable operation and better response than the electromagnetic suction method, but
As described below, in the conventional structure such as that disclosed in Japanese Patent Application Laid-Open No. 56-37176, it took a long time for the wire to come to rest after it returned, and there was a limit to its responsiveness. In other words, as shown in Fig. 4, which shows the change in the displacement of the conventional wire over time, the wire returns to its original position after colliding with the recording paper, but at that time, it crosses the standby position once and returns to the standby position.
Repeat the vibration several times in the same way. As a result, not only does the time required for the wire to rest in the standby position become longer, but when driven at high frequencies, the movement of the motor system including the wire becomes unstable, which limits the responsiveness of the head. . The present invention aims to suppress the above-mentioned residual vibration and realize high responsiveness.

To achieve this objective, a printhead according to the invention comprises a lever having a wire connected to one end;
A leaf spring that fixes the other end of this lever and biases the lever in the printing direction, a permanent magnet that uses magnetic attraction force to bias this lever to the standby position, and elastic energy stored in the leaf spring that is biased to the standby position. The degaussing coil is energized in the direction of canceling the magnetic flux of the permanent magnet in order to release the lever and drive the lever, and the area where the lever is largely deflected from the one end on the back of the lever when the lever almost reaches the standby position is almost at the same time. The device is characterized in that it includes a stopper made of an elastic body and having a surface that comes into contact with the stopper.

The present invention will be explained based on an embodiment shown in FIGS. 1 and 2. FIG. 1 is a sectional view of the head, and FIG. 2 is an exploded view of a plurality of drive units attached to the head. In both figures, a core 2 is fixed to a lower yoke 3, a permanent magnet 1 is sandwiched between it and an upper yoke 4, and fixed using a fixed shaft 12. A lever 8 is swaged together with the free end of the leaf spring 7 by a plunger 6. The lever 8 is made of a thin plate, and its tip is shaped to wrap around the wire 9, and the two are fixed by resistance welding, brazing, or the like. The leaf spring 7 is fastened and fixed between the upper yoke 4 and the presser plate 10 by a fixed shaft 12. The two electrode terminals 15 and 16 of the coil 5 wound around the core 2 have spring properties.

The above-mentioned drive unit 30 can be individually attached to and detached from the head body after assembly and adjustment. The drive unit is assembled into the head body by engaging the protrusion 10a of the drive unit in the guide hole 13a of the head frame 13, and then presses the corresponding pattern of the wiring board 17 against the electrode terminals 15, 16 to establish an electrical connection. A rubber sheet 14 is interposed between the head frame 13 and the drive unit to prevent assembly problems due to variations in length between the drive units and to prevent the generation of noise. Next, the head is assembled by elastically fixing the back cover 25 to the head frame 13 using the fixing spring 26. The lever guide 24 has a slit for guiding the side surface of the lever 8, and has the function of preventing vibration in a direction perpendicular to the plane of FIG. Furthermore, a part 10c of the presser plate 10
is used as a stopper when the lever 8 is in the standby position, and a stopper 11 made of a rubber material is attached to the collision surface with the lever 8.

Next, the operation will be explained. The plunger 6 is attracted to the core 2 by the magnetic flux of the permanent magnet 1 and retains the leaf spring 7 in a biased manner. When the coil 5 is energized in a direction to cancel the magnetic field, the attracted state is released and the lever 8 is rotated by the elastic force of the leaf spring 7, causing the wire 9 fixed at the tip to protrude. The wire 9 collides with an ink ribbon and recording paper (not shown) to form dots.
After the current is cut off, the plunger 6 is attracted again, and the wire 9 also returns to the standby position. At this time, the lever 8 also collides with the stopper 11 almost at the same time as the core 2 collides with the plunger 6. Therefore, as shown in FIG. 3, which shows the change in wire displacement over time in this embodiment, the wire 9 does not go over the standby position, but quickly comes to rest at the standby position with a very slight bounce. Therefore, the motion system including the wire operates stably and moves without disturbance, especially during high frequency drive, so high responsiveness can be achieved.

Furthermore, the engaging surfaces of the presser plate 10 and the stopper 11 each form a slope as shown in FIG. It can be adjusted horizontally). Therefore, even if the standby position of the lever 8 varies due to errors in parts processing accuracy, etc., the stopper 11 can be slid in the vertical direction and set at the optimal position. In addition, since the lever 8 and the stopper 11 engage in plane in this way, when the lever 8 returns, the area where the lever is largely deflected from the end where the wire 9 is fixed on the back of the lever is approximately At the same time, it comes into contact with the stopper 11.

In this embodiment, the stopper 11 is made of polyurethane and has sufficient hardness to restrict the stroke of the lever in the standby position, and sufficient impact resistance and abrasion resistance.

Furthermore, according to the structure shown in this embodiment, the impact caused by the impact between the core 2 of the suction section and the plunger 6 is alleviated, so that the wear and deformation of this impact section is significantly reduced.

Furthermore, since there is no residual vibration of the lever 8 and there is no disturbance in the movement of the wire during high frequency motion, the bending load applied to the wire is reduced and the wire life is extended.

As described above, the printing head according to the present invention is
When a lever, one end of which is connected to a wire and the other end fixed to a leaf spring, almost reaches the standby position, the area where the lever is largely deflected from the one end of the lever almost simultaneously contacts the surface of the stopper of the elastic body. Since the movement of the lever converges instantaneously,
The next movement is carried out quickly and the printing speed can be improved. Further, since the impact applied to the stopper is dispersed over a wide contact surface and the resulting stress is reduced to a small value, fatigue of the material of the lever is suppressed, furthermore, wear of the stopper is reduced and the durability of both can be improved. Furthermore, if the stress applied to the stopper is small, the amount of deformation of the stopper will be small, so the overshoot when the lever returns will be small, improving the movement of the lever and improving the responsiveness of the print head. Become.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a print head showing an embodiment of the present invention, and FIG. 2 is an exploded view showing its drive unit.
FIG. 3 is a diagram showing temporal changes in wire displacement of the print head of the present invention, and FIG. 4 is a diagram showing temporal changes in wire displacement of a conventional example. 1: Permanent magnet, 2: Core, 5: Coil, 6: Plunger, 7: Leaf spring, 8: Lever, 10: Holding plate, 11: Stopper, 30: Drive unit.

Claims (1)

[Scope of Claims] 1. A lever with a wire connected to one end; a plate spring that fixes the other end of the lever and urges the lever in the printing direction; and a lever that biases the lever to a standby position by magnetic attraction. a permanent magnet; a degaussing coil energized in a direction to cancel the magnetic flux of the permanent magnet in order to release the elastic energy stored in the leaf spring biased to the standby position and drive the lever; When the standby position is reached,
A print head comprising: a stopper made of an elastic body having a surface from the one end of the back surface of the lever that is abutted almost simultaneously with a region where the lever is largely deflected.