JPH05208507A - Wire dot printing head - Google Patents

Abstract

PURPOSE:To prevent the damage to the stabilization of printing to be caused by the reduction of magnetic flux generated by an electromagnet following the temperature rise of a printing head, and not offsetting sufficiently the flux of the permanent magnet. CONSTITUTION:A spacer 10 continuously connected with a route section of a leaf spring 4 and a face provided with a yoke 6b of the leaf spring 4 are disposed facing the opposite side in a spring charging type printing head, and a bypass plate 11 continuously connected with the spacer 10 and disposed in a torus shape and integrating a plurality of plate-shaped projections being in the same number of magnetic circuits and side magnetic coils 12 on the plate- shaped projections of the bypass plate 11 are provided. The magnetic flux generated by a permanent magnet 8 running through the bypass plate 11 is eliminated by applying electric current to the side magnetic coils 12 in the opening operation at the time of temperature rise by the arrangement, and also the magnetic flux generated by the permanent magnet 8 is reduced correspondingly to the reduction of the bypass plate flux generated by electromagnetic coils 7 to surely offset the magnetic flux generated by the permanent magnet 8.

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 prints on a recording medium by selectively driving a plurality of print wires.

[0002]

2. Description of the Related Art Conventionally, this type of print head is constructed as shown in FIG. In the figure, 1 is a head frame whose front surface (left side in the drawing) is formed in a tubular shape,
A plurality of print wires 2 are arranged in the head frame 1. The tip portion of the printing wire 2 is guided and supported by a guide 3 provided at the tip of the head frame 1.

A magnetic circuit for driving the print wires 2 is provided corresponding to each of the print wires 2 and an annular leaf spring 4 provided continuously on the rear surface (right side in the figure) of the head frame 1. The armature 5 fixed to the leaf spring 4, a yoke 6b having a suction surface 6a on the core portion facing the armature 5, an electromagnetic coil 7 mounted on the core portion of the yoke 6b, and an outer peripheral portion of the yoke 6b. Permanent magnet 8 connected to the end surface, leaf spring 4, and permanent magnet 8
It is composed of a ring yoke 6c sandwiched between the two.

An arm 9 is fixed to the armature 5, and the base end of the printing wire 2 is fixed to the arm 9.

In the print head having such a structure, the armature 5 is attracted to the attraction surface 6a of the yoke 6b by the attraction force of the permanent magnet 8 during non-printing.
As a result, the leaf spring 4 is held in a bent state.

When a current is applied to the electromagnetic coil in this state, a magnetic flux in the opposite direction to the magnetic flux generated by the permanent magnet 8 is generated on the attraction surface 6a, and the magnetic fluxes cancel each other out, so that the attraction force of the attraction surface 6a disappears. For this reason, the armature 5 is the leaf spring 4
When the elastic strain energy stored in the
The printing operation is started by separating from a.

That is, the print wire 2 fixed to the armature 5 via the arm 9 is guided by the guide 3 and protrudes from the tip of the head frame 1. Then, the printing wire 2 collides with the platen 15 via the ink ribbon 13 and the printing paper 14, and at this time, the ink attached to the ink ribbon 13 is transferred to the printing paper 11 to perform the printing operation. Incidentally, FIG. 5 shows a state immediately after the printing operation.

After the printing operation is completed, when the current applied to the electromagnetic coil 7 is cut off, the armature 5 is again attracted to the attraction surface 6a of the yoke 6b by the magnetic flux of the permanent magnet 8 to perform the return operation. The suction surface 6 of the armature 5 described above
A series of printing operations are completed by the opening operation from a and the suction operation.

In recent years, there has been a demand for higher quality printing and higher speed printing in this print head, and various proposals have been made to meet this demand.

Among these proposals, there is a method of improving the quality of printing by, for example, lengthening the moving stroke of the printing wire 2 and increasing the printing power. There is also a method of increasing the rigidity of the leaf spring 4 and the natural frequency to increase the opening speed of the armature 8 to increase the speed.

[0011]

In the conventional print head described above, the temperature of the coil rises due to a large number of repeated printing operations. Therefore, since the resistance of the coil increases, the value of the current flowing through the coil decreases, and therefore the magnetic flux of the electromagnet decreases, and the magnetic flux of the permanent magnet cannot be canceled sufficiently.

This delays the start of armature movement and impairs the release of elastic strain energy, thus impairing the stability of printing. Further, in order to increase the speed of the print head, it is necessary to improve the movement speed of the armature and the wire. However, due to the above reasons, the print speed of the print head is limited by the characteristic deterioration at high temperature.

Assuming that the amount of magnetic flux of the permanent magnet is kept low as a means for eliminating the above-mentioned drawbacks, when the temperature of the coil is not sufficiently raised, after the armature and the wire are once opened, In the return exercise,
Since the attraction force by the permanent magnets is small, the armature and the wire are not returned easily, which also impairs the printing stability. Therefore, there is a problem that speeding up becomes difficult.

It is an object of the present invention to provide a wire dot type print head in which the start timing of armature movement is constant regardless of temperature and stable printing can be obtained.

[0015]

In order to achieve the above object, a wire dot type print head according to the present invention has an armature for driving a printing wire supported by an elastic member, and a suction surface facing the armature. And a permanent magnet and an electromagnet, and a magnetic circuit including a yoke that attracts the armature to the attraction surface by the permanent magnet and releases the armature from the attraction surface by energizing the electromagnet, and the magnetic circuit with the temperature rise And a magnetic temperature correction circuit for performing magnetic compensation.

In the magnetic temperature correction circuit, the spacer connected to the root of the elastic member is opposed to the surface of the elastic member opposite to the surface on which the yoke is provided, and the magnetic temperature correction circuit is connected to the spacer. And a coil provided on the plate-shaped protrusion of the bypass plate.

[0017]

[Function] By applying a current to the side magnetic coil in the open motion at the time of temperature rise, the magnetic flux generated by the permanent magnet penetrating the bypass plate is canceled and the magnetic flux generated by the electromagnetic coil is reduced. Reduce the magnetic flux,
It surely cancels the magnetic flux from the permanent magnet.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. 1 and 2 are vertical sectional views showing a print head according to an embodiment of the present invention.

In the figure, the print wire 2 guided and supported by a guide 3 provided at the tip of the head frame 1 is driven by a drive device composed of a magnetic circuit. This magnetic circuit is composed of an annular leaf spring 4 connected to the rear surface of the head frame 1, an armature 5 fixed to the leaf spring 4, and a central core portion arranged to face the armature 5. Suction surface 6
A yoke 6b having a, an electromagnetic coil 7 mounted on the yoke 6b, a permanent magnet 8 connected to the end face of the outer periphery of the yoke 6b, and a leaf spring 4 and a permanent magnet 8 are arranged between the permanent magnet 8 and the permanent magnet 8. A ring yoke 6c, a spacer 10 connected to the leaf spring 4, a bypass plate 11 fixed by being sandwiched between the head frame 1 and the spacer 10, and a side magnetic coil 12 provided on the plate-like protrusion of the bypass plate 11. It is configured to include.

In the present embodiment, the bypass plate 11 is provided with the same number of plate-shaped projections as the magnetic circuit as shown in FIG. 4 in an annular shape, and the inner circle position thereof is set to the same degree as the inner position of the leaf spring 4, It is sandwiched between the head frame 1 and the spacer 10 at the outer peripheral portion thereof, and the side magnetic coil 12 is arranged substantially at the center of the plate-like projection of the bypass plate. A spacer 10 is inserted between the leaf spring 4 and the bypass plate 11 and has a thickness sufficient to maintain a distance between the bypass plate 11 and the side magnet coil 12 that does not hinder the operation of the armature 5.

With the above arrangement, the printing operation of the present invention is as follows.

First, the case where the temperature of the print head is low will be described. FIG. 2 shows a state before the printing operation, in which no current is applied to the electromagnetic coil 7, so that the armature 5 is attracted to the attraction surface 6a of the yoke 6b by the attraction force of the permanent magnet 8 and is attached to the leaf spring 4. Is bent.

However, since the print head is provided with the bypass plate 11, the magnetic flux generated by the permanent magnet 8 penetrates the yoke 6b, the armature 5, and the leaf spring 4 as shown by the solid arrow in FIG. The yoke 6b, the armature 5, and the bypass plate 11 are penetrated as indicated by a dashed arrow.

When a current is applied to the electromagnetic coil 7 from this state, the magnetic flux generated by the permanent magnet 8 and the magnetic flux generated in the opposite direction by the electromagnetic coil 7 cancel each other out, and the armature 5 releases the elastic strain energy of the leaf spring 4. Is released from the suction surface 6a, and printing with the printing wire 2 is performed.

FIG. 3 shows a state immediately after the print wire 2 reaches the print medium.

When the current applied to the electromagnetic coil 7 is cut off in this state, the armature 5 is restored to the permanent magnet 8
Is quickly adsorbed to the suction surface 6a of the yoke 6b and returns to the original state. Then, a series of printing operations are completed by this returning operation.

Next, the case where the print operation is repeated and the temperature of the print head rises will be described. FIG. 1 shows a state immediately before the armature 5 is released from the suction surface 6a of the yoke 6b. When the temperature of the print head becomes higher than a certain temperature, a current is applied to the side magnetic coil 12 during the opening operation, so that the magnetic flux penetrating the yoke 6b by the permanent magnet 8 and the armature 5 and the bypass plate 11 is
The opposite magnetic flux generated by the side magnet coil 21 cancels each other out, so that the attraction force of the attraction surface 6a of the yoke 6b against the armature 5 by the permanent magnet 8 becomes small. During the returning operation of the yoke 6b of the armature 5 to the attraction surface 6a, the application of the current to the side magnet coil 12 is interrupted and the original attraction force is restored.

By doing so, the magnetic flux due to the electromagnetic coil 7 decreases due to the temperature rise, and the magnetic flux penetrating the attraction surface 6a by the permanent magnet during the opening operation of the armature 5 is reduced, and the permanent magnet is reduced. By reliably canceling the magnetic flux due to the magnetic flux generated by the electromagnetic coil, a stable armature opening operation can be obtained regardless of the temperature.

[0029]

As described above, according to the present invention, the spacer connected to the root of the leaf spring and the spacer opposite to the surface of the leaf spring opposite to the surface on which the yoke is provided are connected to the spacer and arranged in an annular shape. The bypass plate is formed by integrating the same number of plate-shaped protrusions as the magnetic circuit in the outer peripheral portion, and the plate-shaped protrusions of the bypass plate are equipped with the side magnetic coil. By applying, in response to the decrease of the magnetic flux by the electromagnetic coil,
It is possible to reduce the magnetic flux penetrating the attraction surface of the permanent magnet during the opening operation of the armature.Therefore, the magnetic flux generated by the permanent magnet is reliably offset by the magnetic flux generated by the electromagnetic coil, and the opening operation equivalent to that at room temperature is obtained. Be done.

Therefore, the start timing of the armature movement is constant regardless of the temperature, stable printing can be obtained, and the speedup is facilitated.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing a print head according to an embodiment of the present invention.

FIG. 2 is a vertical sectional view showing a print head according to an embodiment of the present invention.

FIG. 3 is a vertical sectional view showing a print head according to an embodiment of the present invention.

FIG. 4 is a view showing a bypass plate.

FIG. 5 is a vertical cross-sectional view showing a conventional print head.

[Explanation of symbols]

 1 Head Frame 2 Printing Wire 3 Guide 4 Leaf Spring 5 Armature 6a Suction Surface 6b Yoke 6c Ring Yoke 7 Electromagnetic Coil 8 Permanent Magnet 9 Arm 10 Spacer 11 Bypass Plate 12 Side Magnetic Coil 13 Ink Ribbon 14 Printing Paper

Claims (2)

[Claims] 1. An armature for driving a print wire supported by an elastic member, a suction surface facing the armature, a permanent magnet and an electromagnet, and the permanent magnet attracts the armature to the suction surface. A wire dot type print head comprising: a magnetic circuit including a yoke that opens an armature from a suction surface by energizing the electromagnet; and a magnetic temperature correction circuit that performs magnetic compensation of the magnetic circuit due to temperature rise. 2. The magnetic temperature correction circuit comprises a spacer connected to the root of the elastic member, and a ring-shaped spacer connected to the spacer opposite to the surface of the elastic member opposite to the surface on which the yoke is provided. 2. The bypass plate having the same number of plate-shaped protrusions as the magnetic circuit arranged in the outer peripheral portion integrated with each other, and a coil provided on the plate-shaped protrusion of the bypass plate. Wire dot type print head.