JPH06231946A - Printing actuator - Google Patents

Abstract

PURPOSE: To obtain a print actuator of which print speed is improved, and collision force is enhanced, and moving stroke is increased simultaneously. CONSTITUTION: A rear magnetic unit 68 has a stator provided with magnetic poles 74, 76 opposite to each other, having a permanent magnet 70 inbetween, and a coil 72 is wound on the unit 68 so as to produce a magnetic field in a direction so as to cancel a magnetic field by the permanent magnet 70. An armature 80 with a print wire 84 connected thereto is supported by a plate spring 78 and placed, such that its broadwise direction is in matching with the opposed direction of the magnetic poles 74, 76. A front magnetic unit 86 is placed to a side opposite to the rear magnetic unit 68 with the armature 80 inbetween. The magnetic unit 86 has a stator provided with magnetic poles 92, 94 opposite to each other, having a yoke 88 inbetween, and a coil 90 is wound on the unit 86 so as to produce a magnetic field to attract the armature 80 and placed, such that the broadwise direction of the armature 80 matches with the opposed direction of the magnetic poles 92, 94.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a print actuator, and more particularly to a print actuator suitable for use as a print head of a wire dot printer.

[0002]

2. Description of the Related Art A wire dot printer records pixels on a recording medium by colliding the tip of a printing wire with a platen via a recording medium such as an ink ribbon or paper. However, characters and figures are formed on the recording medium by the arrangement of the pixels. Since the wire dot printer is capable of simultaneous copying and can be constructed in a small size and at a low cost, it has been widely used as an output device for peripheral terminal devices, office computers, personal computers and the like of information processing systems.

By the way, in the wire dot printer, the print head for driving the print wire is an important element that greatly affects the printing performance and reliability of the wire dot printer. The main performances required of the print head are: high print speed, large movement stroke of the print wire, large impact force of the tip of the print wire against the platen, low power consumption, and heat dissipation. Is required, the external dimensions are small, and the cost is low. The moving stroke and the collision force are
Important items for obtaining high print quality even when a large number of sheets are simultaneously copied (for example, 8 to 10 sheets) such as a slip, or when the thickness of a recording medium changes during printing. Is.

In order to meet such requirements, various types of print head structures, particularly print wire drive systems, have been proposed. As an example of the driving method, FIG. 10A shows a print actuator 120 that employs a so-called clapper type driving method.

The print actuator 120 has a rectangular armature 124 to which a print wire 122 is connected. In addition to the clapper type, the armature is generally
Considering the miniaturization of the external dimensions of the print actuator,
A printing wire is connected to one end side in the longitudinal direction of the rectangle and is driven with the other end side as a fulcrum. The armature 124 is biased in the direction of arrow D in FIG. 10 by a tension coil spring 126. A substantially U-shaped stator 128 is arranged on the side opposite to the spring 126 with the armature 124 interposed therebetween, and a substantially U-shaped opening is arranged along the longitudinal direction of the armature 124. A coil 130 is wound around the stator 128.

When printing is performed by the print actuator 120, the coil 130 is energized so that a magnetic field for attracting the armature 124 is generated. As a result, the stator 128 is excited, magnetic flux flows through the stator 128 and the armature 124, the armature 124 is attracted to the stator 128 against the biasing force of the spring, and is moved in the direction of arrow E in FIG. Along with this, the printing wire 122 is moved and printing is performed. However, in the above clapper type driving method, since the magnetic flux flows through the armature 124 along the longitudinal direction of the rectangle, the armature 124 is adjusted according to the outer dimensions of the stator 128.
It is necessary to increase the dimension in the longitudinal direction, and it is also necessary to set the thickness dimension to a predetermined value or more in order to prevent magnetic saturation. Therefore, the weight of the armature 124 is large, so that the inertia is large, and it is difficult to move the armature 124 and the printing wire 122 at high speed.

Further, FIG. 10B shows a print actuator 14 which employs a so-called spring charge type drive system.
0 is shown. In the print actuator 140, the armature 142 is supported by the leaf spring 144, and the stator 146 includes the permanent magnet 148. Further, since magnetic saturation occurs when a magnetic flux is passed through the leaf spring 144, the auxiliary magnetic plate 150 is provided as a bypass path for the magnetic flux. The auxiliary magnetic plate 150 has one end attached to the stator 146 and the other end provided so as to correspond to the armature 142 via a gap.

In this print actuator 140, the armature 142 is attracted to the stator 146 by the magnetic field of the permanent magnet 148 in a normal state, and the leaf spring 144 is displaced from the neutral position of displacement "0" to store energy. ing. When printing is performed, the coil 130 is energized so as to cancel the magnetic field generated by the permanent magnet 148. As a result, magnetic flux is generated by the stator 146, the auxiliary magnetic plate 150, and the armature 1.
The armature 142 flows in the direction of arrow F in FIG. 10 by the energy stored in the leaf spring 144, and the print wire 122 is moved to perform printing.

The print actuator 140 shown in FIG.
As shown in FIG. 0 (B), the armature 142 can be downsized to some extent, but since the magnetic flux flows through the auxiliary magnetic plate 150, the magnetic path length is long and the loss is large. I can't get it to work well. Therefore, it is necessary to provide a strong permanent magnet that generates a strong magnetic field and a coil having a number of turns capable of canceling the magnetic field of this permanent magnet, and it is also necessary to provide the auxiliary magnetic plate 150 as described above. Difficult to convert. In addition, the armature must correspond to the end of the U-shaped end of the stator that is located on the print wire side, so the armature must be offset to the print wire side. The ratio of the amount of movement of the print wire to the amount of movement of the print wire is small. Therefore, it is difficult to increase the movement stroke of the printing wire.

Further, in the print actuator proposed by the present applicant in Japanese Patent Laid-Open No. 61-244559, a stator is formed by a plurality of magnetic poles extending in a predetermined direction, and the armature supported by the leaf spring is The width direction is arranged so as to cross the gap formed between the plurality of magnetic poles.
A coil is wound around the stator. This print actuator energizes the coil to excite the stator, attracts the armature to the stator and stores a force in the leaf spring in advance, and the movement of the armature and the printing wire stops the energization of the coil to stop the armature. By stopping the suction of.

In this print actuator, the direction of the magnetic flux flowing through the armature differs from the conventional direction by 90 °, and a magnetic path is formed by the stator and the armature. Therefore, since there is no risk of magnetic saturation or the like, there is no need to provide a magnetic auxiliary plate or the like, and the magnetic path length can be shortened, so that the magnetic flux generated by energizing the coil efficiently acts on the armature. be able to. Further, since the weight and length of the armature can be reduced, the inertia of the armature can be reduced and the movement amount of the printing wire with respect to the movement of the armature can be increased, thus increasing the printing speed. The effect that can be obtained is obtained.

However, the above-mentioned print actuator is basically of the spring charge type in operation principle, and all the drawbacks of the spring charge type have not been solved. In the spring charge type, the printing speed, that is, the moving speed of the printing wire and the armature corresponds to the resonance frequency of the leaf spring, which depends on the spring constant of the leaf spring. In order to improve the printing speed, it is necessary to increase the spring constant of the leaf spring, and if this can be realized, the collision force of the printing wire will also be improved.

However, since the movement stroke of the printing wire (and the armature) corresponds to the amplitude of the leaf spring, a very large amount of energy is required to increase the spring constant of the leaf spring and increase the movement stroke. As a result, the power consumption and the amount of heat generated by the electromagnet for displacing the leaf spring increase, the external dimensions increase, and the power supply for the drive circuit for the electromagnet also increases. In addition, there is a cost disadvantage. As described above, it has been difficult to simultaneously satisfy the improvement of the printing speed and the impact force and the increase of the moving stroke.

Further, in the print actuator described in the above-mentioned Japanese Patent Laid-Open No. 61-244559, in order to keep the armature attracted to the stator and waiting for the movement of the print wire, the coil is always energized. There is a need to. When printing is actually performed on the recording medium by the print actuator, the waiting time is longer, so that the amount of heat generated by the coil is large and the power consumption is large.

The present invention has been made in consideration of the above facts, and an object of the present invention is to obtain a print actuator capable of simultaneously satisfying an improvement in printing speed, an improvement in collision force, and an increase in moving stroke.

[0016]

In order to achieve the above object, a print actuator according to the present invention comprises a pair of first magnetic poles made of a magnetic material and arranged substantially parallel to each other at a predetermined distance, and a pair of the first magnetic poles. A first stator having a permanent magnet arranged between the first magnetic poles, a first coil wound around the first stator, and a holding means having elasticity, An armature arranged substantially orthogonal to the facing direction of the pair of first magnetic poles and arranged to be attracted to the tip of the first stator by the permanent magnet; and a printing element connected to the armature. A pair of second magnetic poles which are made of a magnetic material and which are made of a magnetic material and which are arranged substantially parallel to each other with no permanent magnets and which are arranged substantially parallel to each other are provided. A second strip arranged to face the tip. And a second coil wound around the second stator, passing through an air gap between the tip of the first magnetic pole and the armature, and connecting the armature to the armature. A first magnetic path is formed across the width direction, and the second magnetic path is formed.
Is characterized in that a second magnetic path is formed which passes through the air gap between the tip of the magnetic pole and the armature and which traverses the armature in the width direction of the armature.

In the invention according to claim 1, the first
After the first stator is energized to excite the first stator in the direction of canceling the magnetic field of the permanent magnet, when the armature moves to a predetermined position, the second coil is energized and the second stator attracts the armature. Direction is excited and the armature is attracted to the second stator, and then the first coil is energized so that the armature is attracted to the permanent magnet with an attraction force smaller than the attraction force of the permanent magnet. It is preferable to further include an excitation control means for exciting the stator.

Further, in the invention described in claim 1,
After the first stator is energized to excite the first stator in the direction of canceling the magnetic field of the permanent magnet, when the armature moves to a predetermined position, the second coil is energized and the second stator attracts the armature. After the armature is attracted by the second stator, the first coil is energized so that the armature is attracted by the permanent magnet with an attraction force larger than the attraction force of the permanent magnet. It is preferable to further include excitation control means for exciting one stator.

[0019]

In the present invention, the armature to which the printing element is connected is held by the elastic holding means, and when the first coil and the second coil are not energized, the armature is the magnetic field of the permanent magnet. As a result, it is attracted to the tip of the first magnetic pole against the restoring force of the holding means. In this state, elastic force is stored in the holding means by the displacement of the holding means. Where the first
When the first coil is energized so that the stator is excited in the direction of canceling the magnetic field of the permanent magnet, the magnetic field of the permanent magnet and the magnetic field generated by the first coil cancel each other, and the armature is stored as described above. Due to the elastic force, it moves in the direction away from the first stator, that is, in the direction approaching the second stator.

On the other hand, the second stator does not have a permanent magnet, the second coil is wound, and the second armature is moved in a direction in which the armature approaches the second stator. When the second coil is energized so that the stator is excited in a direction to attract the armature, the armature is attracted to the second stator by the magnetic field generated by the second coil,
It will be moved toward the second stator while accelerating. Since the printing element is also moved according to the movement of the armature, if the platen and the printing medium are arranged on the downstream side in the moving direction of the printing element, the printing element moves along with the movement of the armature. It will be moved toward the print medium and collided.

As described above, according to the present invention, the moving speed of the armature, the printing element, and the collision force of the printing element do not depend only on the elastic force with respect to the displacement amount of the holding member, that is, the spring constant, but the second coil. It depends to a large extent on the strength of the magnetic field generated by. Therefore, even if the spring constant of the holding member is reduced and the moving stroke of the armature and the printing element is increased, the printing speed and the collision force are not greatly affected, and the energization of the first coil and the second coil is not affected. The printing speed, the collision force, and the moving stroke can be satisfied at the same time.

The first stator is provided with a pair of first magnetic poles which are arranged substantially parallel to each other with a predetermined distance therebetween, and the armature is arranged so that its longitudinal direction is substantially orthogonal to the facing direction of the first magnetic poles. That is, they are arranged so that the width direction thereof substantially coincides with the facing direction. Further, the second stator includes a pair of second magnetic poles that are arranged substantially parallel to each other with a predetermined distance therebetween, and a tip portion of the second magnetic pole faces the tip portion of the first magnetic pole with the armature interposed therebetween. It is arranged to. Therefore,
The facing direction of the second magnetic pole is substantially orthogonal to the longitudinal direction of the armature,
That is, they are substantially the same in the width direction of the armature. This allows
A first magnetic path is formed on the first stator side, passing through a gap between the tip of the first magnetic pole and the armature and passing through the armature in the width direction of the armature. On the stator side of, through the gap between the tip of the second magnetic pole and the armature,
A second magnetic path is formed that passes through the armature across the width of the armature.

Therefore, it is not necessary to provide a bypass path such as a magnetic auxiliary plate in order to reduce the influence of a portion having a high magnetic resistance in the magnetic path, and the magnetic path length of the magnetic flux can be shortened by miniaturizing the armature. It is possible to reduce the loss. Therefore, the magnetic flux generated in the coil can more efficiently act on the movement of the armature, as compared with the conventional case. Further, since the armature is attracted by the permanent magnet without moving the armature, there is no need to energize the first coil and the second coil.
It is possible to reduce power consumption as compared with the print actuator described in Japanese Patent No. 4559.

Further, in the present invention, as described above, the width direction of the armature substantially coincides with the facing direction of the first magnetic pole and the facing direction of the second magnetic pole, and the magnetic flux flows across the width direction of the armature. The print actuator 120 shown in FIG.
The dimension of the armature in the longitudinal direction can be made smaller than that of the above. Therefore, the weight of the armature can be reduced to reduce the inertia, and the movement amount of the printing element with respect to the movement of the armature can be increased to further increase the movement stroke of the printing element.

Further, the stator 128 shown in FIG.
If the stator 146 shown in FIG. 10 (B) is simply arranged on both sides of the armature to form a push-pull type print actuator as in the present invention, the magnetic paths on both sides of the armature are separated. Is difficult, and the magnetic fluxes flowing through the magnetic paths on both sides of the armature interfere with each other, so that the magnetic flux cannot be effectively acted on the movement of the armature as in the present invention, and in some cases, the moving direction of the armature may be different. A situation may occur in which the

On the other hand, in the present invention, the first magnetic path and the second magnetic path
In the first magnetic path and the second magnetic path, the magnetic flux from each stator to the armature and the magnetic flux from each armature to each stator contact the magnetic pole. It passes through the air gap between the poles. Therefore, the magnetic flux flowing through the armature through the first magnetic path sharply decreases as the armature moves away from the first stator. Similarly, the second
The magnetic flux flowing through the armature through the magnetic path of (1) also sharply decreases as the armature moves away from the second stator.

Therefore, for example, with the vicinity of the neutral position of the holding means as a boundary, the magnetic flux passing through the first magnetic path acts on the armature on the first stator side, and the magnetic flux passing through the second magnetic path on the second stator side. Can also be configured to act on the armature. In this way, since the first magnetic path and the second magnetic path are magnetically independent, the magnetic flux flowing through the first magnetic path and the magnetic flux flowing through the second magnetic path do not interfere with each other. Therefore, the magnetic flux flowing in each magnetic path can be efficiently applied to the movement of the armature.

Further, in the invention according to claim 1, after the excitation control means energizes the first coil to excite the first stator in a direction of canceling the magnetic field of the permanent magnet, the armature moves to a predetermined position. Then, the second coil is energized to excite the second stator in a direction to attract the armature, and after the armature is attracted to the second stator, the armature attracts less than the attraction force of the permanent magnet. It is preferable to energize the first coil to excite the first stator so that the permanent magnet is attracted by the force.

As a result, the improvement of the printing speed, the improvement of the collision force, and the increase of the moving stroke can be satisfied at the same time as described above. Moreover, since the armature is attracted to the permanent magnet with a small force after being attracted to the second stator,
The moving speed of the armature becomes lower than that in the case where only the attractive force of the permanent magnet acts, and the size of the noise generated when the attracted armature collides with the tip of the first magnetic pole is reduced. You can

Further, in the invention according to claim 1, the excitation control means energizes the first coil to excite the first stator in a direction of canceling the magnetic field of the permanent magnet, and then the armature moves to a predetermined position. Then, the second coil is energized to excite the second stator in a direction to attract the armature, and after the armature is attracted to the second stator, the armature attracts more than the attraction force of the permanent magnet. It is preferable to energize the first coil to excite the first stator so that the permanent magnet is attracted by the force.

As a result, the improvement of the printing speed, the improvement of the collision force and the increase of the moving stroke can be satisfied at the same time as described above, and the armature is attracted by the second stator and then the permanent magnet is applied with a great force. Because it is sucked into
Compared with the case where only the attractive force of the permanent magnet acts, the moving speed of the armature becomes faster, and the operating speed of the print actuator can be improved.

[0032]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 shows the main part of the wire dot printer according to this embodiment. This wire dot printer includes a platen roll 12 around which a recording medium 10 such as paper is wound. The platen roll 12 is fixed to a shaft 14 rotatably supported by a bearing (not shown), and extends from one end to the other end of the recording medium 10 in the width direction. A gear 16 is attached to one end of the shaft 14. Gear 1 for gear 16
8 meshes with each other, and the gear 18 is fixed to the drive shaft of the motor 20.

Therefore, when the motor 20 is driven, the driving force of the motor 20 is transmitted to the shaft 14 via the gears 18 and 16.
The shaft 14 and the platen roll 12 are rotated in the direction of arrow A in FIG. The rotation of the platen roll 12 conveys the recording medium 10 wound around the platen roll 12. A gear 22 is also meshed with the gear 16 via a gear 21, and the gear 22 is fixed to an end portion of a shaft 24. The shaft 24 is arranged in parallel with the shaft 14 and the platen roll 12, and is rotatably supported by a bearing (not shown). When the motor 20 is driven, a driving force is transmitted to rotate the shaft 24.

A shaft 26 is provided near the shaft 24 in parallel with the shaft 24. An endless belt 28 is wound around both ends of the shafts 24 and 26 (only one endless belt is shown in FIG. 1). On the surface of the endless belt 28, a large number of protrusions 28A that project toward the outer periphery of the endless belt 28 are provided at a constant pitch along the longitudinal direction of the endless belt 28. The shafts 24 and 26 and the endless belt 28 constitute a tractor feeder, and when the recording medium 10 is a continuous paper such as so-called personal computer paper, the endless belt 28 is rotated and the projection 28A is formed.
Are sequentially inserted into the holes provided at both ends of the recording medium 10 in the width direction, and the recording medium 10 is conveyed together with the platen roll 12.

A gear 30 meshes with the gear 16, and the gear 30 is attached to a support shaft of a platen knob 32. The platen knob 32 is exposed to the outside of a casing (not shown) of the wire dot printer, and the user can manually convey the recording medium by rotating the platen knob 32.

On the other hand, a pair of shafts 34 and 36 which are parallel to each other are arranged near the platen roll 12, and a moving block 38 is provided on the shafts 34 and 36. The moving block 38 is slidable along the longitudinal direction of the shafts 34 and 36. A print head 40 to which the present invention is applied is attached to the moving block 38. Although the configuration of the print head 40 will be described later in detail, printing is performed by projecting the print wire, and the print wire is attached so as to project toward the platen roll 12.

An ink ribbon cartridge 42 is locked on the moving block 38. The ink ribbon cartridge 42 houses an endless ink ribbon 44 inside and exposes a part of the ink ribbon 44.
The exposed portion is arranged so as to be located between the platen roll 12 and the tip of the print wire at the above-mentioned print wire protruding portion. Therefore, when the print wire is projected, the ink ribbon 44 is pressed toward the platen roll 12 by the tip of the print wire, and the platen roll 1
Dots are recorded on the recording material 10 wound around 2. The ink ribbon cartridge 42 is replaceable.

An endless belt 46 (only a part of which is shown) is arranged below the moving block 38, and the moving block 38 is locked to a predetermined portion of the endless belt 46. The endless belt 46 has irregularities formed on the inner peripheral surface, and irregularities corresponding to the irregularities are wound around a pair of rollers 48 (only one is shown) provided on the outer periphery. The roller 48 is fixed to the drive shaft of the motor 50. Therefore, when the motor 50 is driven, the roller 48 and the endless belt 46 are rotated, and the moving block 38 moves the shaft 34,
Slide along 36.

Next, the print head 40 will be described. As shown in FIG. 2, the print head 40 is formed by sequentially stacking a cylindrical rear frame 60, a thin plate 62, a cylindrical front frame 64, and a disk-shaped front housing 66. The rear frame 60 and the front frame 64 are made of aluminum having high heat dissipation. Further, a cylindrical protrusion 66A having a predetermined diameter is provided at the center of the front housing 66.
A circular hole 66B is formed along the axis of the print head 40 at the diametrical center of A.

As shown in FIG. 3, a rear magnetic unit 68 is arranged on the inner peripheral side of the rear frame 60. Although only a single magnetic unit 68 is shown in FIG. 3, a large number of magnetic units 68 each having the same configuration are actually used.
Are arranged in an annular shape on the inner peripheral side of the rear frame 60. The magnetic unit 68 includes a flat permanent magnet 70. The permanent magnet 70 has the largest area in the flat plate shape, and two facing surface sides are magnetized to have different polarities, and the surface is the inner wall 60A of the rear frame 60.
Are arranged so as to be substantially orthogonal to and along the axial direction of the print head 40.

An aluminum spacer (not shown) is interposed between each of the plurality of magnetic units 68, and each magnetic unit 68 is held by the spacer. Further, the polarities of the facing surfaces of the permanent magnets 70 of the adjacent magnetic units 68 are the same (see FIG. 9), and due to the synergistic effect of the spacers, the magnetic force between the adjacent magnetic units 68 is increased. It prevents the occurrence of inconvenience due to various interference.

A coil 72 as a first coil is wound around the outer circumference of the permanent magnet 70 so that its axial direction is orthogonal to the surface of the permanent magnet 70. The inner wall 60A of the rear frame 60 is provided with a groove 60B corresponding to the coil 72 for accommodating the coil 72. Further, a pair of magnetic poles 74 and 76 are arranged in parallel to the side of the permanent magnet 70 with the permanent magnet 70 interposed therebetween.
The magnetic poles 74 and 76 are made of a magnetic material and extend toward the plate 62 (upper side in FIG. 3). In this extended portion, the magnetic poles 74 and 76 have a gap corresponding to a size capable of accommodating the thickness of the coil 72. They are facing each other. In the magnetic unit 68, the permanent magnet 70 and the magnetic poles 74 and 76 form a stator.

On the other hand, the plate 62 is made of metal and formed in a substantially annular shape, and a projection 78 is formed on the inner peripheral side thereof so as to project toward the axial center of the print head 40. Although only a single protrusion is shown in FIG. 3, actually, the same number of protrusions as the magnetic units 68 of the rear frame 60 are arranged in an annular shape on the inner peripheral side of the plate 62. . Since the plate 62 is made of metal and has a thin shape, the protrusion integrated with the plate 62 also has elasticity against deformation in the directions of arrows B and C in FIG. 3 and acts as a leaf spring (hereinafter, this protrusion 78 is called a leaf spring 78).

An armature 80 is attached to the tip of each leaf spring 78. The armature 80 is made of a material having a high magnetic permeability, and when the print head 40 is assembled, the lower surface in FIG. 3 corresponds to the tips of the magnetic poles 74 and 76, and the longitudinal direction is the magnetic pole 7.
They are arranged so as to be orthogonal to the facing direction of the magnetic poles 4, 76, that is, so that the width direction thereof coincides with the facing direction of the magnetic poles 74, 76. The armature 80 moves in the arrow B direction and the arrow C direction in FIG. 3 according to the displacement of the leaf spring 78. Also, armature 80
Is a support burr 8 protruding toward the axis of the print head 40.
2 is attached, and a print wire 84 as a print element is attached to the tip of the support burr 82.

The length of the print wire 84 depends on the front housing 6 when the print head 40 is assembled.
6 has a size slightly projecting from the edge portion of the circular hole 66B provided in 6. A guide for the print wire 84 (not shown) is provided on the inner wall of the circular hole 66B of the front housing 66.

A front magnetic unit 86 is arranged on the inner peripheral side of the front frame 64. Although only a single front magnetic unit 86 is shown in FIG. 3, the same number of magnetic units 86 as the magnetic units 68 are actually arranged in an annular shape on the inner peripheral side of the front frame 64. There is. The magnetic unit 86 includes a flat plate-shaped yoke 88, and a coil 90 serving as a second coil is wound around the outer periphery of the yoke 88 similarly to the coil 72. The inner wall 64A of the front frame 64 is also provided with a groove 64B for housing the coil 90.

On the side of the yoke 88, a pair of magnetic poles 92 and 94 are arranged in parallel with each other with the yoke 88 interposed therebetween.
The magnetic poles 92 and 94 are made of a magnetic material and extend toward the plate 62 (downward in FIG. 3).
The magnetic poles 92 and 94 face each other with a gap corresponding to the thickness dimension of the yoke 88 interposed therebetween. In the assembled state of the print head 40, the magnetic poles 92 and 94 have their tips facing the tips of the magnetic poles 74 with the armature 80 in between, and the tips of the magnetic poles 94 with the armature 80 in between. It is arranged so as to face the tip portion of 76.

As a result, the opposing directions of the magnetic poles 92 and 94 are orthogonal to the longitudinal direction of the armature 80, that is, they coincide with the width direction of the armature. In the magnetic unit 86, the yoke 8
8 and the magnetic poles 92 and 94 form a stator. The yoke 88 and the magnetic poles 92 and 94 may be integrally formed.

On the other hand, the control unit of the wire dot printer is
It is configured as shown in FIG. That is, the control circuit 10
Reference numeral 0 includes a CPU, a memory, and the like, and a control signal indicating various instructions such as the start of printing and print data indicating the content to be printed are input from a host (not shown).
The motor drive circuits 102 and 104 are connected to the control circuit 100, and the motor drive circuit 102 is connected to the motor 20.
However, each motor 50 is connected to the motor drive circuit 104.

Further, the switch circuit 1 is included in the control circuit 100.
06 is connected. The switch circuit 106 has the same number of switching elements 106 as the total number of coils of the print head 40.
A, 106B ... Each switching element is connected to the control circuit 100, and the control circuit 100
It is designed to be turned on and off according to the instructions. Each switching element is connected to a power source (not shown) and also connected to each coil of the print head 40, and the control circuit 1
When it is turned on by 00, the connected coil is energized and excited.

Note that FIG. 4 schematically shows the configuration of the switching circuit 106 and the connection relationship between the switching element and the coil. In practice, a flywheel current flows through the coil when the energization of the coil is stopped. In addition, elements such as transistors and diodes are added.

The coils are connected to the switch circuit 106 so that the coils 72 of the rear magnetic unit 68 are connected so that when excited, a magnetic field is generated in a direction that cancels the magnetic field generated by the permanent magnet 70 of the rear magnetic unit 68. Has been done. Further, the coils 90 of the front magnetic unit 86 are arranged such that the directions of the magnetic fields generated when energized by being energized are opposite to each other in the adjacent magnetic units 86. The excitation direction of the coil 72 and the excitation direction of the coil 90 with respect to the arrangement direction of the permanent magnets 70 are schematically shown in FIG.

Next, the operation of this embodiment will be described. When performing printing on the recording medium 10 in the wire dot printer, the control circuit 100 determines the print wire 84 to be moved and the movement timing of the print wire 84 based on the input print data. Then, the motor 20 and the motor 50 are driven to convey the recording medium 10 and move the moving block 38 to the initial position so that the print head 40 corresponds to a predetermined portion of the recording medium 10. While the medium 10 is being conveyed and the moving block 38 is being moved, each print wire 84 is moved in accordance with the determined movement timing, and printing is performed on the recording medium 10.

The movement of the print wire 84 is performed as follows. First, in the standby state before the movement of the print wire 84, the energization of the coil 72 of the rear magnetic unit 68 and the coil 90 of the front magnetic unit 86 is stopped. As described above, the rear magnetic unit 68 of the print head 40 has the permanent magnet 70. Therefore, in this standby state, the magnetic flux passing through the permanent magnet 70 and the magnetic poles 74 and 76 is the magnetic pole 7.
The armature 80 flows by flowing along the width direction of the armature 80 through the air gap between the armatures 80 and the tips of the armatures 80.
A suction force acts on the armature 80 as shown in FIG.
Is attracted to the tips of the magnetic poles 74 and 76 against the restoring force of the leaf spring 78 (hereinafter, the position of the armature 80 at this time is referred to as a standby position). At this time, the leaf spring 78 is displaced, and the restoring force for returning to the neutral position where the displacement is 0 is stored.

When the predetermined print wire 84 is moved,
The control circuit 100 turns on the switching element 106A of the switch circuit 106, and energizes the coil 72 of the rear magnetic unit 68 corresponding to the print wire 84 for a predetermined time (see FIG. 7D). As a result, as shown in FIG. 7E, a current flows through the coil 72 and the rear magnetic unit 68
The stator is excited, and a magnetic field that cancels the magnetic field of the permanent magnet 70 is generated. Therefore, the attraction force to the armature 80 is lost, and the armature 80 and the printing wire 84 are separated from each other by the leaf spring 78.
Due to the restoring force stored in the rear magnetic unit 68 as shown in FIG.
Is moved in the direction of arrow B). Note that, as shown in FIG. 7E, the current flowing through the coil 72 gradually decreases due to the flywheel effect after the energization of the coil 72 is stopped.

On the other hand, the armature 80 moves closer to the front magnetic unit 86 past the neutral position due to inertia.
The control circuit 100 turns on the switching element 106B of the switch circuit 106 a predetermined time before the time when the armature 80 passes through the neutral position, and energizes the coil 90 of the corresponding front magnetic unit 86 for a predetermined time (FIG. 7 ( See A)). As a result, as shown in FIG.
Current flows to excite the stator of the front magnetic unit 86, and the magnetic flux passing through the yoke 88 and the magnetic poles 92, 94 passes through the gap between the tip of the magnetic poles 92, 94 and the armature 80, and the width of the armature 80. The attraction force acts on the armature 80 by flowing along the direction. Therefore, FIG.
As also shown in FIG.
It moves while being accelerated in the direction approaching 6.

This movement is continued until the armature 80 hits the tips of the magnetic poles 92, 94 of the front magnetic unit 86 (until the state shown in FIG. 6 is reached). During this movement, the tip of the print wire 84 contacts the ink ribbon 44, and the recording medium 10 is pressed via the ink ribbon 44, whereby dots are recorded on the recording medium 10.

As described above, when the coil 90 is energized before the predetermined time before the armature 80 passes the neutral position, the armature 80 can be greatly accelerated, but the armature 80 passes the neutral position. It may be energized in accordance with the timing of the movement, and even after the armature 80 has passed through the neutral position, the moving speed is improved compared to the conventional case.

By the way, in the state where the movement of the armature 80 is stopped, the leaf spring 78 is displaced as shown in FIG. 6, and the restoring force for returning to the neutral position where the displacement is 0 is stored. . The control circuit 100 turns off the switching element 106B at the timing when the movement of the armature 80 is stopped, and stops the energization of the coil 90. As a result, the armature 80 is moved by the restoring force stored in the leaf spring 78, as shown in FIG. 7C.
6 is moved in the direction away from (direction of arrow C in FIGS. 3 and 5).

This movement continues even after the neutral position due to the inertia of the armature 80. At this time, the rear magnetic unit 6
Since the excitation of the coil 72 of No. 8 is stopped, the attraction force by the permanent magnet 70 acts on the armature 80 from near the neutral position, and the armature 80 is accelerated (the inclination in FIG. 7C becomes large). (Refer to the part that shows) Rear magnetic unit 68
It is attracted to the magnetic poles 74 and 76 and returns to the standby position shown in FIG.

When the movement of the armature 80 (and the print wire 84) is compared with that of a conventional print head (shown by a broken line) with reference to FIG. 7C, the magnetic head goes from the rear magnetic unit 68 to the front magnetic unit 86. The armature 80 is the coil 9
Due to the suction force generated by 0, it is greatly accelerated from near the neutral position. This is because, as shown in FIG. 8, the kinetic energy of the armature is gradually attenuated after passing the neutral position (shown by a broken line) in the past, whereas the print head 40 of the present embodiment is in the neutral position. It is also clear from the fact that the value does not decay even after passing and the value slightly increases.

As a result, as compared with the conventional case, FIG.
As shown in FIG. 5, the time from the start of movement of the armature 80 to the recording of dots by the print wire 84 and the return to the standby position is short, so the printing speed is high, and the standby position and the armature 80
Since the distance from the peak position of movement of the
4 has a large movement stroke, and as shown in FIG. 8, the armature 80 when the print wire 84 records dots.
(And the printing wire 84) has high kinetic energy,
The collision force of the tip of the printing wire 84 against the platen roll 12 is large. As described above, the print head 40 according to the present invention simultaneously achieves an improvement in printing speed, an improvement in collision force, and an increase in moving stroke, as compared with the related art.

Further, in the print head 40 of the present embodiment, the strength of the magnetic field generated by the coil 90 is weakened by, for example, reducing the current flowing through the coil 90 of the front magnetic unit 86 or reducing the number of turns of the coil 90. When it is changed in the direction, as shown by the curves D, E, and F in FIG. 8, the kinetic energy of the armature 80 changes in the decaying direction as the strength of the magnetic field decreases. Although illustration is omitted, when the strength of the magnetic field is changed in the direction of increasing it, the kinetic energy changes in the increasing direction. When the kinetic energy of the armature 80 changes as described above, the moving speed (printing speed) of the armature 80 and the printing wire 84 and the collision force of the printing wire 84 change accordingly.

As described above, in the print head 40, the printing speed and the collision force do not depend only on the spring constant of the leaf spring 78, but largely depend on the strength of the magnetic field generated by the coil 90. Further, the magnetic poles 74, 7 of the rear magnetic unit 68
6, the magnetic poles 92 and 94 of the front magnetic unit 86,
It is also possible to increase the movement stroke as shown by the curve G (the movement stroke is increased by α in FIG. 8) by widening the interval in advance and increasing the energization time to the coil 90. It should be noted that the moving stroke is increased so that the armature 80 moves the magnetic pole 9 of the front magnetic unit 86.
When it is prevented from colliding with 2, 94, FIG.
As indicated by the curve J, the change in the position of the armature 80 has a smooth waveform.

The armature 80 is arranged so that the width direction thereof coincides with the facing direction of the magnetic poles 74, 76 of the rear magnetic unit 68 and the facing direction of the magnetic poles 92, 94 of the front magnetic unit 86. . This allows the coil 7
When 2 or the coil 90 is excited, the magnetic flux flows across the width direction of the armature 80 through the gap between the tip of each magnetic pole and the armature 80. Therefore, a bypass path such as a magnetic auxiliary plate is unnecessary, the magnetic path length is short, and the loss is very small. Therefore, as compared with the related art, the magnetic flux generated in the coil can be efficiently applied to the movement of the armature, and the magnitude of the current flowing in the coil can be suppressed to be low. Further, the size and weight of the armature 80 are also very small as compared with the conventional one.

When there is a demand to reduce the noise emitted from the print head 40, the control circuit 100 causes the armature 80 to return to the standby position when the armature 80 is returned from the front magnetic unit 86 side. Is a permanent magnet 7
The coil 72 may be excited so that it is attracted by the permanent magnet 70 with an attraction force smaller than that of zero. this is,
For example, it can be realized by energizing the coil 72 at a timing corresponding to the pulse K ₁ shown in FIG. 7D and flowing a current through the coil 72 as shown by a curve K ₂ in FIG. 7E.

As a result, the kinetic energy of the armature 80 and the print wire 84 when returning from the front magnetic unit 86 side to the standby position gradually attenuates with a peak near the neutral position as shown by the curve K ₄ in FIG. To do. Accordingly, as shown by the curve K ₃ in FIG.
The inclination of the position change of the armature 80 becomes smaller than that when the armature is not energized, and the armature 80 and the print wire 84 reach the standby position while being gradually decelerated. Therefore, the armature 80 has the magnetic poles 74, 7 of the rear magnetic unit 68.
The collision force when hitting 6 is very small, and the noise emitted from the print head 40 is reduced.

In addition, when there is a demand to further improve the printing speed of the print head 40, when the armature 80 is returned from the front magnetic unit 86 side to the standby position, the control circuit 100 causes the armature to move. It suffices to excite the coil 72 so that 80 is attracted to the permanent magnet 70 with a greater attraction force than the attraction force of the permanent magnet 70. This can be realized by, for example, energizing the coil 72 at a timing corresponding to the pulse L ₁ shown in FIG. 7D and passing a current through the coil 72 as shown by a curve L ₂ in FIG. 7E. it can.

As a result, the kinetic energy of the armature 80 and the printing wire 84 when returning from the front magnetic unit 86 side to the standby position gradually increases with a peak near the neutral position as shown by the curve L ₄ in FIG. To do. Along with this, as shown by the curve L ₃ in FIG.
As compared with the case where the armature is not energized, the inclination of the position change of the armature 80 becomes large, and the armature 80 and the printing wire 84 reach the standby position while being gradually accelerated. Therefore, the time required for the armature 80 to reach the standby position is shortened, and the printing speed of the print head 40 is improved.

Although the example in which the printing wire 84 is used as the printing element has been described above, the present invention is not limited to this, and various printing elements that perform printing by being moved can be applied. Is possible.

[0071]

As described above, according to the present invention, a pair of first magnetic poles made of a magnetic material and arranged substantially in parallel at a predetermined distance, and a permanent magnet arranged between the pair of first magnetic poles. And a first coil having the first stator, a first coil wound around the first stator, and a holding means having elasticity, and the longitudinal direction is substantially orthogonal to the facing direction of the pair of first magnetic poles. And a print element connected to the armature, which is arranged so as to be attracted to the tip of the first stator by the permanent magnet, and which does not have a permanent magnet and is made of a magnetic material and is separated by a predetermined distance. A second stator provided with a pair of second magnetic poles arranged substantially parallel to each other, and a second stator arranged such that a tip end portion of the second magnetic pole faces the tip end portion of the first magnetic pole with the armature interposed therebetween; And a second coil wound around the two stators, Improvement in printing speed, it is possible to satisfy improvement of the impact force and increase the movement stroke simultaneously,
That is an excellent effect.

[Brief description of drawings]

FIG. 1 is a perspective view showing a main part of a wire dot printer according to an embodiment.

FIG. 2 is a perspective view showing an appearance of a print head.

FIG. 3 is an exploded perspective view of the print head when FIG. 2 is cut along the line 3-3 ′.

FIG. 4 is a block diagram showing a schematic configuration of a control unit of the wire dot printer.

FIG. 5 is a schematic view showing a state in which an armature is located at a standby position.

FIG. 6 is a schematic view showing a state in which an armature is attracted to a front magnetic unit.

FIG. 7A is a timing of energizing the coil 90,
(B) is a timing chart showing a change in current flowing through the coil 92, (C) is a change in position of the armature, (D) is a timing of energizing the coil 72, and (E) is a timing chart showing change in current flowing through the coil 72. Is.

FIG. 8 is a diagram showing changes in kinetic energy of the armature and the printing wire when the armature and the printing wire are moved.

FIG. 9 is a schematic diagram schematically showing an exciting direction of a coil of a rear magnetic unit and an exciting direction of a coil of a front magnetic unit with respect to an arrangement direction of permanent magnets.

FIG. 10 shows a conventional printing wire drive system (A)
FIG. 3 is a schematic configuration diagram for explaining the principle of a clapper type and (B) a spring charge type.

[Explanation of symbols]

 10 print head 72 coil 74 magnetic pole 76 magnetic pole 78 leaf spring 80 armature 84 printing wire 90 coil 92 magnetic pole 94 magnetic pole 100 control circuit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tetsuo Sugano 1623 Shimotsuruma, Yamato-shi, Kanagawa 14 Japan AIBM Co., Ltd. Yamato Works

Claims (3)

[Claims] 1. A first magnetic device comprising: a pair of first magnetic poles made of a magnetic material and arranged substantially parallel to each other at a predetermined interval; and a permanent magnet disposed between the pair of first magnetic poles. A stator, a first coil wound around the first stator, and a holding means having elasticity, the longitudinal direction of which is substantially orthogonal to the facing direction of the pair of first magnetic poles, and the permanent magnet. An armature arranged so as to be attracted to the tip portion of the first stator, a printing element connected to the armature, and made of a magnetic material without a permanent magnet and arranged substantially in parallel at a predetermined distance. A pair of second magnetic poles,
A second stator arranged so that the tip of the magnetic pole faces the tip of the first magnetic pole with the armature sandwiched therebetween; and a second coil wound around the second stator. And passing through a gap between the tip of the first magnetic pole and the armature,
And a first magnetic path is formed which passes through the armature across the width of the armature, and passes through a gap between the tip of the second magnetic pole and the armature,
A print actuator, wherein a second magnetic path passing through the armature across the width of the armature is formed. 2. The second coil is energized when the armature moves to a predetermined position after energizing the first coil to excite the first stator in a direction of canceling the magnetic field of the permanent magnet. Energize to excite the second stator in a direction to attract the armature, and after the armature is attracted to the second stator, the armature is attracted to the permanent magnet with an attraction force smaller than the attraction force of the permanent magnet. 2. The print actuator according to claim 1, further comprising excitation control means for energizing the first coil to excite the first stator as described above. 3. The second coil is energized when the armature moves to a predetermined position after energizing the first coil to excite the first stator in a direction of canceling the magnetic field of the permanent magnet. Energize to excite the second stator in a direction to attract the armature, and after the armature is attracted to the second stator, the armature is attracted to the permanent magnet with an attraction force larger than the attraction force of the permanent magnet. 2. The print actuator according to claim 1, further comprising excitation control means for energizing the first coil to excite the first stator as described above.