JPH059938U - Printing head device - Google Patents

Abstract

(57) [Abstract] [Purpose] To reduce the leakage flux between the core 7 forming the electromagnet 6 for swinging the armature 2 with the printing wire 3 and the yoke 10 forming a closed magnetic path for the core 7. The print head is downsized and the power consumption is reduced. [Structure] The first member 12 of the yoke 10 is connected to the core 7
Extends substantially parallel to the direction in which the armature 2 extends. The flat plate ring-shaped second member 13 joined and fixed to the tip of the first member 12 is extended in the radial center direction which is the facing portion between the armature 2 and the core 7. The side surface of the first member 12 and the core 7
The distance between the side surface and the side surface of the core 7 is set to be larger than the distance between the central end of the second member 13 and the side surface of the core 7.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a structure of an impact dot print head device that drives a print wire by switching between excitation and non-excitation of an electromagnet.

[0002]

[Prior Art]

 This type of print head device is disclosed, for example, in Japanese Patent Application Laid-Open No. 62-236759 by the present applicant, and as shown in FIG. A base portion of a leaf spring 103, which is radially arranged on the lower surface side of the main body 102 and elastically supports each armature 101, and a ring-shaped permanent magnet 104 are provided on the back surface (lower surface) of the head main body 102 and a bottomed cylindrical shape. The rear yoke 105 is sandwiched and fixed between the rear yoke 105 and the substantially square flange portion 105a in a plan view, and the electromagnet is arranged so as to face the rear surface (lower surface) of each of the armatures 101 from the bottom plate portion 105b near the inner diameter of the cylinder of the rear yoke 105. There is a structure in which a core 107 as 106 is integrally projected. The armature 101, the rear yoke 105, the spacer 108, and the front yoke 109 are each a ferromagnetic material.

In this configuration, the magnetic flux of the permanent magnet 104 causes the magnetic flux of the permanent magnet 104 to return to the permanent magnet 104 via the spacer 108, the front yoke 109, the armature 101, the core 107, the rear yoke 105 such as the bottom plate portion 105b (see FIG. 5). (See the chain double-dashed line). When the print head is not in operation (when the electromagnet is not excited), the armature 101 is attracted to the end surface (front surface) of the core 107 by the magnetic field of the permanent magnet 104, and the print wire 100 is retracted to a rest position. And the strain energy is stored in the leaf spring 103. When the print head is operated, the coil portion 110 at the selected armature 101 is energized to cancel the magnetic path by the permanent magnet 104, and the elastic energy of the plate 103 causes the print wire 100 to project forward. The chur 101 is swung.

[0004]

[Problems to be solved by the device]

 By the way, in order to accurately manufacture the dimensions and position of the core 107 having a complicated shape in the rear yoke 105, currently, a precision casting method such as a lost wax method or a die casting method or a sintering method is adopted. When the rear yoke 105 is manufactured by casting or injection sintering as described above, if a recess (large space) is provided between the side surface of the columnar core 107 and the inner surface of the outer peripheral cylindrical portion 105c of the rear yoke 105, casting isoform It is difficult to manufacture because it cannot be pulled out.

On the other hand, in order to increase the magnetic force of the permanent magnet 104, it is necessary to increase the area of the N and S surfaces (the portion facing the flange portion 105a of the rear yoke, the spacer 108, etc.). Further, if an attempt is made to increase the required area of the permanent magnet 104 without increasing the planar shape (planar area) of the head body 102, as described above, the flange portion 105a of the rear yoke 105 is moved from the end of the outer peripheral cylindrical portion 105c. There was no choice but to form it so as to project outward in the radius. In other words, the gap between the side surface of the columnar core 107 and the inner surface of the outer peripheral cylindrical portion 105c of the rear yoke 105 is reduced.

As described above, when the gap between the side surface of the columnar core 107 and the inner surface of the outer peripheral cylindrical portion 105c of the rear yoke 105 is small, in addition to the closed magnetic path required for swinging the armature 101, the core 107 The permeance of the bypass magnetic path between the side surface and the side surface of the rear yoke 105 or between the core 107 and the spacer 108 (the reciprocal of the magnetic resistance, which is a measure of the ease of passage of the magnetic flux) becomes large. That is, the leakage of magnetic flux at unnecessary points increases. For this reason, the efficiency of the magnetic circuit is deteriorated, and it is necessary to take measures such as increasing the required area of the permanent magnet and the voltage to be applied to the coil section 110.

As disclosed in Japanese Unexamined Patent Publication No. 63-53055, the inner side surface of the tubular portion of the rear yoke becomes closer to the side surface of the core as it approaches the front end of the core (the portion facing the armature). Although a configuration in which the rear yoke is formed so as to approach each other is disclosed, even with this configuration, there are the same drawbacks as described above regarding the molding of the rear yoke, and the rear yoke side surface is gradually inclined toward the core side surface. Therefore, it cannot contribute to the reduction of the permeance of the bypass magnetic path between the core and the rear yoke.

It is an object of the present invention to reduce the leakage of magnetic flux at unnecessary places such as between the core and the yoke, and to realize the downsizing of the print head and energy saving.

[0009]

[Means for Solving the Problems]

 In order to achieve the above object, the present invention comprises an armature elastically supported by a print wire at its tip and an electromagnet disposed so as to face the middle part between the tip and the base of the armature. In a print head including a core, at least the armature and a yoke that cooperates with the core to form a closed magnetic path, and a permanent magnet provided in the closed magnetic path, the yoke extends toward the armature. A first member that extends substantially parallel to the direction and extends toward the base end of the armature, and a surface that extends from the first member toward the facing portion between the armature and the core, and that surface is in contact with the permanent magnet. It is composed of a second member, and the distance between the side surface of the first member and the side surface of the core is set to be larger than the distance between the center side end of the second member and the side surface of the core.

[0010]

【Example】

 Next, an embodiment embodying the present invention will be described. Reference numeral 1 is a head body made of metal such as aluminum in a print head, and reference numeral 2 is a rear side of the head body 1 which is radially arranged in a plan view. The armature is made of a magnetic material, and the base end of the printing wire 3 is bonded and fixed to the tip of the armature 2.

The print wire 3 is arranged along the longitudinal direction in a cylindrical nose portion 1 a projecting from the front end of the head body 1, and the midway portion of the print wire 3 is slidable on the guide body 4. When the tip of the printing wire 3 protrudes from the tip of the nose portion 1a, it is printed on the paper located on the front surface of the platen 5 through an ink ribbon (both not shown). This is a possible configuration.

The electromagnet 6 which is a driving means for driving each armature 2 has a columnar shape made of a ferromagnetic material which is radially arranged in a plan view (see FIG. 2) so as to face the lower surface of each armature 4. It comprises a core 7 and a coil portion 9 in which an insulating winding is wound around a bobbin 8 fitted on the outer peripheral surface of each core 7. Reference numeral 10 is a yoke made of a ferromagnetic material for forming a closed magnetic circuit in cooperation with the armature 2 and the core 7. The first embodiment of the yoke 10 is, as shown in FIG. A bottom plate portion 11 on which 7 is integrally erected; a cylindrical first member 12 formed from the outer periphery of the bottom plate portion 11 toward the substrate 1b of the head body 1 and further to the base portion of the armature 2, and the first member. 12 is formed separately from the first member 12 and extends from the tip of the first member 12 toward the facing portion between the armature 2 and the core 7 and is constituted by a flat plate ring-shaped second member 13. The inner side surface of the cylindrical first member 12 is formed to be substantially parallel to the side surface of the core 7, and the distance (L1) between the inner side surface of the first member 12 and the side surface of the core 7 is The distance is set to be wider (larger) than the distance (L2) between the end of the second member 13 near the center and the side surface of the core 7. The first member 12 and the second member in the first embodiment are separately manufactured, and the lower surface of the outer peripheral portion of the second member 13 is bonded and fixed to the tip of the first member 12 later. The central portion (free end closer to the inner side of the radius) is arranged so as to approach the tip end of the core 7 and the facing portion of the armature 2.

As shown in FIG. 2, the second member 13 is formed so that the outer circumference is substantially square and the inner circumference is substantially circular in plan view. After the second member 13 is formed separately from the first member 12 in the yoke 10, the first member 12 and the second member 13 are joined and fixed, so that the core 7 and the bottom plate portion 11 of the yoke 10 and the first member 12 are joined together. The three members including the one member 12 have a U-shaped cross section as shown in FIG. Therefore, even when a precision casting method such as the lost wax method is used to integrally form the three parts, a complicated core is not required and the production is extremely simple.

As shown in the second embodiment of FIG. 4, the first member 12 and the second member 13 of the yoke 10 are integrally formed, and the bottom plate portion 11 and the core 7 portion of the yoke 10 are separately formed. After being integrally formed, if the outer peripheral edge of the bottom plate portion 11 is joined to the rear end portion of the first member 12, the first member 12 and the second member 13 have an L-shaped cross section. In addition, since the annular plate-shaped bottom plate portion 11 and the core 7 are L-shaped in cross section, casting and manufacturing are simplified. It should be noted that the tubular first member 12 may be divided into a component including the second member 13 and a component including the bottom plate portion 11 and the core 7 at an intermediate portion in the height direction.

The ring-plate-shaped permanent magnet 14 is joined and fixed to the front surface of the second member 13, and a ring-plate-shaped spacer 15 made of a ferromagnetic material is joined and fixed to the front surface of the permanent magnet 14. The outer circumference and the inner circumference of the permanent magnet 14 and the spacer 15 are substantially the same as those of the second member, and the chamfered portion 16 is formed so as to face the core 7 over the entire inner circumference of the second member 13 and the spacer 15. By providing the above, the gap distance between the inner peripheral corners of the second member 13 and the spacer 15 and the tip of the core 7 is prevented from becoming too close. In addition, a synthetic resin adhesive with high magnetic permeability is used as the bonding material for these members (components) so as not to reduce the lines of magnetic force.

Reference numeral 17 is a film-shaped residual sheet in which the base is joined and fixed to the front surface of the spacer 15, and free of the abrasion-resisting and thermal-resistive sheet 17 such as polyfluoroethylene or polyimide. It is arranged so that the end side is interposed between the armature 2 and the core 7. Reference numeral 18 denotes a ring-shaped front yoke made of a ferromagnetic material, and each of the armatures 2 can be movably fitted into a radial slit 19 formed by cutting out the front yoke 18. On the front side of the front yoke 18, a leaf spring 20 formed of an elastic plate material is joined and fixed in a state of being sandwiched by a pair of thin plate-shaped spacers 21 and 22 made of a magnetic material. The supporting piece 23 of the leaf spring 20 is joined and fixed to the front surface of the base of the armature 2, and the armature 2 is configured to be swingable by the bending elasticity of each supporting piece 23.

Reference numeral 24 is a printed wiring board adhered to the lower surface of the bottom plate portion 11 of the yoke 10, and reference numeral 25 is a terminal portion provided on the bobbin of the coil portion 9 for connecting the coil portion 9 and the printed wiring board 24. ing. With such a configuration, when the print head is in a non-operating state, the magnetic lines of force of the permanent magnet 14 extend from the permanent magnet 14 to the spacer 15, the front yoke 18, the armature 2, the core 7, the yoke 7, as shown by the two-dot chain line in FIG. A magnetic path that returns to the permanent magnet 14 via 10 is formed. As a result, each armature 2 is attracted to the front surface of the core 7, and each printing wire 3 is held at the rear rest position. Along with this, strain energy is accumulated in the leaf spring 20. During the printing operation, the coil portion 9 of the electromagnet 6 corresponding to the selected armature 2 is energized in a pulsed manner, and the core 7 is temporarily excited so as to cancel the magnetic path by the permanent magnet 14. When the strain energy of 20 is released, the corresponding armature 2 swings in the forward direction, the printing wire 3 advances, the dots are printed on the paper, and printing is performed. When the excitation is finished, the armature 2 is moved to the rest position again. It moves backward and is held in position.

In this way, the coil portion 9 is energized in a pulsed manner to cancel the magnetic path of the permanent magnet 14, so that the bottom plate portion 11 of the core 7 and the yoke 10, the first member 12 and the second member 13 are formed. When a magnetic flux is generated, or conversely, the energization of the coil portion 9 is stopped and the magnetic flux by the permanent magnet 14 is formed in the bottom plate portion 11, the first member 12 and the second member 13 of the core 7 and the yoke 10. At this time, as in the present invention, the side surface of the core 7 and the inner side surface of the cylindrical first member 12 of the yoke 10 are formed parallel to each other along the direction in which the core 7 extends toward the armature 2. , The central portion of the second member 13 extending from the first member 12 toward the facing portion between the armature 2 and the core 7 by a distance (L1) between the inner side surface of the first member 12 and the side surface of the core 7. Side end face and Since it is set to be larger than the gap distance (L2) from the side face of the permanent magnet 14, the necessary area of the second member 13 in the yoke facing the magnetic poles (N pole, S pole) of the permanent magnet 14 is secured, and The amount of magnetic flux leaking from the inner side surface of the member 12 to the side surface of the core 7 can be reduced.

In addition, the chamfered portions 16 and 16 are formed on the end surfaces of the spacer 15 and the second member 13 that are closer to the tip (front end) of the core 7 and that are closer to the center of the radius of the second member 13. It is also possible to further reduce the amount of leakage of magnetic flux by increasing the approach gap to the side surface of the core 7. Therefore, in order to swing the armature 2, it is possible to reduce the driving power of the magnetic circuit in which the magnetic flux is repeatedly generated and extinguished.

[0020]

[Operation and effect of the device]

 As described above, according to the present invention, in the print head including the electromagnet 6 having the yoke 10 that cooperates with the armature 2 and the core 7 to form a closed magnetic circuit, the yoke 10 is moved so that the core 7 faces the armature 2. A first member 12 extending substantially parallel to the extending direction and extending toward the base end of the armature 2, and a surface extending from the first member 12 toward the facing portion between the armature 2 and the core 7. And a second member 13 whose surface is in contact with a permanent magnet. The distance between the side surface of the first member 12 and the side surface of the core 7 is defined by the center end of the second member 13 and the core 7. Therefore, according to the present invention, the efficiency of the above-mentioned magnetic circuit is improved, the drive power of the print head is reduced, and the low consumption print head is provided. Can provide .

Further, in the conventional art, while the required area of the second member 13 which is the flange portion of the yoke 10 facing the magnetic poles (N pole, S pole) of the permanent magnet 14 is secured, the first portion which becomes the tubular portion of the yoke 10 is secured. In order to keep the first member 12 away from the side surface of the core 7, the second member 13 serving as the flange portion is made to project radially outward from the tip of the first member 12 serving as the tubular portion of the yoke 10. Therefore, the outer peripheral dimension of the first member 12 inevitably becomes large. Therefore, there has been a problem that the outer peripheral dimension of the substrate 1b of the head body 1 also becomes large and the outer dimension of the print head becomes too large. However, in the present invention, the first member 12 of the yoke 10 is largely separated from the side surface of the core 7, while the second member 13 is provided radially inward from the front end of the first member 12 (closer to the center of the radius). It is possible to achieve compactness without having to increase the outer peripheral dimension of the body, and hence the outer peripheral dimension of the print head.

[Brief description of drawings]

FIG. 1 is a side view showing a cutaway part of a first embodiment of a print head.

FIG. 2 is a sectional view taken along the line II-II of FIG.

FIG. 3 is a perspective view of essential parts of the print head.

FIG. 4 is a cross-sectional view of essential parts of a second embodiment of the print head.

FIG. 5 is a partial side elevational view of a conventional print head.

[Explanation of symbols]

 1 head body 2,101 armature 3,100 printing wire 6,106 electromagnet 7,107 core 9,110 coil part 10 yoke 14,104 permanent magnet 105 rear yoke 11 bottom plate part 12 first member 13 second member 15,21,22 Spacer 16 Chamfered portion 17 Resilient sheet 18 Front yoke 20,103 Leaf spring

Claims (1)

Claims for utility model registration: 1. An armature having a print wire at its tip and elastically supported, and an electromagnet arranged so as to face the middle part between the tip and the base end of the armature. In a print head having a core that forms a closed magnetic circuit in cooperation with the armature and the core, and a permanent magnet that is provided in the closed magnetic circuit, the yoke facing the armature. A first member extending in a direction substantially parallel to the extending direction and extending toward the base end of the armature; and a surface extending from the first member toward a facing portion between the armature and the core, and a permanent magnet on the surface. The second member is in contact with the second member, and the distance between the side surface of the first member and the core side surface is set to be larger than the distance between the center side end of the second member and the core side surface. And the printing head device.