Supporting structure of an armature of a wire dot printer head

Information

  • Patent Grant
  • 6682233
  • Patent Number
    6,682,233
  • Date Filed
    Monday, March 18, 2002
    22 years ago
  • Date Issued
    Tuesday, January 27, 2004
    20 years ago
Abstract
In a wire dot printer head of the present invention, an armature is formed by coupling a magnetic circuit formation member having a supported piece with one end inserted into a cavity formed on a surface of a yoke to an arm coupled to a wire. The supported piece of the armature is rotatably supported by a support point, thereby a side surface of the cavity and a side surface of the supported piece, and a bottom surface of the cavity and an end surface of the supported piece can be set in the proximity. Accordingly, magnetic resistance between the magnetic circuit formation member and the yoke can be reduced.
Description




BACKGROUND OF THE INVENTION




1. Field of the Invention




The present invention relates to a wire dot printer head of wire dot printer, and more particularly, to a structure where magnetic resistance between an armature and a yoke is reduced.




2. Discussion of the Background




Conventionally, known is a wire dot printer head, in which a coil is attached to a core magnetically coupled to a yoke and an armature to drive a wire is provided capable of approaching/separating to/from the core. Printing is performed by driving the armature by feeding a current through the coil and colliding the wire against a print sheet by driving energy of the armature.




The requirement for armature performance is to reduce weight for high speed operation while have a function of forming a magnetic circuit to the yoke and the core and a function of driving the wire. This requirement for the armature is met by constructing the armature by coupling a magnetic circuit formation member for forming a magnetic circuit with respect to the yoke and the core to a light-weight and high-strength arm, and by coupling the wire to an end of the wire.




As usage of the armature comprised of the magnetic circuit formation member and the arm, if the portion of the magnetic circuit formation member is simply provided to be opposed to end surfaces of the core and the yoke, it is structurally difficult to increase opposing surface areas of the magnetic circuit formation member and the yoke. As a result, magnetic resistance between the magnetic circuit formation member and the yoke increases, and the speed of response operation of the armature when a current is fed through the coil is lowered.




Japanese Laid-Open Publication No. Hei 5-238019 discloses an armature constructed by coupling a magnetic material for formation of a magnetic circuit with respect to the yoke and arm to a light-weight and high-strength arm. In this Japanese Laid-Open Publication No. Hei 5-238019, a projecting coupling member having a half-round cross section is formed in a magnetic path portion of the armature, the coupling member is engaged in a recess-shaped rotation support member formed in a part of the yoke, and the armature is rotated about the rotation support member.




However, as apparent from Japanese Laid-Open Publication No. Hei 5-238019, the projecting coupling member formed in the magnetic path portion of the armature and the recess-shaped rotation support member formed in the yoke have mutually opposing surfaces in contact with each other. There is no idea of feeding a magnetic flux between an inner surface of the recess-shaped rotation support member and an outer surface of the coupling member of the armature.




SUMMARY OF THE INVENTION




Accordingly, an object of the present invention is to realize a light-weight and high-strength arm to drive the wire, and especially to reduce the magnetic resistance between the magnetic circuit formation member, coupled to the arm to construct the armature, and the yoke.




The object of the present invention is attained by a novel wire dot printer head of the present invention.




Thus, according to the novel wire dot printer head of the present invention, as an armature is formed by coupling a magnetic circuit formation member having a supported piece with its one end inserted into a cavity formed on the surface of the yoke to an arm coupled to a wire, and the supported piece of the armature is rotatably supported by a support member, and a gap between a side surface of the cavity and a side surface of the supported piece, and a gap between a bottom surface of the cavity and an end surface of the supported piece can be maintained in status of constant proximity. Accordingly, the magnetic resistance between the magnetic circuit formation member and the yoke can be reduced.











BRIEF DESCRIPTION OF THE DRAWINGS




A more complete appreciation of the present invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:





FIG. 1

is a central longitudinal cross-sectional front view of a wire dot printer head of the present invention;





FIG. 2

is a partial longitudinal cross-sectional side view along a line A—A in

FIG. 1

for explanation of armature support structure;





FIG. 3

is an exploded partially cut-away perspective view of a yoke and an armature spacer for explanation of the armature support structure;





FIG. 4

is a longitudinal cross-sectional side view of another armature; and





FIG. 5

is a partial longitudinal cross-sectional side view along the line A—A in

FIG. 1

for explanation of another armature support structure.











DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT




Obviously, numerous modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described herein.




An embodiment of the present invention will be described with reference to

FIGS. 1

to


3


.




First, the entire structure of a wire dot printer head


1


will be described with reference to FIG.


1


. The wire dot printer head


1


is formed by sequentially depositing a front case


2


, a circuit board


3


, a yoke


4


, an armature spacer


5


and a rear case


6


. The front case


2


and the rear case


6


are connected to each other by attachment screws (not shown), and the circuit board


3


, the yoke


4


and the armature spacer


5


are held between the front case


2


and the rear case


6


. The yoke


4


is made of magnetic material. The yoke


4


has an outer peripheral part


8


and an inner cylindrical part


9


, and plural cores


10


are integrally formed between the outer peripheral part


8


and the cylindrical part


9


. These cores


10


have a magnetic pole surface


11


at an end in an axial direction. A coil


12


is attached around an outer periphery of the cores


10


. Plural cavities


13


corresponding to the cores


10


are formed in the outer peripheral part


8


of the yoke


4


. An armature


14


opposed to the core


10


is comprised of an arm


16


to which a wire


15


is wax-bonded and a magnetic circuit formation member


17


welded to both side surfaces of the arm. These armatures


14


are rotatably supported by a support shaft


18


as a support point. The direction of the support shaft


18


is orthogonal to an axis of the core


10


. A wire guide


7


is provided with plural guide chips


19


to slidably guide the wire


15


, and an end guide


20


which arrays the ends of the wires to slidably guide the arrayed wires


15


is provided at an end of the front case


2


.




The armature


14


rotates about the support shaft


18


in a printing direction when a current is fed through the coil


12


. The armature


14


is biased in a returning direction by a biasing member (not shown) such that it is returnable in the returning direction about the support shaft


18


when the current fed through the coil


12


is cut. A ring shaped armature stopper


21


is provided at the center of the rear case


3


. The armature stopper


21


has a function to be contact with the arm


16


of the returning armature


14


to define a return position of the armature


14


.




Referring to

FIG. 3

, the particular shapes of the yoke


4


, the armature spacer


5


and the armature


14


will be described. The respective cores


10


are formed in the yoke


4


radially with respect to the center of the yoke


4


. The cavity


13


is provided on a phantom straight line connecting the center of the yoke


4


and the center of the magnetic pole surface


11


of the core


10


. The magnetic circuit formation member


17


of the armature


14


is made of magnetic material. The magnetic circuit formation member


17


has a supported piece


22


inserted into the cavity


13


formed in the yoke


4


and an attracted surface


23


attracted by the magnetic pole surface


11


of the core


10


. The support shaft


18


is removably engaged in a round through hole (not shown) formed in the supported piece


22


and the arm


16


. A through hole


24


is formed in parallel to the support shaft


18


in the arm


16


and the magnetic circuit formation member


17


provided on both side surfaces of the arm. The arm


16


and the magnetic circuit formation member


17


are coupled by inserting the support shaft


18


through a through hole (not shown), inserting a shaft (not shown) through the through hole


24


in parallel to the support shaft


18


, and in that status, welding the magnetic circuit formation member


17


provided on both side surfaces of the arm


16


. After the welding, the shaft is pulled out of the through hole


24


.




In the present embodiment, the support shaft


18


is in contact with the outer peripheral part


8


of the yoke


4


with its both end portions are on both sides of the cavity


13


. The armature spacer


5


is provided between the yoke


4


and the rear case


6


for formation of space to enable rising and falling operation of the armature


14


. Plural grooves


25


in which the respective support shafts


18


are engaged are formed in the armature spacer


5


. These grooves


25


define positions of the respective support shafts


18


which are in contact on the yoke


4


in an axial direction and positions in a direction orthogonal to the axial direction. Plural guide grooves


26


in which the respective armatures


14


are inserted are formed in the armature spacer


5


.




As apparent from

FIGS. 1 and 3

, a bottom surface of the cavity


13


and an end surface of the supported piece


22


opposed to the bottom surface with a slight gap therebetween are formed to have an arc shape along a radius of the support shaft


18


.




In the present embodiment, the armature spacer


5


is formed by forging or the like using a silicon steel plate as a squeeze-processable low-price magnetic material for enabling flow of magnetic flux between the both side surfaces of the magnetic circuit formation member


17


of the armature


14


and the spacer. The yoke


4


, the core


10


and the magnetic circuit formation member


17


of the armature


14


are formed by metal injection or the like using Permendur as a ferromagnetic material. The arm


16


of the armature


14


is formed by pressing using high-strength marageing steel or light-weight titanium alloy for wax-bonding to the wire


15


. The support shaft


18


is made of e.g. SUS for improvement in abrasion resistance and holding a round shape.




As the structure of wire dot printer using the wire dot printer head


1


is already known, the basic structure will be briefly described without drawing. The wire dot printer has the wire dot printer head


1


, a carriage holding the wire dot printer head


1


, scanned in a straight liner direction, a platen arranged along the scanning direction of the carriage, and a conveyance roller which conveys a print sheet to a position between the platen and the wire dot printer head


1


.




The operation of the wire dot printer will be described. The wire dot printer head


1


is scanned by the carriage along the platen. The coil


12


selected in correspondence with print data is energized by current upon carriage scanning. As the current is fed through the coil


12


, a magnetic flux flows through the core


10


, the magnetic circuit formation member


17


of the armature


14


, the yoke


4


and the core


10


in this order. Accordingly, the armature


14


corresponding to the coil


12


rotates about the support shaft


18


toward a direction in which the attracted surface


23


of the magnetic circuit formation member


17


is attracted by the magnetic pole surface


11


of the core


10


. The wire


15


is driven in the printing direction by rotation operation of the armature


14


.

FIG. 1

shows a moment at which the end of the wires


15


are driven to the print sheet side. The energization to the coil


12


is made instantaneously. When the current fed through the coil


12


is cut, the armature


14


rotates in the returning direction about the support shaft


18


. The energy to cause the armature


14


to return in the returning direction is caused by, as described above, the biasing force of the biasing member to bias the armature


14


in the returning direction and repulsion applied to the wire


15


from the platen by impact between the platen and the wire


15


.




As the supported piece


22


of the magnetic circuit formation member


17


constructing the armature


14


is inserted into the cavity


13


formed in the yoke


4


, an outer side surface of the supported piece


22


opposite to the arm


16


and the inner side surface of the cavity


13


are set in the proximity and a magnetic flux can be fed therebetween. As the magnetic flux is fed between the outer side surface of the supported piece


22


and the inner side surface of the cavity


13


, the magnetic resistance between the yoke


4


and the magnetic circuit formation member


17


of the armature


14


can be reduced.




As the armature spacer


5


allows flow of magnetic flux between the spacer and the both sides of the magnetic circuit formation member


17


of the armature


14


, the magnetic resistance between the yoke


4


and the magnetic circuit formation member


17


of the armature


14


can be reduced.




As the bottom surface of the cavity


13


is formed in arc shape along the radius of the support shaft


18


, a gap between the bottom surface of the armature


14


and one end of the supported piece


22


is kept constant regardless of positional change of the armature


14


in the rotation direction. As the one end of the supported piece


22


is formed into arc shape along the radius of the support shaft


18


, a gap between the end of the supported piece


22


and the bottom surface of the cavity


13


is uniformly kept in the entire area of the end of the supported piece


22


.




As the arm


16


is provided on a phantom straight line connecting the center of the yoke


4


and the center of the magnetic pole surface


11


of the core


10


, and the arm


16


is held by the plural magnetic circuit formation members


17


symmetrically provided on the both side surfaces of the arm, the balance of the armature


14


can be easily achieved.




As the material of the arm


16


, any of magnetic material, weak magnetic material and non-magnetic material may be used. If the arm


16


is made of weak magnetic material or non-magnetic material, as a magnetic flux does not flow through the arm


16


easily, magnetic efficiency is lowered. Further, if a high-strength and lightweight material such as titanium alloy is selected as the material of the arm


16


, the arm


16


and the wire


15


can be firmly wax-bonded to each other, and inertial moment of the armature


14


can be reduced.




Another embodiment of the present invention will be described with reference to

FIGS. 4 and 5

. The cross-sectional positions of

FIGS. 4 and 5

are along the A—A line in FIG.


1


.




As an armature


14


A in the present embodiment is basically the same as the armature


14


described in the above-described embodiment, only the difference will be described. An arm


16


A in the present embodiment has a length not to allow one end of the support shaft


18


to reach the end of the supported piece


22


. More particularly, the arm


16


A is short such that a half-round notch is formed for passing the support shaft


18


. As shown in

FIG. 4

, a gap


27


corresponding to a plate thickness of the arm


16


A is formed between the supported pieces


22


of the magnetic circuit formation member


17


. As shown in

FIG. 5

, a projection piece


28


projecting in the gap


27


between the supported pieces


22


is integrally formed at the center of the cavity


13


of the yoke


4


.




Accordingly, as in the case of the above-described embodiment, an outer side surface of the supported piece


22


opposite to the arm


16


A and the inner side surface of the cavity


13


are set in the proximity and a magnetic flux can be fed therebetween, and an inner side surface of the supported piece


22


and an outer side surface of the projection piece


28


are set in the proximity and a magnetic flux can also be fed therebetween. In this manner, as the projection piece


28


projecting in the gap


27


between the supported pieces


22


is formed at the center of the cavity


13


of the yoke


4


, opposing surface areas of the supported piece


22


and the yoke


4


can be increased, and the magnetic resistance between the yoke


4


and the magnetic circuit formation member


17


of the armature


14


can be effectively reduced.




In this manner, the spillover effect from the construction where the projection piece


28


projecting in the gap


27


between the supported pieces


22


is that, since the length of the arm


16


A on the side of the end of the supported piece


22


is shortened, contact area of the arm


16


A and the support shaft


18


is reduced, and abrasion of the arm


16


A due to contact between the arm


16


A and the support shaft


18


can be suppressed.




Also in the present embodiment, as the bottom surface of the cavity


13


has an arc shape along a radius of the support shaft


18


, a gap between the bottom surface of the armature


14


and the one end of the supported piece


22


is kept constant regardless of positional change of the armature


14


in the rotation direction. As the one end of the supported piece


22


is formed into arc shape along the radius of the support shaft


18


, the gap between the end of the supported piece


22


and the bottom surface of the cavity


13


is uniformly kept in the entire area of the end of the supported piece


22


.



Claims
  • 1. A supporting structure of an armature of a wire dot printer head, comprising:a yoke made of magnetic material; a core made of magnetic material, with a magnetic pole surface at one end and magnetically coupled to the yoke; a coil attached to the core; a cavity formed in a position in proximity to the core on a surface of the yoke; an armature formed by coupling a magnetic circuit formation member made of magnetic material having a supported piece with one end inserted into the cavity and an attracted surface attracted to the magnetic pole surface of the core, to an arm coupled to a rear end of a wire to strike a print sheet at an end; a support point that rotatably supports the supported piece, an axis of the supported piece is orthogonal to an axis of the core; and an armature spacer made of magnetic material that allows a flow of magnetic flux between both sides of the magnetic circuit formation member, wherein a part of the armature spacer is provided in contact with the yoke, wherein the support point includes a support shaft of magnetic material in contact with the yoke, and wherein a groove that defines a position of the support shaft is formed in the armature spacer.
  • 2. The supporting structure according to claim 1, wherein the support point is provided outside of the cavity.
  • 3. A supporting structure of an armature of a wire dot printer head, comprising:a yoke made of magnetic material; a core made of magnetic material, with a magnetic pole surface at one end and magnetically coupled to the yoke; a coil attached to the core; a cavity formed in a position in proximity to the core on a surface of the yoke; an armature formed by coupling a pair of magnetic circuit formation members made of magnetic material each having a supported piece with one end inserted into the cavity and an attracted surface attracted to the magnetic pole surface of the core, to an arm coupled to a rear end of a wire to strike a print sheet at an end; a support point that rotatable supports each of the supported pieces, an axis of each of the supported pieces being orthogonal to an axis of the core; wherein the supported pieces of the pair of magnetic circuit formation members are provided on both sides of the arm, and wherein a projection piece made of magnetic material that projects between the supported pieces of the magnetic circuit formation members provided on both sides of the arm is formed at a center of the cavity.
  • 4. The supporting structure according to claim 3, wherein the support point is provided outside of the cavity.
US Referenced Citations (12)
Number Name Date Kind
4109776 Ek et al. Aug 1978 A
4136978 Bellinger, Jr. et al. Jan 1979 A
4433926 Isobe et al. Feb 1984 A
4575268 Yang et al. Mar 1986 A
4634302 West et al. Jan 1987 A
4767226 Sakaida et al. Aug 1988 A
4915524 Mitsuishi et al. Apr 1990 A
4986676 Kimura et al. Jan 1991 A
5056942 Norigoe Oct 1991 A
5236266 Mitsuishi et al. Aug 1993 A
5290112 Stempfle et al. Mar 1994 A
5527118 Asada et al. Jun 1996 A
Foreign Referenced Citations (4)
Number Date Country
0431876 Jun 1991 EP
5-238019 Sep 1993 JP
05238019 Sep 1993 JP
2001-30523 Feb 2001 JP
Non-Patent Literature Citations (2)
Entry
U.S. application Ser. No. 10/098,555, Terao et al., filed Mar. 18, 2002.
U.S. application Ser. No. 10/376,268, Terao, filed Mar. 3, 2003.