JP2699314B2 - Wire dot print head - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wire dot print head having a sensor for observing the movement of an armature and driving the armature by a sensor output from the sensor.

[0002]

2. Description of the Related Art Conventionally, an impact printer which drives a printing wire, hits a printing medium via an ink ribbon, and prints with the hitting force has a high degree of freedom of printing medium and is relatively inexpensive. And output devices such as information processing systems.

The above impact printers are classified into a plunger type, a spring charge type and a clapper type according to the type of the wire dot print head. Among them, the spring-charged type has an armature to which a printing wire is fixed is swingably supported by a biasing leaf spring, and the armature is previously attracted to the core by a permanent magnet against the elastic force of the leaf spring. When printing, the coil wound around the core is excited to generate a magnetic flux in the opposite direction to the permanent magnet, and the armature is released. The spring-charged wire dot print head, which has good high-speed response, is often used.

Further, there has been provided an image sensor in which a sensor is provided inside, the displacement of the armature is observed by the sensor, and the driving time of the coil is controlled in accordance with the sensor output to improve the print quality. FIG. 2 is a sectional view of a conventional spring charge type wire dot print head. In the figure, 1
Is a base, a permanent magnet 2, a base plate 3, and a spacer 4 are sequentially stacked on an end of the base 1, and a leaf spring 7 and a yoke 8 are interposed between the spacer 4 and the guide frame 5 via a clamp 6. It is supported in a portable manner.

[0005] Reference numeral 9 denotes a core provided on the base 1, and 10 denotes a coil wound around the outer periphery of the core 9. The core 9 and the coil 10 form an electromagnet 11. Reference numeral 12 denotes a cover, which protects a current-carrying board 13 for wiring the coil 10. An armature 14 is attached to the flexible portion of the leaf spring 7 adjacent to the yoke 8, and a print wire 15 is attached to a tip of the armature 14 facing the core 9 of the electromagnet 11, and is fixed to the guide frame 5. The wire guide 16 is guided to a platen (not shown).

In the above-described wire dot print head, when the coil 10 is not energized, the leaf spring 7 supporting the armature 14 to which the print wire 15 is attached is attracted to the core 9 by the magnetic flux of the permanent magnet 2. The printing wire 15 is placed so as not to protrude from the wire guide 16. In this state, the coil 10
When the magnetic flux is generated in such a direction as to cancel the magnetic flux of the permanent magnet 2, the biased leaf spring 7 is released, and the printing wire 15 projects from the end face of the wire guide 16 by the elastic force of the leaf spring 7. . The printing wire 15 protruding in this way performs printing by strongly pressing the ink ribbon and the printing medium placed opposite to the wire dot print head against the platen.

[0007] If the flight time of each print wire 15 varies, or if the contact time with the ink ribbon or print medium varies, the print wires 15 may not be printed.
The return time of the armature 14 and the leaf spring 7 may strongly collide with the core 9, or the printing wire 15 may not return forever, which may cause a printing failure.

Therefore, the displacement of each armature 14 is observed to generate a different drive signal for each print wire 15, and a means for observing the displacement of the armature 14 is provided inside the wire dot print head. .
Reference numeral 17 denotes a detection board provided between the guide frame 5 and the yoke 8, and reference numeral 18 denotes a fixed pole provided on the detection board 17. The fixed pole 18 forms a capacitor by opposing each armature 14 in a narrow space, and has a predetermined capacitance.

The value of the capacitance is determined according to the space between the fixed pole 18 and the armature 14, and the capacitance changes when the armature 14 is displaced during the printing operation. Thus, by detecting this change, the operation of the printing wire 15 fixed to the armature 14 can be known by the detection control element 19 provided on the detection board 17. by the way,
If high-speed printing is to be performed using the wire dot print head having the above-described configuration, the armature 14 may cause an overstroke after printing with the print wire 15 protruding from the end surface of the wire guide 16.

FIG. 3 is a sectional view of another conventional wire dot print head, FIG. 4 is an explanatory view of the operation of the conventional wire dot print head, and FIG. 5 is an enlarged view of a main part of the conventional wire dot print head. 4A shows a state at the time of printing, FIG. 4B shows a state at the time of suction, and FIG. 4C shows a state at the time of occurrence of an overstroke. In FIG. 4, when the printing is completed and the armature 14 is attracted to the core 9 again by the magnetic flux of the permanent magnet 2 as shown in (b), the armature 14 is rotated as it is by the moment of inertia, as shown in (c). An overstroke occurs, the rear end 14a of the armature 14 projects above the yoke 8, and the leaf spring 7 is excessively bent.

Therefore, as shown in FIGS. 3 and 5, after the printing is completed and the armature 14 is sucked into the core 9, an overstroke is generated to prevent the leaf spring 7 from being damaged. A stopper plate 23 is provided between the substrate 17 and the yoke 8 so as to face the rear end 14a of the armature 14. By doing so, the rear end 14a of the armature 14 abuts against the stopper plate 23 immediately before the occurrence of the overstroke, thereby preventing the occurrence of the overstroke and preventing the leaf spring 7 fixing the armature 14 from being damaged. Can be prevented.

In order to prevent the rear end 14a of the armature 14 from abutting on the stopper plate 23 during static suction, a clearance 31 (FIG. 5) is provided between the position of the rear end 14a of the armature 14 during static suction and the stopper plate 23. )
Is formed. In FIG. 3, TH is a thermistor for detecting the temperature in the wire dot print head.

[0013]

However, in the above-described conventional wire dot print head, the thickness t _{1 of the} yoke 8 is set to form the clearance 31, and the armature 14 and the detection substrate 17 The average distance δ ₁ between the fixed poles 18 is determined structurally and cannot be shorter than a certain amount.

Therefore, the armature 14 and the fixed pole 1
It becomes difficult to detect the change in the capacitance between the eight and observe the displacement of the armature 14. Next, setting of driving conditions in a conventional wire dot print head will be described with reference to FIG. FIG. 6 is a time chart for a conventional wire dot print head.

In the figure, the sensor output indicates a change in capacitance, and the armature 14 is displaced and the fixed pole 18 is moved.
It gets bigger as it gets closer. However, the capacitance is an average distance δ ₁ between the armature 14 and the fixed pole 18.
To inversely, it is impossible to increase the maximum value V ₁ of the sensor output as a change in capacitance, susceptible to noise. Further, when the slice level is multiplied by the sensor output, the driving condition of the coil 10 cannot be set to an optimum state.

When the length L ₁ (FIG. 5) of the armature 14 is shortened, the stroke is reduced, so that the plate thickness t _{1 of the} yoke 8 can be reduced, and the average distance δ ₁ between the armature 14 and the fixed pole 18 is reduced. Although it can be shortened, the balance of the mass of the armature 14 is lost, high-order vibration is generated at the time of suction after printing is completed, and the suction operation is delayed.

The present invention solves the above-mentioned problems of the conventional wire dot print head, and can increase the sensor output without affecting the displacement of the armature, and is not affected by noise. It is an object to provide a print head.

[0018]

For this purpose, in a wire dot print head according to the present invention, an armature having a print wire fixed to the tip and supported swingably by a leaf spring, facing one surface of the armature. And a coil that is wound around the core, generates a magnetic flux from the core when energized, and displaces the armature.

[0019] The printhead further includes a fixed pole fixed to the print head body and opposed to the other surface of the armature, and a capacitance sensor formed by a combination of the armature and the fixed pole. In the armature, the other surface facing the fixed pole is cut away from the rear end of the armature forward by a predetermined amount.

In another wire dot print head according to the present invention, an armature having a print wire fixed to the tip and supported swingably by a leaf spring, and a core disposed opposite to one surface of the armature. And a coil that is wound around the core, generates a magnetic flux from the core when energized, and displaces the armature.

A detection board fixed to the print head body, a fixed pole disposed on the detection board so as to face the other surface of the armature, and a combination of the armature and the fixed pole; And a capacitance sensor. In addition, a relief hole for accommodating the rear end of the armature is formed in a portion corresponding to the rear end of the armature on the detection substrate.

[0022]

According to the present invention, as described above, in the wire dot print head, the print wire is fixed to the tip, and the armature is swingably supported by the leaf spring, and is opposed to one surface of the armature. A core is provided, and a coil is wound around the core and generates a magnetic flux from the core when energized to displace the armature.

[0023] Further, it has a fixed pole fixed to the print head main body and disposed opposite to the other surface of the armature, and a capacitance sensor constituted by a combination of the armature and the fixed pole. In the armature, the other surface facing the fixed pole is cut away from the rear end of the armature forward by a predetermined amount. In this case, even if the rear end of the armature is lifted by the suction of the core, the rear end is not cut and does not hit the detection substrate. Therefore, the armature can be brought closer to the fixed pole side by the cutout.

In another wire dot print head according to the present invention, an armature having a print wire fixed to a tip thereof and supported swingably by a leaf spring, and a core disposed opposite to one surface of the armature. And a coil that is wound around the core, generates a magnetic flux from the core when energized, and displaces the armature.

A detection substrate fixed to the print head main body, a fixed pole disposed on the detection substrate so as to face the other surface of the armature, and a combination of the armature and the fixed pole And a capacitance sensor. In addition, a relief hole for accommodating the rear end of the armature is formed in a portion corresponding to the rear end of the armature on the detection substrate. In this case, even if the rear end of the armature is lifted by the suction by the core, the rear end is accommodated in the relief hole. Therefore, the armature can be brought closer to the fixed pole side.

[0026]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a cross-sectional view of a wire dot print head showing a first embodiment of the present invention, FIG. 7 is an enlarged view of a main part of the wire dot print head showing a first embodiment of the present invention, and FIG. 4 is a time chart in the wire dot print head showing the first embodiment.

In the drawing, reference numeral 1 denotes a base, and a permanent magnet 2, a base plate 3, and a spacer 4 are sequentially stacked on the end of the base 1, and a plate 6 is provided between the spacer 4 and the guide frame 5 via a clamp 6. A spring 7 and a yoke 8 are supported in a cantilever manner. 9 is a core provided on the base 1, 10
Is a coil wound around the outer periphery of the core 9, and the core 9 and the coil 10 form an electromagnet 11. Reference numeral 12 denotes a cover, which protects a current-carrying board 13 for wiring the coil 10. An armature 14 is attached to the flexible portion of the leaf spring 7 adjacent to the yoke 8, and a print wire 15 is attached to a tip of the armature 14 facing the core 9 of the electromagnet 11, and is fixed to the guide frame 5. The wire guide 16 is guided to a platen (not shown). TH is a thermistor for detecting the temperature inside the wire dot print head.

In the wire dot print head having the above configuration, when the coil 10 is not energized, the leaf spring 7 supporting the armature 14 to which the print wire 15 is attached is attracted to the core 9 by the magnetic flux of the permanent magnet 2. The printing wire 15 is placed so as not to protrude from the wire guide 16. In this state, the coil 10
When the magnetic flux is generated in such a direction as to cancel the magnetic flux of the permanent magnet 2, the biased leaf spring 7 is released, and the printing wire 15 projects from the end face of the wire guide 16 by the elastic force of the leaf spring 7. . Then, the protruding printing wire 15 performs printing by strongly pressing the ink ribbon and the printing medium placed opposite to the wire dot print head against the platen.

By the way, if the flight time of each print wire 15 varies, or if the contact time with the ink ribbon or print medium varies, the print wires 15 will not change.
The return time of the armature 14 and the leaf spring 7 may strongly collide with the core 9, or the printing wire 15 may not return forever, which may cause a printing failure.

Therefore, the displacement of each armature 14 is observed to generate a different drive signal for each print wire 15, and a means for observing the displacement of the armature 14 is provided inside the wire dot print head. .
Reference numeral 17 denotes a detection board provided between the guide frame 5 and the stopper plate 23, and reference numeral 18 denotes a fixed pole provided on the detection board 17. The fixed pole 18 forms a capacitor by opposing each armature 14 in a narrow space, and has a predetermined capacitance.

The value of the capacitance is determined according to the space between the fixed pole 18 and the armature 14, and the capacitance changes when the armature 14 is displaced during the printing operation. Thus, by detecting this change, the operation of the printing wire 15 fixed to the armature 14 can be known by the detection control element 19 provided on the detection board 17. FIG.
And a rear end 14c of the armature 14 as shown in FIG.
The surface facing the stopper plate 23 on the side is cut out to the vicinity of the rotation center O of the leaf spring 7 to form a stepped portion 14b, thereby lowering the position of the rear end 14c of the armature 14 during suction. . Therefore, the thickness of the yoke 8 can be reduced from t ₁ to t ₂ as compared with the case where the conventional armature 14 shown by the one-dot chain line in the drawing is used.

Therefore, the detection substrate 17 can be brought closer to the armature 14 by that much, so that the average distance between the armature 14 and the fixed pole 18 on the detection substrate 17 is δ _1.
To δ ₂ . Since the capacitance between the armature 14 and the fixed pole 18 is inversely proportional to the average distance between them, the capacitance is increased by a factor of δ ₁ / δ ₂ by reducing the average distance from δ ₁ to δ _2. It will be. Then, the maximum value of the sensor output due to the displacement of the armature 14 (displacement power, or speed output) increases from V ₁ to V _2, the _{V 2 = V 1 × δ 1} / δ 2.

As a result, the ratio of the noise component added to the sensor output, that is, the S / N ratio is reduced, and the slice level added to the sensor output for driving the electromagnet 11 is changed from slice level 1 to slice level 2.
, And becomes less susceptible to noise. Since the step 14b of the armature 14 is substantially small, the operation of the armature 14 does not lose its balance during suction.

FIG. 9 is an enlarged view of a main part of a wire dot print head showing a second embodiment of the present invention, and FIG. 10 is a second embodiment of the present invention.
FIG. 2 is an exploded perspective view of a wire dot print head showing the embodiment of FIG. In the figure, reference numeral 24 denotes an insulating layer formed on the surface of the detection substrate 17 on the yoke 8 side. When the stopper plate 23 (FIG. 1) for preventing overstroke is not used, a relief hole 17a is formed in a portion of the detection board 17 corresponding to the rear end 14a of the armature 14. The escape hole 17a
The armatures 1 are arranged so that the armatures 14 do not come into contact with the detection substrate 17 when the cores 9 are sucked.
The number corresponding to 4 is provided. Therefore, the yoke 8
Can be reduced from t ₁ to t ₃ at which the attraction force of the armature 14 does not decrease, and the average distance between the armature 14 and the fixed pole 18 (FIG. 1) on the detection board 17 can be reduced, The output can be increased.

The present invention is not limited to the above embodiment, but can be variously modified based on the gist of the present invention, and these are not excluded from the scope of the present invention.

[0036]

As described above in detail, according to the present invention, in the wire dot print head, an armature having a print wire fixed to the tip and supported swingably by a leaf spring, and one of the armatures And a coil that is wound around the core, generates a magnetic flux from the core by energization, and displaces the armature. A fixed pole fixed to the print head main body and arranged opposite to the other surface of the armature; and a capacitance sensor formed by a combination of the armature and the fixed pole. In the armature, the other surface facing the fixed pole is cut away from the rear end of the armature forward by a predetermined amount.

In this case, even if the rear end of the armature is lifted by the suction by the core, the rear end is cut off and does not hit the detection substrate. Therefore, the armature can be brought closer to the fixed pole side by an amount corresponding to the cutout, so that the capacitance between the two can be increased. As a result, not only can the sensor output be increased without affecting the displacement of the armature, but also the sensor output is not affected by noise.

In another wire dot print head according to the present invention, an armature having a print wire fixed to the tip and supported swingably by a leaf spring, and a core disposed opposite to one surface of the armature. And a coil that is wound around the core, generates a magnetic flux from the core when energized, and displaces the armature. Then, a detection substrate fixed to the print head main body, a fixed pole disposed on the detection substrate so as to face the other surface of the armature, and a combination of the armature and the fixed pole is provided. A capacitance sensor. In addition, a relief hole for accommodating the rear end of the armature is formed in a portion corresponding to the rear end of the armature on the detection substrate.

In this case, even if the rear end of the armature is raised by being sucked by the core, the rear end is accommodated in the escape hole.
Therefore, the armature can be brought closer to the fixed pole side by that amount, so that the capacitance between them can be increased. As a result, not only can the sensor output be increased without affecting the displacement of the armature, but also the sensor output is not affected by noise. Further, since the sensor output is stabilized, the drive time of the coil can be controlled well, and the print quality can be improved.

[Brief description of the drawings]

FIG. 1 is a sectional view of a wire dot print head showing a first embodiment of the present invention.

FIG. 2 is a sectional view of a conventional spring charge type wire dot print head.

FIG. 3 is a sectional view of another conventional wire dot print head.

FIG. 4 is a diagram illustrating the operation of a conventional wire dot print head.

FIG. 5 is an enlarged view of a main part of a conventional wire dot print head.

FIG. 6 is a time chart in a conventional wire dot print head.

FIG. 7 is an enlarged view of a main part of the wire dot print head showing the first embodiment of the present invention.

FIG. 8 is a time chart in the wire dot print head showing the first embodiment of the present invention.

FIG. 9 is an enlarged view of a main part of a wire dot print head showing a second embodiment of the present invention.

FIG. 10 is an exploded perspective view of a wire dot print head showing a second embodiment of the present invention.

[Explanation of symbols]

 2 permanent magnet 7 leaf spring 9 core 10 coil 14 armature 14b step 14c rear end 15 printing wire 17 detection board 17a relief hole 18 fixed pole 19 detection control element

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Noboru Oishi 1-7-12 Toranomon, Minato-ku, Tokyo Oki Electric Industry Co., Ltd. (56) References JP-A-64-53860 (JP, A) Hei 1-64449 (JP, U)

Claims (4)

(57) [Claims] 1. A printing wire is fixed to a tip, and is attached to a leaf spring.
Therefore swingably supported Amachu A, one face facing the allowed and disposed core of the armature, and is wound around the co <br/> A, to generate a magnetic flux from the core by energization,
In the wire dot printing head Ru with a coil for displacing the armature, (a) is disposed to face the other side of the armature, fixing the fixed pole which is fixed to the print head body, and (b) the armature Depending on the combination with poles
And having a static Den'yo Ryose capacitors to be made, (c) the armature and the other opposed to the fixed pole
Surface thereof, a wire dot printing head, characterized in that notched set amount toward the front from the rear end of the armature. 2. A printing wire is fixed to a tip, and is attached to a leaf spring.
Therefore swingably supported Amachu A, one face facing the allowed and disposed core of the armature, and is wound around the co <br/> A, to generate a magnetic flux from the core by energization,
In the wire dot printing head Ru with a coil for displacing the armature, and the detection board fixed to (a) print head body, on a substrate the detectable (b), the other of the armature
Structure of the surface and the opposite is allowed to disposed a fixed electrode, by a combination of (c) above the armature and the fixed pole
And having a static Den'yo Ryose capacitors to be made, (d) to the detection substrate, the portion corresponding to the rear end of the armature, escape hole for accommodating the rear end of the armature
Wire dot printing head, characterized in that There are formed. Wherein (a) is generated a magnetic flux, and has a permanent magnet you sucking the armature core against the elastic force of the plate spring, (b) the coil is the magnetic flux of the permanent magnet by energization to generate a magnetic flux in a direction to cancel the, release the armature
Wire dot printing head according to claim 1 or 2. 4. The coil generates a magnetic flux when energized.
Is allowed, the wire dot printing head according to claim 1 or 2 for sucking the armature.