JPH06286169A - Impact dot head - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide an impact dot head having high energy conversion efficiency, long life and high reliability. [Structure] A spring 27 is arranged outside the magnetic circuit, and a material having a lower saturation magnetic flux density and permeability than the constituent material of the magnetic circuit is used as the material of the spring 27. [Effect] The magnetic circuit portion and the mechanical spring member are functionally separated, which enables a highly flexible design in pursuit of the performance of each of the magnetic circuit portion and the mechanical spring member, and the spring 27
It also prevents stress corrosion cracking.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a print head for an impact dot matrix printer.

[0002]

2. Description of the Related Art There has been an increasing demand for a low-priced serial printer capable of various printing as an output terminal of a personal computer which has rapidly spread in recent years. Among them, serial impact dot printers are widely used for business such as issuing slips and outputting program lists because of their low running cost and wide selection range of printing media. Among the impact dot heads used in this serial impact dot printer, those that require high-speed printing, store strain energy by biasing the spring member by the magnetic flux of the permanent magnet during standby, and selectively store it in the electromagnetic coil. A large number of so-called spring-charge types have been developed and put into practical use, in which the strain energy of the spring member is converted into kinetic energy by canceling the magnetic flux of the permanent magnet by energization to perform a printing operation. For example, an impact dot head as disclosed in Japanese Patent Publication No. 62-4237 is known. The contents will be described with reference to FIG.

FIG. 5 is a partial sectional view of one printing unit of an impact dot head disclosed in Japanese Patent Publication No. 62-4237. The right side of FIG. 5 is the center side of the impact dot head and the left side is the outer peripheral side. Each corresponds. A ring-shaped permanent magnet 124 and a ring-shaped spacer 132 are placed on the outer peripheral side of the upper surface of the disk-shaped base plate 136, and the same number of cores 125 as the number of printing elements are erected on the inner peripheral side. The coil 122 is wound.
A spring member 127, which is connected in a ring shape on the outer peripheral side and extends from the outer peripheral side toward the center, is placed on the spacer 132, and each inner peripheral side of the spring member 127 extends so as to cover the upper surface of each core 125. There is. Further, a lid 137 having a hole at the center is placed on the spring member 127 via a spring retainer 133, and the whole is fastened by a screw 138. A lever 126 is fixed to the upper surface of the spring member 127 by welding, and a printing protrusion 128, which is a printing element, is provided at the inner peripheral end of the lever 126. Base plate 13
6, the core 125 and the spacer 132 are made of a magnetically permeable material such as magnetic steel, and the spring member 127 is made of a magnetically permeable elastic material. Since the ring-shaped permanent magnet 124 is magnetized in the axial direction, the base plate 136, the core 1
A magnetic circuit is formed by 25, the spring member 127, and the spacer 132, and during standby, the magnetic flux of the permanent magnet 124 passes through the base plate 136, the core 125, the spring member 127, and the spacer 132, and loops back to the permanent magnet 124. Due to the magnetic flux of the permanent magnet 124, the spring member 1
Since 27 is attracted to the core 125, it is biased and stores strain energy. When the coil 122 is energized in a direction to generate a magnetic flux in a direction opposite to the magnetic flux of the permanent magnet 124, the magnetic flux of the permanent magnet 124 is canceled and the spring member 127 causes the core 12 to move.
5 is released from suction, the strain energy is released and the state returns to the free state. Accordingly, the lever 126 pivots upward in FIG. 5, and the printing protrusion 128 provided at the tip of the lever 126 is covered. Impact printing is performed on a print medium (not shown) by projecting from the central hole 137. When the printing is completed, the energization of the coil 122 is completed, and the magnetic flux of the permanent magnet 124 causes the spring member 127 to move to the core 1 again.
It is sucked by 22 and returns to the standby state.

[0004]

[Problems to be Solved by the Invention] Japanese Patent Publication No. 62-4237
In the impact dot head disclosed in the publication, the spring member 127 has both the function of a spring as a mechanical element and the function of a part of a magnetic circuit. However, it is very difficult to combine the function of this spring and the function as a part of the magnetic circuit at a practical level.

Here, in order to explain the spring function of the spring member 127, it is modeled as a cantilever and will be described with reference to FIG. In FIG. 6, the origin 0 is the spacer 1 of the spring member 127.
Corresponding to the edge part sandwiched between 32 and the spring retainer 133,
As the elastically deformable effective spring portion of the spring member 127, the range of the length l from this edge portion to the rear end of the attachment of the lever 126 is considered. Further, the range of the length a from the position where the suction force from the core 125 is received to the rear end of the mounting of the lever 126 is considered as a rigid body portion which is not elastically deformed because the bending rigidity of the lever 126 is large. With such a modeling, the deflection equation of the effective spring portion when receiving the suction force P by the core 125 is as follows.

[0006]

[Equation 1]

Where x is the distance in the longitudinal direction of the spring member,
y: distance in the direction of biasing the spring member, E: Young's modulus, I: second moment of area of the spring member, and when the spring constant is k, the following is obtained.

[0008]

[Equation 2]

When the cross section of the spring member 127 is a rectangle having a width b and a thickness h as shown in FIG. 7, the spring constant k is expressed as follows.

[0010]

[Equation 3]

The maximum stress σmax occurs at the edge portion of x = 0 and is expressed as follows.

[0012]

[Equation 4]

The attracting force P is determined by the amount of magnetic flux passing through the attracting portion, and all of this magnetic flux passes through the spring member 127, so the amount of magnetic flux has the cross-sectional area S of the spring member 127 as a function element. Further, since the cross-sectional area S = bxh, the suction force P is also influenced by the width b and thickness h of the spring, and the spring characteristics and the magnetic characteristics are entangled with each other, making it difficult to design both characteristics.

Also, in terms of material, there is no material excellent in both spring characteristics and magnetic characteristics. For example, spring steel having excellent spring characteristics has a low saturation magnetic flux density and magnetic permeability, and conversely, a saturated magnetic flux density and magnetic permeability. However, pure iron or silicon steel, which is a magnetic circuit material capable of increasing the energy conversion efficiency due to its high temperature, has low mechanical strength and is not practical as a spring material.

Further, the impact dot head is usually 1K.
Since it is driven at a high frequency of Hz or higher, the magnetic flux also increases / decreases at a high frequency, and an eddy current is thereby generated in the magnetic circuit. With this current, the corrosion conditions of the magnetic circuit are aligned,
Moreover, the loss due to the eddy current causes the spring member 127 itself to generate heat, and the temperature rises, further promoting the corrosion condition which is an electrochemical change. Since the spring member 127 vibrates at high frequency as it is driven, and the edge portion is in the maximum stress state as described above, the edge portion receives both stress and corrosion, and stress corrosion cracking occurs here. For this reason,
There is a problem that the spring member 127 is broken at the edge portion and has a short life and low reliability.

Therefore, an object of the present invention is to solve the above-mentioned conventional problems and to provide an impact dot head having a high energy conversion efficiency, a long life, and a high reliability.

[0017]

In order to solve the above problems, the impact dot head of the present invention stores strain energy by biasing the spring member by the magnetic flux of the permanent magnet during standby, and stores it in the electromagnetic coil. In an impact dot head that performs printing by converting the strain energy of the spring member into kinetic energy by canceling the magnetic flux of the permanent magnet by selectively energizing, in the printing operation, the magnetic pole of one of the permanent magnets passes through the electromagnetic coil and the other magnetic pole of the permanent magnet. The spring member is arranged outside the closed magnetic circuit up to the surface, and a material having a lower saturation magnetic flux density and magnetic permeability than the constituent material of the closed magnetic circuit is used as the material of the spring member.

[0018]

According to the above construction of the present invention, a material having a high mechanical strength can be used as the material of the spring member, and all the magnetic circuit parts can be made of materials having excellent magnetic characteristics.

[0019]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic plan view of a mechanical portion of a serial impact dot printer equipped with an impact dot head of the present invention, and FIG. 2 is a schematic front view. In this serial impact dot printer, the impact dot head 2 is mounted on the carriage 1 in order to perform the printing while moving the impact dot head 2 in the digit direction parallel to the platen 3 supporting the printing paper 5 as the printing medium. . Dots are printed on the printing paper 5 arranged between the platen 3 and the ink ribbon 4 while moving the carriage 1 in the digit direction, and desired characters, figures, etc. are printed. As the printing paper 5, various papers are used, from a single-cut paper made up of only one paper to a copy paper made up of about seven non-carbon papers.

The photocoupler 9 provided on the bottom plate 7 has a function of detecting the home position of the carriage 1 by detecting the presence of the fins 10 provided below the carriage 1. The carriage 1 is driven by a carriage driving motor 11 via a driving belt 12 as shown in FIG.
It is reciprocally driven in the lateral direction of FIG. At this time, the encoder 13 attached to the carriage drive motor 11 generates a signal for detecting the position of the carriage 1, and a reference print timing signal is generated based on this signal.

An embodiment of the impact dot head of the present invention will be described with reference to FIG. 3 which is a sectional view taken along line AA of FIG. On one surface of the disk-shaped base plate 36 formed of pure iron and having a hole in the center, nine cores 25 formed of 3% silicon steel are arranged substantially on the circumference as viewed from the direction of the central axis orthogonal to the plane of FIG. A ring-shaped permanent magnet 24 is provided on the outer periphery of the core and is magnetized in the axial direction. Further, a yoke 30 made of pure iron, a side yoke 31, a spacer 32 made of stainless steel, a spring 27 made of spring steel and having a function as a spring member, and a spring retainer 33 made of carbon steel.
Are stacked and fixed. 3% at the tip of spring 27
A plunger 23 made of silicon steel is fixed and supported at a position facing the core 25. A lever 26 made of tool steel, to which a printing wire 28 made of cemented carbide is joined by brazing, is fixed to the tip of the plunger 23. The printing wire 28 is guided to a predetermined position by the wire guides 34 and 35, and in the case of the present embodiment, the tips are arranged in a straight line in the direction perpendicular to the paper surface of FIG. The back stopper 21 is brought into contact with the tip of the lever 26 during non-printing standby.
Is provided. The back stopper 21 has a resin film portion 21a made of polyimide, which has a hardness lower than that of the metal lever 26 and does not wear the lever 26, a metal portion 21b made of stainless steel having a spring property, and a rubber portion 21c made of fluorine rubber for damping a collision force. It is configured.

During non-printing standby, as shown in the lower half of FIG. 3, the magnetic flux of the permanent magnet 24 (shown by a solid line with an arrow) passes from the yoke 30 through the side yoke 31, the plunger 23, the core 25 around which the coil 22 is wound, It goes around the base plate 36 and returns to the permanent magnet 24. As shown in FIG. 4 which is a sectional view taken along line BB of FIG.
A slit 31a surrounding the plunger 23 is provided along the contour of the slit 23a with the smallest possible gap, and the area of the slit 31a of the side yoke 31 facing the side surface of the plunger 23 is made as large as possible. There is. Therefore, the magnetic resistance between the side yoke 31 and the plunger 23 is small, and most of the magnetic flux entering the side yoke 31 from the permanent magnet 24 flows into the plunger 23 through the minute gap. Unlike an electric circuit, a magnetic circuit is magnetically permeable even in a vacuum, so that there is always a leakage magnetic flux, and a magnetic flux that directly leaks from one magnetic pole of one surface of the permanent magnet 24 to the magnetic pole of the other surface, the side yoke 31, the spacer 32, and the spring 27. There is also a magnetic flux that flows to the plunger 23 via the, but the vacuum and the permeability of spring steel and the saturation magnetic flux density of spring steel are low, and the cross-sectional area of the spring 27 is small. These can be ignored because they are located outside the magnetic circuit that flows into the plunger 23 through the minute gap, and the path becomes long. Therefore, in practical use, the yoke 30 and the side yoke 31 pass through and the plunger passes. A magnetic circuit that goes around the 23, the core 25, and the base plate 36 and returns to the permanent magnet 24 can be considered as an effective magnetic circuit. An attractive force acts between the core 25 and the plunger 23 by the magnetic flux of the permanent magnet 24 passing through this effective magnetic circuit, and the plunger 23 moves to the core 25.
Have been sucked into. Further, since the plunger 23 is supported by the spring 27, at this time, the spring 27
Is biased and stores elastic energy.

Here, in order to explain the spring function of the spring 27, it is modeled as a cantilever and will be described with reference to FIG. In FIG. 6, the origin 0 is the spacer 3 of the spring 27.
2 corresponds to the edge portion sandwiched between the spring retainer 33 and the spring retainer 33. As an elastically deformable effective spring portion of the spring 27, the length l from this edge portion to the rear end of the plunger 23 attached thereto is
Thinking of the range. In addition, the length a from the position where the suction force from the core 25 is received to the rear end of the plunger 23 attached
The range of (3) is considered as a rigid portion that does not elastically deform because the bending rigidity of the plunger 23 is large. With such modeling, the deflection equation of the effective spring portion when the suction force P by the core 25 is received is as follows.

[0024]

[Equation 5]

Where x is the distance in the longitudinal direction of the spring,
y: distance in the spring bias direction, E: Young's modulus,
I: Moment of inertia of area of spring Further, assuming that the spring constant of the spring 27 is k, it becomes as follows.

[0026]

[Equation 6]

As shown in FIG. 7, the cross section of the spring 27 is a rectangle having a width b and a thickness h, so the spring constant k is expressed as follows.

[0028]

[Equation 7]

The maximum stress σmax occurs at the edge portion where x = 0 and is expressed as follows.

[0030]

[Equation 8]

The attraction force P is determined by the amount of magnetic flux passing through the attraction portion, but most of the magnetic flux entering the side yoke 31 from the permanent magnet 24 is the magnetic path with the smallest magnetic resistance, the minute gap, the plunger 23, the core. 25, passing through the base plate 36. Since the spring 27 is located outside this and is not used as a magnetic circuit, the shape and material can be set in consideration of only the above-mentioned spring constant and mechanical strength when setting the spring 27.

At the time of printing, by energizing the coil 22 as shown in the upper half of FIG. 3, a magnetic flux (indicated by a broken line with an arrow) for canceling the magnetic flux of the permanent magnet 24 is generated to generate the core 2
5. The attraction force between the plungers 23 is canceled and the biased elastic force of the spring 27 causes the printing wire 28 to be printed. When the printing is completed, the energization of the coil 22 is also completed and the plunger 23 is again attracted to the core 25 by the magnetic flux of the permanent magnet 24, and the tip of the lever 26 collides with the back stopper 21 and stops. The impact force due to this collision is absorbed by the rubber portion 21c while elastically deforming the resin film portion 21a, the metal portion 21b, and the rubber portion 21c.

In this way, the effective magnetic circuit is formed by the path from the yoke 30 to the side yoke 31 and around the plunger 23, the core 25 and the base plate 36 and back to the permanent magnet 24. All the members constituting this magnetic circuit are pure iron. Since it is made of a material having a high magnetic permeability and a saturated magnetic flux density such as silicon steel, the efficiency of converting electromagnetic energy into kinetic energy is high. Further, since the spring 27 is made of spring steel having lower magnetic permeability and saturation magnetic flux density than the material forming the effective magnetic circuit and high mechanical strength, and is arranged outside the effective magnetic circuit, the leakage magnetic flux passing through the spring 27 is reduced, There is little eddy current loss and heat generation due to the change in magnetic flux in the spring 27. Therefore, the corrosive environment of the spring 27 is not promoted and stress corrosion cracking does not occur in the spring 27.

As described above, in the impact dot head according to the present invention, the magnetic circuit portion and the mechanical spring member are functionally separated, so that the magnetic circuit portion and the mechanical spring member can be designed with a high degree of freedom in pursuit of their respective performances. It is possible to realize an impact dot head with high efficiency and long life.

[0035]

As described above, in the impact dot head of the present invention, the spring member is arranged outside the magnetic circuit, and the saturated magnetic flux density and the magnetic permeability of the spring member are higher than those of the constituent material of the magnetic circuit. By using a low one, the magnetic circuit part and the mechanical spring member are functionally separated,
It is possible to design with a high degree of freedom by pursuing the performance of the magnetic circuit part and the mechanical spring member, and since the leakage flux passing through the spring member can be reduced, stress corrosion cracking of the spring member is also prevented and energy conversion efficiency is improved. It is possible to provide an impact dot head that has a long life and a long life and high reliability.

[Brief description of drawings]

FIG. 1 is a schematic plan view of a mechanical portion of a serial impact dot printer equipped with an impact dot head of the present invention.

FIG. 2 is a schematic front view of a mechanical portion of a serial impact dot printer equipped with the impact dot head of the present invention.

FIG. 3 is a sectional view taken along the line AA of FIG. 2 showing an embodiment of the impact dot head of the present invention.

FIG. 4B of FIG. 3 of the impact dot head of the present invention.
It is a -B sectional view.

FIG. 5 is a cross-sectional view of an impact dot head in the related art.

FIG. 6 is a view showing a spring member modeled as a cantilever.

FIG. 7 is a diagram showing a cross-sectional shape of a spring member.

[Explanation of symbols]

 1 Carriage 2 Impact Dot Head 3 Platen 4 Ink Ribbon 5 Printing Paper 6 Connector 7 Bottom Plate 8 Flexible Printed Circuit 9 Photocoupler 10 Fin 11 Carriage Drive Motor 12 Drive Belt 13 Encoder 21 Back Stopper 22 Coil 23 Plunger 24 Permanent Magnet 25 Core 26 Lever 27 Spring 28 Print Wire 29 Slit 30 Yoke 31 Side Yoke 32 Spacer 33 Spring Presser 34 Wire Guide 35 Wire Guide 36 Base Plate

Claims (1)

[Claims] 1. During standby, strain energy is stored by biasing a spring member with a magnetic flux of a permanent magnet, and the magnetic flux of the permanent magnet is canceled by selectively energizing an electromagnetic coil to cause the spring member to have In an impact dot head that performs a printing operation by converting strain energy into kinetic energy, the spring is provided outside a closed magnetic circuit from one magnetic pole surface of the permanent magnet through the electromagnetic coil to the other magnetic pole surface of the permanent magnet. An impact dot head, characterized in that a member having a saturation magnetic flux density and a magnetic permeability lower than that of the constituent material of the closed magnetic circuit is used as the material of the spring member.