JPH0626897B2 - Print head - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a print head of an impact type printer, and particularly to bending of a spring member by attraction force of a permanent magnet, and strain energy stored in the spring member, The present invention relates to a cancel-type print head in which the magnetic attraction of a permanent magnet is canceled by the magnetic flux of an electromagnet and is given to a suction member as printing energy.

[Background of the Invention]

The print head of the impact type printer roughly biases the spring member by the attraction force of the electromagnet, stores strain energy in the spring member, and eliminates the attraction force of the electromagnet.
The type that causes the strain energy of the spring member to act as the printing operation force, the type that uses the accidental electromagnet, and the biasing force of the permanent magnet biases the spring member to store the strain energy, and the magnetic flux of the electromagnet permanently There is a type in which the strain energy of the spring member acts as a printing operation force by canceling the attractive force of the magnet, a so-called cancel type. The cancel-type print head has been widely used in recent years because it has advantages that it does not generate heat during standby as compared with an electromagnet drive type, or that it can secure a large attractive force even with a small permanent magnet.

In this type of print head, since the printing wire and the suction member equipped with the printing wire are caused to fly by the strain energy accumulated by the bias of the spring member, the spring force of the spring member immediately becomes the printing energy of the printing wire. Therefore, the magnitude of the spring force of the spring member greatly affects the print quality. Further, with respect to the rotational movement of the suction member, the clarity of the pivotal fulcrum has a great influence on the printing quality and speeding up.

A conventional print head of this type is a flat plate single-spring type as described in JP-B-58-42033, a cross spring type as described in JP-A-56-42665, etc. However, it is difficult to adjust the spring force of the spring member for ensuring good print quality, and it is necessary to strictly control the dimensions of the parts, which is expensive. See also
The flat plate single-spring spring described in Japanese Patent No. 2033 has an uncertain rotation fulcrum and is not suitable for speeding up. In order to make up for these drawbacks, there has been proposed a device in which the rotation fulcrum of the suction member is provided on the yoke magnetic pole surface and the spring force can be adjusted, as described in JP-A-58-177372.

However, in this type, since the portion of the yoke magnetic pole surface where the rotation fulcrum of the attraction member comes into contact is worn, the attraction force of the permanent magnet decreases over time, and the position and orientation of the rotating attraction member change. Since the amount of bias of the spring changes and the constant strain energy cannot be maintained at all times, the print quality deteriorates and the operation becomes unstable, and high-speed high print quality performance cannot be maintained for a long time. Also, since the suction force decreases with time, the spring force cannot be increased, and a spring member having a high spring constant cannot be used, so that a large return force is applied to the printing wire and the suction member including the printing wire. Cannot be given, that is, the force to return after the printing wire collides with the printing paper (difference between the attractive force of the permanent magnet and the spring force)
Therefore, there is a drawback in that the return performance is significantly deteriorated due to an external lateral pressure received from a paper step portion or the like which occurs when the printing paper is jammed.

[Object of the Invention]

The present invention has been made based on the above matters, and an object of the present invention is to provide a print head capable of maintaining high-speed printing performance and reliability for a long period of time.

[Outline of Invention]

In order to achieve the above-mentioned object, the present invention is a print head in which a suction member is moved by a magnetic attraction force, and strain energy obtained by biasing a spring member provided in the suction member is used as an impact printing force. The attraction member is provided so that the spring member is located in a plane substantially parallel to the magnetic attraction surface of the attraction member, and the rotation of the attraction member is provided on the yaw magnetic pole surface forming a magnetic circuit with the attraction member. In a print head that forms a dynamic fulcrum and attracts the suction member to the magnetic pole surface of the core to generate a biasing force on the spring member when the suction member is in contact with the yoke, the suction member, the core, and the magnetic pole surface of the yoke are By applying a surface treatment based on magnetically permeable nickel and increasing the surface treatment hardness of the yoke and yoke to the suction member, the wear of the core and yoke is reduced to reduce suction. Temporal position of wood, in which was allowed a time reduction of the suction force of the permanent magnet to a small one with allowed to variations in posture small.

Example of Invention

 Embodiments of the present invention will be described below with reference to the drawings.

1 and 2 show an embodiment of the print head of the present invention. As shown in these drawings, the print head of the present invention has an outer frame structure including a nose 1, a housing 2, and a heat sink 3. This nose 1 is provided with a guide 5A for the print wire 4 and its center guide 5B. Protrusions 6 are formed on the outer periphery of the heat sink 3 to improve heat dissipation.

In a space defined by the housing 2 and the heat sink 3, a lever portion 7 having the print wire 4 and a drive mechanism 7A for the lever portion 7 are provided. Lever part 7
As shown in FIG. 2, a plurality of are provided in the housing 2 in the radial direction and in the circumferential direction. This lever part 7
As shown in FIG. 3, it is composed of a lever body 8, a suction member 9 and a spring member 10. The lever body 8 has the printing wire 4 fixed to the tip thereof. The suction member 9 is made of a magnetically permeable material, and the lever body 8 is fixed to one side of the suction member 9,
A plate-shaped spring member 10 is fixed to the other end. The attachment portion of the spring member 10 to the suction member 9 is set to be substantially the same as the magnetic attraction surface 9A of the suction member 9 as shown in FIG. As shown in FIG. 3, the end of the spring member 10 is provided with a hole 11 for use in adjusting the spring force, and the spring member 10 is bent at a portion where it is attached to the suction member 9 and the spring end. Has been given.

As shown in FIG. 1, the structure of the drive mechanism 7A for the lever portion 7 includes a core 12, a yoke 13, a core 12, a permanent magnet 14 arranged between the yokes 13, and a coil 15 provided on the core 12. ing. The yoke 13 has a magnetic pole surface 13A arranged close to the magnetic pole surface 12A of the core 12. These pole faces 13
A and 12A face the suction member 9. Core 12, yoke 13,
The permanent magnet 14 and the attraction member 9 are the permanent magnet 14 and the coil.
The permanent magnet 14 forming the magnetic circuit 15 generates a magnetic flux that attracts the attracting member 9 toward the core and the yoke. The coil 15 is set so as to cancel the magnetic flux of the permanent magnet 14 by its excitation. The core 12, the yoke 13, the permanent magnet 14 and the heat sink 3 are fastened and fixed to the housing 2 with screws 16. In the lever portion 7, the attraction member 9 is normally attracted to the magnetic pole surfaces 12A and 13A of the core 12 and the yoke 13 by the magnetic attraction force of the permanent magnet, so that the core 12,
It is arranged in front of the yoke 13. The rotation fulcrum of the lever portion 7 is constituted by the corner portion 9B of the magnetic attraction surface 9A of the attraction member 9 and the magnetic pole surface 13A of the yoke 13. A support 17 is provided on the printing paper side of the yoke 13. In order to prevent the swinging of the lever portion 7 when the lever portion 7 rotates, the housing 2
Has a lever guide 18 for guiding the lever body 8 of the lever portion 7.

The means for applying a spring force to the spring member 10 is the housing 2
It has a pushing member 19 screwed into. This pushing member 19
Has a spherical portion 20 at its tip. This spherical part is the third
As shown in the figure, it engages with a hole 11 provided at the end of the spring member 10. By pushing and pulling the pushing member 19, the spring member 10 can be biased and the spring force thereof can be adjusted.

In the case of the present embodiment, at least the magnetically attracting surface 9A and the corners 9B of the attracting member 9 are chemically nickel-plated with a thickness of about 10 .mu.m to maintain Vickers hardness Hv500-700. Further, the magnetic pole surfaces 12A and 13A of the core 12 and the yoke 13 are made of silicon carbide (SiC) having a Vickers hardness of Hv3000 or more.
10 μm on the magnetic pole surface 12A of the core 12 by chemical nickel plating with the addition of the fine powder, so-called electroless mixed nickel plating.
m, the magnetic pole surface 13A of the yoke 13 is provided with a thickness of 20 μm,
After plating, Vickers hardness is obtained by hardening heat treatment at 300 ℃ or more
Hardness of Hv1100 or higher is maintained. In this case, the material for plating the suction member 9, the core 12 and the yoke 13 is based on nickel. Particularly, in the case of the core 12 and the yoke 13, nickel is ferromagnetic due to heat treatment. Although the magnetic attraction surface of each of the core 12 and the yoke 13 is plated, there is little adverse effect as a void on the magnetic action, that is, the attraction force of the permanent magnet 14 is small even if the plating thickness fluctuates to some extent. Is capable of effectively acting on the suction member 9. If this plating material is a non-magnetic material such as zinc or chrome plating and it is difficult to control the accuracy of the plating thickness during the plating process, the dimension of the plating thickness will affect the magnetic circuit as an air gap. The difference in the plating thickness causes a large difference in the suction force acting on each suction member 9, and the adjustment value of the bias amount of the spring member 10 also fluctuates significantly, which has a large adverse effect on the high-speed printing performance. It will be.

Next, the operation of the above-described embodiment of the print head of the present invention will be described.

Before the start of printing, the attracting member 9 is moved to the core 12 and the yoke 13 by the magnetic attracting force of the permanent magnet 14 as shown in FIG.
Are attracted to the magnetic pole surfaces 12A and 13A. At this time, the bias of the spring member 10 stores strain energy. The spring force related to this strain energy can be adjusted by pushing and pulling the pushing member 19. Next, when a current is passed through the coil 15, the magnetic flux of the permanent magnet 14 is canceled out, so that the attraction member 9 is rotated by the spring force of the spring member 10 by the corner portion 9B of the magnetic attraction surface 9A of the attraction member 9. It is rotationally displaced around the fulcrum. Therefore, the print wire 4 is guided by the guide 4 and the center guide 5 of the nose 1,
The printing paper is struck through the ink ribbon at its tip.
As a result, dots forming characters are printed on the printing paper.

In the above-described printing operation, the spring member 10 exhibits a cantilever-shaped flexure curve between the connecting portion with the suction member 9 and the engaging portion of the pushing member 19, so that unnecessary stress does not act. It is advantageous against breakage. Further, as described above, the rotation fulcrum of the lever portion 7 is the corner portion 9B of the magnetic attraction surface 9A of the attraction member 9, and the turning radius of the lever portion 7 is the length from the corner portion 9B to the printing wire 4. The size of the spring end is smaller than that of a conventional spring end that is fixedly supported. As a result, the moment of inertia of the lever portion 7 is reduced, and the speed can be increased. Further, the attraction member 9 is pressed against the magnetic pole surface 13A of the yoke 13 by the component force of the attraction force of the permanent magnet 14 and the pressing force of the pushing member 19, and the fluctuation of the rotation fulcrum is small.

Now, in this type of print head, that is, in the print head that accelerates the suction member by the strain energy of the spring member to perform printing, ensure good print quality, that is, stable printing force or operation with stable operation time. To do
It goes without saying that the strain energy stored in the spring member is a very important factor.

This is the point where the greatest effect of the present invention is achieved. Further description will be given below.

FIG. 4 shows a spring pressing portion and a suction member. This figure shows the initial state in which the suction member 9 is attracted to the core 12 and the yoke 13, but when the coil 13 is energized, the suction member 9 uses the corner portion 9B, which is a rotation fulcrum, as a fulcrum in the x direction. Rotate to. At this time, the force acting on the corner portion 9B and the magnetic pole surface 13A of the yoke 13 is the sum of the pressing force F ₁ of the spring member 10 and the attraction force F ₂ of the core 12 without considering the inertial force. Since the repetitive operation is performed in the state where such a force acts, the wear resistance treatment of the corner portion 9B and the magnetic pole surface 13A of the yoke 13 is extremely necessary for ensuring the life of the print head, that is, the wear resistance. Will be important.

FIG. 5 shows a comparison of the abrasion states when the abrasion resistance treatments are different. FIG. 5 (a) shows a corner portion 9B of the suction member 9.
In this case, the hardness of plating on the magnetic pole surface 13A of the yoke 13 is lower than the wear resistance of the portion, that is, the hardness of the latter is larger than that of the former with respect to the change over time. The yoke magnetic pole surface 13A is worn and dented from the position shown by the dotted line in the initial state as shown in the figure, and the corner portion 9B of the suction member 10 is sunk into the yoke 13. The magnetic attraction surface 9A of the attraction member 9 comes into contact with the corner portion 12B of the core 12, and the posture in which the attraction member 9 is attracted by the core 12 is inclined in the initial state as shown in this figure. Obviously, the posture of the spring member 10 also changes, and the pressing force F ₁ decreases. This decrease in the pressing force of the spring directly affects the printing force, which not only decreases the printing force, but also disables printing in a predetermined operation cycle, that is, high-speed printing becomes impossible. . Further, since the suction member 10 tilts in the suction state, the wire 4 remains in a state where it travels from the initial state at the tip of the print head, that is, a state where it projects from the bearing, and when the print head moves, the ribbon 4 moves. , The force may cause breakage of the wire tip, etc.
A deadly failure will occur.

FIG. 5 (b) is a view showing the most preferable example of the embodiment of the present invention.

In this case, contrary to the above-mentioned example, the plating hardness of the corner portion 9B of the suction member 9 is lower than the plating hardness of the magnetic pole surface 13A of the yoke 13, and both of them have good wear resistance and are made of a magnetically permeable material. It is provided with plating that has little effect on magnetic attraction. In this case, with respect to the operation over time, the point where wear is most advanced is the corner portion 9B of the suction member 9, and the corner portion is rounded from the shape shown by the dotted line in the initial state to the shape shown by the solid line in this figure. The magnetic pole surface 13A of the yoke 13 plated with electroless mixed nickel having hardness higher than this corner and having excellent wear resistance added with SiC or the like
The wear can be small.

That is, unlike the previous example, the wear of the suction member 9 only progresses at the corners 9B of the suction member 9, so that the posture of the suction member 9 does not change over time, and the pressing force of the spring member 10 does not change. The fluctuation disappears. Further, in this state, the position of the rotation branch between the corner 9B of the suction member 9 and the yoke magnetic pole surface 13A changes by ΔL as shown in FIG. Pressing force F _{1 at} the pressing point of
Even if the pressure is reduced due to slight wear of the pressing portion, the suction member 9
The rotation moment for is the distance L from the fulcrum to the pressing point.
Is increased by ΔL, the decrease is prevented, a constant moment can be maintained, and the acceleration performance of the spring with respect to the suction member 9 is not changed. That is, since the strain energy of the spring obtained by the initial adjustment is kept constant over time, there is no change in the printing force and the repeated operation cycle, and it is possible to perform stable high-speed and high-quality printing operation for a long period of time. Will have a positive effect.

More specifically, not only the plating hardness of the corner portion 9B of the suction member 9 is made lower than the hardness of the magnetic pole surface 13A of the yoke 13 at random, but the former hardness is Vickers hardness Hv500-700. ， The latter hardness is Vickers hardness Hv11
By keeping it at 00 or more, the wear amount of both the yoke magnetic pole surface 13A and the corner portion 9B of the suction member 9 can be minimized. This will be described with reference to FIG. Sixth
Figure (b) is a schematic diagram of electroless mixed nickel plating to which SiC is added. On the base material 30, there is an electroless mixed nickel plating layer 31 having a thickness of 20 μm, and the size of this layer is 0.5 to 5 μm.
There are some SiC particles 32 and a nickel-plated base material 33. The fact that it is measured as Hv1100 by Vickers hardness is actually
The hardness of the nickel-plated base material 33 is Hv850 to 950 because the size of the pressure wheel 34 of the Vickers hardness tester is about 9 μm.
This means that the SiC particles 32 having a hardness of about Hv3000 are averaged and measured. Therefore, even though the electroless mixed nickel plating hardness is Hv1100, it is actually Hv850-950 and Hv30.
The 00 part will be present. Temporarily, suction member 9
The hardness of the corner portion 9B is set to Hv850 to 950, and the nickel plating base material 33 of the electroless mixed nickel plating layer 31 of the yoke magnetic pole surface 13A
If the same level as the above, the wear of the nickel-plated base material 33 progresses, as shown in FIG. 6 (c), the SiC particles 32 are easily separated, and the wear is further promoted.
Even though the hardness of the corner portion 9B is lower than that of the yoke magnetic pole surface 13A, the effect of reducing the wear amount is small. Therefore, the hardness of the corner portion 9B of the suction member 9 is set to the hardness of the nickel-plated base material 33.
If you choose Hv500-700, which is slightly lower than Hv850-950, the wear of the nickel-plated base material 33 will be small and the SiC
It is conceivable that separation of particles will be less likely to occur. Therefore, the wear of the yoke magnetic pole surface 13A is significantly reduced. Further, it is also advantageous for the wear of the corner portion 9B of the suction member 9 because the hardness difference with the counterpart, that is, the nickel-plated base material 33 that occupies most of the plated layer of the yoke magnetic pole surface 13A, is relatively small. Based on the above idea, the surface treatment of the yoke pole surface is
For the electroless mixed nickel plating with C added and the Vickers hardness of Hv1100, the surface treatment of the corner 9B of the suction member 9 was performed with the electroless nickel plating of Vickers hardness of Hv850-950 and Vickers hardness of Hv500-700. The experiment was confirmed about the kind. As a result, as shown in FIG. 6 (a), when the hardness of the corner portion 9B of the suction member 9 is Hv500-700, Hv850-
It was confirmed that the wear M of the magnetic pole surface 13A of the yoke E could be made significantly smaller than that of 950. It was also confirmed that at this time, the wear amount of the corner portion 9B of the suction member 9 can be suppressed to the extent of 1 μm or less.

As mentioned above, the yoke magnetic pole surface
The surface treatment of 13A is Vickers hardness Hv1100 or more by electroless mixed nickel plating, and the surface treatment of the corners of the suction member 9 is Vickers hardness Hv500-700 by electroless nickel plating, which can significantly reduce the wear amount over time. it can.

Furthermore, this embodiment has another effect as described below.

In FIG. 7, the amount of wear of the yoke magnetic pole surface 13A over time is large,
FIG. 5 (a) shows the state at the time when the process has not yet progressed. In the case of FIG. 5 (a), the magnetic pole surface 12A of the core
A gap G1 is generated between the magnetic attraction surface 9A and the magnetic attraction surface 9A of the attraction member 9. In the case of FIG. 7, a gap G2 is generated between the magnetic attraction surface 9A of the attraction member 9 and the yoke magnetic pole surface 13A. In any case, it means that the effect of the attraction force of the permanent magnet 14 acting on the attraction member 9 is reduced with the passage of time due to the generation of voids. FIG. 8 shows the relationship between the rotational momentum of the suction member 9, that is, the displacement stroke of the printing wire 4, the suction force of the permanent magnet 14 and the spring force of the spring member 10. The suction force in the case of FIGS. 5 (a) and 7 decreases with respect to the initial suction force shown by the solid line in FIG. 8 as shown by the broken line. Considering this decrease in attraction force over time, the initial spring force must be adjusted to a low value at the displacement stroke O as indicated by the alternate long and short dash line, and in order to obtain sufficient strain energy with a low spring force. Therefore, it is necessary to use a spring member having a small spring constant. The diagonal line to the left in FIG. 8 indicates the strain energy at this time. At this time, the restoring force of the wire 4 at the displacement stroke S point becomes the difference between the attraction force and the spring force, that is, F3 in FIG. 8, and a large restoring force cannot be obtained. However, according to the present invention, the yoke pole face
The amount of wear of 13A over time can be made extremely small, and the attraction force of the permanent magnet 4 can be secured over time with almost the same attraction force as the initial attraction force indicated by the solid line in FIG. It is possible to adjust to a high spring force at the point of the displacement stroke O as shown by the two-dot chain line. Therefore, a spring member having a large spring constant can be used to obtain sufficient strain energy, and a large restoring force of the wire 4 at the displacement stroke S point can be obtained as indicated by F4. The strain energy at this time is indicated by the diagonal line to the right in FIG. Needless to say, the fact that the restoring force of the wire 4 can be increased is advantageous for high-speed printing, and further, when a jam occurs on the printing paper 23,
It is difficult to prevent the return operation of the wire 4 from being hindered by the external lateral pressure that the print wire 4 receives from the step generated by the paper, and avoid the worst case in which the print wire 4 is broken even when the print paper 23 jam or the like is abnormal. be able to. FIG. 9 shows a schematic diagram in the case of printing the overlapping portion of the printing paper caused by the printing paper jam.

The embodiment of the present invention and the effect thereof have been described above.
Regarding the plating of the core and yoke, not only silicon carbide SiC but also titanium carbide is an additive.
It is clear that fine powders such as TiC and tungsten carbide WC may be used. In addition to the plating by the electroless mixed nickel plating method, which is added to the plating process and performed at the same time, after plating by the ordinary chemical nickel plating method, the above-mentioned kind of high hardness fine powder is plated by mechanical means. It goes without saying that a means for diffusing into the surface layer and increasing the plating hardness higher than the plating base material hardness may be used. In the present invention, nickel-based plating is selected as the base of the wear-resistant material, but this does not only eliminate the effect of voids on the magnetic attraction as described above, but also nickel. When the wear of plating progresses and wear powder is generated, this becomes nickel oxide NiO due to heat of wear and oxygen in the air. This nickel oxide becomes fine powder, and its hardness is as soft as Hv450,
In other words, it enters between the suction member, the yoke, and the core to act as a lubricant for both, which also has the effect of reducing the degree of subsequent wear.

〔The invention's effect〕

According to the present invention, it is possible to provide a print head which is capable of high-speed printing, has a small spring strain energy variation, has a long life, and has high reliability, and has a dramatic effect.

[Brief description of drawings]

FIG. 1 is a sectional view of a print head structure according to an embodiment of the present invention. FIG. 2 is a plan view of the print head of FIG. Third
The figure is a structural perspective view of a main part according to the present embodiment. 4 and 5 are sectional views of FIG. FIG. 6 is a wear amount comparison diagram. FIG. 7 is a structural cross-sectional view of the main part according to the present invention. Figure 8 shows
A characteristic diagram of the suction force and the spring force. FIG. 9 is a schematic view of a paper jam. 1 ... Nose, 2 ... Housing, 3 ... Heat sink, 4 ... Wire, 5A ... Guide, 5B ... Center guide, 6 ... Protrusion, 7 ... Lever part, 7A ... Drive mechanism, 8 ... ... Lever body, 9 ... Suction member, 9A ... Suction action surface, 9B ... Suction member corner, 10 ... Spring member, 11 ... Hole, 12 ... Core, 12A ... Core magnetic pole surface, 13 ... … Yoke, 13A …… Yoke magnetic pole surface, 14 …… Permanent magnet, 15 …… Coil, 16 …… Screw, 17 …… Support, 18 …… Lever guide, 19 …… Pushing member, 20 …… Pushing member Spherical part , 21 …… print head, 22 …… ribbon, 23 …… printing paper, 24 …… platen.

Claims (3)

[Claims] 1. A yoke for forming a magnetic circuit between the attracting member and a magnetic member by moving the attracting member, and strain energy obtained by biasing a spring member provided on the attracting member is used as impact printing force. The corner portion of the suction member is brought into contact with the magnetic pole surface to form a rotation fulcrum, and the suction member is attracted to the magnetic pole surface of the core in a state where the absorption member is brought into contact with the yoke to generate a biasing force in the spring member. In the print head in which the rotation instruction portion of the member, the surface facing the magnetic pole surface of the core, and the magnetic pole surface of the yoke and the core are magnetically permeable, the surface treatment of the suction member is Vickers hardness Hv5.
A print head having a hardness of 00 to 700 and a surface treatment of a magnetic pole surface of a yoke and a core having a Vickers hardness of Hv1100 or more. 2. The absorbing member is electroless nickel plated to have a Vickers hardness of Hv500 to 700, and at least the magnetic pole surface of the yoke and the core is made of Si.
The printing according to claim 1, wherein electroless nickel plating containing hard fine powder such as C, WC, or TiC is applied, and a hardening heat treatment is performed at 300 ° C or more to obtain a Vickers hardness Hv1100 or more. head. 3. The thickness of the surface treatment of the magnetic pole surface of the core and the surface of the suction member facing the magnetic pole surface of the core and the yoke is made thinner than the thickness of the surface treatment of the magnetic pole surface of the yoke. The print head according to claim 1 or 2.