JPS6212609Y2 - - Google Patents

Description

[Detailed description of the invention] In recent years, dot matrix printers that express characters by an array of dots have become widely used. In particular, dot ink pact printers, which print dots by mechanically striking the tip of a needle onto printing paper via an ink ribbon, have become widely used as office printers because they can print multiple sheets of paper overlappingly. Summer. Typical examples include serial printers that print while moving along the lateral direction of printing paper, and recently, dot matrix type line printers have also appeared and are becoming widespread. This dot matrix type line printer has multiple hammers that print dots every character or several characters, and the hammers are swung horizontally by the width of the character they are in charge of, and at the same time move the printing paper vertically. However, characters are formed in the form of a dot matrix by operating the hammer at a predetermined position.

The present invention relates to a print head for the above-mentioned dot matrix type line printer.

More specifically, it has a yoke equipped with a permanent magnet, a cantilever leaf spring with one end fixed to one end of the yoke and the other end free, and a so-called hammer pin on the front surface near the free end of this leaf spring. The printing head is equipped with a side yoke placed on the left and right sides of this leaf spring with a slight gap between them, and an ink ribbon, paper, and platen placed in front of each leaf spring. This invention relates to a printing head of a printer called a so-called spring charge type dot line printer that prints by striking.

Conventionally, the print head of a spring charge type line printer has a so-called cantilever structure in which one end of a leaf spring 1 is fixed to a base 2, which is one of the yokes, by a fixing plate 3, and the other end is free, as shown in FIG. The base 2 is connected to the yoke 4 via the permanent magnet 5.
It forms a closed magnetic path that connects to the base 2 via the leaf spring 1. Therefore, the tip of the leaf spring 1 is attracted to the front surface of the yoke 4, and the leaf spring 1 is in a distorted state. When printing there, the yoke 4
By applying a current to the coil 6 wound around the coil 6 and canceling the magnetic flux of the permanent magnet 5, the free end of the leaf spring 1, which was attracted to the surface of the yoke 4, is released from the surface of the yoke 4, and the free end of the leaf spring 1, which is held by the leaf spring 1, is released from the surface of the yoke 4. Jump forward with distortion energy. Due to this movement, the hammer pink attached to the tip of the leaf spring 1 hits the ink ribbon 9 and paper 10 on the platen 8 to print. Therefore, in such a spring charge type dot line printer, the printing condition depends on the strain energy of the leaf spring, but the strain energy is also determined by the spring constant of the leaf spring, so the spring constant of the leaf spring is The magnetic circuit is designed so that it can be calculated and the leaf spring can be attracted.

Dot printers generally require high speed. In other words, in order to achieve high speed, it is necessary to speed up each cycle of the leaf spring's attraction to the yoke, adsorption, detachment, and impact on the platen, and this requires increasing the natural frequency of the leaf spring. Ru. In this case, the natural frequency of the leaf spring is proportional to the square root of the spring constant of the leaf spring. Therefore, in order to achieve high speed, it is sufficient to increase the spring constant, but in order to do so, it is necessary to increase the magnetic flux required to attract the leaf spring, and the magnetic part that generates the magnetic flux, that is, the permanent magnet The yoke that forms the magnetic path has to be made larger, and along with this, the current flowing through the coil to release the leaf spring from the permanent magnet also needs to be increased, which requires a large power source, etc., and other inconveniences. It was supposed to occur. In order to eliminate these inconveniences, the challenge is to make the magnetic circuit made up of the magnet and yoke as small as possible, and to design a magnetic circuit that does not reduce the adhesion force of the leaf spring to the small magnet. Various types of line printer print heads have been proposed in the past, but no satisfactory solutions have been found.

As one of the conventional methods, FIG. 1 mentioned above will be explained. This has a yoke 4 with a coil 6 wound around a permanent magnet 5, and a leaf spring 1 at the tip of the yoke 4.
One end of is located. The other end of the leaf spring 1 is fixed to a yoke called a base 2 on which a permanent magnet 5 is placed, so that the flow of magnetic flux from the permanent magnet 5 is
It has two loops. This type of print head is called a one-pole type. This method has fewer parts and can reduce costs, but on the other hand, it is not possible to make the leaf spring 1 thicker than the yoke 4, so the magnetic flux flowing from the permanent magnet 5 to the yoke 4 can have a sufficient magnetic path in the leaf spring 1. Therefore, the leaf spring 1 becomes magnetically saturated.
Therefore, the magnetic flux that flows through the leaf spring 1 attracts the leaf spring 1, so the attractive force is small. Therefore, the spring constant of the attracted leaf spring 1 cannot be increased, and as a result, the speed cannot be increased. It was hot.

Therefore, as a means to increase the attractive force, a printing head using a magnetic path complementing means called a side yoke 11 was devised, as shown in FIG. This printing head is of the one-pole type described above, but a yoke made of a magnetic material, that is, a side yoke 11 is arranged with a slight gap left and right on the left and right sides of the leaf spring 1, and the base of the side yoke 11 is a leaf spring. 1 is sandwiched between the bases 2 and fixed together by a fixing plate 3, forming a closed magnetic path that goes around the permanent magnet 5, the yoke 4, the tip of the leaf spring 1, the side yoke 11, and the base 2. are doing. In other words, the magnetic flux emitted from the permanent magnet 5 passes through the yoke 4 on the upper surface of the magnet, and passes through the yoke 4.
The tip reaches the tip of leaf spring 1 from the tip. As illustrated in the enlarged view around the tip of the leaf spring 1 shown in FIG. Bypass magnetic flux 13 flowing more into the side yoke 11
occurs, forming a loop that reaches the permanent magnet 5 via the base 2. To explain the flow of magnetic flux using an equivalent circuit, the one-pole type shown in Fig. 1 whose steady state is the state in which the leaf spring is saturated is shown in Fig. 4, and the side yoke type shown in Fig. 2 is shown in Fig. 4. 5
It becomes a figure. In the one-pole type, the equivalent circuit of which is shown in _FIG . _p reaches the tip of leaf spring 1 while decreasing due to permeance R _t of leakage in the middle of the magnetic path, but the magnetic flux that actually contributes to the attraction and attraction of the leaf spring is the same as the magnetic flux φ _s that saturates leaf spring 1. There is a restriction. However, in the side yoke type shown in FIG. 5, the permeance P _l between the leaf spring 1 and the side yoke 11 is parallel, so the permeance P _g of the part that contributes to suction and adsorption
The magnetic flux φ flowing in is φ=(1+2P _l /P _s )φ _s . Therefore, the magnetic path that contributes to the attraction and attraction of the leaf spring 1 has been expanded, and the magnetic flux flowing from the yoke 4 to the leaf spring 1 has increased, so the attractive force has also increased, and the spring constant of the leaf spring 1 has therefore increased. Since it can also be made larger, it is possible to increase the speed.

However, in the conventional side yoke type print head in which the side yoke 11 is simply provided as shown in FIGS. 2 and 3, the leaf spring 1 attracts the yoke 4,
In contrast, the side yoke 11 has one end simply fixed to the base 2, and no special consideration has been taken to form an optimal magnetic path. .

That is, as shown in Fig. 6, which shows the cross section of only one print head, and in Fig. 7, which shows an enlarged view of the suction and adsorption portion, it is desirable that when leaf spring 1 is attached to yoke 4, leaf spring 1 and tip surface 14 of yoke 4 are in close contact with each other so that the suction force is maximized. When leaf spring 1 is attached to yoke 4, leaf spring 1 bends along a deflection curve, so that the back surface of the leaf spring in a free state not receiving magnetic force or distortion energy and the tip surface of yoke 4 cannot be in close contact with each other if they are parallel. Therefore, it is necessary to incline the fixed end of the base that fixes leaf spring 1 by the deflection angle of the leaf spring, or to tilt base 2 in such a way that the leaf spring 1 is in contact with the tip surface of yoke 4.
It is necessary to incline the yoke 4 with respect to the leaf spring 1. However, since the side yoke 11 is also fixed to the base 2 together with the leaf spring 1, and must have a size and shape that will not bend due to the suction force acting on the leaf spring 1, when the leaf spring 1 is attracted and attached, the side of the leaf spring 1 protrudes from the side of the side yoke 11, reducing the area that faces it or separating them completely, and the effective distance between the side of the leaf spring 1 and the side of the side yoke 11 increases. This protrusion amount is particularly large at the tip of the leaf spring 1, which is the attraction area. As an example, if the thickness of the leaf spring is 0.7 mm and the amount of movement due to attraction is 0.4 mm, then even if we consider it simply, it will protrude by about 0.3 mm. For this reason,
When the leaf spring 1 is attracted, the magnetic flux that entered the leaf spring 1 from the yoke 4 flows into the side yoke 11, bypassing the leaf spring 1 through the air, so that the resistance to the magnetic flux between the leaf spring 1 and the side yoke 11 becomes large. That is, the permeance _Pl becomes small in the equation φ=(1+ _2Pl / _Ps ) _φs in the equivalent circuit shown in Figure 5, so that the magnetic flux flowing in the attracting and adsorbing portion of the leaf spring becomes small, and the attracting and adsorbing force also becomes small. For this reason, the effect of the side yoke was not fully exerted in the conventional side yoke.

The present invention eliminates the above-mentioned drawbacks of the conventional side yokes, forms a magnetic circuit that fully fulfills the original function of the side yokes, and efficiently utilizes the attraction energy of the magnets, resulting in high-speed performance. This invention provides a spring charge type dot line printer.

According to the present invention, one end of the leaf spring is fixed to the base so that the suction side surface of the leaf spring adsorbed to the yoke and the surface of the side yoke in the leaf spring suction direction effectively match. There is obtained a print head for a dot type line printer characterized in that the other end of the yoke, which was conventionally a free end, is bent in the suction direction of the leaf spring and fixed.

The present invention will be described below with reference to drawings showing embodiments. FIG. 8 is a schematic three-dimensional view showing an embodiment of the present invention with a portion cut away, and FIG.
FIG. On the upper surface of the permanent magnet 5, there are yokes 4 arranged in a line. Also each yoke 4
There is a coil 6 for canceling the magnetic flux flowing from the permanent magnet 5. At the tip of each yoke 4 there is a leaf spring 1 having a hammer pin 7 for printing dots, and on the left and right sides of the leaf spring 1 there are also sides fixed to the base 2 with a fixing plate 3 at the same time as the leaf spring 1. In this embodiment, the free end of the yoke head is particularly integrated, and the protruding portion of the leaf spring 1 is shaped like a window so that a plurality of side yokes 15 can be bent and fixed at the same time. There is. Further, in front of the hammer pin 7, a sheet 10 on which printing is to be performed via an ink ribbon 9 is arranged on a platen 8. In this embodiment, as a means for fixing the integrated free end of the side yoke 15 in a bent state, an L-shaped support plate 16 made of a non-magnetic material is provided, for example, at the rear of the print head. It is fixed to the base 2, and the head of the side yoke 15 is fixed to the end of this support plate 16. At this time, the head of the side yoke 15 is adjusted so that the inner surface 17 of the side yoke 15, that is, the surface in the suction direction of the leaf spring 1, is effectively aligned with the suction surface when the leaf spring 1 is attracted to the yoke 4. Part of the support plate 1
Flex it in 6 directions and fix it. Of course, this adjustment may be performed by adjusting the length to a predetermined length using the machine precision of cutting the support plate 16, but it is easier and less costly to adjust using the spacer 18 sandwiched between the fixed parts.

In the print head configured in this way, when the leaf spring 1 is attracted to the yoke 4, the magnetic flux flowing from the yoke 4 not only flows within the leaf spring 1 itself toward the base 2, but also flows from both sides of the leaf spring 1 to a minimum. Since the flow passes through a short gap and flows to the left and right side yokes 15, the permeant P _l between the side surface of the leaf spring 1 and the left and right side yokes 15 increases, and is expressed by the formula φ = (1 + 2P _l /P _s ) φ _s As shown, the magnetic flux φ flowing into the attraction section increases. Therefore, the suction force F that attracts the leaf spring 1 is F∝
As expressed by ^φ2 , the attractive force increases, the spring constant of the leaf spring can be increased, the strain energy and the natural frequency can be increased, and high speeds can be achieved.

If you look at it differently, it becomes something like this: That is, in the attraction portion of the plate spring 1, the magnetic flux φ flowing from the yoke 4 satisfies φ>2φ _l , where φ _l is the magnetic flux flowing from the plate spring 1 to the side yoke 11. on the other hand,
If the saturation magnetic flux density of the material is B _s and the area of the magnetic path is S, the relationship φ=B _s S holds, so if the width of the yoke 4 and the width of the leaf spring 1 are the same value b,
If the height of the suction part of the yoke 4 is h and the thickness of the leaf spring is t, then φ=B _s bh, φ _l =B _s th, and considering the relationship φ>2φ _l shown earlier, t<b/2, and the thickness of the leaf spring is yoke 4 and leaf spring 1.
It is sufficient that the width b is less than half of the width b. This leads to the effect that the weight of the leaf spring 1 is reduced, the natural frequency is increased, and the speed can be further increased.

In addition, in the above embodiment, in order to strengthen the structure, the part of the head of the side yoke 15, which was conventionally a free end, is integrated and fixed, but this is because the characters are printed using a dot line printer. To obtain a magnetic circuit that is stable against vibrations caused by holding a print head and swinging it laterally with respect to the paper by the width of a character when drawing. That is, when the side yoke 15 is fixed by the head, the side surfaces of the leaf spring 1 and the side yoke 15 can effectively face each other at the shortest distance when the leaf spring 1 is in the suction state, and the accuracy is ± at most. 0.05mm
It can be fixed within a certain range, and a magnetic circuit that is stable against vibration can be easily constructed. Although it is not necessary to integrate the heads of the side yokes, their fixation is extremely effective. If not fixed, the minute gap between the leaf spring 1 and the side yoke 15 will change with vibration, and the permeance in the magnetic circuit will also change, resulting in an unstable magnetic circuit. If this instability occurs, the printing force will decrease. This causes variations in the printing quality, resulting in a decrease in print quality. It may be possible to increase the thickness of the side yoke 15 instead of fixing it, but if this is done, the printing paper 10 and ink that will fit between the tip of the hammer pin 7 provided near the free end of the leaf spring 1 and the platen 8 can be considered. It becomes difficult to arrange the ribbons 9 closely together.
Taking these things into consideration, there is naturally a limit to the idea of increasing the thickness of the side yoke 15, and conventionally, it is common sense that the side yoke has a cantilever structure with one end free, which may inadvertently reduce the vibration. This meant that the structure was susceptible to influence. From this point of view as well, the present invention has the advantage of eliminating the conventional drawbacks, widening the range of design, and lowering costs.

Here, a specific example of the difference between the side yoke structure of the present invention and the conventional side yoke structure is as follows. For example, if we use a rare earth permanent magnet, we can change its shape to 5mm x 10mm x 2.
mm, the suction area at the tip of the yoke is 6 ^mm2 , and the leaf spring is 15 mm long, 0.7 mm thick, and 2 mm wide. ) is shown in FIG. 10. As can be seen by comparing the characteristic 19 of the conventional print head with side yokes and the characteristic 20 of the present invention in FIG. 10, the structure of the present invention has a smaller gap between the leaf spring and the yoke. As you can see, the suction force increases. In other words, if future technological trends include miniaturization, speeding up, and higher quality printing, it can be seen that the present invention will be extremely useful.

Although the present invention has been described above with a focus on the embodiment illustrated in FIG. 8, supplementary explanations will be given below regarding other embodiments of the present invention. FIG. 11 is a perspective view schematically showing one example with a portion cut away, and FIG. 12 is a schematic cross-sectional view thereof.

In this embodiment, the base 2, yoke 4, leaf spring 1, and side yoke 15 are reversed in the structure of the previous embodiment. In this type, the side yoke 1
In order to tension and fix the old free ends of the yoke 15, a groove is formed in the support plate 21, and the free end of the side yoke 15 is inserted into the groove and connected, and the support plate 21 is further fixed to the print head base 22. . Further, a housing 23 is attached to the print head base 22 so as to surround the yoke 4, the magnet 5, and the base 2. With this configuration, it is easy to arrange a plurality of printing hammers in parallel like in a line printer, and it is also easy to bend and fix the side yoke 15 in the suction direction of the leaf spring 1. Furthermore, the side yoke 15 can be easily attached and detached, and parts such as the leaf spring 1 and the coil 6 can be easily replaced.

The present invention has been explained based on the above two embodiments. In this article, we have given an example in which a plurality of side yokes 15 are integrated in order to simultaneously fix a plurality of former free ends of the side yokes, and the part where the leaf spring 1 comes out is made into a window shape. side yoke 11
Even in the case of a shape like this, it is possible to satisfy the basic structure of the present invention, and a certain effect can be achieved.

Furthermore, in the present invention, there is no particular need for the fixing plate used in each of the embodiments described above to fix the side yokes and leaf springs in an overlapping manner.
In particular, there are many means for fixing without using such a fixing plate, and these are effective in their own way. For example, as shown in the sectional view of the hammer portion in FIG. 13, the fixed ends of the leaf springs 1 may be fixed by overlapping side yokes 15, and the side yokes 15 may also serve as the fixing plate. Even in such a case, there is no problem with the means 21 for tensioning and fixing the free ends of the side yokes 15, and the effects of the present invention are reliably exhibited. That is, the leaf spring 1 and the yoke 4 are arranged so that the side surface of the leaf spring 1 and the side surface of the side yoke 15 face each other at the shortest distance near the suction part of the leaf spring 1 to form a stable magnetic path with sufficient margin. , lateral yoke 1
5, etc. can be directly connected and fixed.

As described above, according to the present invention, a printing head for an efficient spring charge type dot line printer capable of high-speed and stable printing can be obtained.

[Brief explanation of the drawing]

Fig. 1 is a schematic perspective view showing a conventional spring charge type line printer print head and its usage pattern, Fig. 2 is a schematic perspective view showing a print head with a conventional side yoke attached, and Fig. 3 is a schematic perspective view showing a print head with a conventional side yoke attached. Figure 2 is a partial perspective view showing the flow of magnetic flux by enlarging the area around the attraction part of the leaf spring, Figure 4 is an equivalent circuit of a conventional print head, and Figure 5 is an equivalent circuit of a head with a side yoke attached. , Fig. 6 is a schematic sectional view of a printing head with a conventional side yoke attached, Fig. 7 is an enlarged schematic sectional view of the vicinity of the suction suction of the leaf spring in Fig. 6, and Fig. 8 is a schematic sectional view of the printing head with a conventional side yoke attached. A partially cutaway perspective view showing the structural concept of a line printer using a print head according to an embodiment, FIG. 9 is a sectional view of FIG. 8, and FIG.
11 is a diagram showing an example of the relationship between the distance between the leaf spring and the yoke and the suction force for the conventional print head shown in the figure and the print head of the present invention shown in FIG. 6; FIG. The figure is a partially cutaway perspective view schematically showing another embodiment of the present invention, FIG. 12 is a sectional view of FIG. 11, and FIG. FIG. 7 is a schematic partial cross-sectional view showing another embodiment. Each symbol in the figure indicates the following. 1...
Leaf spring, 2... Base, 3... Fixed plate, 4... Yoke, 5... Permanent magnet, 6... Coil, 7... Hammer pin, 8... Platen, 9... Ink ribbon, 10... Paper , 11... conventional side yoke,
12... Magnetic flux flowing in the leaf spring, 13... Magnetic flux flowing in the side yoke, 14... Tip surface of the yoke, 15
... Side yoke of the present invention, 16 ... Support plate, 17
...Inner surface of the side yoke, 18...Spacer,
19...An example of the relationship between the distance between the leaf spring and the yoke of the print head using the conventional side yoke and the suction force, 20...The relationship between the leaf spring and the yoke of the print head using the side yoke of the present invention An example of the relationship between the distance and the suction force, 21... Support plate of another embodiment of the present invention,
22...print head base, 23...housing. φ _p ...Magnetic flux generated by the magnet, φ...Magnetic flux flowing to the attraction part of the leaf spring/yoke, φ _s ...Magnetic flux flowing to the leaf spring itself and when the leaf spring is saturated, P
_t ...Leakage permeance from the magnet to the leaf spring suction part, _Pg ...Permeance of the suction part between the leaf spring and yoke, _Ps ...Permeance when the leaf spring is saturated, _Pl ...Leakage between the leaf spring and the yoke Permeance between lateral yokes.

Claims (1)

[Scope of utility model registration request] The plate is attached to a hammer mechanism that uses strain energy generated in the plate spring as a printing energy source by attracting the vicinity of the free end of the cantilever plate spring to the yoke surface using a suction mechanism configured with a permanent magnet and a yoke. In a spring charge type dot line printer print head, in which side yokes are arranged on both sides of a spring, and a plurality of print hammers are arranged in parallel, each of which has a closed magnetic path formed by the permanent magnet, the yoke, the leaf spring, and the side yoke. , one end of the side yoke is fixed to one end of the yoke, and in a state where the free end of the leaf spring is attracted to the yoke, the attraction surface of the leaf spring and the leaf spring suction direction of the side yoke are A dot-type line printer print head characterized in that the free end of the side yoke head is bent in the suction direction of the leaf spring and fixed so that the side yoke head is effectively aligned with the surface of the print head.