JPS6239256A - Printing head - Google Patents

Abstract

PURPOSE:To conduct an uniform printing, by a construction wherein pieces of permanent magnet of arc shape are disposed annular by to form a permanent magnet of annular shape. CONSTITUTION:An armature 23 is magnetically attracted to an attracting surface 24 of a yoke piece 11 by a permanent magnet 18 against the force of a plate spring 28. The printing signal sent from the control circuit formed on a printing board 31 energizes a specified coil 26, thus resulting in the excited yoke piece 11. At the excited yoke piece 11, the force of the permanent magnet 18 is cancelled, whereby the armature 23 if released from the attracting surface 24 by the spring force of the plate spring 28. As a result, a printing wire 7 projects out from a nose portion 3 at the tip end thereof to conduct printing. Two pieces of arc permanent magnet 18a are disposed annularly with a small gap therebetween to form the permanent magnet 18 of annular shape as a whole, which eliminates a large ring eddy current Y while retaining a partial eddy current X. In this manner, the resulting reduction in occurrence of the eddy current prevents the delay of printing action, which enables a high-speed printing to be conducted.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a print head for a printer that performs dot printing by controlling a printing member with an electromagnet.

[Background technology]

Until now, printers that perform dot printing using electromagnetic control have been equipped with a large number of electromagnets that generate electromagnetic force to cancel out the magnetic force of the permanent magnets that attract the printing member hammer, and permanent magnets with the same number of magnets as these. was. In such a structure, the assembly process becomes complicated, leading to an increase in production costs.

As a means to solve this problem, a method was devised in which a permanent magnet was made into a ring shape and shared by all electromagnets. However, as shown in Figure 8, in such a permanent magnet, in addition to the eddy current (X) generated in local parts of the annular magnet due to the magnetic flux (Z) passing through the permanent magnet, there is also an eddy current (X) in the circumferential direction. Eddy current (Y
) occurs.

Because of these eddy currents (X) and (Y), it takes time to excite the coil and cancel the magnetic force of the permanent magnet.
Conversely, after the coil is demagnetized, it takes time for the magnetic force of the permanent magnet to recover. As a result, the printing operation becomes slow and the high-speed printing function is hindered. In addition, the above eddy current (Y) generates magnetic flux in a direction that prevents the excitation of the coils of other electromagnets, so there is a difference between operating one electromagnet and operating multiple electromagnets at the same time. There was also the problem of uneven printing.

[Purpose of the invention]

This invention takes advantage of the advantages of the annular permanent magnet, while
The purpose of the present invention is to reduce eddy current (Y) generated in a permanent magnet and provide a print head with little variation (which performs a high-speed printing operation).

[Disclosure of the invention]

In order to achieve the above object, the present invention includes a group of attraction surfaces arranged in a ring in a number corresponding to the number of dots, an annular permanent magnet that exerts magnetic force on each attraction surface, and a magnetic force of the permanent magnet that exerts magnetic force on each attraction surface. A group of electromagnets that cancel each attraction surface, a group of printing members corresponding to the number of dots extending in the center of a ring formed by the attraction surface in a direction perpendicular to the surface containing this ring, and a group of printing members corresponding to the number of dots at the tip of each printing member. Each of the printing members includes a plate spring that always urges the printing member in the direction in which the printing member protrudes, and an armature that makes each printing member stick to the suction surface against the urging of the leaf spring, and each of the printing members has the following: Printing for dot printers in which the dot normally moves toward the attracting surface due to the magnetic force of the permanent magnet, or when the magnetic force of the permanent magnet is canceled by the electromagnet, its tip protrudes due to the spring force of the leaf spring and forms a dot. The gist of the print head is that the annular permanent magnet is constituted by arc-shaped permanent magnet pieces arranged in an annular manner.

This will be explained in detail below with reference to the accompanying drawings.

FIG. 1 shows the appearance of a print head according to the present invention. As shown in the figure, this print head 1 has a nose portion 3 protruding from the front surface of a cylindrical housing 2 having a fitting structure, and print wires (not shown), which are printing members, inserted through a number of holes 10 formed in the front surface of the nose portion 3. The tip of the (omitted) protrudes to form a dot.

FIG. 2 shows a cross-sectional structure of the left half of the print head 1 shown in FIG. 1, excluding the housing 2 and nose portion 3. As shown in FIG. FIG. 3 shows an exploded view of the print head according to the present invention including the nose portion, with some parts omitted to avoid complexity.

As shown in FIG. 3, suction surfaces 24 whose number corresponds to the number of printed dots are arranged in a ring. Each suction surface 24 is formed by an end surface of the yoke 11, which will be described in detail below. As seen in detail in FIG. 2, the yoke piece 11 is
It includes a pair of legs 12, 13 and their connecting part 14, has a U-shaped side cross section, and has a radially inner leg 1.
The end face of 2 serves as the suction surface 24. In this embodiment, each yoke piece 11 is prepared as a ring-shaped material 40 that is connected together by a connecting piece 39.
After being fitted and fixed to the base plate 15 as described below, the connecting piece 39 is cut and removed along the two-dot chain line 41 in FIG. It is U-shaped as shown by the solid line in Figure 4.

In FIG. 4, the dashed-dotted line indicates the portion to be excised. In this way, when each yoke piece is independent, the magnetic flux generated in each yoke piece 11 is prevented from adversely affecting other yoke pieces 11 when electromagnetic force is generated, which will be described later. However, the yoke pieces may be connected as a whole into one piece like the yoke piece blank 40 in FIG.

A base plate 15 (see FIG. 5) made of a non-magnetic material such as aluminum is located near the connecting portion 14 of the yoke piece 11.
It is fixed by caulking or other methods. That is, the base plate 15 is provided with mounting holes 16 corresponding to the yoke pieces 11, and as shown in FIG. 11 is fixed to the base plate 15.

As shown in FIG. 2, a flat annular permanent magnet 18 is attached to the mounting surface 17 of the leg portion 13 on the radially outer side of the yoke piece 11.
Next, a magnetic flux collecting plate 19 made of a ferromagnetic material and formed into a flat annular shape is fixed with an adhesive or the like, and an auxiliary yoke 21, 21 is disposed thereon.

As shown in FIGS. 2 and 4, a coil 26 is wound around each leg 12 to form an electromagnet group. The permanent magnet 18 is magnetized in the direction in which the leg portion 13 extends, that is, in the vertical direction in FIG.

The print hammer of this print head is constructed as follows. That is, as shown in FIG. 2, a leaf spring 28 is attached to the top of the auxiliary yoke 21.21 via a spring fixing plate 20.20. An armature 23 is fixed to a spring portion 29 of a temporary spring 28 corresponding to each printing wire 7 by means of an eye contact or the like. On the other hand, the arm member 32 fixed to the armature has through holes spaced apart in its longitudinal direction to reduce weight and contribute to high-speed printing. The mounting portion 30 of the leaf spring 28 is sandwiched between the spring fixing plates 20.20. The bolts 34 are inserted through each bolt insertion hole of the front base 27, the spring fixing plate 20, 20, and the leaf spring 28, and are inserted into the auxiliary yoke 21.
．． It is screwed into an internal threaded hole 25 formed in the annular portion of 21.

In the auxiliary yoke 21, an armature 23 is disposed in a notch 22 (FIG. 3) that is formed protruding from the inside of the annular portion at intervals in the circumferential direction, as shown in FIG. As a result, the armature 23 faces the suction surface 24 of the leg portion 12 on the radially inner side of the yoke piece 11.

The number of printing wires 7 corresponding to the number of printing dots is prepared, and as shown in FIGS. 8, 9, and 10 in order, the tip thereof is positioned toward a predetermined hitting position. The lower member 3b is fitted into the upper member 3a.

The print head according to the present invention is constructed as described above, and the armature 23 is normally moved against the force of the leaf spring 18 by the magnetic force of the permanent magnet 18 to move the yoke piece 1.
It is attracted to the attraction surface 24 of No. 1. Therefore, the printing wire 7 connected to the armature 23 is in a state closer to the permanent magnet side. On the other hand, when a dot signal is issued from the control circuit formed on the printed circuit board 31, the single or plural coils 26 instructed by this signal are excited, so that in this excited yoke piece 11, the permanent magnet 18 is The magnetic force is canceled and the armature 23 is released from the attraction surface 24 by the spring force of the leaf spring 28. by this,
The tip of the printing wire 7 protrudes from the nose portion 3 and performs a dotting operation. Note that here, when we say that the magnetic force of the permanent magnet is canceled out, we only mean complete cancellation.
In short, this includes the case where the magnetic force of the permanent magnet is twisted to such an extent that the force of the leaf spring can act.

As shown in Figure 3, the permanent magnet consists of an arc-shaped permanent magnet piece 1
By arranging two pieces 8a in an annular shape with a slight gap between them, the overall structure is annular. Since this permanent magnet 18 has such a divided structure, as shown in FIG. 5, even if a local eddy current (X) occurs, a large annular eddy current (Y) completely disappears.

Since eddy currents are reduced compared to conventional integral annular permanent magnets, delays in printing operations are prevented, and as a result, high-speed printing can be achieved.

In FIG. 3, the permanent magnet 18 is composed of two pieces, but in other configurations, for example, for a 24-dot printer, it may be made up of 3, 4, or 6 pieces. That is, it is conceivable to divide the number of dots into equally divisible numbers (common divisors). This is because the number of pieces necessary to make the ring will have the same shape and size, which is preferable in terms of manufacturing, performance, etc. However, the number of divisions is not limited to such equal division. Each arc-shaped permanent magnet piece 18a may be obtained by dividing a single ring-shaped piece, or may be made into an arc-shaped piece from the beginning. In any case, the production process is simple and does not significantly increase production costs.

Note that instead of configuring the permanent magnet 18 with a plurality of pieces, a third
The magnetic flux collecting plate 19 shown in the figure may be composed of a plurality of pieces. That is, in this case, the magnetic flux collecting plate 19 can also be regarded as a type of annular permanent magnet.

〔Effect of the invention〕

Since the print head according to the present invention has the above-described structure, the speed at which the magnetic force of the permanent magnet is canceled out and the speed at which the magnetic force of the permanent magnet is restored are both fast (as a result, the printing speed is significantly increased).

Further, since no magnetic flux is generated in a direction that interferes with the excitation of the electromagnetic coil, the printing condition is stabilized.

[Brief explanation of the drawing]

Fig. 1 is a perspective view showing the external appearance of a print head according to the present invention, Fig. 2 is a sectional view of the left half of the above print head excluding the housing portion and nose portion, and Fig. 3 is a sectional view including the nose portion. An exploded perspective view of the same print head as above, FIG. 4 is a partially enlarged perspective view showing the state in which the coils are fitted into the legs of the yoke piece, FIG. 5 is a plan view of the base plate, and FIG. 6 is a perspective view of the yoke. 5 is a sectional view of the permanent magnet fixed to the base plate as seen from section line I-1 in FIG. 5, FIG. 7 is a conceptual diagram showing eddy currents generated in the permanent magnet according to the present invention, and FIG. FIG. 3 is a conceptual diagram showing eddy currents generated in a magnet. 1...Print head 7...Print wire 11...
Yoke piece 18... Permanent magnet 18a... Arc-shaped permanent magnet piece 23... Armature 24... Attraction surface
26... Coil 28... Leaf spring

Claims (4)

[Claims] (1) A group of attraction surfaces arranged in a ring in a number corresponding to the number of dots, an annular permanent magnet that exerts magnetic force on each attraction surface, and a group of electromagnets that cancels out the magnetic force of the permanent magnets that exerts on each attraction surface for each attraction surface. and a group of printing members corresponding to the number of dots extending in a direction perpendicular to the surface including the ring at the center of the ring formed by the suction surface, and each printing member is always urged in a direction in which its tip protrudes. and an armature for attracting each printing member to the attraction surface against the urging force of the leaf spring, and each printing member is normally attached to the attraction surface by the magnetic force of a permanent magnet. However, when the magnetic force of the permanent magnet is canceled by the electromagnet, the tip of the print head protrudes due to the spring force of the leaf spring and forms a dot. A print head characterized in that the magnet is constituted by arc-shaped permanent magnet pieces arranged in an annular shape. (2) The print head according to claim 1, wherein the suction surface is an end face of each radially inward leg of a U-shaped yoke piece arranged annularly in a number corresponding to the number of dots. (3) The print head according to claim 1 or 2, wherein the arc-shaped permanent magnet pieces are provided in a number that can evenly divide the number of dots. (4) Claim 1 in which the printing member is a printing wire
The print head according to any one of Items 1 to 3.