JPH0528182B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electromagnetic drive device for printing elements in an impact type dot matrix printer.

[Prior Art] As a conventional electromagnetic drive device for a printing element, for example, as disclosed in Japanese Patent Application Laid-open No. 55-154178, a drive device mounted on a circular yoke plate fixed to the rear end surface of a cylindrical permanent magnet is used. In this case, a plurality of cores around which drive coils were wound were vertically protruded, and each core was configured to face the drive arm of the printing element.

[Problems to be Solved by the Invention] According to the configuration of this known electromagnetic drive device, there is a problem in that it takes time and effort to attach each core to the yoke, and the assembly workability is poor.

In addition, the drive coil is placed in a sealed space, so the heat generated by the drive coil during printing is trapped in the sealed space.
This has the disadvantage that the printing head tends to overheat. This becomes a particularly serious problem when high-speed printing is desired.

SUMMARY OF THE INVENTION An object of the present invention is to provide an electromagnetic drive device for a printing element that is easy to assemble and can efficiently dissipate heat generated by a drive coil.

[Means for Solving the Problems] In the electromagnetic drive device for a printing element according to the present invention, a plurality of drive arms for driving the printing element are arranged radially, and a plurality of U-shaped cores facing the drive arms are arranged in a radial manner. The pieces are radially positioned at predetermined ventilation gaps in correspondence with the arrangement of the drive arm, and each core piece is integrally molded and is attached to the tip of each leg piece on the outside of each core piece. A core body is constituted by integrally molding annular body parts connecting the tips of the respective leg pieces and having a ventilation gap at the rear part between adjacent core pieces, and the core body has inner legs of each core piece. A drive coil for excitation is attached to the piece, and a donut-shaped permanent magnet is provided on the front of the ring body, and a rear ventilation gap between adjacent core pieces is provided outside the core body. As you can see, it is characterized by the fact that it is covered with heat dissipation fins.

[Function] According to the configuration of the present invention, the U-shaped core pieces located radially in correspondence with the arrangement form of the drive arm are integrally molded with a predetermined gap that allows ventilation, and the core pieces of each core piece are integrally formed. A core body is constructed in which a ring body connecting the tips of each of the outer leg pieces is integrally molded at the tip of each of the outer leg pieces, and has a ventilation gap at the rear between adjacent core pieces, and Heat dissipation fins are placed on the outside of the core body so that the ventilation gaps at the rear between the core pieces are exposed to the outside, so there is no need to assemble each core piece, and assembly is easy. The heat generated can be efficiently dissipated to the outside through the rear gap between the core pieces and the heat dissipation fins.

[Example] Hereinafter, a preferred example of the present invention will be described with reference to the drawings.

The print head of this embodiment is broadly divided into a print wire assembly, a drive arm assembly, a core assembly, and a coil assembly.

First, the printing wire assembly will be explained.

In FIG. 1, wire guides 3, 4, and 5 are fixed to a hollow portion 2 of a head frame 1 made of plastic.
A plurality of (nine in this embodiment) printing wires 7 are slidably supported by the print wires 5 to 5 and the wall portion 6 of the head frame 1. A printing pin 8 is fixed to the rear end of each printing wire 7, and a return spring 9 inserted between the printing pin 8 and the wall 6 causes each printing wire 7 to move backward (see FIG. 1). right side).

Next, the drive arm assembly located behind the print wire assembly will be described.

In FIG. 1, the drive arm assembly includes a stopper plate 10, a drive arm 11, and a spacer 12.
and a yoke plate 13, which are fixed in a stacked manner with screws 14. The stopper plate 10, drive arm 11 and spacer 12 are made of non-magnetic material, and the yoke plate 13 is made of magnetic material.
The drive arm assembly integrated through screws 14 is connected to the back surface of head frame 1 through screws 15 screwed into stopper plate 10. Note that the drive arm 11 and the spacer ring 12 may be made of a magnetic material.

The drive arms 11 of this embodiment are arranged radially at equal angular intervals as shown in the second figure, and are connected together at their respective rear ends. A hole 11a is formed in the middle of the drive arm 11, and a movable yoke 11b made of a magnetic material is fixed to the hole 11a with an adhesive or the like as shown in the first figure. The distance between the drive arm 11 and the yoke puto 13 is determined to be a desired distance depending on the thickness of the spacer 12. The yoke plate 13 has a third
As shown in the figure, a through hole 13a and a center hole 13b are bored, and a movable yoke 11b shown in the first figure is movably passed through the through hole 13a. The stopper plate 10 has substantially the same shape as the yoke plate 13 shown in the third figure.

Next, the core assembly located behind this drive arm assembly will be explained.

As shown in FIGS. 1, 4, 5, and 6, the core assembly includes a magnet plate 14 made of a magnetic material, a permanent magnet 15, and a core body made of a magnetic material. 16, which are integrally bonded to each other via an adhesive. The thus integrated core assembly is connected to the aforementioned drive arm assembly by screws 18 with a ring-shaped spacer 17 interposed therebetween. That is, the screw 18 passes through the drive arm assembly and the spacer 17 and attaches to the magnetic plate 14.
It is screwed on. The magnetic plate 14 and the permanent magnet 15 have a ring shape, and the core body 16 has a plurality of magnets arranged radially symmetrically to the arrangement of the drive arms 11 shown in the second figure at predetermined intervals to allow ventilation. It is a collection of U-shaped core pieces 16a. That is, each core piece 16a is integrally molded, and an annular body part 16b that connects the tip of each leg piece on the outside of each core piece 16a is integrally molded, so that the adjacent core As shown in FIG. 6, the core body 16 has a ventilation gap 16c at the rear between the pieces 16a. A movable yoke 11b faces the tip of each leg on the inner side of each core piece 16a, and a permanent magnet 15 is provided on the front surface of the ring portion 16b.

Note that the magnet plate 14 in the coil assembly may be omitted in some cases. In this case, the outer legs of each core piece 16a will be correspondingly longer.

Next, the coil assembly will be explained.

The coil assembly includes a drive coil 19 and a coil terminal plate 20 that holds the drive coil 19. This coil assembly is attached to the core body 16 from the front so that each drive coil 19 surrounds the inner leg of each core piece 16a as shown in the first figure.

As shown in FIGS. 7 and 8, the coil terminal plate 20 includes a ring-shaped portion 20a located at the center, a plurality of rim portions 20b extending radially from the ring-shaped portion, and a rear portion of each rim portion. It consists of a peripheral wall portion 20c that integrally connects the end portions. The rim portion 20b is located at a position corresponding to the gap between the core pieces 16a shown in the fourth figure. Each drive coil 19 is fixed to two adjacent rim portions 20b via an adhesive so as to straddle them. A terminal pin 21 is implanted on the back surface of the terminal board 20, and the end of the drive coil 19 is connected to this terminal pin. A locking portion 2 is provided at the inner peripheral edge of the through hole 20d of the ring-shaped portion 20a.
0e is formed at three locations. The locking portion 20e is
As shown in the first figure, a holder 23 holding a temperature sensor 22 is attached.

Next, the structure of the holder 23 will be explained with reference to FIGS. 10 and 11.

The holder 23 has a shaft-shaped holding part 23a in the center, and three legs 2 from the lower part of the holding part 23a.
3b is formed to extend outward. A recess 23c in which the sensor 22 is installed is formed on the upper end surface of the holding portion 23a, and a recess 23c in which the sensor 22 is installed is formed on the outer peripheral surface.
A groove 23d for passing the second lead wire is formed. The groove 23d passes through the leg portion 23b. Further, each leg portion 23b has an elastically deformable locking claw 23e vertically protruding from the leg portion 23b. This holder 23 can be attached to the terminal board 20 from the back side thereof. Therefore, the temperature sensor 22 is attached to the terminal board 20 in the final stage of print head assembly with it attached to the holder 23.
It can be assembled as shown.

As shown in FIG. 1, the printing head constructed in this manner has a flexible cable 24 attached to its back surface and a heat dissipating fin 25 covering its outer periphery. A flexible cable 24 connects the print head to a control circuit (not shown).
The terminal pin 21 of the terminal board 20 and the lead wire of the temperature sensor 23 are connected to the terminal pin 21 of the terminal board 20. The heat dissipation fin 25 is the core piece 1
The gap 16c between the core body 16 and the gap 16c is located at the outer periphery of the core body 16 so as to be exposed to the outside.

In the print head configured as above,
When not printing, the movable yoke 11b is attracted to the core piece 16 via the magnetic flux of the permanent magnet 15, and the drive arm 11 is in a retreated position as shown in the first figure against its own elastic force. When the drive coil 19 is energized, the magnetic flux of the permanent magnet 15 is canceled out, thereby releasing the magnetic attraction of the movable yoke 11b to the core piece 16. Then the drive arm 11
moves forward by its own elastic force, moves the print wire forward against the spring force of the return spring 9, and a dot is formed on the print medium (not shown).

[Effects of the Invention] According to the present invention described in detail above, each U-shaped core piece is integrally formed and positioned radially in correspondence with the arrangement form of the drive arm with a predetermined gap that allows ventilation. and a core body having an annular body part connecting the tips of each leg piece on the outside of each core piece integrally formed therein, and having a ventilation gap at the rear part between adjacent core pieces. , and the heat dissipation fins are placed on the outside of the core body so that the rear ventilation gap between the core pieces is exposed to the outside, so there is no need to assemble each core piece, making assembly easy. In addition, the heat generated by the coil can be efficiently dissipated to the outside through the gap between the core pieces and the heat dissipation fin, and the print head will not overheat.This improves assembly work efficiency and improves printing efficiency. The durability of the head is improved and stable high-speed drive is possible.

Note that the present invention can be applied to devices other than the spring release type of the above embodiment.

[Brief explanation of the drawing]

The drawings show a preferred embodiment of the present invention, in which FIG. 1 is a vertical sectional view showing the internal structure of the print head with some parts omitted, FIG. 2 is a front view of the drive arm, and FIG. is a front view of the yoke plate, Figure 4 is a front view of the core assembly, Figure 5 is a rear view of the core assembly, Figure 6 is a partially sectional side view of the core assembly, and Figure 7 is a side view of the coil assembly. 8 is a rear view of the coil assembly, FIG. 9 is a sectional view taken along the line A-A in FIG. 8, FIG. 10 is a front view of the temperature sensor holder, and FIG. 11 is a B-B in FIG. FIG. 11... Drive arm, 11b... Movable yoke,
15... Permanent magnet, 16... Core body, 16a...
... Core piece, 16b ... Annular body part, 16c ... Gap, 19 ... Drive coil.

Claims (1)

[Scope of Claims] 1. A plurality of drive arms for driving the printing element are arranged radially, and a plurality of U-shaped core pieces facing the drive arms are spaced apart from each other by a predetermined gap that allows ventilation to drive the printing element. A ring is positioned radially in accordance with the arrangement of the arms, is integrally molded with each of the core pieces, and connects the tip of each of the leg pieces on the outside of each of the core pieces. A core body is constructed in which the body is integrally molded and has a ventilation gap at the rear between adjacent core pieces, and the core body has a drive coil for excitation in the inner leg piece of each core piece. A donut-shaped permanent magnet is provided on the front surface of the ring body, and a heat dissipation fin is placed on the outside of the core body so that the gap is exposed to the outside. Electromagnetic drive of elements. 2. The electromagnetic drive device for a printing element according to claim 1, wherein the drive arm has a movable yoke at a position facing the inner leg piece of the core piece.