JPH0137776Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention is a press device for plates for magnetic circuits that have a special shape that improves the so-called mold retention of the press device while saving the metal plate for the plate when forming by press working. Regarding.

For example, a speaker using an external magnet type magnetic circuit is
It is configured as shown in the figure. 1 shows the outer magnet type magnetic circuit as a whole, 2 is a disk-shaped back plate, 3 is an annular top plate, 4 is a center pole set approximately in the center of the back plate 2, and this and the top plate. A magnetic gap is formed between the two. Further, 5 is an annular magnet disposed facing the center pole 4 so as to surround it from the outside.

In addition, 7 is a frame, 8 is a voice coil, 9 is a damper, 10 is a cone paper, 11 is an edge, 12 is a dust cap, and 13 is a paper arrow.

Now, conventionally, the plates 2 and 3 are formed by a forging method in which metal plates such as steel plates, flat steel, steel strips, etc. are heated to a certain temperature and formed by applying pressure. The press machine is large and expensive, and even if it is produced in large quantities, the top plate 3 and back plate 2 have the disadvantage of high unit costs.

Therefore, it is considered that the back plate 2 and the top plate 3 are formed by a general press working method. According to this, since the press device is generally cheaper than the forging press device, the unit price is lower. However, on the other hand, it has the following drawbacks. That is, when forming the top plate 3 and back plate 2 by general press working, when the radius is R, it is possible to punch out the top plate 3 and back plate 2 as perfect circles as shown in FIG. can. However, in this case, much of the metal plate 14 after punching is wasted, and the metal plate 14 cannot be used effectively. Therefore, the unit costs of the back plate 2 and top plate 3 are also high.

Therefore, in order to avoid waste of the metal plate 14, the width W of the press material should be selected to be W≦2R (2R, 3/2R, 8/5R, etc.). The shape of the blade of the punch is plate 2,
It has the same shape as the metal plate after punching out 3.
Therefore, both ends of the press mold blade (Figs. 3 and 4)
Since the shaded area (in the diagram) is thinner, the blade tends to spill easily and has a disadvantage of having poor shape retention.

In view of these points, the present invention is to devise a press device for a plate of a special shape with improved mold retention while making effective use of metal plates.

Embodiments of the plate according to the present invention will be described in detail below with reference to FIGS. 5 to 7, and parts corresponding to those in FIGS. The redundant explanation will be omitted.

The plates pressed according to the present invention, that is, the back plate 2 and the top plate 3, are flat plates having a so-called barrel shape as a whole, as an example of which is shown in FIG.
A ridge portion 1 that is substantially orthogonal to the straight portions 15 and 16 at a corner where the curved portions 17 and 18 are close to each other.
9, 20, 21, and 22.

The example in the figure shows recesses 27 to 30 whose respective corners are L-shaped.
In the case where the curved portion 17,
Also on the 18 side is a ridge 23 parallel to the straight parts 15 and 16.
~26 are formed.

FIG. 6 shows the shape of the press mold and the metal plate 14 for forming the plate 2 or 3 described above. The distance W between the straight parts 15 and 16 of the plates 2 and 3 is the width of the metal plate 14, which is the same as the width of the curved parts 17 and 18.
This is the case where the radius R is selected to be 8/5 times. When the shape of the die is selected to be the shape of the plate 2 or 3, the shape of the plate 2 or 3 is equal to the shape of the metal plate 14 after punching. Therefore, the shape of the die blade is a convex shape where both ends thereof abut against the recesses 27 to 30 as shown in the figure, and both ends have a predetermined thickness without becoming thin.

The back plate 2 and the top plate 3 generally have a through hole 35 for mounting the center pole 4 (a hole for a magnetic gap in the top plate 3) and a fixing rod (for fixing the annular magnet 5) as shown in FIG. Since small insertion holes 31 to 34 (not shown) are formed, the shape of the press die, especially the shape of the die blade, is slightly different from that in FIG. 6.

FIG. 8 shows another example of the back plate 2 and top plate 3. In this example, the corners are the convex portions 36 to 36.
38, and even in this case, the ridges 19 to 22 are selected to be substantially perpendicular to the straight portions 15 and 16. In addition, the corner part is the convex part 3
When the number is 6 to 39, the shape of one blade of the press mold becomes as shown in FIG. 9, so the thickness of both ends of the blade can be increased. Note that the embodiment shown in this figure is particularly suitable for application to a tweeter speaker.

FIG. 10 shows still another example of the back plate 2 and top plate 3. In this example, straight portions 40 and 41 are also formed in the curved portions 17 and 18 along the width direction of the flat bar 14. In this case, the width of the back plate 2 and the top plate 3 is 1.7 to 1.8R. The above have been selected.

Figures 11 to 13 are cross-sectional views of yokes constructed by attaching the center pole 4 to the back plate 2 of the various examples described above, and the center pole 4 may be formed of a round bar or thick-walled pipe. It is attached near the through hole 35 of the back plate 2 by gluing, caulking, or welding.

By the way, since the back plate 2 or the top plate 3 described above has the ridges 19 to 22 orthogonal to the straight parts 15 and 16, the recesses 27 to 30 or the convex parts 36 to 39 are formed. If the magnetic circuit is configured without intersecting the top plate 3 and the top plate 3, there is a drawback that magnetic flux leaks at the recesses 27 to 30 or the projections 36 to 39 of the back plate 2 and top plate 33.

Therefore, the back plate 2 shown in FIG.
By arranging the top plate 3 and the top plate 3 orthogonally to each other to form a magnetic circuit as shown in FIG. 14, leakage of magnetic flux can be suppressed as much as possible.

Thus, according to the present invention, a ridge is formed at a corner where a straight part and a curved part of a barrel-shaped flat plate are close to each other, so that the ridge part is substantially perpendicular to the straight part, so that the plate material can be saved while saving plate material. In this case, since the press mold, that is, the edge at the corner where the arc portion and the straight portion intersect at both ends of the die blade can be made strong, the mold retention can be improved.

Furthermore, when the back plate, top plate and center pole pressed by the press device of the present invention are assembled so as to intersect with each other by 90 degrees as shown in FIG. 14, leakage of magnetic flux can be suppressed as much as possible.

In addition, since the plate and the speaker can be manufactured at low cost since the plate is formed by general press molding without using forging.

[Brief explanation of drawings]

Fig. 1 is a sectional view of a speaker using an external magnet type magnetic circuit, Figs. 2 to 4 are plan views for explaining conventional press forming of a plate, and Fig. 5 is a sectional view of a speaker using an external magnetic circuit. FIG. 6 is a plan view for explaining press forming of a plate using the press device of the present invention, FIG. 7 is a plan view of the plate after press forming, and FIG. 8 is a plan view of another example of the basic shape of the present invention. FIG. 9 is a plan view of the mold of the example shown in FIG. 8, FIG. 10 is a plan view of still another example of the present invention, and FIGS. 11 to 13 are various examples of the present invention. FIG. 14 is a cross-sectional view of a yoke to which the present invention is applied, and FIG. 14 is a plan view of a magnetic circuit constructed by combining plates formed by the press apparatus of the present invention. 2 and 3 are plates, 15 and 16 are straight parts, 1
7 and 18 are curved portions, and 19 to 22 are ridge portions.

Claims (1)

[Claims for Utility Model Registration] A magnetic circuit plate having a shape surrounded by a pair of opposing linear sides and a pair of arcuate sides of the metal plate is punched out of a band-shaped metal plate. In the press device, a ridge portion substantially orthogonal to the pair of straight sides is provided at least at a portion where the pair of straight sides and the pair of arcuate sides intersect, respectively, of one blade of the mold. A press device characterized by: