JPH0352075Y2 - - Google Patents

Description

[Detailed description of the invention] ``Purpose of the invention'' (Industrial application field) The present invention relates to magnetic circuit units such as speakers and microphones, and is particularly concerned with simplifying assembly and ensuring uniformity of the magnetic gap. Concerning what has been made possible.

(Prior art) In a conventional general external magnet type magnetic circuit unit, the yoke, magnet, and top plate are fixed with adhesive, and the magnetic gap is formed by fitting a jig to the center pole during assembly. Together, they ensure a gap.

This conventional construction method has drawbacks such as the need for adhesive curing time, the need for a large number of jigs, and the inability to ensure an accurately uniform magnetic gap due to the provision of a certain clearance for the jigs. be.

In order to eliminate the above-mentioned drawbacks, as shown in FIG.
When the yoke 21, the magnet 23, and the top plate 24 are press-fitted, the magnetic gap 25 is secured by engaging the engaging flange portion 24a with the outer peripheral surface of the center pole 22, and the yoke 21, magnet 23, and top plate 24 are secured without using adhesive. A device in which each part is fixed in its entirety has also been proposed.

(Problems to be Solved by the Invention) In the device shown in FIG. 3, it is necessary to make the engaging flange portion 24a as thin as possible in order to improve the magnetic properties of the magnetic gap, and therefore the mechanical strength is insufficient. This has disadvantages such as deformation during press-fitting, inability to maintain a predetermined uniform magnetic gap, and the need to use adhesive due to insufficient overall bonding strength. Furthermore, there is a drawback that the cost increases in order to ensure the dimensional accuracy of the inner circumference of the engaging flange portion 24a.

The purpose of this invention is to eliminate the above-mentioned conventional drawbacks,
To provide a magnetic circuit unit which is easy to assemble, can secure a predetermined magnetic gap by press-fitting a top plate, and can maintain uniformity of the magnetic gap. It is in.

"Structure of the invention" (Means for solving the problems) The magnetic circuit unit according to the invention has a large diameter portion formed on the lower outer periphery of the center pole than the part where the magnetic gap is to be formed, and the top plate. A plurality of dowels are protruded on the lower surface of the inner circumferential side in a circumferential manner on a concentric circle with the inner diameter of the top plate, and when the top plate is press-fitted, the dowels are fitted to the upper edge of the large diameter portion of the center pole. When the two engage with each other, a magnetic gap is formed and held.

(Function) When assembling the magnetic circuit unit, when the magnet is placed on the yoke and the top plate is press-fitted, the dowels protruding from the lower surface of the inner circumferential side of the top plate are connected to the large diameter part formed on the center pole. The magnetic gap is engaged with the upper edge of the magnetic gap, thereby forming a uniform magnetic gap and holding the magnetic gap, thereby making it possible to firmly connect and fix the entire magnetic gap.

Incidentally, since the center pole and the top plate can be formed by forging, it is easy to form a large diameter portion on the center pole and a dowel on the top plate.

(Example) The first example of the magnetic circuit unit according to the present invention is as follows.
The explanation will be made based on FIGS. 1 and 2, in which FIG. 1 is a sectional view and FIG. 2 is a back view of the top plate.

In the figure, 1 is a yoke, 2 is a center pole, 3 is a magnet, and 4 is a top plate.
is formed.

In the present invention, the magnetic gap 5 of the center pole 2 is lower than the portion 2a where the magnetic gap 5 is formed.
A large diameter portion 6 is formed on the outer periphery of the top plate 4, and a large diameter portion 6 is formed on the lower surface of the inner periphery of the top plate 4.
A plurality of dowels 7 are protruded in a frequency-divided manner on a concentric circle with a,
By press-fitting the top plate 4, the dowel 7 is attached to the upper edge 6 of the large diameter portion 6 of the center pole 2.
It is constructed so that the magnetic gap 5 is formed and held while the two are engaged with each other by fitting into the magnetic gap 5a.

The dowels 7 can be formed on the top plate 4 during forging of the top plate, but
It can also be formed by embossing from the top surface side, and in the figure, 7a indicates the recessed portion at the time of embossing. In short, a plurality of these dowels 7 may be formed at the frequency division positions, and the number is not limited to the illustrated example.

"Effects of the invention" According to the magnetic circuit unit according to the invention, when assembling the magnet, when the magnet is placed on the yoke and the top plate is press-fitted, the dowels formed on the lower surface of the inner circumferential side of the top plate can be assembled. engages with the upper edge of the large diameter portion formed on the center pole, thereby forming a uniform magnetic gap and holding the magnetic gap properly.

Since the upper edge of the large diameter part of the center pole and the top plate are engaged with each other through the dowel portion, mechanical strength can be increased, and dimensional accuracy is also improved, resulting in a highly reliable magnetic circuit unit. be able to. Moreover, since the top plate is press-fitted, the entire structure can be firmly connected and fixed, and there is no need for a bonding process using an adhesive, resulting in cost reduction.

[Brief explanation of the drawing]

1 and 2 show an embodiment of the magnetic circuit unit according to the present invention, with FIG. 1 being a sectional view and FIG. 2 being a back view of the top plate. FIG. 3 is a sectional view showing an example of a conventional top plate fitting type magnetic circuit unit. 1: Yoke, 2: Center pole, 3: Magnet, 4: Top plate, 5: Magnetic gap,
6: Large diameter portion, 6a: Upper edge of large diameter portion, 7: Dowel.

Claims (1)

[Scope of utility model registration request] A larger diameter part is formed on the lower outer periphery than the part where the magnetic gap of the center pole is to be formed, and a plurality of dowels are formed on the lower surface of the inner periphery of the top plate in a diagonal manner on a concentric circle with the inner diameter of the top plate. A magnetic circuit unit characterized in that the dowel engages with the upper edge of the large diameter portion of the center pole by press-fitting the top plate to form and hold a magnetic gap.