DIAPHRAGM AND ELECTROACOUSTIC TRANSDUCER
A diaphragm including at least a first portion, a second portion, and a third portion that are arranged around a predetermined reference axis extending in a vibration direction, and each have a different cross-sectional shape along a plane that includes the reference axis, in which the cross-sectional shape of the first portion is an arc having a first radius of curvature, the cross-sectional shape of the second portion is an arc having a second radius of curvature different from the first radius of curvature, and the cross-sectional shape of the third portion is a part of an ellipse.
1 . A diaphragm provided in an electroacoustic transducer, the diaphragm comprising at least:
a first portion, a second portion, and a third portion that are arranged around a predetermined reference axis extending in a vibration direction, and each have a different cross-sectional shape along a plane that includes the predetermined reference axis,
wherein the cross-sectional shape of the first portion is an arc having a first radius of curvature,
the cross-sectional shape of the second portion is an arc having a second radius of curvature different from the first radius of curvature, and
the cross-sectional shape of the third portion is a part of an ellipse.
2 . The diaphragm according to claim 1 , further comprising:
a fourth portion arranged in a circumferential direction with the first portion, the second portion, and the third portion,
wherein a cross-sectional shape of the fourth portion is a part of an ellipse.
3 . The diaphragm according to claim 2 ,
wherein the cross-sectional shape of the third portion and the cross-sectional shape of the fourth portion are different.
4 . The diaphragm according to claim 1 , further comprising:
a connecting portion that continuously connects at least one of the following:
the first portion and the third portion; or
the second portion and the third portion.
5 . The diaphragm according to claim 4 ,
wherein in a plan view, boundary lines of at least one of the following pairs are arranged in parallel:
a boundary line between the connecting portion and the first portion, and a boundary line between the connecting portion and the third portion; or
a boundary line between the connecting portion and the second portion, and a boundary line between the connecting portion and the third portion.
6 . The diaphragm according to claim 1 , further comprising:
a neck portion connected to a voice coil,
wherein a thickness at a boundary of the neck portion with the first portion is different from a thickness at a boundary of the neck portion with the third portion.
7 . The diaphragm according to claim 1 ,
wherein a thickness at an outer peripheral edge portion of the third portion is greater than a thickness at an outer peripheral edge portion of the first portion.
8 . The diaphragm according to claim 1 ,
wherein the diaphragm includes paper made from a material that contains at least one of chemical fiber or pulp.
9 . The diaphragm according to claim 1 ,
wherein the diaphragm includes injection-molded resin.
10 . The diaphragm according to claim 1 ,
wherein the diaphragm includes a press-molded sheet- or film-shaped material.
11 . The diaphragm according to claim 1 , comprising:
a neck portion that surrounds the predetermined reference axis extending in the vibration direction; and
at least the first portion, the second portion, and the third portion outside the neck portion,
wherein a cross-sectional shape of the neck portion, along any plane including the predetermined reference axis, is a uniform curve.
12 . The diaphragm according to claim 11 ,
wherein the cross-sectional shape of the neck portion is an arc.
13 . The diaphragm according to claim 12 ,
wherein a radius of curvature of the neck portion is one-tenth or less of both the first radius of curvature and the second radius of curvature.
14 . An electroacoustic transducer comprising:
the diaphragm according to claim 1 ;
a magnetic circuit;
a frame that holds the magnetic circuit and the diaphragm; and
a voice coil coupled to the diaphragm and disposed in a magnetic gap included in the magnetic circuit.
15 . The electroacoustic transducer according to claim 14 , further comprising:
an edge interposed between the diaphragm and the frame and having an annular shape,
wherein the edge includes a diaphragm connecting portion that follows a shape of an outer peripheral edge portion of the diaphragm.
16 . The electroacoustic transducer according to claim 14 ,
wherein the diaphragm includes:
a neck portion that surrounds the predetermined reference axis extending in the vibration direction; and
at least the first portion, the second portion, and the third portion outside the neck portion,
wherein a cross-sectional shape of the neck portion, along any plane including the predetermined reference axis, is a uniform curve.