Patent ID: 9277325
Filing Date: 2016-03-01
CPC Classification: H04R

Claim Text:
1. An inner magnetic transducer with multiple magnetic gaps and multiple coils, which comprises: a magnetic path and a frame being connected therewith, at least two co-axial annular magnetic gaps and a coil bobbin being inserted into the annular magnetic gaps on which mutually-insulating electromagnetic wires are wound in parallel to form at least two coils, a vibrating membrane or a planar sound generating plate being connected with the coil bobbin and an elastic damping plate, the vibrating membrane or the planar sound generating plate is driven to vibrate in air to generate sound by reciprocating the coil bobbin, or the change in the sound pressure is detected via the vibrating membrane and a sound voltage signal is induced in the coils, the transducer being characterized in that, the frame is made of non-magnetic material and provided with at least two circular axial holes at the axial center thereof, the magnetic path comprises a upper polar plate and a lower polar plate which are co-axially mounted, one axially-magnetized permanent magnet or more than one axially-magnetized permanent magnets of the same thickness is sandwiched between the upper polar plate and the lower polar plate, the two polar plates have the same projected area and match with the permanent magnet, a bracket is made of non-magnetic material and provided with an inwardly convex circular platform at the axial center thereof, the circular platform has a smooth and well-defined vertical outer circular surface, an annular groove is arranged on the outside of the vertical outer circular surface and is provided with two or more vent holes evenly distributed in the bottom thereof, the outerside of the annular groove constitutes the annular thin wall of the bracket, at a corresponding axial height or at the top end of the inner circumferential surface of the annular thin wall, a smooth and well-defined horizontal positioning surface is arranged, at a corresponding axial height of the inner circumferential surface or the outer circumferential surface of the annular thin wall, a smooth and well-defined vertical positioning surface is further arranged, the upper and lower polar plate, and the permanent magnet is adhesively fixed onto the axial center of the circular platform surface of the bracket, an annular magnetic yoke being co-axially mounted with the upper and lower polar plates and the permanent magnet, is at its one end engagely or adhesively fixed with and meanwhile stopped by the vertical positioning surface of the annular thin wall of the bracket, and at the other end embedded into the circular axial holes in the bottom of the frame and jointly or adhesively fixed with the frame, two end surfaces of the annular magnetic yoke extend beyond, in their axial heights, the outer polar surfaces of the upper and lower polar plates, respectively, by a H-value of 0.5-20 mm, and form two groups of vertically symmetrical magnetic gap magnetic paths, two co-axial annular magnetic gaps of the same diameter are formed between the inner circumferential surface of the annular magnetic yoke and the vertical circumferential surfaces of the upper and lower polar plates; two of said coils, which are co-axially mounted, are inserted into the annular magnetic gaps, said coils are formed by winding one or two layers of electromagnetic wires, a corresponding space is arranged between the two coils, and the winding directions of the two coils and the directions of current flowing through the two coils are set such that the two coils generate electrodynamic forces F of the same direction at the same working instant; the transducer has two groups of magnetic paths which are vertically and horizontally symmetrical in terms of geometrical shape and magnetic performance, with the central axis of the upper and lower plates and the permanent magnet as the vertical symmetrical axis, and with the halving line X-X axis at the half axial height of the permanent magnet as the horizontal symmetrical axis; the two coils are set identical to each other in terms of the cross-sectional area of electromagnetic wires, the number of turns, the winding extent, the resistance, the absolute value of inductance and the tensile force during winding and thus form two groups of vertically symmetrical coil circuits by taking the halving line X-X axis at the half axial height of the permanent magnet as the horizontal symmetrical axis, the inductances of the two coils and the back electromotive forces induced in course of their reciprocating movements are cancelled out due to a difference in phase angle of 180 degrees, and hence the transducer is an inner magnetic transducer with multiple magnetic gaps and multiple coils which has resistance load characteristics or approximately resistance load characteristics and has high sensitivity, high analytic capability and high fidelity.