Axial magnetization magnetic crown magnet assembly, motor for electrodynamic loudspeaker comprising it, and associated electrodynamic loudspeaker

Abstract

Magnet assembly with axially magnetized magnetic rings, motor for electrodynamic loudspeaker comprising it, and associated electrodynamic loudspeaker The present invention relates to a magnet assembly (1) for an electrodynamic loudspeaker motor, comprising a first outer pair of axially magnetized magnetic rings (2, 3) and a second inner pair of axially magnetized magnetic rings (4, 5), each outer magnetic ring (2, 3) consisting of a plurality of identical axially magnetized outer permanent magnets (2a, 3a) arranged in a circle, the outer permanent magnets (2a, 3a) having either a cylindrical shape or a rectangular parallelepiped shape, the magnet assembly (1) further comprising outer steel rings (6, 7), inner steel rings (8, 9), an external separator (10) arranged between the outer steel rings (6,7) and an internal separator (11) arranged between the internal steel rings (8, 9). Figure to be published with the abstract: Figure 4,

Description

Title of the invention: Axial magnetization magnetic crown magnet assembly, motor for electrodynamic loudspeaker comprising it, and associated electrodynamic loudspeaker

[0001] The present invention relates to the field of electrodynamic loudspeakers, and in particular relates to a magnet assembly with axially magnetized magnetic crowns for an electrodynamic loudspeaker motor, to a motor for an electrodynamic loudspeaker comprising said magnet assembly, and to an electrodynamic loudspeaker provided with said motor.

[0002] Electrodynamic loudspeakers (or transducers) have many defects, in particular behavior tainted by non-linearities, which constitutes a major drawback.

[0003] A conventional electrodynamic loudspeaker motor comprises an electromagnetic actuator, most often composed of a winding arranged on a moving assembly, within a magnetic field generated by a permanent magnet assembly, the configuration of the permanent magnetic field having a so-called radial symmetry between the north and south poles of the permanent magnet assembly. When the winding is traversed by a current modulated in amplitude and frequency, the induced mechanical displacement at audible frequency is transformed into an acoustic field by means of a membrane acting as an emissive surface, also called an acoustic radiator. The sound quality of the electrodynamic loudspeaker depends on the frequency response curve, which must be as invariant as possible over the entire bandwidth (for example, from 16 Hz to 20,000 Hz), and on the linearity of the system marked by the presence of a minimum of harmonic distortions and intermodulation.

[0004] If the electrodynamic loudspeaker favors all frequencies equally, the reproduction of the timbre of a musical instrument, constituting the useful harmonics of the sound, seems a priori to be able to be assured. The reality, however, proves to be more complex given the need to properly reproduce the attack transients of the sounds, representative of the acoustic signature of quality instruments. The response of the loudspeaker to the transients is an essential condition of "fidelity" which can be tested by detecting the "dragging" of the membrane when the loudspeaker is stressed by a train of impulses. The inertia of the moving assembly and the forces due to self-induction phenomena contribute to this defect.

[0005] Acoustic, optical and electrical measurements show that there is no ideal electrodynamic loudspeaker, and that each implementation has defects in terms of bandwidth limitation, various resonance peaks and inertia. The coupling of several loudspeakers makes it possible in principle to overcome many defects, but conversely it sometimes happens that the defects accumulate in a way that is prohibitive for quality musical reproduction.

[0006] Furthermore, existing electrodynamic loudspeakers are affected by generally poor electroacoustic efficiencies, with values ​​between 0.5% and 5%. For example, a room must be soundproofed with approximately 100 WRMS to ensure the reproduction of the fortissimos of a piano delivering approximately 150 mW.

[0007] The useful driving force at the origin of the displacement of the moving assembly results from the interaction of the magnetic induction field, noted B, with each element of length of the winding crossed by a current noted i(t). On the local level, the elementary force F (in Newton) applied to a charge carrier moving within an induction field is called the Lorentz force and is exerted in a direction perpendicular to the plane defined by the field and the speed of the carriers. A balance within an elementary volume carrying charges subject to the phenomenon leads to the expression:

[0008] „ .[U - _ Fl] F - = BJ.i

[0009] Everything happens as if the unwound length of the winding, noted 1, was exposed to a homogeneous magnetic induction field, which makes it possible to define the quantity Bi = Bl called force factor (in N / A or in Tm) of the driving part (also called "motor") of the electrodynamic loudspeaker.

[0010] This force, modulated by the intensity, stresses the moving assembly whose mechanical behavior is dictated by three components: an inertial force, product of the mass of the moving parts (Mm) by the imposed acceleration, a damping force, generally considered proportional to the speed of movement via a constant noted fm (in N / (m / s) or kg / s) (fm being most often noted Rm in terms of mechanical resistance), and a restoring force linked to the suspension mechanics affected by a stiffness noted km (in N / m). For a translation guided on an x ​​axis, the behavior equation of such an idealized electrodynamic loudspeaker is written:

[0011] F = Bd = +f .¾ + [21 * fft at* J m dt ffl

[0012] This general description relationship of any damped oscillator is encountered in many physical systems.

[0013] Equation [2] in all generality presents in its left-hand member the oscillation control request of the system described by the right-hand member. In this sense, the implementation of the Lorentz force historically underlines the originality of the invention of the loudspeaker, motivated by the intensive development of the telephone (the tube amplifiers (thermionic emission tubes, known as radio tubes) had not yet been developed, and the concept of electrical impedance remained uncertain for those skilled in the art).

[0014] Ideally, it is appropriate, whatever the intensity, to keep the force factor Bi= Bl invariant, and this whatever the position of the moving equipment during operation.

[0015] It is thus useful to plot the shape of Bi as a function of x, the latter parameter denoting the displacement of the membrane in the longitudinal direction of the loudspeaker, to get an idea of ​​the quality of the loudspeaker. Ideally, it would be important to have a flat plot over the entire operational range to have optimal reproduction of the stress signals. For a conventional electrodynamic loudspeaker, the representation of this plot takes approximately the form of a Gaussian, and many developments have sought (with very relative success) to improve this behavior. The generic arrangement of the winding of the moving element in a conventional loudspeaker shows the proximity between the winding and the fixed parts of the permanent magnet assembly.Such a conformation is conducive to the generation of eddy currents within the fixed electrically conductive parts when the moving assembly is activated, particularly at high frequency.

[0016] European patent application EP3634013A1 describes a magnet system for an electromechanical transducer, in which the magnet system comprises a first external pair of axially magnetized annular permanent magnets and a second internal pair of axially magnetized annular permanent magnets in opposite polarity with respect to the first pair of permanent magnets, a moving coil being arranged in the air gap formed between the first pair of permanent magnets and the second pair of permanent magnets. However, this existing magnet system does not allow a constant magnetic field to be obtained that can be observed with respect to the travel of the moving assembly of the electrodynamic loudspeaker motor, and therefore does not allow the force factor of the driving part to be linearized over the entire useful travel of the moving coil.Indeed, with this existing system of magnets, the shape of the evolution of the magnetic field in space associated with the course of the mobile assembly is strongly distorted.

[0017] French patent application FR3132404A1 describes a magnet assembly which is similar to that described in European patent application EP3634013A1 and in which, in addition, the inner annular permanent magnets are respectively offset by an offset distance in the outer annular permanent magnets, so as to obtain compensated magnetic field configurations. However, since the axially magnetized annular permanent magnets are rela tively expensive, this existing magnet assembly is relatively expensive to manufacture. In addition, this existing magnet assembly does not allow optimal performance to be obtained in terms of invariance of the force factor over the useful stroke of the moving assembly of the electrodynamic loudspeaker motor.

[0018] The present invention aims to solve the drawbacks of the prior art, by proposing a magnet assembly for an electrodynamic loudspeaker motor, comprising a first external pair of axially magnetized magnetic rings and a second internal pair of axially magnetized magnetic rings, each of the magnetic rings of the first external pair of magnetic rings being made up of a plurality of identical permanent magnets (in the shape of a cylinder or a rectangular parallelepiped) arranged in a circle, which makes it possible to obtain a reduction in the manufacturing cost of the magnet assembly and also to obtain an optimization of the performance of the electrodynamic loudspeaker motor in terms of invariance of the force factor over a significant stroke of its moving assembly.

[0019] The present invention therefore relates to a magnet assembly for an electrodynamic loudspeaker motor, said magnet assembly comprising a first outer pair of magnetic rings and a second inner pair of magnetic rings, each magnetic ring of each of the first and second pairs of magnetic rings having an axial magnetization; the first outer pair of magnetic rings comprising a first outer magnetic ring and a second outer magnetic ring, said first and second outer magnetic rings being arranged coaxially opposite each other, being spaced apart from each other and having the same dimensions;the second inner pair of magnetic rings comprising a first inner magnetic ring and a second inner magnetic ring, said first and second inner magnetic rings being arranged coaxially opposite each other, being spaced apart from each other and having the same dimensions, the first and second inner magnetic rings and the first and second outer magnetic rings being arranged coaxially, i.e. having the same central axis of symmetry passing through the center of each magnetic ring and perpendicular to the plane of each magnetic ring, the first inner magnetic ring being arranged inside the first outer magnetic ring and the second inner magnetic ring being arranged inside the second outer magnetic ring;the magnetization directions of the internal and external magnetic rings being parallel to their central axis of symmetry and configured such that the direction of the north-south magnetic field of the first internal magnetic ring is opposite to that of the first external magnetic ring, the direction of the; north-south magnetic field of the first inner magnetic ring is opposite to that of the second inner magnetic ring, and the direction of the north-south magnetic field of the first outer magnetic ring is opposite to that of the second outer magnetic ring; characterized by the fact that:

[0020] - the first external magnetic crown is made up of a plurality of first identical external permanent magnets arranged in a circle, and the second external magnetic ring is constituted by a plurality of identical second external permanent magnets arranged in a circle, the first external permanent magnets and the second external permanent magnets being one of axially magnetized cylindrical permanent magnets and height-magnetized rectangular parallelepiped-shaped permanent magnets;

[0021] - the magnet assembly further comprises a first outer steel ring, a second outer steel ring, a first inner steel ring and a second inner steel ring which are arranged coaxially with the first outer pair of magnetic rings and the second inner pair of magnetic rings, the first outer steel ring being in contact with the first outer magnetic ring, the second outer steel ring being in contact with the second outer magnetic ring, the first inner steel ring being in contact with the first inner magnetic ring, and the second inner steel ring being in contact with the second inner magnetic ring; and

[0022] - the magnet assembly further comprises an external separator disposed between the first and second outer steel rings and an inner separator disposed between the first and second inner steel rings, such that within the magnet assembly, an inner stack successively comprising the first inner magnetic ring, the first inner steel ring, the inner separator, the second inner steel ring and the second inner magnetic ring is formed inside an outer stack successively comprising the first outer magnetic ring, the first outer steel ring, the outer separator, the second outer steel ring and the second outer magnetic ring, with an air gap formed between the inner and outer stacks.

[0023] The external magnetic crowns, the internal magnetic crowns and the steel rings are arranged coaxially, and therefore have the same central axis of symmetry.

[0024] By axially magnetized magnetic crown is meant a magnetic crown (i.e., a single annular magnetic object, or a set of magnetic elements arranged in a circle) having an axial flux magnetic field relative to the central axis of symmetry of the magnetic crown. The magnetic crown is thus magnetized relative to its height (along its central axis of symmetry), the north pole of the magnetic crown being on one of the two circular faces at the ends of the magnetic crown, and the south pole of the magnetic crown being on the other of the two circular faces at the ends of the magnetic crown.

[0025] The magnetic element(s) constituting each of the magnetic crowns may be made of at least one material from among neodymium, iron, boron, cobalt, nickel, a ferromagnetic ceramic comprising at least one iron oxide, an iron nitride, samarium, zinc and aluminum.

[0026] In the case of cylindrical external permanent magnets, for each of the plurality of first axially magnetized external cylindrical permanent magnets arranged in a circle, its axis of revolution is parallel to the central axis of symmetry of the first external magnetic ring. Similarly, for each of the plurality of second axially magnetized external cylindrical permanent magnets arranged in a circle, its axis of revolution is parallel to the central axis of symmetry of the second external magnetic ring.

[0027] By axially magnetized cylindrical permanent magnet is meant a permanent magnet in the shape of a cylinder having an axial flux magnetic field relative to its axis of revolution. The cylindrical permanent magnet is thus magnetized relative to its height (along its axis of revolution), the north pole of the cylindrical permanent magnet being on one of its two circular faces at the ends of the cylinder, and the south pole of the cylindrical permanent magnet being on the other of its two circular faces at the ends of the cylinder.

[0028] In the case of rectangular parallelepiped-shaped external permanent magnets, for each of the plurality of first external permanent magnets arranged in a circle, its height direction is parallel to the central axis of symmetry of the first external magnetic ring, and one of its sides is oriented toward the central axis of symmetry of the first external magnetic ring. Similarly, for each of the plurality of second external permanent magnets arranged in a circle, its height direction is parallel to the central axis of symmetry of the second external magnetic ring, and one of its sides is oriented toward the central axis of symmetry of the second external magnetic ring.

[0029] A rectangular parallelepiped-shaped permanent magnet with height-magnetization is understood to mean a rectangular parallelepiped-shaped permanent magnet having a magnetic field whose flux is in the height direction of the rectangular parallelepiped. The rectangular parallelepiped-shaped permanent magnet is thus magnetized in relation to its height, the north pole of the rectangular parallelepiped-shaped permanent magnet being located on one of the two ends (upper or lower) of the rectangular parallelepiped, and the south pole of the permanent magnet in the shape of a rectangular parallelepiped located on the other (lower or upper) of the two ends of the rectangular parallelepiped.

[0030] The plurality of first external permanent magnets are arranged in a circle preferably non-contiguously, but could also be arranged in a circle contiguously, without departing from the scope of the present invention.

[0031] Similarly, the plurality of second external permanent magnets are arranged in a circle preferably non-contiguously, but could also be arranged in a circle contiguously, without departing from the scope of the present invention.

[0032] The specific arrangement of the external magnetic crowns and the internal magnetic crowns makes it possible to ensure a function of compensating for the non-linearities of the magnetic field in the magnet assembly.

[0033] In the present invention, the external annular permanent magnets with axial magnetization of French patent application FR3132404A1 are replaced by composite structures of small cylindrical or parallelepiped magnets (so-called barrel structures), making it possible to obtain a magnetic field map that is particularly suitable for maintaining the electromechanical stress (i.e., the force factor) of the moving assembly of the motor almost invariant at any point of its useful travel within the air gap of the magnet assembly.

[0034] Consequently, the use of cylindrical or parallelepipedal permanent magnets (low cost) arranged in barrels makes it possible to replicate the field maps exhibiting the invariance of the value of the force factor Bi over the entire useful travel of the moving assembly.

[0035] The composite structure arranged in a barrel of each external magnetic crown makes it possible on the one hand to have openwork zones promoting the evacuation of heat, and on the other hand to significantly reduce the manufacturing cost of the motor. Indeed, considering an annular permanent magnet, beyond a few centimeters in diameter, the sum of the costs of the basic cylindrical or parallelepiped magnetic elements making it possible to reconstitute the magnetic field remains systematically lower than the price of this annular permanent magnet.

[0036] Thus, the magnet assembly according to the present invention makes it possible to better satisfy the requirements of invariance of the magnetic field for a reduced manufacturing cost.

[0037] The introduction of steel rings (preferably DC01 low carbon mild steel) and internal and external separators has the following advantages:

[0038] - it promotes a reduction in the mass of the magnetic materials to be used artwork ;

[0039] - it guarantees the thermal stability of the magnetic configurations, with regard to the demagnetization curves with respect to the thermal stresses envisaged at various temperatures; and

[0040] - it facilitates the mounting of the motor due to the constriction of flow within the steel significantly reducing the opposing forces between the permanent magnets.

[0041] The steel rings thus make it possible to optimize the arrangement of the magnetic field lines (optimal constriction of the magnetic field lines), while significantly reducing the mechanical constraints observable at the time of assembly of the magnet assembly.

[0042] The magnet assembly according to the present invention thus makes it possible to produce loudspeakers exhibiting linear behavior (at moderate cost), an essential quality for quality sound reproduction.

[0043] According to a first embodiment of the invention, the first internal magnetic ring consists of a first annular permanent magnet with axial magnetization, and the second internal magnetic ring consists of a second annular permanent magnet with axial magnetization.

[0044] An axially magnetized annular permanent magnet is understood to mean a ring-shaped permanent magnet having an axial flux magnetic field relative to the central axis of symmetry of the ring. The annular permanent magnet is thus magnetized relative to its height (along its central axis of symmetry), the north pole of the annular permanent magnet being on one of the two circular faces located at the ends of the ring, and the south pole of the annular permanent magnet being on the other of the two circular faces located at the ends of the ring.

[0045] According to a second embodiment of the invention, the first internal magnetic ring consists of a plurality of identical first internal permanent magnets arranged in a circle, and the second internal magnetic ring consists of a plurality of identical second internal permanent magnets arranged in a circle, the first internal permanent magnets and the second internal permanent magnets being one of axially magnetized cylindrical permanent magnets and height-magnetized rectangular parallelepiped-shaped permanent magnets.

[0046] In the case of cylindrical internal permanent magnets, for each of the plurality of first axially magnetized internal cylindrical permanent magnets arranged in a circle, its axis of revolution is parallel to the central axis of symmetry of the first internal magnetic ring. Similarly, for each of the plurality of second axially magnetized internal cylindrical permanent magnets arranged in a circle, its axis of revolution is parallel to the central axis of symmetry of the second internal magnetic ring.

[0047] In the case of rectangular parallelepiped-shaped internal permanent magnets, for each of the plurality of first internal permanent magnets arranged in a circle, its height direction is parallel to the central axis of symmetry of the first ring internal magnetic ring, and one of its sides is oriented toward the central axis of symmetry of the first internal magnetic ring. Similarly, for each of the plurality of second internal permanent magnets arranged in a circle, its height direction is parallel to the central axis of symmetry of the second internal magnetic ring, and one of its sides is oriented toward the central axis of symmetry of the second internal magnetic ring.

[0048] The plurality of first internal permanent magnets are arranged in a circle preferably non-contiguously, but could also be arranged in a circle contiguously, without departing from the scope of the present invention.

[0049] Similarly, the plurality of second internal permanent magnets are arranged in a circle preferably non-contiguously, but could also be arranged in a circle contiguously, without departing from the scope of the present invention.

[0050] In this second embodiment, since the internal crowns are also made of cylindrical or parallelepipedal permanent magnets, the manufacturing cost of the magnet assembly is further reduced.

[0051] In addition, the composite structure arranged in the barrel of each internal magnetic crown allows for openwork areas to further promote heat dissipation.

[0052] The magnet assembly according to this second embodiment makes it possible to obtain a motor of larger dimensions and greater power.

[0053] According to a particular characteristic of the invention, the external separator consists of an external separation ring arranged between the first and second external steel rings, the external separation ring being made of a non-ferromagnetic material such as aluminum, copper or a polymer.

[0054] Preferably, the external separation ring is made of aluminum or copper and allows the upper and lower parts of the magnet assembly to be separated. Aluminum and copper, being good conductors of electricity, allow the influence of the steel to be reduced and conduct the heat to be evacuated very well.

[0055] According to a particular characteristic of the invention, the internal separator consists of an internal separation ring arranged between the first and second internal steel rings, the internal separation ring being made of a non-ferromagnetic material such as aluminum, copper or a polymer.

[0056] Preferably, the internal separation ring is made of polymer material and, in the case of the second embodiment, can be grooved so as to facilitate air exchange.

[0057] According to a particular characteristic of the invention, the magnet assembly further comprises a housing comprising a first housing part and a second housing part configured to be fixed to each other while receiving between them the em- internal and external piles.

[0058] The two-part housing of the magnet assembly according to the present invention makes it possible to simplify the assembly procedures, on the one hand to reduce costs, and on the other hand to facilitate assemblies, in particular with regard to the mechanical constraints observed when relatively large permanent magnets are made to interact at a short distance. The nature and shape of the first and second housing parts produced make it possible to facilitate the positioning procedures of each element of the internal and external stacks of the magnet assembly.

[0059] The first and second housing portions are made of a non-ferromagnetic material such as a polymer or aluminum.

[0060] The first and second housing parts may, for example, be precisely made by three-dimensional (3D) printing (e.g., using polyethylene terephthalate glycol (PETG)).

[0061] Alternatively, the first and second housing parts may also be made by machining specific parts (e.g., polyvinyl chloride (PVC)).

[0062] It should be noted that working with the addition of material (advantage of 3D printing) results in a reduced cost compared to traditional machining carried out by material removal (machining).

[0063] Finally, in another variant, the first and second housing parts can also be produced by injection molding.

[0064] According to a particular characteristic of the invention, the first housing part comprises a first internal housing configured to receive the first internal magnetic crown and a first external housing consisting of a plurality of first external compartments arranged in a circle and configured to respectively receive the plurality of first external permanent magnets of the first external magnetic crown.

[0065] The first external compartments may be either cylindrical in the case of first cylindrical external permanent magnets, or in the shape of a rectangular parallelepiped in the case of first external permanent magnets in the shape of a rectangular parallelepiped.

[0066] Thus, the first compartments of the first housing part make it possible, in the manner of a barrel, to precisely house the plurality of first external permanent magnets.

[0067] According to a particular characteristic of the invention, the second housing part comprises a second internal housing configured to receive the second internal magnetic crown and a second external housing consisting of a plurality of second external compartments arranged in a circle and configured to respectively receive the plurality of second external permanent magnets of the second external magnetic ring.

[0068] The second external compartments may be either cylindrical in the case of second cylindrical external permanent magnets, or in the shape of a rectangular parallelepiped in the case of second external permanent magnets in the shape of a rectangular parallelepiped.

[0069] Thus, the second compartments of the second housing part make it possible, in the manner of a barrel, to precisely house the plurality of second external permanent magnets.

[0070] According to a particular characteristic of the invention, the first housing part further comprises a barrel extending axially from the first internal housing and around which the first internal magnetic crown, the first internal steel ring, the internal separator, the second internal steel ring and the second internal magnetic crown are capable of being successively stacked.

[0071] Thus, the barrel of the first part of the housing makes it easier to stack around it the different elements of the internal stack of the magnet assembly.

[0072] According to a particular characteristic of the invention, a plurality of internal compartments are formed, being arranged in a circle, at the periphery of the barrel of the first housing part, said plurality of internal compartments serving, at the base of the barrel, as a first internal housing configured to receive the plurality of first internal permanent magnets of the first internal magnetic ring and also, at the free end of the barrel, as an additional internal housing configured to receive the plurality of second internal permanent magnets of the second internal magnetic ring.

[0073] The internal compartments may be either cylindrical in the case of first and second cylindrical internal permanent magnets, or rectangular parallelepiped-shaped in the case of first and second rectangular parallelepiped-shaped internal permanent magnets.

[0074] Thus, in the second embodiment, the plurality of internal compartments makes it possible both to house the first internal permanent magnets (at the base of the barrel), and, after stacking the first internal steel ring, the internal separator and the second internal steel ring, also to house the second internal permanent magnets (at the free end of the barrel).

[0075] According to a particular characteristic of the invention, at least one of the first housing part and the second housing part has interior channels configured to allow an exchange of air with the exterior.

[0076] Thus, the internal channels provided within the housing of the magnet assembly allow for increased heat evacuation compared to what is allowed by the structures of the prior art.

[0077] Preferably, the first housing part (including its barrel) is provided with internal channels facilitating air exchanges with the external environment so as to promote cooling of the engine.

[0078] The present invention also relates to a motor for an electrodynamic loudspeaker comprising a magnet assembly as described above and a moving assembly comprising a cylindrical coil support which is partly inserted into the air gap of the magnet assembly and on which is wound a coil arranged in the air gap of the magnet assembly.

[0079] Thus, the injection of an amplitude- and frequency-modulated current into the coil carried by the moving assembly causes the moving assembly, and therefore the coil, to move in the air gap of the magnet assembly in which the radial component of the generated magnetic field is substantially constant (i.e., a force factor Bl that is substantially invariant over the entire useful travel of the coil), which allows quality sound reproduction with much less loss and non-linear distortion than conventional loudspeakers.

[0080] Furthermore, the use of cylindrical or parallelepipedal permanent magnets in the magnet assembly makes it possible to obtain a relatively light motor compared to conventional motors.

[0081] The motor according to the present invention can be stressed in voltage (in a traditional manner), but is also particularly suitable for being the subject of a current control mode (for a stress regime imposed by an electronic conditioner of the voltage / current converter type).

[0082] The present invention further relates to an electrodynamic loudspeaker comprising a chassis on which are arranged a motor as described above and a membrane connected to the moving assembly of the motor.

[0083] Thus, the mechanical displacement of the moving element induced at audible frequency is transformed into an acoustic field by means of the membrane playing the role of emissive surface (also called acoustic radiator).

[0084] The electrodynamic loudspeaker according to the present invention allows quality sound reproduction with much less loss and non-linearity distortion than conventional systems.

[0085] To better illustrate the object of the present invention, preferred embodiments will be described below, by way of illustration and not limitation, with reference to the appended drawings.

[0086] In these drawings:

[0087] [Fig. 1] is a perspective view of a magnet assembly according to a first embodiment of the invention;

[0088] [Fig.2] is an exploded view of the magnet assembly according to the first embodiment of the invention;

[0089] [Fig.3] is a perspective view of the first outer pair of magnetic rings and the second inner pair of magnetic rings of the magnet assembly according to the first embodiment of the invention;

[0090] [Fig.4] is a sectional view of the magnet assembly according to the first mode of rea lization of the invention;

[0091] [Fig.5] is a perspective view of the first housing part of the magnet assembly according to the first embodiment of the invention;

[0092] [Fig.6] is a perspective view of the second housing part of the magnet assembly according to the first embodiment of the invention;

[0093] [Fig.7] is a perspective view of a magnet assembly according to a second mode of realization of the invention;

[0094] [Fig.8] is an exploded view of the magnet assembly according to the second embodiment of the invention;

[0095] [Fig.9] is a perspective view of the first outer pair of crowns ma magnetic and the second internal pair of magnetic crowns of the magnet assembly according to the second embodiment of the invention;

[0096] [Fig. 10] is a sectional view of the magnet assembly according to the second embodiment of the invention;

[0097] [Fig. 11] is a perspective view of the first housing part of the magnet assembly according to the second embodiment of the invention;

[0098] [Fig. 12] is a perspective view of the second housing part of the magnet assembly according to the second embodiment of the invention;

[0099] [Fig. 13] is a perspective view of an exemplary moving assembly for an electrodynamic loudspeaker motor according to the invention;

[0100] [Fig. 14] is a schematic sectional view of an electrodynamic loudspeaker motor according to the present invention;

[0101] [Fig. 15] is an exemplary curve representing the relative invariance of the force factor Bl as a function of the displacement of the moving assembly in the electrodynamic loudspeaker motor according to the invention; and

[0102] [Fig. 16] is a top view of the first inner and outer magnetic rings of a magnet assembly according to a third embodiment of the present invention.

[0103] Referring to Figures 1 to 6, it can be seen that there is shown a magnet assembly 1 according to a first embodiment of the present invention.

[0104] The magnet assembly 1 comprises a first external pair of magnetic rings comprising a first external magnetic ring 2 and a second outer magnetic crown 3, and a second inner pair of magnetic crowns comprising a first inner magnetic crown 4 and a second inner magnetic crown 5.

[0105] Each of the first and second external magnetic rings 2 and 3 and the first and second internal magnetic rings 4 and 5 has an axial magnetization.

[0106] By axially magnetized magnetic crown, we mean a magnetic crown (i.e., a single annular magnetic object, or a set of magnetic elements arranged in a circle) having an axial flux magnetic field relative to the central axis of symmetry of the magnetic crown. The magnetic crown is thus magnetized relative to its height (along its central axis of symmetry), the north pole of the magnetic crown being on one of the two circular faces at the ends of the magnetic crown, and the south pole of the magnetic crown being on the other of the two circular faces at the ends of the magnetic crown.

[0107] The first and second external magnetic rings 2 and 3 are arranged coaxially opposite each other, are spaced apart from each other and have the same dimensions.

[0108] Similarly, the first and second internal magnetic rings 4 and 5 are arranged coaxially opposite each other, are spaced apart from each other and have the same dimensions.

[0109] The first and second internal magnetic rings 2 and 3 and the first and second external magnetic rings 4 and 5 are arranged coaxially, that is to say they have the same central axis of symmetry passing through the center of each magnetic ring 2, 3, 4, 5 and perpendicular to the plane of each magnetic ring 2, 3, 4, 5, the first internal magnetic ring 4 being arranged inside the first external magnetic ring 2 and the second internal magnetic ring 5 being arranged inside the second external magnetic ring 3.

[0110] The magnetization directions of the internal 4, 5 and external 2, 3 magnetic rings are parallel to their central axis of symmetry and configured such that the direction of the north-south magnetic field of the first internal magnetic ring 4 is opposite to that of the first external magnetic ring 2, the direction of the north-south magnetic field of the first internal magnetic ring 4 is opposite to that of the second internal magnetic ring 5, and the direction of the north-south magnetic field of the first external magnetic ring 2 is opposite to that of the second external magnetic ring 3.

[0111] The first external magnetic crown 2 is made up of eleven first magnets identical external cylindrical permanent magnets 2a with axial magnetization arranged in a circle, and the second external magnetic ring 3 consists of eleven second identical external cylindrical permanent magnets 3a with axial magnetization arranged in a circle.

[0112] For each of the plurality of first external cylindrical permanent magnets 2a, its axis of revolution is parallel to the central axis of symmetry of the first external magnetic ring 2.

[0113] Similarly, for each of the plurality of second external cylindrical permanent magnets 3a, its axis of revolution is parallel to the central axis of symmetry of the second external magnetic ring 3.

[0114] It should be noted that each of the first and second external magnetic rings 2, 3 could also be made up of any number of external cylindrical permanent magnets 2a, 3a arranged in a circle, without departing from the scope of the present invention, said number being a function of the desired inner radius of the external magnetic ring 2, 3.

[0115] By axially magnetized cylindrical permanent magnet 2a, 3a is meant a permanent magnet in the form of a cylinder having an axial flux magnetic field relative to its axis of revolution. The cylindrical permanent magnet is thus magnetized relative to its height (along its axis of revolution), the north pole of the cylindrical permanent magnet being on one of its two circular faces at the ends of the cylinder, and the south pole of the cylindrical permanent magnet being on the other of its two circular faces at the ends of the cylinder.

[0116] It should be noted that the first and second external cylindrical permanent magnets with axial magnetization 2a and 3a could also be replaced by permanent magnets in the shape of a rectangular parallelepiped with magnetization according to the height, without departing from the scope of the present invention.

[0117] The plurality of first external cylindrical permanent magnets 2a are arranged in a circle in a non-contiguous manner, but could also be arranged in a circle in a contiguous manner, without departing from the scope of the present invention.

[0118] Similarly, the plurality of second external cylindrical permanent magnets 3a are arranged in a circle in a non-contiguous manner, but could also be arranged in a circle in a contiguous manner, without departing from the scope of the present invention.

[0119] The first and second external cylindrical permanent magnets 2a, 3a may, for example, have the following characteristics: materials: Nd-Fe-B (neodymium-iron-boron), N35, Nickel; mass = 5.86g; diameter = 10mm; height = 10mm; maximum attraction mass = 4.95kg; internal induction =1.17 Tesla.

[0120] However, the first and second external cylindrical permanent magnets 2a, 3a could also be made of at least one material among neodymium, iron, boron, cobalt, nickel, a ferromagnetic ceramic comprising at least one of iron oxide, iron nitride, samarium, zinc and aluminum, without departing from the scope of the present invention.

[0121] In the first embodiment of the invention as shown in Figures 1 to 6, the first internal magnetic ring 4 consists of a first annular permanent magnet with axial magnetization, and the second internal magnetic ring 5 consists of a second annular permanent magnet with axial magnetization.

[0122] An axially magnetized annular permanent magnet is understood to mean a ring-shaped permanent magnet having an axial flux magnetic field relative to the central axis of symmetry of the ring. The annular permanent magnet is thus magnetized relative to its height (along its central axis of symmetry), the north pole of the annular permanent magnet being on one of the two circular faces located at the ends of the ring, and the south pole of the annular permanent magnet being on the other of the two circular faces located at the ends of the ring.

[0123] The annular permanent magnets constituting the internal magnetic rings 4, 5 can, for example, be made of a material of the Nd-Fe-B (neodymium-iron-boron) type.

[0124] By way of example, the annular permanent magnets constituting the internal magnetic rings 4, 5 have a rectangular section, an external diameter of 19 mm, an internal diameter of 9 mm, and a height of 6 mm.

[0125] The magnet assembly 1 further comprises a first outer steel ring 6, a second outer steel ring 7, a first inner steel ring 8 and a second inner steel ring 9 which are arranged coaxially with the first outer pair of magnetic rings 2, 3 and the second inner pair of magnetic rings 4, 5.

[0126] For example, the external steel rings 6, 7 have a rectangular section, an external diameter of 49.4 mm, an internal diameter of 27 mm, and a height of 2 mm, and the internal steel rings 8, 9 have a rectangular section, an external diameter of 24.5 mm, an internal diameter of 9 mm, and a height of 3 mm.

[0127] The magnet assembly 1 further comprises a ring-shaped outer separator 10 disposed between the first and second outer steel rings 6, 7, and a ring-shaped inner separator 11 disposed between the first and second inner steel rings 8, 9.

[0128] For example, the outer separator 10 has a rectangular section, an outer diameter of 54 mm, an inner diameter of 27 mm, and a height of 6.2 mm, and the inner separator 11a has a rectangular section, an outer diameter of 24.5 mm, an inner diameter of 9 mm, and a height of 6.2 mm.

[0129] The external magnetic crowns 2, 3, the internal magnetic crowns 4, 5, the steel rings 6, 7, 8, 9 and the external and internal separators 10, 11 are arranged coaxially, and therefore have the same central axis of symmetry.

[0130] Within the magnet assembly 1, an internal stack successively comprising the first internal magnetic crown 4, the first internal steel ring 8, the internal separator 11, the second internal steel ring 9 and the second internal magnetic crown 5 is formed inside an external stack successively comprising the first external magnetic crown 2, the first external steel ring 6, the external separator 10, the second external steel ring 7 and the second external magnetic crown 3, with an air gap 12 formed between the internal and external stacks.

[0131] Therefore, the first outer steel ring 6 is in contact with the first outer magnetic ring 2a, the second outer steel ring 7 is in contact with the second outer magnetic ring 3, the first inner steel ring 8 is in contact with the first inner magnetic ring 4, and the second inner steel ring 9 is in contact with the second inner magnetic ring 5.

[0132] The steel rings 6, 7, 8, 9 are preferably made of low carbon mild steel DC01.

[0133] The steel rings 6, 7, 8, 9 thus make it possible to optimize the arrangement of the magnetic field lines (optimal constriction of the magnetic field lines), while significantly reducing the mechanical stresses observable at the time of assembly of the magnet assembly 1.

[0134] The external separator 10 is made of an aluminum ring (which is a good conductor of electricity, allows the influence of steel to be reduced, and conducts heat very well to be evacuated), but could also be made of a ring of another non-ferromagnetic material such as a polymer or copper, without departing from the scope of the present invention.

[0135] The internal separator 11 is made of a ring of polymer material, but could also be made of a ring of another ferromagnetic material such as aluminum or copper, without departing from the scope of the present invention.

[0136] The specific arrangement of the external magnetic rings 2, 3 and the internal magnetic rings 4, 5 makes it possible to ensure a function of compensating for the non-linearities of the magnetic field in the magnet assembly 1.

[0137] The composite structure arranged in a barrel of each external magnetic crown 2, 3 makes it possible on the one hand to have openwork zones promoting the evacuation of heat, and on the other hand to significantly reduce the manufacturing cost of the magnet assembly 1. Indeed, considering an annular permanent magnet, beyond a few centimeters in diameter, the sum of the costs of the cylindrical permanent magnets 2a, 3a arranged in a circle making it possible to reconstitute the magnetic field remains systematically in- lower than the price of this permanent ring magnet.

[0138] The magnet assembly 1 further comprises a housing having a first housing portion 13 and a second housing portion 14 configured to be secured to each other while receiving therebetween the inner and outer stacks of the magnet assembly 1.

[0139] The first and second housing parts 13 and 14 are made of a non-ferromagnetic material.

[0140] The first and second housing parts 13, 14 may, for example, be made by 3D printing (for example, using poly(ethylene terephthalate) glycol (PETG)).

[0141] Alternatively, the first and second housing parts 13, 14 may also be made by machining specific parts (for example, from poly(vinyl chloride) (PVC)).

[0142] In another variant, the first and second housing parts 13 and 14 can also be produced by injection molding.

[0143] The first housing part 13 comprises a first internal housing 13a configured to receive the first internal magnetic crown 4 (of the annular permanent magnet type) and a first external housing consisting of eleven first external cylindrical compartments 13b arranged in a circle in a distributed manner and configured to respectively receive in an adjusted manner the eleven first external cylindrical permanent magnets 2a of the first external magnetic crown 2.

[0144] The first housing part 13 further comprises a barrel 13c extending axially from the first internal housing 13a and around which the first internal magnetic crown 4, the first internal steel ring 8, the internal separator 11, the second internal steel ring 9 and the second internal magnetic crown 5 are capable of being successively stacked.

[0145] The second housing part 14 comprises a second internal housing 14a configured to receive the second internal magnetic ring 5 (of the annular permanent magnet type) and a second external housing consisting of eleven second external cylindrical compartments 14b arranged in a distributed circle and configured to respectively receive in an adjusted manner the eleven second external cylindrical permanent magnets 3a of the second external magnetic ring 3.

[0146] The method of assembling the magnet assembly 1 can thus be as follows:

[0147] - insert the first internal magnetic crown 4 of the permanent magnet type annular around the barrel 13c until it is in the first internal housing 13a of the first housing part 13, and insert the first external cylindrical permanent magnets 2a respectively into the first external cylindrical compartments 13b of the first housing part 13;

[0148] - insert the first internal steel ring 8 around the barrel 13c until it is in contact with the first internal magnetic crown 4 of annular permanent magnet type, and arrange the first external steel ring 6 on the first external cylindrical permanent magnets 2a;

[0149] - insert the internal separator 11 around the barrel 13c until it is in contact with the first inner steel ring 8, and arrange the outer separator 10 on the first outer steel ring 6;

[0150] - insert the second internal steel ring 9 around the barrel 13c until it is in contact with the internal separator 11; and

[0151] - insert the second internal magnetic crown 5 of permanent magnet type annular around the barrel 13c until it is in contact with the second inner steel ring 9, and insert the second outer cylindrical permanent magnets 3a respectively into the second outer cylindrical compartments 14b of the second housing part 14 and then arrange the second outer steel ring 7 on the outer cylindrical permanent magnets 3a, then arrange the second housing part 14 on the first housing part 13 so that the second outer cylindrical permanent magnets 14b are in contact with the second outer steel ring 7 and the second inner magnetic ring 5 of the annular permanent magnet type is located in the second inner housing 14a of the second housing part 14.

[0152] The first housing part 13 has four stops 13e uniformly distributed around the periphery of the latter, each stop 13e having a through hole 13d formed parallel to the central axis of symmetry of the magnet assembly 1.

[0153] The second housing part 14 also has four stops 14d uniformly distributed around the periphery of the latter, each stop 14d having a through hole 14c formed parallel to the central axis of symmetry of the magnet assembly 1.

[0154] The four stops 14d of the second housing part 14 are configured to come into contact with the four stops 13e of the first housing part 13 when the first and second housing parts 13 and 14 are mounted on each other.

[0155] The external separator 10 also has four through holes 10a in correspondence with the through holes 13d and 14c of the first and second housing parts 13, 14.

[0156] Thus, the first and second housing parts 13, 14 can be fixed to each other by means of four bolt-nut assemblies (not shown in the figures), each bolt being successively inserted into a respective through hole 14c of the second housing part 14, a respective through hole 10a of the external separator 10 and a respective through hole 13d of the first housing part 13.

[0157] The outer stack of the magnet assembly 1 is thus sandwiched between the first and second housing parts 13, 14.

[0158] A bore 15 is formed axially at the free end of the barrel 13c of the first housing part 13, such that a screw (not shown in the figures) can be inserted into this bore 15 to lock the position of the internal stack of the magnet assembly 1 on the first housing part 13.

[0159] Above each of the four stops 14d of the second housing part 14, an arm 14e is formed in a cantilevered manner, two through holes 14f being formed in each arm 14e. The four arms 14e of the second housing part 14 thus make it possible to fix thereon an electrodynamic loudspeaker chassis (or basket) using the through holes 14f.

[0160] Furthermore, a through hole 13f is formed in the first housing part 13 facing each first external cylindrical permanent magnet 2a, and a through hole 14g is formed in the second housing part 14 facing each second external cylindrical permanent magnet 3a, the through holes 13f and 14g allowing air exchange with the outside so as to facilitate cooling of the electrodynamic speaker motor.

[0161] Referring to Figures 7 to 12, it can be seen that there is shown a magnet assembly 101 according to a second embodiment of the present invention.

[0162] The elements common to the first embodiment of the invention in Figures 1 to 6 and this second embodiment of the invention bear the same reference number to which 100 has been added, and will not be described in more detail here when they are of identical structures.

[0163] The magnet assembly 101 according to the second embodiment is identical to the magnet assembly 1 according to the first embodiment, except that the first internal magnetic ring 104 is constituted by a plurality of identical first internal cylindrical permanent magnets 104a with axial magnetization arranged in a circle, and the second internal magnetic ring 105 is constituted by a plurality of identical second internal cylindrical permanent magnets 105a with axial magnetization arranged in a circle.

[0164] For each of the plurality of first internal cylindrical permanent magnets 104a, its axis of revolution is parallel to the central axis of symmetry of the first internal magnetic ring 104.

[0165] Similarly, for each of the plurality of second internal cylindrical permanent magnets 105a, its axis of revolution is parallel to the central axis of symmetry of the second internal magnetic ring 105.

[0166] It should be noted that the first and second axially magnetized internal cylindrical permanent magnets 104a and 105a could also be replaced by magnets permanent rectangular parallelepiped magnets with height-dependent magnetization, without departing from the scope of the present invention.

[0167] The plurality of first internal cylindrical permanent magnets 104a are arranged in a non-contiguously circular manner, but could also be arranged in a contiguously circular manner, without departing from the scope of the present invention.

[0168] Similarly, the plurality of second internal cylindrical permanent magnets 105a are arranged in a circle in a non-contiguous manner, but could also be arranged in a circle in a contiguous manner, without departing from the scope of the present invention.

[0169] The first and second internal cylindrical permanent magnets 104a, 105a may, for example, have the following characteristics: materials: Nd-Fe-B (neodymium-iron-boron), N35, Nickel; mass = 5.86g; diameter = 10mm; height = 10mm; maximum attraction mass = 4.95kg; internal induction =1.17 Tesla.

[0170] However, the first and second internal cylindrical permanent magnets 104a, 105a could also be made of at least one material among neodymium, iron, boron, cobalt, nickel, a ferromagnetic ceramic comprising at least one iron oxide, an iron nitride, samarium, zinc and aluminum, without departing from the scope of the present invention.

[0171] In this second exemplary embodiment, the first inner magnetic ring 104 consists of eight first inner cylindrical permanent magnets 104a, the second inner magnetic ring 105 consists of eight second inner cylindrical permanent magnets 105a, the first outer magnetic ring 102 consists of sixteen first outer cylindrical permanent magnets 102a, and the second outer magnetic ring 103 consists of sixteen outer cylindrical permanent magnets 103a.However, the inner magnetic rings 104 and 105 could also include any number of inner cylindrical permanent magnets 104a, 105a depending on the desired inner radius of the inner magnetic rings 104 and 105, and the outer magnetic rings 102 and 103 could also include any number of outer cylindrical permanent magnets 102a, 103a depending on the desired inner radius of the outer magnetic rings 102 and 103, without departing from the scope of the present invention.

[0172] In this second embodiment, since the internal magnetic rings 104, 105 are also made of cylindrical permanent magnets 104a, 105a and not annular permanent magnets, the manufacturing cost of the magnet assembly 101 is further reduced.

[0173] Furthermore, the composite structure arranged in a barrel of each internal magnetic crown 104, 105 makes it possible to have openwork zones which further promote the evacuation of heat.

[0174] For example, in the second embodiment, the outer steel rings 106, 107 may have a rectangular section, an outer diameter of 60 mm, an inner diameter of 42 mm, and a height of 4 mm, the inner steel rings 108, 109 may have a rectangular section, an outer diameter of 38.8 mm, an inner diameter of 30.8 mm, and a height of 4 mm, the outer aluminum ring-type separator 110 may have a rectangular section, an outer diameter of 78 mm, an inner diameter of 42 mm, and a height of 7 mm, and the inner separator 111 may have an outer diameter of 38.8 mm, an inner diameter of 30.8 mm, and a height of 7 mm.

[0175] Furthermore, in the second embodiment, the internal separator 111 of the ring type made of polymer material has grooves 111a which facilitate air exchanges with the exterior.

[0176] Unlike the first embodiment, in the second embodiment, the first housing part 113 has only three stops 113e (in which the three through holes 113d are respectively formed), the second housing part 114 has only three stops 114d (in which the three through holes 114c are respectively formed) and three arms 114e. In addition, the annular outer separator 110 has six through holes 110a, three of which are in correspondence with the three through holes 113d of the first housing part 113 to enable the first housing part 113 to be fixed to the outer separator 110 and the other three of which are in correspondence with the three through holes 114c of the second housing part 114 to enable the second housing part 114 to be fixed to the outer separator 110.

[0177] Furthermore, in this second embodiment, a plurality of internal cylindrical compartments 116 are formed, being arranged in a circle, at the periphery of the barrel 113c of the first housing part 113, said plurality of internal cylindrical compartments 116 serving, at the base of the barrel 113c, as a first internal housing 113a configured to receive the plurality of first internal cylindrical permanent magnets 104a of the first internal magnetic ring 104 and also, at the free end of the barrel 113c, as an additional internal housing configured to receive the plurality of second internal cylindrical permanent magnets 105a of the second internal magnetic ring 105.

[0178] Thus, in the second embodiment, the plurality of internal cylindrical compartments 116 make it possible both to house the first internal cylindrical permanent magnets 104a (at the base of the barrel 113c), and, after stacking the first internal steel ring 108, the internal separator 111 and the second steel ring 109 around the barrel 113c of the first housing part 113, also to house the second internal cylindrical permanent magnets 105a (at the free end of the barrel 113c).

[0179] Further, a through hole 113g is formed in the first housing portion 113 opposite each first internal cylindrical permanent magnet 104a, the through holes 113g allowing air exchange with the outside so as to facilitate cooling of the electrodynamic loudspeaker motor.

[0180] The first housing part 113 further has channels in longitudinal interior channels 117a formed in the barrel 113c, first transverse interior channels 117b formed in the barrel 113c at the internal separator 111 and second transverse interior channels 117c formed in the lower part of the first housing part 113, said interior channels 117a, 117b and 117c allowing an exchange of air with the outside for heat evacuation so as to promote the cooling of the electrodynamic loudspeaker motor.

[0181] Compared to the first embodiment, the magnet assembly 101 according to the second embodiment makes it possible to obtain an electrodynamic loudspeaker motor of larger size and greater power.

[0182] If we refer to [Fig. 13], we can see that there is shown there a moving assembly as an example for an electrodynamic loudspeaker motor according to the invention.

[0183] The moving assembly comprises a cylindrical coil support 200 around which a coil 201 is wound.

[0184] One of the ends of the cylindrical coil support 200 is connected to a membrane 202 itself connected to a chassis (or frame) 203 by means of several flexible arms 204 cut from the membrane material. The moving assembly is thus commonly called a “piston”.

[0185] The frame 203 is configured to be fixed on the arms 114e of the second housing part 114 of the magnet assembly 101 so that the coil 201 is located in the air gap 112 of the magnet assembly 101.

[0186] The cylindrical coil support 200 and the membrane 202 may, for example, be made of polyimide film such as Kapton®.

[0187] The frame 203 may, for example, be made of epoxy glass or polymer material.

[0188] A dome 205 closes the opening of the cylindrical coil support 200 at its end connected to the membrane 202.

[0189] The chassis 203 also comprises electrical tracks 206 for supplying the coil 201 with current.

[0190] Although the moving assembly shown in [Fig. 13] is specifically of the piston type, in another embodiment, the coil 201 could also be directly attached to the rear face of the membrane 202, without departing from the scope of the present invention. Furthermore, the entire circumference of the membrane 202 could also be connected to the frame 203 (i.e., absence of flexible arms 204), without deviate from the scope of the present invention.

[0191] Referring to [Fig. 14], it can be seen that there is shown an electrodynamic loudspeaker motor 207 comprising the magnet assembly 101 according to the second embodiment and the moving assembly of [Fig. 13]. It should be noted that the motor 207 could also comprise the magnet assembly 1 according to the first embodiment, without departing from the scope of the present invention.

[0192] In order not to overload the figure, certain elements of the motor 207 have not been shown in [Fig. 14], such as the membrane 202, the frame 203 and the dome 205 of the moving assembly and the first and second housing parts 113 and 114 of the magnet assembly 101.

[0193] For each of the cylindrical permanent magnets 102a, 103a, 104a and 105a, the letter "N" means "north magnetic pole" of the cylindrical permanent magnet, and the letter "S" means "south magnetic pole" of the cylindrical permanent magnet.

[0194] In [Fig. 14], the north magnetic poles of the first and second outer magnetic rings 102 and 103 are opposite, and the south magnetic poles of the first and second inner magnetic rings 104 and 105 are opposite. However, a reverse arrangement could also be envisaged, namely the south magnetic poles of the first and second outer magnetic rings 102 and 103 opposite, and the north magnetic poles of the first and second inner magnetic rings 104 and 105 opposite, without departing from the scope of the present invention.

[0195] The cylindrical coil support 200 of the moving assembly is partially inserted into the air gap 112 of the magnet assembly 101, such that the coil 201 is arranged at the air gap 112 of the magnet assembly 101.

[0196] The magnetic field B generated by the magnet assembly 101 has a radial component Bx along the x axis and an axial component By along the y axis (parallel to the central axis of symmetry of the magnet assembly 101).

[0197] This generic representation of the electrodynamic loudspeaker motor 207 shows the coil 201 moving along the y axis and subjected to the radial component Bx of the magnetic field B generated by the magnet assembly 101, the magnetic field B being oriented towards the center of the magnet assembly 101, that is to say towards the coil 201.

[0198] A current i modulated in amplitude and frequency is injected into the coil 201 carried by the moving assembly, via the electrical tracks 206.

[0199] The application of Maxwell's rule makes it possible to figure the direction of the Lorentz force F controlling the movement of the moving assembly.

[0200] The injection of the current i into the coil 201 thus causes the displacement of the moving assembly along the y axis, and therefore of the coil 201, in the air gap 112 of the magnet assembly 101 in which the radial component Bx of the magnetic field B generated is substantially constant (i.e., a force factor Bl substantially constant at any point of the useful travel of the coil 201 within the air gap 112 of the magnet assembly 101), which allows quality sound reproduction with much less loss and non-linear distortion than conventional loudspeakers.

[0201] The movement of the moving assembly causes a movement of the membrane 202 (movement made possible by means of the flexible arms 204). The membrane 202 then plays the role of emissive surface (or speaking surface or acoustic radiator) and makes it possible to transform the mechanical movement of the moving assembly induced at audible frequency into an acoustic field.

[0202] The motor 207 according to the present invention can be stressed in voltage (in a traditional manner), but is also particularly suitable for being the subject of a current control mode (for a stress regime imposed by an electronic conditioner of the voltage / current converter type).

[0203] If we refer to [Fig. 15], we can see that there is shown there an example curve representing a modeling of the relative invariance of the force factor Bl (in N / A) as a function of the position Ay (in mm) of the coil 201 along the y axis in the electrodynamic loudspeaker motor 207 according to the invention.

[0204] If we consider that the position Ay = 0 corresponds to the rest point of the coil 201, we see that the motor 207 has a large operational zone of the order of 8 mm (ranging approximately from Ay = -4 mm to Ay = 4 mm) over which the force factor Bl is almost invariant at any point of the useful travel of the coil 201 of the moving assembly within the air gap 112 of the magnet assembly 101.

[0205] If we refer to [Fig. 16], we can see that there is shown a top view of the first internal 4 and external 2' magnetic rings of a magnet assembly according to a third embodiment of the present invention.

[0206] The elements common between the first embodiment of the invention in Figures 1 to 6 and this third embodiment of the invention bear the same reference number, and will not be described in more detail here when they are of identical structures.

[0207] The magnet assembly according to the third embodiment is identical to the magnet assembly 1 according to the first embodiment, except that the first external permanent magnets 2a' of the first external magnetic ring 2' are permanent magnets in the shape of a rectangular parallelepiped with magnetization relative to the height.

[0208] Each first permanent magnet in the shape of a rectangular parallelepiped 2a' has a square cross-section and a magnetic field whose flux is in the height direction of the rectangular parallelepiped. The first permanent magnet in rectangular parallelepiped shape 2a' is thus magnetized relative to its height, the north pole of the first permanent magnet in the shape of a rectangular parallelepiped 2a' being located on one of the two ends (upper or lower) of the rectangular parallelepiped, and the south pole of the first permanent magnet in the shape of a rectangular parallelepiped 2a' being located on the other (lower or upper) of the two ends of the rectangular parallelepiped.

[0209] For each of the plurality of first external permanent magnets 2a' arranged in a circle, its height direction is parallel to the central axis of symmetry of the first external magnetic ring 2', and one of its sides is oriented toward the central axis of symmetry of the first external magnetic ring 2'.

[0210] Although not shown in [Fig.16], in this third embodiment, the second external permanent magnets of the second external magnetic ring are also permanent magnets in the shape of a rectangular parallelepiped with magnetization relative to the height, the arrangement of which is similar to that of the first external permanent magnets 2a'.

[0211] Furthermore, the first internal magnetic ring 4 and the second internal magnetic ring 5 in this third embodiment could each be made up of a plurality of permanent magnets arranged in a circle and in the shape of a rectangular parallelepiped with magnetization according to the height, without departing from the scope of the present invention.

[0212] It is understood that the particular embodiments which have just been described have been given for informational and non-limiting purposes, and that modifications may be made without departing from the present invention.

Claims

1. Claims A magnet assembly (1; 101) for an electrodynamic loudspeaker motor, said magnet assembly (1; 101) comprising a first outer pair of magnetic rings and a second inner pair of magnetic rings, each magnetic ring of each of the first and second pairs of magnetic rings having an axial magnetization; the first outer pair of magnetic rings comprising a first outer magnetic ring (2; 2'; 102) and a second outer magnetic ring (3; 103), said first and second outer magnetic rings (2, 3; 2'; 102, 103) being arranged coaxially opposite each other, being spaced apart from each other and having the same dimensions; the second inner pair of magnetic rings comprising a first inner magnetic ring (4; 104) and a second inner magnetic ring (5; 105), said first and second inner magnetic rings (4, 5; 104, 105) being arranged coaxially opposite each other, being spaced apart from each other and having the same dimensions, the first and second inner magnetic rings (4, 5; 104, 105) and the first and second outer magnetic rings (2, 3; 2'; 102, 103) being arranged coaxially, i.e. having the same central axis of symmetry passing through the center of each magnetic ring and perpendicular to the plane of each magnetic ring, the first inner magnetic ring (4; 104) being arranged inside the first outer magnetic ring (2; 2'; 102) and the second inner magnetic ring (5; 105) being arranged inside the second external magnetic crown (3; 103); the magnetization directions of the internal (4, 5; 104, 105) and external (2, 3; 2'; 102, 103) magnetic rings being parallel to their central axis of symmetry and configured such that the north-south magnetic field direction of the first internal magnetic ring (4; 104) is opposite to that of the first external magnetic ring (2; 2'; 102), the north-south magnetic field direction of the first internal magnetic ring (4; 104) is opposite to that of the second internal magnetic ring (5; 105), and the north-south magnetic field direction of the first external magnetic ring (2; 2'; 102) is opposite to that of the second external magnetic crown (3; 103); characterized by the fact that: - the first external magnetic ring (2; 2'; 102) consists of a plurality of identical first external permanent magnets (2a; 2a'; 102a) arranged in a circle, and the second external magnetic ring (3; 103) consists of a plurality of identical second external permanent magnets (3a; 103a) arranged in a circle, the first external permanent magnets (2a; 2a'; 102a) and the second external permanent magnets (3a; 103a) being one of axially magnetized cylindrical permanent magnets and height-magnetized rectangular parallelepiped-shaped permanent magnets; - the magnet assembly (1; 101) further comprises a first outer steel ring (6; 106), a second outer steel ring (7; 107), a first inner steel ring (8; 108) and a second inner steel ring (9; 109) which are arranged coaxially with the first outer pair of magnetic rings and the second inner pair of magnetic rings, the first outer steel ring (6; 106) being in contact with the first outer magnetic ring (2; 2'; 102), the second outer steel ring (7; 107) being in contact with the second outer magnetic ring (3; 103), the first inner steel ring (8; 108) being in contact with the first inner magnetic ring (4; 104), and the second inner steel ring (9; 109) being in contact with the second inner magnetic ring (5; 105); and - the magnet assembly (1; 101) further comprises an external separator (10; 110) arranged between the first and second external steel rings (6, 7; 106, 107) and an internal separator (11; 111) arranged between the first and second internal steel rings (8, 9; 108, 109), such that within the magnet assembly (1; 101), an internal stack successively comprising the first internal magnetic ring (4; 104), the first internal steel ring (8; 108), the internal separator (11; 111), the second internal steel ring (9; 109) and the second internal magnetic ring (5; 105) is formed inside an external stack successively comprising the first external magnetic ring (2; 2'; 102), the first external steel ring (6; 106), the external separator (10; 110), the second ring external steel (7; 107) and the second external magnetic crown (3; 103), with an air gap (12; 112) formed between the internal and external stacks.

2. Magnet assembly (1) according to claim 1, characterized in that the first internal magnetic ring (4) consists of a first annular permanent magnet with axial magnetization, and the second internal magnetic ring (5) consists of a second annular permanent magnet with axial magnetization.

3. A magnet assembly (101) according to claim 1, characterized in that the first internal magnetic ring (104) consists of a plurality of identical first internal permanent magnets (104a) arranged in a circle, and the second internal magnetic ring (105) consists of a plurality of identical second internal permanent magnets (105a) arranged in a circle, the first internal permanent magnets (104a) and the second internal permanent magnets (105a) being one of axially magnetized cylindrical permanent magnets and height-magnetized rectangular parallelepiped-shaped permanent magnets.

4. Magnet assembly (1; 110) according to one of claims 1 to 3, characterized in that the external separator (10; 110) consists of an external separation ring arranged between the first and second external steel rings (6, 7; 106, 107), the external separation ring being made of a non-ferromagnetic material such as aluminum, copper or a polymer.

5. Magnet assembly (1; 110) according to one of claims 1 to 4, characterized in that the internal separator (11; 111) consists of an internal separation ring arranged between the first and second internal steel rings (8, 9; 108, 109), the internal separation ring being made of a non-ferromagnetic material such as aluminum, copper or a polymer.

6. Magnet assembly (1; 101) according to one of claims 1 to 5, characterized in that it further comprises a housing comprising a first housing part (13; 113) and a second housing part (14; 114) configured to be fixed to each other while receiving the internal and external stacks between them.

7. Magnet assembly (1; 101) according to claim 6, characterized in that the first housing part (13; 113) comprises a first internal housing (13a; 113a) configured to receive the first internal magnetic crown (4; 104) and a first external housing consisting of a plurality of first external compartments (14b; 114b) arranged in a circle and configured to respectively receive the plurality of first external permanent magnets (2a; 2a'; 102a) of the first external magnetic crown (2; 2'; 102).

8. Magnet assembly (1; 101) according to claim 6 or 7, characterized in that the second housing part (14; 114) comprises a second internal housing (14a; 114a) configured to receive the second internal magnetic crown (5; 105) and a second external housing consisting of a plurality of second external compartments (14b; 114b) arranged in a circle and configured to respectively receive the plurality of second external permanent magnets (3a; 103a) of the second external magnetic crown (3; 103).

9. Magnet assembly (1; 101) according to claim 7 or according to claim 8 as dependent on claim 7, characterized in that the first housing part (13; 113) further comprises a barrel (13c; 113c) extending axially from the first internal housing (13a; 113a) and around which the first internal magnetic crown (4; 104), the first internal steel ring (8; 108), the internal separator (11; 111), the second internal steel ring (9; 109) and the second internal magnetic crown (5; 105) are capable of being successively stacked.

10. Magnet assembly (101) according to claim 9 in dependence on claim 3, characterized in that a plurality of internal compartments (116) are formed, being arranged in a circle, at the periphery of the barrel (113c) of the first housing part (113), said plurality of internal compartments (116) serving, at the base of the barrel (113c), as a first internal housing (113a) configured to receive the plurality of first internal permanent magnets (104a) of the first internal magnetic ring (104) and also, at the free end of the barrel (113c), as an additional internal housing configured to receive the plurality of second internal permanent magnets (105a) of the second internal magnetic ring (105).

11. Magnet assembly (101) according to one of claims 6 to 10, characterized in that at least one of the first housing part (113) and the second housing part (114) has interior channels (117a, 117b, 117c) configured to allow an exchange of air with the exterior.

12. Motor (207) for an electrodynamic loudspeaker comprising a magnet assembly (1; 101) according to one of claims 1 to 11 and a moving assembly comprising a cylindrical coil support (200) which is partly inserted into the air gap (12; 112) of the magnet assembly (1; 101) and on which is wound a coil (201) arranged in the air gap (12; 112) of the magnet assembly (1; 101).

13. Electrodynamic loudspeaker comprising a chassis (203) on which are arranged a motor (207) according to claim 12 and a membrane (202) connected to the moving assembly of the motor (207).

Images