EP3892011A1 - Infinite baffle with low stiffness - Google Patents

Infinite baffle with low stiffness

Info

Publication number
EP3892011A1
EP3892011A1 EP19809862.6A EP19809862A EP3892011A1 EP 3892011 A1 EP3892011 A1 EP 3892011A1 EP 19809862 A EP19809862 A EP 19809862A EP 3892011 A1 EP3892011 A1 EP 3892011A1
Authority
EP
European Patent Office
Prior art keywords
cam
membrane
box
axis
diaphragm
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP19809862.6A
Other languages
German (de)
French (fr)
Other versions
EP3892011B1 (en
Inventor
Eduardo MENDES
Bérenger Roig
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Devialet SA
Original Assignee
Devialet SA
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Devialet SA filed Critical Devialet SA
Publication of EP3892011A1 publication Critical patent/EP3892011A1/en
Application granted granted Critical
Publication of EP3892011B1 publication Critical patent/EP3892011B1/en
Active legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R1/00—Details of transducers, loudspeakers or microphones
    • H04R1/20—Arrangements for obtaining desired frequency or directional characteristics
    • H04R1/22—Arrangements for obtaining desired frequency or directional characteristics for obtaining desired frequency characteristic only 
    • H04R1/28—Transducer mountings or enclosures modified by provision of mechanical or acoustic impedances, e.g. resonator, damping means
    • H04R1/2807—Enclosures comprising vibrating or resonating arrangements
    • H04R1/2811—Enclosures comprising vibrating or resonating arrangements for loudspeaker transducers
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R1/00—Details of transducers, loudspeakers or microphones
    • H04R1/02—Casings; Cabinets ; Supports therefor; Mountings therein
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R1/00—Details of transducers, loudspeakers or microphones
    • H04R1/42—Combinations of transducers with fluid-pressure or other non-electrical amplifying means
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R11/00—Transducers of moving-armature or moving-core type
    • H04R11/02—Loudspeakers
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R7/00—Diaphragms for electromechanical transducers; Cones
    • H04R7/16—Mounting or tensioning of diaphragms or cones
    • H04R7/18—Mounting or tensioning of diaphragms or cones at the periphery
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R7/00—Diaphragms for electromechanical transducers; Cones
    • H04R7/26—Damping by means acting directly on free portion of diaphragm or cone
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R9/00—Transducers of moving-coil, moving-strip, or moving-wire type
    • H04R9/06—Loudspeakers
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R2400/00—Loudspeakers
    • H04R2400/11—Aspects regarding the frame of loudspeaker transducers

Definitions

  • the present invention comprises an enclosed acoustic enclosure of the type comprising a box and a loudspeaker comprising a membrane movable relative to the box, the box and the membrane delimiting an essentially closed chamber; the loudspeaker comprising an electrically controlled motor for actuating the diaphragm movable relative to the box, the enclosure further comprising an axial biasing mechanism for the diaphragm away from its median position of rest against of the pressure force exerted by the gas contained in the box on the membrane.
  • the sound produced by a loudspeaker is obtained by the displacement of a mobile membrane.
  • This membrane has its own resonant frequency linked to its mass and the stiffness of its suspensions which give it mobility.
  • the force necessary for the displacement of the oscillatory acceleration membrane of constant amplitude is almost constant.
  • the force necessary for the displacement of the membrane with oscillatory acceleration of constant amplitude increases strongly as the frequency of the oscillatory movements decreases due to the preponderant part of the stiffness of the suspensions. relative to mass.
  • the speakers' designers sought to obtain a frequency of mechanical resonance of the membrane of the loudspeaker, with its suspensions, the smallest possible because this resonant frequency fixes the frequency of low use of the loudspeaker.
  • the acoustic performance of a loudspeaker in the open air is reduced due to the acoustic short circuit linked to the reciprocal cancellation of the "front" and "rear” waves produced by the diaphragm of the speaker.
  • the speakers are most often placed in boxes so that only a single wave produced by the membrane, for example the front wave produced by the front of the membrane, is diffused.
  • the opposite wave is confined within the enclosure.
  • the frequency of mechanical resonance of the membrane increases as the internal volume of the box decreases. This is due to the compression / decompression of the air inside the box during the oscillatory movements of the membrane. Indeed, the compression / decompression of the air behaves like a non-linear spring whose stiffness depends on the volume of the box and the amplitude of the displacement of the membrane. Due to this increase in the resonant frequency of the speaker due to the decrease in volume of the box in which it is placed, speaker manufacturers are forced to use large speakers in order to obtain sound reproduction at low frequencies at high sound volumes because the displacement of the membrane will be as high as the frequency of the sound to be reproduced will be low.
  • document US 2,810,021 describes a loudspeaker in which the membrane is linked to a rod axially stressed by helical springs arranged radially and connected to the axial rod by an elastically deformable blade in the form of a cup.
  • the object of the invention is to provide an acoustic enclosure the production of the anti-spring mechanism of which is facilitated, and the value of the force applied by this mechanism being well controlled regardless of the position of the membrane.
  • the subject of the invention is an acoustic enclosure of the aforementioned type, characterized in that the mechanism comprises a cam movable relative to the box along an axis of displacement of the cam under the action of displacement of the membrane and to at least one cam follower biased transversely to the cam by at least one spring and bearing on the cam, the cam having at least one cam surface capable of converting the transverse force of the or each spring into an axial force on the cam whose the intensity varies according to the position of the cam relative to the box.
  • the acoustic enclosure includes one or more of the following characteristics: -
  • the cam is linked to the speaker membrane by a rod extending along the axis of movement of the membrane;
  • the cam is connected to a movable wall relative to the box, the movable wall defining with the box a substantially closed rear chamber and a substantially closed front chamber partially delimited by the diaphragm of the loudspeaker;
  • the cam comprises at least two cam surfaces distributed angularly around the axis (of displacement of the cam and the axial biasing mechanism of the membrane comprises for each cam surface a cam followers biased towards the axis of displacement of the cam and the cam being sandwiched between the cam followers;
  • the or each cam follower comprises a rotary element suitable for rolling on the cam
  • each cam follower is carried by a pre-stressed elastic arm extending in a plane transverse to the axis;
  • the cam has a range whose distance to the axis of movement of the cam 54 is locally constant along the axis of movement of the cam, this range being in contact with the or each cam follower when the membrane is in position rest so that no force is applied by the cam to the diaphragm by the cam in this diaphragm rest position;
  • the cam has on an inclined range relative to the axis of movement of the cam.
  • the inclination of the cam surface along the inclined range is gradually increasing along the axis of movement of the cam away from the zone of contact with the cam follower when the diaphragm is in the rest position so that the cam imposes an increasing intensity force on the membrane as the membrane moves away from its rest position.
  • Figure 1 is a longitudinal section view of an enclosure according to a first embodiment of the invention
  • Figure 2 is a partial sectional view of the cam and the roller of the anti-spring mechanism of the enclosure of Figure 1;
  • Figure 3 is a view identical to that of Figure 1 of an alternative embodiment of an enclosure according to the invention.
  • FIG. 1 is a closed enclosure. It comprises a box 12 delimiting a chamber 14 essentially closed separated from the external environment.
  • the box 12 comprises rigid and impermeable walls connected to each other.
  • a calibrated decompression vent 16 is provided through a wall to allow a pressure balance between the interior and the exterior of the enclosure during slow variations in atmospheric pressure. This decompression vent 16 is small enough to avoid the circulation of air from and to the chamber 14 during operation of the enclosure and in particular during movements of the speaker membrane.
  • the enclosure comprises a loudspeaker 20 comprising a membrane 22 movable through a hole in the box.
  • the membrane 22 locally delimits the chamber 14 and seals it.
  • the membrane 12 is connected to the side walls of the box by a deformable waterproof seal 24.
  • the loudspeaker comprises a motor 30 with electric actuation for actuating the membrane 22 for its displacement along an axis X-X.
  • the motor essentially comprises an electromagnet, having a carcass 32 secured to the casing 12 by link arms 34 and a coil 36 carried by a movable assembly 38 at the end of which the membrane 22 is carried.
  • the coil 36 is connected, as known per se to terminals 39 for connecting the acoustic enclosure to an amplifier.
  • the moving element 38 is guided relative to the box 12 for movement along the axis X-X by an elastic joint formed by an elastic and breathable corrugated textile plate 41 known as a spider.
  • This textile structure delimits air circulation passages making it possible to balance the pressures on both sides of the spider.
  • the enclosure 10 includes an anti-spring mechanism 50 acting on the membrane 22 and capable of compensating for the effect of the variations in air pressure in the chamber 14 during movements of the membrane 22.
  • the anti-spring mechanism 50 is an elastic mechanism for axially biasing the membrane 22 away from its median position of rest against the pressure force exerted by the air contained in the box on the membrane, that is to say in the direction of movement of the membrane.
  • the mechanism 50 comprises a rod 52, extending along the axis XX, connected, at one end, to the mobile assembly 38 carrying the membrane 22 and, at its other end, to a cam 54 movable relative to the box 12.
  • the rod 52 is thus driven by the movable assembly 38.
  • the rod 52 passes axially through the actuator motor 30 of the loudspeaker.
  • the cam 54 is generally of X-X axis revolution. It has a continuous cam surface of revolution forming in a plane passing through the axis X-X two diametrically opposed cam surfaces 56A, 56B. These cam surfaces are axisymmetric with respect to the X-X axis.
  • the cam 54 is clamped between two cam followers 58A, 58B biased transversely to the axis X-X by springs 60A, 60B holding the cam followers in contact with the cam surfaces 56A, 56B.
  • the cam followers 58A, 58B each advantageously comprise a rotary element 62A, 62B such as a roller suitable for rolling along the length of the cam surfaces 56A, 56B.
  • the axis of rotation of the rollers extends perpendicular to the axis X-X.
  • the rollers 62A, 62B have a diabolo shape, with a concave surface complementary to the cylindrical surface of the cam 54.
  • the springs 60A, 60B extend transversely to the cam surfaces. They are coaxial from axis Y-Y intersecting to axis X-X. These springs, kept constantly compressed and bear at one end on the box 12 and at their other end on the axis of the rotary rollers 62A, 62B forming the cam followers.
  • An additional spider 70, formed between the cam 54 and the actuation motor 32 ensures the axial guidance of the rod 52 and of the cam 54 to ensure a displacement of the latter along the axis X.X.
  • the spider 70 is permeable to gas.
  • the cam surfaces 56A, 56B have in the middle part, along the length of the axis XX and in section along the path of travel of the rollers, a range 72 whose distance from the axis XX of movement of the cam is locally constant along the axis X- X of displacement of the cam.
  • This range 72 extends over a few tenths of a millimeter along the X-X axis.
  • This median range 72 is positioned on the cam so that each roller presses on this median range when the membrane 22 is in the rest position, that is to say in a median position between the two extreme positions which can be occupied under the motor action 30.
  • the cam surfaces 56A, 56B have areas 74 inclined relative to the axis XX.
  • the inclination of these ranges increases by deviating along the axis XX on either side of this median range so that when the cam followers deviate from the median zone, the angle between the axis XX and the normal at the point of contact of the roller on the cam surface increases so that the force applied to the diaphragm increases.
  • the distance between the axis X-X and a point on the cam surface decreases while deviating from the median range 72.
  • the cam surfaces converge away from the median zone.
  • the speaker illustrated in Figure 1 operates as follows.
  • the membrane 22 moves as known per se.
  • the cam 54 driven by the diaphragm, moves axially relative to the cam followers 58A, 58B.
  • the cam followers then exert a force directed along the Y-Y axis toward the X-X axis on the cam surfaces 56A, 56B.
  • These cam surfaces being inclined and maintained along the axis Y-Y between the two rollers, the cam surface is subjected to an axial force, which is applied to the membrane 22 through the rod 52.
  • the cam 54 is moved away from the membrane 22. Under the action of the springs 60A, 60B acting at the through cam followers 62A, 62B, the cam 54 is biased in its direction of movement.
  • the overpressure in the enclosure 14 acts on the membrane 22 to take the membrane 22 out of the box 12.
  • the cam 54 produces a return force of the membrane 22 inside the box.
  • the shape of the cam 54 is adapted so that the sum of the two forces produced by the cam and that resulting from the overpressure in the chamber 14 vanishes practically at any point of the cam or is equal to a desired value in all point of the cam.
  • the shape of the cam surface makes it possible to transform part of a force F Rz exerted by the springs 60A and 60B along the axis YY into a force F Rx along the axis XX.
  • the membrane 22 undergoes, during its displacement, a force F Rx , by means of the rod 52, along the axis XX in the same direction as that of the displacement .
  • the amplitude of this force depends on the angle formed by the surface of the cam 54 with the axis XX at the point of contact of the rollers 62A, 62B.
  • This force is of the form:
  • the stiffness K R (x) is negative because it produces a force in the same direction as the displacement of the membrane.
  • the shape of the cam 52 is chosen so that whatever the position x of the membrane, the sum of the stiffnesses K m (x) + K air (x) + K R (x) is close to the desired value K min .
  • F AR the resonant frequency of the moving mechanical system
  • M is the mass of the moving element 38, the winding 36, the membrane 22 and in part the seals 24 and 41;
  • M AR is the moving mass of the rod 52, the cam 54 is partly the seal 70.
  • the force F T is opposed to the movement of the Force moving part to the right with positive movement of the moving part to the left.
  • Profile 4 of the cam is given by the function expressing y BC as a function of x BC .
  • K min ⁇ K m (x) + K air (x) makes it possible to choose the value of the mechanical resonance frequency F AR of the loudspeaker placed in a closed box.
  • F AR the mechanical resonance frequency
  • the value of F AR will be between 30 Hz and 50 Hz.
  • the additional mass M AR provided by the anti-spring mechanism is reduced to the maximum in order to minimize the force, and therefore the current, necessary for the displacement of the membrane beyond the resonant frequency.
  • FIG. 3 illustrates another embodiment of a closed acoustic enclosure according to the invention.
  • the cam 54 is not connected to the movable assembly by a rod 52.
  • the cam 54 is connected to a movable wall 102, separating in the box 12, the closed chamber 14 in a front chamber 104 partially delimited by the membrane 22 and the movable wall 102 and a rear chamber 106 delimited by the walls of the box 12 and by the movable wall 102.
  • the movable wall 102 is a rigid and impermeable wall connected to the walls of the box 12 by a flexible gas-tight joint 108.
  • the wall 102 extends perpendicular to the axis XX of movement of the cam 54.
  • the same rear chamber 106 is provided for two or more of two speakers whose membranes define the same front chamber 104 separated from the rear chamber in a single wall 102.
  • a calibrated decompression vent 1 14, 1 16 connects the front chamber 104 and the rear chamber 106 to the outside environment. These vents are small enough to avoid the circulation of air during the movement of the membrane 22, but are capable of ensuring pressure balancing between the exterior and the interior of the box during variations in atmospheric pressure.
  • the wall 102 moves due to the vacuum or compression in the front chamber 104.
  • the cam 54 is moved and produced, under the action of the cam followers 58A, 58B, a force applied to the wall 102.
  • This force is contrary to the effect of the pressure acting on the same wall 102 and therefore oriented in the direction of movement of the wall 102.
  • This force is transmitted to the membrane 22 via the gas trapped in the front chamber 104.
  • the stiffness of the compression of the gas in the front chamber 104 is compensated by the force applied by the cam 56 of the axial biasing mechanism 50.
  • the profile of the cam 54 is identical to the profile described with regard to the preceding figures.
  • the cam 54 is enclosed between rollers 202A, 202B, 202C, regularly angularly distributed around the axis XX. These rollers are carried at the free end of elastic arms 204A, 204B, 204C. These elastic arms are each fixed at their other end on a rigid structure 206, itself integral with the box 14.
  • the arms 204A, 204B, 204C extend perpendicular to the axis X-X in the same plane. They are offset transversely to the X-X axis.
  • the rollers 202A, 202B, 202C are mounted to rotate in the extension of the axis of the arms 204A, 204B, 204C respectively, and along the axis of the arms. They are suitable for rolling along the surface of the cam 54 along the axis X-X.
  • the arms 204A, 204B, 204C are prestressed so as to ensure permanent contact between the rollers 202A, 202B, 202C and the cam 54, regardless of the position of the rollers along the length of the cam 54 considered along the axis X-X.
  • the presence of three rotary elements angularly distributed around the axis XX ensures satisfactory guiding of the cam 54 along the axis X- X.
  • the presence of elastic pre-stressed arms deformable in bending ensures a relatively constant force rollers 202A, 202B, 202C on the cam, whatever their position and avoids blocking of the rollers.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Acoustics & Sound (AREA)
  • Signal Processing (AREA)
  • Multimedia (AREA)
  • Health & Medical Sciences (AREA)
  • Otolaryngology (AREA)
  • Electromagnetism (AREA)
  • Audible-Bandwidth Dynamoelectric Transducers Other Than Pickups (AREA)
  • Details Of Audible-Bandwidth Transducers (AREA)
  • Reciprocating Pumps (AREA)

Abstract

Infinite acoustic baffle (10) having a box (12) and a loudspeaker (20) having a membrane (22) that is able to move with respect to the box (12), the box (12) and the membrane (22) delimiting a substantially closed baffle chamber (14); the loudspeaker (20) having an electrically controlled motor (30) for actuating the membrane (22) that is able to move with respect to the box (12), the baffle also having a mechanism (50) for axially urging the membrane (22) away from its median rest position counter to the pressure force exerted on the membrane (22) by the gas contained in the box (12), characterized in that the mechanism (50) has a cam (54) that is movable relative to the box (12) along an axis (X-X) for displacing the cam under the displacement action of the membrane (22), and at least one cam follower (58A, 58B) that is biased transversely to the cam (54) by at least one spring (60A, 60B) and bears on the cam (54), the cam (54) having at least one cam surface (56A, 56B) capable of converting the transverse force of the or each spring (60A, 60B) into an axial force on the cam (54), the intensity of which varies depending on the position of the cam (54) with respect to the box (12).

Description

TITRE : Enceinte close à faible raideur La présente invention comporte une enceinte acoustique close du type comportant un caisson et un haut-parleur comportant une membrane mobile par rapport au caisson, le caisson et la membrane délimitant une chambre essentiellement close ; le haut-parleur comportant un moteur à commande électrique d’actionnement de la membrane mobile par rapport au caisson, l’enceinte comportant en outre un mécanisme de sollicitation axiale de la membrane à l’écart de sa position médiane de repos à l’encontre de la force de pression exercée par le gaz contenu dans le caisson sur la membrane. TITLE: Enclosed enclosure with low stiffness The present invention comprises an enclosed acoustic enclosure of the type comprising a box and a loudspeaker comprising a membrane movable relative to the box, the box and the membrane delimiting an essentially closed chamber; the loudspeaker comprising an electrically controlled motor for actuating the diaphragm movable relative to the box, the enclosure further comprising an axial biasing mechanism for the diaphragm away from its median position of rest against of the pressure force exerted by the gas contained in the box on the membrane.
Le son produit par un haut-parleur est obtenu par le déplacement d’une membrane mobile. Cette membrane a une fréquence de résonance propre liée à sa masse et à la raideur de ses suspensions qui lui confèrent la mobilité. En première approximation, pour des fréquences de déplacements oscillatoires de la membrane au-delà de sa fréquence de résonance mécanique, la force nécessaire au déplacement de la membrane à accélération oscillatoire d’amplitude constante est quasi-constante. Par contre, en-deçà de sa fréquence de résonance mécanique, la force nécessaire au déplacement de la membrane à accélération oscillatoire d’amplitude constante croît fortement à mesure que la fréquence des mouvements oscillatoires diminue en raison de la part prépondérante de la raideur des suspensions par rapport à la masse. Ainsi, les concepteurs de haut- parleurs ont cherché à obtenir une fréquence de résonnance mécanique de la membrane du haut-parleur, avec ses suspensions, la plus petite possible car cette fréquence de résonance fixe la fréquence d’utilisation basse du haut-parleur. The sound produced by a loudspeaker is obtained by the displacement of a mobile membrane. This membrane has its own resonant frequency linked to its mass and the stiffness of its suspensions which give it mobility. As a first approximation, for frequencies of oscillatory displacements of the membrane beyond its mechanical resonance frequency, the force necessary for the displacement of the oscillatory acceleration membrane of constant amplitude is almost constant. On the other hand, below its mechanical resonance frequency, the force necessary for the displacement of the membrane with oscillatory acceleration of constant amplitude increases strongly as the frequency of the oscillatory movements decreases due to the preponderant part of the stiffness of the suspensions. relative to mass. Thus, the speakers' designers sought to obtain a frequency of mechanical resonance of the membrane of the loudspeaker, with its suspensions, the smallest possible because this resonant frequency fixes the frequency of low use of the loudspeaker.
Le rendement acoustique d’un haut-parleur à l’air libre est réduit en raison du court-circuit acoustique liée à l’annulation réciproque des ondes « avant » et « arrière » produites par la membrane du haut-parleur. Pour éviter cette annulation, les haut-parleurs sont le plus souvent placés dans des caissons de telle sorte qu’uniquement une seule onde produite par la membrane, par exemple l’onde avant produite par l’avant de la membrane, soit diffusée. L’onde opposée est confinée dans l’enceinte. The acoustic performance of a loudspeaker in the open air is reduced due to the acoustic short circuit linked to the reciprocal cancellation of the "front" and "rear" waves produced by the diaphragm of the speaker. To avoid this cancellation, the speakers are most often placed in boxes so that only a single wave produced by the membrane, for example the front wave produced by the front of the membrane, is diffused. The opposite wave is confined within the enclosure.
Dans le cas d’une enceinte close, la fréquence de résonance mécanique de la membrane augmente à mesure que le volume interne de la boîte diminue. Ceci est dû à la compression/décompression de l’air interne au caisson lors des mouvements oscillatoires de la membrane. En effet, la compression/décompression de l’air se comporte comme un ressort non-linéaire dont la raideur dépend du volume de la boîte et de l’amplitude du déplacement de la membrane. En raison, de cette augmentation de la fréquence de résonance du haut-parleur en raison de la diminution du volume de la boîte dans laquelle il est placé, les fabricants d’enceintes sont contraints d’utiliser des enceintes de grandes dimensions afin d’obtenir une reproduction sonore en basses fréquences à des volumes sonores élevés car le déplacement de la membrane sera d’autant élevé que la fréquence du son à reproduire sera basse. In the case of a closed enclosure, the frequency of mechanical resonance of the membrane increases as the internal volume of the box decreases. This is due to the compression / decompression of the air inside the box during the oscillatory movements of the membrane. Indeed, the compression / decompression of the air behaves like a non-linear spring whose stiffness depends on the volume of the box and the amplitude of the displacement of the membrane. Due to this increase in the resonant frequency of the speaker due to the decrease in volume of the box in which it is placed, speaker manufacturers are forced to use large speakers in order to obtain sound reproduction at low frequencies at high sound volumes because the displacement of the membrane will be as high as the frequency of the sound to be reproduced will be low.
Pour résoudre ce problème général, il est connu de lier la membrane à un mécanisme dit anti-ressort de manière à réduire la valeur de la raideur équivalente vue par la membrane. To solve this general problem, it is known to link the membrane to a so-called anti-spring mechanism so as to reduce the value of the equivalent stiffness seen by the membrane.
Avec ce mécanisme anti-ressort, il est possible de réaliser des enceintes closes de volume interne réduit ayant des fréquences de résonance de la membrane suffisamment basses afin de reproduire des fréquences sonores de basses fréquences. With this anti-spring mechanism, it is possible to produce closed enclosures of reduced internal volume having sufficiently low resonance frequencies of the membrane in order to reproduce low frequency sound frequencies.
Pour créer ce mécanisme anti-ressort, différentes solutions ont été proposées, notamment des solutions mettant en oeuvre des pompes pour équilibrer les pressions interne et externe à l’enceinte, ou encore des lames élastiques appliquées sur la membrane du haut-parleur. To create this anti-spring mechanism, various solutions have been proposed, in particular solutions using pumps to balance the pressures internal and external to the enclosure, or else elastic blades applied to the diaphragm of the speaker.
Par exemple, le document US 2 810 021 décrit un haut-parleur dans lequel la membrane est liée à une tige sollicitée axialement par des ressorts hélicoïdaux disposés radialement et reliés à la tige axiale par une lame déformable élastiquement en forme de coupelle. For example, document US 2,810,021 describes a loudspeaker in which the membrane is linked to a rod axially stressed by helical springs arranged radially and connected to the axial rod by an elastically deformable blade in the form of a cup.
La mise au point d’un tel mécanisme est particulièrement complexe notamment puisqu’il est très délicat de dimensionner les ressorts et la coupelle ainsi que les moyens de liaison afin de faire que le mécanisme anti-ressort puisse appliquer une force de valeur souhaitée pour chaque position de la membrane. The development of such a mechanism is particularly complex in particular since it is very delicate to size the springs and the cup as well as the connecting means in order to make that the anti-spring mechanism can apply a desired value force for each position of the membrane.
L’invention a pour but de proposer une enceinte acoustique dont la réalisation du mécanisme anti-ressort est facilitée, et dont la valeur de la force appliquée par ce mécanisme est bien maîtrisée quelle que soit la position de la membrane. The object of the invention is to provide an acoustic enclosure the production of the anti-spring mechanism of which is facilitated, and the value of the force applied by this mechanism being well controlled regardless of the position of the membrane.
A cet effet, l’invention a pour objet une enceinte acoustique du type précité, caractérisée en ce que le mécanisme comporte une came mobile par rapport au caisson suivant un axe de déplacement de la came sous l’action de déplacement de la membrane et au moins un suiveur de came sollicité transversalement à la came par au moins un ressort et en appui sur la came, la came présentant au moins une surface de came propre à convertir l’effort transversal du ou chaque ressort en un effort axial sur la came dont l’intensité varie en fonction de la position de la came par rapport au caisson. To this end, the subject of the invention is an acoustic enclosure of the aforementioned type, characterized in that the mechanism comprises a cam movable relative to the box along an axis of displacement of the cam under the action of displacement of the membrane and to at least one cam follower biased transversely to the cam by at least one spring and bearing on the cam, the cam having at least one cam surface capable of converting the transverse force of the or each spring into an axial force on the cam whose the intensity varies according to the position of the cam relative to the box.
Suivant des modes particuliers de réalisation, l’enceinte acoustique comporte l’une ou plusieurs des caractéristiques suivantes : - la came est liée à la membrane du haut-parleur par une tige s’étendant suivant l’axe de déplacement de la membrane ; According to particular embodiments, the acoustic enclosure includes one or more of the following characteristics: - The cam is linked to the speaker membrane by a rod extending along the axis of movement of the membrane;
- elle comporte un joint élastique de guidage reliant la tige au caisson ; - It includes an elastic guide seal connecting the rod to the box;
- la came est reliée à une paroi mobile par rapport au caisson, la paroi mobile délimitant avec le caisson une chambre arrière essentiellement close et une chambre avant essentiellement close délimitée partiellement par la membrane du haut-parleur ; - The cam is connected to a movable wall relative to the box, the movable wall defining with the box a substantially closed rear chamber and a substantially closed front chamber partially delimited by the diaphragm of the loudspeaker;
- la came comporte au moins deux surfaces de came réparties angulairement autour de l’axe (de déplacement de la came et le mécanisme de sollicitation axiale de la membrane comporte pour chaque surface de came un suiveurs de came sollicités vers l’axe de déplacement de la came et la came étant enserrée entre les suiveurs de came ; - the cam comprises at least two cam surfaces distributed angularly around the axis (of displacement of the cam and the axial biasing mechanism of the membrane comprises for each cam surface a cam followers biased towards the axis of displacement of the cam and the cam being sandwiched between the cam followers;
- le ou chaque suiveur de came comporte un élément rotatif propre à rouler sur la came ; - The or each cam follower comprises a rotary element suitable for rolling on the cam;
- le ou chaque suiveur de came est porté par un bras élastique précontraint s’étendent dans un plan transversal à l’axe ; - the or each cam follower is carried by a pre-stressed elastic arm extending in a plane transverse to the axis;
- la came comporte une plage dont la distance à l’axe de déplacement de la came 54 est localement constante suivant l’axe de déplacement de la came, cette plage étant en contact avec le ou chaque suiveur de came lorsque la membrane est en position de repos de sorte qu’aucune force ne soit appliquée par la came sur la membrane par la came dans cette position de repos de la membrane ; - The cam has a range whose distance to the axis of movement of the cam 54 is locally constant along the axis of movement of the cam, this range being in contact with the or each cam follower when the membrane is in position rest so that no force is applied by the cam to the diaphragm by the cam in this diaphragm rest position;
- la came comporte sur une plage inclinée par rapport à l’axe de déplacement de la came. - The cam has on an inclined range relative to the axis of movement of the cam.
- l’inclinaison de la surface de came suivant la plage inclinée est progressivement croissante suivant l’axe de déplacement de la came à l’écart de la zone de contact avec le suiveur de came lorsque la membrane est en position de repos de sorte que la came impose une force d’intensité croissante à la membrane au fur et à mesure du déplacement de la membrane à l’écart de sa position de repos. the inclination of the cam surface along the inclined range is gradually increasing along the axis of movement of the cam away from the zone of contact with the cam follower when the diaphragm is in the rest position so that the cam imposes an increasing intensity force on the membrane as the membrane moves away from its rest position.
L’invention sera mieux comprise à la lecture de la description qui va suivre, donnée uniquement à titre d’exemple et faite en se référant aux dessins sur lesquels : The invention will be better understood on reading the description which follows, given solely by way of example and made with reference to the drawings in which:
- [Fig 1] la figure 1 est une vue en section longitudinale d’une enceinte selon un premier mode de réalisation de l’invention ; - [Fig 1] Figure 1 is a longitudinal section view of an enclosure according to a first embodiment of the invention;
- [Fig 2] la figure 2 est une vue en section partielle de la came et du galet du mécanisme anti-ressort de l’enceinte de la figure 1 ; - [Fig 2] Figure 2 is a partial sectional view of the cam and the roller of the anti-spring mechanism of the enclosure of Figure 1;
- [Fig 3] la figure 3 est une vue identique à celle de la figure 1 d’une variante de réalisation d’une enceinte selon l’invention ; et - [Fig 3] Figure 3 is a view identical to that of Figure 1 of an alternative embodiment of an enclosure according to the invention; and
- [Fig 4] la figure 4 est une vue en perspective d’une variante de réalisation d’un mécanisme anti-ressort d’une enceinte selon l’invention. L’enceinte acoustique 10 illustrée sur la figure 1 est une enceinte close. Elle comporte un caisson 12 délimitant une chambre 14 essentiellement close séparée de l’environnement extérieur. - [Fig 4] Figure 4 is a perspective view of an alternative embodiment of an anti-spring mechanism of an enclosure according to the invention. The acoustic enclosure 10 illustrated in FIG. 1 is a closed enclosure. It comprises a box 12 delimiting a chamber 14 essentially closed separated from the external environment.
Le caisson 12 comprend des parois rigides et imperméables reliées les unes aux autres. Un évent de décompression calibré 16 est ménagé au travers d’une paroi pour permettre un équilibre des pressions entre l’intérieur et l’extérieur de l’enceinte lors des variations lentes de pression atmosphérique. Cet évent de décompression 16 est suffisamment petit pour éviter la circulation d’air depuis et vers la chambre 14 lors du fonctionnement de l’enceinte et notamment lors des mouvements de la membrane du haut-parleur. The box 12 comprises rigid and impermeable walls connected to each other. A calibrated decompression vent 16 is provided through a wall to allow a pressure balance between the interior and the exterior of the enclosure during slow variations in atmospheric pressure. This decompression vent 16 is small enough to avoid the circulation of air from and to the chamber 14 during operation of the enclosure and in particular during movements of the speaker membrane.
Comme connu en soi, l’enceinte comporte un haut-parleur 20 comportant une membrane 22 mobile au travers d’un trou du caisson. La membrane 22 délimite localement la chambre 14 et assure l’étanchéité de celle-ci. La membrane 12 est reliée aux parois latérales du caisson par un joint étanche déformable 24. As known per se, the enclosure comprises a loudspeaker 20 comprising a membrane 22 movable through a hole in the box. The membrane 22 locally delimits the chamber 14 and seals it. The membrane 12 is connected to the side walls of the box by a deformable waterproof seal 24.
Le haut-parleur comporte un moteur 30 à commande électrique d’actionnement de la membrane 22 pour son déplacement suivant un axe X-X. Comme connu en soi, le moteur comporte essentiellement un électro-aimant, ayant une carcasse 32 solidarisée au caisson 12 par des bras de liaison 34 et un bobinage 36 porté par un équipage mobile 38 à l’extrémité de laquelle est portée la membrane 22. The loudspeaker comprises a motor 30 with electric actuation for actuating the membrane 22 for its displacement along an axis X-X. As known per se, the motor essentially comprises an electromagnet, having a carcass 32 secured to the casing 12 by link arms 34 and a coil 36 carried by a movable assembly 38 at the end of which the membrane 22 is carried.
Le bobinage 36 est relié, comme connu en soi à des bornes 39 de connexion de l’enceinte acoustique à un amplificateur. The coil 36 is connected, as known per se to terminals 39 for connecting the acoustic enclosure to an amplifier.
L’équipage mobile 38 est guidé par rapport au caisson 12 pour un déplacement suivant l’axe X-X par un joint élastique formé d’une plaque textile ondulée élastique et perméable à l’air 41 connue sous le nom de spider. Cette structure textile délimite des passages de circulation d’air permettant d’équilibrer les pressions de part et d’autre du spider. The moving element 38 is guided relative to the box 12 for movement along the axis X-X by an elastic joint formed by an elastic and breathable corrugated textile plate 41 known as a spider. This textile structure delimits air circulation passages making it possible to balance the pressures on both sides of the spider.
L’enceinte 10 comporte un mécanisme anti-ressort 50 agissant sur la membrane 22 et propre à compenser l’effet des variations de pression de l’air dans la chambre 14 lors des mouvements de la membrane 22. The enclosure 10 includes an anti-spring mechanism 50 acting on the membrane 22 and capable of compensating for the effect of the variations in air pressure in the chamber 14 during movements of the membrane 22.
Dans ce mode de réalisation, le mécanisme anti-ressort 50 est un mécanisme élastique de sollicitation axiale de la membrane 22 à l’écart de sa position médiane de repos à l’encontre de la force de pression exercée par l’air contenu dans le caisson sur la membrane, c’est-à-dire suivant le sens de déplacement de la membrane. In this embodiment, the anti-spring mechanism 50 is an elastic mechanism for axially biasing the membrane 22 away from its median position of rest against the pressure force exerted by the air contained in the box on the membrane, that is to say in the direction of movement of the membrane.
Le mécanisme 50 comporte une tige 52, s’étendant suivant l’axe X-X, reliée, à une extrémité, à l’équipage mobile 38 portant la membrane 22 et, à son autre extrémité, à une came 54 mobile par rapport au caisson 12. La tige 52 est ainsi entraînée par l’équipage mobile 38. The mechanism 50 comprises a rod 52, extending along the axis XX, connected, at one end, to the mobile assembly 38 carrying the membrane 22 and, at its other end, to a cam 54 movable relative to the box 12. The rod 52 is thus driven by the movable assembly 38.
La tige 52 traverse axialement le moteur d’actionnement 30 du haut-parleur. The rod 52 passes axially through the actuator motor 30 of the loudspeaker.
La came 54 est généralement de révolution d’axe X-X. Elle présente une surface de came continue de révolution formant dans un plan passant par l’axe X-X deux surfaces de came diamétralement opposées 56A, 56B. Ces surfaces de came sont axisymétriques par rapport à l’axe X-X. The cam 54 is generally of X-X axis revolution. It has a continuous cam surface of revolution forming in a plane passing through the axis X-X two diametrically opposed cam surfaces 56A, 56B. These cam surfaces are axisymmetric with respect to the X-X axis.
La came 54 est enserrée entre deux suiveurs de came 58A, 58B sollicités transversalement à l’axe X-X par des ressorts 60A, 60B maintenant les suiveurs de came au contact des surfaces de came 56A, 56B. The cam 54 is clamped between two cam followers 58A, 58B biased transversely to the axis X-X by springs 60A, 60B holding the cam followers in contact with the cam surfaces 56A, 56B.
Les suiveurs de came 58A, 58B comportent avantageusement chacun un élément rotatif 62A, 62B tel qu’un galet propre à rouler suivant la longueur des surfaces de came 56A, 56B. L’axe de rotation des galets s’étend perpendiculairement à l’axe X-X. The cam followers 58A, 58B each advantageously comprise a rotary element 62A, 62B such as a roller suitable for rolling along the length of the cam surfaces 56A, 56B. The axis of rotation of the rollers extends perpendicular to the axis X-X.
Avantageusement, et comme illustré sur la figure 2, les galets 62A, 62B présentent une forme de diabolo, avec une surface concave complémentaire à la surface cylindrique de la came 54. Advantageously, and as illustrated in FIG. 2, the rollers 62A, 62B have a diabolo shape, with a concave surface complementary to the cylindrical surface of the cam 54.
Les ressorts 60A, 60B s’étendent transversalement par rapport aux surfaces de came. Ils sont coaxiaux d’axe Y-Y sécant à l’axe X-X. Ces ressorts, maintenus constamment comprimés et s’appuient à une extrémité sur le caisson 12 et à leur autre extrémité sur l’axe des galets rotatifs 62A, 62B formant les suiveurs de came. The springs 60A, 60B extend transversely to the cam surfaces. They are coaxial from axis Y-Y intersecting to axis X-X. These springs, kept constantly compressed and bear at one end on the box 12 and at their other end on the axis of the rotary rollers 62A, 62B forming the cam followers.
Un spider complémentaire 70, ménagé entre la came 54 et le moteur d’actionnement 32 assure le guidage axial de la tige 52 et de la came 54 pour assurer un déplacement de ceux-ci suivant l’axe X.X. Comme le spider 40, le spider 70 est perméable au gaz. An additional spider 70, formed between the cam 54 and the actuation motor 32 ensures the axial guidance of the rod 52 and of the cam 54 to ensure a displacement of the latter along the axis X.X. Like the spider 40, the spider 70 is permeable to gas.
Les surfaces de came 56A, 56B présentent en partie médiane, suivant la longueur de l’axe X-X et en section suivant le plan de parcours des galets, une plage 72 dont la distance à l’axe X-X de déplacement de la came est localement constante suivant l’axe X- X de déplacement de la came. Cette plage 72 s’étend sur quelques dixièmes de millimètres suivant l’axe X-X. Cette plage médiane 72 est positionnée sur la came de sorte que chaque galet appuie sur cette plage médiane lorsque la membrane 22 est en position de repos, c’est-à-dire dans une position médiane entre les deux positions extrêmes pouvant être occupées sous l’action du moteur 30. The cam surfaces 56A, 56B have in the middle part, along the length of the axis XX and in section along the path of travel of the rollers, a range 72 whose distance from the axis XX of movement of the cam is locally constant along the axis X- X of displacement of the cam. This range 72 extends over a few tenths of a millimeter along the X-X axis. This median range 72 is positioned on the cam so that each roller presses on this median range when the membrane 22 is in the rest position, that is to say in a median position between the two extreme positions which can be occupied under the motor action 30.
De part et d’autre de cette partie médiane, les surfaces de came 56A, 56B présentent des plages 74 inclinées par rapport à l’axe X-X. L’inclinaison de ces plages augmentent en s’écartant suivant l’axe X-X de part et d’autre de cette plage médiane de sorte que lorsque les suiveurs de came s’écartent de la zone médiane, l’angle entre l’axe X-X et la normale au point de contact du galet sur la surface de came augmente de sorte que, la force appliquée sur la membrane augmente. On either side of this middle part, the cam surfaces 56A, 56B have areas 74 inclined relative to the axis XX. The inclination of these ranges increases by deviating along the axis XX on either side of this median range so that when the cam followers deviate from the median zone, the angle between the axis XX and the normal at the point of contact of the roller on the cam surface increases so that the force applied to the diaphragm increases.
Ainsi, la distance entre l’axe X-X et un point de la surface de came diminue en s’écartant de la plage médiane 72. Les surfaces de came sont convergentes à l’écart de la zone médiane. Thus, the distance between the axis X-X and a point on the cam surface decreases while deviating from the median range 72. The cam surfaces converge away from the median zone.
Le haut-parleur illustré sur la figure 1 fonctionne de la manière suivante. The speaker illustrated in Figure 1 operates as follows.
Sous l’action du courant électrique appliqué au bobinage 36, la membrane 22 se déplace comme connu en soi. Lors du déplacement de la membrane, la came 54, entraînée par la membrane, se déplace axialement par rapport aux suiveurs de came 58A, 58B. Les suiveurs de came exercent alors une force dirigée suivant l’axe Y-Y vers l’axe X-X sur les surfaces de came 56A, 56B. Ces surfaces de came étant inclinées et maintenues suivant l’axe Y-Y entre les deux galets, la surface de came est soumise à une force axiale, laquelle est appliquée à la membrane 22 au travers de la tige 52. Under the action of the electric current applied to the winding 36, the membrane 22 moves as known per se. When the diaphragm moves, the cam 54, driven by the diaphragm, moves axially relative to the cam followers 58A, 58B. The cam followers then exert a force directed along the Y-Y axis toward the X-X axis on the cam surfaces 56A, 56B. These cam surfaces being inclined and maintained along the axis Y-Y between the two rollers, the cam surface is subjected to an axial force, which is applied to the membrane 22 through the rod 52.
Si la membrane 22 est déplacée vers l’intérieur du caisson 12, conduisant à comprimer l’air dans la chambre 14, la came 54 est déplacée à l’écart de la membrane 22. Sous l’action des ressorts 60A, 60B agissant au travers des suiveurs de came 62A, 62B, la came 54 est sollicitée dans son sens de déplacement. If the membrane 22 is moved towards the inside of the box 12, resulting in compressing the air in the chamber 14, the cam 54 is moved away from the membrane 22. Under the action of the springs 60A, 60B acting at the through cam followers 62A, 62B, the cam 54 is biased in its direction of movement.
La surpression dans l’enceinte 14 agit sur la membrane 22 pour sortir la membrane 22 hors du caisson 12. Au contraire, la came 54 produit une force de rappel de la membrane 22 à l’intérieur du caisson. Avantageusement, la forme de la came 54 est adaptée pour que la somme des deux forces produites par la came et celle résultant de la surpression dans la chambre 14 s’annule pratiquement en tout point de la came ou est égale à une valeur désirée en tout point de la came. The overpressure in the enclosure 14 acts on the membrane 22 to take the membrane 22 out of the box 12. On the contrary, the cam 54 produces a return force of the membrane 22 inside the box. Advantageously, the shape of the cam 54 is adapted so that the sum of the two forces produced by the cam and that resulting from the overpressure in the chamber 14 vanishes practically at any point of the cam or is equal to a desired value in all point of the cam.
De même, lorsque la membrane 22 est poussée en dehors du caisson 12 par le moteur 30, une dépression naît à l’intérieur de la chambre 14 visant à rappeler la membrane vers l’intérieur du caisson. Dans ce cas, la came 54 exerce sous la sollicitation des ressorts 60A, 60B une force sur la membrane 22 conduisant à repousser celle-ci en dehors du caisson 12, compensant ainsi l’effet de la dépression dans la chambre 14. Likewise, when the membrane 22 is pushed out of the box 12 by the motor 30, a vacuum arises inside the chamber 14 intended to return the membrane towards the inside of the box. In this case, the cam 54 exerts under the stress of the springs 60A, 60B a force on the membrane 22 leading to push the latter out of the box 12, thus compensating for the effect of the depression in the chamber 14.
La forme de la surface de came permet de transformer une partie d’une force FRz exercée par les ressorts 60A et 60B suivant l’axe Y-Y en une force FRx suivant l’axe X-X. The shape of the cam surface makes it possible to transform part of a force F Rz exerted by the springs 60A and 60B along the axis YY into a force F Rx along the axis XX.
A la position d’équilibre, x=0 correspondant à la position de repos de la membrane 22, la surface de la came ayant une plage 72 dont la distance à l’axe X-X de déplacement de la came est localement constante suivant l’axe X-X de déplacement de la came. La surface de came est telle que la force FRx suivant l’axe X-X appliquée par la came sur la membrane 22 par l’intermédiaire de la tige 52, est nulle. A la position d’équilibre, x=0, les galets appuient sur la plage médiane de la surface de la came 54 qui est parallèle à l’axe X-X. At the equilibrium position, x = 0 corresponding to the rest position of the membrane 22, the surface of the cam having a range 72 whose distance from the axis XX of displacement of the cam is locally constant along the axis XX displacement of the cam. The cam surface is such that the force F Rx along the axis XX applied by the cam to the membrane 22 via the rod 52, is zero. At the equilibrium position, x = 0, the rollers bear on the median range of the surface of the cam 54 which is parallel to the axis XX.
Compte tenu de la forme convexe des surfaces de la came 54, la membrane 22 subit, lors de son déplacement, une force FRx, par l’intermédiaire de la tige 52, suivant l’axe X-X dans le même sens que celui du déplacement. L’amplitude de cette force dépend de l’angle formé par la surface de la came 54 avec l’axe X-X au point de contact des galets 62A, 62B. Cette force est de la forme :Given the convex shape of the surfaces of the cam 54, the membrane 22 undergoes, during its displacement, a force F Rx , by means of the rod 52, along the axis XX in the same direction as that of the displacement . The amplitude of this force depends on the angle formed by the surface of the cam 54 with the axis XX at the point of contact of the rollers 62A, 62B. This force is of the form:
La raideur KR(x) est négative car elle produit une force dans le même sens que le déplacement de la membrane. The stiffness K R (x) is negative because it produces a force in the same direction as the displacement of the membrane.
Lors du déplacement de la membrane 22 par l’action du courant circulant dans la bobine, plusieurs raideurs sont mises en jeu : When the membrane 22 is displaced by the action of the current flowing in the coil, several stiffnesses are involved:
Km(x) > 0, la raideur de l’ensemble formé du joint de guidage 24 et des spiders de guidage 41 et 70 ; K m (x)> 0, the stiffness of the assembly formed by the guide seal 24 and the guide spiders 41 and 70;
Kair(x) ³ 0, la raideur liée à la compression/décompression de l’air interne de la chambre 14 ; K air (x) ³ 0, the stiffness linked to the compression / decompression of the internal air of the chamber 14;
KR(x ) < 0, la raideur liée à la force produite sur la membrane 22 par le mécanisme de sollicitation 50. K R (x) <0, the stiffness linked to the force produced on the membrane 22 by the biasing mechanism 50.
La stabilité statique et dynamique de l’ensemble des pièces en mouvement est assurée par la relation suivante : The static and dynamic stability of all moving parts is ensured by the following relationship:
Avec Kmin une valeur positive à choisir. With K min a positive value to choose.
La forme de la came 52 est choisie de telle sorte que quelle que soit la position x de la membrane, la somme des raideurs Km(x) + Kair(x ) + KR(x) soit proche de la valeur désirée Kmin. Ainsi, la fréquence de résonance du système mécanique en mouvement notée FAR est donnée par : The shape of the cam 52 is chosen so that whatever the position x of the membrane, the sum of the stiffnesses K m (x) + K air (x) + K R (x) is close to the desired value K min . Thus, the resonant frequency of the moving mechanical system, denoted F AR, is given by:
OÙ OR
M est la masse l’équipage mobile 38, le bobinage 36, la membrane 22 et pour partie les joints 24 et 41 ; et M is the mass of the moving element 38, the winding 36, the membrane 22 and in part the seals 24 and 41; and
MAR est la masse mobile de la tige 52, la came 54 est pour partie le joint 70. M AR is the moving mass of the rod 52, the cam 54 is partly the seal 70.
La forme de la came est définie telle qu’exposé ci-dessous avec les notations qui suivent : X = XC Déplacement suivant X-X de l’équipage mobile 38 The shape of the cam is defined as set out below with the following notations: X = X C Moving movement XX of the moving equipment 38
x = déplacement de la came xc x = displacement of the cam x c
Au repos : x = 0. x > 0 pour un déplacement vers la gauche. At rest: x = 0. x> 0 for a movement to the left.
FT = K r(x)x Force à compenser (caisson + suspensions de l’équipage mobile) avec KT{x) = Km(x) + Kair(x) > 0 F T = K r (x) x Force to compensate (box + suspensions of the moving part) with K T {x) = K m (x) + K air (x)> 0
La force FT s’oppose au déplacement de l’équipage mobile Force vers la droite avec déplacement positif de l’équipage mobile vers la gauche. y B Déplacement du galet transversalement à l’axe X-X The force F T is opposed to the movement of the Force moving part to the right with positive movement of the moving part to the left. y B Movement of the roller transverse to the axis XX
y B < 0 pour un déplacement transversalement à l’axe X-X vers l’axe X-X. yB = 0 pour x = 0 Force exercée par le galet sur la came y B <0 for a movement transverse to the XX axis towards the XX axis. y B = 0 for x = 0 Force exerted by the roller on the cam
Force exercée vers le bas, sens des y <0 Force exerted downwards, direction of y <0
YB o : pré-compression du ressort du galet Y B o: pre-compression of the roller spring
Angle de transformation de la force du galet Angle of transformation of the roller force
Pour un angle a > 0, la force FRx s’oppose à la force FT Angle au point de contact galet-came entre la transversale à l’axe X-X au point de contact et la normale à la surface au point de contact. Même angle que celui donné par la pente de la came au point de tangence. Equation de la came = Point de contact galet-came For an angle a> 0, the force F Rx opposes the force F T Angle at the point of contact between the roller and the cam between the transverse to the axis XX at the point of contact and the normal to the surface at the point of contact. Same angle as that given by the slope of the cam at the point of tangency. Cam equation = Roller-cam contact point
Position suivant X-X d’application de la force du galet avec rB rayon du galet Position according to XX of application of the roller force with r B radius of the roller
Position transversale à l’axe X-X du point de contact du galet sur la came Position transverse to the X-X axis of the roller contact point on the cam
Le profil 4 de la came est donné par la fonction exprimant yBC en fonction de xBC. Profile 4 of the cam is given by the function expressing y BC as a function of x BC .
A l’équilibre :Equilibrium :
avec Fmin(x ) = Kminx est la force résiduelle restante après compensation, Kmin > 0. with F min (x) = K min x is the residual force remaining after compensation, K min > 0.
Ce qu’on cherche à déterminer : What we are trying to determine:
Avec : il vient : With: it comes:
A partir des relations géométriques suivantes : From the following geometric relationships:
La résolution de l’équation différentielle non-linéaire finale permet d’obtenir yBC en fonction de xBC : The resolution of the final non-linear differential equation makes it possible to obtain y BC as a function of x BC :
La valeur choisie pour Kmin < Km(x) + Kair(x ) permet de choisir la valeur de la fréquence de résonance mécanique FAR du haut-parleur placé dans un caisson clos. Typiquement la valeur de FAR sera comprise entre 30 Hz et 50 Hz. La masse supplémentaire MAR apportée par le mécanisme anti-ressort est réduite au maximum afin de minimiser la force, et donc le courant, nécessaire au déplacement de la membrane au- delà de la fréquence de résonnance. The value chosen for K min <K m (x) + K air (x) makes it possible to choose the value of the mechanical resonance frequency F AR of the loudspeaker placed in a closed box. Typically the value of F AR will be between 30 Hz and 50 Hz. The additional mass M AR provided by the anti-spring mechanism is reduced to the maximum in order to minimize the force, and therefore the current, necessary for the displacement of the membrane beyond the resonant frequency.
On comprend que l’usage d’une came et d’un suiveur de came permet de dimensionner la came de manière à produire sur la membrane 22 une force sensiblement opposée à la force résultant de l’augmentation ou de la diminution de pression dans la chambre 14. La réalisation de l’enceinte s’en trouve ainsi facilitée. It is understood that the use of a cam and a cam follower makes it possible to size the cam so as to produce on the membrane 22 a force substantially opposite to the force resulting from the increase or decrease in pressure in the room 14. The realization of the enclosure is thereby facilitated.
Sur la figure 3 est illustré un autre mode de réalisation d’une enceinte acoustique close selon l’invention. FIG. 3 illustrates another embodiment of a closed acoustic enclosure according to the invention.
Dans ce mode de réalisation, les éléments identiques ou correspondants à ceux du premier mode de réalisation sont désignés par les mêmes numéros de références. Seules les différences seront décrites dans la suite. In this embodiment, the elements identical or corresponding to those of the first embodiment are designated by the same reference numbers. Only the differences will be described below.
Dans ce mode de réalisation, la came 54 n’est pas reliée à l’équipage mobile par une tige 52. Au contraire, la came 54, est reliée à une paroi mobile 102, séparant dans le caisson 12, la chambre close 14 en une chambre avant 104 partiellement délimitée par la membrane 22 et la paroi mobile 102 et une chambre arrière 106 délimitée par les parois du caisson 12 et par la paroi mobile 102. In this embodiment, the cam 54 is not connected to the movable assembly by a rod 52. On the contrary, the cam 54, is connected to a movable wall 102, separating in the box 12, the closed chamber 14 in a front chamber 104 partially delimited by the membrane 22 and the movable wall 102 and a rear chamber 106 delimited by the walls of the box 12 and by the movable wall 102.
La paroi mobile 102 est une paroi rigide et imperméable reliée aux parois du caisson 12 par un joint souple 108 imperméable au gaz. Dans ce mode de réalisation, mais non nécessairement, la paroi 102 s’étend perpendiculairement à l’axe X-X de déplacement de la came 54. The movable wall 102 is a rigid and impermeable wall connected to the walls of the box 12 by a flexible gas-tight joint 108. In this embodiment, but not necessarily, the wall 102 extends perpendicular to the axis XX of movement of the cam 54.
Lorsque l’enceinte comporte plusieurs haut-parleurs, une même chambre arrière 106 est prévue pour deux ou plus de deux haut-parleurs dont les membranes délimitent une même chambre avant 104 séparée de la chambre arrière dans une unique paroi 102. When the enclosure comprises several speakers, the same rear chamber 106 is provided for two or more of two speakers whose membranes define the same front chamber 104 separated from the rear chamber in a single wall 102.
Le guidage suivant l’axe X-X de l’équipage mobile formé de la paroi 102 et de la came 54 est assuré par le joint 108 et les galets 62A, 62B enserrant la came sous l’action des ressorts 60A, 60B. Guiding along the axis X-X of the mobile assembly formed by the wall 102 and the cam 54 is provided by the seal 108 and the rollers 62A, 62B enclosing the cam under the action of the springs 60A, 60B.
Dans ce mode de réalisation, un évent de décompression calibré 1 14, 1 16 relie la chambre avant 104 et la chambre arrière 106 au milieu extérieur. Ces évents sont suffisamment petits pour éviter la circulation d’air lors du mouvement de la membrane 22 mais sont propres à assurer un équilibrage des pressions entre l’extérieur et l’intérieur du caisson lors des variations de pression atmosphérique. In this embodiment, a calibrated decompression vent 1 14, 1 16 connects the front chamber 104 and the rear chamber 106 to the outside environment. These vents are small enough to avoid the circulation of air during the movement of the membrane 22, but are capable of ensuring pressure balancing between the exterior and the interior of the box during variations in atmospheric pressure.
Lors du mouvement de la membrane 22 sous l’action du moteur 30, la paroi 102 se déplace du fait de la dépression ou de la compression dans la chambre avant 104. Sous l’action du déplacement de la paroi 102, la came 54 est déplacée et produit, sous l’action des suiveurs de came 58A, 58B une force appliquée sur la paroi 102. Cette force est contraire à l’effet de la pression agissant sur cette même paroi 102 et donc orientée suivant le sens de déplacement de la paroi 102. Cette force est transmise à la membrane 22 par l’intermédiaire du gaz emprisonné dans la chambre avant 104. During the movement of the membrane 22 under the action of the motor 30, the wall 102 moves due to the vacuum or compression in the front chamber 104. Under the action of the movement of the wall 102, the cam 54 is moved and produced, under the action of the cam followers 58A, 58B, a force applied to the wall 102. This force is contrary to the effect of the pressure acting on the same wall 102 and therefore oriented in the direction of movement of the wall 102. This force is transmitted to the membrane 22 via the gas trapped in the front chamber 104.
On comprend que dans ce mode de réalisation également, la raideur de la compression du gaz dans la chambre avant 104 est compensée par la force appliquée par la came 56 du mécanisme de sollicitation axiale 50. It is understood that in this embodiment also, the stiffness of the compression of the gas in the front chamber 104 is compensated by the force applied by the cam 56 of the axial biasing mechanism 50.
Sur la figure 4 est représentée une variante de réalisation du mécanisme anti ressort 50, pouvant être implémenté dans les modes de réalisation des figures 1 et 3 en remplacement du mécanisme décrit, tous les autres éléments non décrits sur la figure 4 restant identiques. In Figure 4 is shown an alternative embodiment of the anti-spring mechanism 50, which can be implemented in the embodiments of Figures 1 and 3 to replace the mechanism described, all the other elements not described in Figure 4 remaining identical.
Sur la figure 4, on reconnaît la came 54 disposée suivant l’axe X-X, reliés soit directement à l’équipage mobile portant la membrane 22, comme sur la figure 1 , soit à la paroi mobile 102, comme sur la figure 3. In FIG. 4, we recognize the cam 54 arranged along the axis X-X, connected either directly to the mobile assembly carrying the membrane 22, as in FIG. 1, or to the mobile wall 102, as in FIG. 3.
Le profil de la came 54 est identique au profil décrit au regard des figures précédentes. The profile of the cam 54 is identical to the profile described with regard to the preceding figures.
Dans ce mode de réalisation, la came 54 est enserrée entre des galets 202A, 202B, 202C, régulièrement angulairement répartis autour de l’axe X-X. Ces galets sont portés à l’extrémité libre de bras élastiques 204A, 204B, 204C. Ces bras élastiques sont fixés chacun à leur autre extrémité sur une structure rigide 206, elle-même solidaire du caisson 14. In this embodiment, the cam 54 is enclosed between rollers 202A, 202B, 202C, regularly angularly distributed around the axis XX. These rollers are carried at the free end of elastic arms 204A, 204B, 204C. These elastic arms are each fixed at their other end on a rigid structure 206, itself integral with the box 14.
Les bras 204A, 204B, 204C s’étendent perpendiculairement à l’axe X-X dans un même plan. Ils sont déportés transversalement par rapport à l’axe X-X. The arms 204A, 204B, 204C extend perpendicular to the axis X-X in the same plane. They are offset transversely to the X-X axis.
Les galets 202A, 202B, 202C sont montés rotatifs dans le prolongement de l’axe des bras 204A, 204B, 204C respectivement, et suivant l’axe des bras. Ils sont propres à rouler suivant la surface de la came 54 suivant l’axe X-X. The rollers 202A, 202B, 202C are mounted to rotate in the extension of the axis of the arms 204A, 204B, 204C respectively, and along the axis of the arms. They are suitable for rolling along the surface of the cam 54 along the axis X-X.
Les bras 204A, 204B, 204C sont précontraints de manière à assurer un contact permanent entre les galets 202A, 202B, 202C et la came 54, quelle que soit la position des galets suivant la longueur de la came 54 considérée suivant l’axe X-X. The arms 204A, 204B, 204C are prestressed so as to ensure permanent contact between the rollers 202A, 202B, 202C and the cam 54, regardless of the position of the rollers along the length of the cam 54 considered along the axis X-X.
Dans ce mode de réalisation, la présence de trois éléments rotatifs angulairement répartis autour de l’axe X-X assure un guidage satisfaisant de la came 54 suivant l’axe X- X. La présence de bras élastiques précontraints déformables en flexion assure un effort relativement constant des galets 202A, 202B, 202C sur la came, quelle que soit leur position et évite le blocage des galets. In this embodiment, the presence of three rotary elements angularly distributed around the axis XX ensures satisfactory guiding of the cam 54 along the axis X- X. The presence of elastic pre-stressed arms deformable in bending ensures a relatively constant force rollers 202A, 202B, 202C on the cam, whatever their position and avoids blocking of the rollers.

Claims

REVENDICATIONS
1. Enceinte acoustique close (10) comportant un caisson (12) et un haut-parleur (20) comportant une membrane mobile (22) par rapport au caisson (12), le caisson (12) et la membrane (22) délimitant une chambre (14) essentiellement close ; le haut-parleur (20) comportant un moteur (30) à commande électrique d’actionnement de la membrane mobile (22) par rapport au caisson (12), l’enceinte comportant en outre un mécanisme (50) de sollicitation axiale de la membrane (22) à l’écart de sa position médiane de repos à l’encontre de la force de pression exercée par le gaz contenu dans le caisson (12) sur la membrane (22), caractérisée en ce que le mécanisme (50) comporte une came (54) mobile par rapport au caisson (12) suivant un axe (X-X) de déplacement de la came sous l’action de déplacement de la membrane (22) et au moins un suiveur de came (58A, 58B ; 200A, 200B, 200C) sollicité transversalement à la came (54) par au moins un ressort (60A, 60B) et en appui sur la came (54), la came (54) présentant au moins une surface de came (56A, 56B) propre à convertir l’effort transversal du ou chaque ressort (60A, 60B) en un effort axial sur la came (54) dont l’intensité varie en fonction de la position de la came (54) par rapport au caisson (12). 1. Closed acoustic enclosure (10) comprising a box (12) and a loudspeaker (20) comprising a membrane movable (22) relative to the box (12), the box (12) and the membrane (22) defining a essentially closed chamber (14); the loudspeaker (20) comprising a motor (30) with electrical control for actuating the movable diaphragm (22) relative to the box (12), the enclosure further comprising a mechanism (50) for axial biasing of the membrane (22) away from its median position of rest against the pressure force exerted by the gas contained in the box (12) on the membrane (22), characterized in that the mechanism (50) comprises a cam (54) movable relative to the box (12) along an axis (XX) of movement of the cam under the action of displacement of the membrane (22) and at least one cam follower (58A, 58B; 200A , 200B, 200C) biased transversely to the cam (54) by at least one spring (60A, 60B) and bearing on the cam (54), the cam (54) having at least one cam surface (56A, 56B) suitable for converting the transverse force of the or each spring (60A, 60B) into an axial force on the cam (54) whose intensity varies as a function of the position of the cam (54) relative to the ca isson (12).
2. Enceinte acoustique selon la revendication 1 , caractérisée en ce que la came (54) est liée à la membrane (22) du haut-parleur par une tige (52) s’étendant suivant l’axe (X-2. Acoustic enclosure according to claim 1, characterized in that the cam (54) is linked to the diaphragm (22) of the loudspeaker by a rod (52) extending along the axis (X-
X) de déplacement de la membrane (22). X) displacement of the membrane (22).
3. Enceinte selon la revendication 2, caractérisée en ce qu’elle comporte un joint élastique (70) de guidage reliant la tige (52) au caisson (12). 3. Enclosure according to claim 2, characterized in that it comprises an elastic seal (70) for guiding connecting the rod (52) to the box (12).
4. Enceinte selon la revendication 1 , caractérisée en ce que la came (54) est reliée à une paroi (102) mobile par rapport au caisson (12), la paroi mobile (102) délimitant avec le caisson (12) une chambre arrière essentiellement close (106) et une chambre avant essentiellement close (104) délimitée partiellement par la membrane (22) du haut-parleur. 4. Enclosure according to claim 1, characterized in that the cam (54) is connected to a wall (102) movable relative to the box (12), the movable wall (102) delimiting with the box (12) a rear chamber essentially closed (106) and an essentially closed front chamber (104) partially delimited by the diaphragm (22) of the loudspeaker.
5. Enceinte selon l’une quelconque des revendications précédentes, caractérisée en ce que la came (54) comporte au moins deux surfaces de came (56A, 56B) réparties angulairement autour de l’axe (X-X) de déplacement de la came et en ce que le mécanisme (50) de sollicitation axiale de la membrane (12) comporte pour chaque surface de came un suiveurs de came (58A, 58B ; 200A, 200B, 200C) sollicités vers l’axe (X-X) de déplacement de la came et la came (54) étant enserrée entre les suiveurs de came (58A, 58B ; 200A, 200B, 200C). 5. Enclosure according to any one of the preceding claims, characterized in that the cam (54) comprises at least two cam surfaces (56A, 56B) angularly distributed around the axis (XX) of movement of the cam and in that the axial biasing mechanism (50) of the diaphragm (12) comprises for each cam surface a cam follower (58A, 58B; 200A, 200B, 200C) biased towards the axis (XX) for displacement of the cam and the cam (54) being clamped between the cam followers (58A, 58B; 200A, 200B, 200C).
6. Enceinte selon l’une quelconque des revendications précédentes, caractérisée en ce que le ou chaque suiveur de came (58A, 58B ; 200A, 200B, 200C) comporte un élément rotatif (62A, 62B) propre à rouler sur la came (54). 6. Enclosure according to any one of the preceding claims, characterized in that the or each cam follower (58A, 58B; 200A, 200B, 200C) comprises a rotary element (62A, 62B) capable of rolling on the cam (54 ).
7. Enceinte selon l’une quelconque des revendications précédentes, caractérisée en ce que le ou chaque suiveur de came (200A, 200B, 200C) est porté par un bras élastique précontraint (204A, 204B, 204C) s’étendent dans un plan transversal à l’axe (X-X). 7. Enclosure according to any one of the preceding claims, characterized in that the or each cam follower (200A, 200B, 200C) is carried by a pre-stressed elastic arm (204A, 204B, 204C) extend in a transverse plane to the axis (XX).
8. Enceinte selon l’une quelconque des revendications précédentes, caractérisée en ce que la came (54) comporte une plage (72) dont la distance à l’axe (X-X) de déplacement de la came 54 est localement constante suivant l’axe (X-X) de déplacement de la came, cette plage (72) étant en contact avec le ou chaque suiveur de came (58A, 58B ; 200A, 200B, 200C) lorsque la membrane (22) est en position de repos de sorte qu’aucune force ne soit appliquée par la came (54) sur la membrane (22) par la came (54) dans cette position de repos de la membrane (22). 8. Enclosure according to any one of the preceding claims, characterized in that the cam (54) has a range (72) whose distance from the axis (XX) of displacement of the cam 54 is locally constant along the axis (XX) of movement of the cam, this area (72) being in contact with the or each cam follower (58A, 58B; 200A, 200B, 200C) when the diaphragm (22) is in the rest position so that no force is applied by the cam (54) to the membrane (22) by the cam (54) in this rest position of the membrane (22).
9. Enceinte selon l’une quelconque des revendications précédentes, caractérisée en ce que la came (54) comporte sur une plage (74) inclinée par rapport à l’axe (X-X) de déplacement de la came (52). 9. Enclosure according to any one of the preceding claims, characterized in that the cam (54) comprises on a range (74) inclined relative to the axis (X-X) of displacement of the cam (52).
10. Enceinte selon la revendication 9, caractérisée en ce que l’inclinaison de la surface de came suivant la plage inclinée (74) est progressivement croissante suivant l’axe (X-X) de déplacement de la came à l’écart de la zone de contact avec le suiveur de came lorsque la membrane (22) est en position de repos de sorte que la came (54) impose une force d’intensité croissante à la membrane (22) au fur et à mesure du déplacement de la membrane (22) à l’écart de sa position de repos. 10. Enclosure according to claim 9, characterized in that the inclination of the cam surface along the inclined range (74) is progressively increasing along the axis (XX) of movement of the cam away from the area of contact with the cam follower when the diaphragm (22) is in the rest position so that the cam (54) imposes a force of increasing intensity on the diaphragm (22) as the diaphragm (22) moves ) away from its rest position.
EP19809862.6A 2018-12-03 2019-12-03 Infinite baffle with low stiffness Active EP3892011B1 (en)

Applications Claiming Priority (2)

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FR1872229A FR3089381B1 (en) 2018-12-03 2018-12-03 Closed enclosure with low stiffness
PCT/EP2019/083498 WO2020115044A1 (en) 2018-12-03 2019-12-03 Infinite baffle with low stiffness

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CN (1) CN113196799B (en)
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WO2024134496A1 (en) * 2022-12-20 2024-06-27 Powersoft S.P.A. Loudspeaker and method for spreading a sound.

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US20220030351A1 (en) 2022-01-27
WO2020115044A1 (en) 2020-06-11
EP3892011B1 (en) 2022-12-14
CN113196799B (en) 2024-09-20
US11770648B2 (en) 2023-09-26
CN113196799A (en) 2021-07-30
FR3089381B1 (en) 2020-10-30

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