FR2783870A1 - Loudspeaker for compensating vehicle exhaust noise has electromagnets for field magnets to ensure high temperature operation - Google Patents

Abstract

The system uses electromagnets for field magnets in place of permanent magnets. The anti-noise system for a vehicle exhaust comprises a computer (3) coupled to a loudspeaker mounted within the exhaust in order to provide sound signals to compensate for noise emitted from the exhaust pipe. The loudspeaker includes a number of windings (9) mounted around the periphery of the base of the speaker cone, in order to provide the field magnet induction required. These coils are connected to a constant current source (7), deriving power from the vehicle electrical supply, in order to maintain constant magnetic induction within the air gap of the loudspeaker system, regardless of the operating temperature.

Description

The present invention relates to an anti-line noise system

  exhaust for motor vehicle.

  There are already known in the prior art, anti-noise systems for exhaust lines which include means for recording residual line noise connected to an anti-noise computer adapted to deliver an anti-noise signal. loudspeaker means control noise generating an anti-noise

line.

  These systems have been developed to reduce the level of nuisance

  these sounds related to the operation of vehicle engines.

  The noise canceling computer then operates in a conventional manner for

  generate an anti-noise signal from residual line noise.

  This anti-noise signal controls general loudspeaker means.

  ration of line noise canceling, these loudspeaker means being for example

  somehow associated with the exhaust line.

  However, the development of these systems comes up against a certain number of problems linked in particular to the extremely severe conditions of

  operation of the loudspeaker means.

  Indeed, these means must be able to function in a

  temperature range from -40 C to +200 C.

  However, loudspeaker means whose inductive field is generated by permanent magnets, are unable to provide the acoustic power

  necessary for this type of application in such a range of temperatures.

  The object of the invention is therefore to solve these problems.

  To this end, the invention relates to an anti-noise system for line

  motor vehicle exhaust, of the type comprising means for

  residual line noise survey, connected to an anti-noise calculator suitable for

  supplying an anti-noise control signal from general loudspeaker means

  ration of an anti-line noise, characterized in that the loudspeaker means comprise inductor field generation coils connected to constant current supply means, to maintain the constant induction in the air gap of these means loudspeaker, regardless of the temperature

operation of these.

  The invention will be better understood with the aid of the description which follows.

  vre, given only by way of example and made with reference to the drawings an-

attached, on which:

  - Fig.1 shows a block diagram illustrating the general structure

  part of an anti-noise system according to the invention; - Fig.2 shows a side view in section illustrating the general structure of speaker means forming part of such a system; - Fig.3 shows an end view of such loudspeaker means; - Fig.4 shows a block diagram illustrating the structure of first supply means forming part of a system according to the invention; and - Fig.5 shows a block diagram illustrating the structure of second supply means forming part of a system according to the invention. We recognize in fact in Figure 1, an anti-noise system for a motor vehicle exhaust line, this exhaust line is designated

by the general reference 1.

  This system conventionally comprises means for recording residual line noise, designated by the general reference 2 in this figure,

  including, for example, any suitable microphone.

  These means are connected to an anti-noise computer designated by the general reference 3, adapted to deliver an anti-noise control signal from loudspeaker means designated by the general reference 4, for generating a

  anti-line noise, these loudspeaker means being associated with the exhaust line

pement.

  As noted earlier, such means at high

  loudspeaker must be capable of operating in a severe thermal environment, and in particular in a temperature range which may extend between

-40 C and +200 C.

  According to the invention, and as shown in FIGS. 2 and 3,

  in the system according to the invention, the loudspeaker means designated by the

  general reference 4 include inductive field generation windings

  tor connected to constant current supply means, to maintain the constant induction in the air gap of these loudspeaker means, whatever

  or the operating temperature of these.

  In these Figures 2 and 3, there is in fact shown means to high

  loudspeaker, the inductor field generation means of which are designated by the general reference 5 in this figure, comprise different windings, one of which is for example designated by the general reference 6, which are connected to

  constant current supply means, designated by the general reference

line 7 in Figure 2.

  In fact, these inductive field generation windings means

  with loudspeaker can be distributed for example on a circle around an evi-

  dement central thereof, this central recess being designated by the general reference 8, and allowing for example the passage of a portion of exhaust line. In the example described, twelve windings have been illustrated, these twelve windings being distributed in at least two groups connected in parallel of six

  windings each, mounted in series.

  It goes without saying of course that a different number of windings and a

  different connection of these can be used.

  Indeed, we can consider any kind of series / parallel connection of these windings, allowing the optimization of the ampere x turns produced in the

  aim of optimizing the use of material, in particular windings by determining

  tion of the optimal current cause them to flow in them.

  This then makes it possible to reduce the losses by Joule effect generated and

  therefore the heating of the loudspeaker means.

  Each coil is then mounted on a magnetic core, such as for example the magnetic core 9 for the coil 6 between two plates of

field, respectively 10 and 11.

  The constant current supply of the windings can be ensured by

  example by a constant current source of linear type, such as that re-

shown in Figure 4.

  This source presents a classic structure based on the use

  a comparator designated by the general reference 12 whose non-input

  inverter is connected to the midpoint of a bridge comprising a resistor 13 and a Zener diode 14 in series and the output of which is connected to the base of a transistor connected between a resistor 16 and the windings designated by the reference

general 17 in this figure.

  The inverting input of comparator 12 is connected to the output of the

resistance 16.

  The operation of such a constant current power source is well known in the state of the art, so that it will not be described.

in more detail later.

  However, it is also possible to use as a source of ali-

  constant current mentation, a switching source such as that shown

shown in Figure 5.

  In this one, one uses a transistor indicated by the general reference

  18 controlled by a comparator 19. A freewheeling diode designated by the reference

  General reference 20 is connected in parallel across the terminals of a capacitor

  signed by the general reference 21 and a bridge comprising in series, on the one hand,

  the windings designated by the general reference 22 and on the other hand, a resistor

tance 23.

  The midpoint of this bridge is applied to comparator 19.

  In such a structure, the inductance of the windings is then used

  as an inductive storage component.

  The operation of such a power source is also

  classic, we will not describe it in more detail later.

  It is understood in light of this that by using such a structure, it is possible to operate the loudspeaker means with an induction

  constant in the air gap whatever their operating temperature.

  Furthermore, the structure of these loudspeaker means is also

  optimized in terms of volume, and therefore weight.

  It goes without saying of course that still other embodiments

  of such a system can be envisaged.

Claims (5)

  1. Anti-noise system for motor vehicle exhaust line   bile, of the type comprising means (2) for detecting residual line noise,   connected to an anti-noise computer (3) adapted to deliver an anti-noise signal   control noise of loudspeaker means (4) for generating noise canceling   line, characterized in that the loudspeaker means comprise coils   inducing field generation ges (5) connected to supply means (7)   constant current mentation, to maintain constant induction in the air gap of these loudspeaker means, whatever the operating temperature of these.   2. System according to claim 1, characterized in that the coils   nages (5) of generation of the inductive field of the loudspeaker means (4) are   distributed around a central recess (8) thereof.   3. System according to claim 2, characterized in that the coils   swims (5) are distributed on a circle around the recess (8) of the loudspeaker means.   4. System according to any one of the preceding claims,   characterized in that the coils (5) are connected in a configuration series and / or parallel.   5. System according to claim 4, characterized in that the coils   swims (5) are divided into at least two groups connected in parallel, more   each winding, connected in series.