FR2780095A1 - I.c. engine exhaust muffler internal passage shutter - Google Patents

Abstract

The muffler has an inner passage closed by a movable shutter (40) with an actuator (44). The actuator contains a spring (76) for returning the shutter to its rest position, and a piston (64) which is connected mechanically to the shutter by a rigid rod (42) in guide bearings (52, 54) and slides in a housing (45) divided into two chambers (72, 74) of variable volume, depending on the position of the piston. A clearance (71) allows a fluid to flow from one chamber to the other as the piston moves.

Description

The present invention relates to a device for closing a step

  internal sage of an exhaust pipe, of the type comprising a shutter

  ration, movable between an at least partial closing position of said step-

  wise, and a position released from said passage, and a member for urging said flap to a rest position.

  The invention further relates to an exhaust pipe, of the type

  bearing an envelope delimiting an enclosure provided with an entrance and a

  outlet for exhaust gases and at least one sealing device.

  It is known, in particular from document FR-A-96 01233, to install, on a motor vehicle fitted with a heat engine, an exhaust pipe whose configuration of the exhaust line varies in

  function of the exhaust gas flow and / or pressure.

  To this end, it is known to provide in the same exhaust several chambers communicating by passages formed in transverse walls of the exhaust. Some passages are equipped

  shutter devices comprising a shutter allowing the selected shutter

  tive of the passage depending on the operating conditions of the vehicle.

  In particular, it is known to connect the shutter shutter to a pressure member, constituted for example by a bellows, one of the faces of which is stressed by pressure in one of the chambers of the exhaust pipe and the other side is subjected to a separate pressure, for example the

atmospheric pressure.

  The cost of a pressure actuator is relatively high,

  that it requires the use of a deformable membrane. In addition, its integration

  tion in a muffler is tricky. Finally, the reliability of an action-

  Manometric neur placed in an aggressive environment is difficult to insure.

  The object of the invention is to provide a solution to the problem of obturating

  tion of an internal passage of an exhaust pipe, not having the

  disadvantages mentioned above and which, in particular, is simple to put

  be implemented, reliable and inexpensive.

  To this end, the invention relates to a device for closing a step

  internal sage of an exhaust pipe, of the aforementioned type, characterized in that said biasing member comprises a return spring of the shutter towards its rest position, and a piston mechanically coupled to the shutter and mounted to slide in a body delimiting two chambers of variable volume depending on the position of the piston, a nozzle ensuring the transfer, from one chamber to the other, of a fluid filling the two chambers, during the movement of the piston. According to particular embodiments, the closure device comprises one or more of the following characteristics: - the body defines a substantially enclosed space in which the two

  rooms are defined, which space is substantially isolated from the am-

  biant in which the flap is movable; - an interval is maintained between at least part of the periphery

  piston and body, creating a leakage area between the two chambers

  bres, which zone forms said nozzle;

  - the internal section of the body is variable depending on the direction of sliding

  piston; - one of the ends of the spring is mechanically associated with the piston, and the other end of the spring is mechanically associated with the body; - it includes a rigid rod mechanically associating the flap with

  sliding piston, and guide bearings in translation of said rod following

  before the sliding direction of the piston; - Two rod guide bearings are carried by the body along the axis thereof, on either side of the piston; - At least one of the guide bearings is adapted to be carried by the structure of the exhaust pipe; - The piston has a wall integral with the rod, which wall is bordered at its periphery by a ring; - Said ring is received in a peripheral groove delimited in the thickness of the wall; and

  a clearance forming said nozzle is provided between the ring and the groove

ripherique.

  The invention further relates to an exhaust pipe of the pre-

  cited, characterized in that said device is associated with an internal passage

  of the exhaust pipe for closing it, the body of the biasing member

  tion being integral with said envelope.

  The invention will be better understood on reading the description which will

  follow, given only as an example and made with reference to the

  sins, in which: - Figure 1 is a longitudinal sectional view of a silencer according to the invention incorporating a closure device; - Figure 2 is a longitudinal sectional view on a larger scale of the closure device used in the silencer of Figure 1;

  - Figure 3 is a longitudinal sectional view of an exhaust pot-

  ment incorporating an alternative embodiment of a sealing device

lon the invention;

  - Figure 4 is a partial sectional view of an alternative embodiment

  tion of the piston of a closure device according to the invention; and - Figure 5 is a longitudinal sectional view of a variant of

  embodiment of the closure device of FIG. 2.

  The exhaust silencer 10 shown in Figure 1 is intended

  to be used in an exhaust line of a motor vehicle

bile with thermal engine.

  The silencer 10 comprises an envelope 12 of substantially cylindrical shape. The space delimited by the envelope 12 is divided into four adjoining chambers 14, 16, 18, 20, separated by means of three

  transverse partitions, commonly called cups, designated res-

  pectively by the references 22, 24 and 26. The cups 22 and 24 are provided, over their entire surface, with a multitude of perforations, the

  density is adapted to the desired acoustic effect.

  The partition 26 also has perforations on its surface.

  However, the density of perforations is low and much lower than that of

partitions 22 and 24.

  An exhaust gas inlet pipe 28 crosses successively-

  chambers 14, 16 and 18 and opens into chamber 20. A range of perforations 30 of low density is provided on the lateral face of

line 28 in chamber 18.

  An outlet pipe 32 has its end for sampling the gases in the chamber 14 and passes successively through the chambers 16, 18 and 20 in order to exit through the rear face of the silencer. A range of perforations 34 of low density is provided on the lateral face of the pipe 32 in the chamber 16. The transverse wall 26, separating the chambers 18 and 20, has a circular passage 36 associated with a closure device 38 shown in

  larger scale in Figure 2.

  This comprises a shutter 40 mounted movable through the

  towards passage 36. The shutter 40 is movable between a position for closing the passage, as shown in FIG. 1, and a position released from the passage, thus ensuring the opening thereof. The shutter position

  corresponds to the rest position of the flap.

  The flap 40 is carried at the end of a sliding rod 42 associated with a biasing member 44. The latter is fixed to the transverse wall 24. It comprises a hollow body 45 delimited by a cylindrical wall 46 closed at each end by two end walls 48, 50. The sliding rod 42

  is slidably mounted along the axis of the body 45.

  The end walls 48, 50 each carrying a guide bearing in

  translation of the rod 42. These bearings, designated respectively by the references

  references 52 and 54, are for example each formed by a wire mesh sleeve possibly combined with graphite. These sleeves are each retained axially in a pierced cup denoted 56, 58. These cups each have an external peripheral rim 60, 62. These

  flanges are secured to the end walls 48, 50, by a service area

  weaving embedding the rim in a recess of the corresponding end wall

  laying. The rod 42 is integral with a piston 64 received inside the enclosure

  delimited by the cylindrical body 45. The piston comprises a support disc

  port 66 carrying a ring 68 flush with the internal surface of the cylinder wall

body dric 45.

  The disc 66 has at its periphery a peripheral groove or yoke.

  than 70 in which the ring 68 is received. The support disc 64 is de-

  limited by two identical flanges joined together, each comprising a fixing collar on the rod 32 and at their periphery an annular rim defining the

peripheral groove 70.

  The outer diameter of the ring 68 is slightly less than the diameter

  internal meter of the cylindrical wall 46 of the body. In the peripheral interval thus created, a leak is established, allowing the passage of air between the two chambers denoted 72, 74 delimited in the body 45 by the piston 64. This

  reduced section interval constitutes a nozzle 71 establishing a

  fluid connection of reduced section between the two chambers 72, 74.

  A helical spring 76 is further arranged in the chamber 74 op-

  placed on the flap 40. This generally frustoconical spring is secured on the one hand to the end wall 48 and on the other hand to the piston 64. The spring 76

  is suitable for working in compression and urges the flap 40 towards its posi-

tion of rest.

  As shown in FIG. 2, the piston 64 bears against the bearing 54 which forms a shock absorber, by means of its fixing collar on the rod 42. In this position, the flap 40 closes the passage 36, as

shown in figure 2.

  When an overpressure appears in the chamber 20 of the exhaust silencer, for example when the engine is running at a high speed, the pressure of the gas exerted on the flap 40 causes the latter to move against the spring 76 The air contained in chamber 74 is then compressed. This flows gradually towards the chamber 72 by

  the nozzle 71 formed around the ring 68.

  The slow circulation of the fluid from one chamber to the other avoids the oscillation of the flap 40, thus avoiding noise pollution. The two chambers 72, 74 in communication create via the piston 64

  a hydraulic shock absorber associated with mechanical spring 76.

  When the pressure in the chamber 20 drops, the flap 40 returns to its closed position under the action of the compressed spring 76. The excess air contained in the chamber 72 is then returned by the nozzle 71 into the

room 74.

  In Figure 3 is shown an alternative embodiment of a silencer exhaust and a sealing device. In this variation,

  the partition 24 is deleted. The bearing 52 for guiding the rod 42 is also

  slightly deleted. It is replaced by a bearing independent of the body 45 pre-

  seen at the end of the rod 42 carrying the flap 40. This bearing, noted 78, is worn

  by an openwork cup 80 fixed to the partition 26 around the passage 36.

  In this embodiment, as in the previous one, during an increase in the pressure in the chamber 20, the flap 40 is moved smoothly thanks to the presence of the biasing member 44. The latter also ensures the return of the flap 40 to its rest position when the

pressure drops.

  According to an alternative embodiment partially shown in FIG. 4, the nozzle connecting the two chambers is formed by a clearance noted 84 established between the ring 68 and the flanges forming the disc 66. In particular,

  the peripheral groove 70 in which the ring 68 is received has dimensions

  internal sions greater than the corresponding external dimensions of

  the ring, which allows the slow flow of fluid between the two chambers.

  In this case, the external cylindrical surface of the seal applies exactly and substantially without play along the internal surface of the cylindrical wall

46.

  In a variant not shown, the ring 68 comprises, on one of its

  lateral faces in the shape of a crown, several projections extending radially-

  is lying. These projections are supported on the inner surface of one of the flas-

  ques, thus reserving a clearance between the ring 68 and the flanges. The thickness of the

  clearance corresponds to the height of the radial projections.

  According to yet another variant, the projections are formed on one of the

  flanges and the sides of the ring are smooth.

  Such an arrangement guarantees an axial positioning of the ring 68, this being kept in contact with the two flanges 64. This contact is thus established on one side along a lateral face of the ring 68 and on the other

  side following the tops of the radial projections.

  In FIG. 5, yet another alternative embodiment is shown.

  tion of the shutter device. This variant is essentially similar

  in the embodiment of FIG. 2, only the wall 46 of the body being different

annuity.

  In this embodiment, the wall 46 has two cy-

  successive lindres 46A, 46B having different diameters. They are connected to each other by a connecting section 46C of progressively increasing diameter.

  The section 46A, in which the piston 64 extends at rest, has a diameter

meter less than section 46B.

  Thus, for low engine operating speeds, the leakage formed between the two chambers 72, 74 at the level of the piston 64 is low. On the contrary, for high engine speeds, i.e. when the thrust

  exerted on the flap 40 is low, the leakage around the piston 64 is greater

  aunt, the latter then being in the section 46B of enlarged diameter.

  Under these conditions, during low operating speeds of the

  engine, the biasing member 44 creates high damping.

  For high engine speeds, the biasing member 44 bene-

  has a short response time. In addition, the presence of an enlarged area

  in section 46B reduces the possibilities of blocking, due to fouling

possible ment of chambers 72, 74.

  In addition, whatever the embodiment, the sleeves cons-

  titling the guide bearings 52, 54 are released from the end walls 48, in the immediate vicinity of the rod 42. Thus, in the extreme positions of the piston 64, the latter comes into contact with these sleeves which form

  damping elements avoiding noise pollution and shaking.

Claims (12)

  1.- Shut-off device (38) of an internal passage (36) of an exhaust pipe (10), of the type comprising a shutter flap (40), movable between at least one shutter position partial of said passage (36), and a position released from said passage (36), and a member (44) for urging said flap (40) towards a rest position, characterized in that said member   bias (44) comprises a spring (76) for returning the flap (40) to its po-   rest position, and a piston (64) mechanically coupled to the flap (40) and slidably mounted in a body (45) delimiting two chambers (72, 74) of variable volume depending on the position of the piston (64), a nozzle (71) ensuring the transfer, from one chamber to the other, of a fluid filling the   two chambers, during the movement of the piston (64).   2.- Device according to claim 1, characterized in that the body (45) defines a substantially closed space in which the two chambers (72, 74) are defined, which space is substantially isolated from the ambient environment   wherein the flap (40) is movably mounted.   3.- Device according to claim 1 or 2, characterized in that an interval is maintained between at least part of the periphery of the piston (64) and the body (45), thus creating a leakage zone between the two chambers   (72, 74), which zone forms said nozzle (71).   4.- Device according to claim 3, characterized in that the internal section of the body (45) is variable according to the sliding direction of the piston (64).   5.- Device according to any one of the preceding claims,   characterized in that one end of the spring (76) is associated with   canonically with the piston (64), and the other end of the spring (76) is associated mechanically to the body (45).   6.- Device according to any one of the preceding claims,   characterized in that it comprises a rigid rod (42) combining mechanical-   the flap (40) to the sliding piston (64), and bearings (52, 54) of guide   dage in translation of said rod (42) in the sliding direction of the piston (64).   7.- Device according to claim 6, characterized in that two pa-   guide links (52, 54) of the rod (42) are carried by the following body (45)   the axis thereof, on either side of the piston (64).   8.- Device according to claim 6, characterized in that at least one of the guide bearings (74) is adapted to be carried by the structure of the exhaust.   9.- Device according to any one of the preceding claims,   characterized in that the piston (64) has a wall (66) integral with the   rod (42), which wall (66) is bordered at its periphery by a ring (68).   10.- Device according to claim 9, characterized in that said ring (68) is received in a peripheral groove (70) delimited in the thickness of the wall (66).   11.- Device according to claim 10, characterized in that a game   (84) forming said nozzle is provided between the ring (68) and the peripheral groove. that (70).   12.- Exhaust (10), of the type comprising an envelope (12) delimiting an enclosure provided with an inlet (28) and an outlet (32) for the exhaust gases and at least one device for shutter (38) according to one   any of the preceding claims, which device is associated with   an internal passage (36) of the exhaust pipe for closing it, the body   (45) of the biasing member being integral with said envelope (12).