DE102022107345A1 - Hydraulic damper with porous element - Google Patents

Abstract

A damper (12) comprising: - a cylinder (14), - a piston (18), - a compression chamber (26) and an expansion chamber (28) separated by the piston, - a balance chamber (30), - a liquid (34) flowing between the compression chamber, the expansion chamber and the balance chamber (30) due to the movements of the piston,- a gas (36) located in the balance chamber to exert a back pressure (P) on the liquid. The damper defines a passage (38) between the expansion chamber and the balance chamber, with a porous member (44) blocking the passage and being arranged to allow residual gas to flow from the expansion chamber into the balance chamber and liquid flow from the expansion chamber into the compensation chamber to oppose a resistance.

Description

• - einen Zylinder, der eine Achse des Dämpfers und eine innere Aufnahme definiert,
• - einen Kolben, der in der inneren Aufnahme axial verschiebbar ist, und eine Stange, die sich axial erstreckt und an dem Kolben befestigt ist, und
• - ein erstes axiales Ende und ein zweites axiales Ende axial gegenüber dem ersten Ende;

wobei der Zylinder, das erste Ende und der Kolben eine Druckkammer des Dämpfers definieren; der innere Zylinder, das zweite Ende, und der Kolben eine Ausdehnungskammer des Dämpfers definieren; wobei der Dämpfer ferner Folgendes umfasst:

• - eine Ausgleichskammer,
• - eine Flüssigkeit, die sich in der Kompressionskammer, der Ausdehnungskammer und der Ausgleichskammer befindet, wobei der Kolben konfiguriert ist, um aufgrund der axialen Bewegungen des Kolbens in Bezug auf den Zylinder eine Strömung der Flüssigkeit von der Ausdehnungskammer zu der Kompressionskammer und umgekehrt zuzulassen, und um dieser Strömung einen Widerstand entgegenzusetzen, wobei das erste Ende konfiguriert ist, um der Flüssigkeit zu ermöglichen, aufgrund der axialen Bewegungen des Kolbens von der Kompressionskammer in die Ausgleichskammer und umgekehrt zu fließen, und
• - ein Gas, das sich in der Ausgleichskammer befindet, um einen Gegendruck auf die Flüssigkeit auszuüben.

The present invention relates to a hydraulic damper comprising:

• - a cylinder defining an axis of the damper and an internal housing,
• - a piston axially slidable in the internal housing and a rod extending axially and fixed to the piston, and
• - a first axial end and a second axial end axially opposite the first end;

wherein the cylinder, the first end and the piston define a pressure chamber of the damper; the inner cylinder, the second end, and the piston define an expansion chamber of the damper; wherein the damper further comprises:

• - a compensation chamber,
• - a liquid located in the compression chamber, the expansion chamber and the balancing chamber, wherein the piston is configured to allow a flow of the liquid from the expansion chamber to the compression chamber and vice versa due to the axial movements of the piston with respect to the cylinder, and to resist this flow, the first end being configured to allow fluid to flow from the compression chamber to the compensation chamber and vice versa due to the axial movements of the piston, and
• - a gas located in the balancing chamber to exert a back pressure on the liquid.

The invention also relates to a vehicle, in particular a rail vehicle, comprising at least one such damper, and a method for venting such a damper.

In a hydraulic damper, the viscous fluid flows through small orifices from the compression chamber into the extension chamber as the rod approaches the cylinder and from the extension chamber into the compression chamber as the rod moves away from the cylinder. These flows cause viscous friction, which dissipates mechanical energy in the form of heat.

Due to the changing volume of the rod in the inner socket, the sum of the volumes of the compression chamber and the expansion chamber that are accessible to the hydraulic fluid changes. The compensating chamber acts as a reserve, taking over-inflation when the shock is compressed and adding fluid when the shock is relaxed. The gas compressed above the liquid in the balance chamber creates a back pressure.

With such a damper, however, it can happen, particularly during or after commissioning, that residual gas is present in the compression chamber and/or in the expansion chamber. The presence of these gases will adversely affect damping characteristics and damper life. In addition, an emulsion of the gas and the hydraulic fluid can occur, which also impairs the function of the damper.

To prevent these problems, the balance chamber on some railcars includes an air-filled bag that provides back pressure while preventing air from migrating to the other chambers of the damper. However, this solution is relatively expensive and sometimes causes reliability problems.

It is therefore an object of the invention to provide a hydraulic damper which is more reliable and at the same time remains inexpensive.

• - einen Zylinder, der eine Achse des Dämpfers und eine innere Aufnahme definiert,
• - einen Kolben, der in der inneren Aufnahme axial verschiebbar ist, und eine Stange, die sich axial erstreckt und an dem Kolben befestigt ist, und
• - ein erstes axiales Ende und ein zweites axiales Ende axial gegenüber dem ersten Ende;

wobei der Zylinder, das erste Ende und der Kolben eine Druckkammer des Dämpfers definieren; der Zylinder, das zweite Ende, und der Kolben eine Ausdehnungskammer des Dämpfers definieren; wobei der Dämpfer ferner Folgendes umfasst:

• - eine Ausgleichskammer,
• - eine Flüssigkeit, die sich in der Kompressionskammer, der Ausdehnungskammer und der Ausgleichskammer befindet, wobei der Kolben konfiguriert ist, um aufgrund der axialen Bewegungen des Kolbens in Bezug auf den Zylinder eine Strömung der Flüssigkeit von der Ausdehnungskammer zu der Kompressionskammer und umgekehrt zuzulassen, und um dieser Strömung einen Widerstand entgegenzusetzen, wobei das erste Ende konfiguriert ist, um der Flüssigkeit zu ermöglichen, aufgrund der axialen Bewegungen des Kolbens von der Kompressionskammer in die Ausgleichskammer und umgekehrt zu fließen, und
• - ein Gas, das sich in der Ausgleichskammer befindet, um einen Gegendruck auf die Flüssigkeit auszuüben,

wobei der Dämpfer einen Durchgang zwischen der Ausdehnungskammer und der Ausgleichskammer definiert, wobei das zweite Ende ein poröses Element umfasst, das den Durchgang versperrt und eingerichtet ist, um zuzulassen, dass ein Restgas von der Ausdehnungskammer über den Durchgang zu der Ausgleichskammer strömen kann, während sich der Kolben zu dem zweiten Ende hin bewegt, wobei das poröse Element eingerichtet ist, um eine Strömung der Flüssigkeit von der Ausdehnungskammer zur Ausgleichskammer über den Durchgang einen Widerstand entgegenzusetzen, während sich der Kolben zu dem zweiten Ende bewegt, wobei der Widerstand, der durch das poröse Element entgegengesetzt wird, größer ist als der Widerstand, der durch den Kolben entgegengesetzt wird.To this end, the subject of the invention is a hydraulic damper comprising:

• - a cylinder defining an axis of the damper and an internal housing,
• - a piston axially slidable in the internal housing and a rod extending axially and fixed to the piston, and
• - a first axial end and a second axial end axially opposite the first end;

wherein the cylinder, the first end and the piston define a pressure chamber of the damper; the cylinder, the second end, and the piston define an expansion chamber of the damper; wherein the damper further comprises:

• - a compensation chamber,
• - a liquid located in the compression chamber, the expansion chamber and the balancing chamber, wherein the piston is configured to allow a flow of the liquid from the expansion chamber to the compression chamber and vice versa due to the axial movements of the piston with respect to the cylinder, and to resist this flow, wherein the first end is configured to allow fluid to flow from the compression chamber to the balance chamber and vice versa due to the axial movements of the piston, and
• - a gas located in the balancing chamber to exert a back pressure on the liquid,

wherein the damper defines a passageway between the expansion chamber and the balance chamber, the second end including a porous member that obstructs the passageway and is configured to allow residual gas to flow from the expansion chamber to the balance chamber via the passageway while the piston moves towards the second end, the porous element being arranged to resist a flow of liquid from the expansion chamber to the compensation chamber via the passageway as the piston moves towards the second end, the resistance caused by the porous element is greater than the resistance offered by the piston.

• - der Widerstand, den das poröse Element einer Strömung der Flüssigkeit von der Ausdehnungskammer zur Ausgleichskammer entgegensetzt, ist mindestens 10 Mal, vorzugsweise mindestens 50 Mal und noch bevorzugter mindestens 100 Mal größer als der Widerstand, der von dem Kolben entgegengesetzt wird;
• - das poröse Medium umfasst einen Metall- oder Keramikschaum;
• - das zweite Ende definiert eine Aufnahme und das poröse Element ist in die Aufnahme verspannt montiert;
• - das poröse Element ist zwischen mindestens zwei verschiedenen Teilen des zweiten Endes verspannt montiert;
• - der Durchgang, der durch den Dämpfer gebildet wird, umfasst nacheinander in der Richtung von der Ausdehnungskammer zu der Ausgleichskammer einen stromaufwärtigen Abschnitt, der durch eines der zwei Teile definiert ist, einen Zwischenabschnitt und einen stromabwärtigen Abschnitt, der durch das andere der zwei Teile definiert ist, wobei sich das poröse Element in dem Zwischenabschnitt befindet, wobei der stromaufwärtige Abschnitt eine stromaufwärtige Öffnung bildet, die in den Zwischenabschnitt mündet, und der stromabwärtige Abschnitt eine stromabwärtige Öffnung bildet, die in den Zwischenabschnitt mündet;
• - das poröse Element ist axial zwischen einem Körper des zweiten Endes und dem Zylinder verspannt montiert;
• - einen äußeren Zylinder, der den Zylinder um die Achse umgibt, wobei die Ausgleichskammer durch den äußeren Zylinder, das erste Ende und das zweite Ende definiert ist; und
• - die Flüssigkeit ist Öl und das Gas ist Luft.

According to particular embodiments, the damper includes one or more of the following features, alone or in any technically possible combination:

• - the resistance offered by the porous element to a flow of the liquid from the expansion chamber to the compensation chamber is at least 10 times, preferably at least 50 times and more preferably at least 100 times greater than the resistance offered by the piston;
• - the porous medium comprises a metal or ceramic foam;
• - the second end defines a seat and the porous element is mounted clamped into the seat;
• - the porous element is clamped between at least two different parts of the second end;
• - the passage formed by the damper comprises successively in the direction from the expansion chamber to the balancing chamber an upstream portion defined by one of the two parts, an intermediate portion and a downstream portion defined by the other of the two parts wherein the porous element is in the intermediate section, the upstream section forming an upstream opening opening into the intermediate section and the downstream section forming a downstream opening opening into the intermediate section;
• - the porous element is mounted clamped axially between a body of the second end and the cylinder;
• - an outer cylinder surrounding the cylinder about the axis, the balance chamber being defined by the outer cylinder, the first end and the second end; and
• - the liquid is oil and the gas is air.

The subject matter of the invention is a vehicle, in particular a rail vehicle, comprising at least one damper as described above.

• - wenn ein erstes Restgas in der Kompressionskammer vorhanden ist, Bewegen des Kolbens in Richtung des ersten Endes, um das erste Restgas von der Kompressionskammer über den Kolben in die Ausdehnungskammer zu leiten; und
• - Bewegen des Kolbens in Richtung des zweiten Endes, um ein zweites Restgas aus der Erweiterungskammer über das poröse Element in die Ausgleichskammer zu leiten.

The invention also relates to a venting method for a damper as described above, comprising the following steps:

• - when a first residual gas is present in the compression chamber, moving the piston towards the first end to direct the first residual gas from the compression chamber via the piston into the expansion chamber; and
• - moving the piston toward the second end to direct a second residual gas from the expansion chamber into the balance chamber via the porous element.

• - 1 eine perspektivische Ansicht eines Fahrzeugs gemäß der Erfindung ist,
• - 2 eine Schnittansicht eines in 1 dargestellten Dämpfers ist,
• - 3 und 4 analoge Ansichten wie in 2 sind und jeweils zwei Schritte eines Entlüftungsverfahrens gemäß der Erfindung veranschaulichen,
• - 5 eine Schnittansicht eines Dämpfers ist, der eine erste Variante des in 1 bis 4 dargestellten Stoßdämpfers darstellt, und
• - 6 eine Schnittansicht eines Dämpfers ist, der eine zweite Variante des in 1 bis 4 dargestellten Stoßdämpfers darstellt.

The invention will be better understood on reading the following description, given by way of non-limiting example, with reference to the attached drawings, in which:

• - 1 Figure 12 is a perspective view of a vehicle according to the invention,
• - 2 a sectional view of an in 1 damper shown is
• - 3 and 4 analogous views as in 2 and each illustrate two steps of a venting method according to the invention,
• - 5 is a sectional view of a damper, which is a first variant of the in 1 until 4 illustrated shock absorber represents, and
• - 6 is a sectional view of a damper, which is a second variant of the in 1 until 4 illustrated shock absorber represents.

With reference to 1 a vehicle 10, in particular a rail vehicle, is described according to the invention.

The vehicle 10 includes at least one hydraulic damper 12 according to the invention.

The damper 12 is located, for example, between a bogie and a body structure (not shown) of the vehicle 10, or between two vehicles (not shown) of the vehicle, or between two moving elements with which the vehicle 10 is equipped (e.g. dampers a pantograph).

like it in 2 As can be seen, the damper 12 has, for example, a cylindrical shape.

The damper 12 includes an inner cylinder 14 defining an X-axis of the damper and an inner socket 16, a piston 18 axially slidable in the inner socket 16, and an axially extending rod 20 fixed to the piston is. The damper 12 includes a first axial end 22 and a second axial end 24 axially opposite the first end, with the rod 20 being slidably mounted in the second end, for example.

The damper 12 includes on the one hand a compression chamber 26 defined by the cylinder 14, the first end 22 and the piston 18 and on the other hand an expansion chamber 28 defined by the inner cylinder 14, the second end 24 and the piston 18.

The damper 12 includes a balance chamber 30 advantageously defined by the first end 22, the second end 24, and an outer cylinder 32 surrounding the inner cylinder 14 about the X-axis.

The damper 12 includes a liquid 34, e.g. B. an oil, which is in the compression chamber 26, the expansion chamber 28 and the equalization chamber 30 is located. The damper 12 also includes a gas 36, e.g. B. air, which is located in the compensation chamber 30 to exert a back pressure P on the liquid 34.

The damper 12 defines a passage 38 between the expansion chamber 28 and the balance chamber 30, the passage 38 being formed only by the second end 24 in the illustrated example.

The compression chamber 26, located in 2 located below the piston 18, extends axially between the piston and the first end 22, and is bounded radially with respect to the X-axis by the cylinder 14.

The expansion chamber 28, located in 2 located above the piston 18, extends axially between the piston and the second end 24, and is bounded radially by the cylinder 14.

The balance chamber 30 extends axially between the first end 22 and the second end 24 and radially between the inner cylinder 14 and the outer cylinder 32.

In variants not shown, the expansion chamber 30 is not defined by a cylindrical outer shell, but takes on other shapes (not shown).

The first end 22, the outer cylinder 32 and the second end 24 form z. B. a body 40 of the damper 12, wherein the body z. B. is attached to a bogie of the vehicle 10 .

The first end 22 is attached to the outer cylinder 32 and advantageously to the inner cylinder 14 .

The first end 22 is configured to allow the fluid 34 to flow from the compression chamber 26 to the balance chamber 30 and vice versa due to the axial movements of the piston 18 . For example, the first end 22 forms a passage 42 for the liquid 34 between the compression chamber 26 and the compensation chamber 30. Thus, at least during use of the damper 12, the first end 22 is below the second end 24 so that the passage 42 with the liquid 24 is filled.

In a variant that is not shown, the passage 42 is not defined in the first end 22 but between the first end and the cylinder 14 .

The second end 24 is attached to the outer cylinder 32 and the inner cylinder 14 . The second end 24 includes a porous member 44 blocking the passageway 38 .

In the example, the second end 24 is traversed axially by the rod 20, which is thus directed more upwards.

The rod 20 is attached to a (not shown) portion of the vehicle, z. a body structure, while the body 40 of the damper 12 is attached to another portion (not shown), e.g. B. a bogie attached.

In a variant that is not shown, the rod 20 passes axially through the first end 22 and not through the second end 24. In this case, the rod 20 is e.g. B. attached to a bogie and the body 40 to the car body structure.

The piston 18 separates the compression chamber 26 and the expansion chamber 28 axially each other. The piston 18 is configured to allow fluid 34 to flow from the expansion chamber 28 into the compression chamber 26 and vice versa due to the axial movements of the piston 18 relative to the cylinder 14 . The piston 18 is also configured to resist this flow.

In the example, the piston 18 includes a first system 46 for allowing a fluid located in the compression chamber 26 to pass to the expansion chamber 28, the fluid being the liquid 34 ( 2 ) or a first residual gas 48 ( 3 ) located above the liquid 34 against the piston 18. The piston 18 also includes a second system 50 to supply the liquid 34 ( 2 ) located in the extension chamber 28 above the piston 18 to allow passage to the compression chamber 26.

The first system 46 and the second system 50 are advantageously structurally analogous to each other, therefore only the first system 46 will be described below.

The first system 46 includes a passage 52 defined by the piston 18 from the compression chamber 26 to the expansion chamber 28, a stopper 54 located at an entrance 56 of the passage 52, and a return member 58.

The locking piece 54 is between a rest position ( 2 ) in which it blocks passage 52 and an active position in which fluid is allowed to pass from compression chamber 26 to expansion chamber 28.

The reset member 58, z. B. a spring, is arranged to return the locking piece 54 to the rest position by exerting a back pressure P1 on the locking piece 54, which the fluid must overcome in order to pass.

In the example, passage 38 is defined by second end 24 . The second end 24 defines, for example, an axially extending, z. B. cylindrical seat 60 opening into the expansion chamber 28, and a radial duct 62 between the seat 60 and the compensation chamber 30.

The porous element 44 is, for example, clamped into the receptacle 60, mounted, glued or screwed or contained in a cartridge 64, which in turn is received, glued or screwed in the receptacle 60 with a non-positive fit.

The porous member 44 is configured to allow a second residual gas 66 ( 4 ) flows from expansion chamber 28 into balance chamber 30 via passage 38 as piston 18 moves toward second end 24 .

The porous element 44 is arranged to allow a flow of the liquid 34 ( 4 ) from the expansion chamber 28 via the passage 38 to the balance chamber 30 as the piston 18 moves toward the second end 24, this resistance being greater than the resistance the piston 18 imparts to the flow of fluid 34 from the Expansion chamber 28 to the compression chamber 26 opposite.

The residual gases 48, 66 come from z. B. from a portion of the gas 36 that would have migrated from the equalization chamber 30 into the inner receptacle 16.

The resistance presented to the passage of a fluid through a conduit can be detected by a characteristic known to those skilled in the art that relates the flow of the fluid to the pressure drop (or pressure difference) between the inlet and the outlet of the conduit puts. Thus, for the same pressure differential, the porous member 44 is structurally arranged to pass less liquid 34 from the expansion chamber 28 to the balance chamber 30 than the piston 18 from the expansion chamber 28 to the compression chamber 26 at the same time.

According to a particular embodiment, the resistance that the porous element 44 offers to the liquid 34 is at least 10 times, preferably at least 50 times and more preferably at least 100 times greater than the resistance that the piston 18 offers to the liquid 34 .

According to a particular mode, the porous element 44 is impermeable to the liquid 34 .

The porous element 44 advantageously consists of a metal foam and/or a ceramic foam. The foam is selected, for example, from a copper foam, an aluminum foam, a carbon foam or a silicon carbide foam. This material is z. B. obtained by a casting process or an additive manufacturing process.

The foam has open pores and preferably an isotropic structure.

For example, when the foam is metallic in nature, the pore density is between 5 and 40 PPI (pores per inch, where one inch equals 2.54 cm). A value of about 40 PPI is preferred.

For example, if the foam is carbon or ceramic in nature, the pore density is between 5 and 100 PPI.

Uncompressed foam has an equivalent apparent density (including pores) between 2% and 20% of the density of the solid material of which it is made (i.e. without pores). Stated another way, the pores represent between 80% and 98% of the volume of the foam. Preferably, the density of the uncompressed foam is between 6% and 8% of the density of this solid material.

Preferably, the porous member 44 is in a compressed state in which the volume of the foam is reduced by a factor of between 2 and 5 compared to the uncompressed foam. This brings the apparent density of the porous element 44 preferably between 12% and 40% of the density of the solid material making up the foam.

The porous element 44 has, for example, on the expansion chamber 28 side, an active diameter (inlet diameter subjected to the hydraulic pressure of the expansion chamber 28) between 1 mm and 10 mm.

The porous member 44 has a height of 1 mm to 15 mm along the X-axis and a diameter of 1 mm to 10 mm, for example.

The operation of the damper 12 will now be briefly described.

In normal operation ( 2 ) there is no gas (gas sky) in the compression chamber 26 and neither in the expansion chamber 28. The compression chamber 26 and the expansion chamber 28 are completely filled with the liquid 34.

As the rod 20 pushes the piston 18 toward the first end 22 (in 2 downwards), the pressure of the liquid 34 in the compression chamber 26 increases and liquid 34 flows (arrow F1) from the compression chamber 26 via the first system of the piston 18 into the expansion chamber 28.

Due to the rod 20, the increase in the volume of the expansion chamber 28 does not compensate for the decrease in the volume of the compression chamber 26, therefore liquid 34 present in the compression chamber 26 flows through the passage 42 (arrow F2) and enters the compensation chamber 30, which acts as an expansion vessel. The boundary 68 between liquid 34 and gas 36 rises again in the compensation chamber 30 .

The pressure difference between the gas 36 in the equalization chamber 30 and the liquid 34 in the expansion chamber 28 on both sides of the porous element 44 is such that the gas 36 does not or only slightly passes through the porous element 44 into the expansion chamber 28 . This is achieved, for example, by having a relative pressure ratio in the range of 2 to 10 between the equalization chamber 30 and the expansion chamber 28 .

As the rod 20 pushes the piston 18 toward the second end 24 (in 2 upwards), the pressure of the liquid 34 in the expansion chamber 28 increases and liquid 34 flows (arrow F3) from the expansion chamber 28 via the second system 50 of the piston into the compression chamber 26.

Due to the rod 20, the increase in the volume of the compression chamber 26 is greater than the decrease in the volume of the expansion chamber 28, resulting in a suction (arrow F4) of the liquid 34 present in the equalizing chamber 30 towards the compression chamber 26. The boundary 68 between liquid 34 and gas 36 sinks in the compensation chamber 30.

Because the resistance of the porous medium 44 to a passage of the liquid 34 from the expansion chamber 28 into the compensation chamber 30 is greater or even much greater than the resistance offered by the piston 18, the liquid 34 does not reach the expansion chamber 28 or only to a small extent through the porous medium 44 into the compensation chamber 30 and preferably reaches the compression chamber 26 via the piston 18.

A deaeration method according to the invention will now be described.

The method employs the damper 12 .

When the first residual gas 48 in the compression chamber 26 ( 3 ) is present, the piston 18 is moved in a first step towards the first end 22 in order to direct (arrow F5) the first residual gas 48 from the compression chamber 26 into the expansion chamber 28 via the piston 18. then the piston becomes 18 ( 4 ) is moved in a second step toward the second end 24 to direct (arrow F6) the second residual gas 66 from the expansion chamber 28 via the porous member 44 into the equalization chamber 30.

As can be seen, in the invention, the passage of the second residual gas 66 through the porous medium 44 is advantageously due only to the increase in pressure in the expansion chamber 28 caused by the axial displacement of the piston 18 towards the second end 24.

According to one embodiment, the first step and the second step are repeated, possibly multiple times, until all of the first residual gas 48 has been directed from the compression chamber 26 to the expansion chamber 28 and all of the second residual gas 66 has been directed from the expansion chamber 28 to the compensation chamber 30 .

In order to carry out the first step and the second step, the rod 20 is acted on by means which are not shown, e.g. B. by a repeated pull/compression test applied to the damper.

If there is no residual gas in the compression chamber 26 (as in 1 ), the first step is not carried out and the second step is started directly. In this case, according to a particular embodiment, the second step is repeated, possibly several times. The piston 18 may be moved toward the first end 22 between each of these steps.

As can be appreciated, the bleeding process may be performed "naturally" while the damper 12 is in operation, by reciprocating movement of the piston 18 within the inner socket 16. The damper 12 is thus configured to continually self-bleed .

Thanks to the features described above, in particular the porous element 44, the damper 12 normally does not contain residual gases in the compression chamber 26 or in the expansion chamber 28. The damper is therefore more reliable and at the same time inexpensive.

If the damper 12 contains residual gases, it can be easily purged of those gases by the venting process described above.

With reference to 5 a damper 112 is described, which represents a first variant of the damper 12 . The damper 112 is similar to the damper 12 shown in 1 until 4 is shown. Similar elements have the same reference numbers and will not be described again. Only the differences are described in detail below.

In the case of the damper 112, the porous element 44 is not mounted clamped directly into the second end, but rather between two separate parts 102, 104 of the second end 24.

One of the two parts 102, 104 is z. B. a body of the first end, and the other of the two parts is a fastening part, the z. B. is screwed axially into the body.

For example, the passageway 38 includes sequentially, in the flow direction from the expansion chamber 28 to the balance chamber 30, an upstream portion 106 defined by the mounting member, an intermediate portion 108, and a downstream portion 110 defined by the body.

The porous element 44 is located in the intermediate section 108. For example, in section along a radial plane (plane in 5 ) has a rectangular shape.

The upstream section 106 defines an upstream opening 112 opening into the intermediate section 108 and the downstream section 110 defines a downstream opening 114 opening into the intermediate section 108 . In other words, the intermediate portion 108 forms an enlargement which promotes fluid sealing around the porous element 44 .

With reference to 6 a damper 212 is described which represents a second variant of the damper 12 . The damper 212 is similar to the damper 12 shown in 1 until 4 is shown. Similar elements have the same reference numbers and will not be described again. Only the differences are described in detail below.

In the damper 212, the passage is not defined in the second end 24 but is between the second end 24 and the inner cylinder 14.

The second end 24 forms a receptacle 202 which receives the porous element 44 .

The porous member 44 extends axially between a body 204 of the second end 24 and the inner cylinder 14. The porous member 44 is advantageously axially compressed between the second end 22 and the inner cylinder 14. As shown in FIG. For example, the porous element 44 has a section along a radial plane (plane in 6 ) has a rectangular cross-section rotating around the X-axis.

Claims (8)

Hydraulic damper (12; 112; 212) comprising: - a cylinder (14) defining an axis (X) of the damper (12; 112; 212) and an internal housing (16), - a piston (18) axially slidable in the internal housing (16) and a rod (20) extending axially and fixed to the piston (18), and - a first axial end (22) and a second axial end (24) axially opposite the first end (22); the cylinder (14), the first end (22) and the piston (18) defining a compression chamber (26) of the damper (12; 112; 212); the cylinder (14), the second end (24), and the piston (18) define an expansion chamber (28) of the damper (12; 112; 212); the damper (12; 112; 212) further comprising: - a compensating chamber (30), - a liquid (34) located in the compression chamber (26), the expansion chamber (28) and the balancing chamber (30), wherein the piston (18) is configured to relative to due to the axial movements of the piston (18). on the cylinder (14) to allow flow of the liquid (34) from the expansion chamber (28) to the compression chamber (26) and vice versa and to resist that flow, the first end (22) being configured to flow the liquid (34) to allow flow from the compression chamber (26) to the equalization chamber (30) and vice versa due to the axial movements of the piston (18), and - a gas (36) located in the equalization chamber (30) to exert a back pressure (P) on the liquid (34), where: - the damper (12; 112; 212) defines a passage (38) between the expansion chamber (28) and the compensation chamber (30), the second end (24) comprising a porous element (44) which defines the passage (38) blocked and arranged to allow residual gas (66) to flow from the expansion chamber (28) to the balance chamber (30) via the passage (38) as the piston (18) moves toward the second end (24). moves, the porous element (44) being arranged to resist a flow of the liquid (34) from the expansion chamber (28) to the compensation chamber (30) via the passage (38) while the piston (18) moves towards the moves the second end (24) with the resistance offered by the porous element (44) being greater than the resistance offered by the piston (18), - the porous element (44) is mounted clamped between at least two different parts (102, 104) of the second end (24), and - the passage (38) formed by the damper (112) has, successively in the direction from the expansion chamber (28) to the compensation chamber (30), an upstream portion (106) passing through one of the two parts (102, 104 ) is defined, comprises an intermediate section (108) and a downstream section (110) defined by the other of the two parts (102, 104), wherein the porous element (44) is in the intermediate section (108), the upstream section (106) forming an upstream opening (112) opening into the intermediate section (108) and the downstream section (110) forming a downstream opening (114) opening into the intermediate section (108). Dampers (12; 112; 212) according to claim 1 , wherein the resistance offered by the porous element (44) to flow of the liquid (34) from the expansion chamber (28) to the compensation chamber (30) is at least 10 times, preferably at least 50 times and more preferably at least 100 times greater than that Resistance opposed by the piston (18). Dampers (12; 112; 212) according to claim 1 or 2 , wherein the porous medium comprises a metal or ceramic foam. Damper (12) according to one of Claims 1 until 3 wherein the second end (24) defines a socket (60) and the porous member (44) is clamped into the socket (60). Damper (212) according to one of Claims 1 until 4 wherein the porous element (44) is mounted clamped axially between a body (204) of the second end (24) and the cylinder (14). Damper (12; 112; 212) according to one of Claims 1 until 5 , comprising an outer cylinder (32) surrounding the cylinder (14) about the axis (X), the balance chamber (30) defined by the outer cylinder (32), the first end (22) and the second end (24) is defined. Vehicle (10), in particular rail vehicle, comprising at least one damper (12; 112; 212) according to one of Claims 1 until 6 . Bleeding method of a damper (12; 112; 212) according to one of Claims 1 until 6 , comprising the steps of: - when a first residual gas (48) is present in the compression chamber (26), moving the piston (18) towards the first end (22) to remove the first residual gas (48) from the compression chamber (26 ) via the piston (18) into the expansion chamber (28); and - moving the piston (18) toward the second end (24) to direct a second residual gas (66) from the expansion chamber (28) through the porous member (44) into the equalization chamber (30).

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