CN115143220A

CN115143220A - Hydraulic damper with apertured member

Info

Publication number: CN115143220A
Application number: CN202210341631.4A
Authority: CN
Inventors: 雅松·蒂西耶
Original assignee: Alstom Holdings SA
Current assignee: Alstom Holdings SA
Priority date: 2021-03-29
Filing date: 2022-03-29
Publication date: 2022-10-04
Also published as: DE102022107345A1; FR3121189B1; FR3121189A1

Abstract

The invention provides a hydraulic damper (12) with a perforated element, comprising: a cylinder (14), a piston (18), a compression chamber (26) and an expansion chamber (28), separated by the piston, a compensation chamber (30). A fluid (34) flowing between the compression chamber, the expansion chamber and the compensation chamber (30) due to the movement of the piston, a gas (36) located in the compensation chamber to exert a back pressure (P) on the liquid. The damper defines a passage (38) between the expansion chamber and the compensation chamber, the apertured element (44) blocking the passage and being adapted to allow residual gas to flow from the expansion chamber towards the compensation chamber and to apply a resistance to the flow of fluid from the expansion chamber towards the compensation chamber.

Description

Hydraulic damper with apertured member

Technical Field

The invention relates to a hydraulic damper, comprising: :

a cylinder defining an axis of the damper and an internal housing,

a piston which is axially movable in translation in the inner housing, and a rod which extends axially and is fixed to the piston, an

-a first axial end and a second axial end axially opposite the first axial end;

the cylinder, the first end and the piston define a compression chamber of the damper; the inner cylinder, the second end and the piston define an expansion chamber of the damper.

The damper also includes

-a compensation chamber;

-a liquid located in the compression chamber, the expansion chamber and the compensation chamber, the piston being configured to allow the liquid to flow from the expansion chamber towards the compression chamber and vice versa and to exert a resistance to this flow as a result of the axial movement of the piston relative to the cylinder, the first end being configured to allow the liquid to flow from the compression chamber towards the compensation chamber and vice versa as a result of the axial movement of the piston, and

-a gas located in the compensation chamber to exert a back pressure on the liquid.

The invention also relates to a vehicle, in particular a railway vehicle, comprising at least one such damper; and a method of exhausting such a damper.

Background

In the hydraulic damper, when the rod approaches the cylinder, the viscous liquid flows from the compression chamber to the expansion chamber through the orifice, and when the rod moves away from the cylinder, the viscous liquid flows from the expansion chamber to the compression chamber. These flows result in viscous friction, which dissipates mechanical energy in the form of heat.

Due to the varying volume of the rod in the inner housing, the sum of the volumes of the compression chamber and the expansion chamber into which the hydraulic liquid can enter also varies. The compensation chamber acts as a reservoir to draw in excess liquid when the damper is compressed and to provide liquid when the damper is expanded. The gas compressed above the liquid in the compensation chamber ensures a back pressure.

However, in such dampers, it may happen that residual gas is present in the compression chamber and/or expansion chamber, in particular at or after activation. The presence of these gases will affect the damping characteristics and the life of the damper. Furthermore, emulsification of the gas and hydraulic fluid may occur, which also affects the operation of the damper.

To prevent these problems, in some rail vehicles, the compensation chamber comprises a bladder filled with air, which ensures a back pressure while preventing air from migrating into the other chambers of the damper. However, this solution is relatively expensive and sometimes causes reliability problems.

Disclosure of Invention

It is therefore an object of the present invention to provide a hydraulic damper which is more reliable while maintaining moderate costs.

To this end, the invention relates to a hydraulic damper comprising: :

a cylinder defining an axis of the damper and an internal housing,

-a first axial end and a second axial end axially opposite the first axial end;

The damper also includes

-a compensation chamber;

-a gas, the gas being, which is located in the compensation chamber to exert a back pressure on the liquid.

Wherein the damper defines a passage between the expansion chamber and the compensation chamber, the second end comprising a perforated element blocking the passage and adapted to allow residual gas to flow from the expansion chamber to the compensation chamber via the passage upon displacement of the piston beyond the second end. The perforated member is adapted to apply a resistance to the flow of fluid through the passage from the expansion chamber toward the compensation chamber upon displacement of the piston beyond the second end, the resistance applied by the perforated member being greater than the resistance applied by the piston.

According to a particular embodiment, the damper comprises one or more of the following features, which can be used alone or in any technically possible combination:

-the perforated element exerts a resistance to the flow of liquid from the expansion chamber towards the compensation chamber which is at least 10 times, preferably at least 50 times, and more preferably at least 100 times the resistance exerted by the piston;

-the porous medium comprises a metal or ceramic foam;

the second end defines a housing in which the apertured member is clamped;

the apertured member is clamped between at least two different parts of the second end;

-said passage formed by the damper comprises, in sequence in the direction from the expansion chamber to the compensation chamber: an upstream section defined by one of the two parts, an intermediate section in which the apertured element is located, the upstream section forming an upstream aperture to the intermediate section and the downstream section forming a downstream aperture to the intermediate section, and a downstream section defined by the other of the two parts.

The apertured member is axially clamped between the body of the second end and the cylinder;

-an outer cylinder surrounding the cylinder about the axis, the compensation 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 invention relates to a vehicle, in particular a railway vehicle, comprising at least one damper as described above.

The invention also relates to an exhaust method of the damper, which comprises the following steps:

-if a first residual gas is present in the compression chamber, displacing the piston towards the first end to pass the first residual gas from the compression chamber to the expansion chamber via the piston; and

-moving the piston towards the second end to pass the second residual gas from the expansion chamber to the compensation chamber via the apertured element.

Drawings

The invention will be better understood from a reading of the following description, given by way of example only and made with reference to the accompanying drawings, in which:

figure 1 is a schematic view of a vehicle according to the invention,

figure 2 is a cross-sectional view of the damper shown in figure 1,

figures 3 and 4 are views similar to figure 2 and respectively show two stages of the exhaust process according to the invention,

FIG. 5 is a cross-sectional view of a damper constituting a first variant of the damper shown in FIGS. 1 to 4, an

Figure 6 is a cross-sectional view of a damper constituting a second variant of the damper shown in figures 1 to 4.

Detailed Description

Referring to FIG. 1, a vehicle 10, particularly a railway vehicle, is depicted in accordance with the present invention.

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

For example, damper 12 is located between a bogie and a body structure (not shown) of vehicle 10, or between two cars (not shown) of the vehicle, or between two movable elements equipping vehicle 10 (e.g., a pantograph damper).

As can be seen in fig. 2, the damper 12 is, for example, cylindrical in shape.

Damper 12 comprises an internal cylinder 14 defining an axis X of the damper and an internal housing 16; a piston 18 axially movable in translation in the internal housing 16; and a rod 20 extending axially and fixed to the piston. The damper 12 includes a first axial end 22 and a second axial end 24 opposite the first axial end, in which the rod 20 is, for example, slidably mounted.

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

Damper 12 comprises a compensation chamber 30, which is advantageously defined by a first end 22, a second end 24 and an outer cylinder 32 surrounding inner cylinder 14 about axis X.

The damper 12 includes a liquid 34, such as oil, located in the compression chamber 26, the expansion chamber 28, and the compensation chamber 30. The damper 12 also includes a gas 36, such as air, 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 compensation chamber 30, which passage 38 is formed by the second end 24 only in the example shown.

A compression chamber 26, which is located below the piston 18 in fig. 2, extends axially between the piston and the first end 22 and is radially delimited by the cylinder 14.

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

The compensation 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.

According to a variant not shown, the expansion chamber 30 is not defined by a cylindrical outer casing, but takes another shape (not shown).

The first end 22, the outer cylinder 32 and the second end 24 form, for example, a body 40 of the damper 12, which is fixed, for example, to a bogie of the vehicle 10.

The first end 22 is fixed to the external cylinder 32 and advantageously to the internal cylinder 14.

First end 22 is configured to allow fluid 34 to flow from compression chamber 26 toward compensation chamber 30 and vice versa due to axial movement of 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 located below the second end 24 such that the passage 42 is filled with the liquid 24.

In a variant 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 fixed to the outer cylinder 32 and the inner cylinder 14. The second end 24 includes an apertured member 44 blocking the passage 38.

In this example, the second end 24 is axially crossed by the rod 20, which is therefore directed exactly upwards.

The rod 20 is secured to one part of the vehicle (not shown), such as a vehicle body structure, and the body 40 of the damper 12 is secured to another part (not shown), such as a truck.

In another embodiment, not shown, the rod 20 passes axially through the first end 22 rather than the second end 24. In this case, the rod 20 is fixed to, for example, a bogie, and the body 40 is fixed to the vehicle body structure.

The piston 18 axially separates the compression chamber 26 and the expansion chamber 28. The piston 18 is configured to allow the fluid 34 to flow from the expansion chamber 28 toward the compression chamber 26 and vice versa due to axial movement of the piston 18 relative to the cylinder 14. The piston 18 is also configured to apply resistance to such flow.

In an example, the piston 18 includes a first system 46 to allow a fluid located in the compression chamber 26, which is the liquid 34 (fig. 2), or a first residual gas 48 located above the liquid 34 (fig. 3) to pass against the piston 18 toward the expansion chamber 28. The piston 18 also includes a second system 50 to allow the passage of the liquid 34 (fig. 2) in the expansion chamber 28 above the piston 18 towards the compression chamber 26.

Advantageously, the first system 46 and the second system 50 are similar in structure to each other, so only the first system 46 will be described below.

First system 46 includes a passage 52 defined by piston 18 from compression chamber 26 toward expansion chamber 28, a stop 54 at an inlet 56 of passage 52, and a return device 58.

Under the pressure differential between the compression chamber 26 and the distending chamber 28, the barrier 54 is movable relative to the passageway 52 between a resting position (FIG. 2) in which it blocks the passageway, and an activated position; in the activated position, the barrier allows fluid to pass from the compression chamber 26 into the expansion chamber 28.

The return means 58 (e.g. a spring) is adapted to return the barrier towards the rest position by exerting a back pressure P1 on the barrier 54 through which the fluid should overcome.

In the example, the channel 38 is defined by the second end 24. The second end 24 defines, for example, a receptacle 60 extending axially (e.g., cylindrical) and opening into the expansion chamber 28, and a radial conduit 62 between the receptacle 60 and the compensation chamber 30.

For example, the apertured member 44 is clamped, glued or screwed into the receptacle 60, or contained within a sleeve 64 that is itself force, glued or screwed into the receptacle 60.

The apertured member 44 is adapted to allow a second residual gas 66 (fig. 4) to flow from the expansion chamber 28 toward the compensation chamber 30 via the passage 38 upon displacement of the piston 18 toward the second end 24.

The apertured member 44 is adapted to apply a resistance to the flow of liquid 34 (fig. 4) from the expansion chamber 28 toward the compensation chamber 30 via the passage 38 upon displacement of the piston 18 toward the second end 24 that is greater than the resistance applied by the piston 18 to the passage of liquid 34 from the expansion chamber 28 toward the compression chamber 26.

The

residual gases

48, 66 come, for example, from a portion of the gas 36 migrating from the compensation chamber 30 toward the inner housing 16.

The resistance exerted by the conduit to the passage of fluid can be understood by a characteristic curve known to those skilled in the art that relates the flow rate of the fluid to the pressure drop (or pressure difference) between the inlet and outlet of the conduit. Thus, for the same pressure differential, the apertured member 44 is structurally adapted to pass less liquid 34 from the expansion chamber 28 toward the compensation chamber 30 than the piston 18 passes from the expansion chamber 28 toward the compression chamber 26 at the same time.

According to a particular embodiment, the resistance exerted by the apertured member 44 on the liquid 34 is at least 10 times, preferably at least 50 times, and even more preferably at least 100 times the resistance exerted by the piston 18 on the liquid 34.

According to a particular mode, the apertured member 44 is impermeable to the liquid 34.

Advantageously, the foraminous element 44 is made of metal foam and/or ceramic foam. For example, the foam is selected from copper foam, aluminum foam, carbon foam, or silicon carbide foam. Such a material is obtained, for example, by casting or additive manufacturing methods.

The foam has open pores and preferably has an isotropic structure.

If the foam is metallic in nature, the pore density is, for example, between 5 and 40PPI ("pores per inch" in English, i.e., 2.54 centimeters per inch). A value of about 40PPI is preferred.

If the foam is of carbon or ceramic nature, the pore density is for example between 5 and 100 PPI.

The corresponding apparent density of the uncompressed foam (taking into account the porosity) is between 2% and 20% of the density of the solid material of which it is composed (i.e. without porosity). In other words, the voids comprise 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 the solid material.

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

For example, on one side of the expansion chamber 28, the effective diameter of the apertured member 44 (the diameter of the inlet port that receives the hydraulic pressure of the expansion chamber 28) is between 1mm and 10 mm.

For example, the apertured member 44 has a height along the axis X of between 1mm and 15mm and a diameter of between 1mm and 10 mm.

The operation of damper 12 will now be briefly described.

In normal operation (fig. 2), there is no gas in the compression chamber 26 (gas cap) and no gas in the expansion chamber 28. The compression chamber 26 and the expansion chamber 28 are completely filled with the liquid 34.

When the rod 20 pushes the piston 18 towards the first end 22 (downwards in fig. 2), the pressure of the liquid 34 in the compression chamber 26 rises and the liquid 34 passes from the compression chamber 26 towards the expansion chamber 28 via the first system of pistons 18 (arrow F1).

The increase in volume of the expansion chamber 28 due to the rod 20 does not compensate for the decrease in volume of the compression chamber 26, so that the liquid 34 present in the compression chamber 26 passes (arrow F2) through the passage 42 and into the compensation chamber 30, which compensation chamber 30 acts as an expansion tank. The boundary 68 between the liquid 34 and the gas 36 rises in the compensation chamber 30.

The pressure difference between the gas 36 in the compensation chamber 30 and the liquid 34 in the expansion chamber 28 on both sides of the perforated element 44 is such that the gas 36 does not pass or only passes very little through the perforated element 44 towards the expansion chamber 28. This is achieved, for example, by means of a relative pressure ratio between the compensation chamber 30 and the expansion chamber 28 of about 2 to 10.

As the rod 20 pushes the piston 18 toward the second end 24 (upward in fig. 2), the pressure of the liquid 34 in the expansion chamber 28 rises and the liquid 34 passes from the expansion chamber 28 toward the compression chamber 26 via the second system 50 of pistons (arrow F3).

Due to the rod 20, the increase in volume of the compression chamber 26 is greater than the decrease in volume of the expansion chamber 28, which causes the liquid 34 present in the compensation chamber 30 to be drawn towards the compression chamber 26 (arrow F4). The boundary 68 between the liquid 34 and the gas 36 falls in the compensation chamber 30.

Since the porous medium 44 exerts a greater or much greater resistance to the passage of the liquid 34 from the expansion chamber 28 towards the compensation chamber 30 than the piston 18 exerts, the liquid 34 present in the expansion chamber 28 does not pass or passes very little through the porous medium 44 towards the compensation chamber 30 and preferably passes into the compression chamber 26 via the piston 18.

An exhaust method according to the present invention will now be described.

This method implements damper 12.

If the first residual gas 48 is present in the compression chamber 26 (fig. 3), in a first step, the piston 18 is displaced towards the first end 22 to transfer the first residual gas 48 from the compression chamber 26 to the expansion chamber 28 via the piston 18 (arrow F5). Then, in a second step, the piston 18 is displaced towards the second end 24 (fig. 4) to transfer the second residual gas 66 from the expansion chamber 28 to the compensation chamber 30 via the apertured element 44 (arrow F6).

It can be seen that in the present invention, the passage of the second residual gas 66 through the porous media 44 advantageously results in an increase in pressure in the expansion chamber 28 solely due to axial displacement of the piston 18 toward the second end 24.

According to an embodiment, the first and second steps are repeated, possibly a plurality of times, until all the first residual gas 48 passes from the compression chamber 26 into the expansion chamber 28 and all the second residual gas 66 passes from the expansion chamber 28 into the compensation chamber 30.

To carry out the first and second steps, the rod 20 is acted upon by means not shown, for example by repeated tensile/compression tests applied to the damper.

If there is no residual gas in the compression chamber 26 (as in fig. 1), the first step is not performed and the second step is started directly. In this case, the second step is repeated, possibly multiple times, according to a particular embodiment. Between each of these steps, the piston 18 may move toward the first end 22.

As will be appreciated, the venting process will eventually be "natural" as the damper 12 operates due to the alternating movement of the piston 18 within the interior pocket 16. Thus, the damper 12 is suitable for permanent automatic ventilation.

Due to the above-described features, particularly the apertured member 44, the damper 12 generally does not include residual gas in the compression chamber 26 or the expansion chamber 28. Therefore, the damper is more reliable, while maintaining a moderate cost.

If the damper 12 includes residual gases, these gases are easily exhausted by the above-described exhaust method.

Referring to fig. 5, there is described a damper 112 constituting a first modification of the damper 12. Damper 112 is similar to damper 12 shown in figures 1-4. Similar elements have the same reference numerals and will not be described again. Only the differences will be described in detail below.

In the damper 112, the apertured member 44 is not directly clip-mounted in the second end, but is instead clip-mounted between two

different parts

102, 104 of the second end 24.

One of the two

parts

102, 104 is for example a body of the first end and the other of the two parts is a fixed part, for example axially screwed in the body.

For example, the passage 38 includes, in order in the direction of flow from the expansion chamber 28 to the compensation chamber 30, an upstream section 106 defined by the static feature, an intermediate section 108, and a downstream section 110 defined by the body.

The apertured member 44 is located in the intermediate section 108. For example, the apertured member 44 has a rectangular shape in cross section along a radial plane (the plane of fig. 5).

The upstream section 106 forms an upstream orifice 112 that opens into the intermediate section 108, and the downstream section 110 forms a downstream orifice 114 that opens into the intermediate section 108. In other words, the intermediate section 108 forms an enlargement that promotes the tightness to fluids around the foraminous element 44.

Referring to fig. 6, a damper 212, which constitutes a second modification of the damper 12, is described. Damper 212 is similar to damper 12 shown in fig. 1-4. Similar elements have the same reference numerals and will not be described again. Only the differences will be described in detail below.

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

The second end 24 forms a receptacle 202 that receives the apertured member 44.

The apertured member 44 extends axially between the body 204 of the second end 24 and the inner cylinder 14. Advantageously, the apertured member 44 is axially compressed between the second end 22 and the inner cylinder 14. For example, the apertured member 44 has a cross-section in the radial plane (the plane of fig. 6) that is rectangular in rotation about the axis X.

Claims

1. A hydraulic damper (12:

-a cylinder (14) defining an axis (X) of the damper (12,

-a piston (18) axially movable in translation in the internal housing (16); and a rod (20) extending axially and fixed to the piston (18), an

-a first axial end (22) and a second axial end (24) axially opposite to the first axial end (22);

the cylinder (14), first end (22) and piston (18) defining a compression chamber (26) of the damper (12; the cylinder (14), second end (24) and piston (18) defining an expansion chamber (28) of the damper (12;

the damper (12:

-a compensation chamber (30),

-a liquid (34) located in the compression chamber (26), the expansion chamber (28) and the compensation chamber (30), the piston (18) being configured to allow the flow of the liquid (34) from the expansion chamber (28) towards the compression chamber (26) and vice versa and to exert a resistance to this flow as a result of the axial movement of the above-mentioned piston (18) relative to the cylinder (14), the first end (22) being configured to allow the flow of the liquid (34) from the compression chamber (26) towards the compensation chamber (30) and vice versa as a result of the axial movement of the piston (18), and

-a gas (36) located in the compensation chamber (30) to exert a back pressure (P) on the liquid (34),

wherein:

-the damper (12, 212) defining a passage (38) between the expansion chamber (28) and the compensation chamber (30), the second end (24) comprising a perforated element (44) blocking the passage (38) and adapted to allow a flow of residual gas (66) from the expansion chamber (28) towards the compensation chamber (30) via the passage (38) when the piston (18) is displaced towards the second end (24), the perforated element (44) being adapted to exert a resistance to a flow of the liquid (34) from the expansion chamber (28) towards the compensation chamber (30) via the passage (38) when the piston (18) is displaced towards the second end (24), the resistance exerted by the perforated element (44) being greater than the resistance exerted by the piston (18) above,

-the apertured member (44) is mounted clampingly between at least two different parts (102, 104) of the second end (24), and

-the passage (38) formed by the damper (112) comprises in succession, in the direction from the expansion chamber (28) to the compensation chamber (30): an upstream section (106) defined by one of the two pieces (102, 104), an intermediate section (108), and a downstream section (110) defined by the other of the two pieces (102, 104), the apertured element (44) being located in the intermediate section (108), the upstream section (106) forming an upstream aperture (112) leading to the intermediate section (108), and the downstream section (110) forming a downstream aperture (114) leading to the intermediate section (108).

2. The damper (12, 212) as set forth in claim 1 wherein the resistance exerted by said apertured element (44) to the flow of the liquid (34) from the expansion chamber (28) toward the compensation chamber (30) is at least 10 times the resistance exerted by the piston (18).

3. The damper (12, 212) as set forth in claim 1 wherein the resistance exerted by said apertured element (44) to the flow of the liquid (34) from the expansion chamber (28) toward the compensation chamber (30) is at least 50 times the resistance exerted by the piston (18).

4. The damper (12.

5. The damper (12.

6. A damper (12) as set forth in any of claims 1-5 wherein said second end (24) defines a receptacle (60) with said apertured member (44) clamp mounted in said receptacle (60).

7. The damper (212) of any of claims 1-5, wherein the apertured member (44) is axially clamped mounted between the body (204) of the second end (24) and the cylinder (14).

8. The damper (12.

9. A vehicle (10), in particular a railway vehicle, comprising at least one damper (12.

10. A method of venting a damper (12:

-if a first residual gas (48) is present in the compression chamber (26), displacing the piston (18) towards the first end (22) to pass the first residual gas (48) from the compression chamber (26) towards the expansion chamber (28) via the piston (18); and

-displacing the piston (18) towards the second end (24) to pass a second residual gas (66) from the expansion chamber (28) towards the compensation chamber (30) via the apertured element (44).