WO2021209282A1

WO2021209282A1 - Vibration damper

Info

Publication number: WO2021209282A1
Application number: PCT/EP2021/058896
Authority: WO
Inventors: Stefan Hummel; Sven WECKWERTH; Michael STUPP
Original assignee: Liebherr-Components Kirchdorf GmbH
Priority date: 2020-04-15
Filing date: 2021-04-06
Publication date: 2021-10-21
Also published as: DE102020110325A1; EP4136363A1

Abstract

The invention relates to an, in particular hydraulic, vibration damper with a cylinder which, in the interior, has a fluid chamber which is delimited axially by way of two cylinder covers and is filled with a fluid, a piston which is mounted such that it can be displaced within the fluid chamber of the cylinder and divides the fluid chamber into a first and a second chamber, and a piston rod which is connected to the piston, extends through at least one of the cylinder covers, and is mounted displaceably in the latter. The at least one cylinder cover, in which the piston rod is mounted, has a seal which seals the fluid chamber to the outside in a liquid-tight and/or gas-tight manner. According to the invention, a floating and contactless seal is additionally arranged between the fluid chamber and the seal.

Description

Vibration damper

The present invention relates to an especially hydraulic vibration damper according to the preamble of claim 1.

Vibration dampers, especially hydraulic vibration dampers that are filled with an oil, are used in a variety of applications to dampen mechanical vibrations by converting the vibration energy into heat. Vibration dampers of this type are used, for example, as shock absorbers on vehicles or to protect buildings from damaging vibrations such as those caused by people, machines, wind or earthquakes.

Typical vibration dampers known from the prior art are based on a cylinder which has a fluid chamber filled with fluid in which a piston is displaceably mounted. When an external force acts on the piston, the fluid in the cylinder is displaced by one or more damping elements that oppose the displaced fluid with a resistance. This creates a pressure difference that opposes the piston moving relative to the cylinder with a damping force. Usually, the damping elements, for example in the form of damping valves, are arranged in the piston so that the displaced fluid is forced from the pressure side through the piston to the low-pressure side. Alternatively, a fluid channel can be provided in which one or more damping elements are arranged, which connects the fluid chamber on both sides of the piston with one another.

Seals are used to seal off the fluid chamber of the cylinder from the environment. Here, in known hydraulic vibration dampers, elastomer seals are often used, which are designed as liquid-tight Wel lendichtung and are arranged on the guide of the piston rod in or on the cylinder housing.

When the vibration damper is stressed by the pressures that occur, these elastomer seals are exposed to high loads and therefore increased wear and tear, and due to the increased coefficients of friction, they lead to short downtimes and maintenance intervals. As part of maintenance measures, it is sometimes very costly and time-consuming to replace worn elastomer seals.

Against this background, the object of the present invention is to provide a vibration damper which, compared to known devices, requires less maintenance.

According to the invention, this object is achieved by a vibration damper, in particular a special hydraulic vibration damper, with the features of claim 1. Accordingly, the vibration damper according to the invention comprises a cylinder, which has a fluid chamber axially delimited by two cylinder covers and filled with a fluid inside, a piston displaceably mounted within the fluid chamber of the cylinder, which separates the fluid chamber into a first and a second chamber, and a with the piston connected to the piston rod, which extends through at least one of the cylinder covers and in this is slidably mounted. The at least one cylinder cover in which the piston rod is mounted has a seal which seals the fluid chamber from the outside, ie from the environment, in a liquid- and / or gas-tight manner. If the fluid is a liquid, for example oil, the seal is liquid-tight. If the fluid is a gas, it is gas-tight.

According to the invention, a floating and contactless seal is additionally arranged between the fluid chamber and the seal. The term "non-contact seal" is to be interpreted broadly and is to be regarded as a means (pressure reducing means or damping element) which is designed to generate a pressure difference between the fluid chamber and the side facing the seal, i.e. to reduce the pressure. In principle, for example, a pressure reducing valve can therefore also be viewed as a contactless seal in this sense. This enables a pressure reduction to the outside.

The additional integrated non-contact seal reduces the pressure applied to the (outer) seal, which leads to less friction and thus a longer service life of the seal. Due to the reduced wear of the seal, it has to be replaced less frequently, which considerably reduces the maintenance effort of the vibration damper according to the invention and extends the maintenance intervals required by changing the seal.

The advantages that result from the provision of an additional contactless or contactless seal exist regardless of the size and the purpose of the vibration damper according to the invention. Consequently, the vibration damper according to the invention can be, for example, a shock absorber for a vehicle, e.g. a car, excavator, mobile crane, etc., or a vibration damper to protect buildings from earthquakes, environmental influences or vibrations caused by people or machines.

Advantageous embodiments of the invention emerge from the subclaims and the following description. In one embodiment, a fluid channel is provided which connects the first and second chambers to one another. This can be, for example, a hose, a channel formed within the cylinder or a combination of such sections. The fluid channel can comprise one or more connections or connecting elements. The fluid channel preferably runs partially outside the cylinder, for example in the form of a hose which is connected to channels formed in the cylinder via connections. Alternatively, the fluid channel runs within the cylinder tube. As an alternative to this version, the damper also works without oil compensation of the fluid, taking into account the use. In this case, the two oil connections are closed.

Through the fluid channel, the fluid displaced from the pressure chamber (i.e. the chamber that is in front of the piston in the direction of movement of the piston and whose volume is thereby reduced) is displaced into the Niederdruckkam mer by a load on the Schwingungsdämf fers, ie when force is applied to the piston rod (ie the chamber on the other side of the piston, the volume of which increases due to the piston movement) rearranged or initiated.

In a further embodiment it is provided that the fluid channel comprises an inlet channel which is connected to the side facing away from the fluid chamber (ie low pressure side) of the contactless seal and is designed to allow fluid passing through the contactless seal into the other side of the piston to conduct lying chamber (low pressure chamber). The inlet channel is preferably formed in the cylinder, in particular within the cylinder cover, and is connected to a part of the fluid channel extending outside the cylinder.

The contactless seal is thus arranged between the fluid chamber and the inlet channel, the inlet channel being arranged between the outer seal and the contactless seal. This arrangement allows the Fluid forced from the pressure chamber by the contactless seal can escape via the fluid channel into the low-pressure chamber. The pressure at the outer seal is therefore only lower than that at the pressure chamber.

In a further embodiment it is provided that at least one non-return valve is provided in the fluid channel, which allows a flow of the fluid from the fluid channel into the fluid chamber, but vice versa blocks it. This ensures that fluid can only escape from the pressure chamber into the low-pressure chamber.

In a further embodiment it is provided that the fluid channel comprises an outlet channel which opens into the fluid chamber and in which the non-return valve is arranged. In particular, the outlet channel does not end on the low-pressure side of the contactless seal, but directly in the fluid chamber.

In a further embodiment it is provided that the inlet and / or outlet channels are at least partially formed in the cylinder cover. The channels are preferably connected to one another and connected to a part of the fluid channel extending outside the cylinder via a connection or a connecting element. It is also conceivable that some of the channels inside the cylinder jacket or the cylinder shell extends. The inlet and / or outlet channels are located in particular in the cylinder cover through which the piston rod runs, or in the case of a piston rod running through both cylinder covers in both cylinder covers. In particular, at least one inlet channel is provided for each pair of outer and non-contact seals so that the leakage fluid from each of the non-contact seals can flow off via the fluid channel into the respective other (low-pressure) chamber.

In a further embodiment it is provided that the piston rod extends on both sides of the piston through both cylinder covers and is mounted in these ver slidably. The piston rod advantageously points on both sides of the piston has the same diameter. In this embodiment, each cylinder cover has an (outer) seal which seals the fluid chamber from the outside in a liquid and / or gas-tight manner. Accordingly, two non-contact seals are provided, one of these non-contact seals being arranged between the fluid chamber and one of the (outer) seals.

As a result, the vibration damper according to the invention works in both directions, i.e. each of the chambers separated by the piston can function as a pressure and a low-pressure chamber, depending on the direction of force. A pressure reduced by one of the non-contact seals is applied to each of the seals.

In a further embodiment it is provided that the above-described fluid channel comprises an inlet channel and / or an outlet channel with an integrated check valve at each end.

In a further embodiment it is provided that the inlet and / or outlet channels in the cylinder covers and are preferably designed identically. Furthermore, the outer seals, the contactless seals and the inlet and outlet channels together with the check valves are designed to be identical (or mirrored). As a result, the vibration damper according to the invention works equally in both directions.

In a further embodiment it is provided that the cylinder and piston form a synchronous cylinder, i.e. both piston surfaces are the same size.

In a further embodiment it is provided that the (outer) seal is an elastomer seal and in particular a shaft seal contacting the piston rod.

In a further embodiment it is provided that the piston separates the first and second chambers from one another in a liquid-tight and / or gas-tight manner (depending on whether the fluid is a liquid or a gas). Ie there are no damping elements such as damping valves are provided in the piston or the piston rod. Instead, the damping effect is achieved by displacing the fluid from the pressure chamber via the contactless seal and finally via the fluid channel into the low-pressure chamber. This enables a simultaneous pressure reduction on the outer seal, which increases its service life.

In a further embodiment it is provided that the contactless device is a gap seal. Alternatively, another type of non-contact seal such as a labyrinth seal can be used, which also reduces the pressure applied to the outer seal. A valve, e.g. a pressure reducing valve, would also be conceivable here.

In a further embodiment it is provided that at least one of the cylinder covers on the side opposite the fluid chamber borders a further closed fluid chamber which is designed to interact with the piston rod in such a way that the volume of the further fluid chamber varies with the movement of the piston rod. The further fluid chamber is preferably filled with a compressible fluid.

The volume variation of the further fluid chamber as a function of the position of the piston rod can be realized in that the piston rod protrudes through the cylinder cover into the further fluid chamber or in that another piston or separating piston is provided at one end of the piston rod which faces away from the fluid chamber Page limits the further fluid chamber.

The further fluid chamber can be filled with a gas and serve as a gas cushion or gas damper for the vibration damper according to the invention. In particular, the vibration damper according to the invention can be a single-tube damper. In this case, the gas-filled further fluid chamber or gas chamber is used for volume and temperature compensation. The fluid that is in the fluid chamber is in particular oil. Alternatively, the fluid can be a gas.

Further features, details and advantages of the invention emerge from the exemplary embodiment explained below with reference to the single figure.

In the (single) FIG. 1, an exemplary embodiment of the vibration damper 10 according to the invention is shown in a cross-sectional view along the longitudinal axis of the vibration damper 10. This exemplary embodiment is a hydraulic vibration damper 10.

The hydraulic vibration damper 10 according to the invention comprises a cylinder 12, which has an oil-filled fluid chamber 18 in its interior, which is delimited at the axial ends of the cylinder 12 by two cylinder covers 14, 16 and radially by a cylinder shell 13. In the fluid chamber 18, a piston 20 is slidably mounted ver, which separates the fluid chamber 18 into two chambers 24, 26 liquid-tight. For this purpose, the piston 20 can have one or more seals.

The piston 20 is connected to a piston rod 22 which extends on both sides of the piston 20, has the same diameter on both sides (synchronous cylinder), extends through each of the two cylinder covers 14, 16 and is slidably mounted therein. On one side, the piston rod 22 protrudes from the cylinder 12 and has a fastening means 42 at the outer end, via which the vibration damper 10 can be connected to another component or structure of a vehicle, building or other device. The other end of the piston rod 22 likewise protrudes from the corresponding cylinder cover 16, but ends in a further fluid chamber 40 adjoining the cylinder cover 16.

In order to seal off the fluid chamber 18 in a liquid-tight manner from the environment, elastomer seals 28 are arranged in each cylinder cover 14, 16, which are designed as a shaft seal and are arranged around the piston rod 22. In order to reduce the pressure applied to the elastomer seals 28 when the vibration damper 10 is stressed, additional gap seals 30 are provided adjacent to the fluid chamber 18, ie between the fluid chamber 18 and the elastomer seals 28. The gap seals 30, as a non-contact shaft seal, allow oil to pass from the fluid chamber 18 to the side facing the elastomer seal 28 (low-pressure side).

It should be noted at this point that an embodiment is also possible in which the piston rod 22 is only supported in one of the cylinder covers 14, 16 and thus only one elastomer seal 28 and one gap seal 30 are provided.

The vibration damper 10 according to the invention further comprises a fluid channel 32 which connects the two chambers 24, 26 separated by the piston 20 to one another. When the vibration damper 10 is stressed, a force is exerted on the piston rod 22, so that the piston 20 moves in the direction of the further fluid chamber 40. This increases the pressure on the chamber 26, which is located between the piston 20 and the further fluid chamber 40. In contrast, the other chamber 24 has a lower pressure.

In the following, the term “pressure chamber” is used for that chamber 26, 24 in which, due to the force acting on the piston rod 22, there is a greater pressure than in the other chamber 24, 26, hereinafter referred to as “low pressure chamber” the vibration damper 10 is constructed (essentially) symmetrically and functions in both directions (in relation to the longitudinal axis of the piston rod 22), one or the other chamber 24, 26 can represent the “pressure chamber” depending on the direction of the force.

The fluid channel 32 comprises a part running outside of the cylinder 12, which in this exemplary embodiment is designed as a hose 33 and runs essentially parallel to the piston rod 22 between the two cylinder covers 14, 16. In each of the two cylinder covers 14, 16, an inlet channel 34 is formed, which extends from the gap between the piston rod 22 and the cylinder cover 14, 16 or from the The pressure side of each gap seal 30 runs to a connection means 39, which connects the inlet channels 34 to the hose 33. In the present case, the connection means 39 are hydraulic connections angled at 90 °. From the inlet channels 34 in each of the cylinder covers 14, 16 an outlet channel 36 also runs directly to the fluid chamber 18. In each of the outlet channels 36 there is a non-return valve 38, which allows oil to flow from the outlet channel 36 into the fluid chamber 18, but not the other way around. The inlet channels 34 are thus connected to the fluid chamber 18 via the gap seals 30 and the outlet channels 36 via the check valves 38.

The inlet and outlet channels 34, 36 as well as the check valves 38 and the connection means 39 are identical and mirrored to one another (on a plane running perpendicular to the longitudinal axis of the piston rod 22). The inlet channels 34 run vertically and the outlet channels 36 run parallel to the piston rod 22. Alternatively, it is also conceivable that instead of the hose 33 extending outside the cylinder 12, a channel formed in the cylinder shell 13 is provided. Furthermore, several fluid channels 32 can be connected in parallel, possibly each with a separate pair of inlet and outlet channels 34, 36 etc.

When the vibration damper 10 is stressed, i.e. when a force is exerted on the piston rod 22, oil is forced out of the pressure chamber 24, 26 through the gap seal 30 to the inlet channel 34. This leakage oil can escape via the fluid channel 32 into the low-pressure chamber 26, 24, specifically via the outlet channel 36 opening into the low-pressure chamber 26, 24.

The gap seals 30 thus fulfill a double function. On the one hand, they represent a resistance to the oil displaced by the force and thus ensure the damping effect of the vibration damper 10 according to the invention. On the other hand, they reduce the pressure on the side facing the elastomer seal 28 so that it is less stressed or less friction is generated and these are thus spared. This reduces the wear and tear on the Elastomer seals 28 considerably, which increases the service life until the next maintenance interval.

The further fluid chamber 40 can be filled with a gas and thereby act as a gas damper or cushion, which ensures volume and temperature compensation when the vibration damper 10 is stressed. In this case, the vibration damper 10 according to the invention is a hydraulic single-tube damper. One of the ends of the piston rod 22 protrudes into the further fluid chamber 40 and ensures that when the piston 20 moves, the volume of the further fluid chamber 40 also changes. The further fluid chamber 40 is closed. A further fastening means 42 is attached to its axial end spaced apart from the piston 20.

Instead of a hydraulic one, a pneumatic vibration damper 10 could in principle also be used, the fluid chamber 18 being filled with gas instead of oil and the above-mentioned “liquid-tight” seals being designed to be gas-tight. In this case, a gap seal 30 is used, which leads to a reduction in the gas pressure at the outer seals 28.

The gap seal 30 is only one possible example of a pressure reducing means which can be used in the vibration damper 10 according to the invention in order to reduce the pressure applied to the elastomer seal 28. Alternatively, a valve could also be provided which fulfills the same function, i.e. generates a pressure difference and opposes the displaced oil with a resistance in order to generate a damping effect. The pressure reducing means can thus also be viewed as a damping element.

List of reference symbols:

10 vibration dampers

12 cylinders

13 cylinder cover

14 cylinder cover Cylinder cover Fluid chamber Piston Piston rod First chamber Second chamber Seal Contactless seal Fluid channel Hose Inlet channel Outlet channel Check valve Connection means Further fluid chamber Fastening means

Claims

1. Vibration damper (10) comprising a cylinder (12) which has a fluid chamber (18) which is axially bounded inside by two cylinder covers (14, 16) and filled with a fluid, a fluid chamber (18) mounted displaceably within the fluid chamber of the cylinder (12) Piston (20) which separates the fluid chamber (18) into a first and a second chamber (24, 26), and a piston rod (22) connected to the piston, which extends through at least one of the cylinder covers (14, 16) and is mounted displaceably in this, where the at least one cylinder cover (14, 16) has a seal (28) which seals the fluid chamber (18) liquid-tight and / or gas-tight to the outside, characterized in that between the fluid chamber (18 ) and the seal (28) a floating and contactless seal (30) is also arranged, which realizes the pressure reduction to the outside.

2. Vibration damper (10) according to claim 1, characterized in that a fluid channel (32) is provided, which the first and second chambers (24, 26) connects to one another and partially extends outside the cylinder (12) or inside the cylinder tube (18) of the cylinder (12).

3. Vibration damper (10) according to claim 2 or 3, characterized in that the fluid channel (32) comprises an inlet channel (34) which is connected to the side of the contactless seal (30) facing away from the fluid chamber (18) and is formed to pass through the contactless seal (30) tre tend fluid into the chamber (24, 26) on the other side of the piston (20).

4. Vibration damper (10) according to claim 2 or 3, characterized in that at least one check valve (38) is provided in the fluid channel (32) which allows the fluid to flow from the fluid channel (32) into the fluid chamber (18).

5. Vibration damper (10) according to claim 4, characterized in that the fluid channel (32) comprises an outlet channel (36) which opens into the fluid chamber (18) and in which the check valve (38) is arranged.

6. Vibration damper (10) according to one of claims 3 to 4, characterized in that the inlet and / or outlet channels (34, 36) are at least partially formed in the cylinder cover (14, 16).

7. Vibration damper (10) according to one of the preceding claims, characterized in that the piston rod (22) extends on both sides of the piston (20) through both cylinder covers (14, 16) and is slidably mounted therein, each cylinder cover ( 14, 16) has a seal (28) which seals the fluid chamber (18) to the outside in a liquid-tight manner and with a floating and non-contact seal (30) for reducing pressure being additionally arranged between the fluid chamber (18) and the seals (28) .

8. Vibration damper (10) according to claim 7, characterized in that a fluid channel (32) is provided which connects the first and second chambers (24, 26) to one another and preferably partially extends outside the cylinder (12), each end of the fluid channel (32) comprises an inlet channel (34) according to claim 3 and / or an outlet channel (36) according to claim 5.

9. Vibration damper (10) according to one of the preceding claims, characterized in that the inlet and / or outlet channels (34, 36) in the cylinder covers (14, 16) and are preferably designed identically.

10. Vibration damper (10) according to one of the preceding claims, characterized in that the cylinder (12) and the piston (20) form a synchronous cylinder.

11. Vibration damper (10) according to one of the preceding claims, characterized in that the seal (28) is an elastomer seal.

12. Vibration damper (10) according to one of the preceding claims, characterized in that the piston (20) separates the first and second chambers (24, 26) from one another in a liquid-tight and / or gas-tight manner.

13. Vibration damper (10) according to one of the preceding claims, characterized in that the contactless seal (30) is a gap seal.

14. Vibration damper (10) according to one of the preceding claims, characterized in that at least one of the cylinder covers (16) on the side opposite the fluid chamber (18) is bordered by a further closed fluid chamber (40) which is formed with the piston rod (22) cooperate in such a way that the volume of the further fluid chamber (40) varies with the movement of the piston rod (22).

15. Vibration damper (10) according to claim 14, characterized in that the further fluid chamber (40) is filled with a compressible fluid.