GB2629293A

GB2629293A - Oil damper and spin test bench with same

Info

Publication number: GB2629293A
Application number: GB2410267.5A
Authority: GB
Inventors: Binsack Volker; Graefenstein Helge
Original assignee: Schenck RoTec GmbH
Current assignee: Schenck RoTec GmbH
Priority date: 2021-12-22
Filing date: 2022-12-19
Publication date: 2024-10-23
Also published as: DE102021134271B4; DE102021134271A1; GB202410267D0; WO2023116979A1

Abstract

An oil damper (1) is provided with an oil-filled inner oil chamber (2), designed as a hollow chamber, with a likewise oil-containing outer oil chamber (5) connected to the inner oil chamber (2) via at least one passage (3), with a piston rod (7) which protrudes through at least one of the passages (3) and the inner oil chamber (2), which is movable in its longitudinal direction and can be connected to an object (16) to be damped, and with a piston (11) fixed to the piston rod (7), which divides the inner oil chamber (2) into two inner oil chamber parts (12), with at least one passage (3) arranged therein. The inner oil chamber parts (12) are fluidically connected to one another via at least one oil passage means (13). A wave guide element (14) that is not sealed off with respect to the inner oil chamber (2) is arranged in the at least one passage (3) so that the oil can flow out of the inner oil chamber (2) into the outer oil chamber (5).

Description

OIL DAMPER AND SPIN TEST BENCH WITH SAME

The invention relates to a damping unit designed as an oil damper, which comprises an inner oil chamber and an outer oil chamber fluidically connected thereto, wherein the inner oil chamber is divided into two inner oil chamber parts by a piston rod connected to a piston. The invention also relates to a centrifugal test bench with such an oil damper.

For example, to measure loads acting on a rotating body, centrifugal test rigs can be used in which the body, such as a rotor, is operated in its operating speed range and above. In addition, the rotor can be subjected to cyclical speed changes or temperature fluctuations, for example. The rotor can be suspended from a thin, elastic shaft, e.g. via its shaft journal, and accelerated. The rotor then rotates around its axis of inertia instead of its geometric axis, so that the rotor moves virtually free of unbalanced forces. As the elastic natural frequencies of the shaft are usually passed through and large deflections can occur, dampers are often used to limit the shaft deflection so that the stability of the centrifugal shaft can be maintained.

Oil dampers are well-known damping units. These consist of an oil-filled cylinder tube that is closed at both ends by end pieces. A piston rod passes through one of the end pieces and is connected to a piston inside the cylinder tube, which slides in a sealed manner on the inner wall of the cylinder tube. A channel can lead through the piston, which acts as a throttling point to slow down the speed at which the piston is moved.

Oil dampers are known, for example, from DE 37 26 031 C2. Here, the damper has a housing with a cylindrical cavity that is open at one end and accommodates a cylindrical intermediate rotor. A further cylindrical rotor is arranged in the cylindrical intermediate rotor, which is leaded out of the open side of the housing. There is an annular space between the rotors, which is closed off at the closed end of the housing, whereby the hollow cylindrical rotor protrudes into the annular space and a shear gap and a straightening lock are formed in an annular gap between the intermediate rotor and the housing on both the inside and the outside.

DE 10 2004 014 458 Al discloses an oil damper installed in a front fork. The damper comprises an upper chamber and a lower chamber, in which oil is contained, and a fork-internal oil chamber, which is defined by the outer tube, the inner tube and a double-rod shock absorber and in which oil and air are contained. Further, the front fork comprises a check valve disposed in a lower portion of the double-rod shock absorber, the check valve allowing oil flow only in one direction from the fork-internal oil chamber to the lower chamber of the double-rod shock absorber, and a vent line having a small cross-section formed in an upper portion of the double-rod shock absorber, the vent line connecting the upper chamber of the double-rod shock absorber to the fork-internal oil chamber.

EP 2 562 440 B1 discloses a damper system with a magnetic coupling. The magnetic coupling comprises two magnets to exert radial opposing forces at radially opposite points around the rotor so that no resultant force is exerted on the rotor when the rotor is centered in the damper system.

DE 10 2005 055 558 Al describes an adjustable oil damper which has two coaxially interlocking tubes, both of which are closed at the ends by two closure members. The piston rod passes through one of the closure members, while the other closure member contains a throttle device, which can be used to regulate the flow resistance that the damper oil has to overcome when the piston is moved.

The problem with the known oil dampers is that the oil chambers must be sealed against leakage due to the strong alternating pressure caused by the movement of the piston. However, sufficient tightness can only be achieved -2 -with a flexible sealing element, which is connected to both the piston rod and the housing of the oil damper. In order to prevent the sealing element from bulging due to the high pressure, the sealing element would have to be sufficiently rigid. However, this leads to a high spring stiffness, which is not desirable for many oil dampers.

The invention is based on the task of providing an oil damper that has a low spring stiffness despite being sealed.

The problem is solved by the features of claim 1. Preferred embodiments are described in the dependent claims.

According to the invention, the problem is solved by providing an oil damper with an oil-filled inner oil chamber designed as a hollow chamber, an outer oil chamber connected to the inner oil chamber via at least one passage and also containing oil, with a piston rod projecting through the passage and the inner oil chamber, movable in its longitudinal direction and connectable to an object to be damped, and with a piston fixed to the piston rod, which divides the inner oil chamber into two inner oil chamber parts, a passage being arranged in at least one of the inner oil chamber parts, the inner oil chamber parts being fluidically connected to one another via at least one oil passage means, and with at least one shaft guide element arranged in the passage and not sealed off from the inner oil chamber, so that oil can flow from the inner oil chamber into the outer oil chamber.

In a preferred embodiment, an oil damper is provided with an oil-filled inner oil chamber designed as a hollow chamber, an outer oil chamber connected to the inner oil chamber via two passages and also containing oil, with a piston rod projecting through the passages and the inner oil chamber, movable in its longitudinal direction and connectable to an object to be damped, and with a piston fixed to the piston rod, which divides the inner oil chamber into two inner oil chamber parts, each with a passage arranged therein, the inner oil chamber -3 -parts being fluidically connected to one another via at least one oil passage means, and with shaft guide elements arranged in the passages and not sealed with respect to the inner oil chamber, so that oil can flow from the inner oil chamber into the outer oil chamber.

Furthermore, the invention relates to a spin test stand with a damper unit designed as an oil damper. The advantages and embodiments of the oil damper are to be applied analogously to the spin test bench. The oil damper can be permanently installed in the spin test bench and can be connected to the centrifugal shaft of the spin test bench. With the aid of the oil damper according to the invention, efficient damping of an excitation movement of the centrifugal shaft can be damped, thus ensuring the stability of the centrifugal shaft.

The design according to the invention tolerates leakage of the shaft guide element, i.e. the desired damping effect is achieved despite leakage and complicated and elaborately designed seals can be dispensed with. Especially as this allows the piston to move smoothly. The oil escaping from the inner oil chamber flows into the outer oil chamber via at least one shaft guide element, preferably via both shaft guide elements. As the outer oil chamber is fluidically connected to at least one passage, pressure equalization preferably takes place in this chamber. Consequently, an almost constant oil pressure is established in the outer oil chamber, which corresponds approximately to atmospheric pressure.

In one embodiment, the inner oil chamber has a cylindrical shape and is made of metal. The piston can preferably also have a cylindrical shape and in particular be designed as a disk.

The oil passage means, which fluidically connects the two inner oil chamber parts with each other, can advantageously be designed as a gap between the piston, in particular its outer surface and the inner wall of the inner oil chamber, -4 -in particular the inner surface of the hollow chamber wall. Depending on the design of the piston and its position in the inner oil chamber, the gap can extend only partially around the circumference of the piston or surround it corn pletely.

In a further embodiment, the oil passage means can be designed as a throttle or throttle valve, which is preferably integrated in the piston or between the piston and the inner surface of the hollow chamber wall. The throttle could also be arranged outside the cylinder, whereby two connections are provided in the inner oil chamber and the throttle is integrated in the connection between these two. In this respect, several throttles can also be provided through which the oil can move back and forth between the internal oil chambers. Furthermore, the oil passage means can be designed as an opening or several openings in the piston, through which pressure equalization between the inner oil chamber parts is possible.

The described shaft guide elements or the described shaft guide element are used analogously in the following to explain embodiments and function, so that the singular and plural are interchangeable and can be used for both embodiments. The shaft guide element is designed to be leak-proof and allows oil to escape from the inner oil chamber into the outer oil chamber. The shaft guide elements serve to guide the shaft, i.e. in particular the piston rod, and are arranged in particular in the passages between the inner oil chamber and the outer oil chamber. In one embodiment, however, it may also be preferred that only one shaft guide element is provided in a passage, provided that a single-acting piston or piston rod is preferred. One advantage of the leak-proof shaft guide elements is that sealing elements can be dispensed with and spring return forces can therefore be avoided. Oil can escape between the piston rod and the guide elements, particularly on both sides, and flow into the surrounding external oil chamber, which is advantageously also filled with oil. The shaft guide elements are preferably designed in such a way that the flow resistance they cause is higher than the flow resistance between the inner oil -5 -chamber parts in dynamic operation. This allows the pressure required for efficient damping to build up in the inner oil chamber.

The leaking shaft guide elements can be designed as linear bearings in particular. Linear ball bearings or plain bearings, which allow sufficient axial movement of the piston rod while tolerating leakage, are particularly preferred here.

The inner oil chamber is preferably perforated along its central axis by the two passages, for example in the form of bores, which advantageously each open into a chamber of the outer oil chamber. In this respect, it is preferable that the two chambers are arranged diametrically and are fluidically connected to each other via a line, for example a pipe connection.

The piston rod can be connected to a shaft, for example. One end of the piston rod protrudes from the end of the oil damper and can be connected to a shaft. In order to prevent oil from escaping from the outer oil chamber, the outer oil chamber has a sealed shaft feedthrough for the piston rod to pass through. This can be achieved, for example, by a flexible sealing element such as a sealing bellows.

In order to return oil from the outer oil chamber to the inner oil chamber, the outer oil chamber and the inner oil chamber can be connected to each other via a non-return valve so that oil can flow from the outer oil chamber into the inner oil chamber. The movement of the piston can generate a vacuum in the inner oil chamber, in particular in one of the two inner oil chamber parts, through which oil is sucked back into the inner oil chamber via the non-return valve.

The invention is explained in more detail below with reference to an embodiment of the invention, which is shown in the drawing. It shows -6 -Figure 1 a schematic representation of a design of an oil damper and Figure 2 a schematic representation of a spin test stand with a damping unit.

Figure 1 schematically illustrates a design of an oil damper, while Figure 2 schematically indicates a spin test stand with a damping unit. The oil damper 1 comprises an inner oil chamber 2, which can, for example, be formed by a cylindrical hollow chamber. The hollow chamber can, for example, be designed in several parts, whereby the parts can be screwed together and sealed accordingly. The inner oil chamber 2 has two diametrically arranged passages 3, which can for example be formed as holes in the wall of the inner oil chamber 2 and are preferably arranged along the central axis of the inner oil chamber 2. The passages 3 each open into a chamber 4 or a chamber of an outer oil chamber 5, which are located upstream or downstream of the inner oil chamber 2. The two chambers 4 of the outer oil chamber 5 are fluidically connected to each other via a line 6 or through a hollow bore through the hollow chamber wall.

The passages 3 and the inner oil chamber 2 are traversed by a piston rod 7. The piston rod 7 has a first end 8 extending into the oil damper 1 and a second end 9 projecting out of it. The first end 8 of the piston rod 7 is arranged at a distance from the inner wall of the outer oil chamber 5 and the second end 9 of the piston rod 7 can, for example, be connected to a centrifugal shaft of a centrifugal test stand. The outer wall 10 of the outer oil chamber 5, through which the second end 9 of the piston rod 7 protrudes, can be designed as a sealing element. However, it may also be advantageous to design only a part of the wall 10 as a sealing element or to provide a bore in the wall 10 with a shaft guide that is sealed with respect to the outer oil chamber.

The piston rod 7 is connected to a piston 11, which extends radially from the piston rod 7 into the inner oil chamber 2, whereby the piston rod 7 is designed to act on both sides, i.e. double-acting. The piston 11 can have a one-piece or -7 -multi-piece design and be attached to the piston rod 7, for example by means of fasteners. The piston 11 can have a cylindrical shape or be designed as a disk piston or plunger piston, whereby in this design the piston rod 7 is shorter and preferably does not open into a chamber 4 of the outer oil chamber 5.

The piston 11 divides the inner oil chamber 2 into two inner oil chamber parts 12, each with a passage 3 arranged therein, whereby the inner oil chamber parts 12 are fluidically connected to one another via at least one oil passage means 13. The size of the inner oil chamber parts 12 varies depending on the position of the piston 11 in the inner oil chamber 2. The oil passage means 13 can, for example, be provided as a gap between the circumferential surface of the piston 11 and the inner surface of the inner oil chamber 2, which is radially spaced from the latter. However, it is also possible for the oil passage means 13 to be designed as a throttle, not shown, via which a fluidic exchange can take place between the inner oil chamber parts 12. Furthermore, there may be holes or openings in the piston 11, which also enable fluid exchange between the inner oil chamber parts 12, but are not shown in the figures. In this embodiment, an 0-ring could preferably be present as a sealant in a groove on the circumferential surface of the piston 11.

Shaft guide elements 14 are present in the passages 3 between the inner oil chamber 2 and outer oil chamber 5. Depending on the design of the piston rod 7, one or two shaft guide elements 14 are provided in the passages 3. Depending on the design of the piston 11, only one passage 3 between inner oil chamber 2 and outer oil chamber 5 and therefore only one shaft guide element 14 may be provided. The shaft guide elements 14 can be designed as a linear guide, in particular as a linear bearing. The shaft guide elements 14, or shaft guides, allow a linear movement of the piston rod 7 along its longitudinal axis, which in turn causes a movement of the piston 11 in the inner oil chamber 2, which results in an increase or decrease in the volume of the inner oil chamber parts 12. In particular, the shaft guide elements 14 are designed to be leak-proof, i.e. sealing elements are deliberately omitted and leakage is -8 -tolerated so that oil can move from the inner oil chamber 2 into the outer oil chamber 5.

As can be clearly seen in Figure 2, the oil damper 1 can be provided as part of a spin test stand 15 and permanently installed in it. However, the oil damper 1 can also be used in any application if linear movements with a high frequency are to be damped. The oil damper 1, or more precisely the piston rod 7, can be connected to a flexible centrifugal shaft 16 of the centrifugal test stand 15, which in turn carries a rotor 17 to be tested. The rotor 17 is accelerated beyond its operating speed. By rotating the rotor 17, an excitation movement to be damped is exerted on the centrifugal shaft 16. The excitation movement is introduced into the damper 1 via the piston rod 7, which is illustrated schematically in Figure 2. However, it can also be advantageous if two oil dampers are used that are orthogonal to each other. The movement of the piston rod 7 causes the piston 11 connected to it to move and pump the oil present in the inner oil chamber 2 back and forth, for example through the gap between the two inner oil chamber parts 12, which is designed as an oil passage means 13. Due to the energy dissipated in the gap, a pressure difference forms between the inner oil chamber parts 12, which acts on the piston 11 as a desired damping force and dampens the initiated excitation movement.

In order to achieve low spring stiffness despite high damping force, the inner oil chamber 2 is connected to the outer oil chamber 5 via the leaking shaft guide elements 14. This allows oil to enter the outer oil chamber 5, which is also filled with oil, via the shaft guide elements 14. Since the outer oil chamber 5 is connected to both passages 3 via the shaft guide elements 14, pressure equalization takes place in the outer oil chamber 5 between the two outlet points, i.e. the passages 3. This results in an almost constant oil pressure in the outer oil chamber 5, which corresponds approximately to atmospheric pressure. In particular, it is intended that the flow resistance created by the shaft guide elements 14 is significantly higher than the flow resistance caused -9 -by the oil passage means, in particular the gap, so that pressure can build up in the inner oil chamber 2 and the desired damping behaviour of the oil damper is not impeded.

In order to return oil from the outer oil chamber 5 to the inner oil chamber 2, a valve, in particular a non-return valve 18, can be provided between the outer oil chamber 5 and the inner oil chamber 2. The non-return valve 18 can, for example, be spring-loaded or non-spring-loaded. When negative pressure is generated in the inner oil chamber part 12, which is connected to the outer oil chamber 5 via the non-return valve 18, by the movement of the piston 11, oil is moved from the outer oil chamber 5 into the inner oil chamber 2.

The preferred designs can be used to provide an oil damper that is suitable for high-frequency continuous vibrations > 200 Hz and for vibration amplitudes of > 2 mm, which has a spring stiffness of < 0.1 N/mm and damping values of > 100 Ns/m and is also oil-tight.

Claims

CLAIMSOil damper (1) with an oil-filled inner oil chamber (2) designed as a hollow chamber, an outer oil chamber (5) connected to the inner oil chamber (2) via at least one passage (3) and also containing oil, with a piston rod (7) projecting through the passage (3) and the inner oil chamber (2), movable in its longitudinal direction and connectable to an object (16) to be damped, and with a piston (11) fixed to the piston rod (7), which divides the inner oil chamber (2) into two inner oil chamber parts (12), a passage (3) being arranged in at least one of the inner oil chamber pads (12), the inner oil chamber parts (12) being fluidically connected to one another via at least one oil passage means (13), and having at least one shaft guide element (14) which is arranged in the passage (3) and is not sealed off from the inner oil chamber (2), so that oil can flow from the inner oil chamber (2) into the outer oil chamber (5).
Oil damper (1) according to claim 1 with an oil-filled inner oil chamber (2) designed as a hollow chamber, an outer oil chamber (5) connected to the inner oil chamber (2) via two passages (3) and also containing oil, with a piston rod (7) projecting through the passages (3) and the inner oil chamber (2), movable in its longitudinal direction and connectable to an object (16) to be damped, and with a piston (11) fixed to the piston rod (7), which divides the inner oil chamber (2) into two inner oil chamber parts (12), each with a passage (3) arranged therein, the inner oil chamber parts (12) being fluidically connected to one another via at least one oil passage means (13), and with shaft guide elements (14) arranged in the passages (3) and not sealed with respect to the inner oil chamber (2), so that oil can flow from the inner oil chamber (2) into the outer oil chamber (5).
Oil damper (1) according to claim 1 or 2, characterized in that the oil passage means (13) is designed as a gap between the piston (11) and the inner wall of the inner oil chamber (2).
Oil damper (1) according to claim 1 or 2, characterized in that the oil passage means (13) is designed as a throttle.
Oil damper (1) according to claim 1 or 2, characterized in that the piston (11) comprises oil passage means (13) designed as openings.
Oil damper (1) according to one of the preceding claims, characterized in that the shaft guide element (14) or the shaft guide elements (14) are designed in such a way that the flow resistance caused by them is higher than that caused by the oil passage means (13).
Oil damper (1) according to one of the preceding claims 5 or 6, characterized in that the shaft guide element (14) or the shaft guide elements (14) are linear bearings.
Oil damper (1) according to one of the preceding claims 2 to 7, characterized in that the outer oil chamber (5) comprises two fluidically connected and diametrically arranged chambers (4), into each of which one of the passages (3) opens.
Oil damper (1) according to one of the preceding claims, characterized in that the outer oil chamber (5) has a sealed shaft passage for the piston rod (7) to pass through.
10. Oil damper (1) according to one of the preceding claims, characterized in that the inner oil chamber (2) and the outer oil chamber (5) are connected via a non-return valve (18), so that oil can flow from the outer oil chamber (5) into the inner oil chamber (2).
11. A spin test bench (15) comprising an oil damper (1) according to one or more of the preceding claims.