Metal pneumatic spring bellows

Abstract

The invention relates to a telescopic pneumatic spring bellows (100) having an outer metal corrugated hose (111) and an inner metal corrugated hose (112), which are coupled by a connecting sleeve (120). In order to stabilise the movement, a guide element (161, 162) is provided which limits deviations of the movement of the inner and / or outer metal corrugated hose (111, 112) from the axial direction (X). The guide element can, for example, comprise spacer elements (161, 162) which are arranged between the connecting sleeve (120) on the one hand and the outer or inner metal corrugated hose on the other hand.

Description

[0001] Metallic air spring bellows

[0002] The invention relates to a telescopic air spring bellows with metal components.

[0003] US Patent No. 11,401,994 B2 discloses a telescopic air spring bellows that contains two metal bellows arranged telescopically within one another. The problem with such an arrangement is that the movement of the metal bellows can lead to instabilities, which can impair function and cause damage.

[0004] Furthermore, air spring bellows housed in an external housing are known from CN 1 178 171 A. Further embodiments of air spring bellows are described in DE 811 893 B, DE 10 2011 053 131 A1, DE 10 2010 037 162 B4, and DE 10 2008 001 297 A1.

[0005] Against this background, the object of the present invention was to provide a telescopic air spring bellows with metallic components which has improved operating behavior and increased long-term stability.

[0006] This object is achieved by an air spring bellows having the features of claim 1. Advantageous embodiments are contained in the subclaims.

[0007] The air spring bellows according to the invention contains (at least) the following components: At least one first metal corrugated hose, which due to its arrangement is hereinafter referred to as the "outer metal corrugated hose".

[0008] At least one second metal corrugated hose, which is arranged at least partially coaxially within the interior of the outer metal corrugated hose, such that it overlaps with the outer metal corrugated hose in an axial direction in an overlap region, forming a telescopic arrangement. Due to its arrangement, this second metal corrugated hose is hereinafter referred to as the "inner metal corrugated hose."

[0009] A connecting element, which is hereinafter referred to as "connecting sleeve" without restriction of generality, wherein the connecting sleeve extends in the aforementioned overlap area between the outer metal corrugated hose and the inner metal corrugated hose and connects the two metal bellows to each other.

[0010] The air spring bellows is characterized in that it has a guide element which limits deviations of the movement of the outer metal corrugated hose and / or the inner metal corrugated hose from the axial direction.

[0011] The deviations limited by the guide element can be lateral or torsional relative to the axial direction. Limiting the deviations can also include (almost) completely preventing such deviations. The axial direction corresponds to the spring direction of the air bellows and is usually determined by the design of the metal bellows (as their axis of symmetry or central axis). By limiting the movement deviation, the operating behavior of the air bellows can be improved and damage can be prevented.

[0012] For the purposes of this application, a "corrugated metal hose" (or "corrugated pipe") is generally understood to mean a metallic, tubular hose whose geometry differs from a simple cylindrical shape by the presence of at least one radially inwardly directed and circumferentially extending constriction. Such a constriction is generally not locally limited, but extends circumferentially around the hose axis. Both closed-ring and spiral-shaped constrictions can occur.

[0013] To function as an air spring bellows, the inner and outer corrugated metal tubes and the connecting sleeve are typically designed to be gas-tight and connected to each other. However, the invention also encompasses other applications of the device referred to as an "air spring bellows," which may not require a sealed interior, so in this case, the elements or their connections do not need to be gas-tight.

[0014] Furthermore, more than two metal bellows can be provided, which can be arranged serially one behind the other or in a telescopic arrangement parallel to each other. In particular, several pairs of outer metal bellows and inner metal bellows can be provided, each coupled to each other via an associated connecting sleeve. In this way, the ratio between the minimum and maximum length of the air spring bellows can be adjusted virtually arbitrarily.

[0015] The connecting sleeve is preferably connected to an axially upper end of the outer corrugated metal hose and an axially lower end of the inner corrugated metal hose (where the terms "upper" and "lower" are relative or are valid when the air bellows are aligned accordingly). Since the overlap area between the inner and outer corrugated metal hoses generally extends between these two ends, the connecting sleeve covers the entire overlap area in this case. At maximum possible compression of the air bellows, the inner and outer corrugated metal hoses lie completely adjacent to one another, i.e., the overlap area extends over the entire axial length of the air bellows.

[0016] The guide element can be designed and arranged in various ways and can consist of one or more parts. According to a preferred embodiment, the guide element is arranged at least partially (preferably completely) inside the outer corrugated metal hose and / or the inner corrugated metal hose. It is thus protected from harmful environmental influences such as contamination and corrosion, which benefits the service life of the air spring bellows.

[0017] According to a further preferred embodiment, the guide element includes a linear guide in the axial direction. In other words, lateral deviations from this direction are (completely or partially) limited. Additionally or alternatively, torsional movements (rotations) about the axial direction can also be limited by the linear guide. A linear guide without torsional limitation is achieved, for example, by two concentrically and telescopically interlocking tubes with circular cross-sections. If the tubes have a non-circular cross-section, the linear guide also limits torsional movements.

[0018] In a further embodiment, the guide element is coupled to the outside or inside of the outer corrugated metal hose and / or the inner corrugated metal hose. In this way, it can directly exert forces on this side and thus, for example, limit lateral movements. In particular, the guide element can be firmly coupled or connected to a specific position on the outside or inside so that it can move axially with this position. For example, the guide element can be a body that is positively connected to a corrugated metal hose, for example by engaging in a recess in this corrugated metal hose. Details of such a positive coupling can be found, for example, in patent DE 10 2010 037 162 B4.

[0019] Furthermore, the guide element can preferably slide along a sliding surface when the air spring bellows is compressed or stretched in the axial direction. The sliding surface can then act as a guide slot, enabling the desired movement limitation. Furthermore, the contact between the guide element and the guide slot can reduce friction, which has a positive influence on the damping behavior of the air spring.

[0020] Particularly when sliding contact exists between the guide element, the connecting sleeve, the outer metal corrugated hose, and / or the inner metal corrugated hose, the corresponding contact surfaces can advantageously have a friction-reducing and / or wear-reducing coating. This coating can preferably contain or consist of at least one of the following materials: stainless steel, steel, zinc, zinc phosphate, aluminum alloys, copper, titanium, tantalum, nickel-based alloys, graphite, aramids (e.g., Kevlar®), brass, bronze, (hexagonal) boron nitride, and / or molybdenum sulfide.

[0021] According to a further preferred embodiment, the guide element can be arranged between the connecting sleeve on the one hand and the outer metal corrugated hose and / or the inner metal corrugated hose on the other. In this case, the guide element allows force transmission between the connecting sleeve and at least one of the metal bellows without direct contact between these parts. In particular, lateral buckling movements of the metal corrugated hose can be reduced without causing wear-prone or dampening direct contact.

[0022] According to a further embodiment of the invention, the air spring bellows has a limiting element for limiting the maximum expansion of the air spring bellows. The limiting element can extend, in particular, inside the inner corrugated metal tube. It can be implemented, for example, as a rope, a chain, or the like, extending between the base and head of the air spring bellows. The limiting element can prevent overexpansion of the air spring bellows, which could potentially damage it.

[0023] In another embodiment of the invention, at least one end of the air spring bellows has a connecting plate. Such a connecting plate enables a (gas-)tight closure of the air spring bellows and provides a defined interface for coupling other components, for example, a motor vehicle or a machine to be suspended. The connecting plate preferably includes a locking pin for aligning the air spring bellows relative to its surroundings.

[0024] If the air bellows is to be used like an air spring, the interior of the metal bellows typically forms a closed volume filled with gas under excess pressure. To generate and / or regulate the gas pressure, the air bellows preferably has a connection through which a pressure medium (e.g., compressed air) can be supplied to the interior. The connection for the pressure medium can be located, for example, in one of the aforementioned connection plates.

[0025] The outer metal corrugated hose or the inner metal corrugated hose can, in particular, be a corrugated bellows, a wound bellows, or a diaphragm bellows. The term "bellows" generally refers to hoses with a corrugated outer contour, where the difference between the minimum inner diameter and the maximum outer diameter is relatively large (e.g., at least 5%, preferably at least 10% of the outer diameter). Corrugated bellows are typically manufactured from a tube by internal high-pressure forming in conjunction with an upsetting operation. Wound bellows and diaphragm bellows are welded, rotationally symmetrical, or spirally corrugated elements in the profile area, which have either pronounced corrugations perpendicular to the rotation axis or spiral corrugations. A wound bellows structure can preferably be hooked in a form-fitting manner, or can be overlapped or welded integrally.Such elements are described, for example, in DE 10 2008 001 297 A1 or DE 10 2011 053 131 A1, which are incorporated in their entirety into the present application by reference.

[0026] The air spring bellows and its components (metal bellows, connecting sleeve, etc.) can have a circular or non-circular (oval or polygonal) cross-section perpendicular to the axial direction. The invention is explained in more detail below using an exemplary embodiment with the aid of the attached figures. In the following:

[0027] Figure 1 shows a schematic cross-section through one half of a telescopic air spring bellows;

[0028] Figure 2 shows a section of Figure 1 with an alternative implementation of the limiting element as a linear guide.

[0029] Depending on the application, air spring systems typically use rolling or convoluted bellows. For example, in the automotive and commercial vehicle sector, rolling bellows (in conjunction with a rolling piston and a pressure plate) are preferred. The bellows are generally made of NR (natural rubber) / SBR (styrene butadiene rubber) rubber compounds with an additional reinforcement fabric.

[0030] Due to their design, rolling bellows allow for spring travel of at least + / -100 mm in commercial vehicles with a compact installation height. Spring travel of + / -50 mm is common in the automotive sector. Furthermore, even greater travel distances can be achieved when stationary, which is necessary, for example, to adapt a vehicle to varying loading sills.

[0031] A disadvantage of the current technology is that rubber ages due to influences such as sun, ozone, engine or exhaust heat, etc. The bellows wall then becomes hard and brittle, and there is a risk of cracking, especially in the area of ​​the roll fold.

[0032] It is therefore desirable to use metal bellows. Metal has a higher compressive strength than rubber, allowing for a higher burst pressure and a more compact component. Furthermore, metal is more recyclable than natural rubber.

[0033] Based on the aforementioned advantages, an air spring bellows is to be provided that, through the use of several compact, flexible metal hoses / metal bellows, achieves a spring travel identical to that of conventional rubber bellows in a comparable installation space. Preferably, at least two metal bellows, metal hoses, and / or diaphragm bellows should be coaxially interlocked to create a telescopic structure. This telescopic design allows for a compact installation height and sufficient spring travel.

[0034] In this regard, Figure 1 shows a section through an embodiment of an air spring bellows 100 according to the invention. The figure shows only one half of the device, which is essentially rotationally symmetrical about the "axial direction" X, which is vertical in the figure.

[0035] The air spring bellows 100 contains two telescopically nested metal bellows, namely an outer metal bellows 111 and an inner metal bellows 112 arranged coaxially within them. A suitable gas-tight, spirally wound metal bellows, which exhibits greater flexibility than conventional metal bellows, is known, for example, from DE 10 2008 001 297 A1. This flexibility enables a significant extension and compression of the component from the neutral position (typically approximately 20% in the compression and extension directions).

[0036] The upper end (in the drawing) of the outer metal bellows 111 is coupled to the lower end of the inner metal bellows 112 via a preferably rigid connecting sleeve 120. The connecting sleeve 120, with its Z-shaped cross-section, covers the overlap area between the inner and outer metal bellows with its cylindrical, axially extending shell. Furthermore, the connecting sleeve 120 has the task of transmitting the movement of the inner metal bellows 112 to the outer metal bellows 111.

[0037] The connecting sleeve 120 can be designed, for example, as a pressed part, drawn part, or turned part. It is preferably made of metal, but can also be made of plastic and / or have a wear- and friction-reducing coating.

[0038] The connecting sleeve 120 can have different shapes depending on the number of metal bellows. In the illustrated embodiment, it has a Z-shaped contour. The connecting sleeve 120 is connected to the respective metal bellows at its axial end regions. The connection can be positively connected (e.g., pressing, crimping), by a material connection (e.g., welding, soldering, gluing), or by a force connection. For use as an air spring, the connection must be gas-tight.

[0039] The total length LN of the air bellows 100 can vary in the axial direction X depending on its expansion or compression. The length LB of the overlap area as well as the variable lengths Li and L2 above and below it make up the total length LN of the air bellows 100. In the maximum compressed state of the air bellows, the lengths Li and L2 can be reduced to zero, with the two metal bellows 111 and 112 located parallel to each other completely around the connecting sleeve 120 or inside it. The overlap length LB should be selected as large as possible in order to achieve the lowest possible installation height. However, it may only be selected so large that the lengths Li and L2 resulting in the resting state are greater than the maximum spring deflection of the system.

[0040] As an alternative to the illustrated embodiment, more than two metal bellows (and connecting sleeves) can be coaxially inserted into one another (three, four, ..., n metal bellows). The more bellows are inserted into one another, the greater the spring travel and the outer diameter.

[0041] Furthermore, the bellows can be arranged next to each other (parallel), one behind the other or next to and behind each other.

[0042] If all metal bellows are of the same length, the bellows with the smallest diameter generally exhibits the greatest axial and lateral (perpendicular to the center axis X) stiffness. The diameter and bellows length can be matched so that two geometrically different bellows exhibit identical axial and lateral stiffness.

[0043] On their underside and top sides, the metal bellows 111 and 112 are each connected to a connecting plate 140 and 130, respectively. These connecting plates can in turn be coupled to the surrounding area (not shown in detail). The connection to the connecting plates can be positively, materially, or force-fitting, as well as gas- and liquid-tight. In a preferred embodiment, the connecting plates are connected by a soldering process.

[0044] In principle, the application range of the air bellows 100 is variable, although applications are also possible in which it (contrary to its name) does not function as an air spring. In the latter case, the interior of the air bellows does not need to be gas-tight to the environment. However, if the air bellows is to be used as an air spring, the metal bellows 111, 112, the connecting sleeve 120, the connecting plates 130, 140, and the connections between these parts must be gas-tight. The gas inside the assembly can then be compressed, thus generating the desired elastic spring force.

[0045] The metal bellows 111, 112 are preferably dimensioned and constructed so that they have equal spring constants c1 and c2. This has the advantage that stretching is distributed evenly between both bellows and the distances Li and L2 are equal.

[0046] The upper connection plate 130 may optionally have a locking pin 131 to facilitate alignment with the environment.

[0047] As shown, the lower connection plate 140 can have a compressed air supply line 141 for connecting an external compressed air source. This allows the space enclosed by the metal bellows to be subjected to a defined internal pressure Pi. This defined internal pressure causes the metal bellows to elongate.

[0048] The metal bellows 111, 112 have a rest length, which they assume in the unloaded state. If they are compressed relative to this rest length, lateral deflection movements (buckling) can occur. To limit or completely prevent this, the air spring bellows 100 is provided with at least one guide element, which limits or completely prevents lateral and / or torsional movements of the metal bellows. In the example shown in Figure 1, the guide element is realized by two spacer elements 161 and 162, which are arranged, on the one hand, between the inside of the outer metal bellows 111 and the connecting sleeve 120 and, on the other hand, between the connecting sleeve 120 and the outside of the inner metal bellows 112.These can, for example, be metallic knitted bands made of a relatively soft, friction-reducing non-ferrous metal such as cadmium, cobalt, copper, nickel, lead, tin, and zinc, which can slide along the connecting sleeve 120 with low friction and less frictional wear. Furthermore, corrosion- and heat-resistant stainless steel can also be used. The spacers prevent lateral buckling of the metal bellows 111, 112, thus ensuring clean guidance. The knitted band is preferably geometrically adapted to the contour of the bellows corrugation in order to be able to position it in a defined and form-fitting manner. It is compressible to a defined degree and thus only insignificantly influences the mobility of the metal bellows. Alternatively, the spacers can also be made "solid" from plastic or a non-ferrous metal (copper, brass, bronze, nickel, lead, tin, zinc, etc.).

[0049] To prevent overextension of the air bellows 100 in the axial direction X and thus plasticization of the bellows material, a centrally arranged limiting element 150 can be provided. In the illustrated embodiment, this is a flexible (wire) cable that extends between the lower connecting plate 140 and the upper connecting plate 130, and whose extended length specifies the maximum extension value of the air bellows. In the neutral position of the air bellows 100 shown in Figure 1, it has a length LN, while the metal bellows 111 and 112 overlap over a length LB (corresponding to the height of the connecting sleeve 120) and project beyond the overlap area by variable lengths L1 and L2, respectively.

[0050] An alternative embodiment of a limiting and guiding element 163 is shown in Figure 2. This shows a section similar to Figure 1, but the metal bellows are not shown. The guiding element 163 is designed as a linear guide unit and is formed, for example, by two slotted tubes 163a, 163b fixed to the upper and lower connecting plates 130, 140, respectively, and guided into one another, which are connected by a stop pin. This enables axial and torsional limitation of the movement and prevents excessive buckling.

[0051] During operation of the air spring bellows 100, the interior of the metal bellows is pressurized by supplying a resilient, compressible medium (gas, air) through the lower connecting plate 140, for example, to an operating pressure of approximately 7 bar. The internal pressure results in a force on the inner surfaces of the upper and lower connecting plates 130, 140. If the component is not externally constrained, this results in stretching and an increase in length LN. If the component is installed between two constraining frame structures, the generated force is absorbed by them, resulting in a counterforce in the frame structure. In this case, the component length does not change.

[0052] If the air spring bellows 100 is subjected to an external force during ferry operation due to the nature of the route, the metal bellows 111, 112 are compressed, resulting in a change in the internal volume. This change in volume results in a change—in this case, an increase—in the internal pressure.

[0053] In a spirally wound metal bellows, the pitch of the coils could lead to lateral buckling of the shell if the internal pressure increases. Such buckling is prevented by the parallel arrangement of the metal bellows in combination with the supporting spacer elements 161, 162.

[0054] In addition, the indirect frictional contact between the connecting sleeve 120 and the metal bellows can provide additional, secondary damping of the system and influence the frequency response of the metallic air spring.

[0055] Optionally, a throttle valve (not shown) can be provided between the two metal bellows to influence or inhibit the volume exchange between the chambers and thus achieve internal damping of the system.

[0056] The described air spring bellows can be used, for example, in commercial vehicles (in the LD, MD, and HD ranges) as well as in motor vehicles. The use of air springs is particularly advantageous in battery-electric vehicles (BEVs) due to the increased vehicle weight with a battery-electric drive.

[0057] Since the air bellows' main function is to perform an axial movement, industrial application is also possible, for example as a linear guide for machine components and / or as a suspension for machine components.

Claims

Patent claims 1. An air spring bellows (100) comprising an outer metal corrugated hose (111); an inner metal corrugated hose (112) which is arranged at least partially coaxially in the interior of the outer metal corrugated hose (112) such that it overlaps therewith in an overlap region (LB) in an axial direction (X) and forms a telescopic arrangement; a connecting sleeve (120) which extends in the overlap region (LB) between the inner metal corrugated hose (112) and the outer metal corrugated hose (111) and connects them to one another; characterized by a guide element (161, 162, 163) which limits deviations of the movement of the outer metal corrugated hose (111) and / or the inner metal corrugated hose (112) from the axial direction (X).

2. Air spring bellows (100) according to claim 1, characterized in that the guide element (161, 162, 163) is arranged in the interior of the outer metal corrugated hose (111) and / or the inner metal corrugated hose (112).

3. Air spring bellows (100) according to claim 1 or 2, characterized in that the guide element contains a linear guide (163) in the axial direction (X).

4. Air spring bellows (100) according to at least one of the preceding claims, characterized in that the guide element (161, 162) is coupled to the outside or the inside of the outer metal corrugated hose (111) or the inner metal corrugated hose (112).

5. Air spring bellows (100) according to at least one of the preceding claims, characterized in that the guide element (161, 162) can slide along a sliding surface.

6. Air spring bellows (100) according to at least one of the preceding claims, characterized in that the guide element (161, 162) is arranged between the connecting sleeve (120) and the outer metal corrugated hose (111) and / or the inner metal corrugated hose (112).

7. Air spring bellows (100) according to at least one of the preceding claims, characterized in that it has a limiting element (150) for limiting the maximum axial extension, which preferably extends in the interior of the inner metal corrugated hose (112).

8. Air spring bellows (100) according to at least one of the preceding claims, characterized in that a connecting plate (130, 140) is arranged at at least one axial end of the air spring bellows, which preferably has a locking bolt (131) for aligning the air spring bellows.

9. Air spring bellows (100) according to at least one of the preceding claims, characterized in that it has a connection (141) for the supply of a pressure medium.

10. Air spring bellows (100) according to at least one of the preceding claims, characterized in that the outer metal corrugated hose (111) and / or the inner metal corrugated hose (112) is a corrugated bellows, a wound bellows, or a diaphragm bellows.

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