DE102016207873B4 - Air suspension unit for a motor vehicle - Google Patents

Abstract

Air spring unit (1) for a motor vehicle, which has a hollow rolling piston (3) and a rolling bellows (2), the rolling bellows (2) being placed over the rolling piston (3) and under pressure to form a rolling fold (21) on the outside of the rolling piston (3), the rolling bellows (2) being clamped airtight between an air spring cover (7) and the rolling piston (3), and in the area of the air spring cover (7) a pneumatic connection (10) is provided, via which the interior compressed air can be variably supplied and removed from the rolling bellows (2), and that the rolling piston (3) is cylindrically formed by a cover plate (31) and an opposite base plate (32), which are connected to one another by a circumferential side wall (33), wherein at least one pneumatic connection (12) is provided within the base plate (32), via which compressed air can be variably supplied and removed from a compressed air supply to the interior of the rolling piston (3), the circumferential side wall (33) of the rolling piston (3) passing through the compressed air pressurization of the rolling piston (3) is elastically deformable, characterized in that the wall thickness of the side wall (33) increases in the axial direction from the cover plate (31) and from the base plate (32), where the wall thickness is greatest Tapers in the middle and the side wall (33) has the smallest wall thickness here, the inner diameter of the circumferential side wall (33) being increased in areas without any internal pressurization of the rolling piston (3) between the cover plate (31) and the base plate (32), while the Outside (34) of the side wall (33) is simultaneously cylindrical and its outer diameter is constant over its length.

Description

The invention relates to an air spring unit for a motor vehicle according to the preamble of claim 1. The air spring unit has a hollow rolling piston and a rolling bellows, the interior of the rolling bellows being variably fillable with compressed air and being rolled to form a rolling fold on the outside of the rolling piston.

Such an air spring unit can be operated as a continuously variable air spring unit. Such air suspension systems for motor vehicles offer a variety of functionalities to improve the driving characteristics of the vehicle. In such systems, for example, air springs are used that have a rolling bellows in which air is enclosed. This rolling bellows is connected in an airtight manner to a cover and a rolling piston. The rolling bellows is placed over the rolling piston and can roll on it under pressure. Such an air spring is supplied with compressed air by a compressor. Depending on the load of the motor vehicle, air is pumped in or out of the rolling bellows in order to keep the spring properties and thus also the level of the vehicle constant.

Such an air spring is made, for example, from DE 10 2013 203 396 A1 , DE 10 48 165 A , DE 11 27 729 A , US 2,926,011 A known. Furthermore, for example, the US 8,899,603 B2 a similar air spring, but with two bellows. The associated rolling piston has a first cylindrical section and a second section in which the diameter of the rolling piston is reduced in a funnel shape towards the bottom. However, the diameter of the cylindrical section is also locally reduced in its central region when viewed in the axial direction. A first main rolling bellows is attached in the usual manner in an airtight manner to the upper side of the rolling piston. A second, tubular bellows surrounds the rolling piston and is attached with its open hose ends in an airtight manner to the upper side of the rolling piston and to the lower end of the cylindrical section of the rolling piston. A first volume V1 is thus formed between the outer wall of the rolling piston and the inside of the tubular bellows. A volume V2 is defined by the first main rolling bellows. Compressed air can be supplied to both volumes V1 and V2 separately.

The main rolling bellows can roll along the outside of the second bellows on the rolling piston.

The US 9,193,239 B2 However, discloses an air spring device for a motor vehicle with an air spring of the type described, the lower region of a cylindrical rolling piston being accommodated in an axially movable manner in a likewise cylindrical bearing pot. The rolling piston is supported within this bearing pot by a helical spring in an axially movable manner relative to the bottom of the bearing pot. In addition, the rolling piston is held on the inner wall of the bearing pot by a radial bearing.

From the DE 10 2011 003 151 A1 an air spring with rolling bellows is known, the rolling piston of which is formed from a structure with several sections of different shapes. An upper section is cylindrical with a wall with a constant wall thickness, while the lower section is formed by a double-walled hollow body whose inner and outer diameter varies in the axial direction. The US 2015/0210138 A1 describes an air spring with a similarly designed rolling piston.

The WO 2013/007527 A1 describes an air spring with a rolling piston, which also has an upper cylindrical section, but whose diameter tapers towards the bottom. From the DE 10 2011 086 415 A1 an air spring with a rolling piston is known, the cross section of which has different diameters, wall thicknesses and geometries in the axial direction. The US 8,967,648 B2 discloses continuous force control for dual air spring configuration.

However, these types of air suspension units have a large number of components that have to be assembled, so that the air springs are often complex to manufacture. Furthermore, they are relatively heavy and the geometries of some rolling pistons are very complex.

In view of the state of the art shown, the area of air suspension units for motor vehicles still offers room for improvement.

The invention is based on the object of providing a relatively light air spring unit that has as few components as possible and is easy to manufacture.

According to the invention the object is achieved by an air suspension unit for a motor vehicle with the features of claim 1.

It should be noted that the features and measures listed individually in the following description can be combined with one another in any technically sensible manner and show further refinements of the invention. The description characterizes and additionally specifies the invention, particularly in connection with the figures.

The air spring unit according to the invention has a hollow rolling piston and a rolling bellows, the interior of the rolling bellows being variably fillable with compressed air and being able to be rolled to form a rolling fold on the outside of the rolling piston. In this way, air can be supplied and removed from the rolling bellows in a continuously variable manner, for example in order to adapt the spring properties of the air spring depending on the load of the motor vehicle. For this purpose, the air spring is mounted between the body and a wheel suspension element.

According to the invention, the interior of the rolling piston can also be variably filled with compressed air, with at least one side wall of the rolling piston being elastically deformable when this compressed air is applied. The elastic deformation takes place in a direction transverse to the longitudinal axis of the air spring unit.

This means that air can be supplied and removed in a continuously variable manner not only to the rolling bellows, but also to the rolling piston, which can also be used to adapt the spring properties of the air suspension unit. Compared to other continuously variable air spring units, the air spring unit according to the invention has a less complex structure. In addition to the two elements of the rolling bellows and rolling piston, an additional air spring cover can be sufficient to close the rolling bellows in the area of the connection to the body. The other end of the tubular rolling bellows is closed by the rolling piston. This would only require three elements that are easy to assemble. In one embodiment of the invention, the rolling bellows is then clamped in an airtight manner between an air spring cover and the rolling piston.

The geometry of the rolling piston can be designed to be simple in order to be able to realize an elastic deformation of at least one side wall when pressure is applied from the inside. The simple design of the air suspension unit enables low manufacturing costs, low unit costs and low material costs. Furthermore, the air spring unit according to the invention is significantly lighter than known air spring units.

In order to support elastic deformation of a side wall of the rolling piston, the wall thickness of this elastically deformable side wall is reduced in areas according to the invention. The rolling piston is cylindrical in shape by a cover plate and an opposite base plate, which are connected to one another by a circumferential side wall. According to the invention, the wall thickness of the side wall is then reduced at least in some areas between the areas near the cover plate and the base plate, i.e. in a central area. The wall thickness in the areas near the cover plate and the base plate is therefore greater than in a section between these areas. In this way, the side wall can bulge outwards when pressure is applied, with the rolling piston taking on the shape of a barrel at higher pressures. The deformation of the side wall depends on the pressure level inside the rolling piston and the variation in wall thickness of the side wall.

For example, the side wall can have the smallest wall thickness x approximately in the middle between the cover plate and the bottom plate of the rolling piston. However, the reduced wall thickness can also be provided slightly outside the center. Amounts for the reduced wall thickness can in particular be between 2 mm and 10 mm, while the maximum wall thickness in other sections of the side wall can be between 5 mm and 20 mm.

The partial reduction in the wall thickness of the side wall can be achieved by reducing the outer diameter and simultaneously increasing the inner diameter of the rolling piston in a common section. In a preferred embodiment of the invention, however, only the inner diameter of the rolling piston is increased in one section. In this embodiment, the circumferential side wall then has a constant outside diameter without any internal pressurization of the rolling piston between the cover plate and the base plate and is therefore cylindrical. The inner diameter between the areas near the cover plate and the base plate, however, is increased in some areas, which reduces the wall thickness in this area.

Preferably, the area-wise reduction in wall thickness is continuous. It is therefore not a local circumferential groove, but rather the inner surface of the side wall is curved outwards overall. Various suitable curvature curves can be used. In one embodiment of the invention, the inner surface of the side wall, starting from the cover plate and the base plate, initially runs parallel to the outer surface of the side wall before the outward curvature begins.

In order to be able to supply and remove air to the interior of the rolling piston, at least one pneumatic connection can be provided within the base plate of the rolling piston.

The rolling piston can be made of a single material or different materials. For example, the side wall can be made of a different material than the cover plate and the base plate. However, only a single material with different thicknesses can be used. In one embodiment of the invention, at least the side wall of the rolling piston can be made of a plastic. This plastic is ideally elastically deformable. For example, polyamide can be used for this.

• 1 eine Seitenansicht einer Ausführungsform einer erfindungsgemäßen Luftfedereinheit,
• 2 einen schematischen Querschnitt durch eine Luftfedereinheit gemäß der 1 mit geringem Druck im Abrollkolben, und
• 3 einen schematischen Querschnitt durch eine Luftfedereinheit gemäß der 1 mit höherem Druck im Abrollkolben.

Further advantageous embodiments of the invention are disclosed in the subclaims and the following description of the figures. Show it:

• 1 a side view of an embodiment of an air spring unit according to the invention,
• 2 a schematic cross section through an air spring unit according to 1 with low pressure in the rolling piston, and
• 3 a schematic cross section through an air spring unit according to 1 with higher pressure in the rolling piston.

In the different figures, the same parts are always provided with the same reference numbers, which is why they are usually only described once.

The schematic side view according to the 1 shows an air spring unit 1 with a tubular rolling bellows 2 and a rolling piston 3. This air spring unit 1 is arranged between the body and an element of a wheel suspension of a motor vehicle. The upper end of the air spring unit 1 is, for example, firmly connected to the body or a subframe 4. The lower end is then firmly connected to an element 5 of the associated wheel suspension. This element 5 can be, for example, a wheel carrier or a wishbone.

The upper end of the rolling bellows 2 is attached to an upper air spring cover 7. The air spring cover 7 is the schematic cross section 2 refer to. This is typically done by means of a crimp ring 6. The upper hose end of the rolling bellows 2 is then clamped between the crimp ring 6 and the air spring cover 7, the crimp ring 6, for example, as in the embodiment of 2 can be outside. The air spring cover 7 is in turn connected to the body or a subframe. For the purposes of the invention, crimping is to be understood as a joining process in which two components are connected to one another by plastic deformation, for example by crimping, squeezing, crimping or folding. A crimp connection is described as an example. It is of course within the scope of the invention to choose other suitable types of connection, for example a clamp connection or something else.

The lower end of the rolling bellows 2 is attached to the rolling piston 3. This is done via another crimp ring 8. This crimp ring 8 can be used as in the embodiment of 2 lie inside the rolling bellows 2 and clamp the lower hose end of the rolling bellows 2 between the upper end of the rolling piston 3 and the crimping ring 8. The rolling bellows 2 is first turned inside out. A rolling fold 21 is thus formed in the flexible rolling bellows 2, which can roll on the outside of the rolling piston 3. In this regard, too, a crimp connection is described only as an example. It is of course within the scope of the invention to choose other suitable types of connection, for example a clamp connection or something else.

The pressure within the rolling bellows 2 is adjusted by supplying and removing air to the delimited area of the bellows volume 9. A pneumatic connection 10 is used for this. This is preferably located in the area of the upper air spring cover 7. The compressed air can be passed through the air spring cover 7 and also through a section of the body or the subframe 4. The compressed air supply connected to the connection 10, for example with a compressor, is not shown in the figures, but can be carried out by the person skilled in the art in various suitable ways.

The rolling piston 3 is a hollow element. This is, for example, formed from a plastic material and has an upper cover plate 31, a lower base plate 32 and a substantially cylindrical side wall. Air can also be supplied and removed from the delimited space in the form of the piston volume. This is done via a pneumatic connection 12 for the rolling piston. This connection 12 is located in the area of the lower base plate 32. The compressed air can be passed through the base plate 32 and also through a section of the wheel carrier or handlebar 5. The compressed air supply connected to the connection 12 is also not shown in the figures, but can be carried out in various suitable ways by the person skilled in the art.

The cover plate 31 and the bottom plate 32 of the rolling piston 3 are round and preferably have a constant wall thickness. The cylindrical side wall 33 of the rolling piston 3, however, has a variable wall thickness. At least this side wall is made of plastic. The areas near the cover plate 31 or the The base plate 32 is designed to be thicker than an area further away from the cover plate 31 or the base plate 32. For example, the side wall 33 can be tapered approximately in the middle of the rolling piston 3, viewed in the axial Z direction. However, the taper can also be provided closer to the cover plate 31 or the base plate 32. The thickness x in this area can be between 2 mm and 10 mm, while the larger thickness X in the area of the cover plate 31 and the base plate 32 can be, for example, between 5 mm and 20 mm.

The side wall 33 of the rolling piston 3 can assume different states or shapes depending on the pressurization, which are described below with the reference numbers 33a and 33b. In 2 the rolling piston 3 is shown in a first pressure state in which there is low pressure in the inner piston volume 11a. The side wall 33 of the rolling piston 3 is undeformed in this state 33a, and the outside 34 of the side wall 33 is cylindrical. The outer diameter of the rolling piston 3 is therefore essentially constant over its length. In 2 This state of the outside 34 is designated by the reference number 34a.

3 shows the rolling piston 3, however, in a state in which relatively high pressure is present in the now enlarged piston volume 11b. The outside 34 of the side wall 33 of the rolling piston 3 is no longer cylindrical in this state 33b, but is curved outwards due to the internal pressure. In 3 This state of the outside 34 is designated by the reference number 34b. The outer diameter of the rolling piston 3 is therefore no longer constant over its length. In this state, the rolling piston 3 has a quasi barrel shape, ie the side wall 33 bulges outwards. The side wall 33 is elastically curved outwards in a direction that runs transversely to the longitudinal axis A of the air spring unit, ie in the X direction. The cover plate 31 and the base plate 32 are preferably designed so that they do not deform.

The change in shape of the outside 34, i.e. 34a/34b of the cylindrical side wall 33, i.e. 33a/33b, is a function of the pressure of the air in the volume 11a/11b within the rolling piston 3 and the change in wall thickness of the cylindrical side wall 33, i.e. 33a/ 33b. The shape change is therefore continuous between two extreme states.

List of reference symbols:

1

Air suspension unit

2

Rolling bellows

21

Roll fold

3

rolling piston

4

Body, subframe

5

Wheel carrier, handlebars

6

crimp ring

7

Air spring cover

8th

crimp ring

9

Bellows volume

10

Pneumatic connection for rolling bellows

11a

Piston volume in the first pressure state

11b

Piston volume in the second pressure state

12

Pneumatic connection for rolling piston

31

Cover plate

32

base plate

33

Side wall

34

Outside

33a

Sidewall in the first printing state

34a

Outside of the rolling piston in the first pressure state

33b

Sidewall in the second printing state

34b

Outside of the rolling piston in the second pressure state

A

Longitudinal axis of the air suspension unit

Claims (4)

Air spring unit (1) for a motor vehicle, which has a hollow rolling piston (3) and a rolling bellows (2), the rolling bellows (2) being placed over the rolling piston (3) and under pressure to form a rolling fold (21) on the outside of the rolling piston (3), the rolling bellows (2) being clamped airtight between an air spring cover (7) and the rolling piston (3), and in the area of the air spring cover (7) a pneumatic connection (10) is provided, via which the interior compressed air can be variably supplied and removed from the rolling bellows (2), and that the rolling piston (3) is cylindrically formed by a cover plate (31) and an opposite base plate (32), which are connected to one another by a circumferential side wall (33), wherein at least one pneumatic connection (12) is provided within the base plate (32), via which compressed air can be variably supplied and removed from a compressed air supply to the interior of the rolling piston (3), the circumferential side wall (33) of the rolling piston (3) is elastically deformable by the application of compressed air to the rolling piston (3), characterized in that the wall thickness of the side wall (33) increases in the axial direction from the cover plate (31) and from the base plate (32), where the wall thickness is greatest tapers in the middle and the side wall (33) has the smallest wall thickness here, the inner diameter of the circumferential side wall (33) being increased in areas without any internal pressurization of the rolling piston (3) between the cover plate (31) and the base plate (32), while the outside (34) of the side wall (33) is simultaneously cylindrical and its outer diameter is constant over its length. Air suspension unit Claim 1 , characterized in that the reduced wall thickness x is between 2 mm and 10 mm. Air spring unit according to one of the preceding claims, characterized in that the regional reduction in wall thickness is designed to be continuous. Air spring unit according to one of the preceding claims, characterized in that at least the side wall (33) of the rolling piston (3) is made of a plastic.

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