DE102019209491A1 - Air spring with a plastic outer guide - Google Patents

Abstract

Air spring (1) for a motor vehicle, the air spring (1) comprising an elastomeric bellows (4), which is clamped airtight between two connection parts (2; 3) of the air spring (1) and forms at least one roller fold (10) on one of the connecting parts (3) rolls, the rolling bellows (4) being at least partially surrounded by a sleeve-shaped outer guide (7) made of a plastic, the longitudinal guide (7) of the outer guide (7) having a varying wall thickness (d).

Description

The invention relates to an air spring with a plastic outer guide for a motor vehicle according to the preamble of claim 1.

An air spring essentially consists of an air spring cover, a rolling piston and a bellows clamped between them in an airtight manner, thereby limiting a working space under air pressure. The bellows can be enclosed by a sleeve-shaped outer guide and rolls down on the concentric rolling piston during compression, forming a rolling fold. The air spring is connected on the one hand via the air spring cover to the motor vehicle body and on the other hand via the rolling piston to the wheel carrier in order to achieve its spring properties.

External guides are used in particular for thin-walled rolling bellows and to limit their expansion. As a rule, state-of-the-art external guides are made of aluminum. Associated manufacturing processes such as deep drawing, extrusion, etc. have very limited options for adapting the wall thickness to the actual loads, as a result of which the geometric freedom of previous external guides is severely limited.

An outer guide made of plastic with fiber reinforcement is, for example, from the DE 10119363 A1 known.

As a rule, external guides (both aluminum and plastic external guides) are always dimensioned according to the maximum load or worst case, and at best the design reliability is checked for individual other load cases, with a lower load in some areas compared to the load case with the highest load.

It is therefore an object of the invention to provide an air spring with a plastic outer guide, which is characterized by a reduced use of material compared to the prior art and thereby completely fulfills the required strength.

The object on which the invention is based is achieved with the features of the independent patent claim.

According to the invention, an air spring for a motor vehicle is provided, the air spring comprising an elastomeric bellows, which is clamped airtight between two connection parts of the air spring and rolls to form at least one roll fold on one of the connection parts, the roll bellows being at least partially made of a plastic and sleeve-shaped outer guide is surrounded, the outer guide having a varying wall thickness in its longitudinal extent.

The invention is based on the fundamental consideration that the outer guidance of an air spring can be subdivided into four different load zones, since it is exposed to different internal pressures due to its task (supporting corset for the bellows). First of all, the outer guide is fixed to the bellows by means of an inner clamping ring. A high radial pressure acts on the outer guide in this fastening area. Furthermore, the outer guide is also used to attach a protective bellows, which protects the roller fold from dirt. As a rule, this area of the external guidance is not subjected to the internal pressure of the work area.

It has therefore been recognized in an inventive manner that a saving in material and weight of the outer guide can be achieved by specifically varying the wall thickness by adapting the wall thickness of the outer guide to the respective loading situations of the individual loading zones.

Thermoplastic or thermosetting plastic can be used as the plastic material for the outer guide.

According to a preferred embodiment, the outer guide comprises a first end region and a second end region, the wall thickness in the second end region being smaller than the wall thickness in the first end region.

The first end region is, for example, the end of the outer guide facing the first connection part, this region being essentially defined by the fastening of the outer guide to the rolling bellows. The second end region is accordingly the end of the outer guide facing the second connection part. This area is essentially characterized by the fact that the rolling bellows or its rolling fold is not in any deflection position of the regular dynamic driving operation in this area of the outer guide.

This therefore leads to an outer guide which is thick-walled in the area of its attachment to the rolling bellows and which ends in the exposed area as thin-walled as possible.

The second end area is preferably provided for the connection of a protective bellows. The protective bellows or bellows attached to the lower end of the outer guide protects the roller fold from dirt.

According to a further preferred embodiment, the outer guide has an essentially cylindrical inner wall. The outer guide, which varies in its wall thickness, is characterized in particular by a largely cylindrical inner wall. It represents a contact surface that runs as flat as possible for the rolling bellows and especially for its rolling fold.

According to a further preferred embodiment, the outer guide has an essentially conical outer wall. The freedom of design is greatest on the outer wall of the outer guide, so that the easiest way to achieve a material reduction is through the conical shape.

According to a further preferred embodiment, at least one means for increasing the strength is provided on the outer guide. In order to ensure sufficient strength in the tapered areas of the outer guide, means or circumferential elevations (also called ribs) are provided which increase the material strength in this area.

The means for increasing the strength is preferably formed from the plastic material of the outer guide. It is advisable to shape the means or means for increasing strength in the course of spraying the outer guide.

The means for increasing the strength is preferably provided on the outer wall of the outer guide. In addition, the means for increasing the strength is preferably arranged in a central region of the outer guide. The targeted placement of the agent or agents for increasing the strength significantly increases the material strength in the middle area, the total weight of the outer guide being increased only minimally. The central area of the exterior guide is characterized by the fact that the roll fold rolls up and down in this area of the exterior guide during regular dynamic driving.

According to a further preferred embodiment, the outer guide is fixed to the rolling bellows by a fastening ring. The fastening ring can, for example in the form of an inner clamping ring, clamp the outer guide on the inside of the rolling bellows.

If the air spring according to the invention is combined with an integrated shock absorber, it is an air spring strut in which the outer guide with varying wall thickness is also used.

The air spring is used in a chassis, preferably in an air spring system, for a motor vehicle.

Further preferred embodiments of the invention result from the following description of exemplary embodiments with reference to the figures.

• 1 eine Luftfeder gemäß dem Stand der Technik, und
• 2 im Ausschnitt ein erstes Ausführungsbeispiel einer Luftfeder mit einer Außenführung, und
• 3 im Ausschnitt ein zweites Ausführungsbeispiel einer Luftfeder mit einer Außenführung.

Show it

• 1 an air spring according to the prior art, and
• 2nd in the cutout a first embodiment of an air spring with an outer guide, and
• 3rd in the detail a second embodiment of an air spring with an outer guide.

The 1 shows a highly schematic air spring 1 with their essential components. An air spring cover serves as the first connection part 2nd A rolling piston is used to connect to the vehicle body and as a second connection part 3rd for connection to a wheel carrier. This regular installation position of an air spring determines the orientation "up / down".

Between air spring cover 2nd and rolling piston 3rd is an elastomeric bellows 4th clamped airtight, creating a volume-elastic work space filled with compressed air 5 is limited. Tubular bellows 4th is via respective clamping rings 6 on the connecting parts 2nd , 3rd attached.

Rollbalg is also 4th from a sleeve-shaped outer guide 7 enclosed, which is used as a support corset, especially in thin-walled rolling bellows, to the high internal pressure in the work area 5 counteract. External guidance 7 extends parallel to the longitudinal axis L of the air spring 4th . Thin-walled rolling bellows are usually thread-reinforced, these threads being aligned axially or in a cross-over position.

Rolling bellows rolls in dynamic driving mode 4th forming a roller fold 10th on the outer wall of the rolling piston 3rd back and forth. The roll-off piston moves when it is compressed 3rd towards the air spring cover 2nd so that bellows 4th the rolling piston 3rd significantly covered. When rebounding, when there is an air spring cover 2nd from the rolling piston 3rd moving away, the bellows loosens 4th from the rolling piston 3rd so that the outer wall is mostly exposed.

At the same time, the bellows rolls 4th with its roll fold 10th on the inside of the outside guide 7 along. In the normal level position, the lower end area of the outer guide lies 7 usually partially free. When the spring deflection is complete, the bellows is released 4th always more of the inner wall of the outer guide 7 so that a larger area of the outer guide 7 without bellow contact. When the transition to the fully sprung state, roller folds roll 10th on outside guidance 7 along so that outside guidance 7 again mostly from the adjacent bellows 4th is covered and the lower end area is exposed.

The 2nd shows a section of a first exemplary air spring, the outer guide 7 is divided into four areas. Basically, the burden of external guidance 7 divide into four local areas.

The exit of the bellows 4th represents a first area B1 This describes the transition area at which rolling bellows 4th the outside guidance 7 leaves and forms a cardanic fold.

As a second area B2 becomes the upper end of the outer guide 7 viewed towards the air spring cover, which is also the fastening area of the outer guide 7 on the bellows 4th represents.

The attachment of external guidance 7 on the bellows 4th done by a clamping ring 8th , which is on the inside of the bellows 4th is positioned and against which external guidance 7 is pressed so that it is on the bellows 4th is fixed in a rigid position. Because of this fixation, the rolling fold does not roll in any deflection state 10th in the second area B2 .

Below the second area B2 there is a third area B3 in front. This is characterized in that the peel point of the roller fold 10th in normal level within this range B3 lies. Area B3 is defined by the highest release point of the roll fold 10th in the sprung state and through the lowest detachment point of the roller fold 10th in the spring-out state.

In conclusion, as a fourth area B4 the lower end of the outer guide 7 understood which is facing the rolling piston. Area B4 is considered to be unloaded due to the fold 10th in no deflection state. Preferably is range B4 intended for the connection of a bellows.

It has been recognized that outside leadership 7 is exposed to different pressures over its entire length and thus has to meet different strength requirements in some areas. So occurs directly at the outlet of the roller bellows 4th from outside guidance 7 in the first area B1 the highest burden. At normal level, the loads are in the second and third range B2 , B3 due to the internal pressure in the work area 5 almost the same. The burden on the fourth area B4 is negligible because it is from the bellows 4th is not overrun.

Based on these findings, an exemplary wall thickness reduction is carried out by external guidance 7 proposed over their axial length. The longitudinal axis of the air spring 1 is marked with L.

Because in the second area B2 the highest load occurs, the required wall thickness d set to 100% in this area. A wall thickness d of 100% meets the necessary strength requirements of the external guidance 7 around the inside pressure of the work space 5 to withstand the air spring. Below can be the wall thickness d in the third area B3 Start at 67% and continue to thin out to 35%. The wall thickness d in the fourth area B4 is subject to the minimum producible thicknesses of the selected spraying process.

Consequently, the length of the outer guide varies 7 their wall thickness d and can lead to a material saving of 13% compared to purely cylindrical outer guides. Like it 2nd can be seen, the external guidance tapers 7 downwards, so that a material and weight saving is achieved.

With the 3rd a second exemplary air spring is shown, the outer guide 7 with additional means to increase strength 9 is provided.

In this modified form, exterior guidance 7 on the outer wall a plurality of ribs encircling the ring 9 on. These lead to a local stiffening or increase in strength, with a simultaneous reduction in wall thickness. Preferably one or more ribs 9 in the second and third areas of the outside tour 7 educated.

Ribs are created 9 through a corresponding groove in the mold wall when molding the plastic outer guide 7 .

Reference symbol list

1

Air spring

2nd

first connector / air spring cover

3rd

second connector / rolling piston

4th

Bellows

5

working space

6

Clamping ring

7

External guidance

8th

Tension ring

9

rib

10th

Roll fold

d

Wall thickness

B1

first area

B2

second area

B3

third area

B4

fourth area

QUOTES INCLUDE IN THE DESCRIPTION

This list of documents listed by the applicant has been generated automatically and is only included for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• DE 10119363 A1 [0004]

Claims (10)

Air spring (1) for a motor vehicle, the air spring (1) comprising an elastomeric bellows (4), which is clamped airtight between two connection parts (2; 3) of the air spring (1) and forms at least one roller fold (10) on one of the connecting parts (3) rolls, the rolling bellows (4) being at least partially surrounded by a sleeve-shaped outer guide (7) made of a plastic, characterized in that the outer guide (7) has a varying wall thickness (d.) in its longitudinal extension (L) ) having. Air spring (1) after Claim 1 , characterized in that the outer guide (7) comprises a first end region (B2) and a second end region (B4), the wall thickness (d) in the second end region (B4) being smaller than the wall thickness (d) in the first end region (B2). Air spring (1) after Claim 2 , characterized in that the second end region (B4) is provided for the connection of a protective bellows. Air spring (1) according to one of the Claims 1 to 3rd , characterized in that the outer guide (7) has a substantially cylindrical inner wall. Air spring (1) according to one of the Claims 1 to 4th , characterized in that the outer guide (7) has a substantially conical outer wall. Air spring (1) according to one of the Claims 1 to 5 , characterized in that at least one means for increasing the strength (9) is provided on the outer guide (7). Air spring (1) after Claim 6 , characterized in that the means for increasing strength (9) is formed from the plastic of the outer guide (7). Air spring (1) after Claim 6 or 7 , characterized in that the means for increasing strength (9) is arranged in a central region of the outer guide (7). Air spring (1) according to one of the Claims 1 to 8th , characterized in that the outer guide (7) is fixed to the rolling bellows (4) by a fastening ring (8). Chassis, in particular an air spring system, of a motor vehicle comprising an air spring (1) according to one of the Claims 1 to 9 .

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