DE10327485A1 - Active pneumatic spring system for vehicle suspension systems comprises a spring element with a chamber filled with a gas which is compressible/decompressible by means of a separated, controllable liquid medium - Google Patents

Abstract

The active pneumatic spring system for vehicle suspension systems comprises a spring element with a chamber filled with a gas which is compressible/decompressible by means of a separated liquid medium controllable by means of a motor driven hydraulic pump.

Description

Field of use:

The The invention includes an active pneumatic suspension system for a motor vehicle according to the preamble of claim 1.

State of the art:

• – Unabhängigkeit der Aufbaueigenfrequenz vom Beladungszustand [6]
• – weiche Federkennlinie mit progressiver Gestaltung hin zum Endanschlag
• – flexible Gestaltung der Federkennlinie über die Wahl der Kontur des Abrollkolbens
• – einfacher Niveauausgleich
• – gute Geräuschentkopplung des Aufbaus gegenüber dem Fahrwerk

Pneumatic suspension systems and their applications are very widely used in motor vehicles. For buses and commercial vehicles and their trailers and semitrailers, their market share is dominant. In high-end vehicles of automobile manufacturers, they are state of the art. The system advantages of these pneumatic suspension solutions are:

• - Independence of the body's own frequency from the loading condition [6]
• - Soft spring characteristic with progressive design towards the end stop
• - Flexible design of the spring characteristic via the choice of the contour of the rolling piston
• - easy leveling
• - Good noise isolation of the body compared to the chassis

Furthermore come semi-active systems used, you effect by the Decoupling the additional volume, about Control valves, a hardening the characteristic of the pneumatic suspension system for cornering (eg roll compensation in [3]). Furthermore, some have of these systems ([3], [9], [10]) the possibility the continuous change the damper characteristic using electronic control to improve driving comfort in overland and highway driving, as well as an increase in damping [9] on undulating roads.

Disadvantages of pneumatic Suspension systems (prior art):

at purely passive systems, the vehicle body tends more strongly Nodding and wavering and overshooting due to the softer connection. Achieve semi-active systems a reduction of the disadvantages described, but can z. B. no leveling or curve tilting during the Realize circle or partial cycle.

to Improved driving safety and driving comfort are offered Active hydraulic systems to influence the pitch, roll and vertical movement as partially used in spring / damper systems in automobiles of the upper class to the application [1] come.

There pure active pneumatic systems for this very large air mass flows need is an economical realization about compressor solutions for current State of the art only conditionally possible.

Alternative solutions:

Out DE 10045413A1 Such a suspension system is known, which uses a pneumatic air cushion to generate the support forces required on the vehicle body.

How it works: About one external hydraulic accumulator is an additional volume of air via a connecting line introduced into the passive pneumatic element. A comparable one Pneumatic volume is simultaneously from the opposite pneumatic Spring element (same vehicle axle) via the hydraulic coupling taken.

delimitation: In contrast to the presented solution this is an external actuation by means of additional volume. It serves exclusively for roll compensation of the vehicle body.

Out DE 4211628 A1 Another pneumatic suspension system for a motor vehicle is known, which also realizes the support of the vehicle body via an air cushion.

Functionality: The additional forces for the roll compensation be over generates an air line in conjunction with a piston-actuated additional volume. This piston is hydraulically driven horizontally. The oil volume is mechanical with a parallel system on the opposite axis side coupled, which causes an inverse behavior in the opposite spring element.

delimitation: In contrast to the presented solution this is another variant of an external one Activation by means of additional volume. It is exclusively for Roll compensation of the vehicle body.

Out DE 19804288 C1 For example, another active hydropneumatic suspension system for a motor vehicle is known which operates in place of a plunger cylinder via an oil-filled bellows or bellows solution in conjunction with a special hydropneumatic spring.

Functionality: The oil-filled hose reel solution allows one translatorisch working force actuator. The damping is over the hydraulic throttle and the suspension via the conventional hydraulic accumulator and achieved in parallel circuit with the elastomeric memory. actuated will be over one Reversible motor pump unit.

delimitation: In contrast to the presented solution this is a purely hydraulic actuator and a motor pump actuator that over the direction of rotation reversal and the speed change of the electric motor the Response dynamics realized.

Out EP 0504717 B1 is another pneumatic suspension system for a motor vehicle is known, which operates on a quasi-static change of the spring characteristic.

Functionality: The Pneumatikelement is structurally designed, which it partially with a liquid volume filled is what while the operation of the motor vehicle is constant. A change The spring stiffness can be achieved by the liquid filling of the Pneumatic spring element is varied.

at This patent focuses on switching the additional volume on and off with regard to roll compensation of the vehicle body.

delimitation: In contrast to the presented patent solution, this is a static solution. The fluid volume within the pneumatic spring is changeable, but not during the operation of the motor vehicle.

Object of the invention:

The invention ( 6 ) is based on the object to limit the disadvantages of today's pneumatic suspension systems, the excessive roll and pitching of the vehicle body due to the soft spring characteristic, or completely out. At the same time the ride comfort achieved so far should be increased under the premise of compliance or improvement of current driving safety with the most economical use of energy.

Solution of the task:

The object is achieved by an elastic hydro-pneumatic actuator ( 6 1) in conjunction with a +/- swiveling and adjustable hydraulic pump ( 6 Item 4) on the features of claim 1. The respective control modules are located on each suspension spring. The implementation is carried out by an elastic, hydraulic actuator with the direct actuation of the gas space of the pneumatic element via the method of fluid displacement (internal displacement principle). The drive of the hydraulic pump can be controlled by a separate electric motor ( 6 5) or directly from the internal combustion engine. About the vehicle sensors and their technical detection and coordination of vehicle movements are calculated on the information processing, the necessary additional forces and provided by a cascaded control system, the resulting flow rates of the respective self-sufficient hydraulic system.

Advantages of the invention:

• 1. Die positiven Eigenschaften der pneumatischen Federung bleiben vollständig erhalten (siehe Stand der Technik).
• 2. Je nach Regelungskonzept können die Systemfreiheitsgrade des Fahrzeugaufbaus, wie Huben, Nicken und Wanken, sowie ein lastunabhängiges Grundniveau der Einfederung beeinflusst bzw. vollständig kompensiert werden. Diese Maßnahmen dienen alle der Steigerung des Fahrkomforts bzw. der Fahrsicherheit des Kraftfahrzeugs.
• 3. Über die Verwendung eines Stahlarmierungszinges (2 Pkt. 5), an dem sich die Balgwand des pneumatischen Federelements abrollen bzw. abstützen kann, wird es ermöglicht mit einem höheren Betriebsfederdruck zu arbeiten. Dieses hat den Vorteil, dass das Bauvolumen der Pneumatikfeder reduziert werden kann bei vergleichbarer Traglast. Die Auswirkung im geregelten Betrieb ist, dass ein geringeres Verdrängervolumen benötigt wird, was den Energieverbrauch absenkt.
• 4. Zur weiteren Betriebsdrucksteigerung im Pneumatikfederelement wird die Kombination der Parallelschaltung zweier Pneumatikfederelemente mit gegensätzlicher Kraftwirkung in zwei Anwendungsbeispielen verwendet.
• 5. Die Innenaktuierung mittels eines elastischen Schlauchringelastomers auf der Basis des fluiden Verdrängerprinzips kann auf Grund der gewählten technischen Konfiguration je nach Fahrzeugtyp bauvolumensparend ausgeführt werden.
• 6. Die im 4-Quadrantenbetrieb +/– schwenk- und verstellbar arbeitende Hydraulikpumpe weist eine bessere Aktordynamik auf als standardisierte Steuerventillösungen mit Konstantpumpen oder die reversible Motor-Pumpeneinheit, die aus den Patenten DE 198 04288 C1 und DE 100 45 413 A1 bekannt ist.
• 7. Der globale und modulare Systemaufbau ermöglicht eine einfache Systemerweiterung um lokale Stellglieder, z. B. Fahrzeug mit weiteren Achsmodulen, kann ohne eine Neuentwicklung der Systemplattform erweitert werden.

The invention ( 6 ) has the following advantages:

• 1. The positive characteristics of the pneumatic suspension are completely retained (see prior art).
• 2. Depending on the control concept, the system degrees of freedom of the vehicle body, such as lifting, pitching and rolling, as well as a load-independent base level of the spring deflection can be influenced or completely compensated. These measures all serve to increase the driving comfort and the driving safety of the motor vehicle.
• 3. About the use of a steel reinforcement ring ( 2 Pkt. 5), on which the bellows wall of the pneumatic spring element can roll or support, it is possible to work with a higher operating spring pressure. This has the advantage that the construction volume of the pneumatic spring can be reduced with a comparable load. The effect in controlled operation is that a smaller displacement volume is needed, which lowers energy consumption.
• 4. For further operating pressure increase in the pneumatic spring element, the combination of the parallel connection of two pneumatic spring elements with opposite force effect is used in two application examples.
• 5. The Innenaktuierung by means of an elastic Schlauchringelastomers based on the fluid displacement principle can be carried out due to the selected technical configuration, depending on the vehicle type construction volume saving.
• 6. The 4-quadrant operation +/- swivel and adjustable working hydraulic pump has a better actuator dynamics than standard control valve solutions with constant displacement pumps or the reversible motor-pump unit, from the patents DE 198 04288 C1 and DE 100 45 413 A1 is known.
• 7. The global and modular system design allows for easy system expansion to include local actuators, e.g. B. vehicle with other axis modules can be extended without a new development of the system platform.

Drawings:

The embodiments of the invention are shown in the drawings ( 2 to 7 ) and explained in more detail in the following image description:
Note: To clarify the main differences in the respective Anwendungsbeispie In some cases, only the actual actuators have been mapped. On the representation of the supply device and the structural position in the vehicle has been omitted for equality reasons.

2 : Schematic representation of the system structure of the suspension with simple active pneumatic spring

3 : Schematic representation of a hose roll bellows with integrated hose ring in the bellows wall.

4 : Schematic representation of an oil filled pneumatic spring with internal pneumatic reservoir

5 : Schematic representation of a double pneumatic spring with a hose ring bladder

6 : Schematic representation of the system structure of the suspension with dual active pneumatic spring

7 : Schematic representation of a pneumatic spring module with double hose ring solution and integrated passive shock absorber

Description and mode of action of the embodiments:

The present invention has the ambition in a conventional motor vehicle to represent a complete new active hydro-pneumatic suspension system. Compared to a passive or semi-active pneumatic suspension system, the pitch and roll compensation, as well as a vertical control of the vehicle body is made possible. For this active intervention additional forces are required at the respective pneumatic spring units. In the present case, these additional forces by the direct fluid change, by means of a hydraulic actuator within the pneumatic space of the air spring element (positive displacement principle, 2 Item 6). This is a hydraulic medium from a +/- swivel and adjustable hydraulic pump ( 2 4) and sucked into an elastic reservoir (actuator, 2 , Point 6). This process reduces the residual volume for the gaseous medium in the pneumatic spring element ( 2 , 5), with the result that the chamber pressure increases significantly. Technically, not only an increase in pressure but a dynamic adjustment of the spring characteristic of the pneumatic spring element takes place. The target value is a bandwidth up to 6 Hz corner frequency. From an energetic point of view, the internal actuation compared to the external actuation has the advantage that no throttle losses occur via supply lines.

following become 5 outlined application solutions presented and explained in detail:

Variant A1 ( 2 ):

As an application example, the system structure of a suspension according to the McPherson principle is outlined. The spring damper module consists of a conventional one-pipe or two-pipe damper and a pneumatic spring element ( 5 ). The internal actuation of this pneumatic spring element by means of a hydraulic hose ring ( 6 ). Within the pneumatic spring element z. B. Rolling bellows ( 5 ) or bellows is via an elastic hose ring body (actuator, 6 ), filled with a hydrofluid, the nominal volume of the spring element ( 5 ) varies. The elastic ring body ( 6 ) assumes the function of compressing and displacing the gas into a pneumatic residual space. This dynamic system parameter changes the spring stiffness of the pneumatic spring system, or the nominal pressure of the pneumatic cushion, which causes an additional force. The 4-quadrant operation +/- swiveling and adjustable hydraulic pump ( 4 ) generates the necessary Verstelldynamik for such Aktuierung. The connected 3/2 way valve ( 3 ) contains the possibility between two characteristic curves of hydraulic accumulators ( 2 ), depending on the driving requirement profile (eg sporty or comfort-oriented) of the driver. These hydraulic accumulators ( 2 ) as a storage depot for the fluid medium and also provide over their bias the hydraulically necessary system forces in stationary rest position ready. The pneumatic chamber ( 5 ) is in each case via a corresponding line to a pressure supply ( 11 ) connected. Only in the stationary state of the motor vehicle, the level control via the pneumatic supply path. The pneumatic supply system ( 8th to 11 ) is required in all variants presented here.

For redundant system protection of the hose ring cylinder ( 6 ) this is secured with a metallic or fiber-reinforced mesh in the extreme position before overstretching. This fuse is used as an end stop in all shown hose ring solutions.

Variant A2 ( 3 ):

This variant is a higher-integrated version of variant 1. For this purpose, the hose ring cylinder ( 2 ) vulcanized into the fabric of the air spring element. The steel reinforcement ring ( 3 ) causes the support, so that the pressure surge in the actuation of the hydraulic annular bladder within the Pneumatic volume takes place.

Variant A3 ( 4 ):

In this application example, the basic idea is the replacement of the media within the pneumatic spring element. The pneumatic is replaced by the hydraulic or the hydraulic against the pneumatic medium. This means the pneumatic spring element ( 1 ) is filled with the hydraulic fluid. Within the fluid floats a pneumatic storage bubble (ring bubble, 2 ). A fixation via nylon threads (not shown). This design is an all-round actuation of the pneumatic volume. The shape and design depends on the requirement profile of the pneumatic spring element.

Variant A4 ( 5 ):

These Variant was developed to increase the system pressure within the air spring element, to reduce the energy consumption of Aktuierung and the constructive more compact design of the geometric shape.

The common rolling piston ( 4 ) is between two oppositely parallel hose bladders ( 5 u. 6 ) clamped. About the surface difference at the rolling piston ( 4 ) and the pressure differences of the two pneumatic chambers, the differential force for the actual supporting the motor vehicle is generated. Functionally, this is the parallel connection of two pneumatic springs with opposite signs in the direction of force.

The system is constructed as follows: The two pneumatic springs are supported by the flange ( 3 ) on the vehicle body. About the connection bracket ( 9 ), the lower flange forces ( 7 ) introduced upward into the structure. In order to achieve a compact construction of the spring element, in this arrangement an interlocking piston shape ( 4 ) has been chosen. This selected principle is well suited for difficult geometrical mounting positions. A disadvantage is the limited formable piston contour surface. The passive influence of the spring stiffness is very limited by this solution form. It remains the active influence on the hose ring bubble ( 2 ) in the upper pneumatic spring element, which leads to an additional energy expenditure.

The scope for the translation ratio on the choice of the piston surfaces are narrow limits, due to the intermeshing of the two pneumatic spring elements. To avoid frictional forces on the inlet and outlet sealing element of the piston rod, the solution is a third rolling bellows (US Pat. 10 ) used. The advantage of working against each other pneumatic springs is that can be worked on this mutual system distortion of the spring elements with a significantly higher system pressure in the respective pneumatic chambers. This effect favors low fluid flow rates for the internal displacement principle. The reduced volume flows have a negative effect on energy consumption.

Variant A5 ( 6 ):

This variant is a further development of the variant A5 in terms of structural design and functionality. In 6 shows the system structure of the suspension with dual active pneumatic spring.

For reasons of clarity, the system structure of the pneumatic spring variant A5 ( 6 ) through the detail view ( 7 ).

Due to the parallel arrangement of the two pneumatic springs ( 7 Pt. 1 u. 7 Pkt. 6) more constructive space in the vertical is needed. If this space is available, then an optimal design of the piston contour surfaces ( 7 Pkt. 4) and the transmission ratio (piston surfaces) possible. Another distinguishing criterion for variant A4 is the actuation of the second pneumatic spring ( 7 Point 7). Depending on the direction of the +/- swiveling and adjustable hydraulic pump ( 7 5) one of the pneumatic spaces is actuated and the opposite space serves as a fluid reservoir. In this case, a pressure reduction takes place in the space of the fluid reservoir, which, in terms of energy, positively influences the tensioned solution in terms of energy consumption. A special feature of this system is that the hose ring ( 7 Pkt. 7) has dual function as a regulator and as a fluid reservoir. The 3/2 way valve ( 7 3) includes the option of extending the basic functionality by the option of additional fluid volume from a hydraulic accumulator ( 7 2) into the hydraulic system or deliver. Thus, a vehicle base level change or system pressure change can be achieved.

For impressing additional system damping there is a connecting line between the two pneumatic volumes, which is a gas throttle ( 7 Item 10). The higher system pressure of the two air spring elements favors the use of the gas throttle. The gas volume flows are throttled and the gas vibrations are damped. Depending on the application, constant or variable gas throttles ( 7 Pt. 10). ever according to the requirement profile of the producer, the parallel connection of a passive oil damper ( 7 Point 9) or on the connecting line with adjustable pipe throttle ( 7 , Item 10) in individual cases.

For conventional McPherson suspension, the contour piston ( 7 4) designed so that it ensures the passage of the damper piston rod and in the foot area on the damper outer tube ( 7 Item 9) supports the application of the actuating forces. The sealing of the second pneumatic chamber ( 7 Pkt. 6) takes place through the hose roll seal ( 7 8) directly on the damper tube ( 7 Point 9). If the damper is omitted, then a piston rod would be needed at this point.

Depending on the use of a pneumatic medium that can diffuse due to molecular properties through the bellows walls of the pneumatic spring elements, an on-board pneumatic supply ( 6 Pts. 8 to 11) or foreign supply during the routine inspection. Low partial losses can be achieved via the hydraulic accumulator ( 6 2), can be compensated for by increasing the volume of fluid in the circuit.

Remarks:

The in the figures shown cylindrical Abrollgeometrien the piston shapes, (concave or convex shapes) are exemplary for the respective solutions been specified.

A Concrete shaping can only be done as part of a chassis design, based on the requirement profile of the customer become.

The necessary for the adjustment positive or negative hydraulic flow is generated in all of the application examples presented here by a 4-quadrant operation +/- swiveling and adjustable working hydraulic pumps / engine storage valve unit. An adjustable swivel or axial piston pump with stepless volume adjustment should be used. As a special feature of the pump is the pivoting through the zero crossing, so that the suction and pressure side is not well defined. In the design, it can be used as a directly flanged version with an electric motor or a full oil-powered version. The direction of rotation of the electric motor is not reversible but adjustable in speed. The patent DE 19840791 A1 relating to a 4-quadrant vane pump is not affected.

easy solutions for providing the volume flows via standard hydraulic components (Pump or valve solutions) are in principle applicable, but offer a lower dynamic Response. This application option is the one described here Patent covered.

Literature:

• [1] Braess / Seiffert (ed.): Vieweg Handbook Automotive Technology, Vieweg-Verlag, 1st edition 10.2000;
• [2] Robert Bosch GmbH, (ed.): Automotive Handbook, 24th edition, Vieweg-Verlag, act. u. ext. Edition 2002;
• [3] Extrapublication of the journal ATZ u. MTZ: The new Mercedes-Benz E-Class, Vieweg Verlag, May 2002 edition;
• [4] Reimpell, J .: Chassis technology: basics, 4th, completely revised Edition, Vogel Fachbuch Verlag, Würzburg, 2000;
• [5] Wallentowitz H .: Vertical, lateral dynamics of motor vehicles: Suspension systems, handling, steering, suspension, lecture overprint, 5th edition, Aachen, 2001;
• [6] Voss, H .: the air suspension, a controllable vehicle suspension, lecture, Technical Academy Esslingen, Hanover October 14, 1998;
• [7] Ivantsyn J., Ivantsyn M .: Hydrostatic pumps and motors, Vogel Fachbuchverlag, 1st edition 1993;
• [8] Krist, T .: Hydraulics / Fluid Technology, Vogel Buchverlag, B. 1997 edition.
• [9] Extrapublication of the journal ATZ u. MTZ: The new Audi A8, Vieweg Verlag, August 2002 edition;
• [10] Extrapublication of the journal ATZ u. MTZ: The new Maybach, Vieweg Verlag, issue September 2002;
• [11] Mitschke M .: Dynamics of Motor Vehicles, Bd. B. Vibrations, 4th revised edition 2002;
• [12] Matschinsky W .: The wheel guides of road vehicles, Kinematics, elasto-kinematics and construction, Springer Verlag, 2. Edition, 1998;

Claims (7)

Active pneumatic suspension system for a motor vehicle, which has on each vehicle axle and on each side of the vehicle a pneumatic spring element ( 7 Point 5.) with pneumatic cushion, with which the vehicle body is supported via a mechanical chain of action on the vehicle on the road. The support forces acting between the vehicle and the structure are applied and transmitted by the pneumatic spring element. The pneumatic spring element is characterized in that the pneumatic space is filled with a gas and by a fluid medium (Verdrängerprinzip ( 7 Pkt. 6)) can be compressed or relaxed. To separate the gaseous and the fluid medium are Ringschlauch-, membrane or piston surface solutions. The variable internal fluid space (in the suspension element) is connected to a 4-quadrant operation +/- swivel and adjustable hydraulic pump ( 7 Point 4). This can optionally by an electric motor unit ( 7 Pkt. 1) or driven directly by an internal combustion engine. The reversible and adjustable hydraulic pump ( 7 4) is connected via a 3/2 way valve ( 7 3) from a prestressed accumulator ( 7 2). The patent and its claims are binding if the supply of the hydraulic part of simple pump designs or valve solutions. This type of actuation is used to influence the vehicle body based on the pitch, roll and Huben, as a joint or individual influence. Suspension system according to claim 1, characterized in that two parallel-connected pneumatic spring elements ( 7 Point 1. u. Pkt. 6) against each other and optionally via a hose ring solution ( 7 Pkt. 7) can be actuated as an actuator. Suspension system according to claim 1 to 2, characterized in that the hydraulic actuators via a reversible and adjustable hydraulic pump ( 7 Item 5). Suspension system according to claim 1 to 3, characterized in that the parallel-connected double pneumatic spring element ( 7 ) can be mutually actuated. Here is the hydraulic actuator, a reversible and adjustable hydraulic pump ( 7 5) or standard hydraulic pump in the connecting line of the two actuators ( 7 Point 7). Suspension system according to claim 1 to 4, characterized in that in the hydraulic connecting line for the parallel, double, pneumatic spring element ( 7 ) to the hydraulic pump ( 7 , Pkt. 5) additionally a control valve ( 7 3) in conjunction with a membrane ( 7 2) or a piston accumulator. This causes the additional provision or recording of fluid volumes for the self-sufficient hydraulic system. Suspension system according to claim 1 to 5, characterized in that the mutually-working pneumatic spring elements are connected to each other via a pneumatic connecting line and via an adjustable pneumatic throttle ( 7 10) for system damping. Suspension system according to claim 1, characterized in that the actuator as a hose ring ( 4 Pkt. 7) is formed and whose security is secured against material overstretching by a nylon, chain or other type network.