Spring assembly for a vehicle

Abstract

A spring assembly (1) for a vehicle, more particularly utility vehicle (1), comprises at least a first spring (2) and at least a second spring (3) that are arranged connected in parallel. The spring assembly (1) is a non-linear spring assembly (1) with a progressive load deflection curve (12). A strut comprising a spring assembly (1) of this type is provided.

Description

[0001] SPRING ARRANGEMENT FOR A VEHICLE

[0002] The present invention relates to a spring arrangement for a vehicle, in particular a commercial vehicle, according to the preamble of claim 1. The invention also relates to a spring strut of a vehicle, in particular a commercial vehicle, having such a spring arrangement.

[0003] The current state of the art predominantly provides for spring arrangements / suspensions in commercial vehicles using air springs. In this case, compressed air is provided by a compressor mounted on the vehicle. The suspension is based on the compressibility of the compressed air in the bellows.

[0004] The spring stiffness can be adjusted to the vehicle's load by varying the air pressure. Adjusting the air pressure also allows the vehicle ride height to be adjusted.

[0005] During vehicle operation, the suspension's task is to ensure a constant natural frequency of the statically and dynamically loaded vehicle. This requires that the suspension stiffness be adjusted accordingly, depending on the vehicle's mass and load condition.

[0006] The suspension, together with the vehicle, forms a vibration-prone system that is excited to vibrate by external forces. The vehicle exhibits a natural frequency that depends on its weight and load. Vibration is excited during travel by uneven road surfaces, wind loads, and changes in driving conditions (e.g., acceleration, deceleration, cornering).

[0007] A disadvantage of suspensions with a linear spring characteristic is that their constant spring stiffness results in different natural frequencies depending on the load of the commercial vehicle. Conventional air suspensions therefore allow the spring stiffness to be adapted to the load condition by varying the air pressure, but this requires the inclusion of numerous components of the compressed air supply including their peripherals (e.g. compressor, air dryer, compressed air reservoir, pressure regulators and sensors, control electronics). A key aspect that justifies this additional effort so far is the fact that the compressed air can often also be used for other purposes (e.g. air brakes). However, against the backdrop of the increasing electrification of commercial vehicles, alternative braking concepts (e.g.electric brakes) is becoming increasingly important, so that carrying the compressed air units for the sole use of air suspension no longer seems justified.

[0008] The invention is therefore based on the object of creating a suspension / spring arrangement, in particular taking into account the vehicle dynamics, wherein the above-mentioned disadvantages no longer occur or are significantly reduced.

[0009] This object is achieved by a spring arrangement having the features of claim 1. The object is also achieved by a spring strut having the features of claim 11.

[0010] The present invention presents a concept for the suspension of commercial vehicles. It meets the vehicle dynamic requirement of a nearly constant natural frequency independent of the vehicle load.

[0011] Accordingly, a spring arrangement according to the invention for a vehicle, in particular a commercial vehicle, comprises at least one first spring and at least one second spring arranged in parallel. The spring arrangement is designed as a non-linear spring arrangement with a progressive spring characteristic.

[0012] A particular advantage here is that the suspension has a nonlinear or progressive characteristic curve. Starting from a low stiffness level in the unloaded state, the spring stiffness increases with increasing vehicle load or with increasing spring compression. The progressive increase in the spring characteristic curve thus compensates for the influence of the increasing vehicle mass and results in a nearly constant level of the vehicle's natural frequency.

[0013] In contrast, the natural frequency of a conventional suspension with a linear spring characteristic or constant stiffness decreases significantly with increasing vehicle mass. Thus, the nonlinear spring concept offers the advantage of a natural frequency that is virtually independent of the load. Furthermore, unlike air suspension, which requires active control to adapt the air pressure or stiffness to the load condition, this is a passive suspension concept.

[0014] A spring strut of a vehicle, in particular a commercial vehicle, with a spring arrangement, a frame and a plate displaceably guided in the frame has the spring arrangement described above.

[0015] In one embodiment, the spring assembly is arranged in a frame that is movable relative to a plate in the translational direction along a path, with the plate being guided within the frame so that it can be displaced in the translational direction. This results in an advantageously compact design.

[0016] A further embodiment provides that the at least one first spring of the spring arrangement has at least one spring element, and that the at least one second spring has two spring elements. One advantage of this is easy adaptability to different applications.

[0017] It is advantageous if the at least one first spring of the spring arrangement has a constant spring stiffness and the at least one second spring has a non-linear spring stiffness, since the two types of spring can thus be dimensioned and arranged independently of one another to adapt to different applications.

[0018] In one embodiment, the at least one second spring with the nonlinear spring stiffness can have regions with and without negative stiffness. In this way, the stiffness of the at least one second spring can change from negative to positive depending on the load condition, thereby advantageously generating a nonlinear characteristic curve. Such a spring arrangement can thus be designed as a linear spring in combination with at least one nonlinear spring element.

[0019] In yet another embodiment, the at least one spring element of the at least one first spring with constant spring stiffness is hinged to the frame, with the other spring end of the spring element being attached to the plate. This structure is advantageously simple.

[0020] Another embodiment provides that the at least one second spring with the nonlinear spring stiffness is constructed from two spring elements arranged in pairs and inclined to a translation direction running in the direction of gravitational acceleration. This results in an advantageously simple structure.

[0021] In a further embodiment, a first end of the first spring element of the at least one second spring is attached to a projection protruding from an inner ceiling wall of the frame, wherein a first end of the second spring element of the at least one second spring is hinged to an inner side wall of the frame, wherein the two spring elements of the at least one second spring are joined together at a common hinge point and hinged to the plate. This enables a compact and simple design.

[0022] Further advantageous embodiments of the invention can be found in the subclaims.

[0023] In one embodiment, the common pivot point of the other spring ends of the two spring elements of the at least one second spring is attached to a projection protruding from the plate. This design has the advantage of being space-saving.

[0024] A further embodiment provides that the first spring ends of the spring elements of the at least one second spring lie in a common plane, with this plane running perpendicular to the translation direction. One advantage of this is that a simple arrangement of the spring elements is possible to design the nonlinear spring.

[0025] One design of the strut provides for the frame to be connected to the chassis of a vehicle, and for the plate to be attached to the wheel suspension of a vehicle wheel of the vehicle. This is advantageous for quick installation and removal during assembly, repair, and maintenance.

[0026] If the plate is guided displaceably in a translation direction in the frame, wherein the translation direction runs along a path in the direction of the acceleration due to gravity, a simple structure is advantageously achieved.

[0027] An embodiment of the invention is described below with reference to the accompanying drawings. The invention is not limited to this embodiment. In particular, individual features of the following embodiments can be used not only in these, but also in other embodiments. They show:

[0028] Figures 1 -2: schematic representations of an embodiment of a suspension of a vehicle according to the invention in different load conditions;

[0029] Figures 3-5: symbolic representations of a spring arrangement of the embodiment in the different load conditions according to Figures 1 and 2; and

[0030] Figure 6-7: Diagrams with spring characteristics of the embodiment according to Figure 1 -3.

[0031] In the following, terms such as “top” or “bottom” refer to the respective drawing level.

[0032] Figure 1 shows a schematic representation of an embodiment of a suspension arrangement 1 according to the invention of a vehicle in a load state in which a load is applied by a chassis 8 of the vehicle.

[0033] Figure 2 shows the suspension arrangement 1 of the exemplary embodiment according to Figure 1 in a loaded state with the chassis and an additional load 9. Figures 3-5 show symbolic representations of the spring arrangement 1 of the exemplary embodiment in the various load states according to Figures 1 and 2.

[0034] Figures 1-2 show a spring arrangement 1 in two different loading conditions.

[0035] The spring arrangement 1 is designed as a non-linear spring arrangement and comprises a first spring 2 with a constant spring stiffness kpsE and a second spring 3 with a non-linear spring stiffness kNSE. The first spring 2 has a spring element 2a, while the second spring 3 is designed with two spring elements 3a and 3b. The first spring 2 with the constant spring stiffness kpsE and the second spring 3 with the non-linear spring stiffness kNSE are arranged in a parallel circuit.

[0036] The spring element 2a of the first spring 2 with the constant spring stiffness kpsE is articulated with a first spring end to an inner ceiling wall of the frame 4 in a first frame articulation 4a, wherein the other spring end of the spring element 2a of the first spring 2 with the constant spring stiffness kpsE is attached to the plate 5 in a first plate articulation 5a.

[0037] The second spring 3 with the non-linear spring stiffness kNSE is constructed from two spring elements 3a and 3b arranged in pairs and inclined to the translation direction u.

[0038] A first end of the first spring element 3a of the second spring 3 is fastened in a second frame articulation 4b to a projection 4d of the inner ceiling wall of the frame 4, wherein a first end of the second spring element 3b of the second spring 3 is articulated to a third frame articulation 4c on an inner side wall of the frame 4. The second frame articulation 4b and the third frame articulation 4c have an identical position value u in the translation direction relative to a common base, which is indicated here as reference R. In other words, the second frame articulation 4b and the third frame articulation 4c lie in a common plane. This plane is perpendicular to the translation direction.

[0039] The two spring elements 3a, 3b of the second spring 3 are joined at a common articulation point with their other spring ends hinged to a second plate articulation 5b on the plate 5. The second plate articulation 5b is located on a projection 5c projecting inwards from the plate 5, ie into the frame 4.

[0040] In an unloaded load state of the spring arrangement 1, which is not shown here but is conceivable, the springs 2 and 3, ie their spring elements 2a, 3a, 3b, are completely relaxed.

[0041] When the spring assembly 1 is loaded with the weight of the chassis 8 of the associated vehicle, the frame 4 is displaced beyond the plate 5 relative to the latter such that the plate 5 is located approximately in a lower quarter of the frame 4. This is schematically indicated in Figure 1. The frame 4 is displaced with its lower edge to a first position ui. The value of the first position ui is greater with respect to the reference R than a value in the unloaded loading state.

[0042] In this load condition according to Figure 1, the spring assembly 1 is statically preloaded by the mass of the chassis 8. The nonlinear stiffness of the second spring 3 with the spring elements 3a, 3b is at its absolute minimum.

[0043] Figure 2 shows the statically preloaded spring arrangement 1 when loaded by the mass of the chassis 8 and additionally by a load 9, in which the first spring 2 and the second spring 3 each have positive stiffnesses.

[0044] Here, the frame 4 is positioned with its lower edge at a second position U2 that is greater than ui. The plate 5 is located approximately at the height of a side center in the frame 4, with the side center being approximately half the length of the inside of the frame 4 in the translation direction u.

[0045] Figures 3-5 show symbolic representations of the spring arrangement 1 of the embodiment in the various load conditions according to Figures 1 and 2 with the corresponding values ​​of the positions ui and U2 of the frame 4.

[0046] The frame 4 is only indicated. Figure 3 shows the spring assembly 1 with symbols for the first spring 2 and the second spring 3.

[0047] The spring assembly 1 comprises the first spring 2 with the spring element 2a having a constant spring stiffness kpsE and the second spring 3 consisting of the spring elements 9a and 9b having a nonlinear spring stiffness kNSE. The spring assembly 1 is arranged between the frame 4 and the plate 5, as described above.

[0048] The parallel connection of the first spring 2 (kpsE) and the second spring 3 (kNSE) results in a total spring stiffness ktotai, as shown in Figure 4 with only one spring symbol.

[0049] Figure 5 symbolically represents spring arrangement 1 with total spring stiffness ktotai in the load condition with chassis 8 and load 9 according to Figure 2. The total spring stiffness ktotai results from the addition of the spring characteristics 10, 11 (see Figure 7) of the first spring 2 (kpsE) and the second spring 3 (kNSE). This is described further below in connection with Figure 6.

[0050] Figure 6 shows a diagram with spring characteristics 10, 11, 12 of the spring arrangement 1 for one of the spring struts of the associated vehicle.

[0051] The X-axis of the diagram represents the distance u (translation direction) in m between the reference R and the lower edge of frame 4 (see Figures 1-2). The Y-axis shows the load F as a weight force in N.

[0052] The diagram shows a spring characteristic curve 10 of the first spring 2 with the constant stiffness kpsE, a spring characteristic curve 11 of the second spring 3 with the non-linear stiffness kNSE and a progressive spring arrangement characteristic curve 13 of the spring arrangement 1 with the total stiffness ktotai.

[0053] When the vehicle or commercial vehicle is unloaded, the spring assembly 1 is preloaded by the mass of the chassis 8 (see Figures 1, 3, 4). This is marked by a load point 13 on the spring assembly characteristic curve 13.

[0054] In the loaded state, in addition to the chassis 8, the weight force F of the load 9 acts on the spring assembly 1 (see Figures 2 and 5). This state is indicated on the spring assembly characteristic curve 13 by the load point 14.

[0055] Figure 7 shows a diagram showing the resulting natural frequency f as a function of the vehicle mass per strut m of the associated vehicle / commercial vehicle. The natural frequency f in Hz is plotted against the vehicle mass in kg.

[0056] In addition, a frequency band 17 with an upper band limit 17a with the cut-off frequency of 2 Hz (upper limit) and with a lower band limit 17b with the cut-off frequency of 1 Hz (lower limit) is entered in the diagram.

[0057] The natural frequency of a linear suspension arrangement, which is shown here by a spring arrangement characteristic curve 15, is reduced by a factor of 2 with increasing load and thus with increasing vehicle mass m. In the range of a vehicle mass m of approximately 3870 kg, the spring arrangement characteristic curve 15 leaves the frequency band 17, intersects the lower band limit of 1 Hz and continues to smaller values ​​below 1 Hz.

[0058] In contrast, the nonlinear spring arrangement characteristic curve 16 of the spring arrangement 1 according to the invention is significantly flatter and remains within the frequency band 17 as the vehicle mass increases. In other words, the nonlinear spring arrangement characteristic curve 16 of the spring arrangement 1 according to the invention results in a smaller frequency drop and thus ensures compliance with the prescribed frequency band 17 of 1 Hz to 2 Hz.

[0059] In this way, the vehicle dynamic requirement of a nearly constant natural frequency is met regardless of the vehicle load. For this purpose, the spring arrangement 1 has the non-linear or progressive spring arrangement characteristic curve 12 or 16. Starting from a low stiffness level in the unloaded state, the spring stiffness increases with increasing vehicle load or with increasing spring compression. The progressive increase in the spring arrangement characteristic curve 12 or 16 thus compensates for the influence of the increasing vehicle mass m and results in a nearly constant level of the natural frequency f of the associated vehicle. In contrast, when using a conventional suspension with a linear spring characteristic curve or constant stiffness, the natural frequency f decreases significantly with increasing vehicle mass, which is represented by the spring arrangement characteristic curve 15 of the conventional suspension.

[0060] In a design not shown but easily conceivable, the at least one second spring with nonlinear stiffness has regions with and without negative stiffness. The stiffness changes from negative to positive depending on the load condition, thereby creating a nonlinear characteristic curve. Such a spring design is configured as a linear spring in combination with one or more nonlinear spring elements.

[0061] Thus, the nonlinear spring concept of spring arrangement 1 with nonlinear spring stiffness offers the advantage of a natural frequency f that is virtually independent of the load. Furthermore, unlike air suspension, which requires active control to adapt the air pressure or the stiffness of the suspension to the load condition, this is a passive suspension concept. The invention is not limited by the exemplary embodiment specified above, but can be modified within the scope of the claims.

[0062] List of reference symbols

[0063] Suspension arrangement 1

[0064] First Spring 2

[0065] Spring element 2a

[0066] Second Spring 3

[0067] Spring element 3a, 3b

[0068] Frame 4

[0069] Frame linkage 4a, 4b, 4c

[0070] Projection 4d

[0071] Plate 5

[0072] Plate linkage 5a, 5b

[0073] Projection 5c

[0074] Wheel suspension 6

[0075] Vehicle wheel 7

[0076] Chassis 8

[0077] Charge 9

[0078] Spring characteristic curve 10, 11

[0079] Spring arrangement characteristic curve 12

[0080] Load point 13, 14

[0081] Spring arrangement characteristic curve 15, 16

[0082] Frequency band 17

[0083] Band boundary 17a, 17b

[0084] Acceleration due to gravity g

[0085] Spring stiffness k

[0086] Load F

[0087] Natural frequency f

[0088] Vehicle mass m

[0089] Reference R

[0090] Way and

Claims

Claims 1 . Spring arrangement (1) for a vehicle, in particular a commercial vehicle (1), comprising at least one first spring (2) and at least one second spring (3) which are arranged in parallel, characterized in that the spring arrangement (1) is designed as a non-linear spring arrangement (1) with a progressive spring characteristic curve (12).

2. Spring arrangement (1) according to claim 1, characterized in that the spring arrangement (1) is arranged in a frame (4) which is movable relative to a plate (5) in the translation direction on a path (u), wherein the plate (5) is guided displaceably in the frame (4) in the translation direction.

3. Spring arrangement (1) according to claim 1 or 2, characterized in that the at least one first spring (2) of the spring arrangement (1) has at least one spring element (2a) and that the at least one second spring (3) has two spring elements (3a and 3b).

4. Spring arrangement (1) according to claim 3, characterized in that the at least one first spring (2) of the spring arrangement (1) has a constant spring stiffness (kpsE) and the at least one second spring (3) has a non-linear spring stiffness (kNSE).

5. Spring arrangement (1) according to claim 4, characterized in that the at least one second spring (3) with the non-linear spring stiffness (kNSE) has regions with and without negative stiffness.

6. Spring arrangement (1) according to one of claims 3 to 5, characterized in that the at least one spring element (2a) of the at least one first spring (2) with the constant spring stiffness (kpsE) is articulated on the frame (4), wherein the other spring end of the spring element (2a) is attached to the plate (5).

7. Spring arrangement (1) according to claim 5 or 6, characterized in that the at least one second spring (3) with the non-linear spring stiffness (kNSE) is constructed from two spring elements (3a and 3b) arranged in pairs and inclined to a translation direction running in the direction of the gravitational acceleration (g).

8. Spring arrangement (1) according to claim 7, characterized in that a first end of the first spring element (3a) of the at least one second spring (3) is fastened to a projection (4d) protruding from an inner ceiling wall of the frame (4), wherein a first end of the second spring element (3b) of the at least one second spring (3) is articulated to an inner side wall of the frame (4), wherein the two spring elements (3a, 3b) of the at least one second spring (3) are articulated to the plate (5) with their other spring ends brought together at a common articulation point.

9. Spring arrangement (1) according to claim 8, characterized in that the common articulation point of the other spring ends of the two spring elements (3a, 3b) of the at least one second spring (3) is attached to a projection (5c) projecting from the plate (5).

10. Spring arrangement (1) according to claim 8 or 9, characterized in that the first spring ends of the spring elements (3a, 3b) of the at least one second spring (3) lie in a common plane, this plane extending at right angles to the translation direction.

11. Suspension strut of a vehicle, in particular a commercial vehicle, with a spring arrangement (1), a frame (4) and a plate (5) displaceably guided in the frame (4), characterized in that the spring arrangement (1) is designed according to one of the preceding claims.

12. Suspension strut according to claim 11, characterized in that the frame (4) is connected to a chassis (8) of an associated vehicle and that the plate (5) is fastened to a wheel suspension (6) of a vehicle wheel (7) of the associated vehicle.

13. Suspension strut according to claim 12, characterized in that the plate (5) is guided displaceably in a translation direction in the frame (4), wherein the translation direction runs along a path (u) in the direction of the acceleration due to gravity (g).

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