SPRING DEVICE

Abstract

A spring device (1A, 1B) for a motor vehicle (2), comprising a spring unit (3) and a stiffness adjusting unit (15) configured to stiffen the spring unit (3) so as to dynamically vary the spring constant (k, k′) of the spring device (1A, 1B).

Claims

1. Spring device for a motor vehicle, comprising: a spring unit; and a stiffness adjusting unit configured to stiffen the spring unit so as to dynamically vary the spring constant of the spring device.

2. Spring device according to claim 1, characterized in that the spring unit is made of a fiber reinforced plastic.

3. Spring device according to claim 1, characterized in that the spring unit is a leaf spring unit.

4. Spring device according to claim 3, characterized in that the spring unit comprises a plurality of leaf spring sections and a plurality of deflection sections, and in each case one deflection section connecting two adjacent leaf spring sections to one another.

5. Spring device according to claim 4, characterized in that the leaf spring sections comprise an S-shaped geometry.

6. Spring device according to claim 1, characterized in that the stiffness adjusting unit comprises a stiffening element for stiffening the spring unit, which is attached to the spring unit.

7. Spring device according to claim 6, characterized in that the stiffening element is cylindrical.

8. Spring device according to claim 6, characterized in that the stiffening element encloses the spring unit at least in sections.

9. Spring device according to claim 6, characterized in that the spring unit comprises a soft spring section with a first spring constant and a hard spring section with a second spring constant, wherein the second spring constant is greater than the first spring constant, and wherein the stiffening element is attached only to the soft spring section.

10. Spring device according to claim 9, characterized in that the stiffening element is adapted to deactivate the soft spring section.

11. Spring device according to claim 6, characterized in that the stiffness adjusting unit comprises a control apparatus for actuating the stiffening element, wherein the stiffening element can be brought from a deactivated state into an activated state and vice versa by means of the control apparatus, and wherein the spring constant of the spring device in the activated state is greater than in the deactivated state.

12. Spring device according to claim 11, characterized in that an arbitrary number of intermediate states is provided between the deactivated state and the activated state, so that the spring constant of the spring device can be varied continuously.

13. Spring device according to claim 11, characterized in that the stiffening element can be brought from the deactivated state into the activated state by means of a current applied to it, by means of an electric field and/or by means of a magnetic field.

14. Spring device according to claim 11, characterized in that when the stiffening element is brought from the deactivated state into the activated state, properties, in particular material properties and/or geometric properties, of the stiffening element change in such a way that the spring constant of the spring device increases.

15. Spring device according to claim 6, characterized in that the stiffening element comprises a magnetorheological material and/or an electrorheological material.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0050] FIG. 1 shows a schematic view of an embodiment of a spring device;

[0051] FIG. 2 shows a further schematic view of the spring device according to FIG. 1;

[0052] FIG. 3 shows the detailed view III according to FIG. 1;

[0053] FIG. 4 schematically shows a force-deflection curve of the spring device according to FIG. 1;

[0054] FIG. 5 again shows the detailed view III according to FIG. 1;

[0055] FIG. 6 schematically shows a further force-deflection curve of the spring device according to FIG. 1;

[0056] FIG. 7 shows a schematic view of a further embodiment of a spring device;

[0057] FIG. 8 schematically shows a force-deflection curve of the spring device according to FIG. 7;

[0058] FIG. 9 shows a further schematic view of the spring device according to FIG. 7; and

[0059] FIG. 10 schematically shows a further force-deflection curve of the spring device according to FIG. 7.

[0060] In the figures, identical or functionally identical elements have been provided with the same reference signs, unless otherwise indicated.

DETAILED DESCRIPTION

[0061] FIG. 1 shows a schematic view of a spring device 1A. The spring device 1A is, or may be described as, a leaf spring device. However, the spring device 1A may be any embodiment of a spring, for example a coil spring or the like. However, hereinafter it will be understood that the spring device 1A is a leaf spring device. The spring device 1A is suitable for use in or on a motor vehicle 2, in particular on a wheeled vehicle. The spring device 1A may find application in the region of a wheel suspension of the motor vehicle 2. The motor vehicle 2 may comprise any number of spring devices 1A.

[0062] The spring device 1A comprises a spring unit 3. The spring unit 3 is, or may be described as, a leaf spring unit. However, the spring unit 3 may also be a coil spring, for example. The spring unit 3 is made of a fiber-reinforced plastic material or a fiber reinforced plastic (FRP). Alternatively, however, the spring unit 3 may also be at least partially made of a metallic material, for example spring steel. In the following, however, it will be assumed that the spring unit 3 is made of a fiber-reinforced plastic material.

[0063] The fiber composite plastic comprises a plastic material, in particular a plastic matrix, in which fibers, for example natural fibers, glass fibers, carbon fibers, aramid fibers or the like, are embedded. The plastic material may be a thermoset, such as an epoxy resin. However, the plastic material may also be a thermoplastic. The fibers may be continuous fibers. However, the fibers may also be short or medium length fibers, which may have a fiber length of a few millimeters to a few centimeters. The spring unit 3 may have a layered or stratified structure. For this purpose, layers of fiber fabric or fiber scrim are impregnated with the plastic matrix, for example. Alternatively, however, so-called prepregs, i.e. pre-impregnated fibers, fiber fabrics or fiber webs, can also be used to manufacture the spring unit 3.

[0064] The spring unit 3 has a meandering geometry. The spring unit 3 has a plurality of leaf spring sections 4 which are connected to each other at deflection sections 5. The number of leaf spring sections 4 is arbitrary. In FIG. 1, a leaf spring section 4 and a deflection section 5 are each provided with a reference sign. The individual leaf spring sections 4 each have an S-shaped geometry or have an S-shaped course in the side view.

[0065] The leaf spring sections 4 can be connected to each other integrally, in particular integrally made of one material, by means of the deflection sections 5. “Integrally” or “one-piece” means in the present case that the leaf spring sections 4 and the deflection sections 5 form a common component and are not composed of different components. “Integrally made of one material” means in particular that the leaf spring sections 4 and the deflection sections 5 are made of the same material throughout.

[0066] The leaf spring sections 4 and the deflection sections 5 are designed in such a way that, when the spring unit 3 is loaded, no deformation, or at least no appreciable deformation, takes place in the deflection sections 5. The leaf spring sections 4, on the other hand, are each deformed in a central region 6 and generate a spring force counteracting a load acting from the outside.

[0067] A first end section 7 of the spring unit 3 is supported in a first bearing unit 8. A second end section 9 of the spring unit 3 is accordingly supported in a second bearing unit 10. The first bearing unit 8 may, for example, be part of a frame of the motor vehicle 2. The second bearing unit 10 may be part of an axle guide of the motor vehicle 2. The bearing units 8, 10 are part of the spring device 1A. With respect to a direction of gravity g, the first bearing unit 8 is placed above the second bearing unit 10. The first bearing unit 8 is, or may be described as, a spring shoe. The second bearing unit 10 is also a spring shoe or may be referred to as such.

[0068] FIG. 1 shows the spring device 1A in an unloaded or deflected state. In contrast, FIG. 2 shows the spring device 1A in a loaded or compressed state. In the compressed state, the leaf spring sections 4, which are S-shaped in the unloaded state, have a planar shape.

[0069] FIG. 3 shows the detailed view III according to FIG. 1. As previously mentioned, the spring unit 3 comprises leaf spring sections 4, two of which are shown in FIG. 3, which are connected to each other by means of a deflection section 5. However, FIG. 3 may also show a part of a coil of a helical spring, for example, in the case where the spring unit 3 is not a leaf spring unit. More generally, FIG. 3 shows a spring section or spring train with at least one coil.

[0070] The spring device 1A comprises a stiffening element 11 which makes it possible to influence the spring stiffness or spring constant k (FIG. 4) of the spring device 1A during operation of the motor vehicle 2 or of the spring device 1A, in other words to increase or decrease it as required. The “spring constant” or “spring stiffness” indicates the ratio of a force F (FIG. 4) acting on the spring device 1A to a deflection a (FIG. 4) of the spring device 1A caused thereby.

[0071] The stiffening element 11 may have any geometry. For example, the stiffening element 11 may be cylinder-shaped or roller-shaped. The stiffening element 11 may be provided, for example, on the deflection section 5. A plurality of stiffening elements 11 may be provided, and such a stiffening element 11 may be associated with each or only selected deflection sections 5.

[0072] The stiffening element 11 or the stiffening elements 11 can either be attached locally to one or individual sections of the spring unit 3, in particular to the deflection sections 5, or can also enclose the entire spring unit 3. The stiffening element 11 may be inserted or glued into the deflection section 5. In case the spring unit 3 is a coil spring, the stiffening element 11 may also be placed between coils of the spring unit 3.

[0073] With the aid of a control apparatus 12, the stiffening element 11 can be controlled in such a way that it specifically changes its properties in such a way that the spring constant k, the spring travel, the extension or the like of the spring device 1A are influenced. In other words, the properties of the spring device 1A are selectively influenced. This can be done locally, for example at only one of the deflection sections 5, or at the entire spring unit 3.

[0074] In order to influence the properties of the spring device 1A, a signal, in particular an electrical signal, is applied to the stiffening element 11, for example. In the event that several stiffening elements 11 are provided, these can be controlled individually or jointly. In this context, the “properties” of the stiffening element 11 may be understood, for example, as its geometric extension, for example a diameter, a length, a thickness, a width or the like, or its geometric shape, for example circular, oval or polygonal.

[0075] However, the “properties” of the stiffening element 11 may also be understood to mean material properties such as, for example, hardness, viscosity, stiffness, modulus of elasticity or the like. The control apparatus 12 may also be used to influence any combination of the aforementioned properties of the stiffening element 11. For example, the stiffening element 11 can be controlled by means of the control apparatus 12 in such a way that the stiffening element 11 stiffens and/or deforms at least locally.

[0076] In particular, the stiffening element 11 exhibits electrorheological or magnetorheological properties. In other words, the aforementioned properties of the stiffening element 11 that modify the spring constant k of the spring device 1A can be influenced by the application of an electric or magnetic field or by a direct energization of the stiffening element 11, respectively.

[0077] The stiffening element 11 may be made of individual materials or of a combination of different materials which, for example, only partially change their properties within an electric or magnetic field. The stiffening element 11 is made of an elastomer or of a composite material comprising an elastomer. For example, the stiffening element 11 may be made of a magnetorheological elastomer or comprise a magnetorheological elastomer.

[0078] Magnetorheological elastomers comprise an elastomer matrix and magnetically active particles dispersed therein. In such magnetorheological elastomers, the viscoelastic or dynamic mechanical properties can be rapidly and reversibly changed by applying an external magnetic field. The stiffening element 11 may also comprise an electrorheological fluid, elastomer or the like.

[0079] In the simplest case, the control apparatus 12 is an electric circuit 13 with a voltage source 14. The control apparatus 12 and the stiffening element 11 together form a stiffness adjusting unit 15 of the spring device 1A. The stiffening element 11 is part of the electric circuit 13. For example, in the view of FIG. 3, the voltage source 14 does not supply any voltage and the stiffening element 11 is in a deactivated state Z1.

[0080] In the deactivated state Z1, the stiffening element 11 is, for example, many times less stiff than the spring unit 3, so that deformation of the spring unit 3 by the stiffening element 11 is not hindered. The result is the curve of the spring constant k of the spring device 1A shown in FIG. 4. This curve of the spring constant k according to FIG. 4 essentially corresponds to the curve of a spring device not shown without such a stiffness adjusting unit 15.

[0081] When a voltage is applied to the stiffening element 11, as shown in FIG. 5, the stiffening element 11 is moved from the deactivated state Z1 to an activated state Z2. The states Z1, Z2 are shown with different hatchings in FIGS. 3 and 5. For example, the stiffening element 11 has a different geometry in the activated state Z2 than in the deactivated state Z1. Further, the modulus of elasticity of the stiffening element 11 may change when the same is moved from the deactivated state Z1 to the activated state Z2.

[0082] To stay with the previous example, in the activated state Z2 the stiffening element 11 may be many times stiffer than the spring unit 3, so that in the activated state Z2 the stiffening element 11 impedes the deformation of the spring unit 3 in such a way that, as shown in FIG. 6, compared to the deactivated state Z1, a steeper curve of the spring constant k′ of the spring device 1A results. That is, a smaller deflection a of the spring device 1A can be obtained with the same force F. The spring device 1A is therefore harder in the activated state Z2 than in the deactivated state Z1.

[0083] In this case, the stiffness adjusting unit 15 can be designed in such a way that the course of the spring constant k′ becomes increasingly steeper the higher the tension applied to the stiffening element 11. The spring constant k can thus be varied continuously. An infinite number of intermediate states can be provided between the deactivated state Z1 and the activated state Z2.

[0084] However, the control apparatus 12 may also be adapted to generate an electric field E or a magnetic field M for driving the stiffening element 11. In the activated state Z2, the stiffening element 11 is arranged, at least in sections, within the electric field E or the magnetic field M. It is thus possible to control the stiffening element 11 in a contactless or non-contacting manner. For generating the fields E, M, the control apparatus 12 may comprise a coil which can be energized. The coil may enclose the stiffening element 11 at least in sections. However, this is not mandatory.

[0085] FIG. 7 shows a schematic view of a further embodiment of a spring device 1B, which is also suitable for the motor vehicle 2. In the following, only differences between the spring devices 1A, 1B will be discussed. The spring device 1B comprises a spring unit 3, which is a leaf spring unit as previously explained with leaf spring sections 4 and deflection sections 5 arranged between the leaf spring sections 4. The deformation of the leaf spring sections 4 takes place substantially in regions 6. The spring unit 3 is made of a fiber composite plastic.

[0086] In contrast to the spring device 1A, the spring device 1B comprises a spring unit 3 with a progressive characteristic curve. For this purpose, the spring unit 3 comprises a first or soft spring section 16 with a first spring constant k1 and a second or hard spring section 17 with a second spring constant k2. The second spring constant k2 is greater than the first spring constant k1. This difference in spring constants k1, k2 may be achieved, for example, by the hard spring section 17 having a larger cross-sectional area and/or a different geometry than the soft spring section 16. With respect to the direction of gravity g, the soft spring section 16 is placed above the hard spring section 17. The spring sections 16, 17 are connected to each other integrally, in particular integrally made of one material.

[0087] When a load is applied to the spring device 1B, the soft spring section 16 now flexes in first. The hard spring section 17 only compresses when the soft spring section 16 is almost or almost completely compressed. As shown in FIG. 8, this results in a progressive course of the spring constant k of the spring device 1B.

[0088] The spring device 1B comprises a stiffness adjusting unit 15 as previously mentioned, including a control apparatus 12 and a stiffening element 11. The stiffening element 11 is preferably provided at the soft spring section 16. Thereby, as explained with reference to FIGS. 3 and 5, the stiffening element 11 may be provided only at the deflection section 5 or only at the deflection sections 5. However, the stiffening element 11 may also envelop or wrap the entire soft spring section 16, as shown in FIGS. 7 and 9.

[0089] For example, the stiffening element 11 is materially bonded to the soft spring section 16. In the case of materially bonded connections, the connecting partners are held together by atomic or molecular forces. Materially bonded connections are non-detachable connections which can only be separated by destroying the connecting means and/or the connecting partners. Materially bonded joints can, for example, be joined by adhesive bonding or vulcanization. For example, the stiffening element 11 is molded to the soft spring section 16.

[0090] The stiffening element 11 has electrorheological or magnetorheological properties, as previously mentioned. By means of the control apparatus 12, the stiffening element 11 can be brought from a deactivated state Z1 (FIG. 7) to an activated state Z2 (FIG. 9) and vice versa. This can be done, for example, by energizing the stiffening element 11 or by applying an electric field E (FIG. 9) or a magnetic field M thereto. The different states Z1, Z2 are shown in FIGS. 7 and 9 with differently oriented hatchings.

[0091] In the activated state Z2, the stiffening element 11 deactivates the soft spring section 16 such that substantially only the hard spring section 17 compresses when the spring device 1B is loaded. The soft spring section 16 is frozen and ideally does not contribute anything to the spring action of the spring device 1B. As shown in FIG. 10, this results in a linear variation of the spring constant k′. The spring constant k′ then substantially corresponds to the second spring constant k2. In addition, stiffening elements 11 can also be provided on the hard spring section 17.

[0092] With the aid of the stiffness adjusting unit 15, it is thus possible to quickly change the spring constant k, for example, in order to actively adjust or control the spring deflection and the spring constant k of the spring device 1A, 1B in real time. It is possible to compensate for height, for example in the event of a change in load, and to shift the natural frequency of the spring device 1A, 1B into a non-critical range. A wheel-, side- and/or axle-specific change of the spring constant k can be carried out, for example during cornering, for roll stabilization, during acceleration, during braking and/or within the scope of electronic compensation systems or so-called body control systems.

[0093] With the help of the continuous change of the spring constant k, both ride comfort and driving dynamics can be improved. This can also be achieved without the use of a progressive suspension (not shown), whose spring constant is dependent on the spring deflection. By making the spring constant k adjustable, damper functions can be supported. The spring device 1A, 1B can at least partially replace other, partly active, chassis components, such as a roll stabilizer, dampers, air springs or the like, or at least a smaller dimensioning of these chassis components is possible within the scope of downsizing. It is possible to implement a highly dynamically switchable spring device 1A, 1B. Compared to active air springs, the spring device 1A, 1B is a simple, cost-effective and, in terms of dynamic usability, higher-performance solution.

[0094] Although the present invention has been described with reference to examples of embodiments, it can be modified in a variety of ways.

LIST OF REFERENCE SIGNS

[0095] 1A Spring device [0096] 1B Spring device [0097] 2 Motor vehicle [0098] 3 Spring unit [0099] 4 Leaf spring section [0100] 5 Deflection section [0101] 6 Region [0102] 7 End section [0103] 8 Bearing unit [0104] 9 End section [0105] 10 Bearing unit [0106] 11 Stiffening element [0107] 12 Control apparatus [0108] 13 Electric circuit [0109] 14 Voltage source [0110] 15 Stiffness adjusting unit [0111] 16 Spring section [0112] 17 Spring section [0113] a Deflection [0114] E Electric field [0115] F Force [0116] g Direction of gravity [0117] k Spring constant [0118] k′ Spring constant [0119] k1 Spring constant [0120] k2 Spring constant [0121] M Magnetic field [0122] Z1 State [0123] Z2 State