In the drawings:
FIG. 1 is a schematic illustration of a wheel suspension arrangement,
FIG. 2 is a schematic illustration of a wheel suspension arrangement as per FIG. 1 with a device according to the invention,
FIG. 3 is a schematic illustration of a wheel suspension arrangement as per FIG. 1 with a second embodiment of a device according to the invention,
FIG. 4 is a schematic illustration of a wheel suspension arrangement as per FIG. 1 with a third embodiment of a device according to the invention,
FIG. 5 is a schematic illustration of an assembly with a coupling element in a side view,
FIG. 6 is a schematic illustration of a wheel suspension arrangement as per FIG. 1 with a fourth embodiment of a device according to the invention, and
FIG. 7 is a schematic illustration of a wheel suspension arrangement as per FIG. 1 with a fifth embodiment of a device according to the invention.
Identical components in FIGS. 1 to 7 are denoted in the following with identical reference symbols.
FIG. 1 schematically illustrates a left-hand front wheel suspension arrangement which comprises a wheel carrier 1 on which a wheel 2 is mounted. For clarity, only the left-hand wheel suspension arrangement is shown; the wheel suspension arrangement on the right-hand side is of correspondingly mirror-symmetrical design. Between the wheel carrier 1 and a structure 3, an upper and a lower transverse link 4, 5 are connected to the link mounts 23. The structure comprises an integral support 6 which is connected to a body 7 in an immoveable manner. The upper and lower transverse links 4, 5 are in each case connected to the structure 3 and to the wheel carrier 1 in an articulated manner. An assembly 8, which comprises an internal combustion engine 24 with an associated bracket 17, is mounted on the integral support 6. The internal combustion engine 24 is supported by means of the bracket 17 on an engine mount 9 which conventionally has only a small damping component. However, it is possible by using hydraulically damped engine mounts 9 to adjust the damping component according to demand. A spring 10 and a damper element 11 are arranged between the lower transverse link 4 and the body 7. The damper element 11 is connected to the body 7 by means of a head mounting 12. In the same way, it is also possible for a spring-and-damper strut to be arranged between the link 4 and the body 7. The spring 10 can be embodied, for example, as an air spring or a steel spring.
The wheel 2′ which is compressed as it travels over an uneven underlying surface is represented by a dotted line. In the same way, the upper and lower links 4′, 5′ are also deflected as a result of the compression of the wheel. However, the uneven underlying surface is not completely absorbed by the wheel suspension arrangement, but rather the body 7′ and the integral support 6′ are proportionately raised. This is the case in the low-frequency range of structure vibration. In addition, the exertion of an impulse into the body 7 results in a vibration of the drive unit 8 at its natural frequency. The impulse is transmitted to the body 7 and the structure 3 primarily via the damper element. As a result of the high inertial mass of the assembly 8 and the resilient mounting relative to the integral support 6, the assembly 8 is displaced relative to the integral support 6, with the engine mount 9 compressing and the spacing between the assembly 8 and the integral support 6 being reduced from a to a′. For better clarity, the spring 10 and the damper element 11 are not shown in the compressed state.
As a result of the deflection of the assembly 8, the latter is stimulated to vibrate. Said vibrations, also referred to as juddering, of the assembly 8 are transmitted to the vehicle occupants, considerably reducing driving comfort.
FIG. 2 illustrates the wheel suspension arrangement from FIG. 1 expanded to include a coupling element 13 which is embodied as a vibration damper. The coupling element 13 is connected to the lower transverse link 4 and the bracket 17 in an articulated fashion at the linkage points 15. The linkage points 15 can be embodied, for example, as a ball-and-socket joint and/or as eye joints mounted in rubber. The mode of operation of the coupling element 13 is described in the following during wheel compression; the process takes place in a similar fashion in the reverse order as the wheel rebounds. The integral support which, as described above, is raised as the wheel is compressed, is denoted by 6′. The lower transverse link as deflected when the wheel is compressed is denoted by 4′. The coupling element 13 is supported on the assembly 8 and on the lower transverse link 4′ and is therefore subjected to compressive loading. As the wheel 2 is compressed, a force 14 acts on the assembly 8 via the coupling element, which force 14 reduces the compression of the engine mount 9. The assembly as displaced upwards as the wheel 2 is compressed is denoted by 8′. The spacing a between the assembly 8, 8′ and the integral support 6, 6′ is therefore a substantially constant variable. By suitably selecting the linkage points 15 and their degrees of elasticity and the damping characteristic curve of the coupling element 13, which if required have different tension and compression stages, it is possible to adapt said force 14 in such a way that a stimulus for the assembly 8 to vibrate does not occur or occurs to only a small extent.
The faster the wheel 2 is compressed, the faster the integral support 6 is raised and the higher the inertial force of the assembly 8 which acts on the engine mount 9. However, as a result of the vibration damper characteristic curve, the force exerted by the coupling element 13 on the assembly 8 also increases with the speed of compression of the wheel 2. At the same time, the impulse exerted into the structure 3 via the damper element 11 has an effect as the speed of compression of the wheel 2 increases. As a result of the coupling element 13 being connected to the lower transverse link 4 and the bracket 17 at the linkage points 15, however, a further impulse is exerted on the assembly 8 which reduces the effect of the impulse exerted by the damper element 11 on the assembly 8. The spacing of the assembly 8 to the integral support 6 can therefore be kept largely constant at all speeds of compression of the wheel. This also relieves the engine mount 9 of load and reduces a compression of the wheel, effectively avoiding a stimulus for the assembly 8 to vibrate.
Any compression of the wheel causes a stroke movement of the coupling element 13 and therefore a force which acts on the assembly 8. Relative movements between the assembly 8 and the body 7 or the integral support 6 cannot, however, be avoided in all operating states of a vehicle. Said relative movements are damped by the coupling element 13 embodied as a vibration damper. The damping work of the engine mount 9 is therefore advantageously assisted by the coupling element 13.
It is of course also possible in the same way to avoid a stimulus for the assembly 8 to vibrate as the wheel 2 rebounds.
FIG. 3 illustrates a modified embodiment of the device according to the invention. The coupling element 13 is arranged between the upper transverse link 5 and the assembly 8. In contrast to FIG. 2, the coupling element 13 is subjected to tensile loading as the wheel 2 compresses. The compression of the engine mount 9 is avoided in that the coupling element 13 exerts a force 14 on the assembly 8 which counteracts an inertial force. Said force seeks to maintain a constant spacing a between the assembly 8 and the integral support 6 as the wheel 2 compresses and rebounds.
FIG. 4 illustrates a device according to the invention with a chassis auxiliary frame axle. The chassis auxiliary frame 14 is mounted on the body by means of resilient chassis auxiliary frame mounts 16. On the chassis auxiliary frame 14 itself, the assembly 8 or the internal combustion engine 24 is mounted on brackets 17 by means of engine mounts 9. The lower transverse link 4 is connected to the chassis auxiliary frame 15 in an articulated fashion, and the upper transverse link is connected to the body 7. The coupling element 13 is arranged between the assembly 8 and the lower transverse link 4. The wheel which is raised as it is compressed is denoted by 2′, and the chassis auxiliary frame which is raised simultaneously is denoted by 14′. A compression of the engine mount 9 as a result of the high inertia of the assembly 8 is avoided by the coupling element 13. The coupling element exerts a force on the assembly 8, so that the latter is displaced into the position of the assembly 8′. The coupling element 13 keeps the spacing a between the assembly 8, 8′ and the chassis auxiliary frame 14, 14′ substantially constant. A stimulus for the assembly 8 to vibrate as the wheel 2 compresses and rebounds is thereby effectively counteracted.
FIG. 5 illustrates an assembly 8, which comprises an internal combustion engine 24 and a transmission 18, in a side view. The centers of gravity 19, 20 of the internal combustion engine 24 and of the transmission 18 determine a summed center of gravity 21 of the assembly 8. An engine mount 9 is arranged between the bracket 17, which is connected to the internal combustion engine 24, and the integral support 6 or chassis auxiliary frame 16. The lower transverse link 4 is rotatably mounted in the link mounts 23, and is connected to the bracket 17 by means of the coupling element 13. The central axis of the coupling element 13 is aligned so as to run through the summed center of gravity 21. During movements of the lower transverse link 4, the coupling element 13 transmits a force to the assembly 8. As a result of said force, or an impetus, acting on the summed center of gravity 21, no torque or rotational impulse is generated which would additionally load the mount such as for example a transmission mount 22. In connection with the reduced tendency to judder as a result of the coupling element 13, said arrangement also makes it possible to design the transmission mount 22 to be soft, so as to ensure good noise decoupling.
In the embodiment illustrated in FIG. 6, the coupling between the link 4 and the assembly 8 is of hydraulic design. A hydraulic master unit 25 which comprises a piston and a cylinder is arranged between the link 4 and the integral support 6, and a hydraulic slave unit 26, which likewise comprises a piston and a cylinder, is arranged between the assembly 8 and the integral support 6. The master and slave units 25, 26 are connected to one another by means of hydraulic lines 28a, b. A gas spring 27 is connected into the hydraulic line 28a which gas spring 27 acts with a constant pressure on the hydraulic fluid situated in the circuit. A gap through which hydraulic fluid can flow is provided between the piston and the cylinder of the master and/or slave units 25, 26. As a wheel compresses, the master unit 26 is shortened, and the hydraulic fluid which is compressed in the master unit 25 is at least partially displaced into the slave unit 26 depending on the gap size. The slave unit 26 exerts an impulse on the assembly 8 which, corresponding to the mode of operation in the previous embodiments, reduces juddering of the assembly 8. The coupling system can advantageously be tuned by varying the leakage gap. The slave unit 26 also serves to damp vibrations of the assembly 8. In a simplified embodiment, it is of course possible to dispense with the gas spring 2 and the hydraulic line 28a. Since said embodiment requires only the arrangement of hydraulic lines, which can be positioned as desired, between the assembly 8 and the link 4, the master and slave units 25, 26 can be arranged at a distance from one another without great expenditure without having to take into consideration a corresponding installation space for mechanical connecting elements such as bars, cylinders etc.
FIG. 7 shows an embodiment in which the coupling element is embodied as a bar 29 with a friction head 30. As the wheel 2 compresses into the position of the wheel 2′, the bar 29 moves the friction head 30, which is in frictional contact with the assembly, upward. As a result of the frictional force, an impulse is exerted on the assembly 8 which, corresponding to the mode of operation in the previous embodiments, reduces juddering of the assembly 8.
The above described devices according to the invention also advantageously damp vibrations of the assembly 8 by means of the coupling element 13 embodied as a vibration damper, considerably increasing driving comfort in particular in the case of engine mounts 9 with low damping properties. The use of a vibration damper as a coupling element 13 can therefore also make it possible to save on damping devices in the engine mount 9.
In a modified exemplary embodiment which is not illustrated, the coupling element 13 is arranged such that, as the wheel 2 compresses and rebounds, in addition to a force in the direction of the vertical axis z, a force also acts on the assembly 8 in the direction of the longitudinal axis x. It is thereby possible to avoid longitudinal vibration of the assembly 8 in the direction of the X axis. The force in the direction of the longitudinal axis x can be obtained by means of an arrangement of the coupling element 13 as in FIGS. 2-4, rotated about the transverse axis y. The magnitude of the force acting on the assembly 8 in the direction of the longitudinal axis x can be adjusted by means of the magnitude of the rotational angle.
List of Reference Symbols
1 Wheel carrier
2 Wheel
2′ Compressed wheel
3 Structure
4 Lower transverse link
4′ Deflected lower transverse link
5 Upper transverse link
5′ St Deflected upper transverse link
6 Integral support
6′ Raised integral support
7 Body
7′ Raised body
8 Assembly
8′ Displaced assembly
9 Engine mount
10 Spring
11 Damper element
12 Head mounting
13 Coupling element
14 Chassis auxiliary frame
14′ Raised chassis auxiliary frame
15 Linkage points
16 Chassis auxiliary frame mount
17 Bracket
18 Transmission
19 Center of gravity, internal combustion engine
20 Center of gravity, transmission
21 Summed center of gravity
22 Transmission mount
23 Link mount
24 Internal combustion engine
25 Master unit
26 Slave unit
27 Gas spring
28
a Hydraulic line
28
b Hydraulic line
29 Bar
30 Friction head
Patent Application
20080083591
