Vibration damper and torsion profile

Abstract

Vibration damper for an open torsion profile (3) having at least two free legs (5, 5') and a housing (7) having at least two oppositely oriented cylinder bores (8, 8', 8'', 8''') in each of which a piston (9, 9', 9'', 9''') is longitudinally axially movable, characterized in that the pistons (9, 9', 9'', 9''') can be connected at least indirectly to each free leg (5, 5') of the torsion profile (3).

Description

[0001] The present invention relates to a vibration damper for an open torsional profile according to the preamble of claim 1. The invention further relates to a torsional profile according to the preamble of claim 8.

[0002] Such a vibration damper is known, for example, from KR 10 2005 009 59 46 A.

[0003] Such a torsion profile is known, for example, from KR 10 2012 005 91 01 A.

[0004] Particularly in the compact class of passenger cars, so-called torsion beam axles are used as rear axles, as exemplified in... Fig. 1 are shown. Such compound link axles 1 have two leading longitudinal control arms 2, 2', which are connected to each other via a cross member designed as a torsion profile 3, the downwardly open torsion profile 3 additionally serving as a stabilizer. With reference to a vehicle coordinate system, the longitudinal control arms 2, 2' are attached to the vehicle body at the front (in Fig. (1 not shown) are hinged and at the rear are the wheel carriers (in Fig. (1 not shown) including the brake units. The advantages of such a compound link axle 1 compared to other known axles include good lateral stability when cornering and a small footprint, which allows for a more advantageous space allocation in the rear of the car.

[0005] In order for the torsion profile to fulfill its function as a stabilizer, the open torsion profile exhibits relatively low torsional stiffness and a correspondingly low natural frequency. A disadvantage is that the torsion profile can be set into oscillation during braking due to the dry friction of the rear brakes. During this process, the legs of the torsion profile move in opposite directions, producing a low-frequency noise. Due to the similarity of this noise to the bleating of a cow, this low-frequency sound is also known in technical circles as a "mooing noise."

[0006] It has been found that the noises in question occur primarily when switching from forward to reverse driving, because the brake pads are carried along by the backward rotating brake disc and change their contact points on the respective brake carrier. This results in relatively undefined positions of the brake pads during this period, which promotes the occurrence of vibrations.

[0007] Several proposals have already been pursued to prevent the occurrence of such noises, but these have not led to the hoped-for success or have brought other disadvantages.

[0008] Initially, so-called clip-on shims were used, which were stainless steel plates attached to the backing plates of the brake pads. These clip-on shims reduce friction between the pad and the brakes, which can be further reduced by applying grease between the shims and the backing plates. This is intended to ensure that the brake pads quickly assume a defined position when changing direction, thus preventing oscillation caused by the axle's torsional profile.

[0009] A disadvantage is that the installation of the clip-on shim cannot be automated, meaning it often has to be applied manually, which increases assembly costs. Furthermore, greasing is difficult to integrate into existing production facilities and carries the additional risk of the brake pad friction material absorbing oil, which in turn can reduce the friction coefficient of the brake pads.

[0010] Alternatively, it was suggested to stiffen the brake carrier to make it more difficult for vibrations to be transmitted to the axle. However, stiffening the brake carrier increases weight, which contradicts the goal of lightweight vehicle construction and also entails additional costs.

[0011] Finally, so-called "moo dampers" were also proposed, in which a vulcanized and elastically mounted damping mass is bolted to the brake. However, installing such a "moo damper" is also an expensive solution that additionally causes clearance problems during brake manufacturing, axle assembly, and axle installation in the vehicle.

[0012] All the aforementioned attempts to suppress the "moo noises" have the problem that the corresponding additional components must be directly connected to the brake and the applications may need to be reworked or adjusted again if the friction material is changed, which increases maintenance costs.

[0013] The preliminary publications DE 10 2009 043 552 A1 and DE 102 58 023 A1 also do not provide any indications that would allow for the efficient suppression of the “moo” noises.

[0014] It is therefore the object of the present invention to prevent the legs of a torsion profile from oscillating without impairing the profile's torsional properties, which are required from a vehicle dynamics perspective. This also avoids the need for additional applications on the brake and / or the friction material, which would also require replacement, maintenance, and / or adjustment when the friction material needs to be replaced due to wear.

[0015] This problem is solved by the vibration damper according to claim 1. According to the invention, the pistons can be connected, at least indirectly, to each free leg of the torsion profile. By means of the vibration damper according to the invention, the relative movement of the legs of the torsion profile can be damped in such a way that no audible noise is generated by vibration of the torsion profile. At the same time, the torsional properties of the torsion profile are advantageously not affected because the distance between the legs remains essentially constant during torsion of the profile, so that the driving characteristics of the car are maintained. Finally, the vibration damper eliminates the need for additional maintenance work when replacing the brake pads.

[0016] Preferred embodiments of the vibration damper according to the invention are described below and in the dependent claims.

[0017] According to a first advantageous embodiment of the invention, a piston rod is arranged for the indirect connection between each piston and each free leg of the torsion profile. This piston rod has ball ends on both ends for connection to the piston and the free leg. The connection of the piston rods with ball ends enables relative movement between each leg of the torsion profile and a piston. However, in the direction of the piston stroke, the piston rods establish a backlash-free connection between the two parts, thus effectively preventing oscillation of the legs. Alternatively, instead of a connection with ball ends, an elastomer can also be provided, which allows limited movement of the piston rods in all three spatial directions.

[0018] According to an alternative embodiment of the invention, the pistons and connecting rods are each replaced by a hydraulic bellows. In this embodiment, the hydraulic bellows consists of an elastic diaphragm that closes the opening of a cylinder bore. Due to a selectable or adjustable hydraulic overpressure within the closed hydraulic system, all diaphragms bulge outwards so that they are in contact with the legs of the torsion profile, where they can be firmly connected to the legs. Torsional movements of the torsion profile are not affected by this design either, whereas vibration is dampened by the elasticity of the diaphragms, thus also reducing noise generation.

[0019] According to a further preferred embodiment of the invention, the housing is fixedly connectable to the torsion profile, in particular, the housing is fixedly connected to a web of the torsion profile. For fixing the housing to the torsion profile, for example, a bolted connection with a spacer is provided, so that the position / height at which the pistons are connected to the legs of the torsion profile via the ball heads is essentially predeterminable.

[0020] Preferably, the vibration damper according to the invention is a hydraulic vibration damper, and the cylinder bores are preferably hydraulically connected to one another. In a preferred embodiment of the invention, the cylinder bores are additionally connected to a hydraulic accumulator, wherein a throttle, preferably an adjustable throttle, is arranged between the hydraulic accumulator and the cylinder bores. If an adjustable throttle is not required, the connections between the cylinder bores and the accumulator can function as a throttle.

[0021] The hydraulic accumulator advantageously features a preload in the form of a spring, allowing for a selectable overpressure in the hydraulic system by choosing the appropriate compression spring. This prevents gases bound in the hydraulic fluid from escaping and maintains a constant volume within the hydraulic system. Connecting the cylinder bores to the hydraulic accumulator allows the pistons to move independently along their longitudinal axis within the cylinder bores, thus compensating for varying degrees of oscillation in the cylinder legs. The damping strength can be adjusted via the throttle or the variable throttle, enabling the vibration damper to be installed in various torsional profiles, which may exhibit different vibration characteristics and natural frequencies.

[0022] According to a further preferred embodiment of the present invention, the housing has several, preferably four, cylinder bores, two of which are oriented in opposite directions, with all cylinder bores being connected to the hydraulic accumulator. By arranging several parallel cylinder bores, the density of pivot points of the vibration damper on the torsion profile can be increased, whereby, with conventional torsion profiles, four cylinder bores and thus four pistons are sufficient. The common use of the same hydraulic accumulator has the advantage that all cylinder bores are connected to the same throttle or the same adjustable throttle, so that all pistons have identical damping.Alternatively, a vibration damper can be used whose cylinder bores are each closed by an elastic membrane, as described above.

[0023] The problem stated at the outset is additionally solved by the torsion profile according to claim 8. According to the invention, the free legs of the torsion profile are connected to each other via a vibration damper, as described above and in claims 1 to 7.

[0024] Further specific embodiments of the present invention are explained below with reference to the figures. These show: Fig. 1 a schematic representation of a compound link axle (state of the art) and Fig. 2-6 different cross-sectional views of a torsion profile with a vibration damper.

[0025] Fig. Figure 1 shows a compound link axle 1 as known according to the prior art. Such a compound link axle 1 has two longitudinal control arms 2, 2' which are connected to each other by a torsion profile 3. With reference to a vehicle coordinate system (x→,y→,z→) The compound link axle 1 is connected to the vehicle body at the front and to wheel carriers at the rear (both in Fig. (1 not shown) connected. The torsion profile 3 has a web 4 which forms a downwardly open U-shaped, V-shaped or hat-shaped torsion profile with two free legs 5, 5' on both sides.

[0026] Fig. Figure 2 shows the cross-sectional planes AA of the torsion profile 3. Fig. 1. The cross-section clearly shows that the torsion profile 3 has a web 4 and two legs 5, 5', whose opposing vibrations (arrows 21) produce the aforementioned "mooing" sound. To prevent or sufficiently dampen these vibrations, the legs 5, 5' are connected to a vibration damper 6. In the illustrated embodiment, the vibration damper 6 consists of a housing 7, which can be made, for example, of an extruded aluminum profile or of plastic. Two cylindrical bores 8, 8' are provided in the housing 7, with the illustrated embodiment showing a through bore so that the cylindrical bores 8, 8' merge into one another. Pistons 9, 9' are movably mounted in the cylinder bores 8, 8' in the direction of arrow 10 and the pistons 9, 9' are connected to the legs 5, 5' of the torsion profile 3 by piston rods 11, 11'.The piston rods 11, 11' are connected to the pistons 9, 9' and the legs 5, 5' by means of ball heads 12. The housing 7 of the vibration damper 6 is rigidly connected to the torsion profile 3 and, in particular, to the web 4 of the torsion profile 3. In the illustrated embodiment, a bolted connection 13 with a spacer sleeve 14 is provided for this purpose.

[0027] The Fig. Figures 3-6 show the arrangement of the vibration damper 6 within the torsional profile 3 along the cross-sectional planes BB. Fig. Figure 1 illustrates the function and further construction of the vibration damper 6. In the illustrated embodiments, the vibration damper 6 has four pistons 9, 9', 9'', 9''' each, which are movably mounted in cylinder bores 8, 8', 8'', 8'''. The cylinder bores 8 are continuous and extend through the entire housing 7, which is why a hydraulic chamber 15, 15' is formed between each pair of pistons (9, 9'' and 9', 9'''). The hydraulic chambers 15, 15' are hydraulically connected to a hydraulic accumulator 16, which has a predefinable overpressure due to a spring load 17. Between the hydraulic accumulator 16 and the cylinder bores 8, 8', 8'', 8''' or the hydraulic chambers 15, 15' formed therein, an adjustable throttle 18 is arranged, which generates a predefinable hydraulic resistance.

[0028] Fig. Figure 4 shows the situation in which the legs 5, 5' of the torsion profile 3 are deflected outwards from their original position (shown with dashed lines) and thus in the direction of arrow 19. Due to the connection between the legs 5, 5' and the pistons 9, 9', the pistons are pulled out of the housing 7 of the vibration damper 6, and the hydraulic chambers 15, 15' increase in volume. Hydraulic fluid flows in from the hydraulic accumulator 16, passing through the adjustable throttle 18. The narrower the cross-section of the throttle is set, the more the deflection of the free legs 5, 5' is dampened along the direction of arrow 19.

[0029] In Fig. Figure 5 shows the reverse situation, in which the free legs 5, 5' of the torsion profile 3 are deflected inwards along the direction of arrow 20, whereby the pistons 9, 9', 9'', 9''' are pressed into the cylinder bores 8, 8', 8'', 8'''. The hydraulic fluid is supplied to the hydraulic accumulator 16, passing through the adjusting throttle 18, so that the inward movement of the free legs 5, 5' is also dampened. This dampens the vibration of the free legs 5, 5' of the torsion profile 3 to such an extent that no audible noise is produced.

[0030] Fig.Figure 6 shows that the torsional behavior of the torsion profile 3 is not affected by an integrated vibration damper 6, because during torsion the distances between two opposing pistons 9, 9', 9'', 9''' remain essentially unchanged. Therefore, no hydraulic fluid needs to be transferred to or from the hydraulic accumulator 16 via the adjusting throttle 18. Consequently, the torsional movement of the legs 5, 5' or of the torsion profile 3 is not influenced by the vibration damper 6. Reference symbol list 1 compound link axle 2.2' trailing arms 3 Torsion profile 4 Bridge 5.5' thigh 6 vibration dampers 7 cases 8, 8', 8'', 8''' cylinder bores 9, 9', 9'', 9''' pistons 10 Arrow 11 piston rods 12 ball heads 13 bolt connection 14 spacer sleeve 15 Hydraulic chamber 16 hydraulic accumulators 17 Spring load 18 Adjustable throttle 19 Arrow 20 Arrow 21 Arrow

Claims

[1] Vibration damper for an open torsion profile (3) having at least two free legs (5, 5') and a housing (7) having at least two oppositely oriented cylinder bores (8, 8', 8'', 8''') in each of which a piston (9, 9', 9'', 9''') is mounted to be movable longitudinally axially, characterized in that the pistons (9, 9', 9'', 9''') can be connected at least indirectly to each free leg (5, 5') of the torsion profile (3). [2] Vibration damper according to claim 1, characterized by , that for the indirect connection between each piston (9, 9', 9'', 9'''') and each free leg (5, 5') of the torsion profile (3) a piston rod (11) is arranged, which has ball heads (12) on both sides for connection with the piston (9, 9', 9'', 9'''') and the free leg (5, 5'). [3] Vibration damper according to one of claims 1 to 2, characterized by, that the housing (7) can be firmly connected to the bridge (4) of the torsion profile (3). [4] Vibration damper according to any one of claims 1 to 3, characterized by , that the cylinder bores (8, 8', 8'', 8''') are hydraulically connected to each other. [5] Vibration damper according to any one of claims 1 to 4, characterized by , that the cylinder bores (8, 8', 8'', 8''') are connected to a hydraulic accumulator (16), wherein an adjustable throttle (18) is arranged between the hydraulic accumulator (16) and the cylinder bores (8, 8', 8'', 8'''). [6] Vibration damper according to claim 5, characterized by , that the hydraulic accumulator (16) has a preload so that a selectable overpressure can be set in the hydraulic system. [7] Vibration damper according to any one of claims 1 to 6, characterized by, that the housing (7) has four cylinder bores (8, 8', 8'', 8'''') of which two cylinder bores (8, 8''''; 8', 8'''') are oriented in opposite directions, with all cylinder bores (8, 8', 8'', 8''') being connected to the hydraulic accumulator (16). [8] Torsion profile with a web (4) and two free legs (5, 5') which connects two longitudinal arms (2, 2') of a compound link axle (1) as a cross member, characterized by , that the free legs (5, 5') of the torsion profile (3) are connected to each other via a vibration damper (6) according to one of claims 1 to 7.

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