Patent Application
20240270042
The present invention relates to a tubular anti-roll bar for a vehicle chassis and a vehicle chassis comprising the tubular anti-roll bar.
Tubular anti-roll bars made from formed steel tube are known in multiple forms in the prior art. Tubular anti-roll bars are also referred to as torsion bars, stabilization torsion bars or torsion spring bars. Steel springs and tubular anti-roll bars are used, in particular, in motor vehicles, wherein steel springs are used, for example, in spring/damping systems for absorbing shocks caused by uneven road surfaces and tubular anti-roll bars are used for stabilizing against rolling when cornering in a motor vehicle, when driving a motor vehicle over varying road surfaces and in the case of uneven road surfaces. Such anti-roll bars are conventionally arranged in the region of the front and the rear axle and usually extend over the entire width of the vehicle. Forming the steel tube or steel wire into springs and torsion bars may take place according to forming procedures known in the prior art. Before or after this forming, the steel tube or the steel wire may undergo various preparatory steps, which influence the spring properties and strength properties and improve certain other usage properties of a material. In this regard, higher-strength spring and/or torsion bars can be produced with comparatively low material usage and therefore with a low weight and low material costs. In this case, tubular springs have a relatively low weight compared to bar springs, with the same spring properties; the stiffness and flexural strength in tubular anti-roll bars depends on the diameter and the wall thickness. However, increasing the diameter-wall thickness ratio to further save on weight is only possible to a limited extent owing to the higher internal stresses arising during the forming process and during operation of the component. The properties of tubular anti-roll bars are therefore limited to a narrow range of geometrical dimensions and the resultant spring properties and the formability of the steel tube or steel wire is limited in several forming procedures known in the prior art. In particular, the parameters “strength” and “durability” are related to the forming capability and the service life of a tubular anti-roll bar.
The object of the present invention, therefore, is to provide an improved tubular anti-roll bar for vehicles and/or an improved vehicle chassis comprising a tubular anti-roll bar, in which the above-mentioned disadvantages are avoided. In particular, with this improved tubular anti-roll bar for vehicles and/or with the improved vehicle chassis, the aim is to enable an increase in the service life, in particular in the service-life values in dynamic tests, and to reduce the variation in service-life results.
This object is achieved by a tubular anti-roll bar as claimed in claim 1 and a vehicle chassis as claimed in claim 7.
The tubular anti-roll bar according to the invention for a vehicle chassis has the advantage of a longer service life compared to conventional tubular anti-roll bars. Moreover, in the case of the tubular anti-roll bar according to the invention, it is possible to establish properties, in particular the stiffness and flexural strength, based on requirements.
The subject matter of the invention is, therefore, a tubular anti-roll bar for a vehicle chassis, produced from a metal tubular body, comprising a torsion spring portion, two limbs bent off from the torsion spring portion and a bending portion, arranged between the torsion spring portion and the respective bent limb and having an inside bending radius and an outside bending radius, wherein the tubular anti-roll bar has a structure, in particular a steel structure, for example an iron-carbon alloy, for example a microstructure with grains, in particular a granular structure with a grain size distribution and an average grain size, in particular an average value of the grain size distribution, wherein the structure has a ratio between the average grain size, in particular after tempering, in the bending portion of the inside bending radius, in particular in the vertex of the bending portion of the inside bending radius, in relation to the average grain size in the torsion spring portion, in particular in the center of the torsion spring portion, in the range of 70% to 99% or 70% to 90%, preferably in the range of 71% to 79%, particularly preferably in the range of 72% to 78%, especially preferably in the range of 73% to 77%.
A further subject matter of the invention is a vehicle chassis, comprising a tubular anti-roll bar for a vehicle chassis, produced from a metal tubular body, comprising a torsion spring portion, two limbs bent off from the torsion spring portion and a bending portion, arranged between the torsion spring portion and the respective bent limb and having an inside bending radius and an outside bending radius, wherein the tubular anti-roll bar has a structure, in particular a steel structure for example an iron-carbon alloy, for example a microstructure with grains, in particular a granular structure with a grain size distribution and an average grain size, in particular an average value of the grain size distribution, wherein the structure has a ratio between the average grain size, in particular after tempering, in the bending portion of the inside bending radius, in particular in the vertex of the bending portion of the inside bending radius, in relation to the average grain size in the torsion spring portion, in particular in the center of the torsion spring portion, in the range of 70% to 99% or 70% to 90%, preferably in the range of 71% to 79%, particularly preferably in the range of 72% to 78%, especially preferably in the range of 73% to 77%.
A further subject matter of the invention is the use of a tubular anti-roll bar for a vehicle chassis, produced from a metal tubular body, comprising a torsion spring portion, two limbs bent off from the torsion spring portion and a bending portion, arranged between the torsion spring portion and the respective bent limb and having an inside bending radius and an outside bending radius, wherein the tubular anti-roll bar has a structure, in particular a steel structure, for example an iron-carbon alloy, for example a microstructure with grains, in particular a granular structure, with a grain size distribution and an average grain size, in particular an average value of the grain size distribution, wherein the structure has a ratio between the average grain size, in particular after tempering, in the bending portion of the inside bending radius, in particular in the vertex of the bending portion of the inside bending radius, in relation to the average grain size in the torsion spring portion, in particular in the center of the torsion spring portion, in the range of 70% to 99% or 70% to 90%, preferably in the range of 71% to 79%, particularly preferably in the range of 72% to 78%, especially preferably in the range of 73% to 77%, for arrangement on a vehicle chassis.
The invention may be realized in a tubular anti-roll bar of a vehicle chassis comprising a tubular anti-roll bar and by the use of a tubular anti-roll bar for arrangement on a vehicle chassis.
Within the context of the present invention, a tubular anti-roll bar is understood to be a component comprising at least one metal tubular element, in which, when firmly clamped at both ends, the fastened ends execute a pivotal movement with respect to each other about the tubular anti-roll bar axis. In particular, the mechanical strain is essentially produced by a torque acting tangentially to the tubular anti-roll bar axis. Tubular anti-roll bars are also understood to include, for example, an angled torsion bar, a torsion spring, a torsion bar spring or a combination of these.
In a further embodiment of the invention, the metal tubular body comprises a manganese-boron-steel composite with a carbon content in the range of 0.2% by weight to 0.42% by weight in relation to the total weight of the manganese-boron-steel composite, preferably in the range of 0.24% by weight to 0.4% by weight in relation to the total weight of the metal tubular body, in particular the manganese-boron-steel composite. By way of example, the metal tubular body, in particular the manganese-boron-steel composite, is selected from a group of boron-alloyed tempered steels according to DIN EN 10083, for example 20MnB5, 26MnB5, 34MnB5, 40MnB5.
According to a further embodiment of the invention, the average grain size, in particular after tempering, in the bending portion is greater in the outside bending radius than in the inside bending radius. In particular, the structure has a ratio between the average grain size (in particular after tempering) in the bending portion of the outside bending radius (OB) (in particular in the vertex of the bending portion of the outside bending radius (OB)) in relation to the average grain size in the torsion spring portion (2) (in particular in the center of the torsion spring portion) in the range of 78% to 105%, preferably in the range of 80% to 102%, particularly preferably in the range of 83% to 100%, especially preferably in the range of 85% to 98%.
According to a further embodiment of the invention, the bending portion has a bending angle between the torsion spring portion and the respective bent limb in the range of 30° to 105°, preferably in the range of 35° to 95°, particularly preferably in the range of 45° to 90°. Within the context of the present invention, a bending angle is understood to be the path, in particular the measured path, covered by the positionally altered limb of the profile during bending. It is the angle between the originally extended position of the inside edge of the limb and its end position.
In a further embodiment of the invention, the tubular anti-roll bar is tempered by electrical resistance heating; in particular the torsion spring portion, the two limbs bent off from the torsion spring portion and the bending portion arranged between the torsion spring portion and the respective bent limb are tempered at the same time, in particular tempered in one process step. According to a further embodiment of the invention, the structure of the tubular anti-roll bar in part comprises a martensitic structure; in particular, the bending portion comprises a martensitic texture; for example the bending portion is made from a martensitic structure.
The tubular anti-roll bar according to the invention is explained with the aid of the drawings.
In
A longitudinal section through a bending portion 4, 4′ of the tubular anti-roll bar 1 is shown in a schematic representation in
In
In
Sampling took place in the first limb radius of the left side. To this end, two tubular anti-roll bars were provided for each resistance heating method. Therefore, a transverse ground section and a longitudinal ground section could be removed in each case. As reference, a transverse ground section was moreover removed in the neutral back region. The sampling/sample preparation is described in note form below:
A martensitic structure is present in the tempered tubular anti-roll bars, and it is therefore advisable to subject the polished samples to heat treatment. This is intended to oxidize the grain boundaries and facilitate etching of the grain boundaries. Possible furnace settings may be applied as follows:
After the heat treatment, the sample may be quenched directly in water. The polished surface now has an oxide layer which is carefully removed by polishing.
PLEASE NOTE: Complete removal of the oxide layer is advisable !
When generating the grain boundaries, repeated polishing and etching may be necessary. The effective range of oxidation through heat treatment is very superficial and could be evened out by too strong polishing.
Two approved agents may be used for the etching.
After etching, the acid is thoroughly removed from the sample using water. The surface appears copper or black, depending on the etchant. This layer is removed using ethanol and a cotton swab, applying strong pressure. Then, clean with water again, remove the water using ethanol and dry the sample in an air flow.
The sample may now be observed under the microscope. If the result is not yet satisfactory, the polishing and etching are repeated until the grain boundaries are visible.
Suitable magnification should be selected to capture images of the grain boundaries. PLEASE NOTE: In this report, a consistent magnification was selected to enable comparison of the longitudinal ground sections.
If an image is captured with the desired magnification, the grain size is determined using the circular section method of DIN EN ISO 643. This should be established manually depending on the image quality.
Images were captured at 200× magnification at 3 points (c.f.
Images were captured at 500× magnification at 3 points (c.f.
Images were captured at 500× magnification at 3 points in each case (c.f.
Images were captured at 500× magnification at 3 points in each case (c.f.
Images were captured at 500× magnification at 6 points (c.f.
Images were captured at 500× magnification at 6 points (c.f.
From the test results, it is possible to make the following statements:
Tubular anti-roll bars of the above-described type are used in the production of vehicles, in particular the chassis of motor vehicles.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2021 208 073.1 | Jul 2021 | DE | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2022/069820 | 7/14/2022 | WO |
