Semi-trailing arm for a wheel suspension of a motor vehicle and semi-trailing arm axle

Abstract

The invention relates to a semi-trailing arm (4) for a wheel suspension for rear wheels of motor vehicles, the semi-trailing arm (4) comprising: at least one first bearing area (8) for connecting the semi-trailing arm (4) to a body of a motor vehicle, in particular to at least one longitudinal member or to at least one subframe, at least one second bearing area (10) for connecting the semi-trailing arm (4) to the body of the motor vehicle, in particular to at least one cross member or to at least one subframe, at least one wheel carrier (21) for connecting the semi-trailing arm (4) to a wheel (20), and at least one spring mount (24) for connection to at least one spring strut (14) for supporting the semi-trailing arm (4) on the body of the motor vehicle. The invention also relates to a semi-trailing arm axle (2) for a rear suspension of a motor vehicle.

Description

[0001] HF / HF 241028EP

[0002] 18. Dezember 2025

[0003] Semi-trailing arm for a wheel suspension of a motor vehicle and semi-trailing arm axle

[0004] The invention relates to a semi-trailing arm for a wheel suspension of a motor vehicle, wherein the semi -trailing arm comprises at least one first bearing area for connecting the semi-trailing arm to a body of a motor vehicle, in particular to at least one longitudinal member or to at least one subframe, at least one second bearing area for connecting the semi-trailing arm to the body of the motor vehicle, in particular to at least one cross member or to at least one subframe, at least one wheel carrier for connecting the semi-trailing arm to a wheel, and at least one spring mount for connection to at least one spring strut for supporting the semi-trailing arm on the body of the motor vehicle. The invention also relates to a semi-trailing arm axle, in particular for a rear wheel suspension for rear wheels, of a motor vehicle.

[0005] Electric vehicles of the price-sensitive small car type are usually front-wheel drive. Although rear-wheel drive, which is preferable for reasons of driving dynamics (cornering behavior, steering feel), could be implemented via a multi-link axle, it is usually too expensive for this price-sensitive type of small car. The use of rear-wheel drive twist-beam axles does not play a role in the price-sensitive small car type due to the limited installation space and restricted driving dynamics.

[0006] The drive characteristics of electric vehicles, especially in rear-wheel drive configurations, fundamentally change the dynamic behaviour of the vehicle and place higher demands on the kinematic and elastokinematic design of the chassis.

[0007] Compared to vehicles with conventional combustion engines, electric motors can deliver maximum torque instantly. This characteristic significantly increases the risk of the drive wheels exceeding the adhesion limit of the tires when starting off or accelerating out of a bend. In rear-wheel drive models, this sudden torque istransferred to the rear axle, which is responsible for steering stability. A chassis geometry that is not optimally controlled can easily lead to oversteering or skidding.

[0008] For safety reasons, vehicles in normal road traffic are designed to understeer. A steering design is the self-steering behavior of the entire vehicle, which results from the combined self-steering behavior of the front axle and the self-steering behavior of the rear axle.

[0009] Due to their design, semi-trailing arm rear axles usually have an oversteer effect. This "oversteer" must therefore not only be compensated for during driving by understeering the front axle but must also be superimposed in order to ensure that the entire vehicle understeers as intended.

[0010] In vehicles with front-wheel drive, the drive force supports the advantageous understeering of the wheels of an understeering front axle. In vehicles with rearwheel drive, on the other hand, the drive force reinforces the design-related, disadvantageous oversteering of an oversteering rear axle. In the price-sensitive small car segment, this means that the technological effort is too complex and cost-intensive to design the front axle for understeering in such a way that understeering of the entire vehicle is guaranteed.

[0011] Cost-effective semi-trailing arms or semi-trailing arm suspensions are regularly only used on rear-wheel drive vehicles with high axle loads, especially with maximum permissible axle loads of well over 2000 kg. This is due to the fact that such commercial vehicles only reach moderate speeds and have an inert behavior when accelerating due to their mass, which can reduce the disadvantages of oversteering. On the other hand, a semi-trailing arm axle can be designed to be very robust in everyday use, which makes it suitable for rough use in commercial vehicles.

[0012] On the other hand, the driving dynamics disadvantages of oversteer are a major obstacle to the use of semi-trailing axles in the light compact car segment.

[0013] HF / HF 241028EP 18. Dezember 2025A further innovation in electric vehicles is the change in the overall acoustic environment compared to conventional vehicles with combustion engines. Medium to high-frequency driving noises that were previously imperceptible are now clearly audible. Tire noise caused by the interaction between the tires and the road surface has become a major factor affecting driving comfort.

[0014] Due to their design, conventional bearings of semi-trailing arms do not exhibit any significant flexibility in the direction of the vehicle's vertical axis (Z), which is required for vibration damping to enhance comfort. For this reason, semi-trailing arms are generally not connected directly to the body, but indirectly via a cross member or axle carrier, the bearing areas of which provide vibration isolation. In order to achieve vibration characteristics that enhance comfort, an additional component is therefore required in the current state of the art, which is disadvantageous in terms of cost.

[0015] On this basis, the present invention is based on the task of providing a semi-trailing arm and a semi-trailing arm axle for rear wheels, which enables an understeering and / or vibration-damping suspension for motor vehicles in the small car segment, in particular for motor vehicles in the small car segment with rear-wheel drive.

[0016] According to the invention, the aforementioned task is solved in accordance with a first aspect in the case of an above-mentioned semi-trailing arm in that the at least one first bearing area has at least one first bearing, in particular a first rubber-metal bearing, and the at least one second bearing area has a second bearing, in particular a second rubber-metal bearing.

[0017] Furthermore, it is preferred that a wheel steering axis runs through the intersection of a first pole line of the first bearing and a second pole line of the second bearing.

[0018] Preferably, the wheel steering axis is essentially orthogonal to the plane formed by the first pole line and the second pole line.

[0019] HF / HF 241028EP 18. Dezember 2025It is further preferred, that the first bearing and the second bearing each have at least one area with reduced stiffness and at least one area with increased stiffness in the circumferential direction, and that the first bearing and / or the second bearing each have, in their respective axial directions, at least partially a lowered stiffness relative to the area with increased stiffness in the circumferential direction of the respective bearing.

[0020] This can advantageously enable the formation of specific and different bearing rigidities in the circumferential direction and in the axial direction, thereby providing an advantageous wheel steering axis which, under different load conditions of a wheel connected to the semi-trailing arm, enables desired understeering in terms of driving dynamics and / or exhibits vibration-damping properties.

[0021] The overall movement of a wheel regularly consists of the kinematic movement around an axis of rotation and the respective movements of the body-side bearings, in particular the first bearing and the second bearing, which lead to self-steering behaviour, i.e. a turn around a momentary wheel steering axis.

[0022] The momentary wheel steering axis, also known for example as the virtual wheel steering axis and / or kingpin axis, is preferably an imaginary axis around which the respective wheel can rotate in different deflection and load states and taking into account the wheel guidance geometry. This can result in particular from the design of the semi-trailing arm and is not physically present, but is defined, for example, by the spatial arrangement of the bearing areas, in particular the first bearing area and the second bearing area, as well as the stiffness ratios or the relative degrees of freedom of the first bearing and the second bearing.

[0023] The first bearing and the second bearing preferably have stiffnesses or degrees of freedom in their circumferential and / or axial direction. This means that the first

[0024] HF / HF 241028EP 18. Dezember 2025bearing and the second bearing are elastic and therefore allow limited displacement or compliance in the circumferential and / or axial direction when a force is applied.

[0025] The circumferential direction of the first bearing and the second bearing preferably extends along a plane that is orthogonal to the respective bearing center axis. The respective axial direction of the first bearing and the second bearing preferably extends along the respective bearing center axis.

[0026] The self-steering behavior of the motor vehicle can be described by means of one or more two-dimensional rotating pole definitions.

[0027] The pole line of the first bearing and / or the second bearing is in particular an imaginary line that runs orthogonally to the potential movements of the bearings, wherein the potential movements of the bearings are in particular associated with a deformation and / or load absorption of the first bearing and / or the second bearing. Preferably, the pole lines also run orthogonally to the respective bearing center axis. Accordingly, the pole line of the first bearing is preferably orthogonal to the bearing center axis of the first bearing and the pole line of the second bearing is preferably orthogonal to the bearing center axis of the second bearing. The potential movements of the bearings run in particular in the direction of a resultant, which preferably indicates the potential direction of movement of the respective bearing when a force is applied and preferably extends in the plane which runs in the circumferential direction of the respective bearing and / or orthogonally to the respective bearing center axis. The pole lines preferably also extend in the plane which runs in the circumferential direction of the respective bearing and / or orthogonally to the respective bearing center axis.

[0028] As the two pole lines of the first bearing and the second bearing intersect, a rotating pole can be provided which is particularly advantageous with regard to the selfsteering behavior of the semi-trailing arm.

[0029] HF / HF 241028EP 18. Dezember 2025In automotive engineering, the rotating pole refers to a geometric point around which a wheel or axle currently rotates when the vehicle is moving or steering, particularly with regard to the forces and moments acting in the respective plane of observation.

[0030] It should be noted that the rotating pole determined in a two-dimensional view generally only lies in its projection on the spatially extended wheel steering axis. The two-dimensional view may give the impression that the wheel steering axis is vertical to the viewing plane. However, this is generally not the case. Bearing deformations, for example, can lead to a spatial inclination of the wheel steering axis.

[0031] Simplifying the movement of a wheel guidance system in space using a two-dimensional plane model is a common technical approximation. However, this simplified assumption is no longer valid when analyzing chassis performance with high requirements for precision and stability. In the real world, forces do not act on an abstract plane, but in three-dimensional space, generating corresponding forces and moments.

[0032] The forces acting on the ground, i.e. lateral and braking forces, cause longitudinal and transverse torques to be applied to the wheel suspension, which can cause bearing deformation not only in the XY direction but also in the Z direction. Bearing deformation in the Z direction can enable a pivoting movement of the semi-trailing arm.

[0033] These bearing deformations can also cause unexpected movements of the semitrailing arm, which can negatively interfere with the toe-in effect. The unplanned bearing deformations, especially in the Z direction, can cause the actual position of the wheel steering axis to deviate unexpectedly.

[0034] The present invention uses this finding to enable specifically defined bearing deformations in the circumferential direction and / or in the axial direction, which enable a specific self-steering behaviour. The stiffness of the first bearing and / or the

[0035] HF / HF 241028EP 18. Dezember 2025second bearing in the axial direction and / or in the circumferential direction can contribute to advantageous wheel guidance.

[0036] Steering axis planes can be used in a three-dimensional view to determine the current steering axis. The steering axis plane of the first bearing and the steering axis plane of the second bearing are defined in particular by the respective normals to their radial total directions of movement and the respective bearing center axis. The normals to the radial total directions of movement of the first and second bearings point in particular in the direction of the respective increased stiffnesses in the circumferential direction / in the radial direction of the bearings.

[0037] It is preferred that a momentary wheel steering axis is formed by the intersection of a first steering axis plane of the first bearing and a second steering axis plane of the second bearing.

[0038] The momentary wheel steering axis can be tilted by tilting one or both of the radial total directions of movement, in particular by tilting one or both of the center axes of the bearings in relation to the vertical.

[0039] A momentary wheel steering axis can be provided whose point of intersection with the wheel contact plane lies outside the wheel contact point and / or behind the wheel contact point when viewed in the direction of travel. This can advantageously result in a negative scrub radius and / or a negative caster distance being provided by means of the semi-trailing arm.

[0040] A negative scrub radius can lead to a toe-in correction in the event of a braking force occurring on a wheel connected to the semi-trailing arm. In the case of a wheel connected to the semi-trailing arm, a negative caster distance can lead to a toe-in correction in the event of a lateral force occurring on the wheel on the outside of the bend.

[0041] HF / HF 241028EP 18. Dezember 2025Preferably, the bearing center axis of the outer bearing may be inclined relative to a vertical line. This allows for an advantageous intersection point between the momentary wheel steering axis and a wheel center plane. The wheel center plane is, in particular, a plane extending in the X and Y directions which intersects the wheel center, i.e. the center point of a wheel connected to the semi-trailing arm.

[0042] The driving force acts on the respective wheel at a different height in the Z direction than the braking force and the lateral force. While the braking force and the lateral force act at the wheel contact point, the drive force acts at the wheel center. The aforementioned inclination or tilting of the bearing center axis of the first bearing and / or the bearing center axis of the second bearing can counteract a disadvantageous wheel movement when the drive force is applied. In particular, the aforementioned inclination or tilting of the bearing center axis of the first bearing and / or the bearing center axis of the second bearing can enable opposing lever arms of the wheel steering axis for the braking and driving force, so that a toe-in correction of the wheel connected to the semi-trailing arm can be enabled with both opposing forces.

[0043] For example, the point of intersection of the momentary wheel steering axis with the wheel center plane is offset inwards in the positive Y direction, i.e. towards the center of the vehicle, and in particular is arranged further inwards than the wheel center, so that a positive lever arm, also known as a positive spreading offset, can be made available in the wheel center plane for the drive force acting there. For example, the point of intersection of the momentary wheel steering axis with the wheel contact plane is offset outwards in the negative Y direction and, in particular, further outwards than the wheel contact point, so that a negative lever arm or a negative scrub radius can be provided in the wheel contact plane for the braking force acting there. For example, the point of intersection of the momentary wheel steering axis with the wheel contact plane is offset in the positive X direction to the wheel contact point, i.e. arranged behind the wheel contact point in the direction of travel, so that a negative caster distance can be provided for the lateral force acting there. In

[0044] HF / HF 241028EP 18. Dezember 2025particular, the aforementioned aspects can lead to the wheel connected to the semitrailing arm correcting toe-in in different deflection and load states.

[0045] However, the actual axial directions of movement of the Rubber-metal bearings may deviate slightly from the respective bearing center axes. This may be caused by the above-mentioned torques, which can be generated by the lateral and braking forces acting on the ground. In this case, the outer bearing may deform downwards relative to the vehicle, while the inner bearing may deform upwards relative to the vehicle. Due to the inward and rearward inclination of the outer bearing, the lower end of the bearing center axis may point towards the outside and front of the vehicle. The axial deformation of the bearings can generate additional movement of the semi-trailing arm at the outer bearing towards the outside and front of the vehicle, which can counteract the applied torques and thus stabilise and extend the desired toe correction.

[0046] The semi-trailing arm is designed as a triangular control arm, for example, in which a control arm axis defined by the two bearing areas runs at an angle to the transverse axis of the vehicle and horizontally or slightly inclined to the center of the vehicle. The toe and camber of a wheel are usually defined by the sweep angle α and roof angle β. The sweep angle a can be in the range of 8° to 25°, for example.

[0047] Preferably, the semi-trailing arm and / or the wheel suspension or the semi-trailing arm axle is designed for rear-wheel drive rear wheels. Preferably, the first bearing area is an outer bearing area and the second bearing area is an inner bearing area. Thus, the first bearing is preferably an outer bearing when viewed from the center of the vehicle and the second bearing is an inner bearing when viewed from the center of the vehicle.

[0048] For example, the semi-trailing arm can be designed in one piece or in several pieces. In the case of a multi-piece design, it is preferable that the wheel carrier is essentially

[0049] HF / HF 241028EP 18. Dezember 2025rigidly connected to another part of the semi-trailing arm. Preferably, the semi-trailing arm is designed as a wishbone.

[0050] Preferably, the at least one spring mount of the semi-trailing arm is designed in such a way that the line of action of the spring strut essentially runs through the wheel contact point of a wheel connected to the wheel carrier. The wheel contact point is the point of the wheel that is in contact with a surface, for example the road. This enables further advantageous absorption of the axle load by means of the suspension strut, particularly in the direction of the Z-axis and thus relieving the outer and inner bearing areas of the semi-trailing arm. This can be advantageous for the use of the above-mentioned axial flexibilities of the bearings, in particular to achieve additional mobility of the semi-trailing arm under various load conditions.

[0051] A further preferred embodiment is characterized in that the at least one spring mount has at least one rubber bearing for the articulated connection of the spring strut to the semi-trailing arm. This enables an advantageous connection of one end of the spring strut to the semi-trailing arm. For example, the other end of the suspension strut can be bolted to the body of the vehicle in a hinged manner in a suspension strut dome.

[0052] A further preferred embodiment is characterized in that the first bearing and the second bearing each have at least one region with a reduced stiffness and at least one region with an increased stiffness in the circumferential direction. This advantageously enables the formation of specific and different bearing stiffnesses in the circumferential direction, whereby an advantageous wheel steering axis can be provided, which enables a desired understeer in terms of driving dynamics under different load conditions of a wheel connected to the semi-trailing arm.

[0053] A further preferred embodiment is characterized in that the first bearing and the second bearing have a stiffness ratio of between 1:10 and 1:35 in the circumferential direction, in particular between 1:20 and 1:35.

[0054] HF / HF 241028EP 18. Dezember 2025For example, a stiffness ratio of a bearing in a range of 1:10 means that, when an identical force is applied on the one hand in the direction of extension of the region with increased stiffness and on the other hand in the direction of extension of the region with reduced stiffness, the semi-trailing arm moves by, for example, essentially 1 mm in the direction of extension of the region with increased stiffness and by, for example, essentially 10 mm in the direction of extension of the region with reduced stiffness. A stiffness ratio of a bearing in a range of 1:35 therefore means, for example, that when an identical force is applied on the one hand in the direction of extension of the region with increased stiffness and on the other hand in the direction of extension of the region with reduced stiffness, the semi-trailing arm moves by, for example, essentially 1 mm in the direction of extension of the region with increased stiffness and by, for example, essentially 35 mm in the direction of extension of the region with reduced stiffness.

[0055] A further preferred embodiment is characterized in that a direction of extension of the region with reduced stiffness of the first bearing includes an angle around the bearing center axis of the first bearing with an X-axis, in particular with an X-axis running counter to the direction of travel, of ya between 245° and 265°.

[0056] A further preferred embodiment is characterized in that a direction of extension of the region with reduced stiffness of the second bearing includes an angle around the bearing center axis of the second bearing with an X-axis, in particular with an X-axis running counter to the direction of travel, ofyi between 215° and 225°.

[0057] The aforementioned angular ranges can provide an advantageous wheel steering axis, which enables an advantageous intersection of the wheel steering axis with the wheel contact plane and can thus further improve the toe-in correction of a wheel connected to the semi-trailing arm. In this way, for example, it is possible to implement a desired dynamic understeer under different load conditions of the wheel.

[0058] HF / HF 241028EP 18. Dezember 2025For example, the X-axis runs against the direction of travel of the vehicle and, together with a Y-axis running in the transverse direction and orthogonal to the X-axis, spans a horizontal plane. Preferably, the XY plane corresponds to the plane on which the vehicle is moving. For example, the X and Y axes correspond to the usual understanding of these in a Cartesian coordinate system. For example, a Z-axis is orthogonal to the X and Y axes and corresponds to the usual understanding of a Z-axis in a Cartesian coordinate system. For example, the Z-axis is the axis along which weight forces act due to gravity.

[0059] A further preferred embodiment is characterized in that a bearing center axis of the first bearing has an angle of inclination relative to the vertical in a range between 5° and 25°, wherein the vertical preferably refers to the installation state of the semitrailing arm in the motor vehicle.

[0060] A further preferred embodiment is characterized in that a bearing center axis of the second bearing has an angle of inclination angle relative to the vertical in a range between 0° and 5°, particularly preferably of essentially 0°, wherein the vertical preferably refers to the installation state of the semi-trailing arm in the motor vehicle.

[0061] It has been found that an essentially straight arrangement of the second bearing and an inclination of the first bearing can provide an advantageous wheel steering axis, which preferably enables a desired toe correction for both braking force and driving force.

[0062] In particular, the bearing center axis of the first bearing has an angle of inclination relative to the vertical in a range between -20° and 20°, in particular between -20° and -5° or between 5° and 20°, and / or the bearing center axis of the second bearing has an angle of inclination relative to the vertical in a range between -20° and 20°, in particular in a range between -10° and 10°.

[0063] HF / HF 241028EP 18. Dezember 2025A further preferred embodiment is characterized in that the first bearing and the second bearing each have a lowered stiffness in the axial direction, which has a ratio of between 1:2 and 2:1 to the reduced stiffness in the circumferential direction. This can advantageously enable additional steering movement in the Z direction, which can enable and / or enhance desirable understeer in terms of driving dynamics under different load conditions of a wheel connected to the semi-trailing arm. In addition, these largely vertical flexibilities can advantageously enable vibration isolation that enhances comfort.

[0064] Preferably, the angle of inclination of the bearing center axis of the first bearing and the angle of inclination of the bearing center axis of the second bearing relative to the vertical refers to an angle of inclination of the bearing center axes relative to the Z-axis (acting in the direction of gravity). The vertical preferably extends in the direction of the Z-axis. Preferably, the essentially vertical course of the bearing center axes of the first bearing and the second bearing relates to the installation state of the semitrailing arm in the motor vehicle.

[0065] A further preferred embodiment is characterized in that the bearing center axis of the first bearing and the bearing center axis of the second bearing are inclined relative to each other. This means in particular that the distance between the two bearing center axes decreases in the positive Z-direction, i.e. upwards in the installation state of the semi-trailing arm. This can be advantageous with regard to the driving dynamics properties of the semi-trailing arm.

[0066] A further preferred embodiment is characterized in that the first rubber-metal bearing and / or the second rubber-metal bearing has at least one essentially elastomeric inner part and at least one outer part, in particular a sleeve-shaped outer part, which surrounds the elastomeric inner part at least in sections. Such a design can advantageously enable different radial stiffnesses or a stiffness distribution of the rubber-metal bearings in the circumferential direction. Additionally, this can lower the axial stiffness of the Rubber-metal bearing.

[0067] HF / HF 241028EP 18. Dezember 2025For example, the inner part has at least one radial web and at least one pocket. The at least one radial web can extend essentially along the entire inner diameter of a sleeveshaped outer part, thereby providing increased stiffness of the rubber-metal bearing in the direction in which the radial web extends. The at least one pocket is designed, for example, as a recess formed in the elastomeric inner part, whereby a reduced stiffness of the rubber-metal bearing is made possible in the direction in which the at least one pocket extends. The pocket itself can, for example, be formed as an air-filled space inside the sleeve-shaped outer part.

[0068] A further preferred embodiment is characterized in that the first rubber-metal bearing and / or the second rubber-metal bearing has at least one radial web and at least two pockets arranged essentially orthogonally to the at least one radial web, and / or in that the stiffness ratio of the first rubber-metal bearing and / or the second rubber-metal bearing in the direction of extension of the at least one radial web relative to the direction of extension of the at least two pockets is preferably in a range from 1:10 to 1:35.

[0069] The directions of extension of the at least one radial web and the at least two pockets preferably span a plane that essentially corresponds to the circumferential direction described above. Preferably, the direction of extension of the at least one radial web, the direction of extension of the at least two pockets and the central axis of the respective rubber-metal bearing are orthogonal to each other. By providing rubbermetal bearings with the aforementioned stiffness ratio, a preferred wheel steering axis can be realized, which in particular implements a desired dynamic understeer under different load conditions of the wheel.

[0070] For example, different stiffness ratios lead to different degrees of freedom of the at least one rubber-metal bearing. For example, the rubber-metal bearings have different degrees of freedom in the circumferential direction. The relative displacements of the bearings can be regarded as degrees of freedom, for example. In particular, the

[0071] HF / HF 241028EP 18. Dezember 2025rubber-metal bearings have a greater degree of freedom in the direction of extension of the pocket(s) than in the direction of extension of the at least one radial web.

[0072] A further preferred embodiment is characterized in that the first rubber-metal bearing and / or the second rubber-metal bearing has at least one metallic sleeve as an outer part. By means of at least one metallic sleeve, a sleeve for the elastomeric inner part of the rubber-metal bearing can be provided in a structurally favorable manner, whereby a rubber-metal bearing with different radial stiffnesses is provided in a manufacturing-favorable manner.

[0073] A further preferred embodiment is characterized in that the at least one spring mount is designed in such a way that a ratio between a distance between the arm axis and the spring mount and a distance between the arm axis and a wheel center of a wheel connected to the semi -trailing arm is at least 0.9 and / or that the ratio between the bearing distance of the first bearing to the second bearing and the spring distance of the spring mount to a wheel center, with said spring distance being parallel projected to the bearing distance, is at least 3.0. Preferably, the minimum distances of the spring mount to the arm axis and the wheel center to the arm axis are used as the basis for forming the ratio.

[0074] The parallel projected spring distance is preferably orthogonal to the distance between the control arm axis and the spring mount and / or orthogonal to the distance between the control arm axis and the wheel center of the wheel connected to the semi-trailing arm.

[0075] As the suspension strut is connected or mounted close to the wheel, it can absorb a very large proportion of the axle load in the direction of the Z-axis or in the vertical direction. This can advantageously reduce the axle load absorbed by the first and second bearing areas and by the first and second bearings, particularly in the vertical direction or in the direction of the Z-axis.

[0076] HF / HF 241028EP 18. Dezember 2025According to a second aspect of the invention, the aforementioned task is solved by a semi-trailing arm axle comprising: at least two semi -trailing arms, in particular at least two aforementioned semi-trailing arms, wherein the semi-trailing arms each may comprise: at least one first bearing area for connecting the semi-trailing arm to a body of a motor vehicle, in particular to at least one longitudinal member or to at least one subframe, at least one second bearing area for connecting the semi-trailing arm to the body of the motor vehicle, in particular to at least one cross member or to at least one subframe, at least one wheel carrier for connecting the semi-trailing arm to a wheel, and at least one spring mount for connection to at least one spring strut for supporting the semi-trailing arm on the body of the motor vehicle, and preferably at least one cross member, subframe or decoupling member connected to second bearing areas of the at least two semi-trailing arms, characterized in that the semitrailing arms preferably each form a wheel steering axis which leads to toe-in correction of wheels connected to the semi-trailing arm axis when driving force is applied, when braking force is applied and when lateral force is applied. In particular, an aforementioned wheel steering axis is formed respectively. The advantageous embodiments and technical effects associated with such a wheel steering axis have already been described above in connection with the semi-trailing arm.

[0077] According to a third aspect, the aforementioned task is solved by a semi-trailing arm axle for a rear wheel suspension of a motor vehicle comprising: at least two semitrailing arms of the type described above, and at least one decoupling frame, wherein the at least one decoupling frame is connected to the second bearing areas of the at least two semi-trailing arms. The technical advantages and features associated with the semi-trailing arm axle essentially correspond to the technical advantages and features of the semi-trailing arm described above.

[0078] A preferred embodiment is characterized in that the wheel steering axes are designed in such a way that a negative scrub radius is provided on the wheels connected to the semi-trailing arm axle. In particular, a negative scrub radius is provided in that an intersection point of the respective wheel steering axis with the wheel contact plane

[0079] HF / HF 241028EP 18. Dezember 2025lies outside the wheel contact point, in particular as viewed in the Y direction. A negative scrub radius can lead to a toe-in correction in the event of a braking force occurring on a wheel connected to the semi-trailing arm.

[0080] A further preferred embodiment is characterized in that the wheel steering axes are designed in such a way that a negative caster distance is provided on the wheels connected to the semi-trailing arm axle. In particular, a negative caster distance is provided by an intersection point of the respective wheel steering axis with the wheel contact plane being located behind the wheel contact point as viewed in the direction of travel. A negative caster distance can lead to a toe-in correction in the event of a lateral force occurring on a wheel on the outside of the bend that is connected to the semi-trailing arm.

[0081] A further preferred embodiment is characterized by the fact that the wheel steering axes are designed in such a way that there is a positive spreading offset on the wheels connected to the semi-trailing arm axle. In particular, a positive spreading offset is provided by moving a point of intersection of the wheel steering axis with the wheel center plane inwards in the Y direction, i.e. towards the center of the vehicle. A positive spread offset can lead to toe-in correction in the event of a drive force occurring on a wheel connected to the semi-trailing arm.

[0082] Furthermore, it is preferable that a decoupling frame of a drive unit, in particular an electric drive unit, is connected, in particular bolted, to the second bearing areas of the semi-trailing arm. This can improve the connection stiffness between the various components. In addition, the number of connecting elements can be reduced by screwing the semi-trailing arm and decoupling frame together, which can lead to a reduction in costs.

[0083] Furthermore, it is preferred that a center axis of a mounting point of the decoupling frame is aligned with the bearing axis of the second bearing area, so that the assembly

[0084] HF / HF 241028EP 18. Dezember 2025of the wheel suspension can be simplified due to a common, vertical screwing direction or screwing axis.

[0085] Furthermore, it is preferred that the semi -trailing arm axle is designed for an axle load of less than 1200 kg.

[0086] By providing a semi-trailing arm axle as described above, a wheel suspension can be made available in a cost-effective manner, which enables an understeering design of a motor vehicle with rear- wheel drive and / or which provides vibration-damping properties.

[0087] The above-described embodiments and exemplary embodiments of all aspects of the present invention, which are independent with respect to each other and are also to be understood as disclosed in all combinations with one another.

[0088] Further advantageous exemplary embodiments of the invention can be found in the following detailed description of some exemplary embodiments of the present invention, in particular in connection with the figures. However, the figures accompanying the application are intended only for the purpose of clarification, but not for determining the scope of protection of the invention. The accompanying figures are not necessarily to scale and are merely intended to reflect the general concept of the present invention by way of example. In particular, features contained in the figures are in no way to be considered a necessary part of the present invention.

[0089] The invention is explained in more detail below with reference to the figures showing embodiments. They show:

[0090] Fig. 1 a schematic embodiment of a semi-trailing arm axle in a perspective view;

[0091] Fig. 2a schematic embodiment of a semi-trailing arm in a plan view;

[0092] HF / HF 241028EP 18. Dezember 2025Fig. 2b the embodiment of the semi-trailing arm shown in Fig. 2a in a rear view;

[0093] Fig. 2c schematic embodiment of a semi-trailing arm in a perspective view;

[0094] Fig. 3a a detailed view of an embodiment of a first bearing area of a semitrailing arm in a plan view;

[0095] Fig. 3b detailed view of an embodiment of a second bearing area of a semitrailing arm in a plan view;

[0096] Fig. 3c the embodiment of the second bearing area shown in Fig. 3b in a plan view;

[0097] Fig.4a a schematic view of an embodiment of a semi-trailing arm; and

[0098] Fig.4b a further schematic view of an embodiment of a semi-trailing arm.

[0099] In the following description of the various embodiments according to the invention, components and elements with the same function and the same mode of operation are provided with the same reference symbols, even if the components and elements may differ in their dimensions or shape in the various embodiments.

[0100] Fig. 1 shows an example of a semi-trailing arm axle 2. The semi-trailing arm axle 2 has two semi-trailing arms 4 and a cross member (not shown) connecting the two semitrailing arms 4 to each other. The two semi-trailing arms 4 are also connected to a decoupling frame 6. In particular, the semi-trailing arm axle 2 shown is a driven rear axle.

[0101] HF / HF 241028EP 18. Dezember 2025The semi-trailing arms 4 each have a first bearing area 8 for connecting the semitrailing arms 4 to a longitudinal member of the body or to a subframe (both not shown). The first bearing areas 8 are each arranged on the outside when viewed from the center of the vehicle. The semi-trailing arms 4 also each have a second bearing area 10 for connecting the respective semi -trailing arm 4 to the cross member of the body or to a subframe (both not shown). Furthermore, the semi-trailing arms 4 each have a spring mount 12 for connecting the semi-trailing arms 4 to a spring strut 14.

[0102] A first bearing 16 is arranged in the first bearing position 8, which is designed as a rubber-metal bearing in the present case. A second bearing 18, which is also designed as a rubber-metal bearing, is arranged in the second bearing position 8.

[0103] Furthermore, a wheel 20 is connected to the left-hand semi-trailing arm 4 by means of a wheel carrier 21.

[0104] The decoupling frame 6 also has fastening elements 22 for fastening the decoupling frame 6 to a vehicle body. In addition, the decoupling frame 6 has connecting elements 24 for connecting the decoupling frame 6 to a drive unit, in particular to an electric drive unit. The decoupling frame 6 can be connected to the vehicle body via the second bearing area 10 or the second bearing 18.

[0105] Further details regarding the design of the shown semi-trailing arm 6 can be seen in Figs. 2a, 2b and 2c.

[0106] As can be seen in Fig. 2a, both braking force Fb and lateral force Fs act on the wheel contact point 26. A wheel steering axis 28 intersects the wheel contact plane outside the wheel contact point 26 when viewed in the Y direction and behind the wheel contact point 26 when viewed in the direction of travel. This provides a negative scrub radius 30 and a negative caster distance 32, so that toe-in correction of the wheel 20 is possible with braking force Fb and lateral force Fs.

[0107] HF / HF 241028EP 18. Dezember 2025The wheel steering axis 28 runs through the intersection of a first pole line Ra of the first bearing 16 and a second pole line Ri of the second bearing 18. In addition, the wheel steering axis 28 runs in particular orthogonally to the plane spanned by the first pole line Ra and the second pole line Ri.

[0108] The pole line Ra of the first bearing 16 and the pole line Ri of the second bearing 18 are imaginary lines which are orthogonal to the potential movements of the respective bearings 16, 18. As an example, the bearing cross-sections 34 and 36 of the bearings 16 and 18 are shown next to the respective bearings 16 and 18. The formation of the pole lines Ra and Ri is explained in more detail in connection with Figs. 3a to 3c.

[0109] Fig. 2b and 2c show a rear view and a perspective view of the design example of the semi-trailing arm 4. It can be seen that the bearing center axis 34 of the first bearing 16 is slightly tilted with respect to the vertical, in particular with respect to the Z direction, and thus has an angle of inclination, for example an angle of inclination of essentially 15°, with respect to the vertical. The bearing center axis 36 of the second bearing 18 is not tilted and has an angle of inclination of essentially 0° relative to the vertical.

[0110] The tilted or inclined bearing center axis 34 of the first bearing 16 can provide a tilted or inclined wheel steering axis 28. A steering axis plane Ta of the first bearing and a steering axis plane Ti of the second bearing are spanned by the respective normals to their radial total directions of movement 56a, 56i and the respective axial direction or bearing center axis (34, 36). The spatially inclined wheel steering axis 28 is formed by the intersection of both steering axis planes Ta and Ti.

[0111] As can be seen from Fig. 2b and 2c, the driving force Fa acts on the wheel 20 at a different height than the braking force Fb and the lateral force Fs. In this case, the driving force Fa acts in negative X-direction, while the braking force Fb acts in positive X-direction.

[0112] HF / HF 241028EP 18. Dezember 2025While the braking force Fb and the lateral force Fs act on the wheel contact point 26, the drive force Fa acts on the wheel center 38.

[0113] By tilting the wheel steering axis 28, opposing lever arms of the wheel steering axis 28 can be provided for braking force Fb and driving force Fa, so that a toe-in correction of the wheel 20 connected to the semi-trailing arm 4 can be made possible for both opposing forces.

[0114] It can be seen that the intersection point 40 of the wheel steering axis 28 with the horizontal axis 42 of the wheel center plane is offset inwards, i.e. towards the center of the vehicle, so that a positive spreading offset 44 can be provided in the wheel center plane for the driving force Fa acting there.

[0115] Figs. 3a to 3c show the first bearing 16 and the second bearing 18 in a detailed plan view. It can be seen that both bearings 16 and 18 have a web 46 extending over substantially the entire diameter. In addition, the bearings 16 and 18 each have two pockets 48, which define a direction of extension of the bearings with reduced stiffness 50. The webs 46 are preferably part of an elastomeric inner part 47, which is bounded by a metallic sleeve 49.

[0116] In the first bearing 16, the direction of extension of the region with reduced stiffness 50 includes an angle ya of 245° and 265° around the bearing center axis 34 of the first bearing 16 with the X-axis running counter to the direction of travel.

[0117] In the second bearing 18, the direction of extension of the region with reduced stiffness 50 includes an angle yi of 215° and 225° around the bearing center axis 36 of the first bearing 16 with the X-axis running in the opposite direction to the direction of travel.

[0118] HF / HF 241028EP 18. Dezember 2025Fig. 3c uses the second bearing 18 as an example to show the determination of the potential direction of movement of the bearings 16 and 18. Arrow 52 indicates the movement of the bearing 18 in the direction of extension of the region with reduced stiffness 50, whereas arrow 54 indicates the movement of the bearing 18 in the direction of extension of the region with increased stiffness. Both are determined based on a predetermined exemplary force acting on the respective bearing 16 and 18. For example, the length of the arrows 52 and 54 may indicate a deflection of the bearing 18 when a specified force is applied in the respective direction. The resultant 56i then indicates the movement of the bearing 18, taking into account the specific bearing stiffness. The steering axis plane Ti of the bearing 18 is spanned orthogonally to the resultant 56i and the bearing center axis 36.

[0119] Fig.4a and 4b show further schematic view of embodiments of semi-trailing arm 4. It can be seen that the distance Lf of an arm axis 58 to the spring mount 24 is only slightly less than the distance Ln of the arm axis 58 to the wheel center 38. In particular, the ratio Lf / Ln is at least 0.9.

[0120] Fig.4b shows that the ratio between the bearing distance (Qn) of the first bearing 16 to the second bearing 18 and the spring distance (Qf) of the spring mount 24 to the bearing distance (Qn) to a wheel center 38, with said spring distance (Qf) being parallel projected to the bearing distance (Qn), is at least 3.0.

[0121] The exemplary embodiments / examples of the present invention described in this specification are to be understood as disclosed both individually and in all combinations with each other. In particular, the description of a feature encompassed by an embodiment - unless explicitly stated to the contrary - should not be understood herein to mean that the feature is indispensable or essential for the function of the embodiment.

[0122] Terms used in the patent claims such as "comprising", "including", "containing" and the like do not exclude further elements or steps. The phrase "at least partially"

[0123] HF / HF 241028EP 18. Dezember 2025includes both the case of "partially" and the case of "completely". The wording "and / or" is to be understood as meaning that both the alternative and the combination are to be disclosed, i.e. " A and / or B" means "(A) or (B) or (A and BJ". A plurality of entities, persons, or the like in the context of this specification means a plurality of entities, persons or the like. The use of the indefinite article does not preclude a plurality. A single device may perform the functions of several units or devices mentioned in the claims. Reference signs given in the claims are not to be regarded as limiting.

[0124] HF / HF 241028EP 18. Dezember 2025

Claims

HF / HF 241028EP18. Dezember 2025C l a i m s1. A semi-trailing arm (4) for a wheel suspension for rear wheels of motor vehicles, the semi-trailing arm (4) comprising:at least one first bearing area (8) for connecting the semi-trailing arm (4) to a body of a motor vehicle, in particular to at least one longitudinal member or to at least one subframe,at least one second bearing area (10) for connecting the semi-trailing arm (4) to the body of the motor vehicle, in particular to at least one cross member or to at least one subframe,at least one wheel carrier (21) for connecting the semi -trailing arm (4) to a wheel (20), andat least one spring mount (12) for connection to at least one spring strut (14) for supporting the semi-trailing arm (4) on the body of the motor vehicle, wherein the at least one first bearing area (8) has at least one first bearing (16), in particular a first rubber-metal bearing, and the at least one second bearing area (10) has at least one second bearing (18), in particular a second rubbermetal bearing,characterized in that,the first bearing (16) and the second bearing (18) each have at least one region with a reduced stiffness (50) and at least one region with an increased stiffness in the circumferential direction andthat the first bearing (16) and the second bearing (18) each have, in their respective axial directions (34, 36), at least partially a lowered stiffness relative to the area with increased stiffness in the circumferential direction of the respective bearing.

2. Semi-trailing arm (4) according to claim 1,wherein the first bearing (16) and the second bearing (18) have a stiffness ratio of between 1:10 and 1:35, in particular between 1:20 and 1:35, in the circumferential direction.

3. Semi-trailing arm (4) according to claim 1 or 2,wherein the first bearing (16) and the second bearing (18) each have a lowered stiffness in the axial direction, which has a ratio between 1:2 and 2:1 to the reduced stiffness in the circumferential direction.

4. Semi-trailing arm (4) according to claims 1 to 3,wherein a bearing center axis (34) of the first bearing (16) has an angle of inclination relative to the vertical in a range between 5° and 25°,wherein the vertical preferably refers to the installation state of the semi-trailing arm (4) in the motor vehicle.

5. Semi-trailing arm (4) according to claims 1 to 3,wherein a bearing center axis (36) of the second bearing (18) has an inclination angle relative to the vertical in a range between 0° and 5°, particularly preferably of essentially 0°,wherein the vertical preferably refers to the installation state of the semi-trailing arm (4) in the motor vehicle.

6. Semi-trailing arm (4) according to claim 4 or 5,wherein an extension direction of the region with reduced stiffness (50) of the first bearing (16) includes an angle (ya) around the bearing center axis (34) of the first bearing (16) with an X-axis, in particular with an X-axis running counter to the direction of travel, of between 245° and 265°; and / orwherein an extension direction of the region with reduced stiffness (50) of the second bearing (18) includes an angle (yi) around the bearing center axis (36) of the second bearing (18) with an X-axis, in particular with an X-axis running counter to the direction of travel, of between 215° and 225°.HF / HF 241028EP 18. Dezember 20257. Semi-trailing arm (4) according to one of claims 4 and 5,wherein the bearing center axis (34) of the first bearing (16) and the bearing center axis (36) of the second bearing (18) are inclined relative to each other.

8. Semi-trailing arm (4) according to any one of claims 1 to 7,wherein the first rubber-metal bearing (16) and / or the second rubber-metal bearing (18) has at least one essentially elastomeric inner part (47) and at least one outer part (49), in particular in the form of a sleeve, surrounding the elastomeric inner part (47) at least in sections, andwherein the inner part (47) preferably has at least one radial web (46) and at least one pocket (48).

9. Semi-trailing arm (4) according to claim 8,wherein the first rubber-metal bearing (16) and / or the second rubber-metal bearing (18) has at least one radial web (46) and at least two pockets (48) arranged substantially orthogonally to the at least one radial web (46), and wherein the stiffness ratio of the first rubber-metal bearing (16) and / or the second rubber-metal bearing (18) in the extension direction of the at least one radial web (46) relative to the extension direction of the at least two pockets (48) is preferably in a range from 1:10 to 1:35.

10. Semi-trailing arm (4) according to any one of claims 1 to 9,wherein the at least one spring mount (12) is designed such that a ratio between a distance (Lf) of the arm axis (58) to the spring mount (24) and a distance (Ln) of the arm axis (58) to a wheel center (38) of a wheel (20) connected to the semitrailing arm is at least 0.9 and / orwherein the ratio between the bearing distance (Qn) of the first bearing (16) to the second bearing (18) and the spring distance (Qf) of the spring mount (24) to a wheel center (38), with said spring distance (Qf) being parallel projected to the bearing distance (Qn), is at least 3.0.HF / HF 241028EP 18. Dezember 202511. Semi-trailing arm axle (2) for a rear wheel suspension of a motor vehicle, comprising:at least two semi -trailing arms (4) according to one of claims 1 to 10,- at least one decoupling frame (6), wherein the at least one decoupling frame (6) is connected to the second bearing areas (10) of the at least two semi-trailing arms (4).

12. Semi-trailing arm axle (2) according to claim 11,- wherein the decoupling frame (6) of a drive unit, in particular an electric drive unit, is connected, in particular bolted, to the second bearing areas (10) of the semi-trailing arms (4).

13. Semi-trailing arm axle (2) according to any one of claims 11 to 12,- wherein the semi -trailing arm axle (2) is designed for an axle load of less than 1200 kg.HF / HF 241028EP 18. Dezember 2025

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