Steering system for a vehicle, in particular a commercial vehicle

Abstract

The invention relates to a steering system (110) for a vehicle, in particular a commercial vehicle, having at least one steering gear (112), in particular a ball nut hydraulic steering gear, at least one steering mechanism (114) for steering at least one first vehicle wheel and at least one second vehicle wheel, wherein the steering gear (112) is coupled to the steering mechanism (114), at least one hydraulic pump (116) for supplying the steering gear (112) with hydraulic fluid, and at least one drive motor (118) which is independent and / or separate from the traction drive of the vehicle, which is coupled to the hydraulic pump (116) in order to drive the hydraulic pump, wherein the steering gear (112), the hydraulic pump (116) and the drive motor (118) are configured as a structural unit (120) in the assembled state.

Description

TECHNICAL FIELD

[0001] The invention relates to a steering system for a vehicle, in particular a commercial vehicle, having at least one steering transmission, in particular a ball nut hydraulic steering transmission, and at least one steering mechanism for steering at least one first vehicle wheel and at least one second vehicle wheel. BACKGROUND

[0002] The invention is in particular intended for a steering system in light and heavy commercial vehicles, which is equipped with an EPS steering support device (Electric Power Steering: EPS) based on the electro-hydraulic principle. The EPS steering system has a non-continuous operating behavior, i.e. the hydraulic oil in the hydraulic circuit of the steering gear is only delivered by a hydraulic pump during a steering movement (principle: on demand). If there is no steering, the hydraulic oil remains at rest (delivery volume of the hydraulic pump is essentially zero). A motor, for example a drive motor independent of the vehicle drive or traction drive (for example an electric motor in the form of an electric BLCD radial flux motor), serves as a drive for the hydraulic pump. Such a steering system can be used to function as an on-demand steering system (for example in electric commercial vehicles without an internal combustion engine, or in order to achieve automated driving requirements independently of driver intervention, for example by means of a driver assistance system).

[0003] In the future, therefore, further increasing functional requirements will be placed on steering systems for vehicles, in particular commercial vehicles, since the steering system plays an important role in the (partial) automation of the vehicle.

[0004] It is particularly important here that the steering system functions precisely and reliably and takes these increasing functional requirements into account and can still be further optimized in terms of structural space requirements. The increasing functional density in vehicles does not only relate to the steering system, so that the steering system should also be aimed at an optimization of the structural space in the event of a basically unchanged structural space in the vehicle in order to achieve further functions of the steering system and the vehicle itself.

[0005] From the prior art, steering systems for vehicles are already known.

[0006] DE 101 14 600 A1 therefore shows a vehicle steering having a steering control device, in particular a steering wheel, which can be actuated by a driver, a pair of electromechanical actuating devices (Stellaggregat) for respectively controlling one of a pair of steerable vehicle axles, which are located on the right and left of the vehicle body, one of the actuating devices for the steering wheel, means which, in the event of a failure or malfunction of one of the two actuating devices assigned to the steerable axle, ensure control of the two wheels of this axle by means of the respective other still functioning actuating device.

[0007] Furthermore, DE 112 02 082 663 T5 discloses a vehicle steering apparatus, comprising: a steering apparatus configured to rotate steered wheels in accordance with an operation of a steering wheel of a vehicle, wherein the steering apparatus includes first and second motors for steering, the first and second motors having electrical characteristics set to be identical to each other; a first current sensor configured to sense a first current value of a current flowing through the first motor; a second current sensor configured to sense a second current value of a current flowing through the second motor; and an abnormality diagnosis unit.

[0008] DE 102 011 121 827 A1 shows a power steering system, comprising: a power cylinder provided with a pair of pressure chambers to supply a steering force to at least one of steered wheels based on a pressure difference of the pair of pressure chambers; a steering mechanism to deflect the steered wheels in accordance with a steering rotation operation of a steering wheel; a first pump provided with a first drive shaft to suck and discharge a working fluid in accordance with a rotation of the first drive shaft to deliver the working fluid to the power cylinder, wherein the first pump is driven to rotate by a first drive source; a second pump provided with a second drive shaft to suck and discharge the working fluid in accordance with a rotation of the second drive shaft to deliver the working fluid to the power cylinder; a second drive source, which is a different drive source from the first drive source, constituted by an electric motor and driving the second pump to rotate; and a control valve arranged in the steering mechanism to selectively deliver the working fluid, which has been delivered by the first pump or the second pump, to the pair of pressure chambers in accordance with a steering rotation movement of the steering wheel.

[0009] Such steering devices in the prior art are still either expensive and complex or composed of many components, require a large structural space and have a greater weight. As a result, a plurality of error sources arise, which in the worst case can lead to a malfunction of the vehicle. SUMMARY

[0010] It is therefore the task of the present invention to expand the steering system mentioned at the outset in an advantageous manner, in particular in the following respects: the steering system has a smaller weight, is optimized in terms of structural space and implements the steering instructions to the wheels more precisely and more dynamically.

[0011] According to the application, this task is solved by a steering system having the features of the application. According to this, a steering system for a vehicle, in particular a commercial vehicle, is provided with at least one steering gear, in particular a ball nut hydraulic steering gear, at least one steering mechanism for steering at least one first vehicle wheel and at least one second vehicle wheel, wherein the steering gear is coupled to the steering mechanism, at least one hydraulic pump for supplying the steering gear with hydraulic fluid, and at least one drive motor which is independent and / or separate from the traction drive of the vehicle and which is coupled to the hydraulic pump in order to drive the hydraulic pump, wherein the steering gear, the hydraulic pump and the drive motor are configured as a structural unit in the assembled state.

[0012] The application is based on the basic idea that the steering system has a structurally and functionally integrated steering gear. In contrast to the prior art, in which in particular the hydraulic pump and the ancillaries, such as compensation vessels, if necessary valves, etc., are arranged in the vicinity of the traction drive, according to the application the steering gear, the hydraulic pump and the drive motor are combined as a common structural unit. The hydraulic lines can thereby be configured significantly shorter, thereby additionally resulting in less heat loss and flow loss. Furthermore, the steering system can be configured more weight-saving and with less structural space requirement by such a configuration. In this overall solution, the plug-and-play solution, the hydraulic circuit is decoupled from the traction drive of the vehicle, usually an internal combustion engine or a hybrid drive, and is arranged as a compact unit to the steering gear. In this context, it is also conceivable that the hydraulic pump and the drive motor are configured as a preassembled common motor-pump unit and are flange-connected to the steering gear in order to configure the structural unit.

[0013] Furthermore, it can be provided that the drive motor is coupled directly, in particular without a coupling, to the hydraulic pump. Thereby, the motor-pump unit becomes more compact, thereby resulting in further advantages in terms of structural space and weight. Furthermore, this motor-pump unit can thereby be configured more rigidly, so that less material fatigue or wear occurs and thus a higher efficiency of the motor-pump unit can be achieved.

[0014] It is further conceivable that the drive motor and the hydraulic pump have at least one common drive shaft. By this configuration, the motor-pump unit becomes more compact, thereby resulting in further advantages in terms of structural space and weight. Furthermore, by the configuration of the drive shaft, for example by targeted diameter selection, the individual requirements of the hydraulic pump and the drive motor can be specifically met. Thus, the motor-pump unit can use fewer components, thereby being configured less complex and less error-prone, but still meeting the requirements of the hydraulic pump and the drive motor for the drive shaft.

[0015] Furthermore, it is conceivable that the steering system has at least one first shaft bearing device and at least one second shaft bearing device, through which the drive shaft is at least partially supported in the assembled state. In addition to the first and second shaft bearing devices, the electric motor and / or the hydraulic pump can have further bearing devices in their respective housings. The first and second shaft bearing devices are used, inter alia, to reconcile the partly contradictory requirements of the hydraulic pump and the drive motor on the drive shaft. Thus, the drive motor requires a drive shaft that is as rigid or inflexible as possible together with a bearing in order to keep the air gap (between the stator and the rotor) constant at different torques and shaft speeds, for example in the case of an electric motor as drive motor. The hydraulic pump, in turn, requires a shaft that is as flexible, elastic or flexible as possible in order to enable a radial movement within the hydraulic pump, inter alia, within a defined range. This is necessary to ensure pressure and temperature compensation within the pump and thus to keep the operating range of the pump in terms of pressure and temperature requirements as large as possible.

[0016] Furthermore, it is possible that the first shaft bearing device and the second shaft bearing device configure a hybrid bearing system. A hybrid bearing system is particularly suitable for reconciling the partly contradictory requirements of the motor-pump unit on the drive shaft. Thus, for example, the first shaft bearing device can be configured to be rigid at least in terms of the occurring bending stresses of the drive shaft in the region of the drive motor. In contrast thereto, the drive shaft can be configured to be elastic or flexible at least in terms of the occurring bending stresses in the region of the hydraulic pump by the axially defined distance of the second shaft bearing device to the hydraulic pump and by a corresponding configuration.

[0017] Furthermore, it can be provided that the first shaft bearing device is arranged on the drive shaft between the drive motor and the hydraulic pump in the assembled state. This arrangement is particularly advantageous for the bending resistance of the drive shaft in the region of the drive motor. The first shaft bearing device generates a radial bearing reaction force between the hydraulic pump and the drive motor, which compensates the radial or bending forces generated by the hydraulic pump and the resulting bending moments. Thereby, only a very small bending deformation of the drive shaft occurs within the drive motor, which has a positive effect on the efficiency.

[0018] It is likewise conceivable that the first shaft bearing device is configured as a deep groove ball bearing, in particular a double-row deep groove ball bearing. A deep groove ball bearing is very well suited to configure the first shaft bearing device as a very mature and used millions of times component with clearly defined advantages, such as a small radial bearing play at the same time limited radial force load capacity and low costs. However, a double-row deep groove ball bearing is particularly suitable because its axial dimension, although greater than that of a single-row ball bearing, enables a more loadable and more robust bearing to be provided. Furthermore, by the additional axial extension, a more rigid support is achieved, which increases the efficiency of the drive motor for the same reasons already explained above.

[0019] Furthermore, it is conceivable that the drive shaft has an axial end which, in the assembled state, protrudes on the side of the hydraulic pump facing away from the drive motor, wherein the second shaft bearing arrangement is arranged on this axial end of the drive shaft.

[0020] With such a configuration, the lever arm between the radial reaction force of the second shaft bearing arrangement and the radial forces occurring in the hydraulic pump is increased. The increased lever arm results in greater flexibility or pliability of the drive shaft in the region of the hydraulic pump, so that the requirements for the pliability of the drive shaft in the hydraulic pump can be better met by such an arrangement of the second shaft bearing arrangement.

[0021] It is further possible that the second shaft bearing arrangement is configured as a hydrodynamic plain bearing. In comparison with deep groove ball bearings, this hydrodynamic plain bearing has a greater bearing play in the radial direction. Thereby, the flexibility or pliability of the drive shaft in the hydraulic pump is further increased, so that the requirements for the drive shaft in the region of the hydraulic pump can be better met. Furthermore, hydrodynamic plain bearings are already very mature structural elements which can absorb particularly high radial forces in a small space.

[0022] It is additionally possible to provide that the drive shaft has a motor shaft section in the region of the drive motor and a pump shaft section in the region of the hydraulic pump, wherein the motor shaft section has a greater diameter than the pump shaft section. In addition to the above-described configurations of the first and second shaft bearing arrangements, the configuration of the shaft sections also provides a further constructional possibility to more advantageously reconcile the partly contradictory requirements of the drive motor and the hydraulic pump on the drive shaft. Due to the reduced diameter of the pump shaft section, the polar resistance moment of the pump shaft section is reduced, so that the required elastic properties are further improved, in particular under bending loads. The opposite is the case in the motor shaft section, the increased diameter of which accordingly brings about an increased polar resistance moment and the shaft section is correspondingly configured more rigid, so that the efficiency of the drive motor can be further increased, as has been set out above.

[0023] It is furthermore conceivable that the drive motor is configured as an electric motor. The integration of the electric motor into a structural unit which additionally consists of the hydraulic pump and the steering gear has the advantage that the electric motor can be controlled or regulated very well, i.e. the regulation of the electric motor can take place very dynamically and the switching of the rotational direction can be regulated or controlled very simply, precisely and quickly. Furthermore, the electric motor can be simply integrated into or coupled with existing control or regulation device architectures. Thus, the electric motor can have its own control device. Additionally or alternatively, it is possible that the electric motor can be operated by a control device of the steering system or by a vehicle control device. These control devices can of course also take over the regulation task of the electric motor. Furthermore, the electric motor can be controlled or regulated in order to implement a driver assistance system, for example a lane-keeping assistance, a traffic jam assistance, a wind compensation assistance or a partially or fully autonomous steering instruction.

[0024] It is likewise conceivable that the hydraulic pump is configured as a bidirectional hydraulic pump. This configuration has the particular advantage that the hydraulic flow which loads the double-acting pistons in the steering gear with pressure can be reversed by the pump. As a result, it is possible to dispense with the troublesome and expensive control valves if necessary, so that the steering of the steering gear or the supply is simplified. The regulation and / or control outlay for the steering system is likewise reduced, since the steering of the additional valves can be dispensed with. BRIEF DESCRIPTION OF DRAWINGS

[0025] Further details and advantages of the application will now be explained in greater detail with reference to the embodiments shown in the drawings.

[0026] The drawings show:

[0027] Figure 1 schematic perspective view of a steering system in the prior art;

[0028] Figure 2a first schematic block diagram of an embodiment of a steering system according to the application; and

[0029] Figure 2b second schematic block diagram of an embodiment of a steering system according to the application according to Figure 2a the application. DETAILED DESCRIPTION

[0030] Figure 1 A schematic perspective view of a steering system 10 in the prior art is shown.

[0031] The steering system 10 essentially consists of a steering gear 12 in the form of a ball nut hydraulic steering gear, of a steering mechanism 14 coupled with this steering gear for steering two wheels (not shown in the drawing). Figure 1 The steering system 10 essentially consists of a steering gear 12 in the form of a ball nut hydraulic steering gear, of a steering mechanism 14 coupled with this steering gear for steering two wheels (not shown in the drawing).

[0032] The steering mechanism has a first and a second steering straight rod 14a, 14b and a first and a second steering cross rod 14c, 14d.

[0033] According to Figure 1 , the first steering straight rod 14a and the first steering cross rod 14c are hingedly connected with the first wheel carrier for steering or pivoting the first wheel carrier, wherein the first steering straight rod 14a is coupled with the output shaft of the steering gear 12.

[0034] The second steering straight rod 14c is in turn hingedly connected to the first wheel carrier via a carrier element and thus hingedly couples the first wheel carrier with the second wheel carrier via the carrier element and the second steering cross rod 14d.

[0035] Furthermore, the steering system 10 has a hydraulic pump 16 which is coupled with the steering gear 12 via a pipe 16a for supplying the steering gear with hydraulic oil.

[0036] Between the hydraulic output of the steering gear 12 and the input of the hydraulic pump 16, the pipe 16a is arranged in the middle with a compensation vessel 16b.

[0037] Furthermore, the steering system according to Figure 1 comprises a steering column 17 formed as a multi-joint linkage and a steering wheel 17a coupled torsionally thereon for manually controlling the steering gear 12, which leads to a pivoting of the steering mechanism 14 and then to a steering of the wheels.

[0038] Figure 2a A first schematic block diagram of an embodiment of a steering system 110 according to the application is shown.

[0039] The components of the steering system 110 according to the application which are identical or similar to the steering system 10 according to Figure 1 from the prior art have the reference numerals of the components increased by 100, respectively.

[0040] According to Figure 2a , the steering system 110 for a vehicle has a steering gear 112.

[0041] The steering gear 112 is configured as a ball nut hydraulic steering gear and the vehicle is correspondingly configured as a commercial vehicle.

[0042] Furthermore, the steering system 110 has a steering mechanism 114 for steering a first wheel and for steering a second wheel.

[0043] As a representative of the steering mechanism 114, in Figure 2aThe first steering tie rod 114a is only shown schematically, as coupled torsionally to the output shaft 112a of the steering gear 112.

[0044] The steering gear 112 is thus coupled to the steering mechanism 114 via the first steering tie rod 114a.

[0045] Furthermore, the steering system 110 has a hydraulic pump 116 for supplying the steering gear 112 with hydraulic fluid.

[0046] The hydraulic pump 116 is configured as a bidirectional hydraulic pump 116.

[0047] In this case, "bidirectional" means that the hydraulic pump 116 can interchange the pressure side and the suction side and thus can reverse the hydraulic flow depending on the steering direction by switching its rotational direction, which is carried out by the drive motor 118.

[0048] This reversed hydraulic flow is then loaded, depending on the desired or controlled steering movement, on the double-acting steering cylinder in the interior of the steering gear.

[0049] Furthermore, the drive motor 118 is arranged independently and separately from the traction drive of the vehicle, which is coupled to the hydraulic pump 116 to drive the latter.

[0050] According to the basic idea of the application, the steering gear 112, the hydraulic pump 116 and the drive motor 118 are configured in the assembled state as a common structural unit 120.

[0051] Further auxiliary equipment, for example a compensation vessel of the hydraulic pump 116 or a control or regulation of the drive motor 118, can likewise be integrated into the structural unit 120, but are not shown in Figure 2a .

[0052] Furthermore, it can be provided that the hydraulic pump 116 and the drive motor 118 are configured as a preassembled common motor-pump unit 120a and are flange-connected to the steering gear 112 on the end side for the configuration of the structural unit 120.

[0053] Here, the motor-pump unit 120a can be flange-connected to the steering gear 112 on the end side opposite the mechanical direct drive 112b for the mechanical coupling to the steering column.

[0054] Alternatively, it is likewise conceivable that the motor-pump unit 120a can be flange-connected to the steering gear 112 on the end side in the region of the mechanical direct drive 112b.

[0055] Alternatively, the motor-pump unit 120a can also be flange-connected to an axial extension of the steering gear 112 on the outside thereof.

[0056] As further derivable from Figure 2a , hydraulic lines or additional hydraulic switching valves are not shown; only the mechanical direct drive 112b for mechanical coupling with the steering column is shown.

[0057] Figure 2b A second schematic block diagram of an embodiment of a steering system according to the application is shown according to Figure 2a .

[0058] Herein, a motor-pump unit is substantially visible, which motor-pump unit substantially consists of the hydraulic pump 116 and the drive motor 118.

[0059] Here, the drive motor 118 is directly coupled with the hydraulic pump 116.

[0060] In the present context, "directly" can mean that the drive motor 118 and the hydraulic pump 116 are connected to each other without intermediate members, torsionally. Thus, a coupling is dispensed with.

[0061] Furthermore, in this connection with "direct coupling", it should be mentioned that the drive motor 118 and the hydraulic pump 116 have a common drive shaft 122 for the direct coupling.

[0062] The drive shaft 122 extends axially from the drive motor 118 to the hydraulic pump 116, which drive shaft projects axially from the hydraulic pump 116 in the direction of the steering gear 112 in the assembled state.

[0063] The drive motor 118 is configured as an electric motor and has a rotor 118a and a stator 118b, which rotor is torsionally coupled with the drive shaft 122.

[0064] The steering system 110 and in particular the motor-pump unit 120a also has a first shaft bearing device 124 and a second shaft bearing device 126.

[0065] By means of the first and second shaft bearing devices 124, 126, the drive shaft is at least partially supported therein in the assembled state.

[0066] Additionally, the drive motor 118 and the hydraulic pump 116 can have further bearing devices in their respective housings, which are not shown in Figure 2b .

[0067] According to Figure 2b , the first shaft bearing device 124 is arranged on the drive shaft 122 between the drive motor 118 and the hydraulic pump 116 in the assembled state.

[0068] In this arrangement, the first shaft bearing device 124 is arranged axially closer to the drive motor 118 than to the hydraulic pump 116.

[0069] Likewise, it is conceivable in this context that the first shaft bearing device 124 is flange-connected to the housing of the drive motor 118 by means of a cover part, or that the first shaft bearing device 124 is directly supported in the housing of the drive motor 118.

[0070] Additionally or alternatively, it can be provided that the drive motor 118 and the hydraulic pump 116 are coupled to one another by means of a (not shown here) flange and the first shaft bearing device 124 is received or supported by means of this flange. Figure 2b

[0071] The first shaft bearing device 124 is configured as a deep groove ball bearing.

[0072] The deep groove ball bearing can in turn be particularly advantageously configured as a double-row deep groove ball bearing.

[0073] As mentioned above, the drive shaft 122 has an axial end 122a which, in the assembled state, projects on the side of the hydraulic pump 116 facing away from the drive motor 118.

[0074] On this axial end 122a, a second shaft bearing device 126 is arranged.

[0075] The second shaft bearing device 126 can be arranged directly or flange-connected on the housing of the hydraulic pump 116 or have a defined axial distance from this housing.

[0076] It is further conceivable that the second shaft bearing device 126 is flange-connected to the hydraulic pump 116 or is a direct component of the housing of the hydraulic pump 116.

[0077] The second shaft bearing device 126 is configured as a hydrodynamic plain bearing.

[0078] The first and second shaft bearing devices 124, 126 thus configure a hybrid bearing system.

[0079] Here, a "hybrid bearing system" is to be understood such that the first and second shaft bearing devices 124, 126 differ in their respective bearing concepts or bearing configurations.

[0080] The hybrid bearing system in the form of a double-row deep groove ball bearing and a hydrodynamic plain bearing is thus merely exemplary, such that other hybrid bearing configurations are also conceivable.

[0081] Other rolling bearing forms can also be used, for example cylindrical roller bearings, needle roller bearings, tapered roller bearings, barrel roller bearings or toroidal roller bearings.

[0082] The same applies to plain bearings, for which it is also conceivable, for example, that static pressure plain bearings are used. ​

[0083] As bearing material, for the plain bearing bush, bronze (copper-tin alloy), white metal (lead-tin alloy), bearing metal alloyed with lead, aluminum alloy, plastic (e.g. PTFE), ceramic (also fiber-reinforced ceramic), graphite or brass alloy can be used.

[0084] As can be gathered from Figure 2b The drive shaft 122 has a motor shaft section 122b in the region of the drive motor 118 and a pump shaft section 122c in the region of the hydraulic pump.

[0085] The motor shaft section 122b here has a greater diameter than the pump shaft section 122c.

[0086] According to Figure 2b The first shaft bearing device 124 is still supported on a shaft section which corresponds to the diameter of the pump shaft section 122c.

[0087] Alternatively, the first shaft bearing device 124 can be supported on a shaft section which corresponds to the diameter of the motor shaft section 122b or a diameter which lies between the two diameters.

[0088] According to Figure 2b The drive shaft 122 is shown schematically as a simple stepped shaft, wherein the drive shaft 122 can also have a plurality of steps or shaft shoulders.

[0089] List of reference signs

[0090] 10 steering system

[0091] 12 steering transmission

[0092] 14 steering mechanism

[0093] 14a first steering straight rod

[0094] 14b second steering straight rod

[0095] 14c first steering tie rod

[0096] 14d second steering tie rod

[0097] 16 hydraulic pump

[0098] 16a pipe

[0099] 16b compensation vessel

[0100] 17 steering column

[0101] 17a steering wheel

[0102] 110 steering system

[0103] 112 steering transmission

[0104] 112a output shaft of the steering transmission

[0105] 112b direct transmission

[0106] 114 steering mechanism

[0107] 114a first steering tie rod

[0108] 116 hydraulic pump

[0109] 118 drive motor

[0110] 118a rotor

[0111] 118b stator

[0112] 120 structural unit

[0113] 120a motor-pump unit

[0114] 122 drive shaft

[0115] 122a axial end of the drive shaft

[0116] 122b motor shaft section

[0117] 122c pump shaft section

[0118] 124 first shaft bearing device

[0119] 126 second shaft bearing device

Claims

1. A steering system (110) for a vehicle, having: at least one steering transmission (112); the steering transmission (112) is coupled with the steering mechanism (114); at least one hydraulic pump (116) for supplying the steering transmission (112) with hydraulic fluid; and at least one drive motor (118) which is arranged independently and / or separately from a traction drive of the vehicle, the drive motor is coupled with the hydraulic pump (116) to drive the hydraulic pump, wherein the steering transmission (112), the hydraulic pump (116) and the drive motor (118) are configured as a structural unit (120) in an assembled state, wherein the drive motor (118) is directly coupled with the hydraulic pump (116), the drive motor (118) and the hydraulic pump (116) have at least one common drive shaft (122), the steering system (110) has at least one first shaft bearing arrangement (124) and at least one second shaft bearing arrangement (126), the drive shaft (122) is at least partially supported by the first shaft bearing arrangement and the second shaft bearing arrangement in the assembled state, the drive shaft (122) has an axial end (122a) which protrudes in the assembled state on a side of the hydraulic pump (116) facing away from the drive motor (118), wherein the second shaft bearing arrangement (126) is arranged on this axial end (122a) of the drive shaft (122), the second shaft bearing arrangement (126) is configured as a hydrodynamic plain bearing, and the drive shaft (122) has a motor shaft section (122b) in the region of the drive motor (118) and a pump shaft section (122c) in the region of the hydraulic pump (116), wherein the motor shaft section (122b) has a greater diameter than the pump shaft section (122c). The drive motor (118) is coupled with the hydraulic pump (116) without a coupling. at least one steering mechanism (114) for steering at least one first wheel and at least one second wheel, wherein The vehicle is a commercial vehicle. The steering transmission (112) is a ball nut hydraulic steering transmission. The first shaft bearing arrangement (124) and the second shaft bearing arrangement (126) form a hybrid bearing system. The first shaft bearing arrangement (124) is arranged on the drive shaft (122) between the drive motor (118) and the hydraulic pump (116) in the assembled state.

2. The steering system (110) according to claim 1, characterized in that The first shaft bearing arrangement (124) is configured as a deep groove ball bearing.

3. The steering system (110) according to claim 1, characterized in that The first shaft bearing arrangement (124) is configured as a double-row deep groove ball bearing.

4. The steering system (110) of claim 1, characterized in that, The drive motor (118) is configured as an electric motor.

5. The steering system (110) of claim 1, characterized in that, The hydraulic pump (116) is configured as a bidirectional hydraulic pump (116).

6. The steering system (110) according to any one of claims 1 to 5, characterized in that ​ 7. The steering system (110) according to any one of claims 1 to 5, characterized in that ​ 8. The steering system (110) according to claim 7, characterized in that ​ 9. The steering system (110) according to any one of claims 1-5, characterized in that, ​ 10. The steering system (110) according to any one of claims 1-5, characterized in that, ​

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