Power Assisted Steering System Layout

Abstract

The present invention relates to a power assisted steering system arrangement (100A) for a vehicle, comprising a steering wheel (120A), a first driver linkage arrangement (10A), the first driver linkage arrangement (10A) comprising a linkage arrangement between the steering wheel (120C) and the front wheels (127, 127), the linkage arrangement comprising a steering column (121A), a recirculating ball joint (RCB) (123A) arranged on a first side of the vehicle, a tie rod arrangement for steering the front wheels (127, 127), a first lever arm (124A) arranged to transmit a torque applied by the driver via the steering wheel to the tie rod arrangement, the first lever arm (124A) providing a connection between the RCB (123A) and the tie rod arrangement. The system also includes: a torsion bar (128A) having a torsion bar torque sensor associated with a steering column (121A); an auxiliary actuator (30A) arranged on a second side of the vehicle, opposite to a side of the vehicle on which the RCB is arranged, the auxiliary actuator (30A) comprising at least an electric motor (115A) and an electronic control unit ECU (110A) which controls the electric motor according to a control signal received from the torsion bar torque sensor; and an auxiliary actuator linkage arrangement (20A) connected to a tie rod arrangement so that a steering torque applied by a driver and an auxiliary actuator torque provided or applied by the auxiliary actuator (30A) are transmitted to the tie rod arrangement for steering the front wheels of the vehicle.

Description

Technical Field

[0001] The invention relates to a power assisted steering system arrangement. Background Art

[0002] For heavy trucks or large pickup trucks, there is no room for rack and pinion steering as is usually the case with passenger cars, where the steering rack is mounted on the subframe, which is non-existent for heavy vehicles. Therefore, for heavy vehicles, especially for heavy trucks, other solutions must be used. A recirculating ball gearbox (RCB), a pitman arm, a tie rod and two tie rods are usually used to steer the two pitman arms that turn and steer the front wheels of the vehicle.

[0003] An example of such a prior art steering system layout is shown in FIG. 1 of the present application, which is also described further below.

[0004] Another prior art steering system layout is shown in Figure 2. Here, the steering rocker arm does not directly affect the tie rod. Instead, there is a linkage to the stub axle and another linkage that transfers the steering angle between the two stub axles.

[0005] The linkage to the stub axle consists of a straight tie rod (from the rocker arm or pitman arm) and a straight tie rod arm (or steering arm) with a joint in between. The linkage for transmitting the steering angle consists of two tie rod arms and a tie rod with a joint in between.

[0006] Figure 3 shows another prior art solution for the steering system layout. In the solution shown in Figure 3, there is a straight tie rod from the steering rocker arm to the passenger side steering arm. The linkage between the wheels also includes a tie rod here.

[0007] Power assisted steering is incorporated in RCBs on heavy trucks where the assist force is achieved by hydraulic power. The driver applies a torque in the steering column which results in a twist in the valve in the gearbox causing the valve to open hydraulic fluid pressure to one chamber of a cylinder inside the RCB where the cylinder is also the nut of a recirculating ball screw. Thus the screw is turned by the driver and the nut is driven axially by the hydraulic power resulting in an assist force dependent on the torque applied by the driver in the steering column.

[0008] Hydraulic power has a very high power density. Therefore, a power-assisted RCB is very compact and easily fits into the side of the vehicle's frame. Typically, the space around the engine of a vehicle is very limited, and the RCB fits right into the free space. Therefore, there is limited space around the RCB to add new subsystems.

[0009] However, there are disadvantages associated with using hydraulic power as it requires filling with fluid, monitoring the level of the fluid, the risk of fluid leaking over time, etc.

[0010] There is a trend towards electrification of vehicles. It is recognised that there will be sufficient electricity available for power assisted steering. Therefore, an RCB capable of having electric power assistance would be advantageous.

[0011] However, while hydraulic systems have high power density and are easy to fit in an RCB, the same cannot be said for electric motors with gearboxes. Without hydraulics, an unassisted RCB would be slightly smaller, but the reduction in size would not even approach the degree required to fit an electric motor with reduction gears on it and provide the same amount of assistance as a conventional hydraulic assist system.

[0012] Therefore, in many cases, insufficient packaging volume is available to fit the electric motor with the reduction gear, which is a serious problem and constitutes an obstacle to the introduction of electrically assisted RCBs. Summary of the invention

[0013] It is therefore an object of the present invention to provide a power assisted steering system arrangement by which one or more of the above mentioned problems may be solved.

[0014] In particular, it is an object of the present invention to provide a simple and cost-effective power assisted steering system arrangement. Still further, it is a specific object of the present invention to provide a flexible and compact power assisted steering system arrangement.

[0015] In particular, the object of the present invention is to provide a power-assisted steering arrangement which has a high assistance performance and is suitable for both left-hand drive vehicles and right-hand drive vehicles.

[0016] Thus, the initially mentioned power-assisted steering arrangement is provided, which has the characteristic features of the basic solution of the application.

[0017] Advantageous embodiments are given by the preferred embodiments of the present application.

[0018] An advantage of the invention is that it enables power assisted steering of heavy trucks. Another advantage is that an arrangement is provided which can be easily packaged in the packaging volume of an RCB that can be used for both left-hand drive vehicles and right-hand drive vehicles. With the solution according to the invention, the available space can be efficiently utilized, for both left-hand drive and right-hand drive vehicles, the space on the driver's side and the passenger's side will be utilized, and a very simple and cost-effective solution is provided.

[0019] Another advantage of the present invention is that it facilitates manufacturing and assembly and enables reduced maintenance and monitoring of the auxiliary system and also avoids consumption and leakage of hydraulic fluid and also provides an environmentally friendly steering assistance solution. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The invention will be further described hereinafter in a non-limiting manner, by way of example only and with reference to the accompanying drawings, in which:

[0021] FIG. 1 is a schematic diagram of a conventional, prior art steering system for a heavy truck,

[0022] FIG. 2 is a schematic diagram of another conventional, prior art steering system for a heavy truck,

[0023] FIG3 is a schematic diagram of another prior art steering system for a heavy truck,

[0024] Figure 4 The diagram schematically shows an arrangement of an electric power assisted steering system for a heavy vehicle according to a first embodiment of the present invention.

[0025] Figure 5 schematically shows an electric power assisted steering system for a heavy vehicle according to a second embodiment of the present invention, and

[0026] Figure 6 An electric power assisted steering system for a heavy vehicle according to a third embodiment of the present invention is schematically shown.

[0027] Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It should be understood, however, that the drawings are designed for illustrative purposes only and not as a definition of the limits of the present invention, for which reference should be made to the appended claims and the specification as a whole. It should also be understood that the drawings are not necessarily drawn to scale and that, unless otherwise indicated, they are intended only to conceptually illustrate the structures and procedures described herein. Reference numerals with the same but different subscripts are used to indicate corresponding features in different drawings. DETAILED DESCRIPTION

[0028] In order to facilitate the understanding of the present invention, some definitions will be introduced below, and some different prior art solutions based on hydraulic assistance will be described with reference to FIGS. 1 to 3 .

[0029] definition

[0030] A steering position actuator is an actuator that can be used to affect one or more of the steering actuator states, such as rear wheel steering angle, individual steering angles of wheels, axle braking torque or force, wheel braking torque or force, drive torque or force on a single axle, drive torque or force on a single wheel, camber angle on each axle, or camber angle on each wheel.

[0031] State is defined as translational or rotational position, velocity or acceleration, or one or more of states derived from these states, such as, for example, the vehicle slip angle, which is the angle between the vehicle local x-axis and the vehicle velocity vector.

[0032] A signal bus is a transmission path on which signals can be read and / or transmitted.

[0033] Controllability describes the ability of an external input to move the internal state of a system from any initial state to any other final state within a finite time interval.

[0034] A vehicle state controller is defined here as a dynamic function used to achieve a target state in the vehicle in a controlled manner.

[0035] Vehicle state actuators are actuators that, when actuated, affect one or several vehicle states. Examples of vehicle state actuators are brakes, engines, controllable four-wheel drive clutches, controllable differentials, active shock absorbers, electric or hydraulic wheel motors, and electric or hydraulic driven axles.

[0036] An actuator is a mechanism or system that is operated by the ECU and converts an energy source (typically electrical current, hydraulic fluid pressure, or pneumatic pressure) into motion, force, or torque.

[0037] The target value, reference value or request is the set point of the actuator achieved by using a closed loop controller and / or a feedforward controller.

[0038] The steering wheel torque measurement is the torque measured in the steering column or steering wheel or the force measured in the steering rack multiplied by the torque ratio between the steering rack and the steering wheel.

[0039] The steering wheel angle here refers to any angle between the steering wheel and the road wheels multiplied by the ratio between the angular degrees of freedom and the steering wheel angular degrees of freedom. It can also be the rack position multiplied by the ratio between the rack translational degrees of freedom and the steering wheel angular degrees of freedom.

[0040] The steering angle of one wheel is shown here, but if the wheels are steered differently (as in the case of Ackermann steering, for example), the steering angle is defined as the average of the angles of the two wheels.

[0041] A recirculating ball gearbox (RCB) is a steering mechanism that uses a recirculating ball screw to convert the input torque applied by the driver in the steering wheel into an output torque in a lever arm (steering rocker arm) which, via a linkage, steers the front wheels. RCBs can be with or without hydraulic assist.

[0042] Torsion bar torque is the torque measured by using a sensor that is sensitive to the twisting of a specific torsion bar mounted somewhere in the steering column.

[0043] The torsion bar torque sensor may preferably be of a type having both torque sensing and angle sensing, a so-called torque and angle sensor (TAS).

[0044] An ECU is an electronic control unit that reads analog sensor signals and digital signals, e.g. from a signal bus, and performs any type of calculations, such as e.g. executing control tasks and actuating actuators, either via analog or digital signals sent, or by directly controlling an electric motor, e.g. from a motor control stage.

[0045] FIG. 1 is a schematic diagram of a prior art steering system 100A′, for which the concepts of the present invention based on electric assistance (rather than hydraulic assistance) can be implemented, as will be described below with reference to Figure 4 As described. In the hydraulic power assisted steering system as shown in FIG. 1 , hydraulic assistance (not shown in FIG. 1 ) is provided in association with the RCB of the vehicle, and there is a linkage device between the front axle road wheel 127 and the steering wheel 120. The linkage device is composed of a steering column 121, an RCB 123, a pitman arm 124, a tie rod 130' and two tie rods 125' here, and the tie rod 125' is used to steer the two steering arms 135', and the steering arms 135' turn and steer the front wheels 127. It should be noted that there are one or two tie rods for wheel alignment purposes. There are systems with zero, one or two tie rods.

[0046] FIG. 2 is a schematic diagram of another type of steering system 100B′, for which the concepts of the present invention may be implemented, as will be described with reference to FIG. Figure 5 Here, the linkage between the front axle road wheel 127 and the steering wheel 120 consists of a steering column 121, an RCB 123 with hydraulic assistance (not shown), a steering rocker arm 124, a straight tie rod 134" extending essentially in the longitudinal direction of the vehicle in this figure, a steering arm 135", two tie rod arms 131", with a tie rod 130" between them.

[0047] FIG. 3 is a schematic diagram of another steering system 100C′, to which the concept of the present invention may be implemented, as will be referred to in Figure 6Here, the linkage between the front axle road wheel 127 and the steering wheel 120 consists of a steering column 121, an RCB 123 with hydraulic assistance (not shown), a steering rocker arm 124, a straight tie rod 134" extending substantially in the transverse direction of the vehicle in this figure, a steering arm 135"', two tie rod arms 131"', with a tie rod 130"' between the tie rod arms.

[0048] The present invention relies on the fact that there are both left-hand drive and right-hand drive vehicles, which in turn means that there is available packaging volume for the steering gear and steering linkage on each side of the vehicle. Therefore, the basic idea of ​​the present invention is to use one side for an unassisted RCB, which is used to transfer the driver's steering torque from the steering wheel to the road wheels, and regardless of whether the system is set up according to Figure 4 , Figure 5 still Figure 6 , using available packaging volume, to provide electric assist on the passenger side of the vehicle or more generally on the other side (the side opposite to the side on which the RCB is mounted), the RCB being typically mounted on the driver's side of the vehicle.

[0049] Figure 4 1 is a schematic diagram of a power assisted steering system arrangement 100A according to a first embodiment of the present invention. It comprises a steering wheel 120A and a first driver linkage arrangement 10A, which comprises a linkage arrangement similar to the linkage arrangement described with reference to FIG. 1 and is defined here as comprising a steering column 121A, an RCB 123A, a first lever arm (particularly a pitman arm 124A) and a tie rod arrangement, the first lever arm being arranged here on the driver's side of the vehicle. The first lever arm 124A is arranged to transfer the torque applied by the driver via the RCB 123A to the tie rod arrangement, which also forms part of the first linkage arrangement 10A and comprises here a tie rod 130A and two steering tie rods 125A1, 125A2 to steer two steering arms 135A1, 135A2, which turn and steer the front wheels 127A, 127A. Here, the first lever arm 124A is arranged to transfer the driver torque to the tie rod 130A. The RCB 123A and the first lever arm (eg, pitman arm 124A) are interconnected by means of a spline connection or any other fixed connection.

[0050] The power assisted steering arrangement 100A comprises an assist actuator 30A which is here located on the passenger side of the vehicle, or more generally on the side where no (unassisted) RCB 123A is provided, or in short on the side opposite to where the RCB 123A is located, where space is available.

[0051] The power-assisted steering system arrangement 100A further comprises a second linkage arrangement 20A (also indicated as auxiliary actuator linkage arrangement) for transmitting auxiliary actuator torque from the auxiliary actuator 30A to the first linkage arrangement 10A, here to the tie rod 130A, which, as described above, is the link that steers the front axle wheels 127. The second or auxiliary actuator linkage arrangement 20A comprises here an auxiliary arm 145A, which is arranged between the auxiliary actuator 30A, the steering actuator and the tie rod 130A.

[0052] In addition, the steering column 121A incorporates a torsion bar 128A having a torque sensor for measuring the steering torque applied by the driver. The assist torque is actuated by a steering assist actuator 30A, which comprises at least an electric assist motor 115A and an ECU 110A, and optionally also an auxiliary gear 140A. The auxiliary gear 140A, if any, is then connected to an auxiliary arm 145A by means of a spline connection or any other fixed connection.

[0053] Control of the assist actuation level in the steering assist actuator 30A is controlled by the control system in the ECU 110A.

[0054] In order to control the assist of the assist actuator 30A, a torsion bar 128A with a torsion bar torque sensor is installed in the RCB 123A on the steering wheel side, between the RCB 123A and the steering column 121 A. The sensed value (torsion bar torque) in the torsion bar 128A is then sent to the ECU 110A, which is attached to or near the electric motor 115A, via a communication device (such as a signal bus or the like).

[0055] The control of the motor is performed as follows: The torsion bar torque is measured in the RCB or steering column by using a well-known torsion bar torque sensor. The sensed torsion bar torque value sent to the ECU 110A via a communication device (such as a signal bus or the like) is used in the ECU to calculate the target torque of the motor. Optionally, several other sensed values ​​such as, for example, steering wheel angle, motor angle, vehicle speed can be used in the calculation of the target assist torque. This target torque is then actuated by using a torque controller well known to those skilled in the art.

[0056] The auxiliary gear 140A (if any) is a reduction gear, wherein the output shaft of the reduction gear is mounted to a second lever arm including an auxiliary arm 145A, so that the auxiliary arm 145A will be subjected to an auxiliary torque (just as the steering rocker arm 124A is usually when hydraulic assistance is implemented). The reduction gear between the electric auxiliary motor 115A and the auxiliary arm 145A is typically arranged in the form of a sector worm gear or a spur gear, because the angular range of the auxiliary arm 145A is very small and the transmission ratio is very high, so the output gear will be very large, but the rotation is very small, so that only a small sector of the gear will be used, hence the name sector gear. For the sector gear, the unused portion of the output gear is removed. By using a sector gear, the packaging volume will be small even if the radius of the sector gear is large. In addition, the ratio of the reduction gear will make the size of the motor smaller compared to an embodiment without any reduction gear.

[0057] In some embodiments, the auxiliary actuator may include an auxiliary RCB.

[0058] By reference Figure 4 The solution described makes electric power assisted steering of heavy trucks possible and provides an arrangement that allows easy packaging by using the packaging volume of the RCB that can be used for both left-hand drive and right-hand drive vehicles. With this solution, both spaces (i.e. the space on each side of the vehicle) will be utilized and a very simple and cost effective solution is provided.

[0059] Figure 5 2 is a schematic diagram of an alternative steering system 100B according to a second embodiment of the invention, in which the concepts of the invention are implemented. The system includes a steering wheel 120B and a first linkage arrangement 10B (also referred to as a driver linkage arrangement), which includes a linkage arrangement similar to the linkage arrangement described with reference to FIG. 2 and includes a front axle road wheel ( Figure 5 The first linkage arrangement 10B is defined here as comprising a steering column 121B, an RCB 123B, a first lever arm (here for example a steering rocker arm 124B), Figure 5 The invention relates to a tie rod arrangement including a straight tie rod 134B extending substantially in the longitudinal direction of the vehicle, a driver-side steering arm 135B1 and two (driver-side and passenger-side) tie rod arms 131B1, 131B2, with the tie rod 130B located between the two tie rod arms. The RCB 123B and the first lever arm (e.g., the pitman arm 124B) are interconnected by means of a spline connection or any other fixed connection.

[0060] The power assisted steering arrangement 100B comprises an auxiliary actuator 30B which is here located on the passenger side of the vehicle, or more generally on the side where the RCB 123B is not located, or in short on the side opposite to the side where the RCB 123B is located, where space is available.

[0061] The power assisted steering system arrangement 100B further comprises a second linkage arrangement 20B (also indicated as auxiliary actuator linkage arrangement) for transferring auxiliary actuator torque from the auxiliary actuator 30B to the first linkage arrangement 10B, here to the tie rod arrangement, more specifically to the passenger side tie rod arm 131B2.

[0062] In this embodiment, the second linkage arrangement 20B includes an auxiliary arm 145B, an auxiliary steering rod 150B, and a passenger side steering arm 135B2 connected or hinged to the passenger side tie rod arm 131B2 of the first linkage arrangement 10B.

[0063] Thus, the linkage between the electric auxiliary motor 115B and the passenger side steering arm 135B2 consists of the auxiliary arm 145B, the auxiliary steering rod 150B and the passenger side steering arm 135B2 and optionally the auxiliary gear 140B. The auxiliary gear 140B, if present, is then connected to the auxiliary arm 145B, usually by means of a spline connection or any other fixed connection. The linkage between the wheels comprises a tie rod arrangement, which comprises a tie rod 130B and two tie rod arms 131B1, 131B2.

[0064] In addition, the steering column 121B incorporates a torsion bar 128B having a torque sensor for measuring the steering torque applied by the driver. The auxiliary torque is actuated by a steering assist actuator 30B, which includes at least an electric assist motor 115B and an ECU 110B, and optionally (but not necessarily) includes an auxiliary gear 140B. The control of the auxiliary actuation level in the steering assist actuator is controlled by a control system in the ECU 110B. In some embodiments, the auxiliary actuator may include an auxiliary RCB.

[0065] In order to control the assistance of the assist actuator 30B, a torsion bar 128B with a torsion bar torque sensor is installed in the (non-assist) RCB 123B on the steering wheel side, between the RCB 123B and the steering column 121B. The sensed value (torsion bar torque) in the torsion bar 128B is then sent via a communication device (such as a signal bus or the like) to the ECU 110B, which is attached to or close to the electric motor 115B, as also referred to in Figure 4 The embodiments are discussed further herein.

[0066] In reference Figure 5In an alternative to the second embodiment described, the tie rod may be arranged directly between the two pitman arms. In this alternative to the second embodiment, the first or driver linkage arrangement is formed by the pitman arm and the straight tie rod, and the second (auxiliary actuator) linkage arrangement includes the auxiliary arm 145B and the auxiliary pitman rod 150B.

[0067] By reference Figure 5 The solution described, and any variants thereof, makes possible electric power assisted steering of heavy trucks and provides an arrangement which allows easy packaging using the packaging volume of the RCB which can be used for both left-hand drive vehicles and right-hand drive vehicles. Both spaces, i.e. the space on each side of the vehicle, will be used and a very simple and cost effective solution is provided.

[0068] Figure 6 1 is a schematic diagram of a power assisted steering system arrangement 100C according to a third embodiment of the present invention. The system comprises a steering wheel 120C and a first linkage arrangement 100C (also referred to as a driver linkage arrangement) comprising a linkage arrangement similar to the linkage arrangement described with reference to FIG. 3 and comprising a front axle road wheel ( Figure 6 The first linkage arrangement 10C is defined here as comprising a steering column 121C, an RCB 123C, a first lever arm (here for example a steering rocker arm 124C), Figure 6 The straight tie rod 134C extending substantially in the transverse direction of the vehicle, including the transverse tie rod 130C (with or without Figure 6 The RCB 123C and the first lever arm (eg, the pitman arm 124C) are interconnected by means of a spline connection or any other fixed connection.

[0069] The power assisted steering arrangement 100C comprises an assist actuator 30C which is here located on the passenger side of the vehicle, or more generally on the side where no RCB is provided, or in short on the side opposite to where the (unassisted) RCB 123C is located, where space is available.

[0070] The power assisted steering system arrangement 100C also includes a second linkage arrangement 20C (also indicated as auxiliary actuator linkage arrangement) for transferring the auxiliary actuator torque from the auxiliary actuator 30C to the first linkage arrangement 10C, here to the pitman arm 124C. In this embodiment, the second linkage arrangement 20C includes an auxiliary arm 145C, an auxiliary steering rod 150C and optionally an auxiliary gear 140C. The auxiliary gear 140C (if any) is then connected to the auxiliary arm 145C by means of a spline connection or any other fixed connection. In some embodiments, the auxiliary actuator may include an auxiliary RCB.

[0071] according to Figure 6 In the embodiment of the invention disclosed in , the steering column 121C incorporates a torsion bar 128C having a torque sensor for measuring the steering torque applied by the driver.

[0072] The assist torque is actuated by a steering assist actuator 30C, which comprises at least an assist motor 115C and an ECU 110C and optionally an assist gear 140C. The control of the assist actuation level in the steering assist actuator 30C is controlled by a control system in the ECU 110C. As described above, the second linkage arrangement 20C (or the linkage between the electric motor 115C and the steering rocker arm 124C) consists of an assist arm 145C and an auxiliary steering rod 150C between the assist arm 145C and the steering rocker arm 124C, wherein the linkage between the wheels is also covered in this embodiment by a tie rod 130C and two steering arms 135C1, 135C2.

[0073] In an alternative implementation to the third embodiment (not shown), two tie rod arms are added and the tie rod moves to act between the two tie rod arms.

[0074] The first linkage arrangement 10C is also referred to as the driver linkage arrangement, which includes a linkage arrangement similar to the linkage arrangement described with reference to FIG. 3 and includes a linkage arrangement between the front axle road wheel (not shown) and the steering wheel 120C. The first linkage arrangement is defined here as including a steering column 121C, an RCB 123C, a first lever arm (here, for example, a pitman arm 124C), Figure 6 A straight tie rod 134C extending substantially in the transverse direction of the vehicle, a tie rod arrangement including a driver-side steering arm 135C1 and two (driver-side and passenger-side) tie rod arms, with the tie rod 130C located between the two tie rod arms.

[0075] The power assisted steering system arrangement 100C further comprises a second linkage arrangement 20C (also indicated as auxiliary actuator linkage arrangement) for transferring auxiliary actuator torque from the auxiliary actuator 30C to the first linkage arrangement 10C, here to the tie rod arrangement, more specifically to the passenger side tie rod arm.

[0076] In this embodiment, the second linkage arrangement 20C includes an auxiliary arm 145C, an auxiliary steering rod 150C, and a passenger side steering arm 135C2 connected or hinged to the passenger side tie rod arm of the first linkage arrangement 10C.

[0077] Furthermore, by this embodiment and its variations, electric power assisted steering for heavy trucks can be provided and an arrangement is provided which would be possible to package easily within the packaging volume of an RCB which could be used for both left-hand drive and right-hand drive vehicles and both spaces would be used, thus providing a very simple and cost effective solution.

[0078] It should be understood that the concepts of the present invention are applicable to systems having one or two tie rods, or systems having no tie rods, and are not limited to the specifically illustrated embodiments, which may be modified accordingly.

[0079] It is clear that the invention is not limited to the specifically shown embodiments but can be varied in many ways within the scope of the appended claims.

Claims

1. A power-assisted steering system arrangement (100B) for a vehicle, comprising: - Steering wheel (120B), - a first driver linkage arrangement comprising a linkage between the steering wheel (120B) and the front axle roadwheel of the vehicle, the linkage comprising: - a steering column (121A; 121B; 121C), - a recirculating ball joint RCB (123A; 123B; 123C) arranged or mounted on a first side of the vehicle, the first side being the frame side, - a tie rod arrangement for steering the front axle road wheels, - a first lever arm arranged to transfer a torque applied by the driver via the steering wheel (120B) to the tie rod arrangement, thus providing a connection directly or indirectly between the RCB (123A; 123B; 123C) and the tie rod arrangement, - at least one torsion bar (128A; 128B; 128C) having a torsion bar torque sensor associated with or incorporated into the steering column (121A; 121B; 121C), Characterized in that the steering system arrangement further comprises: an auxiliary actuator arranged or mounted on a second side of the vehicle, the second side being opposite to the side of the vehicle on which the RCB (123A; 123B; 123C) is arranged or mounted, the auxiliary actuator comprising at least an electric motor (115A; 115B; 115C) and an electronic control unit (ECU) (110A; 110B; 110C) which controls the electric motor according to a control signal received from the torsion bar torque sensor, and - an auxiliary actuator linkage arrangement (20A; 20B; 20C) connected to the tie rod arrangement, so that a steering torque applied by the driver and an auxiliary actuator torque provided or applied by the auxiliary actuator are transmitted to the tie rod arrangement which steers the front axle road wheels of the vehicle, wherein the first driver linkage arrangement comprises a straight tie rod (134B) arranged between the first lever arm and the tie rod arrangement and extending substantially in the longitudinal direction of the vehicle, and the tie rod arrangement comprises a tie rod pivotally connected to each end of a first tie rod arm (131B1) and a second tie rod arm (131B2), respectively, and a first steering arm (135B1), the first lever arm being connected to the tie rod and being arranged to transfer the driver torque via the straight tie rod (134B) and the first tie rod arrangement The steering arm (135B1) is transmitted to the transverse tie rod (130B), and the auxiliary actuator linkage arrangement (20B) includes an auxiliary arm directly or indirectly connected to the auxiliary actuator (30B) at one end, an auxiliary steering rod pivotally connected to the other end of the auxiliary arm (145B), and a second steering arm connected to the other end of the auxiliary steering rod (150B). The auxiliary actuator linkage arrangement (20B) is therefore arranged to transmit the auxiliary torque from the auxiliary actuator (30B) to the transverse tie rod (130B).

2. The steering system arrangement (100B) according to claim 1, It is characterized in that The first lever arm includes a pitman arm.

3. The steering system arrangement (100B) according to claim 1 or 2, It is characterized in that The auxiliary actuator also includes a gear (140A; 140B; 140C).

4. The steering system arrangement (100B) according to claim 3, It is characterized in that The gear (140A; 140B; 140C) is arranged between the electric motor (115A; 115B; 115C) and the auxiliary arm (145A; 145B; 145C).

5. The steering system arrangement (100B) according to any one of claims 1 to 2, characterized in that: The RCB (123A; 123B; 123C) is arranged on the driver's side of the vehicle, and the auxiliary actuator is arranged on the passenger's side of the vehicle, or vice versa.

6. The steering system arrangement (100B) according to claim 1, It is characterized in that The tie rod (130B) on each end is pivotally connected to a first tie rod arm (131B1) and a second tie rod arm (131B2), respectively, the first tie rod arm (131B1) being connected to the first steering arm (135B1) of the first driver linkage arrangement, and the second tie rod arm (131B2) being connected to the second steering arm (135B2) of the auxiliary actuator linkage arrangement (20B).

7. The steering system arrangement according to claim 1, It is characterized in that The tie rod is arranged between and directly connected to the first steering arm of the first driver linkage arrangement and the second steering arm of the auxiliary actuator linkage arrangement.

8. A steering system arrangement (100C) for a vehicle, comprising: - Steering wheel (120C), - a first driver linkage arrangement comprising a linkage between the steering wheel (120C) and the front axle roadwheel of the vehicle, the linkage comprising: - a steering column (121A; 121B; 121C), - a recirculating ball joint RCB (123A; 123B; 123C) arranged or mounted on a first side of the vehicle, the first side being the frame side, - a tie rod arrangement for steering the front axle road wheels, - a first lever arm arranged to transfer a torque applied by the driver via the steering wheel (120C) to the tie rod arrangement, thus providing a connection directly or indirectly between the RCB (123A; 123B; 123C) and the tie rod arrangement, - at least one torsion bar (128A; 128B; 128C) having a torsion bar torque sensor associated with or incorporated into the steering column (121A; 121B; 121C), Characterized in that the steering system arrangement further comprises: an auxiliary actuator arranged or mounted on a second side of the vehicle, the second side being opposite to the side of the vehicle on which the RCB (123A; 123B; 123C) is arranged or mounted, the auxiliary actuator comprising at least an electric motor (115A; 115B; 115C) and an electronic control unit (ECU) (110A; 110B; 110C) which controls the electric motor according to a control signal received from the torsion bar torque sensor, and - an auxiliary actuator linkage arrangement (20A; 20B; 20C) connected to the tie rod arrangement such that a steering torque applied by the driver and an auxiliary actuator torque provided or applied by the auxiliary actuator are transmitted to the tie rod arrangement which steers the front axle road wheels of the vehicle; Wherein, the first driver linkage arrangement (10C) also includes a straight tie rod (134C), which is arranged between the first lever arm (124C) and the transverse tie rod arrangement, and the transverse tie rod arrangement includes a transverse tie rod (130C) on the outer ends respectively connected to the first steering arm and the second steering arm (135C2), and the auxiliary actuator linkage arrangement (20C) includes an auxiliary arm (145C) directly or indirectly connected to the auxiliary actuator (30C) at one end, an auxiliary steering rod (150C) pivotally connected to the other end of the auxiliary arm (145C), and the auxiliary steering rod (150C) is connected to the first lever arm (124C) of the first driver linkage arrangement (10C) at its other end, and the auxiliary actuator linkage arrangement (20C) is therefore arranged to transmit the auxiliary torque from the auxiliary actuator (30C) to the first driver linkage arrangement via the first lever arm (124C).

9. The steering system arrangement (100C) according to claim 8, It is characterized in that The first lever arm includes a pitman arm.

10. The steering system arrangement (100C) according to claim 8 or 9, It is characterized in that The auxiliary actuator also includes a gear (140A; 140B; 140C).

11. The steering system arrangement (100C) according to claim 10, It is characterized in that The gear (140A; 140B; 140C) is arranged between the electric motor (115A; 115B; 115C) and the auxiliary arm (145A; 145B; 145C).

12. The steering system arrangement (100C) according to claim 8 or 9, characterized in that: The RCB (123A; 123B; 123C) is arranged on the driver's side of the vehicle, and the auxiliary actuator is arranged on the passenger's side of the vehicle, or vice versa.

13. A steering system arrangement according to claim 8 or 9, It is characterized in that The tie rod is pivotally connected at each end to respective first and second tie rod arms, which are connected to the first and second steering arms, respectively.

14. The steering system arrangement (100C) according to claim 8 or 9, It is characterized in that The vehicles include heavy vehicles.

15. The steering system arrangement according to claim 10, It is characterized in that The gear (140A; 140B; 140C) comprises a sector worm gear or a spur gear.

16. A steering system arrangement according to claim 8 or 9, It is characterized in that The straight tie rod (134C) extends in a substantially transverse direction of the vehicle.

17. The steering system arrangement according to claim 14, It is characterized in that The heavy vehicle includes a truck or a large pickup truck.

18. A steering system arrangement according to claim 8 or 9, It is characterized in that The auxiliary actuator also includes an auxiliary RCB.

Images