Power assisted steering system arrangement

Abstract

The present invention relates to a power assisted steering system arrangement (100A) for a vehicle comprising a steering wheel (120A), and a first driver link arrangement (10A) which comprises a linkage between the steering wheel (120C) and front wheels (127,127) comprising a steering column (121A), a recirculating ball joint (RCB) (123A) arranged on a first side of the vehicle, a track rod arrangement for steering the front wheels (127,127), and a first lever arm (124A) arranged to transfer the torque applied by a driver via the steering wheel to the track rod arrangement and providing a connection between the RCB (123A) and the track rod arrangement. The system further comprises a torsion bar (128A) with a torsion-bar torque sensor associated with the steering column (121A); an assistance actuator (30A), arranged on a second side of the vehicle, opposite to the side of the vehicle where the RCB is arranged, the assistance actuator (30A) comprising at least an electric motor (115A) and an electronic control unit (ECU) (110A) controlling the electric motor depending on control signals received from the torsion-bar torque sensor; and an assistance actuator link arrangement (20A) connected to the track rod arrangement, so that a steering torque applied by the driver as well as an assistance actuator torque provided or applied by the assistance actuator (30A) is transferred to the track rod arrangement steering the front wheels of the vehicle.

Description

technical field [0001] The invention relates to a power assisted steering arrangement having the features of the first part of claim 1 . Background technique [0002] For heavy duty trucks or large pickup trucks there is no room for the rack and pinion steering normally used in passenger cars where the steering rack is mounted on the subframe which for heavy vehicles does not exist. Therefore, for heavy vehicles, especially for heavy trucks, other solutions must be used. A recirculating ball gearbox (RCB), steering rocker arms, tie rods and two tie rods are typically used to steer the two steering arms that turn and steer the front wheels of the vehicle. [0003] An example of one such prior art steering system layout is shown in Figure 1 of the present application, which is also described further below. [0004] Another prior art steering system layout is shown in FIG. 2 . Here, the steering rocker does not directly affect the tie rods. Instead, there is a linkage to t...

AI Technical Summary

Problems solved by technology

[0011] However, while hydraulic systems have high power density and are easy to fit in RCBs, the same is not true for electric motors with gearboxes

Without hydraulics, an unassisted RCB would be slightly smaller, but the size reduction isn't even close to what would be required to mount an electric motor with a reduction gear on it and provide the same amount of assist as a conventional hydraulic assisted system degree

[0012] Therefore, in many cases, there is not enough packaging volume available to fit electric motors with reduction gears, which is a serious problem and constitutes an obstacle to the introduction of electrically assisted RCBs

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