#multi-axle #commercial-vehicle #truck #utility-vehicle #steering-systems

Rear axle steering system

Electro-hydraulic steering assistance for multi-axle vehicles

The electro-hydraulic steering system for rear axles is a stand-alone power-on-demand system. Up to three or even more rear axle steering systems can be used in one heavy commercial vehicle. A hydraulic cylinder unit is combined with an electronic power unit.

Power-on-demand

enables energy-efficient steering through an electronically controlled reversible pump

reduced turning circle

and tire wear thanks to additionally steered axle

Cybersecurity

protection against unauthorized external access in accordance with ISO/SAE 21434

compact design

can be used in all drive concepts

Operating principle

In today's transportation industry, the demands placed on commercial vehicles are increasing. Efficiency and automation are in the foreground. The innovative rear axle steering system, with its product features, electronic interface, and integration into the vehicle electrical system, meets these requirements.

The rear axle steering system consists of two main components: the power unit and the cylinder unit with integrated linear sensor and valve system. The steering angle of the front axle is transmitted via the CAN bus to the control unit of the rear axle steering system. This determines the desired position of the steering angle of the rear axle and controls the electric motor of the pump. The resulting oil flow acts on the respective piston surface of the cylinder unit and retracts or extends the piston rod of the cylinder.

The integrated linear sensor provides feedback when the target position is reached. By connecting the cylinder unit to a wheel steering lever and transmitting the steering forces via the track rod, the wheels of the axle are controlled to the desired steering angle. The compact design offers the possibility of steering several axles by using multiple rear axle steering systems. These are freely programmable and can be installed by plug-and-play. An electronic stop can be programmed to protect the rear axle steering against overload at maximum wheel angle. The control unit regulates the oil flow of the pump as soon as the programmed end stop is reached. This prevents damage to the mechanical stops.

Drag to rotate

Hydraulic cylinder and power unit

The power unit (in the upper part of the illustration) is a combination of electric motor, control unit and pump unit. This controls the steering movement via the directly connected hydraulic cylinder. The interface between steering and vehicle is the CAN-communication and power supply.

Technical data

185 bar

Max. pressure

1,000 mm +/−95 mm

Installed length

24 V DC

Operating voltage

24 kg

Weight

Product benefits

PRODUCT BENEFITS FOR MANUFACTURERS

Compatible with ISO 26262 (Road vehicles – Functional safety)
Prepared for ISO/SAE 21434 (Road vehicles – Cybersecurity)
Low installation effort through plug-and-play integration
Compact construction
Light weight

PRODUCT BENEFITS FOR Drivers

Fuel savings and CO₂ reduction through the “power-on-demand” principle
Small turning circle
Reduced tire wear

Holistic mobility solutions across all domains and vehicle segments.

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Bosch Mobility