Back in the day—before the invention of the cell phone, the personal computer, or even the color television—nearly all production cars had manual steering. The setup primarily relied on the driver’s muscles to turn the car’s front wheels back and forth via the steering wheel.
Fortunately, all modern cars have the convenience of power steering. The technology makes the steering system easier to operate, creating a more enjoyable (and far less taxing) driving experience for whoever is behind the wheel.
What is Power Steering?
All modern cars have power steering—a feature that assists the driver in turning the front wheels. The power steering system makes the steering wheel easier to turn by augmenting the force the driver exerts on the vehicle’s mechanical steering gear.
Most vehicles have either electric power steering (EPS) or hydraulic power steering. There are also a few models that use an electro-hydraulic system, which combines elements of both the EPS and hydraulic designs.
Electronic Power Steering
EPS, which is found in nearly all new cars, uses an electric motor to act on the steering gear and provide steering assist. A typical EPS system includes the following power steering components:
Steering Gear (Rack and Pinion Assembly)
The steering gear contains a set of gears that transfer input from the steering column shaft (and the steering wheel) to the steering linkage. From there, the steering linkage connects to the steering knuckles, which, in turn, attach to the wheels and tires. All of the components working together cause the wheels to move in or out in response to the driver’s input.
An electric motor (mounted on either the steering column or steering rack) is the focal point of the EPS system. The motor applies the force needed to turn the steering gear and provide the driver with steering assist. Depending on the system design, the motor may operate on 12 volts (like most automotive electrical components) or 48 volts.
A computer, which is often referred to as the EPS control module, operates the steering motor based on input from the steering system sensors. To retrieve additional information regarding vehicle operation, the EPS module also communicates with other onboard modules over a data network.
The steering wheel sensor, which is usually an angle sensor and a torque sensor integrated into a single assembly, is the primary input to the EPS module. There’s also a sensor that relays the position of the motor back to the EPS module.
The video below demonstrates electronic power steering system operation:
Hydraulic Power Steering
Many vehicles on the road today still have hydraulic power steering. The design uses an engine-driven pump and hydraulic fluid to provide steering assist. A typical hydraulic system includes the following power steering components:
Steering Gear (Rack and Pinion Assembly or Worm Gear Box)
Hydraulic power steering systems may use either a steering rack and pinion assembly or steering box, depending on the vehicle design. Both types of units contain a set of gears that transfer input from the steering column shaft (and the steering wheel) to the steering linkage.
From there, the steering linkage connects to the steering knuckles, which, in turn, attach to the wheels and tires. All of the components working together cause the wheels to move in or out in response to the driver’s input.
Power Steering Pump
The power steering pump, which is driven off of the engine by a belt, pressurizes the power steering fluid and sends that fluid to the power steering gear. When the pressurized fluid acts on the gear, it makes the steering wheel easier to turn for the driver.
Pressurized hydraulic power steering fluid acts as the medium that applies force to the steering gear. A reservoir—mounted either remotely or on top of the power steering pump—stores the fluid.
A set of hoses (or lines) connect the steering gear to the power steering pump. The hose that carries pressurized fluid from the pump to the gear is called the pressure hose. Meanwhile, the hose that routes fluid from the gear back to the pump is called the return hose.
The video below demonstrates hydraulic power steering system operation:
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