Bendix: How a Steering Gear Works (BW5071)

Summary

In this video, Mike Boland, Product Manager at Bendix, explains the operation of an eyelet steering gear. He breaks it down into two systems: mechanical and hydraulic. The mechanical system converts the rotation of the steering wheel into linear motion of the rack piston, which turns the output shaft and controls the steering linkage. The hydraulic system assists this process by directing fluid to the appropriate cylinder, providing hydraulic pressure to assist in steering. The video gives a clear and simple overview of how the steering gear enables precise vehicle control, with the support of hydraulic assist.

Takeaways

• 😀 The steering gear consists of two main systems: a mechanical system and a hydraulic system.
• 😀 The mechanical system converts rotational input from the steering wheel into linear motion of the rack piston inside the gear housing.
• 😀 The rack piston moves within the cylinder bore and rotates the output shaft, which is connected to the steering linkage and front wheels.
• 😀 Hydraulic fluid enters the gear through the pressure line in the valve housing, enabling hydraulic assist.
• 😀 The control valve directs hydraulic fluid to either the upper or lower cylinder depending on the required steering direction.
• 😀 The large seal ring around the rack piston separates the upper and lower cylinders, allowing pressure to build up on either side when assist is needed.
• 😀 When assist is needed in the upper cylinder, the control valve directs fluid there, helping push the rack piston to the right.
• 😀 Similarly, when assist is needed in the lower cylinder, the fluid is directed to that chamber, helping push the rack piston to the left.
• 😀 The movement of the rack piston, either to the left or right, produces rotational movement in the output shaft, which then controls the pitman arm and steering linkage.
• 😀 Hydraulic assist from the power steering system provides additional force, making steering easier and more responsive.
• 😀 The interaction between the mechanical and hydraulic systems allows the vehicle's steering to function smoothly, providing power assistance as needed.

Q & A

What are the two primary systems that make up the steering gear?

The steering gear consists of two primary systems: a mechanical system and a hydraulic system.

How does the mechanical system of the steering gear work?

The mechanical system receives input or rotation from the steering wheel. As the input shaft turns, it pushes the rack piston linearly inside the cylinder bore of the gear housing. This motion rotates the output shaft, which is connected to the steering components, ultimately turning the front wheels.

What role does the output shaft play in the steering gear?

The output shaft is rotated by the motion of the rack piston inside the cylinder bore. This rotation controls the movement of the pitman arm, drag link, and steering linkage, which in turn steers the vehicle's front wheels.

How does the hydraulic system assist in steering?

The hydraulic system assists by directing hydraulic fluid into the gear's control valve. The fluid is directed to either the upper or lower cylinder to provide hydraulic assist, which helps to move the rack piston and facilitate easier steering.

What is the function of the seal ring around the rack piston?

The seal ring acts as a barrier between the upper and lower cylinders, allowing pressure to build up on either side. This creates hydraulic assistance for steering, depending on the direction of movement required.

What happens when hydraulic assist is needed in the upper cylinder of the steering gear?

When assist is needed in the upper cylinder, the control valve directs hydraulic fluid into the upper chamber. The pressure builds up against the seal around the rack piston, pushing the rack piston to the right.

How does the hydraulic assist work in the lower cylinder?

When hydraulic assist is needed in the lower cylinder, the control valve directs fluid to the lower cylinder, building pressure on the other side of the seal. This allows the hydraulic assist to push the rack piston to the left.

What is the overall effect of the rack piston’s linear motion in the steering gear?

The linear motion of the rack piston inside the cylinder bore, either to the right or left, produces a rotational movement of the output shaft. This rotation then controls the steering mechanism, turning the vehicle's front wheels.

How does the steering wheel input translate to turning the vehicle?

The rotation of the steering wheel is transferred through the mechanical system, which moves the rack piston inside the gear housing. This motion of the rack piston is converted into rotational movement of the output shaft, which is connected to the steering linkage that turns the vehicle.

What is the role of the control valve in the hydraulic system?

The control valve directs hydraulic fluid to the appropriate side of the gear's cylinder (either upper or lower) based on the direction of steering input. This provides the necessary hydraulic pressure to assist in moving the rack piston.