Mitigating High Steering Effort in Power Steering Pumps through Manufacturing Process Improvement

Power steering pumps are the heart of any hydraulic power steering system. They provide the heavy lifting power required in the form of high-pressure fluid flow that is utilized in powered steering gears or steering racks to assist drivers in vehicle maneuvers, specifically in low-speed situations. Failure of the power steering pump will inevitably increase work needed from the driver to steer a vehicle and decrease the driver comfort at the same time. This article covers investigations into a customer return issue, affecting more than 20% of pumps, for one particular failure mode, pump input shaft seal leakage, and how the failure is not caused by failure at the input shaft nor by failure of the input shaft seal. It was found that internal damage to the pump rotating assembly allows high-pressure oil to overcome the input shaft seal sealing effect. The cause of the failure was determined to be rooted in the manufacturing process, which was re-ordered to reduce the failure rate to an acceptable value (<1%).