Steering systems

Genesis and application.

The steering system has been an integral part of vehicles since the beginning of automotive history. It plays a key role in ensuring safe and precise directional control. Its tasks include a number of functions which are designed to enable the driver to manoeuvre the vehicle efficiently in different road conditions. The main task of the system is, of course, to implement the vehicle driver's wish to maintain or change the vehicle's path. By turning the steering wheel, this movement is transmitted to the steering wheels (usually the front wheels), allowing the vehicle to turn in the desired direction. The steering system also provides the driver with feedback on road conditions, such as wheel resistance, surface irregularities and tyre grip. This enables him to better assess the road situation and adjust his driving accordingly. The steering system should also minimise the transmission of vibrations and shocks from the road surface to the steering wheel, which increases driving comfort and reduces driver fatigue. In order to provide the driver with greater comfort and reduce the force required to turn the steering wheel, power steering systems have become widespread over time. Initially, these were simple hydraulic power steering designs where the power steering pump was driven from the vehicle's engine. A development of this design is the electro-hydraulic power steering system, which uses an electric motor driven pump (EHPS/EPHS). More recent systems are designs with electric power steering of the transmission or steering column (EPS), which allow a range of additional functions such as lane correction, lane assist and parking assist.

Construction and principle of operation.

A vehicle's steering system consists of several main components:

1. Steering wheel
2. Steering column (electric power steering possible)
3. Steering rack (hydraulic or electric power steering possible)
4. Power steering pump (mechanically or electrically driven)
5. Tie rods and tie rods ends
6. Steering knuckles and suspension components.

Power steering can occur in the configurations listed below.

Hydraulically assisted systems:

• with mechanical pump
• with electro-hydraulic pump

Electrically assisted systems (EPS):

• power steering rack
• power steering column

Electric power steering column.

In this solution, the power of the electric motor is transmitted via a suitable mechanical transmission and clutch to the steering column shaft. The system has an electronic controller that ensures the proper management of the system and the monitoring of its correct operation, i.e. diagnostic functions. A number of input signals recorded by sensors such as a torque sensor on the steering wheel, a steering angle sensor, a vehicle speed sensor and others are required to determine the value of the power steering.

Electric power steering rack.

In these designs, the electric motor is located on or inside the steering rack housing. Through an appropriately selected gear ratio, the movement of the motor transmits the power steering force to a toothed rack located inside the housing. In order to properly manage the operation of the power steering system, the electronic controller receives a number of input signals such as, vehicle speed, steering torque, steering angle and others. The controller also has diagnostic functions and records errors related to system malfunctions.

Hydraulic power steering gear.

Hydraulic fluid (oil) is used to support the movement of the rack, which is supplied to the housing at a sufficiently high pressure. Consequently, part of the steering rack works as a hydraulic cylinder and there is a piston on the rack. Consequently, many components are equipped with a number of suitable seals. An important role is played by the distributor, which contains a valve that directs the hydraulic oil into the corresponding cylinder chamber after just a slight movement of the steering wheel. By virtue of its function, the distributor is also fitted with a number of appropriate seals. The power steering pump, which can be driven mechanically from the combustion engine or electrically, is responsible for generating the high pressure.

Electro-hydraulic pump (EHPS/EPHS).

This type of pump is driven by an electric motor, so its performance is not dependent on the speed of the internal combustion engine. The pump module is usually made up of a number of integrated components such as a fluid reservoir, a high-pressure pump (usually a vane or gear pump), an electronic controller and an electric motor. The electronic controller adjusts the power steering based on several inputs, such as vehicle speed, engine speed and steering sensor readings, among others.

Remanufacturing process.

We are aware of the importance of maintaining appropriate standards and strict quality control in the steering system remanufacturing process due to the direct impact of this system on driving safety. Every component that is remanufactured must be thoroughly inspected for wear, damage and material quality. The use of high-quality spare parts and the precise execution of all remanufacturing procedures are crucial to ensure that the steering system will operate reliably and safely.

As a general rule, the remanufacturing process for each steering component we deal with consists of the following steps:

1. Preliminary verification
2. Cleaning
3. Verification after cleaning
4. Disassembly into components
5. Verification of components
6. Replacement of damaged and critical parts of a component
7. Assembly of components, completion of subassembly
8. Quality control
9. Final diagnostic test
10. Evaluation of functional test results

Remanufacturing of hydraulic power steering gears.

The remanufacturing of a hydraulic power steering gear consists primarily of restoring its tightness. All seals are replaced and all mechanical components are checked for damage or wear and replaced if necessary, including the rack, pinion, distributor, housing, etc. All components of the steering rack are inspected in detail for wear and tear and the presence of mechanical damage such as abrasion or cracks. The degree of wear on the pinion and rack teeth is inspected. The alignment of the rack is also checked. It is often necessary to grind the mating surfaces of the seals very carefully due to local wear or corrosion. Faulty bearings are also replaced. Components qualified for reuse are thoroughly cleaned and all damaged parts are replaced with new ones. After the repair, each steering rack undergoes a test on a dedicated test bench to check its tightness and the power steering force acting on the rack when it moves in both directions.

Remanufacturing of electric power steering (EPS) columns and racks. 

In the case of electrically assisted steering racks or columns, the repair mainly consists of inspecting and replacing defective mechanical and electronic components. Very often the steering sensor is damaged. Replacing the sensor requires precision and the appropriate diagnostic equipment necessary to calibrate it. A problem may also arise in the electronic system that manages the operation of the power steering rack or steering column. Removing this type of fault usually requires replacing the electronic components of the power steering controller. After remanufacturing, the operation of the transmission or steering column is checked on a specially designed diagnostic bench. The test consists of several or more steps, during which the operating conditions of the power steering system are simulated for various driving conditions - car park manoeuvres, city traffic, motorway.

Remanufacturing of electrohydraulic pumps (EHPS/EPHS).

Our equipment also allow us to check the operation of electrically driven pumps, which are components of electro-hydraulic power steering systems. The most common malfunctions of power steering pumps are leaks, reduced performance, noisy operation and mechanical failures. The usual repair of the pump involves replacing a set of seals, bearings and other worn mechanical components. Electrical or electronic components (electric motor, electronic pump controller and others) may also be damaged due to leaks. After remanufacturing, each pump undergoes a performance test on a test bench, during which its operation is simulated corresponding to different vehicle speeds.

Causes and types of damage.

The most common symptoms of power steering failure:

1. Rattling coming from around the vehicle suspension
2. No or limited power steering
3. Less power assist in one direction
4. Hydraulic fluid leaks
5. Noise heard when turning the steering wheel
6. Tendency of the steering wheel to move spontaneously in one direction, instability of the trajectory
7. Vibration felt on the steering wheel
8. Lights on the dashboard

Most common damage: 

1. Mechanical damage in the form of worn teeth, housing, slides, seals.
2. Corrosion of internal components.
3. Damage to the electronics of the power steering controller.
4. Damage to the steering sensor.