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Steering Torque Sensor
Electronic power steering (EPS) has enabled benefits to the automotive world such as light-weighting of technologies, increasing efficiency and reducing complexity and cost. A key component to operating the EPS system is the torsion bar. When the vehicle operator turns the steering wheel, the torsion bar twists and this displacement is used to determine the level of input torque. The electronic control unit (ECU) then uses this information to ensure the correct output torque is applied. A schematic of this system can be seen in Figure 1.
Figure 1: A Schematic diagram of where the torsion bar is used in an EPS system. The bearing highlighted in red is where the bushing sits.
Commonly, needle bearings are used in this application. The torsion bar twists inside the needle bearing and if vibrations are present in the system, the interface between the needle bearings and the torsion bar will cause a buzzing feeling in the steering wheel.
Figure 1: A Schematic diagram of where the torsion bar is used in an EPS system. The bearing highlighted in red is where the bushing sits.
Commonly, needle bearings are used in this application. The torsion bar twists inside the needle bearing and if vibrations are present in the system, the interface between the needle bearings and the torsion bar will cause a buzzing feeling in the steering wheel.
Smart Design Engineered Benefits for Steering Feel (Torsion Bar)
- Without the use of a NORGLIDE® Bearing, shaft & housing bore surfaces must be heat treated to prevent brinelling
- Don’t need to be heat treated to increase hardness
- Greater load capacity
Perfect Fit Engineered Benefits for Steering Feel (Torsion Bar)
- Relaxed tolerances on mating components can be used
- Do not need precision ground surfaces that are required for needle bearings to ensure smooth operation
- Drop in replacements in some applications
Noise Free Engineered Benefits for Steering Feel (Torsion Bar)
Figure 2 shows how the sound pressure level (SPL) of the “buzz” caused by vibrations between the torsion bar and the needle bearing can be reduced by using a single NORGLIDE® Bearing. The overall level has been reduced from 40.3 dB(A) for needle bearings to 36.2 dB(A) for a NORGLIDE® Bearing.
Figure 2: Sound pressure levels (SPL) for the current solution and the NORGLIDE® solution during radial excitation of the torsion bar at 15 Hz and 2.3 m/s2. Overall levels; current solution = 40.3 dB(A), NORLGIDE® = 36.2dB(A).
Figure 2: Sound pressure levels (SPL) for the current solution and the NORGLIDE® solution during radial excitation of the torsion bar at 15 Hz and 2.3 m/s2. Overall levels; current solution = 40.3 dB(A), NORLGIDE® = 36.2dB(A).
Figure 3 shows how the sound pressure level (SPL) of the rotational rattle noise can also be reduced by the use of a single NORGLIDE® Bearing. The overall level has been reduced from 33.0 dB(A) for needle bearings to 25.7 dB(A) for a NORGLIDE® Bearing.
Figure 3: Sound pressure levels (SPL) for the current solution and the NORGLIDE® solution for rotational excitation at 15 Hz and 2.3 m/s2 of the constrained torsion bar resulting in a backlash test for the gear teeth. Overall levels; current solution = 33.0 dB(A), NORLGIDE® = 25.7 dB(A).
Figure 3: Sound pressure levels (SPL) for the current solution and the NORGLIDE® solution for rotational excitation at 15 Hz and 2.3 m/s2 of the constrained torsion bar resulting in a backlash test for the gear teeth. Overall levels; current solution = 33.0 dB(A), NORLGIDE® = 25.7 dB(A).
Long Life Engineered Benefits for Steering Feel (Steering Torque Sensor)
- No grease required
- No brinelling due to metal-on-metal contact
- No parts to become dislodged as with roller elements in needle bearing