Overview of Plain Bearings in Dual Mass Flywheels (DMF)

Overview of Plain Bearings in Dual Mass Flywheels (DMF)

Plain bearings, also known as bushings, are simple bearings without rolling elements. They enable relative sliding motion between a shaft and its housing while providing support, reducing friction, and damping vibration. In dual mass flywheels, plain bearings are critical components of the torsional damping system, ensuring smooth engine torque transfer and minimizing vibration.

Key Requirements for DMF Bushings:

• High wear resistance under oscillating or small-amplitude motion

• Low friction coefficient to improve energy efficiency

• High load-bearing capacity to transmit torque effectively

• Resistance to high temperatures typical of engine operation

• Compatibility with lubrication conditions, whether dry or oiled

Cylindrical Bushings

Description:
Cylindrical bushings are straight, tubular components that fit into the bore of the flywheel or hub, allowing a shaft or pin to slide within.

Advantages:

• Simple design and easy to manufacture

• Compact, saving axial space

• Suitable for applications with minimal axial constraints

Material Considerations:

• Self-lubricating composites (e.g., PTFE-based)

• Bronze or copper alloys with oil impregnation

• High-strength polymers for low-load applications

Typical Applications in DMF:

• Torsional damper pin bushings

• Supporting rotational motion between primary and secondary flywheel masses

• Intermediate pins requiring radial load support

Engineering Solutions:

• Material: Self-lubricating bronze (CuSn10, CuSn8) or PTFE composites for maintenance-free operation

• Surface Treatment: Optional solid lubricant coatings (e.g., MoS₂) for improved wear resistance

• Precision Fitting: Tight tolerances to prevent vibration while ensuring smooth sliding

Flanged Bushings

Description:
Flanged bushings are similar to cylindrical bushings but include an integral flange at one end. The flange provides axial positioning, preventing the bushing from sliding out of the bore.

Advantages:

• Handles both radial and moderate axial loads

• Simplifies assembly by eliminating separate retaining parts

• Prevents axial movement under torsional vibrations

Material Considerations:

• Same as cylindrical bushings: bronze or PTFE composites

• Flanges may be reinforced to resist edge wear

Typical Applications in DMF:

• Axial support of torsional damper pins or shafts

• Areas where axial displacement must be controlled to maintain damping performance

Engineering Solutions:

• Material Selection: Bronze or PTFE composites with integral flanges for wear resistance

• Flange Reinforcement: Thicker or slightly protruding flanges for high-load applications

• Fit Design: Press-fit or interference-fit with housing to prevent rotation or displacement

• Lubrication: Self-lubricating materials reduce maintenance; optional oil grooves for heavy-duty DMFs

Cylindrical vs. Flanged Bushings: Key Comparison

Summary:

• Cylindrical bushings: Best for radial load support and compact DMF designs; ideal for damper pins and intermediate shafts.

• Flanged bushings: Provide axial positioning, vibration stability, and edge protection; suitable for torsional damper interfaces where bushing displacement must be strictly controlled.

• Material solutions: Self-lubricating PTFE or oil-impregnated bronze ensures long-term durability in harsh engine environments.