Vacuum pumps provide braking assistance (through a brake booster)
and support the supercharging and exhaust gas recirculation. They
contribute to the overall safety and efficiency of the braking
system by reducing the amount of pedal effort required for braking.
Since any failures or deterioration in the performance of a vacuum
pump would have an adverse effect on the braking performance of an
automobile and may even lead to accidents, auto makers have
established stringent requirements for the reliability and
performance of vacuum pumps prior to assembly. The vane type pumps
supply brake boosters with negative pressure of 0.9 bar (1,880
lbs/sq ft) to reduce braking efforts for drivers.
In order to keep the pump vanes working efficiently, they require
high wear resistance in the tip area, low coefficient of friction
particularly for electrical pumps, tight dimensional tolerances,
thermal expansion similar to or slightly greater than aluminum, and
a high strength/weight ratio. In addition, driven by pedestrian
safety legislation, the position of the pumps has moved nearer the
oil sump, meaning that they experience increasing service
temperatures up from 100 to 110°C and 120°C to 130°C (212 to 230°F
and 248 to 266°F).
Selection of materials is critical to the performance and operating
reliability of vacuum pumps. PEEK polymer has excellent resistance
to automotive fluids and has demonstrated a very good compressive
creep resistance at elevated temperatures. It is a unique material
which maintains high mechanical strength at 150°C (302°F) for 5,000
hours or more and resists brittleness when stressed by mechanical
and frictional loads. It withstands the forces generated during
cold starting [-40°C (40°F)]) where the engine oil has a relative
high viscosity. The material's excellent wear resistance results in
a longer service life.
In recent years, the automotive industry has faced increasing
pressure to maximize performance and safety while minimizing fuel
consumption, weight and cost. As a result, high durability, low
cost, driving comfort, and low environmental pollution have become
the core measurements of R&D efforts. HONY Plastics 's
materials and deep technical support are helping automotive part
makers around the world boost product performance, improve design
flexibility, and extend service part life while successfully
meeting the industry's demanding material requirements.