<<BACK TO PREVIOUS

Breather valve cuts pressure losses

A valve for crankcase ventilation pressure regulation is being developed by Mann & Hummel and will replace the Flatline type when it enters production. It is claimed to offer reduced pressure loss, reduced hydrocarbon (HC) emissions, more compact dimensions and lower cost.

The pressure of blow-by gases in the crankcase should be kept as constant as possible, regulation of which requires a valve. This design uses a Bourdon tube both as a pressure sensor and actuator.

One end of the plastic tube is attached to the moulded valve housing and is open to atmospheric pressure. A pivoted slide regulator is fitted to the other end. A spring between the tube and the housing sets the desired pressure and accounts for changes in temperature. Expansion of the tube transfers a torque against the spring, moving the regulator and therefore changing the cross section of the valve. This maintains pressure in the crankcase irrespective of the vacuum in the inlet manifold.

Reduced pressure loss in the valve makes it simpler to hold crankcase pressure within the desired tolerance.

Eliminating the rubber membrane used in the Flatline design brings several benefits: reduced component and assembly costs; HC emissions are reduced because they cannot permeate the nylon housing or the valve; valves can be commonised for both petrol and diesel engines (membrane materials can differ depending on fuel type).