HEMA ENDUSTRI A.S. HATTAT OTOMOTIV PAZARLAMA .A.S.

HHU SERIES STEERING UNITS

HEMA ENDÜSTRİ A.Ş. HATTAT OTOMOTIV PAZARLAMA A.Ş.HHU SERİSİ DİREKSİYON ÜNİTELERİ

ON SYSTEM (Open Center, Non Reaction)Open center steering units have, in neutral position, an internal circuit conveying the fluid directly from pump to tank. Non reaction circuit prevents external forces act on the vehicle wheels from being transmitted to the steering wheel.

SIMPLIFIED SCHEMA

EXAMPLEOPEN CENTERNO REACTION

NEUTRAL POSITION

The oil flow from the pump is conveyed directly to the tank.

EXAMPLEDURING STEERING

OPEN CENTER

Turning the steering wheel the relative movement between shaft and sleeve opens some paths that convey the flow in direction of the metering pump (gerotor) and from the gerotor to the steering cylinders.The oil flow directs to the cylinders is proportional to the movement of the steering wheel.The oil from the cylinder is conveyed to the tank

VALVES SCHEME

Shock valves

Suction valves

Relief valve

Check valve

A Z X H Y …..

Relief valve • • • •Antishock valves • •Suction valves • •Check valve • • • • •

VALVE FUNCTION (Relief valve)The relief valve protects the system against excessive pressure and limits the system pressure while steering. The built-in relief valve also works as a by-pass when the steering cylinder is at the end stroke.

120

130

140

150

160

10 15 20 25 30 35 40 45

Flow Rate

Pre

ssur

e P

-T

SALES DRAWING OF A STEERING UNIT HHU

VALVE FUNCTION (Shock valves)The shock valves protect the steering unit from dangerous pressure peaks and limit the maximum external force on the steering cylinder.

VALVE FUNCTION (Suction valves)The suction valves are designed specifically to prevent cavitation in steering cylinders.

VALVE FUNCTION (Chech valve)The check valve prevent oil from returning through the P-inlet oil port when pressure on the cylinder side is higher than oil pump pressure. Steering wheel kick back is avoided

HHU SERİSİ AÇIK DEVRE REAKSİYONSUZ TİP,ANTİŞOK –ANTİKAVİTASYONVE BASINÇ EMNİYET VALFLİDİREKSİYON ÜNİTELERİ

STEERING UNITS ABOUT OPEN CENTER AND NONREACTION TYPES INCLUDING ANTISHOCK ANTICAVITATIONS