Lotus Evora Service Notes page 172

Lotus Service Notes
Splines to
intermediate
shaft
Hydraulic seal
Roller bearing
Valve body
Sealing rings
Ball bearing/seal
Pinion gear
The steering column is clamped to splines on the top end of the rack input shaft, the lower end of which
is machined to form a valve rotor, turning within the valve sleeve. The valve sleeve is fixed to the pinion gear
and contains hydraulic ports which are controlled by the position of the rotor relative to the sleeve. The rotor
and sleeve are connected by the torsion bar, the top end of which is secured inside the top end of the hollow
input shaft (rotor), and the bottom end splined into the pinion gear (sleeve). The degree of twist of the torsion
bar is determined by the force applied at the steering wheel, and is proportional to the loading at the front tyres.
These forces tend to be highest when manoeuvering at low speed (e.g. parking) and result in the greatest
angular displacement between valve rotor and sleeve.
The valve body incorporates 4 ports:
- inlet from the engine driven pump;
- outlet (return) to the reservoir;
- connection to the right hand rack cylinder;
- connection to the left hand rack cylinder.
Page 4
Section HI
Connection pin
Input shaft/valve rotor
Torsion bar
Outlet to reservoir
To/from rack cylinder 1
Inlet from pump
To/from rack cylinder 2
Valve sleeve
Torsion bar splined
to sleeve/pinion
h61