New features and modifications
over the Ford Granada
New steering gear for the new steering geometry.
New reservoir and lines.
New height and reach-adjustable steering column.
New steering column remote radio control stalk.
Steering wheels as for MY '94, optionally with speed control buttons
and/or in leather.
Steering Column
Location of the power steering
components according to engine
A Left-hand drive variant
B Right-hand drive variant
1 Power steering fluid reservoir
2 Power steering pump - DOHC engine
3 Steering gear
4 Cooling loop
5 Power steering pump - V6 24V engine
6 Power steering pump - Diesel engine
ZF Servotronic power steering (awaiting
diagram)
The ZF Servotronic is a power steering system the power assistance of which
is controlled electronically according to the vehicle speed.
It is available in conjunction with 24V engines.
Construction
The ZF Servotronic essentially consists of
fluid reservoir (16),
pump with control valve (14 in detail A)
steering gear with valve housing (19, 20)
electronic speedometer (1)
special power steering module (2)
electro-hydraulic transducer (3)
The valve housing accommodates
torsion bar (10)
rotary slide valve (12)
control sleeve (13)
reaction piston (8)
Operation without vehicle speed signal
The torsion bar (10) is connected at the top to the rotary slide valve (12)
and at the bottom to the pinion (20) and the control sleeve (13).
When the steering wheel is turned, the rotary slide valve (12) rotates
together with the pinion (20), control sleeve (13) and reaction piston (8)
in the valve housing (23).
The torsion bar (10) is deformed elastically by the torque transmitted
through the steering column. This produces a radial movement of the rotary
slide valve (12) in relation to the
control sleeve (13). The hydraulic fluid coming from the pump is passed to
the appropriate side of the working piston (24) in the steering gear.
The reaction piston (8) remains inoperative.
Operation with vehicle speed signal
The effect on the working piston (24) remains the same.
The steering module receives a vehicle speed signal from the electronic
speedometer (1) and sends a flow signal corresponding to this speed to the
electro-hydraulic transducer (3).
Depending on this flow signal, the valve in the electro-hydraulic transducer
(3) is opened a greater or lesser amount and opens the hydraulic passages to
the reaction piston (8).
On the inside the reaction piston (8) is connected to the rotary slide valve
(12) by means of three axial ball guides. On the outside it is connected to
the control sleeve (13) by means of a ball thread with four turns.
The axial movement of the reaction piston (8) caused by the action of the
hydraulic fluid is converted by the ball thread into a radial movement which
counteracts the radial movement of the rotary slide valve (12).
The valve housing (23) accommodates the reaction limiting valve (4) which
has the task of limiting the pressure to the reaction piston (8) and
allowing surplus fluid to pass to the return.
