2011 FORD KUGA ECT

General overview
Haldex clutches of the 3rd and 4th generations are
used in the Ford Kuga.
The development of the third generation Haldex
clutch represents a big step forward in modern
all-wheel technology. The Haldex clutch is
electro-hydraulically controlled. Additional
information is taken into consideration during
control tasks via the all-wheel drive control unit.
Slip alone is no longer decisive for the distribution
of the propulsive forces; the vehicle's driving
dynamics are also taken into consideration. The
control unit accesses the driving-related data via
the data bus. With this data, the control unit has
all the essential information about speed, cornering,
coasting or traction operation, and can optimally
react to every driving situation.
Compared with the previous generation, the 4th
generation Haldex clutches operate with higher
pressure and achieve shorter response times when
distributing the drive forces.
Advantages of the Haldex clutch:
• Permanent all-wheel drive withelectronically-controlled multi-plate clutch
• Fast response
• No straining when parking and manoeuvring
• Compatible with different tyres (e.g. emergency spare wheel)
• Fully combinable with driving dynamic control systems
The driveshaft is connected to the input shaft of
the Haldex clutch. Within the Haldex clutch, the
input shaft is separated from the output shaft to
the rear axle differential by means of a multi-plate
clutch. Torque is only transmitted to the rear axle
differential when the plate assembly of the Haldex
clutch is closed.
The multi-plate clutch is electro-hydraulically
controlled via the all-wheel drive control unit. For
ecological driving, the torque to the rear axle is reduced to a minimum up to a throttle position of
approx. 50%. A prerequisite for this is that there is
no difference in speed in the Haldex clutch between
the input and output shafts.
Operation
E100645
16
3
25
4
Description
Item
Output shaft
1
Working piston
2
Plates
3
Ring piston pump
4
Control Valve
5
Input shaft
6
Within the Haldex clutch is a plate assembly and
a so-called ring piston pump with a pump plunger
and a working piston.
Fluid supply is started if there is a speed difference
between the input and output shafts.
This fluid pressure is transmitted to the working
piston and in this way the plate assembly is
compressed.
Design of the 3rd generation Haldex
clutch
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E100664
1
3
4
11
11
10
9
8
76
5
2
Description
Item
Multiplate clutch
1
Ring piston pump
2
All-wheel drive control unit
3
Pressure relief valve (high pressure)
4
Input shaft
5Description
Item
Electric feed pump
6
Fluid filter
7
Pressure accumulator
8
Pressure relief valve (low pressure)
9
Preload valve
10
High-pressure valves
11
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The Haldex clutch is based on the principle of a
simple wet clutch that distributes the torque variably
between the front and rear axles.
Three components are linked within the Haldex
clutch:• A mechanical component, comprising input and
output shafts, the plate assembly (clutch) as
well as the cam plate and the roller bearing.
• A hydraulic component, essentially comprising pressure valves, a pressure accumulator, the
control valve, the ring pistons and a fluid filter.
• The electronic control comprises the electric fluid pump and the all-wheel drive control unit
with integrated pressure/temperature sensor
and an actuator motor for the control valve.
Design of the multi-plate clutch
7
4
3
2
8
1
6
10911
13
A
B12
5
E100662
Description
Item
Pump plunger assembly
A
Working piston assembly
B
Output shaft
1
Inner plates
2
Outer plates
3
Disc drum
4
Contact plate
5Description
Item
Input shaft
6
Cam disc
7
Springs
8
Pump plunger roller
9
Pump plunger roller
10
Pump plunger
11
Working piston roller
12
Working piston
13
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All-wheel drive control unit
E100663
14
3
2
5
Description
Item
Electronic Control Unit
1
Control valve
2
Pressure/temperature sensor
3
Electrical connection CAN (controller area
network) databus
4
Electric feed pump connection
5
The all-wheel drive control unit is bolted directly to
the housing of the Haldex clutch.
It forms one unit made up of the control valve, a
pressure/temperature sensor, and a control
module. It receives signals from the PCM and from
the ABS control module via the CAN data bus. The
control module in the control unit uses these
signals to determine the fluid pressure that is
needed to actuate the clutch plates depending on
the requirement. This determines how much torque
should be transmitted to the rear wheels. All-wheel
drive is deactivated if a fault occurs in the all-wheel
drive control unit.
A preload of approx. 80 Nm is always present at
the Haldex clutch. The temperature sensor of the Haldex clutch is
installed near the control valve in the control unit
and is surrounded by the hydraulic fluid. The
temperature is transmitted to the control module
and is used for adaptation to the changing viscosity
of the hydraulic fluid. If the hydraulic fluid is cold,
the control valve has to be opened slightly more
than requested. This allowance has to be reduced
as the temperature increases. The normal working
temperature of the hydraulic fluid is between +40
°C and +60 °C. If the temperature rises above 100
°C, the clutch is depressurised; if the temperature
falls below 95 °C, the clutch is pressurised again.
All-wheel drive is deactivated and a diagnostic
trouble code set if a fault occurs in the temperature
sensor.
With Haldex Generations I and II, the control valve
was actuated via a stepper motor. With Haldex
Generation III, the stepper motor has been omitted.
The control valve is now actuated via a solenoid
valve. The solenoid valve is actuated by the control
module in the all-wheel drive control unit by means
of pulse width modulation. The pulse width
modulation determines the position of the
adjustment spindle and thus the opening cross
section of the return hole. This is how the pressure
at the working piston of the plates is determined.
If the return hole is fully closed, maximum pressure
is applied to the plates. If the return hole is fully
open, the plates are unpressurized.
Electric feed pump
The electric feed pump is installed in the clutch
unit. It works according to the gerotor principle.
The main purpose of the feed pump is to fill the
pressure accumulator and the space behind the
pump plunger with hydraulic fluid, thereby ensuring
a fast response time of the Haldex clutch. The feed
pump used in the third generation is designed to
achieve an even higher pressure than the base
pressure of 4 bar. It is supplied with current by the
control module in the all-wheel drive control unit
when the engine is running above approx. 400 rpm.
Pressure control - 3rd generation
Haldex clutch
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Rear Drive Axle/Differential
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E100539
34
2
1
9
8
10
7
6
5A
B
C
D
Description
Item
Barometric Pressure
A
Base pressure
B
Increased base pressure (preload)
C
Operating pressure
Drive
Plate assembly and ring piston pump
1
High-pressure valves
2
Pressure Sensor
3Description
Item
Control valve
4
Pressure accumulator
5
Electric feed pump
6
Filters7
Preload valve
8
Pressure relief valve (low pressure)
9
Pressure relief valve (high pressure)
10
Base pressure
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E100540
Description
Item
Barometric Pressure
A
Base pressure
BDescription
Item
Increased base pressure (preload)
C
Operating pressure
Drive
The hydraulic fluid is drawn from the sump of the
hydraulic system and directed through a filter. The
feed pump pressurises the system and pumps
hydraulic fluid into the pump plungers. This base
pressure of 4 bar presses the rollers for the pump
plungers against the cam disc. At the same time,
hydraulic fluid flows into the working piston. This
eliminates the play in the clutch plates. The Haldex
clutch can respond quickly and distribute the torque
within fractions of a second. The spring force in
the pressure accumulator determines the base pressure of 4 bar and compensates pressure
fluctuations. A compensating spring works in the
opposite direction and prevents the plate discs
becoming blocked by the force of the working
piston. This restricts the transferable torque to
approx. 7 Nm. This value can, however, deviate
slightly due to temperature and/or the difference
in speed between the input and output shafts.
Increased base pressure (preload)
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E100541
Description
Item
Barometric Pressure
A
Base pressure
BDescription
Item
Increased base pressure (preload)
C
Operating pressure
Drive
To ensure very fast torque transmission, a higher
voltage is applied to the electric feed pump and
the control valve fully closed before the shaft-driven
pump is brought into operation. As a result, the
maximum pressure is raised above the base
pressure, and a torque of up to 80 Nm applied to
the multi-plate clutch. This achieves significantly
faster pressure build-up than with older systems (second generation). To protect the pump from
overloading, the pressure is restricted to approx.
10 bar by the pressure relief valve. The hydraulic
fluid flows back into the sump via the pressure
accumulator.
Pressure build-up
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1
2
3
4
E115887
Description
Item
Fluid filter
1
All-wheel drive control unit
2Description
Item
Electric feed pump
3
Pressure accumulator
4
The electric feed pump is an axial piston pump
which is more robustly designed than the gerotor
pump in the 3rd generation Haldex. The higher
feed pressure means that the ring piston pump at
the clutch plate assembly, the pressure relief
valves, preload valve and the high pressure valves
are no longer necessary.
The pressure accumulator on the 4th generation
Haldex is larger and is designed for the higher
pressure. The 4th generation Haldex has a larger fluid filter
which contains a non-return valve.
The all-wheel drive control unit no longer contains
a pressure sensor in the 4th generation Haldex.
Pressure control - 4th generation Haldex
clutch
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Rear Drive Axle/Differential
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