High pressure FORD KUGA 2011 1.G Owner's Manual

Rear Drive Axle and Differential – System Operation andComponent Description
System Operation
General Information
The powertrain with all-wheel drive consists of the
following main components:
• engine
• transaxle with front axle differential
• transfer box
• halfshafts and driveshafts
• Haldex clutch
• rear axle differential
The Haldex clutch guarantees continuous variable
torque transmission to the rear axle under all
driving conditions. The Haldex clutch reacts
immediately and equally quickly with slow or fast
wheel slip.
A difference in angle of rotation of 90° between the
input and output shafts is required to build up
maximum pressure at the multi-plate clutch or to
transmit maximum torque.
The advantage of vehicles with all-wheel drive is
that they distribute the drive between all four
wheels. They therefore have a higher tractive
power. They feature improved cornering behaviour,
as the grip at all four wheels can be better utilised.
Thus, the wheels contribute to a greater degree
towards cornering stability.
The engine torque is transmitted from the transfer
box to the rear axle via a driveshaft. The driveshaft
is flange-mounted to the input side of the Haldex
clutch.
Driving situations
Pulling away and accelerating
• When pulling away and accelerating, as muchall-wheel drive as necessary must be available
immediately in the short-term. During
acceleration, the electronic system detects slip
at the front axle. This slip is counter-controlled
and thus the propulsive force optimally
distributed to the two axes.
Cornering • A sporty driving style, in particular dynamic
cornering, demands stable cornering behaviour.
The all-wheel system distributes the propulsive
force to all four wheels and by so doing boosts
the high cornering forces so that the vehicle
makes optimum contact with the road surface.
Snow and black ice
• Snow and black ice require particularly high grip. Under these conditions, the Haldex clutch
always distributes the propulsive force to the
axle with the better traction. The all-wheel
system reacts intelligently and quickly to all
driving situations.
Trailer operation
• When driving with a trailer, the trailer weight (support load) is transmitted to the rear axle via
the towbar. This reduces the load on the front
wheels, which means they can slip. The
electronic system detects this difference and
distributes most of the propulsive force to the
rear axle.
Haldex clutch
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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
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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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All-wheel drive control unit
E100663
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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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E100539
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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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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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Description
Item
Battery
1
Battery junction box (BJB) in the engine
compartment
2
Generic electronic module (GEM)
3
Powertrain Control Module (PCM)
4
Instrument cluster
5
Data link connector (DLC)
6
Steering Wheel Rotation Sensor
7
ABS/ESP module or hydraulic control unit
(HCU)
8Description
Item
Combined yaw rate sensor and lateral
acceleration sensor / longitudinal
acceleration sensor
9
Front wheel sensor
10
Rear wheel sensor
11
Rear wheel sensor
12
Front wheel sensor
13
ESP switch
14
Rear brakes
15
Front brake
16
The ABS monitors the different wheel speeds of
the vehicle with the aid of wheel speed sensors.
Using the data from all of the wheel speed sensors,
the ABS module calculates the so-called reference
speed, which is a measure of the actual road
speed. The ABS module compares the individual
circumferential wheel speeds with this reference
speed when the driver initiates braking. If one or
more of the circumferential wheel speeds deviates
too far from the reference speed, this means that
slip at the affected wheels is so great that steering
stability of the vehicle is no longer ensured. The
ABS module actuates electro-mechanical valves
which influence the brake pressure at the relevant
wheels.
Like the traction control system (TCS), the ESP
system uses a large proportion of the ABS
components. In addition, there are sensors which
pick up the steering angle, the acceleration forces
acting on the vehicle and the yaw rate or yaw
moment. The sensors transmit these signals to the
combined ABS/ESP module. Using the wheel
speed and steering angle data, the ABS/ESP
module calculates the direction of travel planned
by the driver and determines the corresponding
speed-dependent lateral acceleration and yaw
moment. These values are compared with those
actual measured. If the actual lateral acceleration
and the yaw moment deviate excessively from the
target values (unstable driving characteristics), the
ABS/ESP module actuates individual brakes
selectively via the HCU (hydraulic control unit). In
addition, the engine speed is reduced by
intervention in the engine management system.
How the system works for understeer: In the
event of understeer, brake intervention occurs at
the wheels on the inside of the curve. The rear
wheel is braked heavily, so that a high amount of slip is caused. In this way, the cornering force of
the rear axle is heavily reduced and the centrifugal
force that now becomes effective turns the rear of
the vehicle back into the curve. The front wheel is
not braked as hard. The braking force that is
transmitted via the front wheel to the road surface
generates a torque with the aid of the lever arm
(vertical tire force to the vehicle's centre of gravity),
which supports the yaw moment of the vehicle.
Both measures together result in the vehicle
reverting back to the curved path intended by the
driver.
How the system works for oversteer:
In the
event of oversteer the wheels on the outside of the
curve are braked. This time, the front wheel is
subjected to a high level of slip so that the
cornering force at the front axle is reduced. The
rear wheel is not braked as heavily and, together
with the effective lever arm, results in a reduction
in the vehicle yaw moment. Both measures
together result in the vehicle being stabilized and
reverting back to the curved path intended by the
driver.
If ESP control occurs, possible ABS interventions
will be overridden as the ESP works at higher slip
rates than the ABS.
Emergency brake assist (EBA): The emergency
brake assist helps drivers in emergency braking
situations by automatically applying the brakes with
the maximum possible braking force.
If the brake pedal is pressed very suddenly, the
ABS module increases the hydraulic pressure to
all of the brakes until the threshold for ABS
intervention is reached. This applies the maximum
braking effort for the available traction. The ABS
control unit monitors inputs from the brake pedal
switch and from the pressure sensor within the
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HCU to check for sudden actuation of the brakes.
With the brake pedal pressed, the ABS module
triggers emergency braking if the rate of increase
of hydraulic pressure exceeds the predetermined
limit.
If the brake pedal is pressed so hard that the ABS
becomes active on the front wheels then the ABS
control unit increases the pressure to the rear
wheel brakes up to the ABS intervention threshold.
EBA operation continues until the driver releases
the brake pedal sufficiently for the hydraulic
pressure in the HCU to drop below a threshold
value stored in the ABS module.
Trailer stability control:If the vehicle is ordered
with a trailer coupling then the Trailer Stability
Control function is integrated in the ESP. The ESP
detects snaking when driving with a trailer and
reduces the speed of the vehicle and trailer through
adapted braking and, if necessary, by also reducing
the engine output until the snaking movement of
the trailer is corrected.
Roll-over protection: The ESP dynamically
determines the tipping tendency of the vehicle and
works in conjunction with the EBA system to
prevent the vehicle from tipping over during
dynamic maneuvers like lane changing or while
negotiating bends.
Emergency brake light: The emergency brake
light automatically switches on the hazard flasher
system to warn drivers of other vehicles that
emergency braking is being initiated. Based on a
defined delay value, the ABS/ESP module sends
a signal to the generic electronic module (GEM)
via the CAN data bus. The GEM activates the
hazard flasher system, that then flashes 7 times.
Prerequisites for activation of the emergency brake
light are:
• The speed is higher than 50 km/h.
• The brake pedal is being actuated.
• The deceleration is greater than 9 m/s².
To prevent activation on snow or ice, for example,
the following prerequisites must be met:
• The speed is higher than 50 km/h.
• The brake pedal is being actuated.
• ABS regulation takes place.
• The deceleration is greater than 6 m/s².
Tire pressure monitoring system: The tire
pressure monitoring system used in the Kuga is
able to detect loss of air in a tire at an early stage
and warn the driver. Because it can only compare
the behaviour of the tyres with each other, it is not possible to draw conclusions about the absolute
tyre pressure. It is also not possible to monitor the
spare tyre pressure. In order for the system to
operate correctly, the tyre pressures must be
regularly checked and corrected and the system
subsequently initialised (see below).
The tire pressure monitoring system used here,
depending on the equipment level, is built into the
anti-lock braking system (ABS) as an extra function
and therefore does not have its own sensors.
The ABS module measures the loss of pressure
in the tyres by calculation using the wheel speed
sensors of the ABS system. If a tyre loses
pressure, its diameter decreases and the speed of
the wheel therefore increases. If the ABS module
detects such a loss in pressure, it sends a signal
to the instrument cluster via the CAN bus and a
warning message is displayed in the message
centre. The warning threshold depends among
other things on the dimension of the tyres being
used, the vehicle operating conditions and the
status at the last initialisation. Since neither the
absolute tyre pressure nor the position of the tyre
is known, the pressure of all the tyres must be
checked and the system re-initialised after a tyre
pressure warning. If necessary, the cause of the
loss of pressure must be investigated.
Regular tyre pressure checks are still necessary.
The system must be initialised after a tyre is
changed, winter or summer tyres fitted, the
pressures corrected or adjusted to suit the vehicle
load. This can be done by the driver using the
driver information system. For further information,
see: Owner’s Manual.
Component Description
Opto-electronic steering wheel rotation
sensor
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Anti-Lock Control - Stability Assist
206-09B- 11
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Description
Item
Electro-hydraulic power steering pump
with integrated power steering moduleRefer to Component Description:
Electro-hydraulic power steering pump
(page5)
1
Ignition switch
2
Generic electronic module (GEM)
3
Data link connector (DLC)
4
Powertrain Control Module (PCM)
5
ABS module or ESP module
6Description
Item
Steering gear
7
Integrated steering angle sensor - vehicles
built up to 09/2009RefertoComponentDescription:(page
10)
8
High pressure pipe
9
Fluid Return Line
10
Battery junction box (BJB)
11
Battery
12
System Operation
Electronic principle of operation
The power steering module requires the following
information in order to ensure precise steering
behavior in all driving situations:
• Steering wheel position
• Rate of turn of the steering wheel
• Vehicle speed
• Information about the vehicle configuration
• Information about the ignition switch position
• Instantaneous engine operating status
The required information is made available to the
power steering module via direct connections and
via the CAN bus (refer to the flow chart).
The steering wheel position and the rate of turn of
the steering wheel are transmitted to the power
steering module as PWM signals from the steering
angle sensor. The steering angle sensor receives
its voltage and ground supply from the power
steering module and operates inductively with an
input voltage of 5 V.
The vehicle speed is made available to the power
steering module as a CAN bus signal from the ABS
module or ESP module. The engine operating status is made available to
the power steering module as a CAN bus signal
from the PCM.
The power steering module obtains the vehicle
configuration information via the CAN bus from the
GEM. This information is required by the power
steering module in order to define the internal
characteristics of the power steering.
The power steering module obtains information
about the current ignition switch position via the
voltage input (terminal 15) of the ignition switch.
Whilst constantly monitoring the relevant input
signals the power steering module accesses stored
maps. With the aid of this information the pump
speed is matched to the current driving situation.
An electronic diagnosis of the electro-hydraulic
power steering can be performed with the aid of a
diagnostic tester via the DLC of the vehicle. For
additional information please refer to "Diagnosis
and Testing" in this section.
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Power Steering
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