Land Rover Lesson 2 Auto Trans Coolingine Rover Manual

							The sprags are located in a cage which is a spring which
holds the sprags in the wedge direction and maintains
them in contact with the inner and outer races.
Referring to the illustration, the sprags are designed so
that the dimension B is larger than the distance between
the inner and outer race bearing surfaces. When the
outer race rotates in a clockwise direction, the sprags
twist and the edges across the dimension B wedge
between the races, providing a positive drive through
each sprag to the inner race. The dimension A is smaller
than the distance between the inner and outer race
bearing surfaces. When the outer race rotates in an
anti-clockwise direction, the dimension A is too small
to allow the sprags to wedge between the races, allowing
the outer race to rotate freely.
On the illustration shown, when the outer race is rotated
in a clockwise direction, the sprags twist and are
wedged between the inner and outer races. The sprags
then transfer the rotation of the outer race to the inner
race, which rotates at the same speed.
Lock-Up Clutch Mechanism
The Torque Converter Clutch (TCC) is hydraulically
controlled by an electronic pressure regulating solenoid
(EPRS4) which is controlled by the TCM. This allows
the torque converter to have three states of operation as
follows:
•Fully engaged
•Controlled slip variable engagement
•Fully disengaged
The TCC is controlled by two hydraulic spool valves
located in the valve block. These valves are actuated by
pilot pressure supplied via a solenoid valve which is
also located in the valve block. The solenoid valve is
operated by PWM signals from the TCM to give full,
partial or no lock-up of the torque converter.
Unlocked conditionA
Locked conditionB
Clutch plate1
Clutch piston2
Torque converter body3
Turbine4
Impeller5
Stator6
Piston chamber7
Turbine chamber8
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							The lock-up clutch is a hydro-mechanical device which
eliminates torque converter slip, improving fuel
consumption. The engagement and disengagement is
controlled by the TCM to allow a certain amount of
controlled slip. This allows a small difference in the
rotational speeds of the impeller and the turbine which
results in improved shift quality. The lock-up clutch
comprises a piston and a clutch friction plate.
In the unlocked condition, the oil pressure supplied to
the piston chamber and the turbine chamber is equal.
Pressurised fluid flows through a drilling in the turbine
shaft and through the piston chamber to the turbine
chamber. In this condition the clutch plate is held away
from the torque converter body and torque converter
slip is permitted.
In the locked condition, the TCC spool valves are
actuated by the electronic pressure regulating solenoid
(EPRS4). The fluid flow in the unlocked condition is
reversed and the piston chamber is vented. Pressurised
fluid is directed into the turbine chamber and is applied
to the clutch piston. The piston moves with the pressure
and pushes the clutch plate against the torque converter
body. As the pressure increases, the friction between
the clutch plate and the body increases, finally resulting
in full lock-up of the clutch plate with the body. In this
condition there is direct mechanical drive from the
engine crankshaft to the transmission planetary gear
train.
FLUID PUMP
The fluid pump is an integral part of the transmission.
The fluid pump is used to supply hydraulic pressure for
the operation of the control valves and clutches and also
to pass the fluid through the transmission cooler.
The 6HP26 fluid pump is a crescent type pump and is
located between the intermediate plate and the torque
converter. The pump has a delivery rate of 16cm3 per
revolution.
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							Securing ring1
Shaft oil seal2
O-ring seal3
Pump housing4
Ring gear5
Crescent spacer6
Roller bearing7
Impeller8
Centring pin9
Spring washer10
Outlet port (high pressure)11
Inlet port (low pressure)12
The pump comprises a housing, a crescent spacer, an
impeller and a ring gear. The housing has inlet and outlet
ports to direct flow and is located in the intermediate
plate by a centring pin. The pump action is achieved by
the impeller, ring gear and crescent spacer.
The crescent spacer is fixed in its position by a pin and
is located between the ring gear and the impeller. The
impeller is driven by drive from the torque converter
which is located on a needle roller bearing in the pump
housing. The impeller teeth mesh with those of the ring
gear. When the impeller is rotated, the motion is
transferred to the ring gear which rotates in the same
direction.
The rotational motion of the ring gear and the impeller
collects fluid from the intake port in the spaces between
the teeth. When the teeth reach the crescent spacer, the
oil is trapped in the spaces between the teeth and is
carried with the rotation of the gears. The spacer tapers
near the outlet port. This reduces the space between the
gear teeth causing a build up of fluid pressure as the oil
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							reaches the outlet port. When the teeth pass the end of
the spacer the pressurised fluid is passed to the outlet
port.
The fluid emerging from the outlet port is passed
through the fluid pressure control valve. At high
operating speeds the pressure control valve maintains
the output pressure to the gearbox at a predetermined
maximum level. Excess fluid is relieved from the
pressure control valve and is directed, via the main
pressure valve in the valve block, back to the pump inlet
port. This provides a pressurised feed to the pump inlet
which prevents cavitation and reduces pump noise.
MECHATRONIC VALVE BLOCK
The Mechatronic valve block is located in the bottom
of the transmission and is covered by the fluid pan. The
valve block houses the TCM, electrical actuators, speed
sensors and control valves which provide all
electro-hydraulic control for all transmission functions.
The Mechatronic valve block comprises the following
components:
•TCM
•Six pressure regulator solenoids
•One shift control solenoid
•One damper
•Twenty one hydraulic spool valves
•Manually operated selector valve
•Temperature sensor
•Turbine speed sensor
•Output shaft speed sensor.
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							ZF 6HP26 Automatic Transmission – Mechatronic Valve Block
Position switch1
Sliding block2
Selector spool valve3
Position switch assembly4
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							Electronic Pressure Regulator Solenoid (EPRS)
6
5
Solenoid Valve 16
EPRS 47
EPRS 58
EPRS 39
EPRS 210
EPRS 111
Electrical connector12
Transmission Control Module (TCM)13
Valve housing14
Valve plate15
Torque converter retaining valve16
Clutch return valve17
Element seal18
Pressure regulator dampers19
Intermediate plate20
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							ZF 6HP26 Automatic Transmission – Valve Housing Components
Selector spool valve1
Lubricating valve2
Torque converter pressure valve3
System pressure valve4
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							Torque converter clutch valve5
Retaining valve – Clutch E6
Clutch valve E7
Clutch valve A8
Valve housing9
Bolts10
Retaining valve – Clutch A11
Retaining valve – Clutch B12
Pressure reducing valve13
Shift valve 114
Retaining valve – Brake D15
Shift valve 216
Damper17
Electronic Pressure Regulator Solenoid (EPRS)
6
18
Solenoid valve 119
EPRS 420
EPRS 521
EPRS 222
EPRS 323
EPRS 124
ZF 6HP26 Automatic Transmission – Valve Plate Components
Retaining valve – Brake D21
Clutch valve – Brake D22
Clutch valve B3
Valve plate4
Clutch valve – Brake D15
Clutch valve – Brake C6
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							Electronic Pressure Regulator Solenoids (EPRS)
Six Electronic Pressure Regulator Solenoids (EPRS)
are located in the valve block. The solenoids are
controlled by Pulse width Modulation (PWM) signals
from the TCM. The solenoids convert the electrical
signals into hydraulic control pressure proportional to
the signal to actuate the spool valves for precise
transmission operation.
The following table shows EPRS and their associated
functions:
FunctionEPRS
Clutch A1
Clutch B2
Clutch C3
Brake clutches D and E4
System pressure control5
Torque converter lock-up
control
6
Solenoids EPRS 1, 3 and 6 supply a lower control
pressure as the signal amperage increases and can be
identified by a black connector cap. The TCM operates
the solenoids using PWM signals. The TCM monitors
engine load and clutch slip and varies the solenoid duty
cycle accordingly. The solenoids have a 12V operating
voltage and a pressure range of 0 - 4.6 bar (0 - 67
lbf.in2).
Solenoids EPRS 2, 4 and 5 supply a higher control
pressure as the signal amperage increases and can be
identified by a green connector cap. The solenoids are
normally open, regulating flow solenoid valves. The
TCM operates the solenoids using a PWM earth
proportional to the required increasing or decreasing
clutch pressures. The solenoids have a 12V operating
voltage and a pressure range of 4.6 - 0 bar (67 - 0
lbf.in2).
The resistance of the coil winding for the EPRS
solenoids is 5.05 ohms at 20°C (68°F).
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							Control Solenoid
A shift control Solenoid Valve (SV) is located in the
valve block. The solenoid is controlled by the TCM and
converts electrical signals into hydraulic control signals
to control clutch application.
The shift control solenoid is an open/closed, on/off
solenoid which is controlled by the TCM switching the
solenoid to earth. The TCM also supplies power to the
solenoid. The TCM energises the solenoid in a
programmed sequence for clutch application for gear
ratio changes and shift control.
The resistance of the solenoid coil winding for solenoid
is between 26 to 30.4 ohms at 20°C (68°F).
Sensors
Speed Sensors
The turbine speed sensor and the output shaft speed
sensor are Hall effect type sensors located in the
Mechatronic valve block and are not serviceable items.
The TCM monitors the signals from each sensor to
determine the input (turbine) speed and the output shaft
speed.
The turbine speed is monitored by the TCM to calculate
the slip of the torque converter clutch and internal clutch
slip. This signal allows the TCM to accurately control
the slip timing during shifts and adjust clutch application
or release pressure for overlap shift control.
The output shaft speed is monitored by the TCM and
compared to engine speed signals received on the CAN
bus from the ECM. Using a comparison of the two
signals the TCM calculates the transmission slip ratio
for plausibility and maintains adaptive pressure control.
Temperature Sensor
The temperature sensor is also located in the
Mechatronic valve block. The TCM uses the temperature
sensor signals to determine the temperature of the
transmission fluid. These signals are used by the TCM
to control the transmission operation to promote faster
warm-up in cold conditions or to assist with fluid
cooling by controlling the transmission operation when
high fluid temperatures are experienced. If the sensor
fails, the TCM will use a default value and a fault code
will be stored in the TCM.
Damper
There is one damper located in the valve housing. The
damper is used to regulate and dampen the regulated
pressure supplied via EPRS 5. The damper is load
dependent through modulation of the damper against
return spring pressure.
The damper comprises a piston, a housing bore and a
spring. The piston is subject to the pressure applied by
the spring. The bore has a connecting port to the function
to which it applies. Fluid pressure applied to the
applicable component (i.e. a clutch) is also subjected to
the full area of the piston, which moves against the
opposing force applied by the spring. The movement
of the piston creates an action similar to a shock
absorber, momentarily delaying the build up of pressure
in the circuit. This results in a more gradual application
of clutches improving shift quality.
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