Part 2
Transmission Description
PLANETARY GEAR TRAINS
The planetary gear trains used on the ZF 6HP28 transmission comprise a single web planetary gear train and a double web planetary gear train. These gear trains are known as Lepelletier type gear trains and together produce the six forward gears and the one reverse gear.
Single Web Planetary Gear Train
The single web planetary gear train comprises:
- Sunwheel
- Three (naturally aspirated versions) or four (SC (supercharger) versions) planetary gears
- Planetary gear carrier (spider)
- Ring gear or annulus.
Torque Converter Input Shaft
The double planetary gear train comprises:
- Two sunwheels
- Three short planetary gears
- Three long planetary gears
- Planetary gear carrier
- Ring gear or annulus
ELECTRONIC PARK LOCK
The park lock is electronically actuated by solenoid valve located in the valve block. The park lock is engaged by a mechanical spring system comprising a parking disc and a lock cylinder controlled by a solenoid valve.
The park lock is engaged when the TCM (transmission control module) receives a park request from the JaguarDrive selector. When the park lock is released, a solenoid valve in the valve housing directs hydraulic pressure to the lock cylinder, which moves the piston within the cylinder and releases the park lock pawl at the rear of the transmission by means of a connecting rod. The solenoid on the lock cylinder is energized and locks the cylinder piston in the unlocked position. Additional locking of the piston is achieved with ball catches within the lock cylinder.
When park is selected, the solenoid on the lock cylinder is de-energized, the ball catches are released and the piston is free to move in the lock cylinder. The solenoid in the valve housing is also de-energized. The spring loaded parking disc pulls the cylinder piston in the park direction which allows the park disc to move on its mounting. This movement is transferred via the connecting rod to parking pawl, which is engaged in the park lock gear.
If an electrical failure occurs, the park lock can be manually released by means of an emergency park release lever located in the floor console. The lever is connected to the parking disc by a cable and allows the park lock to be released manually. For additional information, refer to 307-05 Automatic Transmission/Transaxle External Controls.
TRANSMISSION CONTROL MODULE
The TCM (transmission control module) is an integral part of the Mechatronic valve block which is located at the bottom of the transmission, within the fluid pan. The TCM (transmission control module) is the main controlling component of the transmission.
The TCM (transmission control module) processes signals from the transmission speed and temperature sensors, ECM (engine control module) and other vehicle systems. From the received signal inputs and pre-programmed data, the module calculates the correct gear, torque converter clutch setting and optimum pressure settings for gear shift and lock-up clutch control.
CONTROL DIAGRAM
NOTE:
A = Hardwired; B = K bus; D = High speed CAN (controller area network) bus; O = LIN (local interconnect network) bus
PRINCIPLES OF OPERATION
Power Flows
Operation of the transmission is controlled by the TCM (transmission control module), which electrically activates various solenoids to control the transmission gear selection. The sequence of solenoid activation is based on programmed information in the TCM (transmission control module) memory and physical transmission operating conditions such as vehicle speed, throttle position, engine load and JaguarDrive selector position.
Engine torque is transferred, via operation of single or combinations of clutches to the 2 planetary gear trains. Both gear trains are controlled by reactionary inputs from brake clutches to produce the 6 forward gears and 1 reverse gear. The ratios are as follows:
Shift Elements
The shift elements are three rotating multiplate clutches (A, B and E) and two fixed multiplate brakes (C) and D). All shifts from 1st to 6th gears are power-on overlapping shifts. Overlapping shifts can be described as one of the clutches continuing to transmit drive at a lower main pressure until the next required clutch is able to accept the input torque.
The shift elements, clutches and brakes are actuated hydraulically. Fluid pressure is applied to the required clutch and/or brake, pressing the plates together and allowing drive to be transmitted through the plates. The purpose of the shift elements is to perform power-on shifts with no interruption to traction and smooth transition between gear ratios.
Power Flow 1st Gear
The JaguarDrive selector and the selector valve spool are in the 'D' position. Engine torque is transmitted from the torque converter turbine shaft to the ring gear 1 of the single web planetary gear train and the outer plate carrier of clutch 'E'.
Ring gear 1 drives the planetary gears which rotate around sunwheel 1. This drives the planetary gear carrier 1 and also the outer plate carrier of clutch 'A' and the inner plate carrier of clutch 'B'.
When clutch 'A' is engaged, sunwheel 3 in the double web planetary gear train is driven and meshes with the short planetary gears.
The double web planetary gear train is locked against the transmission housing by brake 'D'. This allows ring gear 2 (output shaft) to be driven in the same direction as the engine via the long planetary gears.
NOTE:
Refer to 'Shift Elements' illustration for key
Power Flow 2nd Gear
The JaguarDrive selector and the selector spool valve are in the 'D' position. Engine torque is transmitted from the torque converter turbine shaft to the ring gear 1 of the single web planetary gear train and the outer plate carrier of clutch 'E'.
Ring gear 1 drives the planetary gears which rotate around sunwheel 1. This drives the planetary gear carrier 1 and also the outer plate carrier of clutch 'A' and the inner plate carrier of clutch 'B'.
When clutch 'A' is engaged, sunwheel 3 in the double web planetary gear train is driven and meshes with the short planetary gears.
Sunwheel 2 is locked to the transmission housing by brake clutch 'C'. The long planetary gears, which are also meshed with the short planetary gears, roll around the fixed sunwheel 2 and transmit drive to the double web planetary gear train carrier and ring gear 2 in the direction of engine rotation.
NOTE:
Refer to 'Shift Elements' illustration for key
Power Flow 3rd Gear
The JaguarDrive selector and the selector spool valve are in the 'D' position. Engine torque is transmitted from the torque converter turbine shaft to the ring gear 1 of the single web planetary gear train and the outer plate carrier of clutch 'E'.
Ring gear 1 drives the planetary gears which rotate around sunwheel 1. This drives the planetary gear carrier 1 and also the outer plate carrier of clutch 'A' and the inner plate carrier of clutch 'B'.
When clutch 'A' is engaged, sunwheel 3 in the double web planetary gear train is driven and meshes with the short planetary gears.
Sunwheel 2 is driven via clutch 'B' which is engaged. The long planetary gears, which are also meshed with the short planetary gears, cannot roll around the fixed sunwheel 2 and therefore transmit drive to the locked double web planetary gear train carrier in the direction of engine rotation.
NOTE:
Refer to 'Shift Elements' illustration for key
Power Flow 4th Gear
The JaguarDrive selector and the selector spool valve are in the 'D' position. Engine torque is transmitted from the torque converter turbine shaft to ring gear 1 of the single web planetary gear train and the outer plate carrier of clutch 'E'.
Ring gear 1 drives the planetary gears which rotate around sunwheel 1. This drives the planetary gear carrier 1 and also the outer plate carrier of clutch 'A' and the inner plate carrier of clutch 'B'.
When clutch 'A' is engaged, sunwheel 3 in the double web planetary gear train is driven and meshes with the short planetary gears.
The double web planetary gear carrier is driven via clutch 'E' which is engaged. The long planetary gears, which are also meshed with the short planetary gears and the double web planetary gear carrier, drive ring gear 2 in the direction of engine rotation.
NOTE:
Refer to 'Shift Elements' illustration for key
Power Flow 5th Gear
The JaguarDrive selector and the selector spool valve are in the 'D' position. Engine torque is transmitted from the torque converter turbine shaft to ring gear 1 of the single web planetary gear train and the outer plate carrier of clutch 'E'.
Ring gear 1 drives the planetary gears which rotate around sunwheel 1. This drives the planetary gear carrier 1 and also the outer plate carrier of clutch 'A' and the inner plate carrier of clutch 'B'.
When clutch 'A' is engaged, sunwheel 3 in the double web planetary gear train is driven and meshes with the short planetary gears.
The long planetary gears, which are also meshed with the short planetary gears and the double web planetary gear carrier, drive ring gear 2 in the direction of engine rotation.
NOTE:
Refer to 'Shift Elements' illustration for key
Power Flow 6th Gear
The JaguarDrive selector and the selector spool valve are in the 'D' position. Engine torque is transmitted from the torque converter turbine shaft to ring gear 1 of the single web planetary gear train and the outer plate carrier of clutch 'E'.
Clutches 'A' and 'B' are released, removing the effect of the single web planetary gear train.
Clutch brake 'C' is applied which locks sunwheel 2 to the transmission housing.
Clutch 'E' is engaged and drives the double web planetary gear carrier. This causes the long planetary gears to rotate around the fixed sunwheel 2 and transmit drive to ring gear 2 which is driven in the direction of engine rotation.
NOTE:
Refer to 'Shift Elements' illustration for key
Power Flow Reverse Gear
The JaguarDrive selector and the selector spool valve are in the 'R' position. Engine torque is transmitted from the torque converter turbine shaft to ring gear 1 of the single web planetary gear train and the outer plate carrier of clutch 'E'.
Ring gear 1 drives the planetary gears of the single web planetary gear train which rotate around the fixed sunwheel 1. This transmits the drive to the single web planetary gear carrier, the outer plate carrier of clutch 'A' and the inner plate carrier of clutch 'B'.
With clutch 'B' applied, sunwheel 2 in the double web planetary gear train is driven and meshes with the long planetary gears.
The double web planetary gear carrier is locked to the transmission housing by brake clutch 'D'. This allows ring gear 2 to be driven in the opposite direction to engine rotation by the long planetary gears.
NOTE:
Refer to 'Shift Elements' illustration for key
Instrument Cluster
The instrument cluster is connected to the TCM (transmission control module) via the high speed CAN (controller area network) bus. Transmission status is transmitted by the TCM (transmission control module) and displayed to the driver in one of two displays in the instrument cluster. For additional information, refer to 413-01 Instrument Cluster.
Malfunction Indicator Lamp
The MIL (malfunction indicator lamp) is located in the tachometer in the instrument cluster. Transmission related faults which may affect the vehicle emissions output will illuminate the MIL (malfunction indicator lamp).
The MIL (malfunction indicator lamp) is illuminated by the ECM (engine control module) on receipt of a relevant fault message from the TCM (transmission control module) on the high speed CAN (controller area network). The nature of the fault can be diagnosed using a Jaguar approved diagnostic system which reads the fault codes stored in the TCM (transmission control module) memory.
Transmission Status Display
The transmission status display is located in a LCD (liquid crystal display) at the top of the instrument cluster, between the speedometer and the tachometer. The LCD (liquid crystal display) shows the JaguarDrive selector position or the selected gear when in manual 'Jaguar Sequential Shift' mode.
The following table shows the displays and their descriptions.
The message center is located in the lower center of the instrument cluster. The message center is a LCD (liquid crystal display) to relay vehicle status and operating information to the driver and can display messages relating to a number of the vehicle systems. If a transmission fault occurs, the message center will display the message 'GEARBOX FAULT'.
Transmission Control Module
The TCM (transmission control module) outputs signals to control the shift control solenoid valve and the EPRS to control the hydraulic operation of the transmission.
The TCM (transmission control module) processes signals from the transmission speed and temperature sensors, the ECM (engine control module) and other vehicle systems. From the received signal inputs and pre-programmed data, the module calculates the correct gear, torque converter clutch setting and optimum pressure settings for gear shift and lock-up clutch control.
The ECM (engine control module) supplies the engine management data over the high speed CAN (controller area network) bus. The TCM (transmission control module) requires engine data to efficiently control the transmission operation, for example; flywheel torque, engine speed, accelerator pedal angle, engine temperature. The steering angle sensor and the ABS (anti-lock brake system) module also supply data to the TCM (transmission control module) on the high speed CAN (controller area network) bus. The TCM (transmission control module) uses data from these systems to suspend gear changes when the vehicle is cornering and/or the ABS (anti-lock brake system) module is controlling braking or traction control.
Using the signal inputs and the memorized data, the TCM (transmission control module) control program computes the correct gear and torque converter lock-up clutch setting and the optimum pressure settings for gear shift and lock-up clutch control. Special output-side modules (power output stages, current regulator circuits), allow the TCM (transmission control module) to control the solenoid valves and pressure regulators and consequently precisely control the hydraulics of the automatic transmission. In addition, the amount and duration of engine interventions are supplied to the engine management by way of the CAN (controller area network) bus.
The transmission has a fully electronic JaguarDrive selector with no Bowden cable connection to the transmission. The transmission selections are made using a rotary JaguarDrive selector which rises from the floor console once the engine is running. Rotation of the JaguarDrive selector to any of the five positions is sensed by the TCM (transmission control module) via the high speed CAN (controller area network) bus. The TCM (transmission control module) then reacts according to the selected position. The 'S' (sport) position selection allows the TCM (transmission control module) to operate the transmission using the semi-automatic 'Jaguar Sequential Shift'.
Gear selections are sensed by the TCM (transmission control module) when the driver operates the steering wheel paddle switches. Once the JaguarDrive selector position is confirmed, the TCM (transmission control module) outputs appropriate information on the high speed CAN (controller area network) bus.
If the JaguarDrive selector is in 'D', 'Jaguar Sequential Shift' is temporary and will cancel after a time period or can be cancelled by pressing and holding the + paddle for approximately 2 seconds.
If the JaguarDrive selector is in 'S', 'Jaguar Sequential Shift' is permanent and can only be cancelled by pressing and holding the + paddle for approximately 2 seconds or by moving the JaguarDrive selector to the 'D' position.
The TCM (transmission control module) can be reprogrammed using an approved Jaguar diagnostic system using a flash code. The TCM (transmission control module) processor has a 440 kb internal flash memory. Of this capacity, approximately 370 kb are used by the basic transmission program. The remainder, approximately 70 kb is used to store vehicle-specific application data.
Engine Stall
If the vehicle stalls it will coast down in gear, with the transmission providing drive to the engine. A restart can be attempted at this point and the engine may start and the driver can continue.
If the coast down speed reduces such that the speed of the engine is less than 600 rev/min, the transmission will go to neutral, D illumination will flash in the instrument cluster. The driver needs to select neutral or park and then press the brake pedal to restart the engine.
If the start/stop button is pressed when driving, the message ENGINE STOP BUTTON PRESSED is displayed in the message center but there will be no change to the ignition state. If the driver requires to switch off the engine, the start/stop button must be pressed for a second time. The engine will be stopped and will be back driven by the transmission as the vehicle coasts down. When the engine speed is less than 600 rev/min the transmission engages neutral (flashing D illumination in the instrument cluster). When vehicle speed is less than 2 km/h (1.2 mph) Park is engaged. The JaguarDrive selector automatically rotates back to its lowered P position and the vehicle ignition is switched off.
The park engagement is prevented in a stall case as the ignition power is on and D was the last selected gear. The park engagement speed at ignition off is from the least value of the wheel speeds (CAN (controller area network) signal) and transmission output speed (internal signal).