Presentation on theme: "Chapter 20 Electronically Automated Standard Transmissions."— Presentation transcript:
Chapter 20 Electronically Automated Standard Transmissions
Objectives (1 of 2) Explain how a standard mechanical transmission is adapted for automated shifting in three-pedal and two-pedal systems. Identify three different OEM automated transmissions and interpret the serial number codes of each. Describe the hardware changes that differentiate a standard Roadranger twin-countershaft transmission from its electronically automated version. Outline the electronic circuit components that are used to manage AutoShift transmissions.
Objectives (2 of 2) Outline the main box and auxiliary section actuator components required for AutoShift electronically automated, standard transmissions. Describe how the electronic circuit components work together to perform the system functions. Perform some basic diagnostic troubleshooting on automated transmission electronics. Describe the ZF Meritor SureShift and FreedomLine transmissions and the Mercedes Benz AGS transmissions.
Transmission Identification The best way of identifying transmission specifications on a vehicle is by accessing the chassis data bus, specifically the 130 MID for generic ESTs.
AutoShift (1 of 2) Serial Number: RTAO – B AS R Roadranger T Twin countershaft A Automated O Overdrive (X) = nominal torque capacity 7 Design level (5 = spur gear, 6 = multimesh gearing, 7 = multimesh front, helical auxiliary gearing) 10 Number of forward speeds B Ratio set designation (C) ASAutoShift
AutoShift (2 of 2)
UltraShift Serial number: RTO B - DM 2 R Roadranger T Twin countershaft O Overdrive 14 Torque capacity 9 Design level 10 Forward speeds B Ratio category DM UltraShift with DM clutch 2 Automation level/Gen II electronics
Freedomline Serial Number: M O – 16 Z 10 C - A 18 M ZF Meritor O Overdrive (no letter = direct drive) 16 Input torque rating: 1,600 lb./ft. Z Design platform: Z = FreedomLine F = 9 speed G = 10 speed 10 Number of forward gears C Ratio A Automated (S = shift by wire, M = manual) 18 Highest torque in top 2 gears = 1800 lb./ft.
Mercedes Benz AGS Serial Number: MBT – 560 S - 6 O MBT Mercedes-Benz Transmission 560 Input torque rating 560 lb./ft. 6 Number of forward ratios O Overdrive (D 5 direct drive)
AutoShift Components The Eaton Fuller Roadranger AutoShift automated transmission is a two-module system. –The System Manager (ECU) does the “thinking.” –A second module, the transmission controller (ECU), converts that thinking into action by performing the switching functions of the transmission. AutoShift transmission components can be grouped as follows: –Base standard gearbox –Transmission automation components –Vehicle automation components
Base Transmission The AutoShift transmission is based on a Roadranger twin- countershaft platform. A Fuller 10-speed transmission has a 5-speed main or front case, with a 2-speed auxiliary section. Although the base transmission has a similar appearance to non-automated versions, the following changes are required: –Main box. Two screw bosses have been added to the case so the transmission controller can be mounted to the side. –Range cylinder cover. The range cylinder cover is altered to house the range shift control mechanism. –Shift bar housing. The shift bar housing has been machined to accept the speed sensors. –Shift yokes. The shift yokes have been hardened at the fork pads to improve durability during shifts.
Electric Shifter Assemblies The shift shaft is a square section shaft. The shift finger rides on the shift shaft. This permits the shift finger to be moved along the rail. The shift shaft has a machined area on the end to enable it to rotate the position sensor. The gear select yoke also rides on the shift shaft. The yoke is driven by the gear select ball screw, which rotates the shift shaft for gear selection. The gear select sensor provides position data to the transmission controller.
Ball Screw Assemblies (1 of 2) The shift finger position is located by a pair of ball screws. One ball screw is used for the lateral (left to right) movement that is required to select the correct rail. The other ball screw is used for the forward or backward positioning required to select a gear.
Ball Screw Assemblies (2 of 2) The ball screw assembly is made up of a worm gear, ball screw nut, and ball bearings. When the worm gear rotates, the ball bearings ride in the grooves of the worm threads. When a ball reaches the end of a ball screw block, it is forced into a tube to be returned to the beginning of the worm threads in the ball screw block.
Rail Select Ball Screw The gear select ball screw nut has a pair of tabs, one on either side. These tabs drive the gear select yoke, which is located on the shift shaft with the shift finger. When gear selection is commanded, the ball screw block moves the gear select yoke, which in turn moves the shift shaft.
Electric Motors The motors use a permanent magnet operating principle and are capable of forward or reverse rotation. The rail select motor is pinned directly to the rail select ball screw and the gear select motor is pinned directly to the gear select ball screw. The electric motors used in each ball screw assembly are not interchangeable.
Position Sensors (1 of 2) Position sensors convert a mechanical position to a signaled voltage value that is then returned to the ECU. AutoShift position sensors are three-wire voltage dividers. They are supplied a reference voltage of 5V, modulated by the ECU. There is a resistor between the 5V input terminal and the ground connection. A wiper contacts the resistor and, depending on its mechanical location, determines the signal voltage value returned to the ECU.
Position Sensors (2 of 2) The rail select sensor is connected to the rail select ball screw. The position sensor yoke arm fits over a pin on the side of the rail select screw block. Its signal allows the transmission controller to determine whether the shift finger is located over the correct rail before effecting a shift. The gear select sensor monitors shift finger position during gear selection. The signal returned to the transmission controller confirms whether a shift has been successfully effected.
Shop Talk Current versions of AutoShift are designed to break driveline torque when a predetermined driveline (road) speed is sensed. This prevents driveline component stall damage to the engine.
Range Valve Operation (1 of 2)
Range Valve Operation (2 of 2)
Speed Sensors (1 of 4) Three speed sensors are used in the transmission. They measure and report: –Input shaft speed –Mainshaft speed –Output shaft speed When the teeth of the pulse wheel cut through the magnetic field in the sensor, an AC voltage is induced in pulses. The AC voltage value and frequency produced will rise in proportion to the increase in rotational speed. These sensors can be tested by measuring voltage output.
Speed Sensors (2 of 4) The input shaft speed sensor is located at the right front corner of the shift rail housing. The speed sensor magnet and coil produce pulses from the upper countershaft PTO gear. The AC voltage and frequency rise proportionally with shaft speed. The ECU measures the frequency of the pulses, not the actual voltage generated. Input shaft speed is calculated by multiplying countershaft speed by the head set ratio.
Speed Sensors (3 of 4) The mainshaft speed sensor is located at the left rear corner of the shift rail housing at the auxiliary countershaft drive gear. A pulse generator principle is used; the AC voltage and frequency produced and sent to the ECU increase proportionally with shaft rotational speed. The auxiliary countershaft drive gear is meshed to the mainshaft through the auxiliary drive gear and is driven at the same speed.
Speed Sensors (4 of 4) The output shaft speed sensor picks up pulses produced by a tone ring located on the output shaft. This tailshaft-located sensor inputs road speed data to the AutoShift transmission controller and to other chassis electronic systems. Road speed is determined by factoring the output shaft speed with the drive axle carrier ratio and the rolling radius dimension of the tires. A standard 16-tooth pulse wheel is used.
Function of the Speed Sensors Shift synchronization –Input shaft speed and mainshaft speed data is used by the transmission controller for synchronizing shifts in the transmission main box. Verifies range engagement –The data generated by the mainshaft and output shaft speed sensors is used by the transmission controller to verify range engagement. Reports road speed data –The output or tailshaft speed sensor data may also be shared with other chassis electronic systems as vehicle road speed data.
Power Module (1 of 2) The power module is located on the transmission controller next to the electric shifter unit. It incorporates the following components: –Cycling circuit breakers –Reverse voltage diode –Reverse voltage Zener diode The power module connects the vehicle electrical system with the transmission electrical and electronic systems and protects the transmission electrical system from current overloads with cycling-type circuit breakers.
Power Module (2 of 2) The AutoShift power module contains two SAE #1 cycling circuit breakers: –One rated at 25 amps. The 25-amp breaker protects the circuit supplying the electric shifter motors and the logic battery power from current overloads. –The other at 10 amps. The 10-amp breaker is located in series in the circuit supplying logic battery power following the 25- amp breaker.
Reverse Voltage Diode The reverse voltage diode is located just past the 25-amp circuit breaker. The diode permits current flow in one direction only. In the event of a reverse polarity condition, the reverse voltage diode blocks current flow into the transmission electrical circuit.
Reverse Voltage Zener Diode The reverse voltage zener diode is located between the negative terminal on the reverse voltage diode and battery ground. The zener diode functions as a normal diode but acts to regulate voltage should it exceed a specified level. The reverse voltage zener diode used in the AutoShift power module will permit current flow, although it will not permit the voltage value to exceed 32V.
Power Module Functions Motor Power. Connected to the vehicle cranking motor, the circuit passes through the 25-amp circuit breaker and the reverse voltage diode and connects to the motor terminals. Motor ground. The motor is direct grounded through the power module by means of a wire to the cranking motor ground terminal. Logic power. Logic power refers to the electric feed required to power up the system ECUs. It is routed from the vehicle cranking motor battery terminal through both the 25-amp and 10-amp circuit breakers. Logic ground. The logic ground is routed direct from the cranking motor ground terminal through the power module and out to the logic power connector.
Transmission Controller It has some limited processing capability but is mainly responsible for managing the switching requirements of the system. The transmission controller ECU is multiplexed. It is connected to the system electrical/electronic circuit by means of a dedicated harness known as the transmission harness. All of the input and output circuits are connected to the transmission controller by means of this harness, including the data link to the system manager.
Inertia Brake The inertia brake system on an AutoShift transmission helps stop the countershafts on initial engagements when the clutch is either out of adjustment or defective. The inertia brake is mounted at the 6- or 8-bolt PTO. The inertia brake consists of a solenoid and brake. The solenoid controls the inertia brake by switching regulated air pressure to the inertia brake piston to apply the friction and reaction discs, which brakes the countershaft.
Caution When removing the inertia brake solenoid, ensure that system air pressure is completely relieved and the air/filter regulator is removed.
Vehicle Automation Components The vehicle automation components connect the transmission electrical and electronic circuits with those of the vehicle. This group of components includes: –System manager –Gear display –Shift lever –Power connect relay –Start enable relay –Vehicle harnesses
System Manager The system manager ECU is a second microprocessor module with the dual functions of interfacing with the rest of the vehicle and overall management of the transmission systems. –Controlling logic power –Managing shifting –Processing fault conditions –Processing shift lever commands –Controlling Service and Wait lights –Providing information to lever digital display
Caution The shifter module must be calibrated before a vehicle is placed in operation.
Data Retention The system manager stores fault code data in its nonvolatile RAM before turning off the power connect relay during each shutdown.
Service light –The service light displays fault information to the driver or technician. –A flashing or continuous illumination of the service light indicates that a fault code has been logged. –Logged fault codes can then be pulse displayed by flashing numeric codes on the service light. Wait light –The wait light was only used on the earliest versions of AutoSelect/AutoShift. –On those transmissions using a wait light, it is illuminated on power-up when the system manager and transmission controller perform a self-check sequence. –If the transmission checks okay, the wait light turns off.
Speaker –The speaker tone is used to alert the driver to break torque on the driveline so that a shift can be effected. –The tone signal is output by the system manager. Detents –The detent mechanism locates the transmission shift lever in the correct location in each range select position. –It provides an element of gearshift feel to the driver when shifting from one gear to another.
Gear Display When a shift is initiated, the target gear is displayed continuously. When the transmission shifts to neutral, the target gear begins to flash. When the shift sequence is completed, the display ceases to flash and the range status is displayed. Up arrows indicate the input shaft speed must be increased until it matches main shaft speed. Down arrows indicate the input shaft speed must be decreased to match the main shaft speed.
Vehicle Harnesses (1 of 2)
Vehicle Harnesses (2 of 2)
Tower Harness Service Port The service port is located in the tower harness. It is used to access circuits for voltage checks. The circuits can be checked without separating harness connectors. –Pin A: ignition power –Pin B: dummy –Pin C: measures voltage at the power connect relay –Pin D: ground –Pin E: start enable relay coil –Pin F: dummy –Pin G: power connect relay coil; output from the system manager
Fallback Modes When a fault code is logged, the transmission electronics are designed to assess all remaining functionality and then default to a limited operational mode. –Five-speed fallback –One-speed fallback –In-place fallback –Downshift fallback
Fault Code Status An active code indicates a problem active at the time of reading the system. An inactive code (historic code) indicates the occurrence of a fault that has either occurred in the past or is not detected at the moment of reading the system. The presence of an inactive code may indicate that the vehicle has not been driven in the proper manner. AutoShift system troubleshooting should be performed using the AutoShift service literature that contains step-by-step troubleshooting guides.
Pretests Transmission pretests should be performed before progressing to specific fault code isolation. Pre-checks require that electrical inputs and pneumatic supply to the transmission be functioning properly. The pretests eliminate obvious high-level problems immediately before progressing to a detailed, sequentially stepped diagnostic procedure.
Symptom-driven Diagnostics No fault code –A transmission is, above all, a mechanical device, and problems will occur in which active or inactive electronic codes are not logged. Mechanical faults –Never assume that every fault must be electronically monitored.
CEEMAT This was an early, not too successful effort by Eaton at an automated transmission system. The acronym stands for converter enhanced, electronically managed, automated transmission. You do see a few CEEMAT automated transmissions around, but more likely in a college or teaching environment rather than on the highway.
Engine SynchroShift (ESS) Rockwell Meritor introduced Engine SynchroShift (ESS) in 1997 just before their merger with the German company ZF. ESS is a three-pedal system designed to synchronize engine rpm automatically to road speed during any shift sequence. The ESS transmission had no independent processing capability and relied upon multiplexing to the engine electronics to operate. The end result was to make the shifting of a non-synchronized manual transmission as easy as shifting a fully synchronized transmission. –As a three-pedal system, the main function of the clutch was to break driveline torque at stall; that is, for starting and stopping the vehicle. –Auxiliary range shifts were automatic, reducing driver effort and synchronizer damage. –ESS featured a break torque switch that enabled the driver to power upshift and downshift.
SureShift SureShift is a ZF Meritor three-pedal automated transmission that uses joystick initiated shifts. The clutch pedal is used only to break driveline torque at stall (starting and stopping). SureShift is currently available in 9- and 10-speed transmissions. The electronics are J1939 networked to the chassis data bus. The system is essentially a later version of the ESS system.
FreedomLine The ZF Meritor FreedomLine transmission was the first two-pedal system automated transmission available for trucks. The driver can select either automatic or manual modes of operation, but he has no direct control over clutching. A self-adjusting system-actuated clutch is built into the FreedomLine automated transmission. It is available in 12- and 16-speed versions. FreedomLine transmissions are networked into the chassis data bus via a J1939 data link.
Mercedes-Benz AGS The automated transmission is an adaptation of the Mercedes- Benz six-speed, medium-duty, mechanical transmission that has been around for a number of years. It is packaged into an aluminum housing and uses a two-pedal system with a manual option mode. When operated in manual mode, the management electronics prevent the driver from making a shift that could result in driveline damage. It is networked to the J1939 data bus so that shift algorithms are based in what is happening elsewhere in the engine and drivetrain. Troubleshooting is accomplished using Freightliner ServicePro software.
UltraShift The UltraShift automated transmission was introduced by Eaton Fuller Roadranger in 2003 as a two-pedal system. The initial release was a 10- speed unit with an inertia brake. UltraShift uses a modular automation design that is said to simplify service repair work. The clutch used is a 15.5 inch, two-plate, ceramic button type with coaxial springs. In common with all current automated transmissions, the driver can option manual shifting. The Eaton Gen II software is programmed with algorithms that prevent the driver from making a shift that could result in driveline damage.
Urge to Move The latest innovation from Eaton Fuller is the addition of a fully automated wet clutch to their six-speed AutoShift transmission used in medium-duty applications. This converts their automated transmission into a two-pedal system that handles similarly to an equivalent Allison automatic transmission. To make the wet clutch perform much like an automatic with a torque converter, Eaton’s wet clutch uses a creep feature known as Urge-to-Move. Urge-to-Move loads a continuous 45 pounds-feet of torque to the transmission through the wet-clutch pack so that the driver senses engagement at any time the shift lever is in the drive position. This system requires a cooler for the transmission fluid.
Summary (1 of 6) Automated standard transmissions use electronic controls to adapt a standard mechanical transmission for either semi-automated or fully automated shifting. This technology allows the driver to keep both hands on the steering wheel during shifting and significantly reduces driver fatigue. Automated transmissions can be divided into three- pedal systems that use a clutch pedal and two- pedal systems that eliminate the clutch pedal. All automated transmissions use a clutch, but the clutch is controlled by the system electronic control unit (ECU).
Summary (2 of 6) The Eaton Fuller AutoShift transmission is based on a standard Roadranger twin countershaft mechanical transmission platform. AutoShift electronics use two ECUs to perform logic processing and output switching operations required by the system. The AutoShift system manager ECU performs most of the processing. –It manages transmission functions and information, interfaces with the chassis data bus, controls shifting through its handshake connection with the transmission controller, acts on driver command signals, performs diagnostic self-checks, and logs fault codes.
Summary (3 of 6) The AutoShift transmission controller manages shifting based on command signals received from the system manager, monitors the input circuit components physically located within the transmission, exchanges speed and gear ratio status data with the system manager, and provides the system manager with diagnostic information. The AutoShift system manager ECU is located in the shift tower assembly. The transmission controller ECU is located on the left side of the transmission.
Summary (4 of 6) Shifts are effected by an electric shifter assembly that replaces the gear shift lever in a standard Roadranger transmission. A pair of reversing electric motors actuated by the transmission controller precisely locates a shift finger in the shift block recesses in the shift rails. The rail select motor is used to move the shift finger transversely (side to side) with the objective of locating it precisely in the shift recess of one of the three shift rails. The gear select motor moves forward and backward. After the shift finger has been positioned over the correct shift rail, the gear select motor is energized to move the rail into gear.
Summary (5 of 6) The means used by automated transmissions to select gears is identical to that in a standard transmission: shift finger movement first selects one of the three shift rails, then slides that rail fore or aft. AutoShift transmissions perform self-diagnostic tests and log fault codes when performance parameters of any electronically monitored component or system are out of specification. Faults are broadcast over the chassis data bus. Fault codes can be displayed by the AutoShift diagnostic (service) lights, or by either using a handheld diagnostic EST or a PC with the appropriate software.
Summary (6 of 6) The electronics are SAE J1939 compatible, which permits multiplexing with other chassis electronics systems. Most of the automated transmissions that compete with the AutoShift system are similar in terms of their principles of operation.