4 X 4. These all-wheel drive systems are among the most advanced interactive all-wheel drive systems available in the world today.

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Jewel Jackson
6 years ago
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1 159 Introduction What s New in AWD: The ITM 3e system is just one of the latest interactive all-wheel drive systems available as part of BorgWarner s growing itrac torque management systems portfolio. Borg- Warner has a full line of active torque management devices focused on the needs of the ever expanding all-wheel drive market, such as the new NexTrac all-wheel drive system being launched in 2009 Hyndai Santa Fe and/or the Cadillac CTS s ITM all-wheel drive system also being launched this year. These all-wheel drive systems are among the most advanced interactive all-wheel drive systems available in the world today. A Closer Look at the ITM 3e System: The ITM 3e system uses sophisticated controls and algorithms to sense wheel slip and can seamlessly convert to an all-wheel drive system within milliseconds. This enhances vehicle handling by optimizing vehicle traction to both the front and rear wheels when needed. While driving at highway speeds, the ITM 3e system reduces torque transfer to the rear wheels, which improves fuel economy when compared to a full-time all-wheel drive system. The ITM 3e system is designed to work in conjunction with other vehicle onboard systems such as the anti-lock brake system (ABS) and the electronic ride stability system to provide improved traction and stability when needed. Electronically Controlled All-Wheel Drive System: The ITM 3e system requires no front-to-rear slippage to activate the all-wheel drive system, unlike other all-wheel drive systems that rely on pumps or a viscous fluid to transfer torque to the non-driving wheels when needed. This system transfers torque solely in response to accelerator pedal position and other vehicle system inputs. This electronically controlled all-wheel drive system does not incorporate traction control. The all-wheel drive system does not aid in side-to-side traction. The anti-lock brake system (ABS) is responsible for side-to-side traction using brake intervention programming.

2 160 4 X 4 Components The electronically controlled all-wheel drive system includes: An All-Wheel Drive ECM (AWD ECM) A Power Transfer Unit (PTU) or transfer case A two-piece drive shaft An Electronically Controlled Coupling (ECC) A Rear Differential assembly Axle shafts

3 161 Components (continued) ECM The AWD ECM communicates with the ABS control module and the PCM over the CAN C BUS system. The AWD ECM uses the wheel speed sensor inputs from the ABS module to monitor wheel speeds relative to one another and also determine the vehicle s actual speed. The AWD ECM uses this information along with the accelerator pedal position to determine how much torque is to be transferred to the rear wheels. The AWD ECM then sends an electrical current to the ECC that is proportional to the amount of torque required. This allows the torque transfer to the rear wheels, to be fine-tuned to the amount of traction actually needed.

4 162 4 X 4 Power Transfer Unit (PTU) The power transfer unit (PTU) or transfer case is mounted to the right side of the transmission. The right axle half-shaft passes through the power transfer unit and drives the right front wheel. The power transfer unit transfers torque from the driving wheels to the rear differential through the drive shaft and electronically controlled coupling (ECC).

163 Two Piece Drive Shaft and the ECTC Two Piece Drive Shaft: The two piece drive shaft connects the power transfer unit to the electronically controlled coupler.

5 163 Two Piece Drive Shaft and the ECTC Two Piece Drive Shaft: The two piece drive shaft connects the power transfer unit to the electronically controlled coupler. A center bearing supports the drive shaft and a center plunge type joint compensates for movement between the engine/power transfer unit and the electronically controlled coupling. The Electronically Controlled Transfer Case (ECTC) The purpose of the ECTC is to transmit torque to the rear wheels by way of a two-stage clutch system. The low torque electromagnet powered clutch, is controlled by the AWD ECM. A cam and ball mechanism amplifies the force of the low torque clutch, applying the wet multi-disc main clutch that transmits torque to the rear wheels. The wet clutch is similar to clutch packs in automatic transmissions.

164 4 X 4 The Rear Differential Assembly and Axle Shafts The rear differential assembly of the ITM 3e system consists of the electronically controlled coupling and the rear differential.

6 164 4 X 4 The Rear Differential Assembly and Axle Shafts The rear differential assembly of the ITM 3e system consists of the electronically controlled coupling and the rear differential. The rear differential uses the torque provided by the electronically controlled coupling to drive the rear wheels. The electronically controlled coupling is not serviceable and must be replaced as an assembly. Axle Shafts: The axle shafts are internal to the rear differential assembly. The purpose of the axle shaft is to transfer torque from the differential carrier to the wheels.

7 165 How Does the ITM 3e System Work? The electrically controlled all-wheel drive system includes the following electrical components: The AWD Electronic Control Module (AWD ECM) The Anti-lock Brake System (ABS)and wheel speed sensors The Electronically Controlled Coupling (ECC)

8 166 4 X 4 Operating Systems The system has four operating modes: Open loop Closed loop Wheel speed dependent Vehicle dynamics enhancement The AWD ECM also interfaces with the ABS/Stability ride control system and the traction control system. This interface allows the ABS system to influence rear wheel torque transfer through the EEC and helps the driver maintain control of the vehicle. Open Loop Operation: In high power demand situations, the all-wheel drive system immediately starts engaging the electronically controlled coupling, transferring a high percentage of torque to the rear wheels. This prevents front wheel slippage, as power is transmitted to all four wheels. This mode of operation is called open-loop operation, because the AWD ECM does not use inputs from the ABS system to control the torque transfer to the rear wheels. Closed Loop Operation: In closed-loop operation, the AWD ECM uses inputs from the ABS control module to determine the proper torque transfer as needed. Power to the rear wheels is also modulated under the following conditions. Front wheels slipping on ice while backing will transfer torque to the rear wheels Loss of traction at freeway speeds, as in hydroplaning, will transfer torque to the rear wheels. Both open-loop and closed-loop modes are always active with the closed-loop mode layered on top of the open-loop mode to increase torque to the rear wheels when needed to maintain traction in extreme situations.

9 167 Operating Systems (continued) Wheel Speed Dependent Operation: Wheel Speed dependent mode is independent of the open-loop and closed-loop modes, using wheel speed differences to determine when the vehicle is turning in a tight turn. This condition is indicated by a large difference in the side-to-side wheel speeds. This causes the AWD ECM to reduce torque to the rear wheels which prevents binding in the driveline. Vehicle Dynamics Enhancement: Additional AWD ECM calibrations control the torque being sent to the rear wheels for improved handling at speeds between 25 mph and 65 mph. At these speeds, the system increases torque to the rear wheels during cornering. Above 70 mph. and under normal driving conditions, the AWD ECM strategy provides minimal torque transfer to the rear wheels to increase fuel economy.

Fully Active vs. Reactive AWD coupling systems. How much performance is really needed? Thomas Linortner Manager, Systems Architecture

Fully Active vs. Reactive AWD coupling systems How much performance is really needed? Thomas Linortner Manager, Systems Architecture Overview 1. Market requirements for AWD systems 2. Active and Reactive