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Transaxle Efficiency and Stall Testing

Project Brief

Automotive transmission and transaxle development requires precise control and acquisition of test data. In order to evaluate transmission and transaxle performance, a precision electric motor and dynamometer test stand was developed that has the following characteristics:

	The precision electric motor and dynamometer test stand developed at SwRI evaluates transmission and transaxle performance.

• Speed Range, 0 to 6,000 rpm

• Speed Accuracy, ± 1 rpm

• Torque Range, 0 to 1,500 ft-lb

• Torque Accuracy, 1 ft-lb

The Southwest Research Institute (SwRI) transaxle test stand configuration is universal in nature, so it can accept transaxles with different input-to-output shafts, and vertical and horizontal centerline dimensions. Input power to the transaxle is provided by a 300-HP DC dynamometer capable of input speeds up to 6,000 rpm. Input torque is measured with an in-line torque transducer.

The transaxle is driven through a spindle and bearing assembly mounted in a headstand. Outputs from the transaxle half-shafts are connected through two in-line torque transducers and into two identical 2.00:1 gearboxes. The gearbox outputs are connected through rigid shafting and into a 575-HP DC dynamometer. Transaxle output speeds of 1,500 rpm (100 mph for a 12" R.R.) can be obtained.

Using two gearboxes where outputs are rigidly connected eliminates any differential effects caused when dissimilar output speeds occur. Automatic emergency shutdowns occur for the following conditions:

• Overtorque (input and output)

• Overspeed (input and output)

• Overtemperature ATF

• Gearbox pressures

Control is achieved through a digital dynamometer controller, in-line torque transducers, precision speed regulators, and a PID closed-loop feedback system. The test stand is fully computer-controlled, providing automated testing through setpoint operation based on multiple control parameters, data acquisition, real-time data processing with graphical presentation, report formatting, and automatic shutdown.

Data obtained indicate torque losses and related transaxle efficiency. These losses are associated with pump, torque converter, rolling element bearings, bearing preload, journal bearings, gear mesh, windage, seal drag and clutch pack friction disk clearances.

Transaxle Evaluation

Transaxle testing and evaluation, which is performed in each gear, consists of simulating the following conditions:

• Constant input

• Stall

• Neutral

• Backdrive

• Spin

Automatic transmission fluid temperature is maintained through a circuit consisting of a heat exchanger, multiple infrared heaters, and an in-line heater. The circuit is regulated with a PID temperature controller.

For more information about our drivetrain engineering capabilities and past performance briefs, or how you can contract with SwRI, please contact Douglas Fussner at dfussner@swri.org or (210) 522-3972.

drivetrain.swri.org

| Design and Development | Engine, Emissions & Vehicle Research Division | SwRI Home |

Southwest Research Institute^® (SwRI^®), headquartered in San Antonio, Texas, is a multidisciplinary, independent, nonprofit, applied engineering and physical sciences research and development organization with 11 technical divisions.

December 28, 2012