Torque convertersDESCRIPTION OF TECHNICAL CHALLENGE
Automatic transmission vehicles, especially passenger cars, are gaining popularity in the global
market, especially in the premium and luxury vehicle segments. Automatic transmission
vehicles are known for effortless driving, and the increase in congested stop-and-go driving
conditions is pushing customers to select automatic transmission vehicles. Each automatictransmission needs a torque converter and manufacturers are trying to optimize torqueconverters to enhance vehicle operating efficiency.

Torque converters must be testedto be oil-tight to avoid wear of theinternal parts and early failure.

At first, even the smallest leak in a torque converter will annoy the car’s driver (a stain on thefloor after parking, for example), but overextended time, this leak will lead to malfunctioning of
the car: During acceleration the driver will feel slippage when the vehicle shifts from engine todrive. In this stage accelerated wear of the torque converter will also occur. Finally, if no oil isleft in the torque converter, the torque converter will fail completely and no driving power will betransmitted anymore.
The housing of the torque converter is made out of two shells which are welded together after
assembling the internal parts. For quality control, this weld needs to be leak tested to prevent
oil leakage. Typically torque converters are tested against a leak rate in the 10-4… 10-5 mbarl/srange.

THE INFICON SOLUTION
Leak testing of torque converters
Two options exist for leak testing of torque converters, depending on required throughput andinvestment:

Accumulation testing

Vacuum chamber testingThroughput

Low to mediumHighInvestmentLowHigh

Helium required

100%

20% to 40%

For leak testing, the torque converter must be sealed on two sides: on a flat surface on the sidefacing the engine (later this surface will be sealed with an O-ring) and also on the side facing
the transmission.

LEAK TESTING OF COMPONENTSTORQUE CONVERTERS

Accumulation testing
The part is placed in a simple chamber in an adapter of the leak testing system
which seals all openings. Then the part is evacuated and the evacuationpressure is held for about 2 sec to check for gross leaks. The torque converter isthen pressurized with 100% helium to a slight overpressure pressure of approx.
1.5 bar (~ 22 psi) allowing the test gas to escape through any leaks into theaccumulation chamber. Fans ensure an even distribution of the test gas in thechamber – so, independent of the position of the leak, precise measurement
values are guaranteed. It is at this point that the T-Guard Helium Accumulation
Sensor determines the test gas concentration in this atmosphere. A rise ofconcentration is converted into a leak rate.
Torque converters can be tested with low
investment in an accumulation system with
the T-Guard sensor.

Vacuum chamber testing
For higher throughput and lower helium consumption, vacuum chamber testing isused. The torque converter is placed in the testing chamber and connected to
the vacuum system. Once the chamber lid is closed, vacuum pumps pull avacuum on the inner volume of the torque converter as well as on the vacuumchamber. When the torque converter is evacuated, it is backfilled with 20 to 40%of helium. Helium then has the opportunity to migrate outwards and if a leak ispresent, the INFICON LDS3000 Helium Leak Detector (connected to the vacuumchamber) detects the helium atoms as they emerge from the torque converter.

For high-throughput testing and saving on
helium cost, torque converters should betested in vacuum chambers systems.

Both accumulation and vacuum chamber testing allow an operator to detectleaks confidently with high repeatability. Testing is not affected by heat andmoisture on the test pieces or in the environment. In addition, parts can be tested
quickly after welding.

BENEFITS OF LEAK TESTING WITH TRACER GAS•••••Accurate, traceable and repeatable measurements for confident leak testing
Highly sensitive testing methods, able to detect small leaks (10-4 .. .10-6 mbar l/s range)
Testing independent of temperature and humidity
Dry process, no risk of water intake during testing
Option of automated, high throughput process as well as a lower cost process available

For more information, please visit us atwww.inficonautomotive.com

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re a c hus @ i nf i co n. c o m

Due to our continuing program of product improvements, specifications are subject to change without notice.
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