The friction and wear performance of wet clutches and other devices of this type can be improved by attention both to the lubricant and the friction material used. In 1995 a Japanese Standard was introduced, describing a method of determining the friction characteristics of various production clutch plate components.
Other test methods include the LVFA and the SAE#2 machines. The former uses small scale parts, manufactured from the friction material, and uses a flywheel coast-down to achieve a full range of sliding speeds. The SAE#2 machine tests a full clutch pack and, while giving an overall performance of the clutch/lubricant system, does not give detailed knowledge of friction characteristics or the influences of wear of the components.
The TE 92M Automated Clutch Friction Test Machine offers just that possibility. It uses a single friction pair in their original manufactured state. The machine may be configured to accept clutch plates from North American, European and Japanese manufacturers by fitting appropriate clamps TE 92M/FPC. Clutch plates up to 11.25 inch (286 mm) diameter may be accommodated.
The machine may also be used to test limited-slip differential, synchromesh and torque converter components with custom design modifications. The machine may be supplied with test adapters to conform to the JASO M349-2001 standard.
The TE 92M may be customised to meet the requirements of each application.
The machine frame comprises a base and top plate separated by two rigid vertical columns. This arrangement ensures accurate location of the test spindle housing with respect to the normal loading axis. The machine is supplied floor mounted and includes a range of safety interlocks.
Motor and Test Spindle
The test spindle projects downwards from the top plate and runs in a housing with precision greased for life bearings. The drive motor is also mounted on the top plate and is connected to a pulley on the test spindle by means of a timing belt. This pulley is part of the outer casing of an epicyclic gearbox, providing a 1:1 speed ratio for the small size LVFA specimens and 6:1 for the large friction specimens.
The motor is a 4-pole ac machine with a 5000 ppr (pulse per revolution) shaft encoder and vector drive giving a minimum turn-down ratio of 1000:1 on speed. This wide speed range is required to perform ramped speed sweep tests from 2 m/s down to zero with stable speed control at the very low speeds: this is required to pick up any stick-slip events. The minimum guaranteed motor speed is 2 rpm which, after the epicyclic reduction is 0.33 rpm at the clutch plate (4 mm/s at 125 mm radius).
The PC based control system with complex speed set point capability provides control of continuous ramps from zero up to the maximum speed as well as operation with discrete steps of speed:
- 0 to 2 m/s upward and downward ramps with 2 seconds fastest ramp
- Steps of speed over a 1000:1 turn-down ratio in the selected speed range (step time from 1 second to 32,000 seconds). Speed ranges are 0.33 – 333 rpm and 2 – 2,000 rpm
- Providing the ability to switch between the ramp mode and the discrete mode of operation during a single test.
Load and Torque Measurement
The various test adapters are mounted on an aluminium cross beam which is guided by linear bearings on the vertical machine columns. The beam is loaded from underneath by a pneumatic bellows actuator assembly which includes an in-line strain gauge type force transducer for measurement and feedback control of load. There are two interchangeable loading assemblies providing a 500:1 turn-down ratio on load. Stops are provided to allow the test components to be brought out of contact by removing the load, thus allowing tests involving cyclic engagement and loading of clutch components.
The test adapters are placed on a spherical bearing that provides alignment under loading and an inner spindle that permits free rotation under the influence of frictional torque generated in the contact. A torque arm is attached to the test adapter so that rotational movement is resisted by a strain gauge force transducer mounted on a bracket attached to the upper plate.
The stationary specimen is mounted in reservoir using a modular clamping system to accommodate a range of diameters and spline arrangements. Parts of the clamp are manufactured to suit the spline arrangements on the clutch plates.
A number of options are available for lubricating the contact, depending on the test work being carried out. The JASO standard requires the use of specific clutch components and an oil volume of 100 ml whereas other tests may use over 1 litre of fluid in the reservoir. Different reservoirs are required to accommodate the required test specimens and fluid volumes.
All rotating parts are guarded for worker safety. A mechanical cut-off is also provided to protect the torque transducer from over-load.
The software incorporates Alarm Level checking features that are switchable from step to step to take account of changing load conditions. There are two types of alarm, for warning and for machine shutdown. For instance a friction coefficient may be used to shut down the machine in the case of over-torque events and temperature may be used in case of over temperature.
Control and Data Acquisition
The TE 92M has PC based sequence programmable control and data acquisition. This is provided by an integrated Serial Link Interface Module and COMPEND 2000 software running on a host PC, operating under Windows. Data is stored to hard disc in standard spread sheet compatible file formats (.csv or .tsv).
Tests are defined by a sequence of steps, each step containing set-point, data recording rates and alarm level information. Set-points may be adjusted by step change or ramp. The test sequence is followed unless interrupted by the operator or an alarm. Set-points may also be adjusted manually using on screen toggles.
Specimen Size: Mean radius of friction material: 35 to 125 mm (typical) Maximum outer diameter: 286 mm Small Size Specimen: Mean radius of friction material: 15 mm (typical LVFA) Speed Measurement: 600 ppr shaft encoder Speed Turn-Down Ratio: 100:1 Machine Torque/Speed: 37.5 Nm @ 1,000 rpm 18.7 Nm @ 2,000 rpm 224 Nm @ 167 rpm 112 Nm @ 333 rpm 50% over-current capacity for 30 seconds Low Load: 50 to 1,000 N (LVFA specimens) High Load: 250 to 10,000 N (CLUTCH specimens) Torque Transducer: strain gauge beam Range: 1,000 N Torque Arm Radius: 187 mm Torque Range: 180 Nm Heater Power: 3 kW Method: electrical resistance heaters Temperature Range: 40 to 200°C (100 to 400°F) Temperature Sensor: J-type thermocouple Motor: 4 kW, 4-pole ac with 2048 pulse per rev shaft encoder Interface: Serial Link Interface Module Software: COMPEND 2000 TE 92M/CSM Coolant Service Module Circulating Fluid: heat transfer oil Feed Pump: positive displacement gear pump Pump Power: 0.37 kW Flow Rate: 4 litres/minute maximum Control Valve: 3-way electro-pneumatic Controlled Parameters Rotational Speed Temperatures Load Test Duration Recorded Parameters Load Rotational Speed Friction Torque Temperatures Test Duration Friction Coefficient Services Electricity: 380/415 V, three phase, 50/60 Hz, with neutral and earth 7.5 kW Clean, dry air: 4 cfm at 8 bar (120 psi) Mains water and drain: 10 l/min (typical) Installation Floor-standing machine: 600 mm x 800 mm deep x 1,000 mm high, 300 kg Wall-mounting cabinet: 600 mm x 360 mm x 760 mm high, 100 kg Floor-standing cabinet: 600 mm x 600 mm x 1,900 mm high, 50 kg Coolant service module: 930 mm x 530 mm x 500 mm high, 50 kg
automatic transmission fluids clutch lubricants clutch materials friction materials limited slip differential materials LVFA testing stick-slip torque converter components
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