Pulse-Width Modulated (PWM) Solenoid Valve
Functional Testing Equipment
Two single-station cells are networked to test, calibrate and exchange data at rates of 180 pph. per cell with an R&R of 10% and a Cpk of 2.3.
Proportional Pressure Control Valve Calibration and Functional Test System
Application Requirements
Test parts are Pulse-Width Modulated (PWM) solenoid valves for diesel turbochargers. Valve calibration must regulate a 32.5 psig air supply to produce an outlet pressure of 20.5 ± 2.5 psig at 40% modulation. Fully closed, they must hold back 32.5 psig with pressure loss no greater than 2.5 psi per second equivalent to 2000 sccm leakage.
Test Process and Solution
InterTech’s design uses two test cells as testing is interrupted midway for valve potting. At the first cell, the operator scans the part’s Data Matrix bar code to set up the test database for that valve.
The operator then loads the part onto the fixture. The cell measures the coil resistance and conducts a 600 Vac. “Hi-Pot” test to a 5 mA. limit for 1 second. Next air pressure is applied to the inlet and the PWM module is set at 40% duty cycle. Voltage is adjusted until the coil current reaches 450 mA. A servo drive engages and turns the adjustment screw until the valve’s outlet pressure falls within the specification limits. The servo retracts. Modulation drops to zero before returning to 40% so that outlet pressure can be measured again. The valve is tested for leakage at zero modulation.
Accepted parts are removed to have potting compound applied to cover the calibration screw. Rejected parts are dropped through a chute into a lockbox for rework.
When potted valves resume testing at the second cell, another Date Matrix scan must transfer first-cell data before second-cell tests can proceed. After checking potting depth, inlet pressure is applied while the PWM driver ramps the modulation from zero through a sequence of up to 5 user-selectable steps, recording the outlet pressure delivered at each level and displaying them graphically.
The PWM driver then retraces its steps back down the percentage sequence establishing a second curve. The difference between curves permits the evaluation of hysteresis effects against user-selected limits. Current modulation then drops to zero and the valve is tested for leakage.
Accepted parts are ink marked automatically, while rejected parts have their threads deformed before the operator can remove and drop them into the reject chute.
Special Features
- InterTech designed PWM valve driver can supply up to 32 Vdc. at 3 amps. The user can select modulation frequency percentages digitally in 1% increments from 0 to 100%.
- Coil resistance measurement is automatically compensated for ambient temperature.
- User-friendly, password-protected HMI allows a technician to change test parameters, including hysteresis test point windows and Deadband limits.
- Reject chutes have sensor interlocks to eliminate the possibility of shipping defective products.
- InterTech employs a wide range of patented technology to ensure that it meets the highest ISO 17025 quality standards.
To reach an InterTech Applications engineer call 847-679-3377 x250 or CLICK HERE