Piezo Valves; Recommended Test Sequence - Hartridge HK900 Operating Manual

Operating Manual
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3.2.2 Piezo Valves

These use the inherent properties of piezo crystals (that they deflect with applied voltage) to activate
the valve. There is a positive current pulse (I) to switch the valve on, and a negative current pulse to
switch the valve off. The overall pulse width (T) is the time between the positive and negative current
pulses.
Siemens were the first manufacturer to introduce piezo injectors, the main advantage over solenoid
valves being that piezo valves have a much faster response time.

3.3 Recommended Test Sequence

The recommended test sequence for Common Rail injectors is as follows:
1. Initial Check
2. Cleaning and Repair
3. Re-do initial Check
4. Final Test
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Figure 3.2: Solenoid Injector Drive Signal
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Figure 3.3: Piezo Injector Drive Signal
Use a Testmaster (HH701) and Signal Unit (HK85x) to check the basic
operation of the injector and the nozzle spray pattern.
If required, clean the nozzle in an ultrasonic tank, or dismantle the
injector and replace faulty components. Any dismantling and reassembly
should be done in a clean environment.
Re-check the injector on a Testmaster after cleaning/repair.
Carry out a full delivery, backleak, and response time test on the
injectors using the HK900 and HK901kits.
HARTRIDGE LIMITED
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HL030(EN), Issue 1, June 2005