Equivalent Circuit for Driving Piezoelectric Injectors

The activation of the fuel injector affects both engine performance and pollutant emissions. However, the automotive industry restricts access to information regarding the circuits and control strategies used in its vehicles. One way to optimize fuel injections is using piezoelectric injectors. These injectors utilize crystals that expand or contract when subjected to an electric current, moving the injector needle. They offer a response time up to four times faster than solenoid-type injectors and allow for multiple injections per combustion cycle. These characteristics result in higher combustion efficiency, reduced emissions, and lower noise levels, making piezoelectric injectors widely used in next-generation engines, where stricter emission and efficiency standards are required. This study aims to design a drive circuit for piezoelectric injectors in a common rail system, intended for use in a diesel injector test bench. Experimental measurement of voltage was obtained from an injector coupled to a running diesel engine. The developed equivalent circuit demonstrated the capability to drive piezoelectric injectors with voltage values close to those observed in a commercial injector installed in a diesel engine, validating its suitability for research and experimental applications. Additionally, injector operating curves were generated, evaluating the injected diesel mass flow rate for different energization times and injection pressure. The designed equivalent circuit successfully enabled the correct operation of piezoelectric injectors on the test bench, reproducing the expected charge and discharge behavior required for precise actuation.