![]() Instead of using mechanical pump nozzles, piezo injectors use an actuator module made of thousands of wafers or discs, each made of piezo crystals. ![]() It’s this change in shape that makes piezoelectric crystals perfect actuators for diesel fuel injectors. More importantly, this also works the other way around: if you run an electric current through a piezo crystal, the crystal will change shape slightly. When mechanical stress is applied to certain crystals (for example, if it’s compressed or struck), an electrical charge is generated in the crystal. This is thanks to the piezoelectric effect, first discovered in 1880. Specifically, piezo crystals rapidly expand and contract. The unique attribute of piezo crystals such as quartz is that they change shape when exposed to an electrical current. Using certain crystals (known as piezo crystals), piezoelectric injectors are able to offer superior performance to traditional diesel injection systems while minimising the emissions and noise many associate with diesel. Piezoelectric injectors are highly efficient compared to traditional solenoid injectors, and are the beating heart of modern common-rail diesel engines. A Mercedes-Benz mechanic explains the science behind piezoelectric injectors Today, our Mercedes-Benz mechanics in Melbourne explain what these injectors are, and how they function. It’s no wonder that these systems are commonly found in many diesel-powered Mercedes vehicles.Īnd at the heart of these common-rail systems are piezoelectric injectors. This has several advantages most importantly, they allow for reduced emissions, better fuel consumption and less noise, all while delivering more power than traditional injection methods. Instead of using mechanically-operated pump nozzles to direct fuel, common-rail systems use high-pressure rails to direct fuel to each solenoid valve. Modern diesel Mercedes-Benz engines use common-rail direct injection. Each component in your Mercedes-Benz engine are highly-engineered, and designed to provide maximum performance.įuel injectors in particular are a crucial part of your Mercedes’ engine, responsible for delivering fuel to the engine’s combustion chamber. The device has been developed to solve a particular situation rising when testing piezo common rail injectors, as the piezo actuator must result lubricated before being energized.In addition to luxury, Mercedes-Benz vehicles are designed for performance and maximum efficiency. PiezoDevice 87.20.116 is the specific device to be used on an exhisting DIT31 test bench for diesel injectors. Piezo actuator control requires the addition of CRP module to the external unit TC38.Ĭonnection and test methods keeps unchanged contrary to the test of electromagnetic common rail injectors. The electromagnetic actuator control is delegated to the external unit TC38, which once synchronized with DIT31, generates the excitement command, via smartcards. The injector in the center has at least one of the nozzle holes with a reduced diameter by dirt or oxide while the nozzle holes of the injector on the right are expanded by wear. On the left, the injector injects the correct amount. This parameter, together with the injection time, determines the amount of the injected fluid. On the left an injector that pulverizes exactly on time, on the right an injector that responds with a delay.įor each chatter, at constant pressure DIT31 calculates the difference between the level of pressure on opening and closing of the nozzle. Injection time is the time elapsed between the opening and closing of the nozzle. Opening delay is the time to translate the electrical command into a mechanical movement The injector on the left has an acceptable quantity of return the other one on the right has an extra internal leakage. Known the acceptable leckage time, any lower value indicates a too high back leackage. With the injector pressurized, the pump is stopped and the pressure drops gradually, depending on the return. Piezoelectric actuator control requires the additional CRP module to the unit TC38.Īctivated the automatic triggering cycle, it is easy to find the minimum pressure which allows the chatter.Īctivated the automatic triggering cycle, it is easy to find the minimum pressure which allows the chatter pressure difference during the injection time the time interval between opening and closing of the nozzle (injection time). ![]() The most popular method to measure the flow of a common rail injector is to collect in a graduated glass the amount of liquid introduced during a known number of injections and compare this volume with the graduation of the container.Īn alternative able to provide higher resolution, is to split the flow in its two fundamental physical parameters: that is,
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