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knock sensor

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knock sensor

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knock sensor

  1. 1. Knock Sensor
  2. 2. What Is Knocking ? High frequency vibrations giving rise to ping like sound inside an Engine. Caused By : Low Quality Fuel Deposits on Cylinder Wall Wrong Spark Plug.
  3. 3. How Can It Be Prevented? Why do we care?? Knocks can rob power from the engine and worst, destroy the engine itself. How can we prevent knocking?? lower compression ratio, higher octane fuel, change driving habits or……MECHATRONICS! Need a tow??
  4. 4. The Sensor : Principle Knock Sensor Uses Piezoelectric Element. Works on Piezoelectric Effect. Piezoelectric elements generate voltage when pressure or vibration is applied to them. Piezoelectric Crystal Ceramics and single crystal materials: quartz, tourmaline and gallium phosphate
  5. 5. Working Of the Sensor Knock Sensors generate a voltage when vibration is applied to them utilizing the piezoelectric effect. Due to the vibration, a counter weight inside the sensor is applying pressure on the piezo- element, this pressure creates an electric charge in the piezo- element which is the output signal of the sensor. Knock Sensor
  6. 6. Knock Sensor Circuit Once signs of detonation are detected (i.e. knocking), the knock sensor sends a voltage signal to the engine control unit(ECU) which retards the spark timing slightly to avoid detonation. ECU
  7. 7. Benefits Vehicle engines work more efficiently and produce more power when operating near the detonation limit. Although simple, knock sensors allow optimum engine performance and protect the engine from potential damage caused by detonation.
  8. 8. Application Piezoelectric effect is found in many applications but knock sensors seem associated with the automotive industry. Knock control for internal combustion engines. Machine tool protection. Cavitations detection. Monitoring of pivot bearings. Anti theft systems.
  9. 9. Challenges (knocks) Piezoelectric elements can be sensitive to more than one physical dimension. Operate in harsh environment (dirt, grease, moisture, road salt, etc.) for automotive applications. Ceramic materials lack long term stability. Sensor can be fooled by things like bad water pump or alternator bearing, or a loose rod bearing.
  10. 10. References “Automotive approach” by system approach by Jack Erjavec. “ Design of Knock sensor” by Alexander A.Bazhenoy. “Total Automotive Technology” by Anthony E. Schaller.
  11. 11. THANK YOU Any Questions..?

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