Chain tensioner with a sensor that detects excessive chain elongation

摘要

A hydraulic chain tensioner 14, for a valve train chain 11 of an internal combustion engine in a vehicle, comprises a piston 15 that presses a blade on the chain 11 so as to maintain the chain 11 in tension. A sensor 16 detects an axial position of the piston 15 proportional to chain elongation and transmits an alert signal if the chain elongation is excessive. The alert signal from the sensor 16 is transmitted to an electronic control unit (ECU) 20 of the vehicle. Sensor 16 detects micro-displacements in order to evaluate a velocity of the piston 16 and thereby a vibrational state of the chain 11. A method for monitoring the chain elongation is also disclosed, the method includes a phase in which the alert signal is sent if chain elongation is above a predetermined threshold and a corrective action impacting on an ignition fuel strategy is performed. The method uses a computer program product comprising control apparatus in which a computer program having computer-code is stored.