Patent ID: 8336291
Filing Date: 2012-12-25
Classification: F01N,F02B,F02D,F02M,Y02T

Abstract:
1. An exhaust throttle valve diagnosing device for diagnosing mechanical failure of an exhaust throttle valve, which is provided with an intake throttle valve provided in an intake passage of an engine, the intake passage communicating with an exhaust passage of the engine through a recirculation passage of an exhaust recirculation device, and which is provided with a recirculation valve provided in the recirculation passage, and a turbocharger turbine having a variable turbo-vane and a normally fully opened exhaust throttle valve switchable to a predetermined close position provided in the exhaust passage downstream of the recirculation passage, comprising: engine revolution number detection means for detecting a revolution number of the engine; gas flow rate detection means for detecting a flow rate of a gas flowing through the intake passage or exhaust passage; storage means for storing a flow rate detected by gas flow rate detection means; and failure judgment means for, when switching the exhaust throttle valve from full opening to the closed position in order to warm up the engine, fixing the intake throttle valve to full opening, fixing the recirculation valve to full closing and fixing the variable turbo-vane to a predetermined opening degree so as to accelerate a gas flow rate from the intake passage to the exhaust passage, detecting a fully opened flow rate by the gas flow rate detection means, with the exhaust throttle valve at full opening, and storing this flow rate in the storage means, and then instructing the exhaust throttle valve to switch from full opening to the closed position for detecting a closed position flow rate by the gas flow rate detection means, and determining a judgment threshold value corresponding to the detected revolution number of the engine, wherein the judgment threshold value increases as the revolution number of the engine increases, determining a flow rate difference by deducting the detected closed position flow rate from a fully opened flow rate stored in the storage means, and judging a failure of the exhaust throttle valve when this flow rate difference is less than the determined judgment threshold value.