Diagnosis device and diagnosis method for turbocharger

Abstract

A diagnosis device for a turbocharger, the diagnosis device includes an electronic control unit. The electronic control unit is configured to calculate a turbine expansion ratio as a ratio of a pressure of the exhaust gas flowing into a turbine of the turbocharger to the pressure of the exhaust gas flowing out from the turbine; operate a deterioration evaluation value toward a predetermined one of an increase side and a decrease side when the turbine expansion ratio exceeds a threshold; and determine a replacement timing of a turbine component when a total operation amount of the deterioration evaluation is equal to or larger than a specified value, the total operation amount being an operation amount from an initial value of the deterioration evaluation value.

What is claimed is: 
     
         1 . A diagnosis device for a turbocharger, the turbocharger mounted on an engine, the turbocharger including a turbine, and the turbocharger being configured to supercharge intake air by driving the turbine with a flow force of exhaust gas of the engine, the diagnosis device comprising
 an electronic control unit configured to:   calculate a turbine expansion ratio as a ratio of a pressure of the exhaust gas flowing into the turbine to the pressure of the exhaust gas flowing out from the turbine;   operate a deterioration evaluation value toward a predetermined one of an increase side and a decrease side when the turbine expansion ratio exceeds a threshold; and   determine a replacement timing of a turbine component when a total operation amount of the deterioration evaluation is equal to or larger than a specified value, the total operation amount being an operation amount from an initial value of the deterioration evaluation value.   
     
     
         2 . The diagnosis device according to  claim 1 , wherein
 the electronic control unit is configured to operate the value of the deterioration evaluation value by a predetermined value every time the turbine expansion ratio exceeds the threshold.   
     
     
         3 . The diagnosis device according to  claim 1 , wherein
 the electronic control unit is configured to operate the value of the deterioration evaluation value to be increased as a difference between the threshold and the turbine expansion ratio increases when the turbine expansion ratio exceeds the threshold.   
     
     
         4 . The diagnosis device according to  claim 1 , wherein
 the specified value is lower at a low atmospheric pressure than at a high atmospheric pressure.   
     
     
         5 . A diagnosis method for a turbocharger, the turbocharger mounted on an engine, the turbocharger including a turbine, and the turbocharger being configured to supercharge intake air by driving the turbine with a flow force of exhaust gas of the engine, the diagnosis method comprising:
 calculating a turbine expansion ratio as a ratio of a pressure of the exhaust gas flowing into the turbine to the pressure of the exhaust gas flowing out from the turbine;   operating a deterioration evaluation value toward a predetermined one of an increase side and a decrease side when the turbine expansion ratio exceeds a threshold; and   determining a replacement timing of a turbine component when a total operation amount of the deterioration evaluation is equal to or larger than a specified value, the total operation amount being an operation amount from an initial value of the deterioration evaluation value.