Malfunction-determining device for exhaust gas purifying device and malfunction-determining method for exhaust gas purifying device

A malfunction-determining device for an exhaust gas purifying device, the exhaust gas purifying device comprising:

• a filter device being provided in an exhaust passage for exhaust gas exhausted from an internal combustion engine to remove a residual substance in the exhaust gas;
• and a pressure measuring device being provided to the filter device to measure a pressure of the exhaust gas, the malfunction-determining device comprising:
• a usability determiner being configured to determine whether or not the pressure measuring device is usable based on the pressure measured by the pressure measuring device and an exhaust gas flow rate;
• a frozen-state determiner being configured to determine whether or not the pressure measuring device is frozen;
• a malfunction determiner being configured to determine that the pressure measuring device has a malfunction when the usability determiner determines that the pressure measuring device is unusable and the frozen-state determiner determines that the pressure measuring device is not frozen;
• and
• a model-deposition-amount calculator being configured to calculate a theoretical amount of deposition of particulate matters in the filter device as a model-deposition-amount when the usability determiner determines that the pressure measuring device is not usable and the frozen-state determiner determines that the pressure measuring device is frozen.