Patent ID: 8276370

Claim:
A construction machine, comprising: an engine; a working implement operable as a result of driving of the engine; a reduction catalyst arranged in an exhaust gas line from the engine to purify and reduce nitrogen oxides in exhaust gas; a reducing agent tank in which a reducing agent to be fed to the exhaust gas line is stored; a temperature detector operatively arranged to detect a temperature of the reducing agent in the reducing agent tank; an air conditioner providing an air condition in an operator's cab; a control device operatively arranged in the operator's cab to control the air condition; a first air blow line operatively arranged to guide warm/cold air from the air conditioner to the operator's cab; a switching device operatively arranged to switch a flow of the warm/cold air blown out of the air conditioner such that a portion of the warm/cold air from the air conditioner is fed into the operator's cab through the first air blow line; and a warm/cold air guide system comprising: a second air blow line operatively arranged to guide the warm/cold air from the air conditioner to the reducing agent tank; and a electronic controller having operative logic that outputs a warm air signal or a cold air signal, which corresponds to a temperature of the warm/cold air blown out of the air conditioner in accordance with the temperature of the reducing agent as detected by the temperature detector, as a control signal for the air conditioner; the operative logic of the controller being configured to; (a) in a state where the control device is not operating, the controller outputs the cold air signal when the temperature of the reducing agent is higher than a first predetermined temperature or outputs the warm air signal when the temperature of the reducing agent is lower than a second predetermined temperature which is lower than the first predetermined temperature, to guide the warm/cold air blown out of the air conditioner to the reducing agent tank through the second air blow line; (b) while in a state where the control device is not operating, the controller outputs a stop signal when the temperature of the reducing agent is higher than the second predetermined temperature but is lower than the first predetermined temperature; and (c) upon operating the control device, the controller outputs a control signal for the air-conditioner and controls the switching device such that a portion of the warm/cold air blown out of the air conditioner is fed to the first air blow line when the temperature of the reducing agent is within a range of the predetermined temperature.