CONTROL DEVICE, EXHAUST GAS PURIFICATION SYSTEM, AND CONTROL METHOD FOR ENGINE

A control device that can execute forced regeneration processing in an engine that comprises: a DOC and a DPF that are arranged on an exhaust flow channel of the engine; and a heating means that is for heating the DOC and the DPF and includes an exhaust throttle valve. The forced regeneration processing includes: first heating processing in which the heating means is controlled such that the DOC is heated to a first temperature; and second heating processing in which the heating means is controlled such that, after the first heating processing has been completed, the DPF is heated to a second temperature that is higher than the first temperature. The control device comprises a valve opening/closing operation execution part that, when a switch from the first heating processing to the second heating processing occurs, makes the exhaust throttle valve execute a valve opening/closing operation that makes the degree of opening of the exhaust throttle valve greater than a prescribed degree of opening for exactly a prescribed amount of time.