An exhaust purification system is provided with a NOx-occlusion-reduction-type catalyst and a NOx purge rich control unit that executes NOx purge in a case where a catalyst temperature of the NOx-occlusion-reduction-type catalyst is equal to or higher than a catalyst temperature threshold value and a NOx occlusion amount of the NOx-occlusion-reduction-type catalyst is equal to or higher than an NOx occlusion amount threshold value and executes the NOx purge even when the catalyst temperature is lower than a catalyst temperature threshold value in a case where the NOx occlusion amount is equal to or greater than the occlusion amount threshold value, a fuel injection amount resulting from an accelerator operation is equal to or greater than an injection amount threshold value, and an exhaust temperature detected by a first exhaust temperature sensor is equal to or higher than an exhaust temperature threshold value.

An engine-driven working machine includes a controller, which varies a control value of a solenoid valve so as to decrease or increase an opening degree of the solenoid valve when a rotating speed of an engine is within a predetermined high rotating speed range and the rotating speed of the engine is lower or higher than a predetermined rotating speed, respectively. In case the controller determines that the engine-driven working machine gets started saw cutting, the controller stops varying the control value of the solenoid valve when the rotating speed of the engine is within the predetermined high rotating speed range and lower than the target rotating speed.

An exhaust purification system includes: an NOx reduction type catalyst, which is provided in an exhaust passage; an intake air amount sensor, which detects an intake air amount of the internal combustion engine; and a controller, which executes a regeneration treatment that recovers an NOx purification capacity of the NOx reduction type catalyst by switching an exhaust air fuel ratio from a lean state to a rich state by using: an air-system control to reduce the intake air amount; and an injection-system control to increase a fuel injection amount, wherein, in response to a detection value of the intake air amount sensor, the controller changes at least one of a fuel injection timing and the fuel injection amount in the internal combustion engine, in at least one period of switching of: a period of starting the regeneration treatment; and a period of ending the regeneration treatment.

A system and method for preventing unauthorized modification to engine control software or an engine control system of, for example, a refrigerated transport application is provided. Particularly, the embodiments described herein prevent unauthorized parties from inadvertently or intentionally making changes to the engine control software used for controlling the engine or the engine control system that could, for example, potentially bypass emission strategies implemented in the refrigerated transport application. Accordingly, emission strategies such as, for example, EPA Tier IV not-to-exceed (NTE) regulations can be maintained.

It is determined whether the execution conditions for the injection quantity variation correction are met, based on whether all of following conditions are satisfied: the engine operation is the stationary operation, the injection quantity of a fuel injection valve falls within the predetermined range, and the fuel pressure falls within the predetermined range. When the execution conditions are met, the fuel pressure decrease caused by the fuel injection of the fuel injection valve for each cylinder is calculated based on the output of a fuel pressure sensor, and the injection quantity variation correction to correct the injection quantity variation of the fuel injection valve for each cylinder is performed based on the fuel pressure decrease caused by the fuel injection of each cylinder. Thus, the fuel pressure decrease can be accurately calculated, the injection quantity variation of each cylinder is precisely corrected.

An exhaust purification system includes a NOx-occlusion-reduction-type catalyst that occludes NOx in exhaust in a lean state and reduces and purifies the occluded NOx in exhaust in a rich state, and a NOx purge rich control unit that executes NOx purge of reducing and purifying the occluded NOx by putting the exhaust into the rich state by fuel injection control, where a catalyst temperature of the NOx-occlusion-reduction-type catalyst is equal to or higher than a catalyst temperature threshold value and a NOx occlusion amount of the NOx-occlusion-reduction-type catalyst is equal to or higher than an NOx occlusion amount threshold value, and executes the NOx purge when the catalyst temperature is lower than a catalyst temperature threshold value.

An exhaust purification system including a NOx catalyst 32 provided in an exhaust passage of an internal combustion engine 10 and purifying NOx in exhaust; a MAF sensor 40 for acquiring an air flow-rate of the internal-combustion engine 10; a control unit 60, 70 that execute catalyst regeneration treatment of recovering a NOx purification ability of the NOx catalyst 32 by performing, in combination, air-based control of reducing air flow-rate of the internal-combustion engine 10 to a predetermined target air flow-rate and injection-based control of increasing a fuel injection amount, wherein, in a case of executing the catalyst regeneration treatment, the control unit 60, 70 starts with the air-based control and starts the injection-based control when the air flow-rate acquired by the MAF sensor 40 is reduced to the target air flow-rate.

The embodiments include: a NOx occlusion/reduction catalyst which is provided to an exhaust passage of an internal combustion engine, occludes NOx in exhaust when the exhaust is in a lean state, and reduces and purifies occluded NOx when the exhaust is in a rich state; a NOx purging control unit which, when the exhaust is in the rich state, executes NOx purging in which the NOx occluded in the NOx occlusion/reduction catalyst is reduced and purified; and a NOx-purging-prohibition processing unit which, when at least one of a plurality of prohibition conditions is fulfilled, prohibits execution of catalyst regeneration processing by the NOx purging control unit even if a catalyst-regeneration-processing start request has been issued, and, when one of the prohibition conditions is fulfilled during execution of the catalyst regeneration processing, invalidates the prohibition condition and allows continued execution of the catalyst regeneration processing by the NOx purging control unit.

Feedback control is executed based on a measured CA10 and a measured CA50 that are calculated based on measured data for MFB. During steady operation a correlation index value I.sub.RA that shows a degree of correlation between the measured data and reference data corresponding thereto is calculated. During transient operation, a correlation index value I.sub.AA that shows a degree of correlation between the measured data and measured data that is measured immediately prior to the measured data is calculated. If the correlation index value I.sub.RA or the correlation index value I.sub.AA is less than a determination value I.sub.th, control is performed to prohibit reflection in the aforementioned feedback control of each of the measured CA10 and the measured CA50 which are measured in the combustion cycle in which the relevant correlation index value is calculated.

An internal combustion engine includes a turbocharger, a variable valve gear, an A/F sensor in an exhaust passage, A/F feedback control means, and scavenge A/F control means. The variable valve gear drives intake and exhaust valves, and can drive with a valve open characteristic with valve overlap. The A/F feedback control means performs feedback correction of a fuel injection amount based on an A/F sensor output, and acquires a learning value of information relating to A/F control from a feedback correction amount. The scavenge A/F control means carries out A/F control by a value learned during an operation of the engine with non-scavenge valve open characteristic, when the variable valve gear is operated with the scavenge valve open characteristic. The scavenge valve open characteristic has a valve overlap amount of such a degree that blow-by of intake air occurs in an intake stroke during a turbocharger operation.