Exhaust gas purification system for hydraulic operating machine

Abstract

When an output value of an exhaust resistance sensor 34 has reached or exceeded a set value ΔPa, a controller 20 executes recovery control of a filter of an exhaust gas purification device 32 after conducting exhaust temperature increasing control by operating a pump discharge pressure increasing device (solenoid proportional valve) 38 so that exhaust gas temperature as an output value of an exhaust temperature sensor 33 reaches a preset value Ta. Thus, the recovery process of the exhaust gas purification device can be executed with reliability by increasing the exhaust gas temperature irrespective of the operating environment and the fuel consumption can be kept at a minimum necessary level.

1 . An exhaust gas purification system for a hydraulic operating machine equipped with a diesel engine ( 1 ), an exhaust gas purification device ( 32 ) provided in an exhaust line ( 31 ) of the engine, a variable displacement hydraulic pump ( 2 ) driven by the engine, a pump displacement adjusting device ( 14 ,  14 A) for controlling the displacement of the hydraulic pump, and at least one hydraulic actuator ( 25 ) driven by hydraulic fluid discharged from the hydraulic pump, comprising:
 an exhaust resistance sensor ( 34 ) for detecting exhaust resistance of the exhaust gas purification device ( 32 );   an exhaust temperature sensor ( 33 ) for detecting temperature of exhaust gas in the exhaust gas purification device;   a pump discharge pressure increasing device ( 38 ) provided in a hydraulic line ( 2   a ), through which the hydraulic fluid discharged from the hydraulic pump ( 2 ) flows, for increasing discharge pressure of the hydraulic pump; and   a recovery control device ( 20 ,  20 A) for executing recovery of the exhaust gas purification device by combusting and removing particulate matter accumulated in the exhaust gas purification device when the exhaust resistance detected by the exhaust resistance sensor has reached or exceeded a set value,   wherein the recovery control device includes an exhaust temperature increasing control device ( 20 ,  20 A) which increases the exhaust gas temperature so as to make the exhaust gas temperature detected by the exhaust temperature sensor reach a preset value by increasing absorption torque of the hydraulic pump by operating at least the latter one of the pump displacement adjusting device ( 14 ,  14 A) and the pump discharge pressure increasing device ( 38 ) when the exhaust resistance detected by the exhaust resistance sensor has reached or exceeded the set value.   
     
     
         2 . The exhaust gas purification system for a hydraulic operating machine according to  claim 1 , wherein the exhaust temperature increasing control device ( 20 ,  20 A) controls an operation amount of at least the latter one of the pump displacement adjusting device ( 14 ,  14 A) and the pump discharge pressure increasing device ( 38 ) so that an increment of the absorption torque of the hydraulic pump ( 2 ) amounts to 20%-30% of maximum torque of the engine ( 1 ). 
     
     
         3 . The exhaust gas purification system for a hydraulic operating machine according to  claim 1 , wherein the exhaust temperature increasing control device ( 20 , 20 A) includes an exhaust temperature adjusting device which adjusts at least one selected from an operation amount of the pump displacement adjusting device ( 14 ,  14 A), an operation amount of the pump discharge pressure increasing device ( 38 ) and an increment of revolution speed of the engine so that the exhaust gas temperature remains within a preset range after the exhaust gas temperature detected by the exhaust temperature sensor ( 33 ) has been increased to the preset value. 
     
     
         4 . The exhaust gas purification system for a hydraulic operating machine according to  claim 1 , wherein the recovery control device is an automatic recovery control device ( 20 ,  20 A) which automatically starts operation when the exhaust resistance detected by the exhaust resistance sensor has reached or exceeded the set value. 
     
     
         5 . The exhaust gas purification system for a hydraulic operating machine according to  claim 4 , further comprising operation detecting means for detecting whether the hydraulic actuator ( 25 ) is being driven or not,
 wherein the exhaust temperature increasing control device ( 20 ,  20 A) increases the exhaust gas temperature by increasing the absorption torque of the hydraulic pump by operating at least the latter one of the pump displacement adjusting device ( 14 ,  14 A) and the pump discharge pressure increasing device ( 38 ) when the hydraulic actuator ( 25 ) is being driven.   
     
     
         6 . The exhaust gas purification system for a hydraulic operating machine according to  claim 5 , wherein when the hydraulic actuator ( 25 ) is not being driven, the exhaust temperature increasing control device ( 20 ,  20 A) increases the exhaust gas temperature by increasing revolution speed of the engine to a preset revolution speed and increasing the absorption torque of the hydraulic pump ( 2 ) by operating the pump displacement adjusting device ( 14 ,  14 A) and the pump discharge pressure increasing device ( 38 ). 
     
     
         7 . The exhaust gas purification system for a hydraulic operating machine according to  claim 1 , further comprising:
 operation permission state detecting means ( 13 ) for detecting whether the hydraulic operating machine is in an operation permission state or not; and   manual recovery instruction means ( 36 ), wherein:   the recovery control device is a manual recovery control device ( 36 ,  20 ,  20 A) which issues an alarm when the exhaust resistance detected by the exhaust resistance sensor ( 34 ) has reached or exceeded the set value and starts operation when the operation permission state detecting means detects that the hydraulic operating machine is not in the operation permission state and there is an instruction by the manual recovery instruction means, and   the exhaust temperature increasing control device ( 20 ,  20 A) increases the exhaust gas temperature by increasing revolution speed of the engine to a preset revolution speed and increasing the absorption torque of the hydraulic pump ( 2 ) by operating the pump displacement adjusting device ( 14 ,  14 A) and the pump discharge pressure increasing device ( 38 ).   
     
     
         8 . The exhaust gas purification system for a hydraulic operating machine according to  claim 4 , wherein the exhaust temperature increasing control device ( 20 ,  20 A) previously stores an exhaust resistance threshold value, for judging whether the recovery of the exhaust gas purification device by the automatic recovery control device ( 20 ,  20 A) is necessary or not, as a function of engine revolution speed and an engine load, determines the exhaust resistance threshold value by referring to current engine revolution speed and engine load and inputting them to the function, and sets the determined exhaust resistance threshold value as the set value. 
     
     
         9 . The exhaust gas purification system for a hydraulic operating machine according to  claim 4 , wherein the automatic recovery control device ( 20 ,  20 A) sets the set value of the exhaust resistance at a lower value when the hydraulic actuator is not being driven compared to cases where the hydraulic actuator is being driven. 
     
     
         10 . The exhaust gas purification system for a hydraulic operating machine according to  claim 1 , wherein:
 the recovery control device includes an automatic recovery control device ( 20 ,  20 A) which automatically starts operation when the exhaust resistance detected by the exhaust resistance sensor has reached or exceeded the set value and a manual recovery control device ( 36 ,  20 ,  20 A) which issues an alarm when the exhaust resistance detected by the exhaust resistance sensor ( 34 ) has reached or exceeded the set value and starts operation when the operation permission state detecting means detects that the hydraulic operating machine is not in the operation permission state and there is an instruction by the manual recovery instruction means, and   the set value in the automatic recovery control device ( 20 ,  20 A) is set lower than the set value in the manual recovery control device ( 36 ,  20 ,  20 A).