Engine control system for working machine

Abstract

An engine control system for a working machine measures the sulfur content of an exhaust gas since sulfur is detrimental to normal functioning of an exhaust gas aftertreatment device. Each time a key switch is turned ON to start an engine, the engine control system compares a remaining fuel amount memorized at the last stop of the engine and a remaining fuel amount detected at the current start of the engine. The engine control system performs a sulfur concentration measurement process only when the remaining fuel amount is increased. A target revolution speed Na appropriate for measuring the concentration of sulfur is set and when the temperature of the exhaust gas is within a predetermined temperature range and a target time has elapsed, the engine control system determines whether the sulfur concentration exceeds a threshold value. If the sulfur concentration exceeds the threshold value, an alarm display device is activated.

1 . An engine control system for a working machine, the engine control system used in an exhaust gas purification system for a hydraulic operating machine having a diesel engine ( 1 ), an exhaust gas aftertreatment device ( 3 ) disposed in an exhaust system of the engine, and a hydraulic system ( 2 ) including a hydraulic pump ( 21 ) driven by the engine and at least one hydraulic actuator ( 23 ) driven by a hydraulic fluid discharged from the hydraulic pump, the engine control system comprising:
 an exhaust temperature detection device ( 33 ) for detecting the temperature of an exhaust gas of the engine;   a sulfur concentration detection device ( 36 ) for detecting the sulfur concentration in the exhaust gas of the engine;   an alarm device ( 42 ); and   a control device ( 51 ,  52 ) for performing a sulfur concentration measurement process in accordance with a value detected by the exhaust temperature detection device and with a value detected by the sulfur concentration detection device;   wherein, if, in the sulfur concentration measurement process, the exhaust gas temperature detected by the exhaust temperature detection device is within a predetermined temperature range appropriate for measuring the sulfur concentration in the exhaust gas, the control device measures the sulfur concentration in the exhaust gas of the engine by using the sulfur concentration detection device; and   wherein, if the measured sulfur concentration is not lower than a predetermined threshold value, the control device activates the alarm device.   
     
     
         2 . The engine control system for a working machine according to  claim 1 , further comprising:
 a key switch ( 46 ) for starting the engine ( 1 ); and   a fuel amount detection device ( 40 ) for detecting the amount of remaining fuel to be supplied to the engine;   wherein, each time the key switch turns ON to start the engine, the control device ( 51 ,  52 ) compares a remaining fuel amount memorized by a memory device ( 51   a ) at the last stop of the engine and a remaining fuel amount detected by the fuel amount detection device at the current start of the engine, and performs the sulfur concentration measurement process only when the remaining fuel amount is increased.   
     
     
         3 . The engine control system for a working machine according to  claim 1 , further comprising:
 an engine revolution speed designation device ( 41 ) for designating a target revolution speed of the engine ( 1 );   wherein, when the sulfur concentration measurement process is not to be performed, the control device ( 51 ,  52 ) exercises normal engine revolution speed control to control the revolution speed of the engine in accordance with the target revolution speed designated by the engine revolution speed designation device; and   wherein, when the sulfur concentration measurement process is to be performed, the control device ( 51 ,  52 ) exercises fixed control to forcibly set the revolution speed of the engine to a predetermined target revolution speed appropriate for measuring the sulfur concentration in the exhaust gas without regard to the target revolution speed designated by the engine revolution speed designation device.   
     
     
         4 . The engine control system for a working machine according to  claim 1 ,
 wherein, when the sulfur concentration is not lower than the predetermined threshold value, the control device ( 51 ,  52 ) brings the engine ( 1 ) to an automatic stop after the lapse of a predetermined period of time.   
     
     
         5 . The engine control system for a working machine according to  claim 2 , further comprising:
 an engine revolution speed designation device ( 41 ) for designating a target revolution speed of the engine ( 1 );   wherein, when the sulfur concentration measurement process is not to be performed, the control device ( 51 ,  52 ) exercises normal engine revolution speed control to control the revolution speed of the engine in accordance with the target revolution speed designated by the engine revolution speed designation device; and   wherein, when the sulfur concentration measurement process is to be performed, the control device ( 51 ,  52 ) exercises fixed control to forcibly set the revolution speed of the engine to a predetermined target revolution speed appropriate for measuring the sulfur concentration in the exhaust gas without regard to the target revolution speed designated by the engine revolution speed designation device.   
     
     
         6 . The engine control system for a working machine according to  claim 2 ,
 wherein, when the sulfur concentration is not lower than the predetermined threshold value, the control device ( 51 ,  52 ) brings the engine ( 1 ) to an automatic stop after the lapse of a predetermined period of time.   
     
     
         7 . The engine control system for a working machine according to  claim 3 ,
 wherein, when the sulfur concentration is not lower than the predetermined threshold value, the control device ( 51 ,  52 ) brings the engine ( 1 ) to an automatic stop after the lapse of a predetermined period of time.   
     
     
         8 . The engine control system for a working machine according to  claim 4 ,
 wherein, when the sulfur concentration is not lower than the predetermined threshold value, the control device ( 51 ,  52 ) brings the engine ( 1 ) to an automatic stop after the lapse of a predetermined period of time.