Particulate matter detection sensor and control device of controlling the same

Abstract

A particulate matter (PM) detection sensor is placed in an exhaust gas pipe of a diesel engine. The PM sensor element has a detection part composed of a pair of detection electrodes and a heater part. The detection electrodes and the heater part are stacked in the PM sensor element. A control circuit instructs a heater power supply to supply electric power to the heater part when the diesel engine is started to operate. The heater part heats the detection part at a predetermined temperature T 1 within a range of 600° C. to 900° C. for a predetermined period S 1 of time, for example, 650° C. for 20 seconds, in order to burn and completely eliminate particulate matter accumulated in the detection part. This control process avoids incorrect detection of the PM detection sensor. After this process, the control circuit executes usual control of the PM detection sensor.

1 . A control device of controlling a particulate matter detection sensor placed in an exhaust gas pipe of an internal combustion engine through which exhaust gas emitted from the internal combustion engine flows and discharged to the outside, the particulate matter detection sensor having a particulate matter sensor element comprised of an insulation substrate, a detection part composed of a pair of detection electrodes formed on a surface of the insulation substrate, and a heater part of generating heat energy when receiving electric power in order to heat the detection part at a predetermined temperature,
 the control device comprising a control part which detects an electrical resistance value between the pair of the detection electrodes in the detection part, the electrical resistance value between the pair of the detection electrodes in the detection part changing in accordance with a change of quantity of particulate matter accumulated in the detection part, and the control part adjusting electric power supply to the heater part,   the control part comprising:
 combustion control means which executes combustion control when the internal combustion engine is started to operate, and in the combustion control, the combustion control means supplies electric power to the heater part in order to maintain the detection part of the particulate matter detection sensor at a predetermined temperature T 1  for a predetermined period S 1  of time in order to burn the accumulated particulate matter in order to eliminate the accumulated particulate matter from the detection part of the particulate matter detection sensor; and 
 usual control means which executes usual control after completion of the combustion control which is executed when the internal combustion engine is started to operate, wherein in the usual control, the usual control means supplies electric power to the heater part in order to maintain the detection part of the particulate matter sensor element at a temperature T 2  which is less than the predetermined temperature T 1  in order to detect particulate matter accumulated in the detection part. 
   
     
     
         2 . The control device according to  claim 1 , wherein the control part further comprises electric power supply timing means which determines a time to supply electric power to the heater part, counted from a time when the internal combustion engine is started to a time when the electric power is supplied to the heater part on the basis of the operation state of the internal combustion engine. 
     
     
         3 . The control device according to  claim 2 , wherein the electric power supply timing means calculates an amount of condensed water remained in the exhaust gas pipe adhering to the detection part in the particulate matter detection sensor, and delays the timing to supply the electric power to the heater part on the basis of the calculated amount of condensed water. 
     
     
         4 . The control device according to  claim 1 , wherein the combustion control means supplies the electric power to the heater part in order to maintain the detection part of the particulate matter detection sensor at the predetermined temperature T 1  within a range of not less than 600° C. to not more than 900° C. 
     
     
         5 . The control device according to  claim 4 , wherein the combustion control means supplies the electric power to the heater part in order to maintain the detection part of the particulate matter detection sensor at the predetermined temperature T 1  of not less than 650° C. for the predetermined period S 1  of time of not less than 20 seconds. 
     
     
         6 . The control device according to  claim 1 , wherein the usual control means supplies the electric power to the heater part in order to maintain the detection part of the particulate matter detection sensor at a predetermined temperature within a range of not less than 50° C. to not more than 600° C. 
     
     
         7 . The control device according to  claim 1 , wherein
 the detection part is comprised of the pair of the detection electrodes having a comb shape and detection lead parts formed on a front surface of the insulation substrate, and   the heater part is comprised of heater electrodes and heater lead parts formed at the front end in a back surface of the insulation substrate.