Particulate matter detection system
A particulate matter detection system detects a particulate matter in exhaust gas. The particulate matter detection system includes: a particulate matter detection sensor in which at least one detection portion is provided, the at least one detection portion including at least one pair of multiple electrodes and a deposition surface which is interposed between the pair of electrodes and which the particulate matter is deposited on; a capacitor connected to the at least one detection portion in series; a power supply configured to apply a direct voltage to a series body including the at least one detection portion and the capacitor; and a voltage measurement portion configured to measure a voltage of the capacitor.
1. A particulate matter detection system for detecting a particulate matter in exhaust gas, the particulate matter detection system comprising:
a particulate matter detection sensor in which at least one detection portion is provided, the at least one detection portion including
at least one pair of a plurality of electrodes and
a deposition surface which is interposed between the pair of electrodes and which the particulate matter is deposited on;
a capacitor connected to the at least one detection portion in series;
a power supply configured to apply a direct voltage to a series body including the at least one detection portion and the capacitor; and
a voltage measurement portion configured to measure a voltage of the capacitor that increases in response to charge stored in the capacitor from the power supply increasing when the pair of electrodes is conducted by the particulate matter; wherein
the particulate matter in the exhaust gas is detected based on a change in the voltage of the capacitor measured by the voltage measurement portion.
2. The particulate matter detection system according to claim 1 , wherein:
the particulate matter detection sensor and the capacitor are separately provided from each other.
3. The particulate matter detection system according to claim 1 , wherein:
the plurality of electrodes are arranged at a predetermined distance in the particulate matter detection sensor; and
both of the detection portion and the capacitor are provided by the plurality of electrodes.
4. The particulate matter detection system according to claim 3 , wherein:
the capacitor includes the pair of electrodes;
the particulate matter is deposited between the pair of electrodes and is deposited on a surface of the pair of electrodes.
5. The particulate matter detection system according to claim 3 , wherein:
a plurality of electrode pairs including the pair of electrodes adjacent to each other are provided in the particulate matter deposition sensor; and
a part of the electrodes among the plurality of electrode pairs has a deposition amount of the particulate matter, the deposition amount being smaller than a deposition amount that a remaining part of the electrode pairs has.
6. The particulate matter detection system according to claim 3 , wherein:
a plurality of electrode pairs including the pair of electrodes adjacent to each other are provided in the particulate matter deposition sensor; and
each of the electrode pairs has a different capacitance from each other between the pair of electrodes, the capacitances being different from each other.
7. The particulate matter detection system according to claim 3 , wherein:
the capacitor includes the pair of electrodes; and
at least one of the electrodes of the capacitor is covered with an insulation layer.
8. The particulate matter detection system according to claim 7 , further comprising:
a switch connected to the capacitor in parallel; and
a control portion configured to control an on-off operation of the switch,
wherein:
the control portion performs
an application process of applying a direct voltage of the power supply to the series body,
a discharge process of, after the application process, causing the switch to turn on and discharging charge stored in the capacitor, and
a measurement process of, after the discharge process, causing the switch to turn off and measuring the voltage of the capacitor.
9. The particulate matter detection system according to claim 7 , further comprising:
a series connector that
includes a resistor and the switch connected to the resistor in series and
is connected to the capacitor in parallel; and
a control portion configured to perform an operation control of the switch,
wherein:
the control portion
periodically switches on-off states of the switch,
measures a voltage drop of the resistor by utilizing the voltage measurement portion, and
determines that a large PM corresponding to the particulate matter having a particle diameter larger than 2.5 μm is deposited on the deposition surface when a time change rate of the voltage drop is higher than a predetermined value.
10. The particulate matter detection system according to claim 7 , further comprising:
a control portion configured to determine whether the particulate matter is deposited on the deposition surface,
wherein:
the control portion
measures a time increase rate of the voltage of the capacitor,
calculates a resistance between the pair of electrodes based on the measured time increase rate, and
determines that the particulate matter having a predetermined amount is deposited on the deposition surface when a value of the calculated resistance is lower than a predetermined threshold.
11. The particulate matter detection system according to claim 7 , further comprising:
a control portion configured to determine whether the particulate matter is deposited on the deposition surface,
wherein:
the control portion
measures a time increase rate of the voltage of the capacitor,
calculates a resistance between the pair of electrodes based on the measured time increase rate, and
determines that the particulate matter having a predetermined amount is deposited on the deposition surface when a value of the calculated resistance changes a predetermined time or more.
12. The particulate matter detection system according to claim 7 , further comprising:
a switch connected to the capacitor in parallel; and
a control portion configured to control an on-off operation of the switch, wherein:
the particulate matter detection sensor includes a heater configured to burn the particulate matter deposited on the deposition surface and remove the particulate matter; and
the control portion
measures a time increase rate of the voltage of the capacitor after removing the particulate matter by utilizing the heater; and
causes the switch to turn on at a predetermined time interval and periodically discharges the charge stored in the capacitor when the measured time increase rate is lower than a predetermined threshold.
13. The particulate matter detection system according to claim 12 , wherein:
the control portion determines that the particulate matter detection sensor is broken when the time increase rate is higher than the threshold.
14. A particulate matter detection system for detecting a particulate matter in exhaust gas, the particulate matter detection system comprising:
a particulate matter detection sensor in which at least one detection portion is provided, the at least one detection portion including
at least one pair of a plurality of electrodes and
a deposition surface which is interposed between the pair of electrodes and which the particulate matter is deposited on;
a capacitor connected to the at least one detection portion in series;
a power supply configured to apply a direct voltage to a series body including the at least one detection portion and the capacitor; and
a voltage measurement portion configured to measure a voltage of the capacitor; wherein:
the plurality of electrodes are arranged at a predetermined distance in the particulate matter detection sensor;
both of the detection portion and the capacitor are provided by the plurality of electrodes;
a plurality of electrode pairs including the pair of electrodes adjacent to each other are provided in the particulate matter deposition sensor; and
each of the electrode pairs has a different capacitance from each other between the pair of electrodes, the capacitances being different from each other.
15. A particulate matter detection system for detecting a particulate matter in exhaust gas, the particulate matter detection system comprising:
a particulate matter detection sensor in which at least one detection portion is provided, the at least one detection portion including
at least one pair of a plurality of electrodes and
a deposition surface which is interposed between the pair of electrodes and which the particulate matter is deposited on;
a capacitor connected to the at least one detection portion in series;
a power supply configured to apply a direct voltage to a series body including the at least one detection portion and the capacitor; and
a voltage measurement portion configured to measure a voltage of the capacitor; wherein:
the plurality of electrodes are arranged at a predetermined distance in the particulate matter detection sensor;
both of the detection portion and the capacitor are provided by the plurality of electrodes
the capacitor includes the pair of electrodes; and
at least one of the electrodes of the capacitor is covered with an insulation layer.
16. The particulate matter detection system according to claim 15 , further comprising:
a switch connected to the capacitor in parallel; and
a control portion configured to control an on-off operation of the switch,
wherein:
the control portion is further configured to perform:
an application process of applying a direct voltage of the power supply to the series body,
a discharge process of, after the application process, causing the switch to turn on and discharging charge stored in the capacitor, and
a measurement process of, after the discharge process, causing the switch to turn off and measuring the voltage of the capacitor.
17. The particulate matter detection system according to claim 15 , further comprising:
a switch connected to the capacitor in parallel; and
a control portion configured to control an on-off operation of the switch, wherein:
the particulate matter detection sensor includes a heater configured to burn the particulate matter deposited on the deposition surface and remove the particulate matter; and
the control portion is further configured to:
measure a time increase rate of the voltage of the capacitor after removing the particulate matter by utilizing the heater; and
cause the switch to turn on at a predetermined time interval and periodically discharges the charge stored in the capacitor when the measured time increase rate is lower than a predetermined threshold.
18. The particulate matter detection system according to claim 15 , further comprising:
a series connector that
includes a resistor and the switch connected to the resistor in series and
is connected to the capacitor in parallel; and
a control portion configured to perform an operation control of the switch,
wherein:
the control portion is further configured to:
periodically switch on-off states of the switch,
measure a voltage drop of the resistor by utilizing the voltage measurement portion, and
determine that a large PM corresponding to the particulate matter having a particle diameter larger than 2.5 μm is deposited on the deposition surface when a time change rate of the voltage drop is higher than a predetermined value.
19. The particulate matter detection system according to claim 15 , further comprising:
a control portion configured to determine whether the particulate matter is deposited on the deposition surface,
wherein:
the control portion is further configured to:
measure a time increase rate of the voltage of the capacitor,
calculate a resistance between the pair of electrodes based on the measured time increase rate, and
determine that the particulate matter having a predetermined amount is deposited on the deposition surface when a value of the calculated resistance is lower than a predetermined threshold.
20. The particulate matter detection system according to claim 15 , further comprising:
a control portion configured to determine whether the particulate matter is deposited on the deposition surface,
wherein:
the control portion is further configured to:
measure a time increase rate of the voltage of the capacitor,
calculate a resistance between the pair of electrodes based on the measured time increase rate, and
determine that the particulate matter having a predetermined amount is deposited on the deposition surface when a value of the calculated resistance changes a predetermined time or more.