JP2011203093A - Gas sensor, and disconnection detection method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gas sensor that detects concentration of conductive fine particles contained in gas to be measured, has no dead period, rapidly detects a disconnection failure, and has high reliability, and to provide a disconnection detection method of the same.SOLUTION: As a disconnection detecting means for detecting the existence of disconnection of conduction routes (111-117 and 121-127) connecting between a detection part 11 and a resistance measuring means 60, a disconnection detecting resistor 13 having a predetermined resistance value Ris disposed on an anti-resistance measuring means side so that the resistor conducts a pair of detection electrodes 110 and 120 to each other and is parallel to a detecting resistor Rformed between the detection electrodes (110 and 120).

Description

  The present invention relates to a gas sensor for detecting conductive fine particles contained in a gas to be measured such as combustion exhaust gas of an internal combustion engine, and a disconnection detection method for early detection of disconnection abnormality of the gas sensor.

In recent years, diesel engines and gasoline lean burn engines have been combined with common rail fuel injection systems, supercharger systems, oxidation catalysts, diesel particulate filter DPF, selective catalytic reduction (SCR) systems, exhaust gas recirculation (EGR) systems, etc. Reduction of environmentally hazardous substances such as nitrogen oxides NOx, particulate matter PM, unburned hydrocarbons HC, etc. contained in combustion exhaust gas such as the above.
The DPF used in such a system generally has a honeycomb structure made of porous ceramics having excellent heat resistance and countless pores, and PM is contained in the pores existing in the porous partition walls. When trapped, PM accumulates, clogs the pores and the pressure loss increases, it is heated in the DPF by heating with a burner or heater, or by post injection that injects a small amount of fuel after the combustion explosion of the engine. The combustion exhaust gas is introduced, the DPF is heated, and PM collected in the DPF is burned and removed to be regenerated.
In order to further improve the combustion efficiency of the internal combustion engine, determination of the DPF regeneration timing, OBD (on-board diagnosis, in-vehicle fault diagnosis device) for detecting deterioration, breakage, etc. of the DPF, feedback of the internal combustion engine In control and the like, there is a need for a gas sensor that can continuously detect PM contained in combustion exhaust gas with high accuracy. Furthermore, when using such a gas sensor for detecting PM, there is a demand for reliable fail-safe against a failure of the gas sensor.

  As a means for detecting PM in combustion exhaust gas, Patent Document 1 discloses that a pair of electrodes is formed on the surface of a substrate having heat resistance and electrical insulation, and a gap between the electrodes is used as a detection unit. A heating element is formed inside, and the conductive portion excluding the electrode, the detection portion, and the terminal portion forming the detection portion on the substrate is covered with a protective layer made of an airtight and electrically insulating material, and the detection portion, the protective layer, A smoke density sensor is disclosed in which the heat generation density of a heating element in the vicinity of the boundary is made higher than the heat generation density of the detection unit, and the temperature of the detection unit is heated to 400 ° C. or more and 600 ° C. or less. .

  However, in the conventional smoke concentration sensor as disclosed in Patent Document 1, the electrical resistance between the pair of electrodes that changes due to the deposition of conductive smoke is detected by an electronic circuit, but the smoke is not deposited. In this case, since the pair of electrodes is in an insulated state, there is a dead period until the electrical resistance between the pair of electrodes gradually decreases due to the deposition of smoke and the electrical resistance can be detected by the electronic circuit.

  As a method for solving the problem of such a dead period, Patent Document 2 discloses a detection device for detecting fine particles in a gas flow, and includes an electrode pair including at least two electrodes formed on a substrate. And at least two electrodes of the electrode pair are covered with a conductive layer, and the resistance value of the conductive layer is equal to or less than the minimum value of the resistance value formed by the fine particles in the measurement gas. A fine particle detection apparatus characterized by the above is disclosed.

  Further, in Patent Document 3, in such a particle detection apparatus, a reference electrode pair is provided separately from a detection electrode pair for detecting particles in a gas flow, and a current flowing between the detection electrode pair is disclosed. And a detection apparatus and an abnormality detection method for recognizing a disconnection when the ratio or difference between the current flowing between the reference electrode pair and the reference electrode pair exceeds a predetermined threshold value are disclosed.

However, as disclosed in Patent Document 2, the insensitive period until the resistance formed by the fine particles deposited between the electrodes can be detected by conducting between the electrodes by the conductive layer formed so as to cover the two electrodes. In order to solve the problem, it is necessary to maintain a resistance value in a very narrow range as the resistance value of the conductive layer.
However, in such a fine particle detection apparatus, it is necessary to heat and burn away the fine particles deposited on the detection electrode pair. For this reason, when heating is repeated by long-term use, migration in which the metal component moves between the conductive layer and the electrode occurs, and the resistance value of the conductive layer changes. The change in the resistance value of the conductive layer affects the detection result, and there is a possibility that the fine particles in the gas flow cannot be accurately detected.
Moreover, in such a detection apparatus, since both electrodes are electrically connected to each other by the conductive layer, even if a disconnection abnormality occurs in one or both of the two electrodes, the disconnection is caused by the conductive layer. A disconnection abnormality cannot be detected because a conductive path that conducts the portion is formed.

Further, as disclosed in Patent Document 3, when it is attempted to detect the presence or absence of disconnection of the detection electrode pair by comparison with the reference electrode pair, the number of electrode pairs that is double that in the case of detecting particles with a conventional pair of electrodes Therefore, there is a risk of increasing the manufacturing cost.
Furthermore, there is a possibility that the disconnection of the reference electrode pair itself cannot be detected.

  Therefore, in view of such circumstances, the present invention has a highly reliable gas sensor that detects the concentration of conductive fine particles contained in the gas to be measured with a simple configuration without a dead period and can quickly detect a disconnection abnormality. An object of the present invention is to provide a gas sensor and a method for detecting disconnection thereof.

In the first invention, at least a detection unit provided with a pair of detection electrodes facing each other with a predetermined gap provided on the surface of the electrically insulating heat-resistant substrate exposed to the gas to be measured, and a heating unit for heating the detection unit And a resistance measuring means for measuring the electrical resistance between the detection electrodes, which varies depending on the amount of the conductive fine particles detected by the fine particle detection element, and the conductivity in the gas to be measured. In the gas sensor that detects the concentration of functional fine particles,
As a disconnection detection means for detecting the presence or absence of disconnection of a conduction path connecting the detection unit and the resistance measurement means, the disconnection detection resistor having a predetermined resistance value is electrically connected to the pair of detection electrodes, and the detection electrode It is provided on the side of the anti-resistance measuring means so as to be parallel to the detection resistor formed therebetween.

According to the first invention, since the detection resistor formed in the detection unit by the deposition of the fine particles and the disconnection detection resistor are connected in parallel, the combined resistance thereof is reduced and detected by the resistance measurement unit. In this case, the current flowing in the fine particle detection element can be increased to a value higher than the detection limit of the resistance measuring means, and the dead time can be eliminated.
In addition, since the energization path connecting the detection unit and the resistance measuring unit is connected in series via the disconnection detection resistor, the detection unit is detected when a disconnection occurs in the energization path. Immediately after the fine particles deposited on the substrate are heated by the heating unit and the fine particles are burned and removed, the output voltage becomes 0. Therefore, it is possible to reliably detect the disconnection of the energization path connecting the detection unit and the resistance measuring means. It becomes possible to take measures to eliminate the abnormality by promptly warning the abnormality.

  In the second invention, the pair of detection electrodes are formed in a comb-teeth shape from which a plurality of electrodes protrude and are made to face each other.

  According to the second invention, as in the first invention, in addition to the elimination of the dead period, the output voltage is increased when a disconnection occurs in the energization path other than the portion where the fine particles of the detection unit are deposited. Since it becomes 0, it becomes possible to detect disconnection.

  In a third aspect of the invention, part of the pair of detection electrodes is bent in a crank shape so as to face each other (claim 3).

  According to the third invention, in the same way as the first invention, the dead period can be eliminated, and all the energization paths connecting the detection unit and the resistance measurement means including the pair of detection electrodes can be performed. Therefore, when the disconnection occurs in either the detection electrode or the energization path, it is any place in the detection electrode and the energization path. However, immediately after the fine particles deposited on the detection unit are heated and removed by the heating unit, the output voltage becomes 0. Therefore, it is possible to detect the disconnection reliably and to promptly warn of an abnormality. Therefore, it is possible to take measures for eliminating the abnormality and to realize a more reliable gas sensor.

  In the fourth invention, the disconnection detection resistor is placed at a thermally stable position.

  According to the fourth invention, the resistance value of the disconnection detection resistor is stabilized, and disconnection detection can be performed reliably.

  In a fifth aspect of the invention, a thermistor having a temperature sensitive characteristic is used as the disconnection detection resistor, and is provided on the detection unit side.

  According to the fifth invention, in addition to the same effect as the first invention, it becomes possible to detect the temperature of the detection unit, and the temperature management of the detection unit and the temperature control of the heating unit at the time of detecting the fine particles are further improved. It can be realized accurately, and a more reliable gas sensor can be realized.

In the sixth invention, at least a detection unit provided with a pair of detection electrodes opposed to each other by being exposed to the gas to be measured and providing a predetermined gap on the surface of the electrically insulating heat-resistant substrate, and a heating unit for heating the detection unit, And a resistance measuring means for measuring the electrical resistance between the detection electrodes, which varies depending on the amount of the conductive fine particles detected by the fine particle detection element, and the conductivity in the gas to be measured. A disconnection detection method for a gas sensor for detecting the concentration of conductive fine particles,
As the disconnection detecting means for detecting the presence or absence of disconnection of the conduction path connecting the detection section and the resistance measuring means, the gas sensor conducts the pair of detection electrodes and detects formed between the detection electrodes. Provided with a disconnection detection resistor having a predetermined resistance value provided in parallel with the resistor,
At least disconnection determination means for detecting the presence or absence of disconnection by comparing an output voltage detected by a combined resistance of the detection resistor and the disconnection detection resistor with a predetermined threshold value, and the output voltage exceeds the predetermined threshold value. If it is detected, it is determined that the wire is disconnected (claim 6).

According to the sixth aspect of the present invention, if no disconnection occurs, at least conduction is ensured by the disconnection detection resistor. Therefore, the output voltage is always generated, and the output voltage is set to the predetermined value in consideration of an error. When the threshold value is exceeded, it can be determined that the wire is surely disconnected.
Whether the output voltage is determined to be a disconnection when the output voltage is equal to or higher than the predetermined threshold or whether the output voltage is equal to or lower than the predetermined threshold is determined as to whether the resistance measuring unit is provided on the high side or the low side with respect to the detection resistor. The output voltage can be changed as appropriate depending on whether the output voltage is inverted output or non-inverted output, and whether the threshold is provided on the high side or the low side with respect to the output voltage.

  In a seventh aspect of the invention, the combustion of the particulates is completed using one or both of a combustion stroke in which particulates accumulated on the detection portion are burned and removed by the operation of the heating portion, and the combustion time and the output of the particulate detection element. It is provided with a particulate combustion completion judging means for judging, and a disconnection judging means for judging the presence or absence of disconnection based on the presence or absence of the output of the particulate detection element after confirming the combustion of the particulates. (Claim 7).

  According to the seventh aspect, it is possible to determine the presence or absence of disconnection in a state where the fine particles are reliably removed by combustion.

The outline | summary of the gas sensor containing the microparticle detection element in the 1st Embodiment of this invention is shown, (a) is an expansion | deployment perspective view, (b) is an equivalent circuit schematic of the detection part at the time of PM deposition, (c) is The equivalent circuit diagram of the detection part after PM combustion. The expansion | deployment perspective view which shows the modification of the microparticle detection element in the 1st Embodiment of this invention. Sectional drawing which shows the outline | summary of the whole gas sensor using the microparticle detection element in the 1st Embodiment of this invention from two directions. The expansion | deployment perspective view which shows the other modification of the microparticle detection element in the 1st Embodiment of this invention. The outline | summary of the other modification of the microparticle detection element in the 1st Embodiment of this invention is shown, (a) is the perspective view seen from the detection part side, (b) is the perspective view seen from the back surface side. The expansion | deployment perspective view which shows the other modification of the microparticle detection element in the 1st Embodiment of this invention. The outline of the gas sensor containing the particulate detection element in the 2nd embodiment of the present invention is shown, (a) is a development perspective view, (b) is an equivalent circuit diagram of the detection part at the time of PM deposition, (c), The equivalent circuit diagram of the detection part after PM combustion. The modification of the microparticle detection element in the 2nd Embodiment of this invention is shown, (a) is a top view, (b) is the sectional drawing, (c) is a top view which shows the other modification, (b) ) Is a cross-sectional view thereof. The modification of the detection part in the 2nd Embodiment of this invention is shown, (a) is an equivalent circuit diagram using a constant current power supply, (b) is an equivalent circuit diagram using a low voltage power supply. It is a flowchart which shows the disconnection detection method used for the gas sensor of this invention, Comprising: (a) is the most basic flowchart, (b) is the flowchart which aimed at more reliable disconnection detection. The flowchart which shows the disconnection detection method used for the gas sensor of this invention. The characteristic view which shows the dead period elimination effect of the microparticle detection element of this invention with a comparative example. The disconnection detection effect of the gas sensor of this invention is shown, (a) is a characteristic diagram when a disconnection occurs in a portion other than the detection unit, (b) is a characteristic diagram when a disconnection occurs in the detection unit.

With reference to FIG. 1, the outline | summary of the fine particle detection element 10 in the 1st Embodiment of this invention and the gas sensor 1 which has this is demonstrated.
The particulate detection element 10 according to the first embodiment of the present invention is, for example, a failure of a diesel particulate matter filter (DPF) that collects particulate matter (PM) contained in combustion exhaust discharged from a diesel internal combustion engine. In order to perform diagnosis (OBD) and DPF regeneration control, the gas sensor 1 is used to detect the concentration of PM in combustion exhaust gas, particularly, conductive fine particles.
The fine particle detection element 10 has a detection resistor R _SEN that varies depending on the amount of PM deposited on the detection unit 11 formed by a pair of detection electrodes 110 and detection electrodes 120 facing each other with a predetermined gap. It is measured by the measuring means 60 and PM in the gas to be measured is detected. The detection electrode 110 and the detection electrode 120 are formed in a comb-like shape in which a plurality of electrodes protrude from the lead portions 111 and 121, respectively, and are opposed to each other, so that PM is deposited between the electrodes.
The particle detection element 10 of the present invention includes a detection unit 11 and a heating unit 14, and the gas sensor 1 measures the particle detection element 10 and a detection resistor R _SEN formed in the detection unit 11 of the particle detection element 10. The resistance measurement means 60 and the detection unit 11 are heated to a predetermined temperature to control the energization to the heating unit 14 for stabilizing the detection resistance R _SEN and heating and removing the PM deposited on the detection unit 11. The heater control means 61 that performs the disconnection determination control and the like that will be described later according to the output voltage _VOUT from the resistance measurement means 60.

As shown in FIG. 1B, the greatest feature of the particle detection element 10 according to the first embodiment of the present invention is through a disconnection detection resistor 13 having a predetermined offset resistance value R _OFFSET as a disconnection detection means. The disconnection detection resistor 13 is provided on the anti-resistance measuring means side so as to be electrically connected to the detection electrode 110 and the detection electrode 120 and to be parallel to the detection resistor R _SEN .
By adopting such a configuration, the combined resistance R _SUM (= R _OFFSET · R _SEN / (R _OFFSET + R _SEN )) of the offset resistance R _OFFSET and the detection resistance R _SEN of the disconnection detection resistance 13 is lowered, and the combined resistance When the output voltage V _OUT dropped by R _SUM is detected by the voltage dividing resistor R ₁ provided as the resistance measuring means 60, the current flowing through the fine particle detection element 10 is raised to the detection limit or more of the resistance measuring means 60, and the dead period is increased. Can be resolved.
Particulate PM is deposited in the detection unit 11, when it becomes saturated becomes much smaller than the detection resistor _{R SEN} disconnection detection resistor _{R OFFSET,} detection resistor _{R SEN} and disconnection detection power supply voltage _{V CC} It can be detected as an output voltage V _OUT proportionally divided by the combined resistance R _SUM with the resistor R _OFFSET and the voltage dividing resistor R _1, and when the particulate PM deposited on the detection unit 11 is removed by combustion, the detection resistance RSEN large becomes much as compared with the disconnection detection resistor _{R OFFSET,} it can be detected as the output voltage _{V OUT} that is prorated by the power supply voltage _{V CC} disconnection detection resistor _{R OFFSET} voltage dividing resistor R1.
In addition, as shown in FIG. 1 (c), the energization paths (111 to 117, 121 to 127) connecting the detection unit 11 and the resistance measurement unit 60 are connected in series via the disconnection detection resistor 13. Therefore, when a disconnection occurs in any one of the energization paths (111 to 117, 121 to 127), immediately after the PM accumulated on the detection unit 11 is burned and removed, the energization path is interrupted by the disconnection point and the resistance is measured. Since there is no continuity with the means, it is possible to easily detect a disconnection, and it is possible to take measures to eliminate the abnormality by promptly warning the abnormality.
In the present embodiment, the disconnection of the energization path connecting the detection unit 11 and the resistance measuring unit 60 can be detected, but the disconnection of the detection electrodes 110 and 120 itself cannot be detected.

Based on the output voltage _VOUT detected by the resistance measuring means 60, the electronic control unit 70 grasps the amount of PM in the gas to be measured, feeds it back to the operating conditions of the internal combustion engine, and detects fine particles according to the amount of PM. The detection condition of the element 10 is determined, the necessity of regeneration of the particle detection element 10 is determined, the condition for energizing the heater 140 is determined, and the particle detection element 10 It is determined whether or not there is a disconnection in the energization path connecting the resistance measuring means 60.

More specifically, the detection unit 11 includes an electrically insulating heat resistant substrate 100, a pair of the detection electrode 110 and the detection electrode 120 provided on the electrically insulating heat resistant substrate 100 with a predetermined distance therebetween, and It is an essential part, and is constituted by a disconnection detection resistor 13 provided as a disconnection detection means for connecting the detection electrode 110 and the detection electrode 120.
In the present embodiment, the detection electrode 110 and the detection electrode 120 are connected to lead portions 111 and 121 that are electrically connected to the external resistance measuring means 60, and the plurality of detection electrodes 110 and the detection electrodes 120 are alternately arranged. Comb teeth are formed so as to face each other.
Further, terminal portions 112 and 122 are formed at the output side end portions of the lead portions 111 and 121, and are connected to the external resistance measuring means 60 via the connection fittings 115, 116, 125, and 126, and the conductive lines 117 and 127. Has been.
In addition, the end of the lead portions 111 and 121 opposite to the output side is a main portion of the present invention, and is arranged in parallel with the detection resistor R _SEN formed by PM deposited between the detection electrodes. The disconnection detection resistor 13 having both the resistance value R _OFFSET and serving as both the dead period eliminating means and the disconnection detection means is connected via the disconnection detection resistance lead portions 113 and 123 and the disconnection detection resistance electrode portions 114 and 124. Yes.
Furthermore, in order to ensure electrical insulation between the PM deposited so as to short-circuit between the lead portions 112 and 121 by bypassing the breakage detection resistor 13, and the breakage detection resistor 13 and the lead portions 113, 114, 123, and 124. The insulating heat-resistant protective layer 150 is formed using an electrically insulating heat-resistant material so as to cover the surfaces of the disconnection detecting resistor 13 and the lead portions 113, 114, 123, and 124.
The heating unit 14 includes a heater 141 that generates heat when energized, a pair of heater leads 142a and 142b that connect the heater 141 and the energization control device 61, heater terminal portions 144a and 144b, an electrically insulating heat resistant substrate 140, Through-hole electrodes 143a and 143b that pass through the insulating heat-resistant substrate 140 and connect the heater lead portions 142a and 142b and the heater terminal portions 144a and 144b, the conductive wires 145a and 145b, and the detection unit 11, in particular, electric wire detection The insulating heat-resistant protective layer 150 that protects the resistor 13 is used.
The electrically insulating heat resistant substrates 100 and 140 are formed in a flat plate shape by using an electrically insulating heat resistant material such as alumina by a known method such as a doctor blade method, a press molding method, CIP, or HIP.
Detection electrodes 110 and 120, lead portions 111 and 121, terminal portions 112 and 122, disconnection detection resistance lead portions 113 and 123, disconnection detection resistance terminal portions 114 and 124, heater 141, heater lead portions 142a and 142b, heater terminal portion 144a 144b is formed on the electrically insulating heat-resistant substrates 100 and 140 by a known method such as thick film printing, plating, or vapor deposition.
As the disconnection detection resistor 13, a resistor made of a single substance or a complex containing at least one of metal, metal oxide, metal compound, carbon, and carbon compound is used.
In the present embodiment, an example is shown in which a resistor having a thick film formed on the surface of the electrically insulating heat-resistant substrate 100 is used.
In the present embodiment, the disconnection detection resistor 13 is formed at a position where it can be heated by the heating unit 14 to stabilize the offset resistor R _OFFSET .
The detection resistance R _SEN formed by PM deposited on the detection unit 11 is several hundred Ω to 1 kΩ during PM deposition, and changes to 1 MΩ or more during PM combustion.
Further, in the present embodiment, the offset resistance _{R OFFSET} disconnection detection resistor 13, 16Keiomega～36keiomega, dividing resistors _{R 1} of the output voltage detection unit 60 is set to 4Keiomega～24keiomega, the power supply voltage _{V CC,} 5. It is set to 0v.

When the maximum amount of PM is accumulated in the detection unit 11, the detection resistance R _SEN is much smaller than the offset resistance R _OFFSET , so that the output voltage _VOUT is determined by the detection resistance R _SEN and the voltage _dividing resistance R _1. The range is 0.0 v to 4.8 v, and the dynamic range is effectively used, and the range can be stably detected even when the output variation is taken into consideration.
Output variations dividing resistors R ₁ and be at least 24kΩ increases and the voltage dividing resistors R ₁ below 4kΩ reduces the dynamic range, the detection accuracy is deteriorated.
Further, in a state where PM deposited on the detection unit 11 is burned and removed, the detection resistance R _SEN is much larger than the offset resistance R _OFFSET , so that the output voltage _VOUT is equal to the offset resistance R _OFFSET and the voltage _dividing resistance R _1. And is determined to be 0.5v to 1.0v.
If the offset resistance R _OFFSET is set to 36 kΩ or more, the dynamic range is lowered and the detection accuracy is deteriorated. If the offset resistance R _{OFFSET is set} to 16 kΩ or less, the offset value becomes small, and it is difficult to discriminate between a normal time and a disconnection. .

With reference to FIG. 2, a modified example 10a of the particle detecting element in the first embodiment of the present invention will be described.
In the above embodiment, the disconnection detection resistor 13 is provided at a position where it can be heated by the heating unit 14 to stabilize the offset resistance R _OFFSET . However, in this embodiment, the counter output of the lead units 111 and 121 is achieved. The disconnection detection resistance lead portions 113a and 123a drawn from the side are extended to the output side of the electrically insulating substrate 100, and are not subjected to the heat of the gas to be measured or the heat from the heating portion 14, and in a thermally stable position, The disconnection detection resistor terminal portions 114a and 124a are provided, and the disconnection detection resistor 13a composed of a fixed resistor such as a chip resistor is mounted to stabilize the offset resistance R _OFFSET .
In the present embodiment, a thermistor having a temperature sensitive characteristic may be used as the disconnection detection resistor 13a, and may be provided at a position that can be heated by the heating unit 14 on the detection unit side.
By adopting such a configuration, in addition to the same effects as those of the above embodiment, the temperature of the detection unit 11 can be detected, and the temperature management of the detection unit 11 and the temperature control of the heating unit 14 at the time of particle detection can be performed. A more accurate gas sensor can be realized with higher accuracy.

With reference to FIG. 3, a more specific configuration of the gas sensor 1 using the fine particle detection element 10a according to the first embodiment of the present invention will be described.
The gas sensor 1 is fixed to a substantially cylindrical insulator 21 that inserts and holds the particulate detection element 10 inside, and a flow path wall 40 through which the gas to be measured flows. The gas sensor 1 holds the insulator 21 and also detects the detection unit 11 of the particulate detection element 10. At a predetermined position in the measured channel 400, a cover body 30 provided at the distal end side of the housing 20 for protecting the detection unit 11 of the particulate detection element 10, and a proximal end side of the housing 20. A detection electrode 110 that is provided and connected to the terminal portions 112 and 122 of the particulate detection element 10 via the connection fittings 115, 116, 125, and 126, and changes according to the amount of PM collected and deposited on the detection unit 11; A pair of signal lines 117 and 127 that transmit the detection electric resistance R _SEN between 120 to the external resistance measuring means 60, and a heat sensor built in the fine particle detection element 10. A substantially cylindrical casing 22 that fixes a pair of conducting wires 147a and 147b connected to each other via a sealing member 220 on the base end side via a sealing member 220, the heater terminal portions 145a and 145b, and the connection fittings 146a and 146b. And is composed of.
The cover base 300 of the cover body 30 is appropriately provided with measured gas inlet / outlet holes 301 and 302 for introducing a measured gas containing PM into the detection unit 11, and a flange portion 303 provided on the proximal end side is a housing. It is fixed by caulking by a caulking portion 203 provided on the front end side of 20.
In the present embodiment, the disconnection detection resistor 13a is disposed at a relatively stable temperature in the insulator 21.
Diesel combustion exhaust gas containing PM as the measurement gas flows through the measurement gas flow path 400 and is introduced from the measurement gas inlet / outlet holes 301 and 302 provided in the cover body 30, and the detection unit 11 is included in the measurement gas. , The PM is deposited between the detection electrodes 110 and 120, and the detection resistor R _SEN is formed between the detection electrodes 110 and 120, so that the outside of the gas sensor 1 is exposed. The combined resistance of the detection resistor R _SEN and the offset resistor R _OFFSET can be detected by the resistance measuring means 60 provided in the above, and the amount of PM deposited can be calculated.

  With reference to FIG. 4, another modified example of the fine particle detection element 10b in the first embodiment of the present invention will be described. In the above-described embodiment, the breakage detection resistor lead portion 113 formed by forming the end portions of the lead portions 111 and 121 on the side of the anti-resistance measuring means and the breakage detection resistor 13 on the electrically insulating substrate 100 by a method such as thick film printing, In the fine particle detection element 10b according to the present embodiment, a fixed resistor with leads disposed on the output side of the electrically insulating substrate 100 is used as the disconnection wire detection resistor 13b. The lead portions 111 and 121 are connected to the end portions on the anti-resistance measuring means side via the wires 113b and 123b. By adopting such a configuration, the internal resistance of the disconnection detection resistance lead portions 113b and 123b can be reduced as compared with the case where the disconnection detection resistance lead portions 113b and 123b are formed. Durability can also be improved.

With reference to FIG. 5, another modified example will be described as the fine particle detection element 10c in the first embodiment of the present invention.
As shown in FIG. 5, a fixed resistor with leads is used as the disconnection detection resistor 13 c, and the disconnection detection resistor leads 113 c and 123 c are bent, and the disconnection detection resistor 13 c is connected to the heating unit 14 on the back side of the detection unit 11. You may make it touch.
With this configuration, the disconnection detection resistor 13c can be heated by the heater 141 and is thermally stabilized, and disposed on the back surface side of the detection unit 11, so that the disconnection detection resistor lead portions 113c and 123c are electrically connected. Since the insulating substrate 100 is three-dimensionally separated, it is difficult to form a conductive path due to PM deposition. The influence on the disconnection detection resistor 13c can be eliminated.

With reference to FIG. 6, another modified example of the fine particle detection element 10d in the first embodiment of the present invention will be described.
In the above embodiment, the example in which the disconnection detection resistor 13 is formed on the surface of the electrically insulating substrate 10 has been shown. However, as in the present embodiment, the electrically insulating substrate 100d is disposed between the detecting unit 11 and the heating unit 14. Are formed on the surface thereof, and through-hole electrodes 118 penetrating through the ends of the lead portions 111 and 121 on the side opposite to the detection side and the electrically insulating substrate 100d, You may connect via 128.
Although the example in which the disconnection detection resistor 13d is provided in the non-heatable region has been described in the present embodiment, the disconnection detection resistor 13d may be provided in a position that can be heated by the heater 140.

With reference to FIG. 7, the outline of the gas sensor 1e using the fine particle detection element 10e in the second embodiment of the present invention will be described.
In the above-described embodiment, the plurality of detection electrodes 110 and 120 are drawn out so that the pair of detection electrodes 110 and 120 constituting the detection unit 11 extend linearly from the lead portions 111 and 121, respectively, and these are opposed to each other. Although an example in which the electrodes are formed in a comb-teeth shape is shown, in the present embodiment, a part of the pair of detection electrodes 110e and 120e connected to the lead portions 111 and 121 is bent in a crank shape to provide a predetermined gap. These end portions on the opposite resistance measuring portion side are connected to the disconnection detection resistor 13 via the disconnection detection resistor lead portions 113e and 123e.
With this configuration, as shown in FIG. 7B, the detection resistor R _SEN formed in the detection unit 11e by PM deposition and the offset resistor R _OFFSET of the disconnection detection resistor 13 are connected in parallel. As a result, the combined resistance decreases, and the current flowing through the particulate detection element 10 when the output voltage _VOUT that drops due to the combined resistance from the power supply voltage _VCC is detected by the voltage dividing resistor R ₁ provided as the resistance measuring means 60. the pulled over the detection limit of the voltage dividing resistors R _1, it is possible to eliminate the dead time.

In addition, as shown in FIG. 7C, energization paths (111, 112, 113e, 114 to 117, 121, 122, 123e, which connect the detection unit 11 and the resistance measurement means 60 including the detection electrodes 110e and 120e, 124 to 127) are all connected in series via the disconnection detection resistor 13, so that the detection electrodes 110e and 120e and the energization paths (111, 112, 113e, 114 to 117, 121, 122, 123e, 124 to 127), when a disconnection occurs in any of the locations of the detection unit 11 as well as the conduction path, the output immediately after the PM deposited on the detection unit 11 is removed by combustion. Since the voltage _VOUT is 0, it is possible to detect a disconnection with certainty, and it is possible to take measures to eliminate the abnormality by promptly warning the abnormality. .
In the first embodiment, the detection of the disconnection of the detection electrodes 110 and 120 itself could not be detected even though it was possible to detect the presence or absence of the disconnection in the conduction path. However, in this embodiment, the detection electrodes 110e and 120e themselves were not detected. Disconnection can also be detected.
In the present embodiment, the voltage _dividing resistor R ₁ is provided between the detection resistor R _SEN and the ground. However, the voltage _dividing resistor R ₁ may be provided between the power supply voltage _VCC and the detection resistor R _SEN. good.

With reference to FIG. 8, a modified example will be described as the fine particle detection elements 10f and 10g in the second embodiment of the present invention.
Also in the present embodiment, as in the above embodiment, the mounting positions of the disconnection detection resistors 13f and 13g are mounted on the electrically opposite output side of the detectors 11f and 11g via the disconnection detection resistor lead portions 113 and 123. If there is, the mounting position of the disconnection detection resistor 13 can be changed as appropriate.

With reference to FIG. 9, the modification of the detection part 11 in the 2nd Embodiment of this invention is demonstrated. In the above embodiment, an example that is configured to detect a disconnection detection resistor _{R OFFSET} and the detection resistor _{R SEN} output voltage _{V OUT} combined resistance _{R SUM} and by dividing resistors _{R 1} by applying a power supply voltage _{V CC} min As described above, a constant current power supply 60h may be provided and the operational amplifier 601 may detect the output voltage _VOUT as shown in FIG. 11A, or as shown in FIG. The output voltage _VOUT may be detected using the constant voltage power supply 80 and the operational amplifier 601i.
Note that these embodiments can also be adopted as appropriate in the first embodiment of the present invention.

With reference to FIG. 10, the basic disconnection detection method of the gas sensor 1 of this invention is demonstrated.
This figure (a) shows the most simplified disconnection detection method, and the output voltage threshold value judging means in step S100 compares the output voltage _VOUT with a predetermined threshold value _VREF , for example, the threshold value _VREF. If a value close to 0v is set, the determination is Yes if the output voltage _VOUT is as close to 0v as possible, and it is determined that a disconnection has occurred, a disconnection determination is made in step S110, and the output voltage _VOUT is a predetermined value. If it is equal to or greater than the threshold value V _REF , it is not determined that there is a disconnection, and it can be determined that it is normal. Therefore, the determination is No and the normal determination can be made temporarily, but in order to make a more accurate determination Then, the process proceeds to a normality determination unit in step S200 described later.
According to the present embodiment, if disconnection does not occur, conduction is ensured by at least the disconnection detection resistor 13, so that the output voltage _VOUT is always generated, and the output voltage _VOUT is set to a predetermined value in consideration of an error. If it is smaller than the threshold value V _REF , it can be determined that the wire is surely disconnected.

In the present embodiment, it is determined that the output voltage _VOUT is equal to or lower than the predetermined threshold V _REF as a disconnection. However, the output voltage _VOUT may be determined to be higher than the predetermined threshold V _REF as a disconnection. Whether the output voltage _VOUT is determined to be a disconnection when the output voltage _VOUT is equal to or higher than the upper threshold V _REF or whether the output voltage _VOUT is equal to or lower than the predetermined threshold V _REF is determined as a disconnection is provided on the high side relative to the detection resistor R _SEN whether low side to provide either a or a non-inverting output and inverting output an output voltage V _OUT, the voltage dividing resistors R ₁ to form a threshold value V _REF to the detection resistor R _SEN, on whether low side providing the high side It can be appropriately changed depending on whether it is provided.

This figure (b) is a flowchart which shows the determination method for determining the presence or absence of a reliable disconnection.
In the PM combustion process in step S200, the heater unit 14 is energized to burn the PM accumulated in the detection unit 11, and the PM is burned and removed.
In the PM combustion completion determination means in step S210, it is determined whether or not PM combustion is completed. Specifically, whether the PM combustion is completed by measuring the combustion time from the start of the PM combustion stroke, judging by detecting the presence or absence of the output of the detection resistor R _SEN , or combining these both It can be determined whether or not.
If it is determined in step S210 that the combustion is not completed, the determination is No, the process returns to the PM combustion process in step S200, and the process is repeated until PM is completely combusted.
When the PM deposited on the detection unit 11 is completely combusted, the combustion completion determination unit in Step S210 makes a determination Yes, and the process proceeds to the threshold determination unit in Step S220.
In the threshold value determination means in step S220, it is determined whether or not the output voltage _VOUT is smaller than a predetermined threshold value. If a disconnection has occurred, the output voltage _VOUT is 0 or a value close to 0 as much as possible. It becomes determination Yes and a disconnection determination is carried out.
In a state in which PM in the detection unit 11 is not completely deposited, the output voltage _{V OUT} is a predetermined threshold value _{V REF} (e.g., the offset voltage _{V OFFSET} which is divided by the breakage detecting resistor _{R OFFSET} dividing resistors _{R 1)} If it is above, it will become determination No and will progress to the normal determination of step S230.

Another specific example of the disconnection detection method of the gas sensor 1 of the present invention will be described with reference to FIG. In the disconnection detecting means provided in the electronic control unit 70, the disconnection determination of the gas sensor 1 is started according to the flowchart shown in FIG. The disconnection detection method is not only a disconnection detection means but also a gas sensor regeneration means.
In the first output determination means in step S300, the presence or absence of the output voltage _VOUT of the particulate detection element 10 is determined. If the output voltage _VOUT is greater than 0 v, the determination is Yes, and the process proceeds to step S310, where the output voltage _VOUT is If it is 0v, that is, if there is no output, the determination is no and the process proceeds to the disconnection determination means in step S370.
In the second output determination means in step S310, it is determined whether or not the output voltage _VOUT is greater than a predetermined first threshold value _Vref1 . When the output voltage _VOUT is equal to or lower than the first threshold value V _ref1 , the amount of PM deposited on the detection unit 11 of the particulate detection element 10 is not saturated, and the amount of PM can be detected. It becomes determination No. Steps S300 and S310 are repeated until the PM deposition amount is equal to or greater than a predetermined amount, and the detection voltage _VOUT is equal to or greater than the first threshold value _Vref1 and the determination is Yes.
When the PM accumulation amount approaches the saturation amount and the determination is YES in step S310, the process proceeds to the particulate combustion process in step S320.
In the particulate combustion process in step S320, since the amount of PM deposited on the detection unit 11 is equal to or greater than a predetermined amount, energization of the heater 140 is started and the PM deposited on the detection unit 11 is burned and removed.
When the particulate combustion stroke is started, the output voltage _VOUT is monitored, and in the particulate combustion completion determination means in step 130, whether or not PM combustion has been completed is determined between the output voltage _VOUT and the second threshold value _Vref2 . Determined by comparison.
Due to the combustion of PM, the detection resistance R _SEN between the detection electrodes 110 and 120 is increased, and determination No is made until the output voltage _VOUT becomes equal to or lower than the second threshold value V _ref2 , and steps S320 and S330 are repeated. Energization of the heater 140 is maintained for combustion.
In step S330, when the output voltage _VOUT becomes equal to or lower than the second threshold value _Vref2 and the determination becomes Yes, the particulate combustion confirmation timer t in step S340 starts.
Next, the particulate combustion confirmation determining means in step S350 determines whether or not the particulate combustion confirmation timer t has passed a predetermined threshold value t _ref .
Until the particulate combustion confirmation timer t elapses the threshold value t _ref , even if the output voltage V _OUT becomes equal to or lower than the predetermined threshold value V _{ref2, the} PM is reliably burned, so that the energization of the heater 140 is maintained.
When the predetermined time has elapsed and the determination is YES in step S350, the process proceeds to the particulate combustion stop process in step 160, and energization of the heater 140 for PM combustion is stopped.
Next, the disconnection determination means in step S370 performs disconnection determination depending on whether or not the output voltage _VOUT is 0v.
If the output voltage _VOUT is 0v in step S370 despite the fact that PM has been reliably burned in steps S340 to S360, it is certain that the wire is disconnected, and therefore the determination is Yes. In step S380, disconnection determination is performed.
If PM is reliably combusted from step S340 to step S360, and if the output voltage _VOUT is not 0v in step S370, it is certain that the output is normal, so determination No is made, and step S390 Make a normal judgment.
If the output voltage V _OUT is 0v in step S300, it is disconnected, and in step S370, the output voltage V _OUT is also 0v, the determination is Yes, and the disconnection determination in step S380 is performed.
In step S180 and step S390, the determination result of the presence or absence of disconnection is transmitted to the outside by a diagnostic output or the like, and the disconnection determination is terminated.
When the output voltage _VOUT remains at 0v due to PM accumulation, it is a disconnection in the conduction path other than the detection unit 11, and the output voltage _VOUT changes due to PM accumulation, and the output after combustion of PM When the voltage _VOUT is 0, it can be determined that the detection unit 11 is disconnected. Therefore, in the disconnection determination in step 180, the detection unit 11 is disconnected or a disconnection in the energization path other than the detection unit 11 is performed. It is also possible to determine whether there is a separate diagnosis output.

With reference to FIG. 12, the effect of this invention in the normal time of the gas sensor 1 using the microparticle detection element 10 of this invention is demonstrated with a comparative example.
The output change of the gas sensor using the fine particle detection element not provided with the disconnection detection resistor 13 of the present invention is shown as a comparative example.
In the comparative example, at the time when PM begins to deposit between the pair of detection electrodes, the output voltage _VOUT is almost 0 V and cannot be detected because it has an extremely high resistance value of about 1 MΩ to 10 MΩ. There is a period td.
For this reason, even if a disconnection abnormality has occurred in the gas sensor 1 during the dead period td, it cannot be determined whether or not it is abnormal, and there is a possibility that abnormalities such as PM outflow due to failure of the exhaust purification device cannot be prevented.
On the other hand, in the gas sensor 1 using the particulate detection element 10 having the disconnection detection resistor 13 of the present invention, the disconnection detection resistor 13 is detected between the output electrodes 110 and 120 formed by PM deposited on the detection unit 11. _{When the SEN} is formed, the offset resistance R _OFSET of the disconnection detection resistor 13 is in parallel with the detection resistor R _SEN , so that the combined resistance is lowered and the output voltage _VOUT can be detected even in the early _stage of PM deposition. Become.
When the amount of accumulated PM is small, the detection resistor R _SEN formed between the detection electrodes 110 and 120 is large, and the output voltage _VOUT is determined by the offset resistor R _OFFSET and the voltage _dividing resistor R1, and is almost equal to the offset voltage V _OFFSET . Will be equal.
Moreover, PM deposition proceeds and the output voltage _{V OUT} becomes the first threshold value _{V ref1} or more, according to the above disconnection determination means, combustion of the PM is started, the output voltage _{V OUT} is in the vicinity of the offset voltage _{V OFFSET} In the state where PM combustion is maintained for a predetermined time t _ref after the threshold value V _{REF2 of} 2 or less and PM is reliably removed, the presence or absence of disconnection is determined, and the output voltage _VOUT after PM combustion stop is 0 v or more. If the offset voltage is V _OFFSET , normality is determined, PM is deposited as it is, and combustion of PM is started again when the output voltage _VOUT becomes equal to or higher than the first threshold value.

With reference to FIG. 13, the effect when a disconnection abnormality occurs will be described.
As shown in FIG. 13A, when the output voltage _VOUT is normal, the output voltage _VOUT rises due to the accumulation of PM, and does not become lower than the offset voltage V _OFFSET by PM combustion. When a disconnection occurs in the energization path other than the detection unit 11 while PM is being deposited on 11, the output voltage _VOUT continues to be 0 regardless of the presence or absence of PM combustion, so that it is easy. It turns out that the disconnection has arisen.
Such disconnection can be detected by using any one of the fine particle detection elements 10, 10a, 10b, 10c, and 10d in the first embodiment of the present invention and the fine particle detection elements 10e, 10f, and 10g in the second embodiment. Can do.
As shown in FIG. 13B, when the disconnection occurs in the detection unit 11e, the output voltage _VOUT is disconnected when the PM is deposited in the disconnection portion to form a conductive path. Even in this state, the presence or absence of disconnection is not detected, and the gas sensor 1 functions as if it is normal.
When PM accumulation progresses and the output voltage _VOUT becomes equal to or higher than the first threshold value V _ref1 , PM combustion starts, and when PM deposited on the disconnected portion is removed, PM remains other than the disconnected portion of the detection unit 11. However, the resistance value suddenly increases, and the output voltage V _OUT becomes equal to or lower than the second threshold value V _ref2 . However, in the present invention, even if the output voltage _VOUT becomes the second threshold value, the combustion of PM is not stopped immediately, but the combustion of PM is maintained for a predetermined time t _ref and completely detected by the detection unit 11. After removing the deposited PM, disconnection determination is performed.
For this reason, when the disconnection has occurred in the detection unit 11, it is understood that the disconnection has occurred in the detection unit 11 because the output voltage _VOUT is 0 after the PM combustion confirmation, and the disconnection determination is surely performed. can do.
In addition, when the disconnection has occurred in the detection unit 11, if the gas sensor 1 is operated as it is, PM accumulates in the disconnection part, and the disconnection part is bypassed to operate normally. However, after PM combustion, The voltage _VOUT becomes 0, indicating that the disconnection is abnormal.

The present invention is not limited to the above-described embodiment, and can be appropriately changed without departing from the gist of the present invention.
For example, in the above embodiment, the particulate matter detection sensor mounted on an internal combustion engine such as an automobile engine has been described as an example, but the particulate matter detection sensor of the present invention is not limited to being mounted on a vehicle, It can also be used for particulate matter detection in large-scale plants such as thermal power plants.

DESCRIPTION OF SYMBOLS 1 Gas sensor 10 Particulate detection element 11 Detection part 110,120 Detection electrode 111,121 Lead part 112,122 Terminal part 113,123 Disconnection detection resistance lead part 114,124 Disconnection detection resistance terminal part 115,116,125,126 Connection metal fitting 117 127 Signal lines 100, 140 Electrical insulating heat-resistant substrate 13 Disconnection detection resistor 141 Heater 142a, 142b Heater lead part 143a, 143b Through-hole electrode 144a, 144b Heater terminal part 145a, 145b, 146a, 146b Connecting bracket 147a, 147b 20 Housing 21 Insulator 22 Casing 220 Sealing member 30 Cover body 301, 302 Measured gas inlet / outlet hole 40 Measured gas channel wall 400 Measured gas channel 60 Resistance measuring unit 61 Heating control unit 70 Electronic control unit

JP 59-197847 A International Publication No. 2008/138661 European Patent Application No. 1925926

Claims (7)

A fine particle detection element having at least a detection unit that is exposed to a gas to be measured and has a pair of detection electrodes facing each other with a predetermined gap provided on the surface of the electrically insulating heat-resistant substrate, and a heating unit that heats the detection unit; And a resistance measuring means for measuring the electrical resistance between the detection electrodes, which varies depending on the amount of the conductive fine particles detected by the fine particle detection element, to detect the concentration of the conductive fine particles in the gas to be measured. In the gas sensor
As a disconnection detection means for detecting the presence or absence of disconnection of a conduction path connecting the detection unit and the resistance measurement means, the disconnection detection resistor having a predetermined resistance value is electrically connected to the pair of detection electrodes, and the detection electrode A gas sensor, which is provided on the side of the anti-resistance measuring means so as to be in parallel with a detection resistor formed therebetween.   The gas sensor according to claim 1, wherein the pair of detection electrodes are formed in a comb-teeth shape in which a plurality of electrodes protrude and face each other.   The gas sensor according to claim 1, wherein a part of the pair of detection electrodes is bent in a crank shape so as to face each other.   The gas sensor according to any one of 1 to 3, wherein the disconnection detection resistor is placed at a thermally stable position.   The gas sensor according to any one of claims 1 to 3, wherein a thermistor having a temperature-sensitive characteristic is used as the disconnection detection resistor, and provided on the detection unit side. A fine particle detection element having at least a detection unit that is exposed to a gas to be measured and has a pair of detection electrodes facing each other with a predetermined gap provided on the surface of the electrically insulating heat-resistant substrate, and a heating unit that heats the detection unit; And a resistance measuring means for measuring the electrical resistance between the detection electrodes, which varies depending on the amount of the conductive fine particles detected by the fine particle detection element, to detect the concentration of the conductive fine particles in the gas to be measured. A disconnection detection method for a gas sensor,
As the disconnection detecting means for detecting the presence or absence of disconnection of the conduction path connecting the detection section and the resistance measuring means, the gas sensor conducts the pair of detection electrodes and detects formed between the detection electrodes. Provided with a disconnection detection resistor having a predetermined resistance value provided in parallel with the resistor,
At least disconnection determination means for detecting the presence or absence of disconnection by comparing an output voltage detected by a combined resistance of the detection resistor and the disconnection detection resistor with a predetermined threshold value, and the output voltage exceeds the predetermined threshold value. A disconnection detection method for a gas sensor, characterized in that it is determined that a disconnection occurs.   Particulate combustion completion determination for determining the completion of combustion of particulates using one or both of a combustion process for burning and removing particulates accumulated on the detection part by the operation of the heating part and the output of the combustion time and particulate detection element 7. A disconnection determining means for determining the presence or absence of disconnection based on the presence or absence of an output of the particulate detection element after confirming combustion of the particulates, and determining whether or not there is a disconnection with the particulates completely removed. Method for detecting disconnection of gas sensor.

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