METHOD AND SYSTEM FOR DETECTING EXHAUST PARTICLES

Abstract

Procedure that includes the following: Adjusting a motor operation in response to a distribution of particles on multiple electrode pairs arranged in a common particle (particulate matter, PM) sensor housing of a PM sensor; and distinguishing the size of the particle distribution based on a resistance measured independently at each of the multiple electrode pairs; and further comprising: generating a current distribution across the multiple electrode pairs based on the measured resistance at each of the multiple electrode pairs, wherein the multiple electrode pairs are each electrically isolated from one another and further connected to independent voltage sources and independent measuring devices.

Description

Technical area

[0001] This description generally relates to the design and use of resistive sensors for particles (Particle Matter, PM) in an exhaust gas stream. General state of the art / Summary of the invention

[0002] Diesel engine emissions are regulated by regulations. Diesel particulate matter (PM) is the particulate component of diesel exhaust, which includes diesel soot and aerosols such as ash particles, metal wear particles, sulfates, and silicates. When released into the atmosphere, PM can take the form of individual particles or chain aggregates, typically in the invisible submicrometer range of 100 nanometers. Various technologies have been developed to detect and filter out exhaust PM before the exhaust is released into the atmosphere.

[0003] For example, PM sensors, also known as soot sensors, can be used in vehicles with an internal combustion engine. A PM sensor can be placed upstream and / or downstream of a diesel particulate filter (DPF) and can be used to detect the filter's PM load and diagnose DPF operation. Typically, the PM sensor can detect particulate or soot load based on a correlation between a measured change in electrical conductance (or current or resistance) between a pair of electrodes arranged on a planar substrate surface of the sensor and the amount of PM deposited between the sensing electrodes. More specifically, the measured conductance provides a measure of soot accumulation. As such, the sensitivity of the PM sensor can be affected by the size of particles accumulated on the sensing electrodes.For example, if a large particle becomes deposited between the measuring electrodes, a PM sensor current can quickly become saturated, reducing the sensitivity of the PM sensor to detect subsequently deposited particles.

[0004] In addition, large particles deposited on the electrodes can lead to inaccurate DPF wear readings and unwarranted replacement of properly functioning filters. Furthermore, the distribution of particles on the PM sensor electrodes can also affect the current measured by the sensor, leading to errors in the PM sensor's output signal. This can cause the PM sensor, which detects PMs leaving the DPF, to inaccurately reflect the DPF's filtering capabilities.

[0005] An exemplary PM sensor design is shown by Roth et al. in US Pat. No. 8,823,401 B2. A pair of planar, side-by-side, interdigitated electrodes connected to a common voltage source are used to independently detect PMs in the exhaust gas. As the PMs deposit on the interdigitated electrode pair due to the electrostatic attraction between the charged PMs and the electrodes, the output signals from the two independent PM sensors are further analyzed and compared using extensive algorithms to obtain meaningful information to distinguish larger particles in the exhaust.

[0006] However, the present authors have identified potential problems with such an approach. The PM sensors described in Roth et al. may still experience problems with large particles that saturate the PM sensor current and thereby impair the sensitivity of the PM sensor. Furthermore, the sensor output signal from Roth et al. requires analysis with extensive algorithms to obtain meaningful information regarding the PMs in the exhaust gas, resulting in longer processing times and undesirable delays in data output and diagnostics.

[0007] DE 10 2011 017 547 A1 discloses a gas sensor capable of detecting a concentration of PM contained in exhaust gas emitted from a diesel engine. The gas sensor consists of a ceramic substrate and sensing parts formed on the ceramic substrate with resistance parts. A resistance value of each of the resistance parts is changed based on the amount of conductive particles captured by and accumulated on the sensing parts. The sensing parts have different sensing ranges. A portion of the sensing range of each of the sensing parts overlaps each other. The concentration of PM contained in the gas to be detected is detected based on the change in the resistance value of the resistance parts.

[0008] DE 10 2012 024 258 A1 discloses a sensor and a measuring arrangement for detecting the particle concentration in the exhaust stream of an internal combustion engine. The sensor has different sensor regions arranged on a support, each with differently arranged electrodes. The sensor comprises at least two identically designed sensor units, each sensor unit consisting of at least two different sensor regions whose electrodes have different electrode spacings.

[0009] A soot measurement system comprising a soot sensor with a first element and a circuit is known from WO 2015 / 073596 A1. An electrostatic repulsion voltage (ERV) can be applied to one or more sensor / heating elements during a fouling prevention mode (CPM) to repel ash and reduce sensor fouling. A pulsed heating voltage (PHV) can be applied to the elements during CPM, and a pulsed ERV can be applied to the elements during the PHV off period.

[0010] The inventors have found a way to partially solve these problems while improving the sensitivity of PM sensors. In one example, the problems described above can be solved by a method according to claim 1 and a method according to claim 6. This allows each individual electrode pair of the multiple electrode pairs to be connected to different voltage sources, and the current measured at each electrode pair can be summed to obtain the total PM sensor current. As a result, the PM accumulation at each individual electrode pair can be monitored independently, and the particle size distribution can be tabulated.

[0011] For example, large particles deposited on one of the electrode pairs can saturate the current measured at that specific electrode pair, while the remaining electrode pairs remain unaffected. The technical effect of summing the currents generated at the PM sensor's multiple electrode pairs to create a total PM sensor current is that the total PM sensor current cannot saturate and can continue to increase as PMs continue to deposit on the remaining electrode pairs. In this way, a more accurate measure of the PM load in the exhaust, and therefore the PM load of the DPF, can be determined. This improves the efficiency of filter regeneration and reduces the need for extensive algorithms. Furthermore, by enabling more accurate diagnosis of an exhaust DPF, compliance with emissions regulations can be improved.This reduces the high warranty costs of replacing faulty particulate filters; exhaust emissions are reduced, and the service life of the exhaust component is extended.

[0012] It should be understood that the above summary is intended only to introduce, in a simplified form, a selection of concepts that are discussed in more detail in the detailed description. It is not intended to point out principal or essential features of the claimed subject matter, the scope of which is clearly defined by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that overcome disadvantages identified above or in any part of this disclosure. Short description of the drawings Fig. Figure 1 shows a diagram of an internal combustion engine and an associated particulate matter (PM) sensor positioned in an exhaust stream. Fig. Figure 2A shows an enlarged view of a single electrode pair of multiple electrode pairs of the PM sensor and an associated circuit for detecting PMs accumulated in the single electrode pair. Fig. Figure 2B shows the multiple electrode pairs of the PM sensor with multiple voltage sources for detecting PMs in the exhaust stream. Fig. Figure 2C shows an example current generated at the multiple electrode pairs of the PM sensor. Fig. 3 shows a general flowchart for operating the PM sensor to discriminate particle size and regenerate the PM sensor based on a total sum of the current generated at each of the multiple electrode pairs of the PM sensor. Fig. 4 shows a flowchart of a method for performing a regeneration of the PM sensor. Fig. Figure 5 shows a flowchart of a method for diagnosing leaks in a particulate filter located upstream of the PM sensor. Fig. Figure 6 shows an exemplary relationship between the total sum of the current of PM sensor current and the soot load on the particulate filter. Detailed description

[0013] The following description concerns the detection of particles (Particulate Matter, PM) in an exhaust stream of an engine system, such as the one in Fig. 1. A single electrode pair of a PM sensor, as shown in Fig. 2A, may include a pair of interdigitated electrodes electrically coupled to a voltage source to generate a current based on the particles collected between the electrodes. Multiple pairs of electrodes of the (in Fig. 2B) PM sensor can be connected to multiple voltage sources to measure the current at each of the electrodes independently and sum them to generate a total current of the PM sensor ( Fig. 2C). A control unit may be configured to execute a control routine, such as the routine of Fig. 3, to distinguish the particle size based on the total current of the PM sensor and regenerate the PM sensor. In addition, the control unit can intermittently clean the PM sensor (as in the example shown in Fig. 4) to enable continued PM detection and to perform a diagnosis on a particulate filter upstream of the PM sensor based on a duration between particulate filter regenerations (as in the method shown in Fig. 5 presented methods). An exemplary relationship between the total current of the PM sensor and the DPF soot load is shown with reference to Fig. 6. In this way, by independently measuring the current at individual electrode pairs of the PM sensor's multiple electrode pairs and summing them to generate the PM sensor's total current, measurement fluctuations can be reduced. Overall, the PM sensor's performance in estimating DPF filtering capabilities (and thereby detecting DPF leaks) can be enhanced, and compliance with emissions standards can be improved because PMs in the exhaust gas can be detected more reliably.

[0014] Fig. 1 shows a schematic representation of a vehicle system 6. The vehicle system 6 includes an engine system 8. The engine system 8 may include an internal combustion engine 10 having a plurality of cylinders 30. The internal combustion engine 10 includes an air intake 23 and an exhaust 25. The air intake 23 includes a throttle valve 62 that is in fluid communication with the intake manifold 44 via an intake passage 42. The exhaust 25 includes an exhaust manifold 48 that ultimately discharges into an exhaust passage 35 that directs exhaust gas to the atmosphere. The throttle valve 62 may be disposed in the intake passage 42 downstream of a boost pressure enhancer, such as a turbocharger (not shown), and upstream of an intercooler (not shown). If present, the intercooler may be configured to lower the temperature of the intake air that has been compressed by the boost pressure enhancer.

[0015] The exhaust 25 may include one or more emission control devices 70, which may be mounted in a tightly coupled position within the exhaust. One or more emission control devices may include a three-way catalyst, a nitrogen oxide filter, an SCR catalyst, etc. The exhaust 25 may also include a diesel particulate filter (DPF) 102, which temporarily filters PM from the incoming gases and is positioned upstream of the emission control device 70. In one example, as shown, the DPF 102 is a diesel particulate trap system. The DPF 102 may have a monolithic structure, made of, for example, cordierite or silicon carbide, with multiple channels located within to filter particulates from the diesel exhaust.Tailpipe exhaust, from which the PMs have been filtered out after passing through the DPF 102, may be measured in a PM sensor 106, further treated in the emission control device 70, and exhausted to the atmosphere via the exhaust passage 35. In the example shown, the PM sensor 106 is a resistive sensor that estimates the filtration efficiency of the DPF 102 based on a change in conductance measured at the PM sensor electrodes. Here, the PM sensor 106 is a resistive sensor that estimates soot leakage from the DPF 102 based on a change in conductance measured at the soot sensor electrodes 106. If the soot emission from the DPF 102, as determined from the output signal of the PM sensor 106, is greater than the threshold soot emission, it may be determined that the DPF 102 is leaking and defective and needs to be replaced.If the conductance of the PM sensor reaches a threshold, the PM sensor can also be regenerated by heating the PM sensor until the soot particles are burned off. The response time for the accumulation of soot emissions, and thus the response time to reach a conductance threshold, is a measure of the DPF leak. Thus, the PM sensor can be regenerated by heating the sensor substrate via a heating element (not shown) to burn off the accumulated soot particles from the surface of the PM sensor 106. By intermittently regenerating the surface of the soot sensor 106, it can be returned to a state more suitable for capturing exhaust soot. In addition, accurate information regarding the exhaust soot levels can be obtained from the sensor regeneration and passed on to the control unit.

[0016] The vehicle system 6 may further include a control system 14. The control system 14 is shown receiving information from a plurality of sensors 16 (various examples of which are described herein) and sending control signals to a plurality of actuators 81 (various examples of which are described herein). For example, the sensors 16 may include an exhaust flow rate sensor 126 configured to measure a flow rate of exhaust gas through the exhaust passage 35, an exhaust gas sensor (located in the exhaust manifold 48), a temperature sensor 128, a pressure sensor 129 (downstream of the emissions control device 70), and a PM sensor 106. Other sensors, such as additional pressure, temperature, air-fuel ratio, exhaust flow rate, and composition sensors, may be coupled to various locations in the vehicle system 6.As another example, the actuators may include fuel injectors 66, a throttle body 62, DPF valves that control filter regeneration (not shown), an engine actuator that controls PM sensor opening (e.g., the control unit opening of a valve or plate in an inlet of the PM sensor), etc. The control system 14 may include a control unit 12. The control unit 12 may be configured with computer-readable instructions stored in non-transitory memory. The control unit 12 receives signals from the various sensors. Fig. 1, processes the signals and uses the various actuators of Fig. 1 for adjusting the engine operation based on the received signals and instructions stored in a memory of the control unit. Example routines are described in this text with reference to the Fig. 3-5 described.

[0017] We return to Fig. 1. The PM sensor 106 of Fig. 1 is disposed in the exhaust passage 35 where exhaust gases flow from downstream of the DPF 102 toward an exhaust tailpipe, as indicated by the arrows. In some examples, the PM sensor 106 may be disposed upstream of the DPF to determine the soot load of the DPF. The PM sensor 106 may include a protective tube, which may serve to protect a PM sensor element housed therein, and may additionally serve to redirect exhaust gas flow over the PM sensor element. Typically, the PM sensor element includes a pair of planar interdigitated electrodes forming a "comb" structure and connected to a single voltage source. By applying a voltage to the pair of planar interdigitated electrodes, an electric field may be generated within the gap between the electrodes, and any accumulated PM may change the resistance between the electrodes, which may then be measured as a change in current across the electrodes.By monitoring the change in current, the soot load at the PM sensor can be determined. Here, PMs or soot are deposited on interdigitated electrodes of the PM sensor element by means of the electrostatic attraction of the charged soot particles to the sensor surface by the electric field created by the pair of planar interdigitated electrodes. However, if larger particles are deposited between the electrodes, connecting multiple "combs" of the electrode, the PM sensor current can saturate. After that, additional PMs accumulating on the PM sensor electrode may no longer increase the current, thereby reducing the sensitivity of the PM sensor in detecting PMs in the exhaust gas. In some cases, a leak in the DPF may be indicated, requiring an unjustified replacement of an otherwise perfectly good DPF.

[0018] The inventors have recognized that by independently connecting individual electrode pairs of the interlocking comb structure to separate voltage sources and separate measuring devices and concomitantly monitoring the current at each of the individual electrode pairs, it may be possible to reduce the saturation of the PM sensor current due, for example, to the impact of large particles.

[0019] A single pair of electrodes is shown in the schematic view 200 of Fig. 2A. We now turn Fig. 2A, where view 200 shows a single electrode pair 202 coupled to a measuring circuit including a voltage source 218 and a measuring device 220. Here, the single electrode pair 202 may further include a positive electrode 204 and a negative electrode 206.

[0020] The positive and negative electrodes 204 and 206 can typically be made of metals such as platinum, gold, osmium, rhodium, iridium, ruthenium, aluminum, titanium, zirconium, and the like, as well as oxides, cements, alloys, and combinations containing at least one of the above-mentioned metals. The electrodes 204 and 206 are formed on a PM sensor substrate (not shown), which is typically made of highly electrically insulating materials. Electrically insulating materials can include oxides such as aluminum oxide, zirconium oxide, yttrium oxide, lanthanum oxide, silicon oxide, and combinations including at least one of the above, or any comparable materials capable of preventing electrical crosstalk and providing physical protection for the single pair of interdigitated electrodes 202.

[0021] The negative electrode 206 may include a first electrode wire or contact pad or "prong" 208 and a second electrode wire or contact pad or "prong" 210 connected at an intersection 209. Here, the first electrode wire 208 extends along a first direction (e.g., along the Y-axis) by a first distance determined by the length of the first electrode wire 208. The second electrode wire may extend along a second direction (e.g., along the X-axis) orthogonal to the first direction, and may further extend by a second distance, where the second distance is, for example, greater than the first distance. Here, the second distance may include the length of the second electrode wire 210.As seen in the schematic view 200, the first electrode wire 208 and the second electrode wire 210 of the negative electrode 206 form a "T-shaped" intersection 209. In one example, the intersection 209 may be formed midway along the length of the first electrode wire 208. As a result, at the intersection 209, the first electrical wire 208 may be electrically coupled to the second electrode wire 210 of the negative electrode 206. Together, for example, the first electrode wire 208 and the second electrode wire 210 form the negative electrode 206.

[0022] The positive electrode 204 of the single electrode pair 202 may include a single electrode wire or a contact island or "prong" consisting of multiple segments 212, 214, and 216 separated from both the first electrode wire 208 and the second electrode wire 210, creating a gap in which the charged PMs can be trapped. Here, the segments 212 and 216 may be positioned on either side of the second electrode wire 210 of the negative electrode, and further equidistant (e.g., at a distance D1) from the second electrode wire 210. For example, the distance may include a space with no components between them.

[0023] The first segment 212 of the positive electrode 204 may extend along the second direction (e.g., along the X-axis) a third distance, where the third distance is longer than both the first distance and the second distance. Furthermore, the first segment 212 of the positive electrode 204 may be connected to a second, orthogonal segment 214, and may be further connected to a third segment 216. Together, the three segments of the positive electrode 204 surround or encompass the second electrode wire 210 and are further separated and electrically insulated (or decoupled) from both the first electrode wire 208 and the second electrode wire 210. The first segment 212 is separated from the third segment 216 by a distance, for example, equal to the length of the second segment 214 (or 2D1).In some examples, segments 212, 214, and 216 may be a single, continuously electrically coupled electrode wire and together form the positive electrode 204. However, the positive electrode 204 and the negative electrode 206 may also be decoupled from each other.

[0024] As described earlier, the second negative electrode wire 210 is coupled to the first electrode wire 208 at the intersection 209. However, the second electrode wire 210 includes a non-attached end separated from each of the first positive electrode segment 212, the second positive electrode segment 214, and the third positive electrode segment 216 by a distance. The distance between the non-attached end of the second electrode wire 210 and the second positive electrode segment 214 is D2, while the distance between the non-attached end of the second electrode wire 210 and each of the first positive electrode segment 212 and the third positive electrode segment 216 is D1.

[0025] The negative electrode 206 is electrically coupled to a negative terminal of the voltage source 218 via an electrical connection 222. Furthermore, the positive electrode 204 is electrically coupled to a measuring device 220 via an electrical connection 224 and further connected to a positive terminal of the voltage source 218 via an electrical connection 226. Here, the measuring device 220 is connected between the positive electrode and the positive terminal of the voltage source 218. In some examples, the measuring device may be located between the negative electrode and the negative terminal of the voltage source 218. As a result, the electric field generated between the positive and negative electrodes may assist in trapping electrically charged soot particles therebetween, thereby forming soot bridges.

[0026] The electrical connections 222, 224 and 226, the voltage source 218 and the measuring device 220 may be part of an electrical circuit that may be located outside the exhaust duct 35 (for example, <1 meter away). Furthermore, the voltage source 218 and the measuring device of the electrical circuit may be controlled by a control unit, such as the control unit 12 of Fig. 1, so that particulates trapped at the PM sensor can be used, for example, to diagnose leaks in the DPF. The measuring device 220 may be any device capable of sensing a change in resistance across the electrodes, such as a voltmeter. In some examples, the measuring device 220 may be a current measuring device, such as an ammeter. As PM or soot particles 228 are deposited between the positive electrode 204 and the negative electrode 206, the resistance between the electrode pair may begin to decrease, indicated by an increase in the current measured by the measuring device 220.The control unit 12 may be able to determine the resistance between the single electrode pair 202 as a function of the current measured by the measuring device 220 and derive a corresponding PM or soot load at the single electrode pair 202 of the PM sensor. In this way, by connecting the single electrode pair to a voltage source, it may be possible to determine the current at the single electrode pair based on the PMs accumulated between the electrodes of the single electrode pair 202. Here, a length of the PMs deposited between the single electrode pair 202 may be determined based on the resistance (and further based on the current) measured by the measuring device 220.If the accumulated PMs become long enough and thereby extend along the gap between the positive and negative electrodes, touching the positive and negative electrodes, a soot bridge can form. When the soot bridge is formed, the current measured at the positive and negative electrodes can saturate. For example, a large particle 228 extending across the positive electrode 204 and the negative electrode 206 can saturate the current measured by the measuring device 220.

[0027] In PM sensors that include interdigitated electrodes connected to a single voltage supply, the soot bridge formed at one or more pairs of positive and negative "prongs" of the PM sensor electrodes can saturate the current measured at the PM sensor. After that, the current measured at the PM sensor electrodes may no longer detect any of the particles that continue to be deposited between the electrodes of the PM sensors. The inventors have recognized that by using multiple interdigitated electrodes and by independently connecting each of them to separate voltage sources, as in Fig. 2B, the PM sensor can be prevented from being affected by large particles deposited between the electrodes of the PM sensor, thereby still allowing PMs in the exhaust gas to be detected.

[0028] We now turn Fig. 2B, where a schematic view 230 of an exemplary embodiment of interdigitated electrodes of a particulate matter (PM) sensor (such as the PM sensor 106 of Fig. 1) and a PM detection circuit. Here, the PM sensor may include multiple (here four) interdigitated electrode pairs 202, 234, 236, and 238 electrically coupled to multiple (here four) voltage sources 218, 240, 242, and 244, as shown in Fig. 2B shown.

[0029] Thus, the details of each interdigitated electrode pair 202, 234, 236, and 238 and their corresponding positive and negative electrodes of the multiple electrode pairs of view 230 may be similar to the single electrode pair 202 and its positive and negative electrodes 204 and 206 of schematic view 200, as discussed above.

[0030] In one example, the single electrode pair 202 of Fig. 2B may be a first single electrode pair and may further be similar to the single electrode pair 202 described with reference to Fig. 2A. In addition to the single electrode pair 202, the PM sensor shown in view 230 may include a second single electrode pair 234 that is further separated from the first single electrode pair 202 by a gap. Furthermore, the second single electrode pair 234 may include a positive electrode surrounding a negative electrode that is further insulated and separated by a distance (where the positive electrode and the negative electrode of the electrode pair 234 are similar to the positive and negative electrodes 204 and 206 described, for example, with reference to Fig. 2A). Furthermore, the positive electrode may be connected to a positive terminal of the second voltage source 240 via a connecting wire 260. Similarly, the negative electrode of the second single electrode pair 234 may be connected to a measuring device 246 via a connecting wire 261 and further to a negative terminal of the voltage source 240 by a connecting wire 262. Here, the voltage source 240 may be different from the voltage source 218, and further, the measuring device 246 may be different from the measuring device 220. Additionally, the second single electrode pair 234 may be separated from the single electrode pair 202 by a distance. In some examples, the measuring device 246 may be connected between the positive electrode of the single electrode pair 234 and the positive terminal of the voltage source 240.In some further examples, the negative electrodes of consecutive individual electrode pairs 202 and 234 may be diagonally opposite each other.

[0031] The PM sensor of view 230 may further include a third single electrode pair 236 and a fourth single electrode pair 238. The details of the third and fourth single electrode pairs may be similar to those of the first and second single electrode pairs discussed above. Briefly, the third single electrode pair 236 may include a positive electrode surrounding a negative electrode that is further insulated and separated by a distance (where the positive and negative electrodes of electrode pair 234 are similar to the positive and negative electrodes 204 and 206, for example, described with reference to Fig. 2A). Furthermore, the positive electrode may be connected to a third measuring device 248 via a connecting wire 263, and may be further connected to a positive terminal of a third voltage source 242 via a connecting wire 265. Similarly, the negative electrode of the third single electrode pair 236 may be connected to a negative terminal of the third voltage source 242 by a connecting wire 264. Here, the third voltage source 242 may be different from either the first voltage source 218 or the second voltage source 240, and further, the third measuring device 248 may be different from either the first measuring device 220 or the second measuring device 246.Additionally, the third single electrode pair 236 may be closer to the second single electrode pair 234 than the first single electrode pair 202, and may further be separated from the second single electrode pair 234 by a distance. In some examples, the separation between the third single electrode pair 236 and the second single electrode pair 234 may be similar to the separation between the first single electrode pair 202 and the second single electrode pair 234. In other examples, the separation between successive single electrode pairs may be different. In some examples, the measuring device 248 may be connected between the negative electrode of the single electrode pair 236 and the negative terminal of the third voltage source 248. In some further examples, the negative electrodes of successive single electrode pairs may be diagonally opposite each other.

[0032] Additionally, the fourth single electrode pair 238 may include a positive electrode surrounding a negative electrode that is further insulated and separated by a distance (wherein the positive electrode and the negative electrode of the electrode pair 234 are similar to the positive and negative electrodes 204 and 206 described, for example, with reference to Fig. 2A). Furthermore, the negative electrode of the fourth single electrode pair 238 may be connected to a fourth measuring device 250 via a connecting wire 267 and may be further connected to a negative terminal of a fourth voltage source 244 via a connecting wire 268. Similarly, the positive electrode of the fourth single electrode pair 238 may be connected to a positive terminal of the fourth voltage source 244 by a connecting wire 266. Here, the fourth voltage source 244 may be different from any of the first voltage source 218, the second voltage source 240, and the third voltage source 242, and further, the fourth measuring device 250 may be different from any of the first measuring device 220, the second measuring device 246, and the third measuring device 248.Additionally, the fourth individual electrode pair 238 may be closer to the third individual electrode pair 236 than the first individual electrode pair 202 and the second individual electrode pair 234, and may further be separated from the third individual electrode pair 236 by a distance. In some examples, the separation between the fourth individual electrode pair 238 and the third individual electrode pair 236 may be similar to the separation between the first individual electrode pair 202 and the second individual electrode pair 234, and may further be similar to the separation between the second individual electrode pair 234 and the third individual electrode pair 236. In other examples, the separation between successive individual electrode pairs may be different.In some examples, the measuring device 250 may be connected between the positive electrode of the single electrode pair 238 and the positive terminal of the fourth voltage source 250. In some further examples, the negative electrodes of consecutive single electrode pairs may be diagonally opposite each other.

[0033] Here, the PM sensor consists of four individual electrode pairs. However, the PM sensor may include even more individual electrode pairs without departing from the scope of the disclosure. The electrical connections or connecting wires connecting the multiple individual electrode pairs to the corresponding multiple voltage sources and multiple measuring devices may be part of an electrical circuit that may be located outside the exhaust duct 35 (e.g., <1 meter away). The multiple measuring devices may be devices capable of detecting changes in resistance at the electrodes, such as voltmeters. In some examples, the measuring devices may be current measuring devices, such as ammeters. Furthermore, the multiple voltage sources (such as voltage sources 218, 240, 242, 244 of view 230 of Fig. 2B) and the plurality of measuring devices (such as the measuring devices 220, 246, 248 and 250 of view 230 of Fig. 2B) of the electrical circuit can be controlled by a control unit, such as the control unit 12 of Fig. 1, so that particles trapped at the PM sensor can be used to diagnose leaks in the DPF, as described below with reference to Fig. 2C is explained.

[0034] Thus, an exemplary specific particulate matter (PM) sensor system may include a PM sensor including a plurality of planar interdigitated electrode pairs and a plurality of voltage sources, wherein each individual planar interdigitated electrode pair of the plurality of interdigitated electrode pairs includes a positive electrode and a negative electrode, wherein the positive electrode is electrically coupled to a positive terminal of a voltage source via a sensing device, wherein the negative electrode is electrically coupled to a negative terminal of the voltage source, and wherein the individual electrode pairs are isolated from each other by an insulating gap.Here, the negative electrode of each of the planar interdigitated electrode pairs may include a first electrode wire extending a first distance along a first direction and a second electrode wire extending a second distance along a second direction, the first direction being orthogonal to the second direction and the second distance being greater than the first distance. Furthermore, the first electrode wire of the negative electrode may be electrically coupled to the second electrical wire, thereby creating an intersection between the first electrode wire and the second electrode wire, and may be further electrically coupled to the negative terminal of the voltage source.Furthermore, the positive electrode of each of the planar interdigitated electrode pair comprises a positive electrode wire adjacent to both the first electrode wire and the second electrode wire, which surrounds the second electrode wire of the negative electrode, and is further insulated from both the first electrode wire and the second electrode wire of the first negative electrode, and is further connected to the positive terminal of the voltage source.

[0035] The PM sensor system may further include a control unit, wherein computer-readable instructions are stored in a non-transitory memory to accumulate PMs at each of the positive electrode and the negative electrode of the planar interdigitated electrode pair by accumulating the PMs between one or more of the first electrode wire, the second electrode wire, and the positive electrode wire, as described below with reference to Fig. 2C. Here, the PM sensor may be downstream of a particulate filter in an exhaust passage, and the control unit may include further instructions to: generate a current at each of the planar interdigitated electrode pairs, sum the current generated at each of the planar interdigitated electrode pairs, and generate a total PM sensor current ( Fig. 3), and to regenerate the PM sensor when the total current is higher than a threshold ( Fig. 4). In addition, the control unit may further include instructions to indicate a leak in the particulate filter based on a duration between regenerations of the PM sensor ( Fig. 5).

[0036] Fig. 2A-2B show example configurations with the relative position of the various components. If they are shown in direct contact or in direct coupling with each other, then such elements may be referred to as being in direct contact or directly coupled with each other, respectively, in at least one example. Similarly, elements shown adjacent or juxtaposed may be adjacent or adjacent to each other in at least one example. For example, components that are in surface-sharing contact with each other may be referred to as being in surface-sharing contact. As another example, elements positioned at a distance from each other and having only a space and no other components between them may be referred to as such in at least one example.

[0037] We now turn Fig. 2C. The curve diagram 270 shows a current generated at the multiple pairs of electrodes arranged with respect to Fig. 2B. More specifically, the graph 270 compares the total current generated in the PM sensor embodiment including multiple planar interdigitated electrode pairs connected to multiple voltage sources, with an exemplary PM sensor including an interdigitated "comb" electrode structure with a single voltage source. The total PM sensor current is shown along the vertical axis, and time is shown along the horizontal axis. Line 276 may indicate a threshold current corresponding to a regeneration of the PM sensor.

[0038] In Fig. In Figure 2C, curve 272 represents the total PM sensor current generated in an exemplary PM sensor including continuous interdigitated electrodes coupled to a single voltage source. Here, the PM sensor may include a positive electrode consisting of continuous "spikes," with all of the "spikes" coupled to a positive terminal of the single voltage source. Similarly, the PM sensor may also include a negative electrode also consisting of continuous "spikes," with all of the "spikes" coupled to a negative terminal of the single voltage source. Additionally, the PM sensor may include a single sensing device coupled between the positive electrode and the voltage source or the negative electrode and the voltage source.When PMs accumulate between the positive and negative electrodes of the PM sensor, the change in resistance can be detected by the measuring device, and a current corresponding to the change in resistance can be generated. Between t0 and t1, the PM sensor can accumulate PMs and generate a total PM sensor current, as indicated by curve 272.

[0039] At t1, a large particle may become deposited between one or more of the PM sensor's electrode pairs, creating a soot bridge across the PM sensor's electrodes, causing the total PM sensor current to saturate (curve 272). Here, the total PM sensor current measured by the single sensing device coupled to the electrodes may quickly reach the regeneration threshold (line 276). After that, PMs accumulating between the electrodes may not cause an increase in the total PM sensor current (curve 272). Therefore, with a single voltage source and a single sensing device coupled to the interdigitated PM sensor electrodes, the total PM sensor current measured by the sensing device may have a weak dependence on the size and / or length of the bridge and may not depend on the number of bridges.In this case, the DPF, which is located upstream of the PM sensor, can be falsely diagnosed as having a leak, leading to unjustified replacements of an otherwise perfectly good DPF.

[0040] The inventors have recognized that by incorporating multiple voltage sources and multiple measuring devices coupled to individual electrode pairs, as described with reference to Fig. 2B, the total PM sensor current can be generated by summing the current at individual electrode pairs. Here, curve 274 represents the total PM sensor current generated by summing the current at individual electrode pairs, as in Fig. 2B shown.

[0041] We return to Fig. 2C. The first current (I1) may be the current generated at the first single electrode pair 202 and may be measured by the first measuring device 220. As a result, when PMs accumulate between the positive electrode and the negative electrode of the single electrode pair, the current I may be generated. Similarly, the current generated at the second single electrode pair 234 and measured by the second measuring device 246 may be I2. Likewise, the current generated at the third single electrode pair 236 and measured by the third measuring device 248 may be I3; and the current generated at the fourth single electrode pair 238 and measured by the fourth measuring device 250 may be I4. Here, the Fig. 2B has four individual electrode pairs. However, the PM sensor may, for example, contain more than four individual electrode pairs. Thus, the total PM sensor current can be generated by summing the current generated at the individual electrode pairs and can be mathematically expressed as Itotal=∑i=1nIi where i can indicate the number of individual electrode pairs included in the PM sensor design. In the Fig. 2B, i is equal to four. Thus, in such an example, the total PM sensor current I total = I1+I2+I3+I4.

[0042] We return to Fig. 2C back, where curve 274 I totalof the PM sensor, as explained above. Between t0 and t1, the total PM sensor current can be represented by curve 274. At t1, a large particle can accumulate, for example, between the electrodes of the first single electrode pair (such as PM 228 at the electrode of single electrode pair 202 of Fig. 2B). In one example, PM 228 may be formed by PMs accumulating over time, creating a large soot bridge at the electrodes of the first single electrode pair. The large particle (or soot bridge) accumulating at the electrodes of the first single electrode pair may cause an increase in the total PM sensor current at time t1 (curve 274). In some examples, the current at the first single electrode I1 measured by the first measuring device 220 may saturate; however, the current at the other single electrode pairs may not saturate, which may, for example, keep the total PM sensor current below the threshold current for PM sensor regeneration (line 276).Thus, as PM 228 accumulates and grows along the Y-axis, forming a soot bridge connecting the positive and negative electrodes of the first electrode pair 202, the current I1 measured at the first sensing device may reach a first threshold, and the first threshold may be, for example, a saturation current for the first individual electrode pair. Here, the current I1 may be used to determine the size of the PM (228) and may further be used, for example, to determine the length of the PM (228). In some examples, the threshold may be based on the PM size and / or PM length, and may further be based on the resistance measured at the electrodes. As a result, the total PM sensor current may be represented by I. total ~ I1, whereby the currents measured by the remaining individual electrode pairs may be small.

[0043] Between t2 and t3, the PMs may continue to accumulate on the PM sensor, and the multiple electrodes may continue to detect the PMs, as indicated by a steady increase in the total PM sensor current (curve 274). However, at t2, large particles (such as PM 252) may be detected on individual electrode pairs 202 and 234 of Fig. 2B) are deposited on multiple electrode pairs, resulting in an increase in the total PM sensor current (curve 274). For example, PM 252 may be a large particle that extends along the Y-axis and covers multiple electrode pairs. In some examples, PM 252 may correspond to a soot bridge that forms on multiple electrodes of consecutive individual electrode pairs 202 and 234 as PMs accumulate in the exhaust gas over time. Here, the total PM sensor current I total experience an increase as shown by curve 274, and the total PM sensor current is I total ~ I 1++ I2 (I3 and I4, for example, may be small), but it still remains below the threshold current for regenerating the PM sensor (line 276). Here, the total PM sensor current may represent current summed across multiple individual electrode pairs. In other words, the current measured by the first and second measuring devices 220 and 246 may be summed by the controller to determine the total PM sensor current. The currents measured by the third and fourth measuring devices 248 and 250 may still remain small. The large particle spanning multiple electrode pairs may cause the currents measured by the corresponding measuring devices to reach a second threshold, where the second threshold may be, for example, a saturation current for the first and second individual electrode pairs. In some examples, the second threshold may be greater than the first threshold.

[0044] Similarly, between time t2 and t3, the multiple individual electrode pairs may continue to receive PMs in the exhaust gas. However, at time t3, large particles (such as PM 254) may accumulate on individual electrode pairs 202, 234, and 236 of Fig. 2B) deposit on multiple electrode pairs, resulting in an increase in the total PM sensor current (curve 274). For example, PM 254 may be a large particle that extends along the Y-axis and covers multiple electrode pairs. As explained earlier, PM 254 may correspond to a soot bridge that forms on multiple electrodes of consecutive individual electrode pairs 202, 234, and 236 as PMs accumulate in the exhaust gas over time. Here, the total PM sensor current I total experience an increase as shown by curve 274, and the total PM sensor current is I total ∼ I 1++ I2 + I3 (I4 may be small, for example), but it still remains below the threshold current for regenerating the PM sensor (line 276). Here, the total PM sensor current may represent the current measured by the first, second, and third measuring devices 220, 246, and 248, which may be summed by the controller to determine, for example, the total PM sensor current. The currents measured by the fourth measuring devices 250 may still remain small (I4 ∼ 0). The large particle spanning multiple electrode pairs may cause the currents measured by the corresponding measuring devices to reach a third threshold, where the third threshold may be, for example, a summation of saturation currents for the first, second, and third individual electrode pairs. In some examples, the third threshold may be greater than either the second threshold or the first threshold.

[0045] Between time t3 and t4, the multiple individual electrode pairs can continue to capture PMs in the exhaust gas. However, at time t4, a large particle (such as PM 256) can accumulate on all four individual electrode pairs of Fig. 2B) deposit on multiple electrode pairs, resulting in an increase in the total PM sensor current (curve 274). For example, PM 256 can be a large particle that extends along the Y-axis and covers multiple electrode pairs. Here, the total PM sensor current I total experience an increase as shown by curve 274, and the total PM sensor current is I total ∼ I 1++ I2 + I3 + I4, and the total PM sensor current may reach the PM sensor regeneration threshold (line 276). Here, the total PM sensor current may represent the current measured by the first, second, third, and fourth measuring devices 220, 246, 248, and 250, which may be summed by the controller to determine, for example, the total PM sensor current. The large particle spanning multiple electrode pairs may cause the currents measured by the corresponding measuring devices to reach a fourth threshold, where the fourth threshold may be, for example, a summation of saturation currents for the first, second, third, and fourth individual electrode pairs. In some examples, the fourth threshold may correspond to the regeneration threshold for the PM sensor.Once the total PM sensor current reaches the regeneration threshold, indicating that the exhaust PM load has reached the threshold load, the PM sensor may need to be regenerated, as shown in . Fig. 4. In short, during conditions where the exhaust PM load on the PM sensor is higher than the threshold load, the PM sensor can be regenerated by heating the sensor substrate with a heater to burn off the accumulated soot particles from the PM sensor surface. By intermittently regenerating the PM sensor surface, it can be returned to a state more suitable for capturing exhaust PM. Furthermore, accurate information regarding the exhaust PM levels can be obtained from the sensor regeneration and transmitted to the control unit.

[0046] In this way, by summing the current across multiple individual electrode pairs, the PM sensor can more accurately detect PMs in the exhaust gas without being affected by, for example, large particles deposited on the electrodes. The technical effect of summing the currents generated across the PM sensor's multiple individual electrode pairs is that the PM sensor can more accurately detect PMs exiting the DPF, allowing the DPF to be diagnosed more reliably for leaks.

[0047] Thus, an exemplary method may be performed by the control unit as described with reference to Fig. 3 to determine exhaust PM levels more accurately and reliably. The method may include accumulating particulate matter (PM) in an exhaust at each individual electrode pair of a plurality of electrode pairs located in a PM sensor, independently generating a current at each individual electrode pair in response to accumulated particulate matter, distinguishing particle size based on the current, and summing the current at the plurality of electrode pairs to generate a total PM sensor current. Here, the total current may increase proportionally to the particle size. The method may further include regenerating the PM sensor when the total PM sensor current is greater than a threshold current.The method may further include indicating a leak in a particulate filter upstream of the PM sensor when a duration between regenerations of the PM sensor is shorter than a threshold, and not indicating the leak in the particulate filter when the duration between regenerations of the PM sensor is longer than the threshold. Here, each individual electrode pair of the plurality of electrode pairs includes a positive contact pad connected to a positive terminal of a voltage source and a negative contact pad connected to a negative terminal of the voltage source, the positive contact pad surrounding the negative contact pad and further separated by a distance.

[0048] We now turn Fig. 3, where a method for operating the PM sensor to discriminate particle size and regenerate the PM sensor based on a total sum of the current generated at the individual electrode pairs of the multiple electrode pairs of the PM sensor is shown. Instructions for carrying out method 300 and the remaining methods included herein may be provided by a control unit based on instructions stored in a memory of the control unit and in conjunction with signals received from sensors of the engine system (such as those described above with reference to Fig. 1, Fig. 2A and Fig. 2B). The control unit may use engine actuators of the engine system to adjust engine operation according to the methods described below.

[0049] At 302, method 300 includes determining engine operating conditions. The determined engine operating conditions may include, for example, engine speed, engine temperature, various exhaust air-fuel ratios, various exhaust temperatures, PM loading at the PM sensor, PM loading at the DPF, loading at an exhaust nitrogen oxide trap, ambient temperature, duration (or distance) since the last regeneration of the PM sensor and DPF, etc. At 304, method 300 includes collecting soot or PMs on individual electrode pairs of multiple electrode pairs of the PM sensor. Here, the PMs exiting the DPF may be trapped at the electrodes of the PM sensor. The PM sensor may include multiple individual electrode pairs (such as in Fig. 2B). As PMs accumulate on individual electrode pairs, the current can be measured across multiple sensing devices. The current measured by the sensing device can be used, for example, to generate the size of the PM deposited on the electrodes. Larger particles can overlap across multiple electrodes, generating a larger PM sensor current that is summed, for example, across multiple sensing devices. Similarly, smaller particles can extend across fewer electrode pairs, generating a smaller PM sensor current.

[0050] Next, at 306, method 300 includes generating a distribution of particles on the plurality of electrode pairs. Generating a distribution of particles may additionally and / or optionally include determining a resistance R iat each of the individual electrode pairs of the multiple electrode pairs of the PM sensor at 308, and may further include generating a current I i at the single electrode pair of the multiple electrode pairs of the PM sensor. As explained earlier, for example, when a particle is deposited on an electrode pair, a current is measured at the measuring device coupled to the electrode pair. The particle deposited on the electrode pair can further cause a reduction in the resistance R i and thereby, for example, the size of the particle can be determined based on the resistance R i at 312.

[0051] The process then proceeds to 314 where the distribution of the current I i at the individual electrode pairs of the multiple electrode pairs of the PM sensor to generate a total current I totalof the PM sensor. Mathematically, the summation of the current at individual electrode pairs can be Itotal=∑i=1nIi where i can specify the number of individual electrode pairs included in the PM sensor design. In the Fig. 2B, i is equal to four. Thus, in such an example, the total PM sensor current I total = I1+I2+I3+I4. Further, at 316, method 300 includes determining a total length of the distribution of particles on the multiple electrode pairs of the PM sensor.

[0052] The method 300 then proceeds to 318 where it may be determined whether the total current I totalis lower than a threshold Thr. The threshold Thr may be the threshold current corresponding to the PM sensor regeneration threshold. In some examples, the threshold Thr may be based on the PM load on the PM sensor, above which the PM sensor may need to be regenerated. If the total current is lower than the threshold Thr, indicating that the PM sensor has not yet reached the regeneration threshold, method 300 proceeds to 324, where PMs may continue to be collected at individual electrode pairs of the multiple electrode pairs, and then at 328, the currents generated at the multiple individual electrode pairs of the PM sensor may continue to be summed, as previously discussed. The method then returns to 318, where the total current may be intermittently checked, for example, to determine whether the PM sensor has reached the regeneration threshold.

[0053] If the total current is greater than the threshold Thr, then the method proceeds to 320 where the PM sensor may be regenerated as described with reference to Fig. 4. Further, at 322, method 300 includes indicating a leak in the DPF upstream of the PM sensor based on a duration between PM sensor regenerations, and further includes adjusting engine operation based on the indication of the leak in the DPF, as described with reference to Fig. 5. In this way, a diagnosis of the DPF can be performed reliably and accurately by measuring and summing the current generated at several individual electrode pairs connected to several voltage sources and further connected to several measuring devices.

[0054] Thus, an example method may include adjusting engine operation in response to a distribution of particulate matter across multiple electrode pairs disposed within a common particulate matter (PM) sensor housing of a PM sensor. The method may further include distinguishing the size of the distribution of particulate matter based on a resistance measured independently at each of the multiple electrode pairs, and may further include generating a distribution of current across the multiple electrode pairs based on the resistance at each of the multiple electrode pairs.Here, the method may further include summing the distribution of current of each individual electrode pair of the plurality of electrode pairs to generate a total PM sensor current, determining an overall size of the distribution of particulate matter on the plurality of electrode pairs based on the total PM sensor current, and in response to the total current being greater than a threshold, regenerating the PM sensor. The method may further include indicating a leak in a diesel particulate filter upstream of the PM sensor based on a duration between PM sensor regenerations. In another representation of the method, the method may include determining a length of the distribution of particulate matter on the individual electrode pair based on the current at each of the individual electrode pairs of the plurality of individual electrodes.Adjusting engine operation may further be based on indicating the leak in the diesel particulate filter, and the multiple electrode pairs may each be electrically isolated from each other and may further be connected to independent voltage sources and independent measuring devices. Each individual electrode pair may include a first electrode coupled to a positive terminal of a single voltage source and a second electrode coupled to a negative terminal of the single voltage source, and wherein the first electrode surrounds the second electrode and is further electrically isolated from the first electrode.

[0055] We now turn Fig. 4, where a method 400 for regenerating the PM sensor (such as one in Fig. 1). More specifically, if the soot load at the PM sensor is greater than the threshold, or if a resistance of the PM sensor decreases to a threshold resistance when temperature corrected, the conditions for PM sensor regeneration may be considered to be met, and the PM sensor may need to be regenerated to enable continued PM detection. At 402, PM sensor regeneration may be initiated, and the PM sensor may be regenerated by heating the sensor at 404. The PM sensor may be heated by triggering a heating element thermally coupled to the sensor electrode surface, such as a heating element embedded in the sensor, until the soot load on the sensor has been sufficiently reduced by oxidation of the carbon particles between the electrodes.PM sensor regeneration is typically controlled using timers, and the timer may be set for a threshold duration at 402. Alternatively, sensor regeneration may be controlled using a temperature measurement of the sensor tip, by controlling the power supply to the heater, or both. If a timer is used for PM sensor regeneration, method 400 includes checking at 406 whether the threshold duration has elapsed. If the threshold duration has not elapsed, method 400 proceeds to 408, where PM sensor regeneration may continue. If the threshold duration has elapsed, method 400 proceeds to 410, where PM sensor regeneration may be terminated, and the circuit may be deactivated at 412. Further, for example, the sensor electrodes may be cooled to the exhaust temperature.Method 400 proceeds to 414, where the resistance between the electrodes of the PM sensor is measured. Based on the measured resistance, possibly temperature corrected, the PM or soot load of the PM sensor (i.e., the accumulated PMs or soot between the electrodes of the PM sensor) may be calculated at 416, and the method proceeds to 418. At 418, the calculated PM sensor soot load may be compared to a threshold, Lower_Thr. The Lower_Thr threshold may be a lower threshold, for example, below the regeneration threshold, indicating that the electrodes are sufficiently cleared of soot particles. In one example, the threshold may be a threshold below which regeneration may be terminated.If the soot load continues to be greater than Lower_Thr, indicating that another regeneration may be required, method 400 proceeds to 408, where the PM sensor regeneration may be repeated. However, if the PM sensor continues to undergo repeated regenerations, the controller may set fault codes to indicate that the PM sensor is worn or that the heating element in the soot sensor may be worn. If the soot load is lower than the Lower_Thr threshold, indicating that the electrode surface is clean, method 400 proceeds to 420, where the soot sensor resistance and the soot sensor regeneration history may be updated and stored in memory. For example, a PM sensor regeneration frequency and / or an average duration between sensor regenerations may be updated.At 422, various models can then be used by the control unit to calculate the percentage efficiency of the DPF's soot filtration. This allows the PM sensor to perform on-board DPF diagnostics.

[0056] The exhaust passage may include one or more PM sensors positioned upstream and / or downstream of the DPF to determine a soot load on the DPF. If the soot sensor is positioned upstream of the DPF, a soot load on the sensor may be inferred based on changes in resistance following soot deposition on the PM sensor's multiple electrodes. The soot load determined in this way may be used, for example, to update the soot load on the DPF. If the soot load on the DPF is greater than a threshold for DPF regeneration, the control unit may adjust engine operating parameters to regenerate the DPF. More specifically, in response to the fulfillment of filter regeneration conditions, a temperature of the filter (or near the filter) may be raised sufficiently to burn off stored soot.This may involve operating a heater coupled to the DPF or raising the temperature of the exhaust gases fed into the DPF (for example, by running the engine in a rich combustion mode).

[0057] We now turn Fig. 5, where an exemplary method 500 for diagnosing DPF function based on the PM sensor regeneration time is shown. At 502, the controller may calculate, via calibration, the time of regeneration for the PM sensor, t(i)_regen, i.e., the time measured from the end of the previous regeneration to the start of the current PM sensor regeneration. At 504, t(i)_regen is compared to t(i-1)_regen, i.e., the previously calibrated PM sensor regeneration time. From this, it can be inferred that the soot sensor may need to complete a regeneration cycle multiple times to diagnose the DPF. If t(i)_regen is less than half the value of the t(iI) region, then at 508, it is indicated that the DPF is leaking, and a DPF wear signal is initiated.Alternatively, or in addition to the process discussed above, the DPF may also be diagnosed using other parameters, such as exhaust gas temperature, engine speed / load, etc. The deterioration signal may be initiated, for example, by a malfunction indicator lamp or a diagnostic code. Furthermore, method 500 includes adjusting engine operation based on the indication of the leak in the DPF at 510. Adjusting engine operation may include, for example, reducing engine torque at 512. In one example, in response to detecting a leak in the DPF, engine power may be throttled. Reducing engine power may reduce the amount of emissions in the exhaust. For example, adjusting engine operation may include adjusting an actuator of a throttle valve to set a reduced amount of airflow to the engine, thereby reducing torque.

[0058] A current regeneration time of less than half the previous regeneration time may indicate that the time it takes for the circuit to reach the R_regen threshold is shorter, and thus the regeneration frequency is higher. A higher regeneration frequency in the PM sensor may indicate that the outgoing exhaust gas consists of a larger amount of particulate matter than would be the case with a normally functioning DPF. Therefore, if the change in regeneration time in the soot sensor reaches the t_regen threshold, where the current regeneration time of the PM sensor is shorter than half the previous regeneration time, a worn or leaking DPF is signaled—for example, via a display to an operator and / or via the setting of a flag stored in non-transitory memory coupled to the processor, which can be sent to a diagnostic tool coupled to the processor.If the change in regeneration time in the soot sensor does not reach the threshold t_regen, no leaking DPF is reported at 506. In this way, leaks in a particulate filter positioned upstream of the particulate sensor can be detected based on a deposition rate of the particulates on the particulate sensor element.

[0059] We now turn Fig. 6, where a map 600 shows an exemplary relationship between the total PM sensor current and the particulate filter soot load. More specifically, map 600 shows a graphical representation of the relationship between PM sensor regeneration and DPF soot load, specifically, how PM sensor regeneration may indicate DPF wear. Vertical markers t0, t1, t2, t3, t4, t5, and t6 denote significant times during operation and in the PM sensor and particulate filter system.

[0060] The first curve from the top in Fig.6 shows the PM total sensor current of the PM sensor. As previously described, when PMs deposit on individual electrode pairs of the multiple electrode pairs of the PM sensor, the current measured at the individual electrode pairs may begin to increase, and the total sum of the currents measured at the multiple individual electrode pairs can be determined as the PM total sensor current (curve 602) of the PM sensor. The PM total sensor current is at its lowest value at the very bottom of the curve graph, and its magnitude increases toward the top of the curve graph in the vertical direction. The horizontal direction represents time, and time increases from left to right in the curve graph. The horizontal marker 606 represents the threshold current for regenerating the PM sensor in the top curve.The curve 604 represents the soot load of the DPF, and the horizontal marker 608 represents the threshold soot load of the DPF in the second curve.

[0061] A PM sensor regeneration cycle is shown between t0 and t1. At time t0, the PM sensor is in a relatively clean state, as measured by a low total PM sensor current. If a control unit coupled to the PM sensor determines the total PM sensor current by summing the current at the multiple measuring devices and further determines that the current is low, it can send instructions to a regeneration circuit to stop applying heat so that a detection circuit can begin detecting the increase in PM pollution. As the PM pollution at the sensor increases, the total PM sensor current begins to increase (602). Between t0 and t1, PM continues to accumulate, and the total PM sensor current (curve 602) increases accordingly, and further, the soot load on the DPF also increases (curve 604).In some examples, the DPF soot load may be based on the PM sensor load, for example, if the PM sensor is located upstream of the DPF. For example, the controller may be able to calculate the PM distribution and further determine the amount of PM present in the PM sensor by calculating the change in current. This may, for example, saturate currents at one or more of the measuring devices based on the PM amount.

[0062] At t1, the PM sensor current (curve 602) reaches the threshold current for PM sensor regeneration (marker 606). At t1, PM sensor regeneration may be initiated, as explained earlier. Thus, between t1 and t2, the PM sensor may be regenerated, for example, by energizing the regeneration circuit. At t2, the PM sensor may be sufficiently cool and may begin to accumulate PMs. Thus, between t2 and t3 (DPF regeneration cycle), the PM sensor may continue to accumulate PMs. During the time between t2 and t3, the DPF soot load continues to increase (curve 604). However, at t3, the DPF soot load (curve 604) reaches the threshold soot load for DPF regeneration (marker 608). Between t3 and t4, the DPF can be regenerated to burn off the soot deposited in the DPF, as explained earlier.Furthermore, at t4, the PM sensor regeneration frequency can be compared with the previous PM sensor regeneration frequency. Based on the PM sensor regeneration frequency remaining similar to previous cycles, it can be determined that the DPF is not leaking. This allows the DPF to be monitored and diagnosed for leaks based on the PM sensor output signal.

[0063] Another DPF cycle is shown between t5 and t6. Here, between t5 and t6, the soot load on the DPF gradually increases (curve 604). During this time, the total PM sensor current can be monitored. Curve 602 shows the PM sensor undergoing multiple regeneration cycles, as described earlier. However, the PM sensor regeneration frequency has almost doubled (curve 602). As explained earlier, a higher regeneration frequency in the PM sensor may indicate that the outflowing exhaust gas consists of a larger amount of particulates than would be the case with a normally functioning DPF, so a leaking DPF may be reported at t6.

[0064] In this way, a more accurate measure of exhaust PM loading and thus DPF soot loading can be determined. This improves the efficiency of filter regeneration and reduces the need for extensive algorithms. By enabling more accurate diagnosis of an exhaust DPF, compliance with exhaust emission standards can also be improved. This reduces the high warranty costs of replacing faulty particulate filters; exhaust emissions are reduced, and the service life of the exhaust component is extended. Furthermore, by using multiple individual electrodes connected to multiple measuring devices and multiple voltage sources, an accurate measure of PM sensor loading can be determined. By summing the current across multiple individual electrode pairs, the PM sensor can more accurately detect PMs in the exhaust without being affected, for example, by large particles deposited on the electrodes.The technical effect of summing the currents generated at the multiple individual electrode pairs is that the PM sensor can more accurately detect PMs leaving the DPF, allowing the DPF to be more reliably diagnosed for leaks.

[0065] The systems and methods described above also provide a method for detecting particulate matter, the method including adjusting engine operation in response to a distribution of particulate matter across a plurality of electrode pairs disposed within a common particulate matter (PM) sensor housing of a PM sensor. In a first example of the method, the method may additionally or alternatively include: distinguishing the size of the distribution of particulate matter based on a resistance independently measured at each of the plurality of electrode pairs; and may further comprise: generating a distribution of current across the plurality of electrode pairs based on the resistance at each of the plurality of electrode pairs.A second example of the method optionally includes the first example, and further includes: summing the distribution of current of each individual electrode pair of the plurality of electrode pairs to generate a total PM sensor current; determining a total size of the distribution of particulates on the plurality of electrode pairs based on the total PM sensor current; and in response to the total current being greater than a threshold, regenerating the PM sensor. A third example of the method optionally includes the first and / or second example, and further includes: indicating a leak in a diesel particulate filter upstream of the PM sensor based on a duration between PM sensor regenerations.A fourth example of the method optionally includes one or more of the first to third examples, and further includes that the adjustment of the engine operation is further performed based on the indication of the leak in the diesel particulate filter. A fifth example of the method optionally includes one or more of the first to fourth examples, and further includes that the plurality of electrode pairs are each electrically isolated from one another and are further connected to independent voltage sources and independent measuring devices.A sixth example of the method optionally includes one or more of the first to fifth examples, and further includes wherein each individual electrode pair includes a first electrode coupled to a positive terminal of a single voltage source and a second electrode coupled to a negative terminal of the single voltage source, and wherein the first electrode surrounds the second electrode and is further electrically insulated from the first electrode.

[0066] The systems and methods described above also provide a method for detecting particulate matter in a particulate matter sensor system, the method comprising: accumulating particulate matter (PM) in an exhaust at each individual electrode pair of a plurality of electrode pairs located in a PM sensor; independently generating a current at each individual electrode pair in response to accumulated particulate matter; distinguishing particle size based on the current; and summing the current at multiple electrode pairs to generate a total PM sensor current. In a first example of the method, the method may additionally or alternatively include increasing the total current proportionally with particle size. A second example of the method optionally includes the first example and further includes regenerating the PM sensor when the total PM sensor current is greater than a threshold current.A third example of the method optionally includes the first and / or second examples, and further includes indicating a leak in a particulate filter upstream of the PM sensor when a duration between regenerations of the PM sensor is shorter than a threshold. A fourth example of the method optionally includes one or more of the first through third examples, and further includes not indicating the leak in the particulate filter when the duration between regenerations of the PM sensor is longer than the threshold.A fifth example of the method optionally includes one or more of the first to fourth examples, and further includes wherein each individual electrode pair of the plurality of electrode pairs includes a positive contact pad connected to a positive terminal of a voltage source and a negative contact pad connected to a negative terminal of the voltage source, wherein the positive contact pad surrounds the negative contact pad and is further separated by a distance.

[0067] The systems and methods described above also provide a particulate matter (PM) sensor system comprising a PM sensor including a plurality of planar interdigitated electrode pairs and a plurality of voltage sources, wherein each individual planar interdigitated electrode pair of the plurality of interdigitated electrode pairs includes a positive electrode and a negative electrode, the positive electrode being electrically coupled to a positive terminal of a voltage source via a sensing device, the negative electrode being electrically coupled to a negative terminal of the voltage source, each individual electrode pair being insulated from each other by an insulating gap.In a first example of the particulate sensor system, the sensor may additionally or alternatively include the negative electrode of each planar interdigitated electrode pair comprising a first electrode wire extending a first distance along a first direction, and a second electrode wire extending a second distance along a second direction, wherein the first direction is orthogonal to the second direction and the second distance is greater than the first distance. A second example of the particulate sensor system optionally includes the first example and further includes the first electrode wire of the negative electrode being electrically coupled to the second electrical wire, creating an intersection between the first electrode wire and the second electrode wire, and further electrically coupled to the negative terminal of the voltage source.A third example of the particle sensor system optionally includes the first and / or second example, and further includes that the positive electrode of each of the single planar interdigitated electrode pair comprises a positive electrode wire adjacent to both the first electrode wire and the second electrode wire, enclosing the second electrode wire of the negative electrode, and further insulated from both the first electrode wire and the second electrode wire of the first negative electrode, and further connected to the positive terminal of the voltage source.A fourth example of the particle sensor system optionally includes one or more of the first to third examples, and further includes a control unit, wherein computer-readable instructions are stored in a non-transitory memory, for accumulating PMs at both the positive electrode and the negative electrode of the single planar interdigitated electrode pair by accumulating the PM between one or more of the first electrode wire, the second electrode wire, and the positive electrode wire.A fifth example of the particulate sensor system optionally includes one or more of the first through fourth examples, and further includes that the PM sensor is downstream of a particulate filter in an exhaust passage, and wherein the controller further includes instructions for: generating a current at each of the single planar interdigitated electrode pairs, summing the current generated at each of the single planar interdigitated electrode pairs, and generating a total PM sensor current and regenerating the PM sensor when the total current is higher than a threshold. A sixth example of the particulate sensor system optionally includes one or more of the first through fifth examples, and further includes that the controller further includes instructions for indicating a leak in the particulate filter based on a duration between regenerations of the PM sensor.

[0068] It should be noted that the example control and estimation routines included herein may be used with various engine and / or vehicle system configurations. The control methods and routines disclosed herein may be stored as executable instructions in non-transitory memory and may be executed by the control system, including the control unit, in combination with the various sensors, actuators, and other engine hardware. The specific routines described herein may represent one or more of any number of processing strategies, such as event-driven, interrupt-driven, multitasking, multithreading, and the like. As such, various illustrated actions, operations, and / or functions may be executed in the illustrated order or in parallel, or may, in some cases, be omitted.Likewise, the order of processing is not required to implement the features and advantages of the exemplary embodiments described herein, but is provided solely for convenience of illustration and description. One or more of the illustrated actions, operations, and / or functions may be performed repeatedly depending on the particular strategy employed. Furthermore, the described actions, operations, and / or functions may graphically represent code to be programmed into non-transitory memory of the computer-readable storage medium in the engine control system, wherein the described actions are performed by executing the instructions in a system including the various engine hardware components in combination with the control unit electronics.

[0069] It is understood that the configurations and routines disclosed herein are exemplary in nature, and that these specific embodiments should not be interpreted in a limiting sense, as numerous variations are possible. For example, the technology described above can be applied to V6, inline four-cylinder, inline six-cylinder, V12, horizontally opposed four-cylinder, and other types of engines. The subject matter of the present disclosure includes all novel and non-obvious combinations and subcombinations of the various systems and configurations and other features, functions, and / or characteristics disclosed herein.

[0070] The following claims specifically point out certain combinations and subcombinations that are considered novel and non-obvious. These claims may refer to "a" element, "a first" element, or the like. Such claims are to be construed as including the inclusion of one or more such elements without requiring or excluding two or more such elements. Other combinations and subcombinations of the disclosed features, functions, elements, and / or properties may be claimed by amending the present claims or by presenting new claims in this or a related application. Such claims, whether broader, narrower, the same, or different in scope than or as the original claims, are also to be considered to be included within the subject matter of the present disclosure.

Claims

[1] Procedure comprising: Adjusting engine operation in response to a distribution of particles across multiple electrode pairs disposed within a common particulate matter (PM) sensor housing of a PM sensor; and distinguishing the size of the distribution of particles based on a resistance independently measured at each of the multiple electrode pairs; and further comprising: generating a distribution of current across the multiple electrode pairs based on the measured resistance at each of the multiple electrode pairs, wherein the multiple electrode pairs are each electrically isolated from one another and further connected to independent voltage sources and independent measuring devices. [2] The method of claim 1, further comprising: summing the current distribution of each individual electrode pair of the plurality of electrode pairs to generate a total current of the PM sensor; Determining an overall size of the distribution of particles on the plurality of electrode pairs based on the total current of the PM sensor; and in response to the total current being higher than a threshold, regenerating the PM sensor. [3] The method of claim 2, further comprising: indicating a leak in a diesel particulate filter upstream of the PM sensor based on a duration between PM sensor regenerations. [4] The method of claim 3, wherein adjusting engine operation is further based on the indication of the leak in the diesel particulate filter. [5] The method of claim 1, wherein each individual electrode pair includes a first electrode coupled to a positive terminal of a single voltage source and a second electrode coupled to a negative terminal of the single voltage source, and wherein the first electrode surrounds the second electrode and is further electrically insulated from the first electrode. [6] Procedure comprising: Accumulation of particulate matter (PM) in an exhaust at each of multiple electrode pairs located in a PM sensor; Independently generating a current at each individual electrode pair in response to accumulated particles; Differentiating particle size based on current; and Summing the current at each individual electrode pair of multiple electrode pairs to generate a total current of the PM sensor. [7] A method according to claim 6, wherein the total flow increases proportionally with the particle size. [8] The method of claim 7, further comprising: regenerating the PM sensor when the total current of the PM sensor is greater than a threshold current. [9] The method of claim 8, further comprising: indicating a leak in a particulate filter upstream of the PM sensor when a duration between regenerations of the PM sensor is less than a threshold. [10] The method of claim 9, further comprising not indicating the leak in the particulate filter if the duration between regenerations of the PM sensor is longer than the threshold. [11] The method of claim 6, wherein each individual electrode pair of the plurality of electrode pairs includes a positive contact pad connected to a positive terminal of a voltage source and a negative contact pad connected to a negative terminal of the voltage source, the positive contact pad surrounding the negative contact pad and further separated by a distance.

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