Method and system for capturing particulate matter in exhaust gas

Abstract

Method comprising: Flowing exhaust gas from downstream of a particulate filter via perforations (244) directed adjacent a lower end of an external device (216) into an exhaust gas sensor assembly (202) in a direction radially inward toward a center of the external device (216), the perforations (244) fluidly coupling chambers (209) of the external device (216) to an exhaust passage (210); Directing the exhaust gas toward an internal device (218) located between the perforations (244) and a sensor element (234) where the exhaust gas flows in a direction perpendicular to the exhaust gas flow in the exhaust passage (210); Directing the exhaust gas past the interior device (218), over the sensor element (234), and into a dome (246) of the exhaust sensor assembly (202); and then returning the exhaust gas from the dome (246) to the sensor element (234).

Description

AREA

[0001] The present application relates to the capture of particulate matter in an exhaust system. BACKGROUND / SUMMARY

[0002] Engine emissions control systems may utilize various exhaust gas sensors. An example sensor may be a particulate matter sensor indicative of the particulate matter mass and / or concentration in the exhaust gas. In one example, the particulate matter sensor may operate by detecting particulate matter (PPM) accumulation over time and providing an indication of the extent of accumulation as a measure of particulate matter levels. The PPM sensor may be located upstream and / or downstream of a diesel particulate filter and may be used to detect varying particulate matter loads on the particulate filter and for diagnostic operation of the particulate filter.

[0003] An example of an FS sensor is shown by Maeda et al. in US 2012 / 0 085 146 A1. Therein, the particulate matter sensor is mounted on top of an exhaust duct and housed within a cylindrical protective tube. The FS sensor additionally includes a sensing element positioned closer to a center of the exhaust duct so that the sensor output more accurately reflects an average soot concentration in the exhaust duct. Additionally, the FS sensor includes inlet holes designed to direct the exhaust gas into the sensor and toward the sensing element. Here, the sensing element is positioned closer to the inlet holes to allow the sensing element to capture more of the incoming particulate matter.

[0004] However, the inventors have recognized potential problems with such sensor configurations. As one example, such an arrangement may make the sensor element more susceptible to contamination by water droplets in the exhaust gas that condense on or near the intake ports. In such sensor configurations, an additional protective layer may be required to protect the soot sensor element from direct impingement of larger particles and water droplets. Adding an additional protective layer may reduce the electrostatic attraction between the charged soot particles and the sensor element electrodes, leading to reduced soot sensor sensitivity. With reduced sensitivity, the soot sensor may not be able to reliably detect particulate filter leaks.Accordingly, errors in the sensor can lead to a false indication of a diesel particulate filter (DPF) impairment and an unnecessary replacement of functioning filters.

[0005] On the other hand, if the sensor is mounted at the bottom of the exhaust duct, as shown by Paterson in US8310249 B2, water condensation at the bottom of the exhaust duct can overflow into the sensor element, thereby contaminating the sensor element. Such contamination of the sensor element can lead to sensor output fluctuations, which can reduce the accuracy of estimating the particulate load on the particulate filter. Further prior art is known from DE 20 2014 005 420 U1 and US 2015 / 0 355 067 A1.

[0006] The inventors herein have recognized the above problems and identified an approach to at least partially address the problems. In one example approach, a particulate matter sensor assembly includes a cylindrical assembly, an inner device disposed within an outer device of the cylindrical assembly, having a radius less than a radius of the outer device, and a sensor device located above an annular space near a dome located at a top end of the outer device. In this way, problems related to water droplets and larger contaminants impacting the sensor element and causing sensor output fluctuations can be reduced by disposing the sensor element above the annular space.

[0007] In one example, an exhaust particulate matter sensor assembly may be disposed downstream of an exhaust particulate filter in an exhaust passage. The particulate matter sensor may include a cylindrical assembly including perforations located at the lower end and a sensing element located at the upper end of the assembly, with the internal device located between the two. The cylindrical assembly further includes an internal flow space divided into equal sections by a plurality of partition walls, where each of the divided sections includes at least one of the perforations. A dome is located at the upper end of the assembly and extends outside the exhaust passage.

[0008] The perforations fluidly couple the inner flow space to the exhaust passage. Thus, exhaust gas flows through the perforations to enter and exit the cylindrical assembly. The inner device is radially smaller than the cylindrical assembly. Thus, a small annular space exists between the periphery of the inner device and the inner surface of the outer device. The sensing element is arranged on surfaces of the partition walls, with oppositely charged electrodes of the sensing element located on alternating partition wall surfaces. Therefore, exhaust gas flows over the sensing element into the dome, where the exhaust gas is swirled and redirected to various compartmentalized sections, and back over the sensing element. This can provide more uniform particulate deposition across the sensing element surfaces.

[0009] This improves the functionality of the sensor element and makes the sensor more reliable. Furthermore, by enabling more accurate diagnosis of the exhaust particulate filter, compliance with exhaust emission requirements can be improved. This reduces the high warranty costs for replacing functioning particulate filters. The exhaust gas can exit the sensor through the holes. The symmetrical design of the cylindrical assembly and the internal device eliminates the manufacturing process for special sensor alignment during assembly and improves sensor repeatability.

[0010] It should be understood that the foregoing summary is provided to introduce, in simplified form, a selection of concepts further described in the detailed description. It is not intended to identify important or essential features of the claimed subject matter, the scope of which is defined solely in the claims following the detailed description. Furthermore, the claimed subject matter is not limited to implementations that address disadvantages noted above or in any part of this disclosure. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 shows a schematic diagram of an engine and an associated particulate matter (PM) sensor arranged in an exhaust stream. Fig. Figure 2 shows a schematic diagram of the FS sensor, including a cylindrical assembly having a plurality of perforations that fluidly couple chambers of an internal flow space to an exhaust passage. Fig. Figure 3 shows a schematic diagram of the FS sensor showing exhaust gas flowing into the FS sensor via perforations at a lower end of the FS sensor. Fig. 4 shows an example design of electrodes formed on first surfaces of the sensor element. The Fig. 2 - Fig. 4 are shown approximately to scale. Fig. Figure 5 is a flowchart illustrating an exemplary method for collecting particulates in the exhaust stream at the sensor element disposed within the internal device of the cylindrical assembly of the FS sensor. Fig. 6 is a flowchart illustrating an exemplary method for regenerating the sensor electrodes of the FS sensor. Fig. 7 shows a flowchart illustrating an exemplary method for detecting leaks in a particulate filter located upstream of the FS sensor. Fig. 8 shows an exemplary relationship between a soot load for the FS sensor and a soot load for a particulate filter arranged upstream of the FS sensor. DETAILED DESCRIPTION

[0011] The following description relates to systems and methods for capturing particulate matter (PM) in an exhaust stream of an engine system, for example the engine system used in Fig. 1. An FS sensor may be coupled to an exhaust passage of the engine system. The FS sensor may include a cylindrical assembly including a plurality of perforations fluidly coupling an internal flow space to the exhaust passage. The cylindrical assembly may be coupled to a top surface of the exhaust passage, with the perforations located adjacent a central axis of the exhaust passage. The internal flow space may be divided into equal-sized chambers, each including at least one of the perforations. The cylindrical assembly further includes an internal device located between a sensor element and the perforations in an external device, as shown in Fig. 2. The holes act as inlets and outlets of the cylindrical assembly, as shown in Fig. 3. The sensor element may include electrodes formed on a first surface of the sensor element, as shown in Fig. 4. In addition, the sensor element may include heating elements formed on a second surface opposite the first, as shown in Fig. 4. A controller may be configured to perform a control routine, such as an exemplary routine according to Fig. 5 to accumulate particles in the exhaust gas flow via the electrodes of the sensor element. Furthermore, the controller can activate the FS sensor ( Fig. 6) periodically clean to enable continued FS monitoring. Furthermore, the controller may be designed to execute a routine, such as an example routine from Fig. 7 , to regenerate the exhaust particulate filter based on a time between regenerations of the FS sensor. An example of a filter diagnosis is shown in Fig. 8. In this way, the function of the FS sensor to estimate the filtering capacities of the DPF (and thereby to detect DPF leaks) can be increased.

[0012] The Fig. 1 - Fig. 4 show example configurations with a relative arrangement of the different components. When shown as directly touching or directly coupled to one another, such elements may be referred to as directly touching or directly coupled, respectively, at least in one example. Likewise, elements shown abutting or adjacent to one another may be abutting or adjacent to one another, respectively, at least in one example. As one example, components that are in surface-sharing contact with one another may be referred to as being in surface-sharing contact. As another example, elements that are arranged apart from one another with only a space between them and no other components may be referred to as such, at least in one example.As yet another example, elements shown above / below each other, on opposite sides of each other, or left / right of each other may be referred to as such relative to each other. Further, as shown in the figures, a topmost element or point of an element may, in at least one example, be referred to as a "top" of the component, and a bottommost element or point of the element may be referred to as a "bottom" of the component. As used herein, top / bottom, upper / lower, over / under may refer to a vertical axis of the figures and may be used to describe the positioning of elements of the figures with respect to one another. Thus, elements shown above other elements are, in one example, arranged vertically above the other elements.As yet another example, shapes of the elements depicted in the figures may be referred to as having these shapes (such as circular, straight, flat, curved, rounded, beveled, angled, or the like). Further, elements shown intersecting one another may be referred to as intersecting elements or intersecting one another, at least in one example. Still further, an element shown inside another element or outside another element may be referred to as such, in one example. It is understood that one or more components referred to as "substantially similar and / or identical" may vary from one another depending on manufacturing tolerances (e.g., within 1-5% variation).

[0013] Fig. 1 shows a schematic diagram of a vehicle system 6. The vehicle system 6 includes an engine system 8. The engine system 8 may include an engine 10 having a plurality of cylinders 30. The engine 10 includes an engine intake 23 and an engine outlet 25. The engine intake 23 includes a throttle 62 fluidly coupled to the engine intake manifold 44 via an intake passage 42. The engine outlet 25 includes an exhaust manifold 48 that ultimately leads to an exhaust passage 35 that directs exhaust gas to the atmosphere. The throttle 62 may be disposed in the intake passage 42 downstream of a boosting device, for example, a turbocharger (not shown), and upstream of an aftercooler (not shown). If present, the aftercooler may be configured to reduce the temperature of the intake air compressed by the boosting device.

[0014] The engine outlet 25 may include one or more emission control devices 70, which may be mounted in a close-coupled position in the exhaust. One or more emission control devices may include a three-way catalyst, NOx trap, SCR catalyst, etc. The engine outlet 25 may further include a diesel particulate filter (DPF) 102 that temporarily filters particulate matter from incoming gases located upstream of the emission control device 70. In one example, as shown, the DPF 102 is a diesel particulate matter containment system. The DPF 102 may have a monolithic structure, such as that made of cordierite or silicon carbide, with a plurality of channels inside for filtering particulate matter from diesel exhaust.The exhaust gas from the tailpipe, from which FS has been filtered following passage through the DPF 102, may be measured in an FS sensor 106 and further processed in the emissions control device 70 and expelled into the atmosphere via the exhaust passage 35. In the depicted example, the FS sensor 106 is a resistive sensor that estimates the filtering efficiency of the DPF 102 based on a change in conductivity measured at the FS sensor electrodes. A schematic view 200 of the FS sensor 106 is shown in FIG. Fig. 2, as described in more detail below.

[0015] The vehicle system 6 may further include the control system 14. As shown, the control system 14 receives information from a plurality of sensors 16 (various examples of which are described herein) and sends control signals to a plurality of actuators 81 (various examples of which are described herein). In one example, the sensors 16 may include an exhaust flow rate sensor 126 configured to measure an exhaust flow rate through the exhaust passage 35, an exhaust gas sensor (located in the exhaust manifold 48), a temperature sensor 128, a pressure sensor 129 (located downstream of the emissions control device 70), and an FS sensor 106. Other sensors, such as additional sensors for pressure, temperature, air-fuel ratio, exhaust flow rate, and composition, may be coupled to various locations in the vehicle system 6.In another example, the actuators may include fuel injectors 66, a throttle 62, DPF valves (not shown) that control filter regeneration, an electrical circuit switch, etc. The control system 14 may include a controller 12. The controller 12 may be configured with computer-readable instructions stored on non-transitory memory. The controller 12 receives signals from the various sensors. Fig. 1 , processes the signals and sets the different actuators Fig. 1 to adjust engine operation based on the received signals and instructions stored in a memory of the controller. In one example, during operation of the FS sensor to accumulate soot particles, the controller may send a control signal to an electrical circuit to apply a voltage to the sensor electrodes of the FS sensor to trap the charged particles on the surface of the sensor electrodes. In another example, during regeneration of the FS sensor, the controller may send a control signal to a regeneration circuit to close a switch in the regeneration circuit for a threshold period to apply a voltage to heating elements coupled to the sensor electrodes to heat the sensor electrodes. In this way, the sensor electrodes are heated to burn off soot particles deposited on the surface of the sensor electrodes.Example routines are given here in relation to the . Fig. 5 - Fig. 7 described.

[0016] With reference to Fig. 2 is a schematic view 200 of an exemplary embodiment of a particulate matter (PS) sensor assembly 202 (such as the PS sensor 106 of Fig. 1 ). The FS sensor assembly 202 may be configured to measure FS mass and / or concentration in the exhaust gas and, as such, may be connected to an exhaust passage 210 (e.g., as shown in Fig. 1) which is arranged upstream or downstream of a diesel particulate filter (such as the DPF 102 shown in Fig. 1). Portions of the FS sensor assembly 202 shown in dashed lines are obscured by solid-line portions of the figure.

[0017] An axis system 290 is shown, which includes three axes: an x-axis parallel to the horizontal direction, a y-axis parallel to the vertical direction, and a z-axis perpendicular to both the x and y axes. A direction of gravity 299 is shown with an arrow parallel to the vertical direction. A central axis 295 of the exhaust passage 210 is shown parallel to the horizontal direction. An axial axis 298, which can also be used as a central axis 298 of the FS sensor assembly 202, is perpendicular to the central axis 295.

[0018] In the schematic view 200, the FS sensor assembly 202 is disposed within the exhaust passage 210, with exhaust gases flowing (horizontally along the X-axis) from a position downstream of the diesel particulate filter toward an exhaust tailpipe, as indicated by arrows 258. The FS sensor assembly 202 is installed within the exhaust passage 210. Here, the FS sensor assembly 202 is cylindrical in shape. In another example, the assembly may be a hollow elliptical structure disposed within the exhaust passage 210. As shown, the FS sensor assembly 202 is symmetrical about the Y-axis.

[0019] The FS sensor assembly 202 extends along the Y-axis in a direction perpendicular to the direction of exhaust flow 258. Further, the FS sensor assembly 202 may include an upper end 260 and a lower end 270. A portion of the upper end 260 may be coupled to a top surface 212 of the exhaust passage 210 (and not coupled to a bottom surface 214 of the exhaust passage 210, for example). Thus, the upper end 260 may be shaped similarly to the top surface 212 of the exhaust passage 210 (e.g., curved). Alternatively, the upper end 260 may be flat, with only the periphery of the upper end 260 coupled to the top surface 212. However, the lower end 270 hangs freely within the exhaust passage 210 and is not coupled to any surface of the exhaust passage 210. In one example, a length L of the FS sensor assembly 202 extends beyond the central axis 295 of the exhaust passage 210.In this way, the lower end 270 is below the central axis 295 relative to the direction of gravity 299. In some examples, the length L may be substantially equal to a radius of the exhaust passage 210 such that the lower end 270 reaches the central axis 295 and does not extend beyond it. The upper end 260 may be mounted into the top surface 212 of the exhaust passage 210 in a variety of ways. For example, the upper end 260 may be inserted, screwed, or held to the top surface 212 via additional screws or holes (not shown). The upper end 260 is in sealing contact with the top surface 212. Accordingly, no exhaust gas 258 will escape through the intersection between the upper end 260 and the top surface 212 into an internal combustion engine (e.g., engine 10 in the embodiment of FIG. Fig. 1 ) or to the ambient air.

[0020] The upper 260 and lower 270 ends are sealed to the exhaust passage 210. Accordingly, no exhaust gas flows through the upper end 260 or the lower end 270. The upper end 260 and lower end 270 are substantially identical circles. It will be understood that the upper and lower ends may have other shapes without departing from the scope of the present disclosure, for example, square-shaped. As a result, the FS sensor assembly 202 includes an external device 216 extending between and sealingly coupled to the upper 260 and lower 270 ends. The external device 216 is a cylinder with a length L. It will be understood that the external device 216 may have other suitable shapes (e.g., spherical, cubic, right-angle prism-like, etc.) without departing from the scope of the present disclosure.In this way, the FS sensor assembly 202 may also be referred to as a cylindrical assembly having a cylindrical outer device 216 coupled to an exhaust duct of the exhaust passage 210.

[0021] An inner device 218 is circular and located within the outer device 216. The inner device 218 may comprise a material substantially identical to a material of the outer device 216. Therefore, both the inner device 218 and the outer device 216 are impervious to the flow of exhaust gas. The material may be metal, plastic, alloy, or a combination thereof. The inner device 218 is the same in shape and material as the upper 260 and lower 270 ends, except that its diameter is smaller than the diameters of the upper 260 and lower 270 ends, such that a flow space exists between the inner device 218 and the outer device 216, as described below.

[0022] The outer device 216 is a cylindrical guard of radius R1. The inner device 218 is a circular guard of radius R2. The radii R1 and R2 are measured from the axial axis 298, which passes through the geometric centers of the upper 260 and lower 270 ends. Here, the inner device 218 is smaller than the outer device 216 (e.g., R2 (R1)) and an annular gap 224 and / or annular space 224 is located between the outer device 216 and the inner device 218. Thus, the inner device 218 is spaced from the inner surfaces of the outer device 216. The annular gap 224 is uniform between the outer device 216 and the inner device 218, with a gap 226 indicating the width of the annular gap 224. In this way, the inner device 218, the outer device 216, and the upper 260 and lower 270 ends include centers aligned along the axial axis 298.The inner device 218 is located asymmetrically within the outer device 216, such that it is closer to the upper end 260 than the lower end 270. In other embodiments, the inner device 218 may be located symmetrically within the outer device 216, exactly in the middle of the upper end 260 and the lower end 270. Both the outer device 216 and the inner device 218 are fixed and do not slide, rotate, or move.

[0023] In one example, the length of the FS sensor assembly 202 may be selected such that the lower end 270 does not extend beyond the central axis 295. In this way, the average soot particle concentration in the exhaust passage 210 may be adequately reflected in the sensor assembly by positioning the sensor assembly 202 close to the central axis 295 of the exhaust passage 210. Additionally or alternatively, the FS sensor assembly 202 includes a plurality of perforations 244 evenly spaced around the exterior device 216 adjacent the lower end 270. In some examples, the lower end 270 may extend below the central axis 295 such that the perforations 244 are located along the central axis 295. In either case, the sensitivity of the FS sensor assembly 202 may be increased, and the sensor may be made more reliable.Furthermore, enabling more accurate diagnosis of the exhaust particulate filter can improve compliance with exhaust emission requirements. This reduces the high warranty costs for replacing functioning particulate filters, improves exhaust emissions, and extends the service life of exhaust components.

[0024] As shown, each of upper end 260, lower end 270, and inner device 218 are parallel to the direction of exhaust flow 258. The inner device 218 is fixed within and spaced from the inner surfaces of the outer device 216. The inner device 218 is fixedly coupled to the outer device 216 via a plurality of partition walls 206. In some examples, the inner device 218 is located within the outer device 216 via a plurality of spacers. As shown, there are eight partition walls 206 that divide an inner flow space 242 of the outer device 216 into eighths. The partition walls 206 are substantially the same height and width and intersect along the axial axis 298 and / or the geometric center of the outer device 216. The partition walls 206 traverse from the upper end 260 to the lower end 270 and are pressed against an inner surface of the outer device 216 over the entire length L of the outer device 216.In the other type, the partition walls 206 are located within the outer device 216, where the partition walls are physically coupled to the outer device 216 along their outer edge, while they are physically coupled to each other along their inner edges, which intersect at the axial axis 298, and where the inner device 218 is installed within the outer device 216 via the partition walls 206. Accordingly, portions of the inner flow space 242 located between the first and second partition walls 206 are fluidly separated from portions of the inner flow space 242 located between the second and third partition walls. Here, portions of the inner flow space 242 located between the partition walls may be referred to as chambers 209 and / or flow sections 209. Each chamber of the chambers 209 is fluidly separated from an adjacent chamber, wherein each chamber of the chambers 209 has substantially the same volume.Each chamber of the chambers 209 includes at least one of the perforations 244. In one example, each chamber of the chambers 209 includes exactly one of the perforations 244. Thus, in one example, there are exactly eight perforations 244 located on a common plane and facing radially outward directions. The perforations 244 are substantially identical to one another, with each of the perforations 244 being a circle. However, the perforations 244 may be oval, square, or of any other suitable shape for admitting and ejecting exhaust gas to / from the FS sensor assembly 202.

[0025] The perforations 244 are evenly spaced around the outer device 216, adjacent the lower end 270, and are configured to introduce exhaust gas into and expel exhaust gas from the FS sensor assembly 202. Specifically, each of the perforations 244 functions as an inlet and an outlet for an individual one of the chambers 209. For example, the perforation 244a is the inlet and outlet for the chamber 209a.

[0026] Thus, the perforation 209a allows exhaust gas to flow only into the chamber 209a. Furthermore, exhaust gas in the chamber 209a can only flow out of the chamber 209a to the exhaust passage 210 via the perforation 244a.

[0027] During a cold start of the vehicle, the exhaust gas may not be warm enough to convert water in the exhaust passage into vapor (gaseous state), and therefore water may sometimes remain in a liquid state. By installing the internal device 218 within the external device 216, the sensor may be protected from water droplets and / or large particles due to the fact that the gap 226 is smaller than water droplets and / or large particles. This may prevent or reduce large particles from flowing to the sensor element 234 located at the top 260 of the external device 216 adjacent to a dome 246. Exhaust gas may swirl within the dome 246 and flow to a chamber different from the chamber from which it came. Alternatively, a first chamber may allow exhaust gas to flow into the dome 246, and the exhaust gas may flow from the dome 246 into a second chamber different from the first chamber.Thus, the dome 246 is a hemisphere with a geometric center aligned with the axial axis 298. In this manner, the dome 246 is located above the intersection between the partition walls 206. The dome 246 protrudes through a recess in the top surface 212 of the exhaust passage 210 such that exhaust gas within the dome 246 is located entirely outside the exhaust passage 210. The dome 246 is completely sealed to prevent exhaust gas from flowing out of the dome 246 to an engine and / or ambient air.

[0028] The sensor element 234 is coupled to the partition walls 206 near the dome 246. The sensor element 234 is positioned downstream of the gap 226 of the annular space 224 relative to a direction of exhaust flow in the FS sensor assembly 202 that is substantially parallel to the axial axis 298. In the other type, the internal device 218 is located between the perforations 244 and the sensor element 234.

[0029] The sensor element 234 includes a substrate 240 (shown with a cross pattern) having electrodes 236 formed on a first surface and a heating element (in Fig. 4) formed on a second, opposite surface. In other words, the electrodes 236 and the heating element are formed on two opposite sides of the substrate 240, thus they are separated by a thickness of the substrate 240. Accordingly, the sensor element 234 may be a square element to utilize the flat shape of the partition walls 206. However, the sensor element 234 may be rectangular, circular, triangular, or the like without departing from the scope of the present disclosure. For a square-shaped element 234, the electrodes 236 may be linear. Various other geometries may alternatively be possible without departing from the scope of the disclosure. Oppositely charged electrodes are shown in solid and dashed lines. As shown, one partition of the partition walls 206 does not include both types of electrodes 236.For example, a positive electrode is located on a first partition, and partitions directly adjacent to the first partition comprise negative electrodes. Thus, the partitions 206 alternate between comprising positive and negative electrodes. In some examples, individual partitions of the partitions 206 may comprise both positive and negative electrodes. Accordingly, the electrodes 236 may interdigitate in a comb-like structure. However, it will be understood that the electrodes may be spiral or have other suitable shapes to determine soot in the exhaust stream. The soot particles in the exhaust may be sandwiched between the interdigitated electrodes as described with reference to FIG. Fig. 4 declared to be deposited.

[0030] The sensor element 234 can be arranged in the external device 216 above the internal device 218 such that the electrodes 236 are directed toward chambers 209, while the heating element formed on the opposite surface is pressed against the partition walls 206. The sensor element 234 is located on both sides of a partition of the partition walls 206 with identically charged electrodes 236 on both sides. This means that a partition of the partition walls 206 with a portion of the substrate 240 comprising electrodes 236 in a continuous line includes continuous line electrodes and a heating element on the first and second surfaces of the partition wall. As shown, the first and second surfaces are directed toward different chambers 209 and thus may experience different soot deposits.By positioning the sensor element 234 over the internal device 218 and thus the gap 226, problems with water droplets and larger contaminants impinging on the sensor element and causing fluctuations in the sensor output can be reduced. The description of the electrical circuit and the composition of the sensor element and substrate is . Fig. 4 common.

[0031] Now with reference to Fig. 3 shows a schematic view 300 of the exhaust flow through the FS sensor assembly 202. Specifically, the view 300 depicts exhaust flowing into the FS sensor assembly 202 via the perforations 244 located adjacent the lower end 270 of the external device 216. Here, the perforations 244 are configured to receive exhaust from the exhaust passage 210 and direct the exhaust into the internal flow plenum 242 formed in the external device 216. Directing the exhaust into the internal flow plenum 242 involves flowing exhaust in a radially inward direction relative to the external device 216. The exhaust may enter the external device 216 via one of the perforations 244. In one example, exhaust gas may easily flow through upstream holes (e.g., holes 244a and 244h) and enter the FS sensor assembly 202.Additionally, the exhaust gas may turn in a direction opposite the direction of exhaust flow (indicated by arrows 258) to enter the FS sensor assembly 202 via downstream perforations (e.g., perforations 244d and 244e). Still further, the exhaust gas may turn in a direction perpendicular to the direction of exhaust flow (arrows 258) via sideways perforations (e.g., perforations 244b, 244c, 244f, and 244g). It will be understood that in some examples, more exhaust gas may enter the FS sensor assembly 202 via perforations 244a and 244h compared to the other perforations. In addition, larger or heavier contaminants and / or water droplets 274 (such as having a size or weight above a threshold) in the exhaust gas can only enter the FS sensor assembly via upstream perforations 244a and 244h.Accordingly, the larger contaminants and / or water droplets 274 may have too much momentum to be able to spin around and enter the FS sensor assembly 202 via the side holes and the downstream holes. This may prevent many large particles and / or water droplets from entering the FS sensor assembly 202. Fig. Figure 3 shows a comparable view of the sensor assembly 202 shown in Fig. 2. Thus, components in the following figures may be numbered the same.

[0032] As shown, each of the perforations 244a, 244b, 244c, 244d, 244e, 244f, 244g, and 244h corresponds to each of the chambers 209a, 209b, 209c, 209d, 209e, 209f, 209g, and 209h, respectively. As described above, each chamber is fluidly separated from the other chambers. Furthermore, each of the chambers is fluidly coupled to the dome 246. Thus, exhaust gas from the chamber 209b can flow into the dome 246 and to the chamber 209g, with the exhaust gas flowing back through the exhaust passage via the perforation 244g. In this way, exhaust gas can flow from each chamber 209 to the dome 246 and then from the dome 246 into each of the chambers 209.

[0033] As previously mentioned with reference to Fig. 2, the FS sensor assembly 202 is sealed except for the perforations 244. In this manner, the FS sensor assembly 202 includes no inlets or additional outlets other than the perforations 244. Therefore, exhaust gas within the FS sensor assembly flows back into the exhaust passage either through the perforation through which it entered the FS sensor assembly and / or through another perforation. A general exhaust flow through the FS sensor assembly 202 may include exhaust gas flowing toward the upper end 260, through the dome 246, downward toward the lower end 270, and out of the FS sensor assembly 202 through one of the perforations 244, as described below. It will be understood that the exhaust flow into the FS sensor assembly 202 flows in a direction opposite to the exhaust flow out of the FS sensor assembly 202.

[0034] An exemplary exhaust flow is shown, with exhaust entering chamber 209a via perforation 244a (as shown by arrow 278) in a radially inward direction relative to external device 216. The exhaust in internal flow space 242 is forced to travel toward the upper end 260 of FS sensor assembly 202. Specifically, the exhaust, as well as large particles and / or water droplets, flow in a direction perpendicular (as indicated by arrow 281 and solid black circles 274) to the direction of exhaust flow in exhaust passage 210 (as indicated by arrows 258). It will be understood that exhaust arrow 281 may also swirl and / or flow in an annular manner within chamber 209a, but its general flow direction is parallel to arrow 281 shown in Fig. 3. The exhaust then flows through the annular space 224 between the outdoor device 216 and the indoor device 218 (shown by arrow 283) while the large particles and / or water droplets 274 impinge on the indoor device 218. As described above, the annular space 224 may be too small for large particles and / or water droplets to pass through. Additionally or alternatively, the momentum of the large particles and / or water droplets may force the large particles and / or water droplets to flow adjacent the axial axis 298 where the indoor device 218 is located.

[0035] Exhaust gas in chamber 209a flows over the surface of the sensor element 234 before flowing into the dome 246 (shown by arrow 284). The exhaust gas flow 284 may deposit particulates on the substrate 240 before flowing into the dome 246. The particulates may electrically couple oppositely charged electrodes of the electrodes 236. As described above, each of the partition walls includes only a positive or negative electrode. Additionally, the partition walls alternate such that adjacent partition walls include oppositely charged electrodes. In this manner, a chamber includes at least one of a positive electrode and a negative electrode. For example, chamber 209a is formed across two partition walls of the partition walls 206, with one partition wall shown as having a dashed line electrode and the other partition wall shown as having a solid line electrode.As particles build up on substrate 240 in chamber 209a, the electrodes can be coupled, as described below. In some examples, only oppositely charged electrodes in a chamber can be electrically coupled. In other examples, charged electrodes of different chambers can be electrically coupled.

[0036] In some examples, the exhaust gas may impinge on the top end 260 before following a contour of the top end 260 into the dome 246. Exhaust gas flows in an upward direction to enter the dome 246 because the dome is located outside the exhaust passage 210 and vertically above the FS sensor assembly 202, as described above. Exhaust gas in the dome may swirl around before exiting the dome 246 and entering each of the chambers 209. In one example, the exhaust gas in the dome 246 may be uniformly divided such that an equal amount of exhaust gas enters each of the chambers 209. However, as shown by arrows 285, all exhaust gas exiting the dome 246 enters chamber 209e.

[0037] Additionally, the exhaust gas flowing into and out of the dome 246 bypasses the sensor element 234. The arrangement of the sensor element 234 has several advantages. First, the sensor element 234 is positioned to take exhaust gas samples from each of the chambers 209, which can improve the accuracy of the measured FS. Second, the sensor element can receive a uniform FS deposition due to the turbulence created in the FS sensor assembly 202 by the interior device 218 and the dome 246. As a result, the sensor element 234 can accurately estimate the FS in the exhaust stream.

[0038] Specifically, the exhaust gas in the chamber 209e flows downward in a direction perpendicular to the arrows 258 and opposite to the arrow 281 (as indicated by arrow 286). Thus, exhaust gas flowing out of the dome 246 and into the chambers 209 flows in a direction opposite to a direction of the arrows 281 and 283. This means that exhaust gas entering the chamber 209e from the exhaust passage 210 (not shown) flows in a direction opposite to the arrow 286. The exhaust gas flows through the annular space 224 between the outer device 216 and the inner device 218. The exhaust gas is then directed toward the lower end 270, where it can turn and flow through the perforation 244e. Exhaust gas flowing through the perforation 244e flows in a direction parallel to the direction of exhaust flow in the exhaust passage 210 (arrows 258), as shown by the arrows 287.The exhaust gas exiting the FS sensor assembly 202 combines with the exhaust gas in the exhaust passage, as indicated by arrows 258 and 288. Therefore, exhaust gas flowing through downstream perforations (e.g., 244d and 244e) and into the exhaust passage 210 flows in a direction parallel to the exhaust flow (arrows 258). Furthermore, exhaust gas flowing through side-facing perforations (e.g., 244b, 244c, 244f, and 244g) and into the exhaust passage 210 flows in a direction perpendicular to the exhaust flow (arrows 258) before turning and flowing in a direction parallel to the exhaust passage. Still further, exhaust gas flowing through upstream perforations (e.g., 244a and 244h) and into the exhaust passage 210 flows in a direction opposite to the exhaust flow (arrows 258) before turning and flowing in a direction parallel to the exhaust passage.In this way, the holes 244 act as inlets and outlets of the FS sensor assembly 202.

[0039] In summary, exhaust gas flows through a perforation of the perforations located near a lower end of the FS sensor assembly, where the exhaust gas enters a chamber of the internal flow space of the FS sensor assembly. The internal flow space is divided into a plurality of equally sized chambers that are separated from each other. As the exhaust gas flows up and around the internal device in the chamber, it flows past the sensor element and into a dome. Thus, the exhaust gas can deposit a number of particles on the substrate of the sensor element before flowing into the dome, where the exhaust gas can be redirected into one of the chambers of the internal flow space. The exhaust gas flows in a downward direction, past the sensor element, where the exhaust gas can again deposit particles, and towards the lower end of the FS sensor assembly. The exhaust gas flows out of a perforation of the chamber in a radially outward direction relative to the exhaust passage.

[0040] In some examples, additionally or alternatively, a majority of exhaust gas may enter the FS sensor assembly via the upstream perforations, and a majority of exhaust gas may exit the FS sensor assembly via the downstream perforations. With reference to Fig. 3, the upstream holes are located to the left of the axial axis and the downstream holes are located to the right of the axial axis. This can provide a substantially U-shaped exhaust flow to the FS sensor assembly.

[0041] Thus, an exemplary particulate matter sensor includes a pair of electrodes formed on a first surface of a sensor element, a heating element formed on a second surface of the sensor element, the second surface opposite the first surface, and a plurality of partition walls dividing an internal flow space of the particulate matter sensor into equal-sized chambers. Additionally or alternatively, each of the partition walls is in face-sharing contact with the second surface of the sensor element, and where the first surface of the sensor element is exposed to the annular space. Additionally or alternatively, the partition walls are impermeable to exhaust gas flow, and where a number of partition walls is equal to eight. Additionally or alternatively, each of the partition walls corresponds to a positive or negative electrode of the sensor element, and where adjacent partition walls correspond to oppositely charged electrodes.Additionally or alternatively, the partition walls form a shape of an eight-pointed star in a plan view symmetrical about a center of the particulate matter sensor. Additionally or alternatively, each of the chambers comprises at least one perforation fluidly coupling the chamber to an exhaust passage. Additionally or alternatively, the electrodes comprise linear positive and linear negative electrodes, and where the positive and negative electrodes are located on different partition walls. Additionally or alternatively, the partition walls are located in the outdoor device, the partition walls are physically coupled to the outdoor device along a long outer edge, while they are physically coupled to each other along a long inner edge, and where the indoor device is installed in the outdoor device via the partition walls.

[0042] Now, with reference to Fig. 4 a schematic view 400 of the sensor element 234 according to Fig. 2 and an attached electrical circuit 414. Specifically, the electrodes 236 formed on a flat substrate 240 are shown. Since each of the partition walls 206 is rectangular and abuts one another along the axial axis 298 to evenly divide the internal flow space, the partition walls 206 form a dome (e.g., dome 246 of Fig. 2 and Fig. 3) an eight-pointed star. Thus, it may be advantageous to include a square substrate for the sensor element to increase the surface area available for soot particle adsorption. However, various other geometries of the substrate and electrode structure may be possible without departing from the scope of the present disclosure. Some example structures include rectangular or circular substrates with interdigitated comb electrodes.

[0043] In view 400, the substrate 240 of the sensor element 234 is square with a length less than a radius R1 of the partition walls 206. The substrate 240 of the sensor element 234 may be made of electrically insulating materials. Examples of possible electrically insulating materials may include oxides such as aluminum oxide, zirconia, yttrium oxide, lanthanum oxide, silicon dioxide, and combinations thereof, including at least one of the foregoing or any similar material capable of inhibiting electrical connection and providing physical protection for the electrodes 406 and 408. In some examples, the substrate 240 may be constructed of a porous ceramic material (e.g., porosity of approximately 60%).

[0044] The sensor electrode 236 includes a pair of electrodes 406 and 408 formed on separate surfaces of the sensor element 234. Here, the pair of electrodes 406 and 408 may form linear prongs, indicated by dotted and solid lines, respectively, in view 400. These electrodes may 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 thereof that include at least one of the foregoing metals. Each electrode of the pair may be constructed of the same material as the other electrode of the pair or a different material. For example, the electrode 406 may be constructed of the same material as the electrode 408. In another example, the electrode 406 and the electrode 408 may be constructed of different materials.The distance between the "prongs" of the two electrodes can typically range from 30 micrometers to 50 micrometers, with the linewidth of each individual "prong" being approximately the same, although the latter may be excluded. The distance can be measured from a first electrode of the electrodes 406 to the axial axis 298 and to a single electrode of the electrodes 408 adjacent to the first electrode. As shown, the electrodes 406 and 408 alternate such that one electrode of the electrodes 408 is located between each of the electrodes 406.

[0045] Electrodes 406 and 408 may be electrically connected to an electrical circuit 414. Electrode 408 of sensor element 234 is connected by connecting wire 412 to a positive terminal of a voltage source 416 of electrical circuit 414. Thus, electrode 408 may be referred to as a positive electrode. Likewise, electrode 406 of sensor element 234 is connected via a connecting wire 410 to a measuring device 418 and further connected to a negative terminal of voltage source 416 of electrical circuit 414. Thus, electrode 406 may be referred to as a negative electrode. Connecting wires 410 and 412, voltage source 416, and measuring device 418 are part of electrical circuit 414 and are located outside exhaust passage 210 (for example, 1 meter away).Furthermore, the voltage source 416 and the measuring device 418 of the electrical circuit 414 can be controlled by a controller, such as the controller 12 of FIG. Fig. 1, so that particulate matter collected at the FS sensor assembly 202 can be used, for example, to detect leaks in the DPF. Therefore, the measuring device 418 can be any device capable of reading a change in resistance (or current) across the electrodes, for example, a voltmeter (or an ammeter). When FS or soot particles deposit between the electrodes 406 and 408, the current measured between the electrodes 406 and 408 can begin to increase, which is measured by the measuring device 418. The controller 12 can be capable of determining the current and deriving a corresponding FS or soot load at the electrodes 406 and 408 of the sensor element 234 of the FS sensor assembly (e.g., FS sensor assembly 202 according to Fig. 2 and Fig. 3). By monitoring the load on the sensor element 234, the exhaust soot load downstream of the DPF can be determined and thus used to diagnose and monitor the condition and functionality of the DPF.

[0046] In view 400, the electrode 406 includes a plurality of linear prongs of equal length. The electrode 406 (synonymously referred to as the negative electrode) includes a substantially straight portion 420 that connects the electrode 406 to the connecting wire 410. Here, the straight portion 420 extends over the substrate 240. This forces the electrode 406 to also extend over the substrate 240, thereby preventing the electrode 406 from contacting the electrode 408. The electrode 406 is located symmetrically about the axial axis 298.

[0047] Similar to the negative electrode 406, the electrode 408 includes a plurality of linear prongs that are substantially equal in length. The electrode 408 (synonymously referred to as the positive electrode) includes a substantially straight section 422 that connects the electrode 408 to the connecting wire 412. Here, the straight section 422 may be located below the straight section 420, which follows the contour of the substrate 240 and rests on top of it. This means that the straight section 422 and the electrode 408 are flush with the substrate 240 before reaching an end point of the substrate 240. Alternatively, the straight section 420 and the electrode 406 are spaced away from the substrate 240 before its end point to prevent contact between the electrodes 406 and 408.In one example, a length of the straight section 422 of the positive electrode 408 may be equal to, less than, or greater than the length of the straight section 420 of the negative electrode 406. The positive electrode 408 is located symmetrically about the axial axis 298. Furthermore, the positive electrode 408 extends in directions that are oblique to the negative electrode 406. Specifically, an angle between the negative electrode 406 and the positive electrode 408 is exactly 45°.

[0048] The heating element 238 is shown on a second surface of the substrate 240 in surface-sharing contact with the partition walls 206. Each partition of the partition walls 206 is sandwiched between an innermost heating element layer, a middle substrate layer, and an outer electrode layer. The outer electrode layer of a partition wall comprises like-charged electrode prongs (e.g., either positive or negative). In this way, each chamber (e.g., chambers 209 of the Fig. 2 and Fig. 3) positive 408 and negative 406 electrodes.

[0049] Now, with reference to Fig. 5 an exemplary method 500 for collecting particulates in the exhaust stream via sensor electrodes disposed within the FS sensor (such as a Fig. 1 shown FS sensor 106 and / or the FS sensor assembly 202 of Fig. 2). Specifically, particles in the exhaust stream can be collected via electrodes formed on surfaces of the partition walls arranged within a cylindrical assembly of the FS sensor. The cylindrical assembly includes a circular inner device arranged within a cylindrical outer device and separated by a gap. Additionally, the cylindrical assembly includes a plurality of perforations for directing exhaust gas into and out of chambers of the cylindrical assembly.

[0050] The instructions for performing method 500 and the remaining methods 600 and 700 included herein may be executed by a controller based on instructions stored in a memory of the controller and in conjunction with signals received from sensors of the engine system, for example, as described above with reference to Fig. 1. The controller may use motor actuators of the motor system to adjust motor operation according to the methods described below.

[0051] At 502, method 500 includes determining and / or estimating engine operating conditions. Certain engine operating conditions may include, for example, engine speed, exhaust flow rate, engine temperature, exhaust air-fuel ratio, exhaust temperature, duration (or distance) since a last DPF regeneration, FS load on the FS sensor, boost level, ambient conditions such as barometric pressure and ambient temperature, etc.

[0052] Method 500 proceeds to 504, wherein a portion of exhaust gas collected from downstream of the particulate filter (such as DPF 102 of Fig. 1 ) is directed through perforations into an FS sensor. The perforations are circular and located adjacent to a lower end of an external device. As previously explained, the perforations fluidly couple the chambers of the internal flow space of the external device to an exhaust passage. Thus, the perforations allow exhaust gas into the chambers. The direction of the exhaust flow through the perforations can, for example, be parallel, oblique, perpendicular, and / or opposite to the direction of the exhaust flow in the exhaust duct, as described above.

[0053] Next, method 500 proceeds to 506. At 506, method 500 includes directing the exhaust gas toward an annular space formed between the outdoor device and the indoor device in a direction perpendicular to the direction of exhaust flow in the exhaust passage. As described above, the exhaust gas flows upward in a direction opposite to gravity.

[0054] Method 500 proceeds to 508. At 508, method 500 includes flowing exhaust gas through the annular space toward the sensor element located adjacent the top of the sensor. The sensor element is physically coupled to surfaces of the partition walls that divide the internal flow space of the outdoor device into substantially equal-sized chambers. As described above, the heating element of the sensor element is pressed against surfaces of the partition walls, and the electrodes are exposed to the exhaust gas in the chambers. Method 500 proceeds to 510.

[0055] At 510, method 500 includes accumulating particles between electrodes formed on the sensor element. Specifically, at 510, particles in the chamber adjacent to the top of the external device are directed toward the electrodes of the sensor element, and the particles are deposited over the electrodes. The direction of exhaust flow into the chamber is perpendicular to the direction of exhaust flow in the exhaust passage. As previously described, the sensor element, including the electrodes, is disposed above the internal device. The positive electrodes are connected to the positive terminal of a power supply, and the negative electrodes are connected to a measuring device and then to the negative terminal of the power supply. When the controller applies a voltage to the sensor electrodes, particles in the chambers can experience a strong electric field, allowing them to accumulate between the electrodes.Additionally, a load on the sensor electrodes is estimated based on a current generated in the sensor electrodes. As particles accumulate on the surface of the sensor electrodes, the resistance of the electrodes begins to decrease, and a current measured by the measuring device begins to increase. The controller may be able to infer a load on the sensor electrodes based on the current measured on the electrodes. Method 500 then proceeds to 512.

[0056] At 512, method 500 includes redirecting the exhaust flow into the dome toward the chambers of the sensor toward the perforations in a direction perpendicular to the direction of exhaust flow in the exhaust duct to expel exhaust into the exhaust passage. In some examples, a majority of the exhaust gas may flow through the downstream perforations due to its low static pressure and less exhaust gas entering the sensor via the downstream perforations. Method 500 then proceeds to 514.

[0057] At 514, method 500 includes periodically checking whether the sensor electrode has met the regeneration conditions. Specifically, the FS sensor regeneration conditions may be considered met when the soot load at the FS sensor is above a threshold, or when a resistance of the FS sensor (set to temperature) drops to a resistance equal to a threshold, or when a current of the FS sensor exceeds a threshold. In some examples, if a time equal to a threshold duration has elapsed since an immediately preceding sensor regeneration, the regeneration condition may be considered met. The FS sensor may request a regeneration to enable further FS detection.

[0058] If the regeneration conditions are met (e.g., “YES” at 514), method 500 proceeds to 518 where the FS sensor may be regenerated by performing a method described in Fig. 6. In short, regeneration of the FS sensor can be initiated by heating the sensor. The FS sensor can be heated, for example, by actuating a heating element formed on another surface of the sensor element, opposite the surface containing the electrodes. Here, the controller can close the switch in a regeneration circuit, thereby applying a voltage to the heating element, causing the heating elements to heat up. Furthermore, the controller cannot apply voltages to the sensor electrodes while the sensor is being regenerated. Accordingly, the sensor electrodes cannot collect soot during sensor regeneration. Therefore, the heating element can be actuated until the soot load on the sensor is sufficiently reduced by oxidation of the carbon particles between the electrodes. However, if the conditions for regenerating the FS sensor are not met (e.g.,"NO" at 514), the method proceeds to 516 where the particles may continue to be collected at the sensor electrodes and the method ends.

[0059] Thus, an exemplary method may include flowing exhaust gas from downstream of a particulate filter via perforations adjacent a lower end of an external device into an exhaust sensor assembly in a radially inward direction toward a center of the external device, the perforations fluidly coupling chambers of the external device to an exhaust passage, and directing the exhaust gas toward an internal device located between the perforations and a sensor element, where the exhaust gas flows in a direction perpendicular to the exhaust flow in the exhaust passage. Additionally or alternatively, the method further comprises flowing the exhaust gas through an annular space between the internal device and the external device toward the sensor element.Additionally or alternatively, the sensor element is adjacent to a dome of the exhaust gas sensor assembly, which is located outside the exhaust passage, and where the dome is hollow and designed to direct exhaust gas to the chambers after the exhaust gas has flowed over the sensor element, wherein the exhaust gas flows in a direction perpendicular to the exhaust gas flow in the exhaust passage. Additionally or alternatively, the exhaust gas sensor assembly does not include any inlets or additional outlets other than the perforations.

[0060] Now, with reference to Fig. 6 a method 600 for regenerating the FS sensor (such as one in Fig. 1 shown FS sensor 106 and / or the FS sensor assembly 202 from Fig. 2). Specifically, if the soot load on the FS sensor is above the threshold, or if a temperature-adjusted resistance of the FS sensor drops to a threshold resistance, the FS sensor regeneration conditions may be considered met, and the FS sensor may request a regeneration to enable further FS detection. At 602, a regeneration of the FS sensor may be initiated, and the FS sensor may be regenerated by heating the sensor at 604. The FS sensor may be heated by actuating a heating element until the soot load on the sensor is sufficiently reduced by oxidation of the carbon particles between the electrodes.

[0061] Regeneration of the FS sensor is typically controlled using timers, and the timer may be set to a threshold-length period at 602. Alternatively, sensor regeneration may be controlled by using a temperature measurement of the sensor tip, by controlling the power provided to the heater, or any or all of these. If a timer is used to regenerate the FS sensor, method 600 includes checking whether the threshold-length period has elapsed at 606. If the threshold-length period has not elapsed (e.g., "NO" at 606), method 600 proceeds to 608, where the regeneration circuit may remain enabled to continue regeneration, and the method ends. Method 600 may return to 606 to continue checking whether the threshold period has elapsed.If the threshold time period has elapsed (e.g., "YES" at 606), method 600 proceeds to 610, where the FS sensor regeneration may be terminated and the electrical circuit may be deactivated at 612. Further, the sensor electrodes may be cooled to, for example, the exhaust gas temperature. Method 600 proceeds to 614, where the FS sensor load and regeneration history may be updated and stored in memory. For example, a frequency of FS sensor regeneration and / or an average time period between sensor regenerations may be updated, and the method ends.

[0062] In some examples, the controller (e.g., controller 12 from Fig. 1) Additionally or alternatively, determine which of the positive and negative electrodes are electrically coupled. For example, only the electrodes in a single chamber may be electrically coupled. Accordingly, heating elements corresponding only to that single chamber may be turned on. In this way, heating elements of the sensor element may be operated individually to reduce power consumption during FS sensor element regenerations. In other embodiments, the FS sensor assembly may be rotated via a motor. This may adjust an amount of exhaust gas entering the chambers (e.g., more exhaust gas enters upstream chambers compared to downstream chambers).Thus, FS sensor assembly regeneration may include rotating the FS sensor assembly such that fully loaded chambers requiring regeneration may be rotated to a downstream position to reduce an amount of exhaust gas flowing into the fully loaded chambers.

[0063] The engine exhaust passage may include one or more FS sensors, which may be located upstream and / or downstream of the DPF, to determine a soot load on the DPF. If the FS sensor is located upstream of the DPF, a soot load on the sensor may be derived based on the change in resistance due to soot deposition at the plurality of electrodes of the FS sensor. 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 higher than a threshold for DPF regeneration, the controller may adjust the engine operating parameters to regenerate the DPF. In particular, in response to the conditions for regenerating the filter being met, a temperature of the filter (or near the filter) may be increased sufficiently to combust deposited soot.This may involve operating a heater coupled to the DPF or increasing the temperature of the engine exhaust gas (e.g. by running rich) flowing into the DPF.

[0064] Now, with reference to Fig. 7 shows an exemplary method 700 for determining DPF function based on the FS sensor regeneration time. At 702, the controller may calibrate to calculate the FS sensor regeneration time, t(i)_regen, which is the time measured from the end of the previous regeneration to the start of the current FS sensor regeneration. At 704, t(i)_regen is compared to t(i-1)_regen, which is the previously calibrated FS sensor regeneration time. From this, it may be inferred that the soot sensor may cycle through regeneration multiple times to establish a diagnostic for the DPF. If t(i)_regen is less than half the value of t(i - 1)-region, then at 708 it is indicated that the DPF is leaking and a signal related to the degradation of the DPF is initiated.Alternatively, or in addition to the above process, a diagnosis for the DPF may be established using other parameters such as exhaust gas temperature, engine speed / load, etc. The signal related to degradation may be initiated, for example, by a malfunction indicator lamp or a diagnostic code. Furthermore, method 700 includes adjusting engine operation based on the indication of leaks in the DPF at 710. Adjusting engine operation may include, for example, limiting engine speed at 712. In one example, in response to detecting leaks in the DPF, engine power and torque may be reduced. Reducing engine power and torque may reduce the amount of FS emissions in the exhaust.For example, adjusting engine operation may reduce the amount of fuel injected into a diesel engine under heavy load conditions, thereby reducing torque. Additionally or alternatively, in response to the detection of leaks in the DPF, EGR usage may be reduced. Additionally or alternatively, an engine warning indicator may appear on the instrument panel to indicate the maximum distance the vehicle can travel before the DPF service check.

[0065] A current regeneration time of less than half the previous regeneration time may indicate that the electrical circuit has significantly less time to reach the R_regen threshold, thus requiring a higher regeneration frequency. A higher regeneration frequency in the FS sensor may indicate that the exhaust gas contains a higher amount of particulate matter than detected in a normally functioning DPF.Accordingly, when the change in regeneration time in the soot sensor reaches a threshold t_regen at which the current regeneration time of the FS sensor is less than half of the previous regeneration time, DPF degradation or leakage is indicated, for example, via an indication to a vehicle operator and / or via the setting of a flag stored on non-volatile memory coupled to the processor, which can be sent to the diagnostic tool coupled to the processor. If the change in regeneration time of the soot sensor does not reach the threshold t_regen, no DPF leakage is indicated at 706. In this way, leaks in a particulate filter arranged upstream of the particulate matter sensor can be detected based on a rate of deposition of the particulate matter on the particulate matter sensor electrodes.

[0066] Now, with reference to Fig. 8, diagram 800 illustrates an exemplary relationship between the soot load of the FS sensor and the soot load of the particulate filter. Specifically, diagram 800 graphically illustrates the relationship between the regeneration of the FS sensor and the soot load of the DPF, and specifically how a regeneration of the FS sensor can indicate DPF degradation. The vertical markers t0, t1, t2, t3, t4, t5, and t6 identify key times in the operation and system of the FS sensor and DPF.

[0067] The first course from Fig.Figure 8 shows a soot load of the FS sensor. As previously described, FS is deposited, for example, via the positive and negative electrodes formed on a cylindrical substrate located in an internal device closer to a hole formed at the bottom of the internal device. As soot accumulates, a current measured at the electrodes begins to increase (or a resistance of the electrodes begins to increase). The controller may be able to determine a soot load (plot 802) based on the measured current / resistance. Therefore, the soot load has its lowest value at the bottom of the plots and increases in magnitude toward the top of the plot in the vertical direction. The horizontal direction represents time, and time increases from the left to the right side of the plot.The horizontal marker 806 represents the load at a threshold value for regeneration of the FS sensor in the upper representation. The representation 804 represents the soot load on the DPF and the horizontal marker 808 represents the soot load of the DPF at a threshold value in the second representation.

[0068] A regeneration cycle of the FS sensor is depicted between t0 and t1. At time t0, the FS sensor is in a relatively clean state, as measured by a low FS load (representation 802). A controller coupled to the FS sensor determines the soot load of the FS sensor based, for example, on the current / resistance measured at the sensor electrodes. If the controller determines that the soot load is low, it can send instructions to a regeneration circuit to stop applying heat so that a detection circuit can begin detecting a buildup of FS load. As the FS load on the sensor increases, soot accumulates in the space between the sensor electrodes.

[0069] Between t0 and t1, as FS continues to accumulate, the soot load (illustrated 802) increases accordingly, and further, the soot load at the DPF also increases (illustrated 804). In some examples, the soot load at the DPF may be based on a load on the FS sensor, for example, when the FS sensor is located upstream of the DPF.

[0070] At t1, the soot load on the FS sensor (representation 802) reaches a threshold load for regeneration of the FS sensor (marker 806). The threshold load may be a load at which the sensor requires regeneration. At t1, regeneration of the FS sensor may be initiated as discussed above. In short, the controller may close a switch in the electrical circuit to apply voltage to the heating elements, which may be formed, for example, along the inner surface of the center element. Furthermore, the FS sensor may not operate in FS collection mode, so the controller cannot apply voltage to the sensor electrodes.

[0071] Accordingly, the FS sensor may be regenerated between t1 and t2 by switching on the electrical regeneration circuit. At t2, the FS sensor may be cool enough and, for example, begin collecting soot and continue collecting between t2 and t3 (DPF regeneration cycle). During the time between t2 and t3, the soot load in the DPF continues to increase (illustration 804). At t3, the soot load on the DPF (illustration 804) reaches a threshold load for regenerating the DPF sensor (marker 808). Between t3 and t4, the DPF may be regenerated to burn off the soot deposited on the DPF. Furthermore, at t4, the FS sensor regeneration frequency may be compared to a previously estimated FS sensor regeneration frequency. If the regeneration frequency of the FS sensor remains the same compared to previous cycles, it can be determined that the DPF is not leaking.In this way, the condition of the DPF can be monitored and leaks can be detected based on the output of the FS sensor.

[0072] A different DPF cycle is shown between t5 and t6. Here, the soot load on the DPF gradually increases between t5 and t6 (Figure 804). During this time, the soot load on the FS sensor (Figure 802) can be monitored. Figure 802 shows that the FS sensor undergoes several regeneration cycles as described above. However, the regeneration frequency of the FS sensor has almost doubled (Figure 802). The higher regeneration frequency in the FS sensor may indicate that the outflowing exhaust gas contains a higher amount of particulate matter than detected in a normally functioning DPF. Accordingly, a DPF leak may be indicated at t6.

[0073] This allows for a more accurate measurement of the particulate matter load in the exhaust gas and thus the soot load in the DPF. This increases the efficiency of filter regeneration operations. Furthermore, enabling more accurate diagnosis of an exhaust DPF can increase compliance with exhaust emission regulations. Therefore, this reduces the high warranty costs for replacing functioning particulate filters and extends the service life of exhaust components.

[0074] In this way, the sensor element can be shielded by one or more cylindrical protective tubes and circular plates. Exhaust gases can enter the sensor assembly through perforations located near a lower end of the cylindrical protective tube. Thus, the exhaust gas can undergo changes in flow direction, which helps to reduce the flow rate. In addition, water droplets and large contaminants flow into the circular plate located in the cylindrical protective tube, which is located between the sensor element and the perforations. The exhaust gas flows through the chambers to the sensor element, and a dome is arranged outside the exhaust passage. The dome receives exhaust gas and distributes the exhaust gas to the chambers. Exhaust gas then flows back through the chambers towards the perforations. Thus, exhaust gas entering the cylindrical protective tube flows twice along a length of its chambers.In this way, by separating the holes from the sensor element with the circular plate, problems of uneven soot deposition due to the uniform current caused by the annular space can be prevented.

[0075] A technical effect of a more uniform flow of sample gases onto a particulate matter sensor can be achieved by reducing the exhaust gas flow velocity. By interrupting the exhaust gas flow path and reducing the velocity, the flow uniformity across the particulate matter sensor surface can be increased. Furthermore, by placing the sensor element under the dome, the exhaust gas is forced to pass the sensor element twice before being expelled from the cylindrical protective tube.

[0076] A particulate matter sensor assembly comprises a cylindrical assembly, an internal device disposed within an external device of the cylindrical assembly, having a radius less than a radius of the external device, and a sensor element located above an annular space proximate a dome located at an upper end of the external device. A first example of the sensor further includes where the annular space is a portion of an internal flow space of the external device located between the external device and the internal device. A second example of the sensor, optionally incorporating the first example, further includes where the internal flow space is divided into identical chambers via a plurality of rigid partition walls impermeable to exhaust flow, and wherein each of the chambers includes a perforation for receiving and expelling exhaust gas.A third example of the sensor, optionally including the first and second examples, further includes where the dome is fluidly connected to the internal flow space of each of the chambers. A fourth example of the sensor, optionally including one or more of the first to third examples, further includes where the dome extends outside the exhaust duct of an exhaust passage. A fifth example of the sensor, optionally including one or more of the first to fourth examples, further includes where the internal device prevents large particles and water droplets from flowing to the sensing element. A sixth example of the sensor, optionally including one or more of the first to fifth examples, further includes where the external device comprises a plurality of perforations located on a common plane facing radially outward directions.A seventh example of the sensor, optionally including one or more of the first to sixth examples, further includes where the indoor device is completely spaced from and suspended within the outdoor device, and wherein the outdoor device has a cylindrical shape and the indoor device is circular.

[0077] A particulate matter sensor includes a pair of electrodes formed on a first surface of a sensor element, a heating element formed on a second surface of the sensor element, the second surface opposite the first surface, and a plurality of partition walls dividing an internal flow space of the particulate matter sensor into equal-sized chambers. A first example of the sensor further includes where each of the partition walls is in surface-dividing contact with the second surface of the sensor element, and wherein the first surface of the sensor element is exposed to the internal flow space. A second example of the sensor, optionally including the first example, further includes where the partition walls are impermeable to the exhaust gas flow and where the number of partition walls is eight.A third example of the sensor, optionally including the first and / or second example, further includes where each of the partitions corresponds to a positive or negative electrode of the sensing element, and wherein adjacent partitions comprise oppositely charged electrodes. A fourth example of the sensor, optionally including one or more of the first to third examples, further includes where the partitions, in a plan view, form a shape of an eight-pointed star symmetrical about a center of the particulate matter sensor. A fifth example of the sensor, optionally including one or more of the first to fourth examples, further includes where each of the chambers comprises at least one perforation fluidly coupling the chamber to an exhaust passage.A sixth example of the sensor, optionally including one or more of the first to fifth examples, further includes where the electrodes comprise linear positive and linear negative electrodes, and wherein the positive and negative electrodes are located on different partitions. A seventh example of the sensor, optionally including one or more of the first to sixth examples, further includes where the partitions are located in the outdoor device, the partitions are physically coupled to the outdoor device along an outer edge while being physically coupled to each other along an inner edge, and where the indoor device is installed in the outdoor device via the partitions.

[0078] A method includes flowing exhaust gas from downstream of a particulate filter through perforations adjacent a lower end of an outdoor device into an exhaust sensor assembly in a radially inward direction toward a center of the outdoor device, the perforations fluidly coupling chambers of the outdoor device to an exhaust passage, and directing the exhaust gas toward an indoor device located between the perforations and a sensor element, where the exhaust gas flows in a direction perpendicular to the exhaust flow in the exhaust passage. A first example of the method further includes flowing the exhaust gas through an annular space between the indoor device and the outdoor device toward the sensor element.A second example of the method, optionally including the first example, further includes where the sensor element is adjacent to a dome of the exhaust gas sensor assembly disposed outside the exhaust passage, and where the dome is hollow and configured to direct exhaust gas to the chambers after the exhaust gas has flowed over the sensor element, wherein the exhaust gas flows in a direction perpendicular to the exhaust gas flow in the exhaust passage. A third example of the method, optionally including the first and / or second example, further includes where the exhaust gas sensor assembly does not include any inlets or additional outlets other than the perforations.

[0079] 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 executed by the control system, including the controller, 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. Accordingly, various illustrated acts, operations, and / or functions may be performed in the illustrated order, in parallel, or in some cases, may be omitted.Likewise, the processing order is not required to achieve the features and advantages of the embodiments described herein, but rather is provided for ease of illustration and description. One or more of the illustrated acts, operations, and / or functions may be performed repeatedly depending on the particular strategy employed. Further, the described acts, operations, and / or functions may graphically represent code to be programmed on non-transitory memory of the computer-readable storage medium in the engine control system, wherein the described acts are performed by executing the instructions in a system including the various engine hardware components in combination with the electronic controller.

[0080] It is understood that the configurations and routines disclosed herein are exemplary in nature, and these specific embodiments are not to be considered limiting, as numerous variations are possible. For example, the above technique may be applied to V-6, I-4, I-6, V-12, horizontally opposed 4-cylinder, and other engine types. 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.

[0081] The following claims particularly set forth certain combinations and subcombinations that are considered novel and non-obvious. These claims may refer to "a" element or "a first" element, or the equivalent thereof. Such claims are to be construed as including the inclusion of one or more such elements and neither requiring nor excluding two or more such elements. Further combinations and subcombinations of the disclosed features, functions, elements, and / or properties may be claimed by amending the present claims or by filing new claims in this or a related application. Such claims, whether broader, narrower, the same, or different in scope than the original claims, are also to be considered included within the subject matter of the present disclosure. QUOTES CONTAINED IN THE DESCRIPTION

[0082] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature • US 2012 / 0 085 146 A1 • US 8 310 249 B2 • DE 20 2014 005 420 U1 • US 2015 / 0 355 067 A1

Claims

[1] Method comprising: Flowing exhaust gas from downstream of a particulate filter via perforations (244) directed adjacent a lower end of an external device (216) into an exhaust gas sensor assembly (202) in a direction radially inward toward a center of the external device (216), the perforations (244) fluidly coupling chambers (209) of the external device (216) to an exhaust passage (210); Directing the exhaust gas toward an internal device (218) located between the perforations (244) and a sensor element (234) where the exhaust gas flows in a direction perpendicular to the exhaust gas flow in the exhaust passage (210); Directing the exhaust gas past the interior device (218), over the sensor element (234), and into a dome (246) of the exhaust sensor assembly (202); and then returning the exhaust gas from the dome (246) to the sensor element (234). [2] The method of claim 1, wherein directing the exhaust gas toward the sensor element (234) includes flowing the exhaust gas through an annular space (224) between the indoor device (218) and the outdoor device (216). [3] The method of claim 1, wherein the sensor element (234) is adjacent to the dome (246) of the exhaust gas sensor assembly (202) disposed outside the exhaust passage (210), and where the dome (246) is hollow and configured to direct exhaust gas to the chambers (209) after the exhaust gas has flowed over the sensor element (234), the exhaust gas flowing in the direction perpendicular to the exhaust gas flow in the exhaust passage (210); and wherein a pair of electrodes (236) are formed on a first surface of the sensor element (234) and a heating element (238) is formed on a second surface of the sensor element (234). [4] The method of claim 1, wherein the exhaust gas sensor assembly (202) does not include any inlets or additional outlets other than the perforations (244). [5] The method of claim 1, further comprising, after directing the exhaust gas back to the sensor element (234), directing the exhaust gas from the exhaust sensor assembly (202) into the exhaust passage (210). [6] The method of claim 1, wherein the exhaust gas leaves particles on the substrate of the sensor element (234) before being directed into the dome (246). [7] The method of claim 6, wherein the exhaust gas leaves further particles on the substrate of the sensor element (234) when the exhaust gas is directed from the dome (246) back to the sensor element (234). [8] Method comprising: Flowing exhaust gas from downstream of a particulate filter via perforations (244) directed adjacent a lower end of an external device (216) into an exhaust gas sensor assembly (202) in a direction radially inward toward a center of the external device (216), the perforations (244) fluidly coupling chambers (209) of the external device (216) to an exhaust passage (210), and directing the exhaust gas towards an internal device (218) located between the perforations (244) and a sensor element (234), where the exhaust gas flows in a direction perpendicular to the exhaust gas flow in the exhaust passage (210), wherein the sensor element (234) is adjacent to a dome (246) of the exhaust gas sensor assembly (202) disposed outside the exhaust passage (210), and wherein the dome (246) is hollow and configured to direct exhaust gas to the chambers (209) after the exhaust gas has flowed over the sensor element (234), the exhaust gas flowing in a direction perpendicular to the exhaust gas flow in the exhaust passage (210); and wherein a pair of electrodes (236) are formed on a first surface of the sensor element (234) and a heating element (238) is formed on a second surface of the sensor element (234). [9] The method of claim 8, wherein the dome (246) is a hollow hemisphere. [10] The method of claim 8, further comprising flowing the exhaust gas through an annular space (224) between the indoor device (218) and the outdoor device (216) toward the sensor element (234). [11] The method of claim 10, wherein flowing the exhaust gas to the sensor element (234) includes flowing the exhaust gas upward.

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