METHOD FOR DETECTING FINE PARTICULATES IN EXHAUST GAS

Abstract

Method comprising: Flowing exhaust gas from downstream of a particulate filter (102) into an exhaust sensor assembly (202) via a flow tube (206) disposed between an indoor and outdoor device (218, 216) in a direction opposite to the flow of exhaust gas in an exhaust pipe (210), the flow tube (206) being connected to downstream surfaces of the indoor and outdoor devices (218, 216); and Directing the exhaust gas towards an internal chamber (242) in the internal device (218) before the exhaust gas flows to an annular space arranged between the internal and external devices (218, 216), wherein the exhaust gas flows in a direction orthogonal to the flow of the exhaust gas in the exhaust pipe (210).

Description

Area

[0001] The present application relates to the capture of particulate matter in an exhaust system. General state of the art / brief description

[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 the accumulation of particulate matter (PPM) 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 particulate matter loading at the particulate filter and to diagnose the 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 pipe and housed within a cylindrical protective tube. The FS sensor additionally includes a sensing element positioned closer to a center of the exhaust pipe so that the sensor output more accurately reflects an average soot concentration in the exhaust pipe. 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 arrangements. 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 arrangements, an additional protective layer may be required to protect the soot sensor element from direct impingement by 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 determine 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 pipe, as shown by Paterson in US 8 310 249 B2, water condensation at the bottom of the exhaust pipe may overflow into the sensor element, thereby contaminating the sensor element. Such contamination of the sensor element may lead to sensor output fluctuations, thereby reducing the accuracy of the particulate load estimation on the particulate filter (see also US 2016 / 0 131 013 A1).

[0006] To at least partially address the problems, the invention proposes a method according to claim 1. Advantageous embodiments of the invention are subject of the dependent claims. Therein, a particulate matter sensor assembly comprises a spherical assembly, an inner device positioned within an outer device of the spherical assembly, offset from a geometric center of the outer device, and a sensor element located on an outer surface of the inner device, proximal to a narrowest passage between the spherical assembly and the elongated

[0007] Chamber. In this way, problems related to water droplets and larger contaminants impinging on the sensor element and causing sensor output fluctuations can be reduced by separating the sensor element from an internal chamber of the internal device.

[0008] An exhaust particulate matter sensor assembly is disposed downstream of an exhaust particulate filter in an exhaust pipe. The particulate matter sensor may include a spherical assembly including a flow tube mounted at a lower, downstream end of the assembly relative to a direction of exhaust flow and a sensor element positioned closer to an upper end of the assembly.

[0009] In particular, the spherical assembly includes hollow spherical misaligned outer and inner devices separated by a gap and / or annular space. A support rod may be attached to the upper end of the assembly and connect the assembly to the top of an exhaust pipe.

[0010] The flow tube fluidly connects the indoor device to the exhaust passage. Thus, exhaust gas flows through the elongated chamber before flowing through the annular space located between the outdoor and indoor devices. The indoor device is located asymmetrically within the spherical assembly, with geometric centers of the elongated chamber and spherical assembly offset. Thus, a largest diameter of the elongated chamber corresponds to a narrowest gap of the annular space. The sensing element is positioned on an outer surface of the indoor device along its largest diameter. As a result, exhaust gas flows annularly through the narrowest passage and deposits particulates on the sensing element before flowing through an outlet of the outdoor device to the exhaust passage.

[0011] This improves the functioning 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 associated with replacing functioning particulate filters. Exhaust gas can exit the sensor through the outlet located at the bottom of the assembly. The asymmetric design of the outer and inner devices eliminates the manufacturing process for specific sensor alignment during assembly and improves sensor repeatability.

[0012] 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 overcome disadvantages noted above or in any part of this disclosure. Short description of the drawings Fig. Figure 1 shows a schematic diagram of an engine and an associated particulate matter (PM) sensor positioned in an exhaust stream. Fig. Figure 2 shows a schematic diagram of the FS sensor with a spherical assembly comprising a flow tube and a sensing element mounted via a support rod within an exhaust pipe. Fig. Figure 3 shows a schematic diagram of the FS sensor showing exhaust gas flowing into the FS sensor via the flow tube attached to a bottom of the spherical assembly. Fig. Figure 4 shows an exemplary configuration of circular interdigitated electrodes formed on a first surface of the sensor element. Fig. 2-4 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 positioned within the internal device of the spherical assembly of the FS sensor. Fig. 6 is a flowchart illustrating an exemplary method for regenerating the sensor electrodes of the FS sensor. Fig. Figure 7 shows a flowchart illustrating an exemplary method for detecting leaks in a particulate filter positioned 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 positioned upstream of the FS sensor. Detailed description

[0013] The following description relates to a method for detecting 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 placed in an exhaust passage of the engine system. The FS sensor may include a spherical assembly having an attached flow tube and a support rod attached to diametrically opposite ends of the spherical assembly. The spherical assembly may be attached to a bottom of the exhaust passage by means of the support rod. In particular, the spherical assembly includes a spherical inner device positioned within a spherical outer device and separated by a gap, and the flow tube includes an inner tube positioned within an outer tube and separated by a space, as shown in Fig. 2. Furthermore, a cylindrical spherical element may be positioned in the inner device and may exhaust gas by means of a flow tube and holes formed on the inner device, as shown in Fig. 3, towards the sensor element. The sensor element may include interdigitated 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, opposite surface, 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 collect particles in the exhaust gas via the electrodes of the sensor element. Furthermore, the controller can detect the FS sensor ( Fig. 6) periodically clean to enable continued FS monitoring. Furthermore, the controller may be configured 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.

[0014] Fig. 1-4 show example arrangements with relative positioning of the various components. When shown directly touching or directly connected to one another, such elements may be referred to as directly touching or directly connected, 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 positioned 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 relative to each other. Thus, elements shown above other elements are, in one example, positioned 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).

[0015] Fig. 1 shows a schematic illustration 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 connected to the engine intake manifold 44 via an intake passage 42. The engine outlet 25 includes an exhaust manifold 48, which ultimately leads to an exhaust passage 35 that directs exhaust gas to the atmosphere. The throttle 62 may be located 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.

[0016] 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, a lean NOx trap, an SCR catalyst, etc. The engine outlet 25 may further include a diesel particulate filter (DPF) 102 that temporarily filters particulate matter from incoming gases positioned 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 to 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 electrodes of the FS sensor. A schematic view 200 of the FS sensor 106 is shown in FIG. Fig. 2, as described in more detail below.

[0017] The vehicle system 6 may further include a 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 connected 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 various 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 connected to the sensor electrodes to heat the sensor electrodes. In this way, the sensor electrodes are heated to burn off soot particles that have deposited on the surface of the sensor electrodes.Example routines are given here in relation to the . Fig. 5-7 described.

[0018] 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 PSSensor 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 (such as the one shown in Fig. 1) connected to a diesel particulate filter (such as the DPF 102 shown in Fig. 1) is upstream or downstream.

[0019] An axis system 290 is shown, comprising 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.

[0020] In the schematic view 200, the FS sensor assembly 202 is disposed within the exhaust passage 210, with exhaust gases flowing (in a horizontal direction 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 mounted within the exhaust passage 210 via a support rod 208. Here, the FS sensor assembly 202 is spherical in shape. In another example, the assembly may include a hollow elliptical structure positioned within the exhaust passage 210. As shown, the FS sensor assembly 204 and the support rod 208 are symmetrical about the y-axis.

[0021] The support rod 208 may extend along the y-axis in a direction orthogonal to the direction of the exhaust flow 258. Further, the support rod 208 may include an upper end 260 and a lower end 270. A portion of the upper end 260 may be connected to a top surface 212 of the exhaust passage 210 (and not connected to a bottom surface 214 of the exhaust passage 210, for example). As one example, the portion of the upper end 260 of the support rod 208 that extends through the top surface 212 of the exhaust passage 210 may be much smaller than the portion 254 of the support rod 208 that remains within the exhaust passage 210. The upper end 260 of the support rod 208 may be mounted within the top surface 212 of the exhaust passage 210 in a variety of ways. For example, the upper end 260 of the support rod 208 may be inserted, screwed, or held to the top 212 via additional screws (not shown).The upper end 260 is in sealing contact with the top surface 212. Accordingly, no exhaust gas 258 escapes through the intersection between the upper end 260 and the top surface 212 into an engine (e.g., the engine 10 in the embodiment of FIG. Fig. 1) or to the ambient air.

[0022] The lower end 270 of the support rod 208 may be connected to an upper portion 261 of the spherical assembly 204. Thus, the lower end 270 of the support rod 208 may be closed to prevent exhaust gas from escaping through the upper portion 261 of the spherical assembly 204. In particular, the spherical assembly 204 includes a hollow spherical outer device 216 (hereinafter referred to as outer device 216) and a hollow egg-shaped inner device 218 (hereinafter referred to as inner device 218) concentrically positioned within the outer device 216. The upper end 260 of the support rod 208 may be connected to an upper portion 261 of the outer device 216. As a result, the support rod 208 is fluidly connected to the external device 216, particularly at the opening formed in the upper portion 261 of the external device 216 and the lower end 270 of the support rod 208.It can be noted that the support rod 208 is not connected to the inner device 218, but is only connected to the outer device 216.

[0023] The outer device 216 is a spherical protective device with radius R1. However, the inner device 218 is an elongated protective device with a varying radius, where R2 indicates a largest radius of the inner device 218. Here, the inner device 218 is smaller than the outer device 216 (e.g., R2 <R1) und ein ringförmiger Spalt 224 und / oder ringförmiger Raum 224 befindet sich zwischen der Außenvorrichtung 216 und der Innenvorrichtung 218. Die Innenvorrichtung 218 ist asymmetrisch in der Außenvorrichtung 216 positioniert, sodass der ringförmige Spalt 224 zwischen der Außenvorrichtung 216 und der Innenvorrichtung 218 nicht einheitlich ist, wobei ein Spalt 226 einen engsten Abschnitt des ringförmigen Spalts 224 angibt. Hierin kann der Spalt 226 auch als engster Spalt 226 und / oder engster Raum 226 bezeichnet werden.In this way, the annular space 224 is not symmetrical, with a larger portion of its volume located near a bottom portion 262. The outer device 216 and the inner device 218 include offset centers C and C' along a common central axis Y-Y', which is perpendicular to the direction of exhaust flow (arrow 258) in the exhaust passage 210. However, the center C is located along a first horizontal axis, X-X', which is below a second horizontal axis, X''-X''', of the center C'. Thus, the center C' of the inner device 218 is closer to the top portion 261 than the center C of the outer device 216. Together, the inner device 218 and the outer device 216 form a spherical assembly 204 of the FS sensor assembly 202.

[0024] As one example, the length of the FS sensor assembly 202 and the radii R1 and R2 of the outer device 216 and inner device 218 of the spherical assembly 204 can be selected such that the spherical assembly 204 can be positioned closer to a center of the exhaust passage 210. In this way, by positioning the sensor assembly near the center of the exhaust passage 210, the average soot particle concentration in the exhaust passage 210 can be adequately reflected in the sensor assembly. In one example, the X-X' axis also represents a central axis of the exhaust passage 210. Thus, the sensitivity of the FS sensor assembly 202 can be increased and the sensor can be made 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, improves exhaust emissions and extends the service life of exhaust components.

[0025] The inner device 218 is mounted within and spaced from the inner surfaces of the outer device 216 via a flow tube 206 and a spacer 209 and / or a support 209. The spacer 209 is physically connected to the outer device 216 and inner device 218 at opposite outer ends. The spacer 209 is rigid and impervious to (e.g., does not permit) exhaust gas. Unlike the spacer 209, which is located adjacent an upstream surface 220 of the outer device 216, a flow tube 206 is located on a downstream surface 222 of the spherical assembly 204. As shown, in the embodiment of Fig. 2, the upstream surface 220 is located to the left of the Y-Y' axis, and the downstream surface 222 is located to the right of the Y-Y' axis. The flow tube 206 is physically connected to the outer device 216 and the inner device 218 at opposite outer ends. Further, the flow tube 206 is hollow and configured to allow exhaust gas to flow therethrough to an inner chamber 242 of the inner device 218. Specifically, exhaust gas flows directly from the exhaust passage 210 via the flow tube 206 to the inner chamber 242 without flowing through the annular space 224. In one example, the flow tube 206 is the only inlet for exhaust gas to enter the spherical assembly 204 from the exhaust passage 210. In this manner, both the flow tube 206 and the spacer 209 firmly connect the inner device 218 to the inner surfaces of the outer device 216, with only the flow tube 206 being configured to receive exhaust gas into the inner device 218.

[0026] During a cold start of the vehicle, the exhaust gas may not be warm enough to convert water in the exhaust passage to vapor (gaseous state), and therefore, water may sometimes remain in a liquid state and collect at the bottom 214 of the exhaust passage 210. By attaching the flow tube 206 to the downstream surface 222 of the external device 218, the sensor may be protected from water condensing and accumulating at the bottom of the exhaust passage by allowing a pulse of large particles and / or water droplets to flow through the flow tube 206. This may prevent and / or reduce the entry of large particles into the internal device 218.

[0027] An indoor device outlet 244 fluidly connects the interior chamber 242 of the indoor device 218 to the annular space 224. Except for the indoor device outlet 244 and the flow tube 206, the indoor device 218 is completely sealed, with surfaces impermeable to exhaust gas flow. The indoor device outlet 244 is positioned along an upper surface of the indoor device 218 near the upper portion 261. An outdoor device outlet 246 is located on a lower surface of the outdoor device 216 near the lower portion 262. The indoor device outlet 244 and the outdoor device outlet 246 are both located on the Y-Y' axis. However, the outdoor device outlet 246 is located in a lower half of the outdoor device below the X-X' axis, and the indoor device outlet 244 is located in an upper half of the outdoor device above the X-X' axis. In this way, exhaust gas flows through a full height (e.g.Diameter) of the annular space 224 along the Y-Y' axis before flowing through the outdoor device outlet 246. In one example, the outdoor device outlet 246 includes a diameter that is larger than a diameter of the indoor device outlet 244. Both the outdoor device outlet 246 and the indoor device outlet 244 may be circular, oblong, or have other shapes designed to allow exhaust gas to flow therethrough.

[0028] The exhaust passage 210 is confined by the spherical assembly 204, resulting in a decrease in static pressure in portions of the exhaust passage 210 adjacent to the spherical assembly 204 along the Y-Y' axis. This may create a partial vacuum that may flow through the external device outlet 246, thereby providing a vacuum in the annular space 224. The vacuum may draw some exhaust through the flow tube 206 and into the internal chamber 242. However, the vacuum may not be sufficient to reverse the flow direction of large particles and / or water droplets, as discussed below. Fig. 3 is described.

[0029] Thus, the outer device 216 may be fabricated as a hollow spherical device with recesses formed on the lower portion 262 and the downstream surface 222. In one example, the recesses are circular. The flow tube 206 may be fabricated as a hollow cylinder and inserted into a recess of the downstream surface 222 and a recess of the inner device 218. Alternatively, the support rod 208 and the spacer 209 are solid tubes used to support the spherical assembly 204 and the inner device 218, respectively. As described above, the support rod 208 may be sized to extend the spherical assembly 204 toward a center of the exhaust passage 210. Alternatively, the spacer 209 and the flow tube 206 may be sized to position the inner device 218 asymmetrically within the outer device 216.

[0030] Similar to the outer device, the inner device 218 may be fabricated as a hollow, elongated device with recesses formed near the upper portion 261 and near the downstream surface 222 corresponding to a location of the flow tube 206. The radius of the inner device 218 is non-uniform, with a largest radius along the X''-X''' axis and a smallest radius along the Y-Y' axis. Near the downstream surface 222, the recess may receive exhaust gas into the interior chamber 242 of the inner device 218. The recess near the upper portion 261 may expel exhaust gas into the annular space between the outer device 216 and the inner device 218. In this way, the inner device 218 is firmly suspended within the outer device 216. Additionally, the internal device 218 may include a sensor element 234 connected to an outer surface of the internal device 218.

[0031] The sensor element 234 may be located along a largest diameter (e.g., or radius R2). As one example, the sensor element 234 is annular and wraps around a complete circumference of the internal device 218 along the X''-X''' axis. Thus, the internal device 218 may be forcibly pushed into the sensor element 234 to prevent slippage and / or separation. The sensor element 234 is located downstream of the narrowest gap 226 of the annular space 224 with respect to a direction of exhaust flow.

[0032] The sensor element 234 includes a substrate 240 having interdigitated electrodes 236 formed on a first surface and a heating element 238 formed on a second, opposite surface. In other words, the interdigitated electrodes 236 and the heating element 238 are formed on two opposite sides of the substrate 240, thereby being separated by a thickness of the substrate 240. Accordingly, the sensor element 234 may be a circular element to utilize the elongated shape of the internal device 218. However, the sensor element 234 may be rectangular, square, triangular, or the like without departing from the scope of the invention. For a circular element 234, the interdigitated electrodes 236 may additionally be circular, so that there is increased surface area coverage of the electrodes located on the circular sensor element 234.Alternatively, various other geometries may be possible without departing from the scope of the disclosure. One exemplary geometry includes an interdigitated "comb electrode structure." The soot particles in the exhaust may be trapped between the interdigitated electrodes as described with reference to FIG. Fig. 4. The sensor element 234 can be positioned outside the inner device 218 such that the interdigitated electrodes 236 face inner surfaces of the outer device 216, while the heating element 238 formed on the opposite surface is pressed against an outer surface of the inner device 218. By positioning the sensor element 234 on the outside of the inner device 218, it is separated from the flow tube 206 and thus can reduce problems in which water droplets and larger contaminants impinge on the sensor element and thereby cause fluctuations in the sensor output. The description of the electrical circuit and the composition of the sensor element and the substrate is Fig. 4 common.

[0033] Now, with reference to Fig. 3 is a schematic view 300 illustrating the exhaust flow through the FS sensor assembly 202. In particular, view 300 illustrates exhaust flowing into the FS sensor assembly 202 via flow tube 206, which is located between curved inner and outer surfaces of the outer device 216 and inner device 218, respectively. Here, the flow tube 206 is configured to receive exhaust from the exhaust passage 210 and direct the exhaust into the inner chamber 242 formed in the inner device 218. Directing the exhaust into the inner chamber 242 involves reversing an exhaust flow as indicated by arrow 279 and then through the flow tube 206 and into the inner chamber 242 as indicated by arrow 280. In particular, the exhaust gas enters the flow tube 206 in a direction oblique to and / or opposite to the direction of the exhaust gas flow (indicated by arrow 258) within the exhaust passage 210.Thus, larger or heavier contaminants and / or water droplets 274 (such as particles having a size or weight exceeding the threshold) in the exhaust gas may gravitate toward the bottom 214 of the exhaust passage 210 and have momentum too great to turn around and enter the flow tube 206.

[0034] As mentioned above with reference to Fig. 2, the internal device 218 is sealed, except for the recess corresponding to the flow tube 206 and the internal device outlet 244. Therefore, the exhaust gas in the internal chamber 242 is forced to move toward the upper portion 261 of the spherical assembly 204. In particular, the exhaust gas flows in a direction perpendicular (as indicated by arrow 281) to the direction of exhaust gas flow in the exhaust passage 210 (as indicated by arrows 258). It will be understood that the exhaust arrow 281 may also swirl and / or flow annularly within the internal chamber 242, but its general flow direction is parallel to the arrow 281 shown in Fig. 3. The exhaust gas then flows outwardly in an annular manner, as indicated by arrows 282, into the annular space 224 via the outlet 244 of the internal device, as indicated by arrows 281. In the schematic view 300, the annular space 224 is a ring formed between the internal device 218 and the external device 216, and thus the annular space 224 can function as a flow chamber between the internal device 218 and the external device 216. The exhaust gas in the annular space 224 flows around the internal device 218 in a downward direction toward the lower portion 262 of the spherical assembly 204.

[0035] In particular, the exhaust gas flows annularly downward within the annular space 224 in a direction orthogonal to arrows 258 and the opposite arrow 281 (as indicated by arrow 283). The exhaust gas flows through the narrowest gap 226 between the outdoor device 216 and indoor device 218 before passing the sensor element 234. The positioning of the outdoor device outlet 244 with respect to the sensor element 234 has several advantages. First, the outdoor device outlet 244 is positioned along a most restricted portion of the exhaust passage 210, thereby promoting the illustrated exhaust flow. Second, the sensor element 234 is positioned above the outdoor device outlet 244 such that exhaust gas flowing toward the outdoor device outlet 244 flows through at least a horizontal plane of the sensor element 234 (e.g., along the X''-X''' axis).As a result, the sensor element 234 can accurately estimate FS in the exhaust stream while receiving uniform FS deposition due to the annular downward direction of the exhaust stream in the annular space 224.

[0036] In one example, the annular space 224 adjacent to the internal device 218, where the narrowest gap 226 corresponds to a venturi throat, is venturi-shaped. Thus, exhaust flow exiting the internal device outlet 244 (indicated by arrows 282) may have a uniform exhaust mass flow through the annular space 224. In other words, the exhaust distribution across an area of the sensor element 234 may be substantially uniform (as shown by arrows 283), with a relationship between the external device 216 and internal device 218 substantially preventing uneven exhaust flow across the sensor element. The exhaust is directed in a direction perpendicular to the horizontal plane of the sensor element 234 (which is, for example, along the X-axis).It should be understood that the exhaust gas is directed toward the first surface, which includes the electrode, rather than toward the second surface of the sensor element 234, which includes the heating element 238. This is because the heating element 238 is pressed against exterior surfaces of the interior device 218 and is not exposed to the annular space 224 like the electrodes 236. Soot particles in the exhaust gas are collected between the interdigitated electrodes 236 of the sensor element 234, as described above. Exhaust gas in the annular space 224 is then directed toward the exterior device outlet 246, where the exhaust gas flows out of the spherical assembly 204 and into the exhaust passage 210. Exhaust gas flowing through the outdoor device outlet 246 first flows in a direction perpendicular to the direction of exhaust flow in the exhaust passage 210 (arrows 258) before turning in a direction parallel to the arrows 258, as shown by the arrows 284.The exhaust gas leaving the spherical assembly 204 combines with exhaust gas in the exhaust passage, as indicated by arrows 258 and arrows 284.

[0037] In summary, due to a venturi shape of the exhaust passage adjacent to the spherical assembly, exhaust gas flows past the outdoor device outlet. The exhaust gas then flows through the flow tube in a direction oblique to and / or opposite to its original flow and enters an interior chamber of the indoor device. The exhaust gas in the interior chamber is then directed toward a portion of the annular space located near the upper portion of the spherical assembly. The exhaust gas flows annularly, in a downward direction through the annular space. The exhaust gas flows through at least one plane of the sensing element, if not, flows over the sensing element before flowing into a region of the annular space below the indoor device. Thus, the sensing element detects FS of portions of the exhaust gas before the exhaust gas can exit the spherical assembly via the outdoor device outlet 246.

[0038] Thus, an exemplary particulate matter sensor includes a pair of interdigitated electrodes formed on a first surface of a cylindrical sensor element, a heating element formed on a second surface of the cylindrical sensor element, the second surface being opposite the first surface, and a flow tube and spacer suspending an inner device within an outer device of a spherical assembly, the inner device being spaced completely away from the outer device via an annular space. Additionally or alternatively, the second surface of the cylindrical sensor element may be pressed against an outer surface of the inner device, and the first surface of the sensor element is exposed to the annular space.Additionally or alternatively, the flow tube is configured to direct exhaust gas downstream of the spherical assembly to an internal chamber positioned in the indoor device, and wherein the spacer is impermeable to exhaust gas flow. Additionally or alternatively, the spherical assembly is mounted in an exhaust passage via a support rod extending from a top of the exhaust passage along a vertical axis. Additionally or alternatively, the indoor device is elongated and the outdoor device is spherical, and wherein a center of the indoor device is offset from a center of the outdoor device. Additionally or alternatively, the sensing element is located around a largest circumference of the indoor device, downstream of a narrowest gap between the outdoor device and indoor device.Additionally or alternatively, the spherical assembly defines an exhaust passage forming a venturi throat at an outdoor device outlet of the outdoor device. Additionally or alternatively, the outdoor device and indoor device do not include any inlet or outlets other than the flow tube, the indoor device outlet, and the outdoor device outlet.

[0039] 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. In particular, circular interdigitated electrodes formed on a circular substrate 240 are shown. Since the protection assembly has a spherical shape, it may be advantageous to include a circular substrate for the sensor element to increase the surface area available for soot particle adsorption. However, various other geometries of the substrate and electrode configurations may be possible without departing from the scope of the invention. Some example configurations include rectangular or square substrates with interdigitated comb electrodes.

[0040] In view 400, the substrate 240 of the sensor element 234 is circular with radius R3, which is less than R1 and greater than R2 of the outer device 216 and inner device 218 of Fig. 2. 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%). The radius R3 of the circular substrate 240 may be determined based on the radius R2 of the internal device 218.

[0041] The sensor electrode 236 includes a pair of circular, interdigitated electrodes 406 and 408 formed on a surface of the sensor element 234. Here, the pair of planar, interdigitated electrodes 406 and 408 may form circular, interdigitated prongs, indicated by solid and dashed 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 interdigitated pair may be composed of the same material as the other electrode of the pair or a different material. For example, electrode 406 may be composed of the same material as electrode 408.In another example, electrode 406 and electrode 408 may be made of different materials. The spacing between the circular "prongs" of the two electrodes may typically be in the range of 30 micrometers to 50 micrometers, with the linewidth of each individual "prong" being approximately the same, although the latter may be excluded.

[0042] Electrodes 406 and 408 may be connected to an electrical circuit 414 via electrical connections. Electrode 408 of sensor element 234 is connected to a positive terminal of a voltage source 416 of electrical circuit 414 via connecting wire 412. Thus, electrode 408 may be referred to as a positive electrode. Likewise, electrode 406 of sensor element 234 is connected to a measuring device 418 via a connecting wire 410 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 duct 210 (e.g., <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. As such, the measuring device 418 can be any device capable of reading a change in resistance (or current) across the electrodes, such as a voltmeter (or an ammeter). As FS or soot particles become deposited 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 may 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 202.By monitoring the load on the sensor element 234, the exhaust soot load downstream of the DPF can be determined and thereby used to diagnose and monitor the condition and functionality of the DPF.

[0043] In view 400, the electrode 406 includes a plurality of linear prongs of equal diameter that wrap around the substrate 240. 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. Herein, the straight portion 420 may extend between edges (located, for example, at the perimeter) of the substrate 240. As an example, a length of a straight portion 420 may be slightly less than a height of the substrate along the y-axis. The electrode 406 may additionally include a plurality of individual curved portions 424 that begin at specific locations along the straight portion 420 in a clockwise direction along the surface of the substrate 240 and end at a distance from the straight portion 420.Herein, each curved section 424 corresponds to a major arc of a circle with a specific radius slightly larger than R3, with the center coinciding, for example, with the center of the substrate 240. Each curved section 424 of the electrode 406 is substantially identical. Additionally, the curved sections 424 are cascaded along the height of the substrate 234 in the direction of gravity 299.

[0044] Similar to the negative electrode 406, the electrode 408 may include a plurality of circular prongs that are substantially equal in diameter. The electrode 408 (synonymously referred to as the positive electrode) includes a substantially straight portion 422 that connects the electrode 408 to the connecting wire 412. Here, the straight portion 422 may be parallel to the straight portion 420 of the negative electrode 406 and may extend between upper and lower edges of the substrate 240. As an example, a length of the straight portion 422 of the positive electrode 408 may be equal to, less than, or greater than the length of the straight portion 420 of the negative electrode 406.The positive electrode 408 may additionally include a plurality of individual curved sections 426 that begin at specific locations along the straight section 422 in a counterclockwise direction along the surface of the substrate 240 (away from the straight section 420 of the negative electrode 406) and end at a distance from the straight section 420.

[0045] In one example, the spacing w between the negative electrodes may be equal to the spacing w' between the positive electrodes. In another example, the spacing w may be different from the spacing w'. As previously mentioned, various geometries of the interdigitated electrodes may be possible. A spacing x between the negative 406 and positive 408 is substantially constant between each iteration of the bent portions 424 and 426. In one example, when sufficient FS accumulates and spans the entire spacing, x, the negative and positive electrodes are then electrically connected, as described below.

[0046] 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). In particular, the particulates in the exhaust stream may accumulate over interdigitated electrodes formed on a circular surface of a cylindrical substrate and positioned within a spherical assembly of the FS sensor. The spherical assembly includes an elongated inner device positioned within a spherical outer device and separated by a gap. The spherical assembly also includes a flow tube attached to the downstream surface to direct exhaust gas into and out of the spherical assembly.

[0047] 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.

[0048] 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.

[0049] 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 guided into an FS sensor via a flow tube. Here, the flow tube is a cylindrical tube located between the curved surfaces of the indoor device and the outdoor device. As explained above, the flow tube and a spacer mount the indoor device within the outdoor device. Unlike the spacer, the flow tube is designed to receive exhaust gas from the exhaust passage and guide it to the indoor device. The direction of the exhaust gas flow into the flow tube is, for example, opposite to the direction of the exhaust gas flow in the exhaust pipe.

[0050] 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, exhaust gas flows from the interior chamber of the indoor device into the annular space via an interior device outlet located near the top portion of the outdoor device. Thus, exhaust gas is forced to flow through a majority of a height of the interior chamber before flowing to the annular space.

[0051] Method 500 proceeds to 508. At 508, method 500 includes flowing exhaust gas through the annular space in a downward annular direction through a plane of the sensor element located on an exterior surface of the indoor device. The sensor element is physically coupled around the circumference corresponding to the largest diameter of the indoor device. Thus, the circumference of the sensor element is correspondingly larger than the largest circumference of the indoor device. As described above, the heating element of the sensor element is pressed against an exterior surface of the indoor device, and the electrodes are exposed to the exhaust gas in the annular space. Method 500 proceeds to 510.

[0052] At 510, method 500 includes collecting particles between circular, interdigitated electrodes formed on the sensor element. Specifically, at 510, particles in the annular space are directed toward the electrodes of the sensor element, and the particles are deposited over the electrodes. The direction of exhaust flow into the annular space is perpendicular to the direction of exhaust flow in the exhaust passage. As previously described, the sensor element, including the interdigitated electrodes, is disposed over the center C of the outdoor device. The positive electrodes are connected to the positive terminal of a power supply, and the negative electrodes are connected to a sensing device and then to the negative terminal of the power supply.When the controller applies a voltage to the sensor electrodes, particles in the annular space may experience a strong electric field, allowing them to accumulate between the electrodes. Additionally, a stress 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 stress on the sensor electrodes based on the current measured on the electrodes. Method 500 then proceeds to 512.

[0053] At 512, method 500 includes directing exhaust through the outdoor device outlet to the exhaust passage in a direction orthogonal to the direction of exhaust flow in the exhaust conduit. Exhaust flow through the outdoor device outlet may be promoted via a lower static pressure adjacent to the outdoor device outlet due to a restriction of the exhaust passage adjacent to the spherical assembly. Method 500 then proceeds to 514.

[0054] 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.

[0055] 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.

[0056] Thus, an example method may include flowing exhaust gas from below a particulate filter into an exhaust sensor assembly via a flow tube positioned between indoor and outdoor devices in a direction opposite to the flow of exhaust gas in an exhaust pipe, the flow tube being connected to downstream surfaces of the indoor and outdoor devices. The example method may further include directing the exhaust gas toward an interior chamber in the indoor device before the exhaust gas flows to an annular space located between the indoor and outdoor devices, the exhaust gas flowing in a direction orthogonal to the flow of exhaust gas in the exhaust pipe. Additionally or alternatively, the method may further include flowing the exhaust gas in the annular space via a sensor element connected to a surface of the indoor device outside the interior chamber.Additionally or alternatively, the method may further include the flow tube and an external device outlet located in a lower half of the external device, and the sensor element located in an upper half of the external device. Additionally or alternatively, the method may further include the flow tube fluidly connecting the internal chamber to the exhaust tube, further comprising an internal device outlet fluidly connecting the internal chamber to the annular space in an upper half of the external device.

[0057] 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). In particular, 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 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. FS sensor regeneration is typically controlled using timers, and the timer may be set at 602 to a period of time the length of a threshold.Alternatively, sensor regeneration may be controlled by using a temperature measurement of the sensor tip or 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 on to continue regeneration, and the method ends. Method 600 may continue to monitor the regeneration duration if the threshold duration has not elapsed and the regeneration circuit is ON. If the threshold length period has elapsed (e.g.,If the response is "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.

[0058] In some examples, additionally or alternatively, a voltage provided to the heating element to regenerate the sensor substrate may be reduced as an engine load increases. For example, if an engine load is high, then the controller signals an actuator to provide less voltage to the heating element, thereby consuming less current. Regeneration of the sensor substrate may still be achieved by exhaust gas flowing through the FS sensor assembly. Further, due to the proximity of the sensor substrate to the outdoor device, along with the restriction of the annular space between the sensor substrate and the outdoor device, the heat and velocity of the exhaust gas through the annular space may still promote regeneration and / or removal of the particulates. For example, the exhaust velocity and heat may remove the particulates more easily than a low engine load.Furthermore, more oxygen can flow through the FS sensor assembly, increasing the likelihood of particulate combustion even when less voltage is supplied to the heater. Thus, during an engine load where voltage is a light load, the controller can signal the heater actuator to provide full voltage due to the reduced exhaust flow and temperatures. Thus, the heater becomes hotter during low engine loads than at higher engine loads. In this way, the heater's power consumption during regenerations at higher engine loads can be reduced.

[0059] 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) that flows into the DPF.

[0060] 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 calculate, through calibration, 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 diagnosis for the DPF. If t(i)_regen is less than half the value of t(il)-region, then at 708, the DPF is indicated to be leaking, and a DPF degradation signal 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.

[0061] 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 sensor can be detected based on a rate of deposition of the particulates on the particulate sensor electrodes.

[0062] 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 may 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.

[0063] 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.

[0064] A regeneration cycle of the FS sensor is shown 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.

[0065] 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, if the FS sensor is located upstream of the DPF.

[0066] 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 requests 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, for example, formed 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.

[0067] 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 (plot 804). However, at t3, the soot load on the DPF (plot 804) reaches a threshold load for regenerating the DPF (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.

[0068] Another DPF cycle is shown between t5 and t6. Here, the soot load on the DPF gradually increases between t5 and t6 (diagram 804). During this time, the soot load on the FS sensor (diagram 802) can be monitored. Diagram 802 shows that the FS sensor undergoes several regeneration cycles as described above. However, the regeneration frequency of the FS sensor has almost doubled (diagram 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.

[0069] 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 requirements. Therefore, this reduces the high warranty costs for replacing functioning particulate filters and extends the service life of exhaust components.

[0070] In this way, a sensor element can be shielded by one or more spherical protective tubes, which further enhance uniform soot deposition. Exhaust gases can enter the sensor assembly via a flow tube located on a downstream surface of the spherical assembly. Accordingly, the exhaust gas can undergo changes in flow direction, which helps to reduce the flow rate. Additionally, water droplets and larger contaminants flow past the flow tube due to their greater momentum compared to smaller particles. The exhaust gas is directed to the internal chamber of the indoor device, where the exhaust gas is separated from the annular space and the sensor element. Exhaust gas then flows through the outlet of the indoor device and into the annular space, where the exhaust gas can flow around the sensor element.In this way, by separating the inner chamber from the sensor element, problems of uneven soot deposition due to the uniform flow created by the annular space can be prevented. Thus, the annular space between the inner device and the outer device can be sized, shaped, and positioned to create a uniform flow of exhaust gases onto the sensor surface.

[0071] One technical effect of achieving 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 at the particulate matter sensor surface can be increased. Furthermore, by positioning the sensor element outside the internal chamber in the annular space, exhaust gas is forced to flow past the sensor element before being expelled from the spherical assembly.

[0072] A particulate matter sensor assembly includes a spherical assembly, an inner device positioned within an outer device of the spherical assembly, offset from a geometric center of the outer device, and a sensor element located on an outer surface of the inner device, proximal to a narrowest passage between the outer device and the inner device. A first example of the particulate matter sensor assembly further includes the inner device being fixedly mounted within the outer device via a flow tube and a support. A second example of the particulate matter sensor assembly, optionally including the first example, further includes the flow tube being positioned obliquely to a vertical axis of the outer device and against a downstream surface of the outer device relative to a direction of exhaust flow.A third example of the particulate matter sensor assembly, optionally including the first and / or second examples, further includes wherein the support is positioned perpendicular to the flow tube and against an upstream surface of the outdoor device, and wherein the support is solid and the flow tube is hollow. A fourth example of the particulate matter sensor assembly, optionally including one or more of the first to third examples, further includes wherein the sensor element is cylindrical and positioned around a largest diameter of the indoor device.A fifth example of the particulate matter sensor assembly, optionally including one or more of the first through fourth examples, further includes the indoor device including an interior chamber located therein, and the spherical assembly including an annular space located between the outdoor device and indoor device, further including an indoor device outlet fluidly connecting the indoor chamber to the annular space. A sixth example of the particulate matter sensor assembly, optionally including one or more of the first through fifth examples, further includes the indoor device including a first recess corresponding to the indoor device outlet near a top of the indoor device and a second recess corresponding to a flow tube near a bottom of the indoor device.A seventh example of the particulate matter sensor assembly, optionally including one or more of the first to sixth examples, further comprises that the indoor device is completely spaced from and suspended within the outdoor device, and that the outdoor device is a spherical shape and the indoor device is an elongated shape.

[0073] An exemplary particulate matter sensor includes a pair of interdigitated electrodes formed on a first surface of a cylindrical sensor element, a heating element formed on a second surface of the cylindrical sensor element, the second surface being opposite the first surface, and a flow tube and a spacer suspending an inner device within an outer device of a spherical assembly, the inner device being spaced completely away from the outer device via an annular space. A first example of the particulate matter sensor further includes the second surface of the cylindrical sensor element being pressed against an outer surface of the inner device and the first surface of the sensor element being exposed to the annular space.A second example of the particulate matter sensor, optionally including the first example, further includes wherein the flow tube is configured to direct exhaust gas downstream of the spherical assembly to an interior chamber positioned within the indoor device, and wherein the spacer is impermeable to exhaust flow. A third example of the particulate matter sensor, optionally including the first and / or second example, further includes wherein the spherical assembly is mounted within an exhaust passage via a support rod extending from a top of the exhaust passage along a vertical axis. A fourth example of the particulate matter sensor, optionally including one or more of the first through third examples, further includes wherein the indoor device is elongated and the outdoor device is spherical, and wherein a center of the indoor device is offset from a center of the outdoor device.A fifth example of the particulate matter sensor, optionally including one or more of the first through fourth examples, further includes that the sensor element is located around a largest periphery of the indoor device, downstream of a narrowest gap between the outdoor device and indoor device. A sixth example of the particulate matter sensor, optionally including one or more of the first through fifth examples, further includes that the spherical assembly defines an exhaust passage forming a venturi throat at an outdoor device outlet of the outdoor device. A seventh example of the particulate matter sensor, optionally including one or more of the first through sixth examples, further includes that the outdoor device and indoor device do not include any inlet and outlets other than the flow tube, indoor device outlet, and outdoor device outlet.

[0074] A method includes flowing exhaust gas from below a particulate filter into an exhaust sensor assembly via a flow tube positioned between indoor and outdoor devices in a direction counter to the exhaust flow in an exhaust pipe, the flow tube being connected to downstream surfaces of the indoor and outdoor devices and directing the exhaust gas toward an interior chamber in the indoor device before the exhaust gas flows to an annular space located between the indoor and outdoor devices, the exhaust gas flowing in a direction orthogonal to the exhaust flow in the exhaust pipe. A first example of the method further includes flowing the exhaust gas in the annular space via a sensor element connected to a surface of the indoor device outside the interior chamber.A second example of the method, optionally including the first example, further includes the flow tube and an external device outlet located in a lower half of the external device, and the sensor element located in an upper half of the external device. A third example of the method, optionally including the first and / or second example, further includes the flow tube fluidly connecting the internal chamber to the exhaust tube, further comprising an internal device outlet fluidly connecting the internal chamber to the annular space in an upper half of the external device.

[0075] 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 into 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.

[0076] It should be 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.

[0077] 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.

Claims

[1] Method comprising: Flowing exhaust gas from downstream of a particulate filter (102) into an exhaust sensor assembly (202) via a flow tube (206) disposed between an indoor and outdoor device (218, 216) in a direction opposite to the flow of exhaust gas in an exhaust pipe (210), the flow tube (206) being connected to downstream surfaces of the indoor and outdoor devices (218, 216); and Directing the exhaust gas towards an internal chamber (242) in the internal device (218) before the exhaust gas flows to an annular space arranged between the internal and external devices (218, 216), wherein the exhaust gas flows in a direction orthogonal to the flow of the exhaust gas in the exhaust pipe (210). [2] The method of claim 1, wherein the exhaust gas in the annular space is directed over a sensor element (234) connected to a surface of the internal device (218) outside the internal chamber (242). [3] The method of claim 2, wherein the flow tube (206) and an outlet (246) of the outdoor device (216) are arranged in a lower half of the outdoor device (216) and the sensor element (234) is arranged in an upper half of the outdoor device (216). [4] The method of claim 1, wherein the flow tube (206) fluidly connects the inner chamber (242) to the exhaust tube (210), and further comprising an outlet (244) of the inner device (218) fluidly connecting the inner chamber (242) to the annular space in an upper half of the outer device (216). [5] The method of claim 2, wherein the sensor element (234) is cylindrical, wherein a pair of interdigitated electrodes (406, 408) is formed on a first surface of the sensor element (234), and wherein a heating element (238) is formed on a second surface of the sensor element (234), the second surface being opposite the first surface. [6] The method of claim 1, wherein the exhaust gas sensor assembly (202) is spherical and constricts an exhaust gas passage to create an exhaust gas restriction at an outlet (246) of the outdoor device (216).

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