Exemplary embodiments of the present invention relate to methods and devices for monitoring the flow of particulate matter within an exhaust gas stream. More specifically, in one exemplary embodiment, the present invention relates to diesel particulate sensors having improved sensing capabilities
Emissions from stationary and mobile fossil burning devices have been and will continue to be of particular concern in view of accumulating laws and regulations restricting emissions from such devices. In one aspect, particulate matter within emissions has been regulated causing industries, particularly the automotive industry, to utilize particulate matter removal devices, such as filters. Such removal devices are configured to catch or trap particulate matter flowing through an exhaust gas stream prior to exiting an exhaust system. To determine when the particulate matter filter is reaching its capacity, the total volume or volume flow rate of particulate matter flowing into the filter or within the exhaust gas stream is monitored. Monitoring is often achieved through a particulate matter sensor exposed to the exhaust gas flow. The particulate matter sensor functions by transmitting signals based upon electrical potential across the probe of the sensor. For example, as ionized particulate matter within the exhaust gas passes across the sensor, electrical potential across the sensor increases or decreased providing an indication of the amount of particulate matter that has traveled past the sensor and into the filter.
However, many of these sensors fail to provide accurate readings of particulate matter flowing past the sensor or within an exhaust gas stream. For example, certain sensors are not sufficiently robust to withstand forces or temperatures encountered by such sensors. Other problems with certain sensors are their inability to accurately indicate the presence of particulate matter within an exhaust gas flow due to poor signal noise ratio. Still other problems exist as well. Accordingly, in view of the shortcomings of previous sensor designs, there is a need for improved methods and devices for monitoring the flow of particulate matter flowing within and exhaust gas stream.
Exemplary embodiments of the present invention relate to methods and devices for monitoring the flow of particulate matter within an exhaust gas stream. In one exemplary embodiment, a particulate matter sensor for an exhaust system of an engine is provided. The particulate matter sensor includes a housing having a first end and a second end. The housing includes a sealing feature located at the first end of the housing for forming a seal between the housing and a corresponding component. The housing further includes an attachment feature located between the first end and the second end of the housing for attachment of the particulate matter sensor to the exhaust system. The particulate matter sensor further includes a sensing rod extending from the first end of the housing. The sensing rod is configured to generate a signals based upon particulate matter flowing within the exhaust system of the engine. The particulate matter sensor also includes an electrical connector extending from the second end of the housing. The electric connector is in communication with the sensing rod to transmit signals generated by the sensing rod.
In another exemplary embodiment, a method of monitoring particulate matter flowing within an exhaust gas stream of an engine is provided. The method includes: forming an opening through an exhaust conduit of an exhaust system, the opening defining a first sloped surface and a first threaded portion; forming a particulate matter sensor having a housing, sensing rod and electrical connector, the housing including a first end and a second end, the housing further including a second sloped surface disposed at the first end and a second threaded portion located between the first end and the second end; and threadably engaging the first and second threaded portions to cause engagement and sealing of the first and second sloped surface, wherein upon engagement the sensing rod is located within an exhaust gas stream and generates signals based upon the presence of particulate matter, the signals being transmitted to a controller through the electrical connector.
The above features and advantages and other features and advantages of the present invention are readily apparent from the following detailed description of the best modes for carrying out the invention when taken in connection with the accompanying drawings.
Other objects, features, advantages and details appear, by way of example only, in the following detailed description of embodiments, the detailed description referring to the drawings in which:
Exemplary embodiments of the present invention provide methods, systems and devices for detecting and monitoring particulate matter flowing in an exhaust gas stream. In one particular exemplary embodiment, a particulate matter sensor is provided. The particulate matter sensor is configured for detecting and monitoring particulate matter flowing within an exhaust gas stream for determining volume or volume flow rate of particulate matter flowing within the stream. In one particular exemplary embodiment, the particulate matter sensor includes a sensing rod having an increased surface area for improving accuracy in the detection and monitoring of particulate matter within the exhaust gas stream. In one configuration, the increased surface area of the sensor rod is achieved through the structure of the particulate matter sensor, which allows for larger diameter sensing rods to be used. Other advantageous will become apparent as shown and described herein.
In general, referring to
In one exemplary operation, referring to
Reference is also made to the following patent applications: U.S. Provisional Patent Application Ser. No. 61/083,328 filed Jul. 24, 2008 and U.S. patent application Ser. No. 12/508,272, filed Jul. 23, 2009; U.S. patent application Ser. No. 12/467,673, filed May 18, 2009; and U.S. Provisional Patent Application Ser. No. 61/083,333 filed Jul. 24, 2008 and U.S. patent application Ser. No. 12/508,096 filed Jul. 23, 2009, the contents of each of the aforementioned provisional and non-provisional applications are incorporated herein by reference thereto.
Reference is also made to the following U.S. Pat. Nos. 6,971,258; 7,275,415; 5,697,334 and 4,111,778 the contents each of which are incorporated herein by reference thereto.
In one exemplary embodiment, a controller 40 is provided for receiving the signals and determining the total amount of particulate matter that has flowed past the sensing rod 12 and hence into the exhaust control device 32. In this embodiment, the controller includes suitable algorithms for determining the amount of particulate matter flowing past the sensor assembly 10 and hence into the exhaust control device 32. In one exemplary embodiment, the controller may also be in communication with one or more regeneration devices or configurations, for causing an increase in temperature of the exhaust control device 32 and/or sensor assembly 10 suitable for causing removal or inhalation of accumulated particles. As such, once the controller determines that total volume of particulate matter that has passed the sensor assembly 10 has reached a predetermined level, the controller 40 may initiate regeneration of the exhaust control device 32 and the particulate matter sensor assembly 10.
In greater detail, referring to both
The above referenced configuration is particularly advantageous as it allows for increased diameter of the sensing rod 12. This is due to the placement of the sealing feature at an end portion (e.g., first end 46) of the housing 14. In prior configurations, the sealing feature was located on a side of the attachment feature that is opposite of the sensing rod, e.g., between the first and second end of the housing. As such, the attachment feature, e.g., threads, are formed within the diameter of the sealing feature, which results in a smaller diameter sensing rod. Through the configuration of the housing of the present invention, larger sensing rods 12 can be used, which provide for increased sensing accuracy and improves robustness of the sensing rod due to the larger mounting diameter. This is because by placing the sealing feature 44 at an end of the housing 14, the use of a sealing surface extending beyond an attachment feature, such as done in prior sensor assemblies, is no longer necessary. This allows for the diameter of the probe to be more similar to the diameter of the attachment feature, or threads, thereby allowing for a larger probe.
For example, previous sensors have been limited to 4 mm probes with 14 mm threads or 6.5 mm probes with 18 mm threads. Through the features of the present invention, it is possible to utilize 10 mm probes with 16 mm threads. Not only does this provide for increased accuracy of the particulate matter sensor, but also provides for a more robust sensor assembly 10 due to the larger mounting base of the probe 16, for mounting to mount 19. It should be appreciated that other larger diameter probes and threads are possible. Accordingly and in one exemplary embodiment, the outer diameter of the sensing rod is at least about 50% of a diameter of the sealing feature of the housing. In another embodiment, the outer diameter of the sensing rod is at least 85% of a diameter of the sealing feature of the housing. Of course, other suitable diameters greater or less than the aforementioned values are considered to be within the scope of exemplary embodiments of the present invention.
Still referring to
To prevent grounding of the sensing rod 12, the first insulator 20 comprising a compressed powder dielectric material (e.g., talc or equivalent thereof) is disposed between the sensing rod and the housing 14. The configuration of the first insulator and housing 14 also forms a gap 58 between the sensing rod 12 and the housing. Alternatively, gap 58 may be filled with the material of the first insulator 20. In one exemplary embodiment and through the configuration and placement of the first and third insulators, an air gap 62 is also formed between the mount 19, which is electrically conductive, and the housing 14. As such, through this configuration signals formed by the sensing rod 12 are prevented from grounding through the housing 14.
The sensing rod 12 may be formed of any suitable material for detection of particulate matter or other material of interest. In one configuration, the sensing rod is formed of an electrically conductive or semi-conductive material and is also capable of withstanding deleterious effects of exhaust emission (e.g., heat, corrosiveness, or otherwise). For example, the sensing rod may be formed of conducting or semiconducting material such as metal, metal alloy or otherwise. In another example, the sensing rod may be formed of an insulating material, such as ceramic or glass, and include a conductive or semi-conductive layer thereover, such as metal, metal alloy or otherwise. In either of these configurations, or otherwise, the conductive or semi-conductive material may include a non-conducting or dielectric layer applied or placed thereover for protection of the conductive material or otherwise, such as described below. Examples of some suitable conducting materials include nickel alloys such as HAYNES® 214® or HAYNES® 240®, both of which are sold by Haynes International Inc. of Kokomo, Ind., U.S.A.
Similarly, the sensing rod 12 may be formed through any suitable forming process including molding, stamping or otherwise. In one exemplary embodiment, the probe 16 of the sensing rod comprises a hollow tube member. In this configuration, it is contemplated that the probe 16 and/or sensing rod 12 is formed through a deep drawn process, or the like. Other methods are possible.
In one exemplary embodiment, the sensing rod 12 is formed with, generates or otherwise includes an insulating material or layer thereover to prevent transmission of electric current to or from unwanted components. In one configuration, the insulating material or layer comprises an oxide coating of a material forming the sensing rod. Suitable materials include materials capable of forming an oxide coating or layer that has low thermal and/or electrical conductivity. One exemplary material includes a first material comprising nickel alloy and a second material comprising aluminum and one or more of yttrium or zirconium. Other materials and combinations are possible.
As previously mentioned, the sensing rod 12 is in communication with one or more additional devices for transmission of signals from the probe 16 to another device, through electrical connector 18. In one exemplary embodiment, the sensing rod 12 is attached directly to the electrical connector 18. In another exemplary embodiment, referring to
In one exemplary embodiment, referring to
The particulate matter sensor assembly 10 may be used in various industries for determining a flow of particulate matter. These industries include, without limitation, automotive industry, freight industry, mass transit industry, power generating industry such as power plants or factors, or other emission producing industry. In one particularly advantageous application, the particulate matter sensor assembly 10 is useable within the automotive industry and more particularly with internal combustion engines of vehicles for monitoring particulate matter generated thereby. In this configuration, the particulate matter sensor assembly 10 is placed within the exhaust gas stream flowing through an exhaust gas conduit, exhaust treatment device or otherwise, from a diesel engine, gasoline engine or otherwise.
In one exemplary embodiment, an exhaust control system is provided for monitoring and removing particulate matter from an exhaust gas stream. The exhaust system includes and exhaust control device, such as a particulate matter filter, which is in fluid communication with an engine through a suitable exhaust gas conduit. The exhaust control system also includes one or more particulate matter sensors. As exhaust gas flows through the exhaust gas conduit, particulate matter for a given time period is determined by monitoring an electrical signal across a surface of the probe generated by an electrical potential of particles flowing past the probe to determine the amount of particulate matter that has flowed into the exhaust control device. The particulate matter sensor generates signals based upon the charged particles flowing past the probe. The signals are received by a controller configured for determining the total amount of particulate matter that has flowed past the probe and into the particulate matter filter based upon the signals received.
Further exemplary embodiments include monitoring particulate matter flowing within an exhaust gas stream using a sensing rod constructed in accordance with exemplary embodiments of the present invention. In one embodiment, the method includes generating signals with the particulate matter sensor based upon the presence of particulate matter flowing in the exhaust gas stream and flowing past the sensor and thus creating an electrical signal in the probe based upon the electrically charged particles or the electrical potential of the particles flowing past the sensing rod of the probe. As previously mentioned and in one exemplary embodiment, the signal is based upon a charge created in the probe based upon particulate matter flowing past the sensor. The controller receives the signals and determines at least one flow characteristic of particulate matter flowing within the exhaust gas stream such as total amount of particulate matter flowing by the sensor and into the emission control device, or volume flow rate of particulate matter or otherwise.
While the invention has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiments disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the present application.
The present application claims the benefit of U.S. Provisional Patent Application Ser. No. 61/100,507 filed Sep. 26, 2008, the contents of which is incorporated herein by reference thereto.
Number | Date | Country | |
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61100507 | Sep 2008 | US |