Patent Description:
Heat flux is a useful measure for predicting relative heater element performance, including temperature, transfer efficiency, and life-time. The flux density exhibited by a heater element is defined as Watt density (watts/mm<NUM>), which represents a measure of the magnitude of the power that can be concentrated per square millimeter of an element's surface area. A heater element that exhibits a high Watt density will generally provide a fast temperature rise and a lower overall manufacturing cost due to the reduced amount of surface area that is required. However, these advantages are often off-set by the risk of reduced lifetime due to the higher surface temperatures that are encountered, as well as the potential for lower reliability (e.g., over-shooting the desired temperature condition, etc.). <CIT> discloses a heater system according to the preamble of claim <NUM>.

During manufacturing, variances encountered in processing conditions and heater construction can result in differences in the heat flux that are exhibited within different portions of a single heater element or between the various heater elements that are produced. In order to compensate for this manufacturing variability, and ensure reliability at the expense of maximizing performance (e.g., rate of heating) and minimize cost (e.g., lowering the element's surface area), the industry conventionally applies a safety factor, which results in a reduction in the Watt density exhibited by the heater element.

In overcoming the enumerated drawbacks and other limitations of the related art, the present invention provides a smart heating system according to claim <NUM>. The performance information may be stored as written text, a bar code, a data matrix, or a radio frequency identification (RFID) tag. The smart heating system heating system may further comprises a LIN or a CAN bus capable of providing a communication pathway between at least two system components.

According to one aspect of the present disclosure, the smart heating system may further comprise at least one support bracket in contact with the at least one heater element and optionally with the at least one temperature sensor. The performance information may include only heater information or a combination of both heater and sensor information. The heater performance information may include the rate of heating that occurs at a desired voltage or under a specified flow condition.

According to another aspect of the present disclosure, the heating system may further comprise a power switch that receives signals from the ECU. In this case, the performance information may also include switch information. The power switch can be controlled by a switch control unit that is in communication with the ECU and uses the switch information. The switch information may include a measurement of the current and/or voltage, as well as the rate of heating associated with the solid state components of the switch as a function of the amount of electrical current that is being switched.

According to yet another aspect of the present disclosure, the smart heating system includes multiple heater elements and temperature sensors, the temperature sensors being a combination of individual sensors or a junction sensor capable of providing more than one temperature measurement. The temperature sensor may be selected as a thermocouple, a thermistor, or a resistance temperature device. The heater element may be selected as a cable heater, a tubular heater, a cartridge heater, a flexible heater, a layered heater, a metal foil, or a metal fleece heater.

The smart heating system may be used to compensate for a thermal gradient present in a diesel oxidation catalyst (DOC), diesel particle filter (DPF), selectic catalytic reducer, lean NOx traps, or another exhaust component that includes an after-treatment catalyst. Thus diesel exhaust system may be constructed to comprise the smart heating system as described above and hereafter.

The following description is merely exemplary in nature and is in no way intended to limit the present disclosure or its application or uses. It should be understood that throughout the description, corresponding reference numerals indicate like or corresponding parts and features.

The present disclosure generally relates to a smart heating system and a method of use associated therewith. The smart heating system made and used according to the teachings contained herein is described throughout the present disclosure in conjunction with diesel exhaust applications in order to more fully illustrate the concept. The incorporation and use of smart heating system in conjunction with other types of thermal management applications is contemplated to be within the scope of the disclosure.

The following specific embodiments are given to illustrate the design and use of smart heating systems according to the teachings of the present disclosure and should not be construed to limit the scope of the disclosure. Those skilled-in-the-art, in light of the present disclosure, will appreciate that many changes can be made in the specific embodiments which are disclosed herein and still obtain alike or similar result without departing from or exceeding the scope of the disclosure. One skilled in the art will further understand that any properties reported herein represent properties that are routinely measured and can be obtained by multiple different methods. The methods described herein represent one such method and other methods may be utilized without exceeding the scope of the present disclosure.

A smart heating system general comprises at least one heater element with predetermined (e.g., measured) or predictable performance characteristics. One example of such performance characteristics includes the rate of heating for the heater element when it is exposed to a preselected voltage or under a specified process flow condition. Although the average performance for multiple heater elements of the same or substantially similar design that are manufactured by the same process under similar process conditions represents valuable information, the measurement or knowledge of how each individual heater element in the system performs allows one to control the system's overall performance with respect to fast heating without sacrificing overall reliability. One specific example of a performance characteristic for a heater element that can be used to control a system's overall performance includes, without limitation, the locations associated with any non-uniformity in sheath temperature as shown by the temperature profile exhibited by the heating element under a known or predetermined flow/process condition.

A smart heating system provides the benefits of enhanced diagnostic capability in addition to maximizing heat flux and lowering manufacturing cost. A robust diagnostic capability often depends on the variation exhibited from heater element to heater element. A system that is capable of using performance characteristics or information for specific heater elements provides for enhanced diagnostic capability by allowing at least a portion of the random variation that arises from manufacturing variances to be corrected or compensated for.

The specific characteristics or information can be stored in any known format that is desirable, including but not limited to written text, bar codes, data matrix, and radio frequency identification (RFID), as well as being communicated on a digital bus or any other information or communication method known to one skilled in the art.

According to one aspect of the present disclosure, the smart heating system may comprise at least one heater element or alternatively, a combination of at least one heater element and at least one temperature sensor. The sensor may be in contact with the sheath of the heater element (see <FIG>), located on a bracket adjacent to the heater element, or located upstream or downstream of the heater element (see <FIG>). The sensor is capable of measuring the temperature in a specific or desired location of the heater element. The measurement of temperature by the sensor allows the system to reduce power when the heater element is approaching or surpassing a predetermined temperature limit established according to the application being performed.

Referring to <FIG>, one specific combination of the smart heating system <NUM> is shown that comprises a tubular heater element <NUM> and a thermocouple <NUM>. The thermocouple <NUM> can be in contact with or attached to the sheath of the heater element <NUM> (<FIG>) or located adjacent to the heater element <NUM> (<FIG>). One skilled in the art will understand that other types of heaters and sensors, may be used without exceeding the scope of the present disclosure. Optionally, the thermocouple <NUM> may be in communication with or attached to a signal conditioning module <NUM> that is capable of storing and/or processing information, such as, without limitation, sensor time response, sensor contact resistance to the heater's sheath, heater's maximum temperature limit, maximum ramp rate for the heater, heater resistance, and the heater's temperature profile or distribution map, as well as the difference in temperature between the heater and the area adjacent to the heater. The maximum temperature limit and the maximum ramp rate may be determined for a specific heater element <NUM> and sensor <NUM> combination using conventional testing and inspection of the combination.

Since the signal conditioning module <NUM> may comprise an input and output (I/O), an analog to digital converter (ADC), and a microprocessor, it is possible to use said module to make or communicate other measurements, including but not limited to, the magnitude of current leakage to ground, as well as the voltage and/or current applied to the heater. The measurement of current leakage is useful for determining if the heater insulation resistance (IR) is low and can be used to adjust the rate of applying voltage to the heater in order to remove moisture and/or extend the lifetime of the heater. The measurement of the applied voltage and/or current can be used to determine Power and heat flux associated with the smart heating system <NUM>, as well as to detect the occurrence of any defects or faults.

Still referring to <FIG>, a signal conditioning module <NUM> with digital communication capability may alternatively be used. Such digital communication capability may include the use of a local interconnect network (LIN) bus or controller area network (CAN) bus, as well as any other digital bus known to one skilled in the art. The digital bus receives measurements, such as temperature, current leakage, voltage, current, etc. from another device that is in communication with the bus through the use of an integral connector <NUM>, which in turn allows the signal conditioning module <NUM> to become aware of and use this information instead of information that itself had measured.

According to another aspect of the present disclosure, the types of information collected and/or communicated may be utilized to enhance control of the heater system with respect to performance. For example, the information may be used to calculate (a) control parameters to avoid over temperature conditions associated with the heater; (b) a slow ramp for voltage at low current (I)-resistance (R) conditions in order to allow moisture to be evaporated; or (c) a diagnostic limit designed to prolong the lifetime of the heater system. An example of such a diagnostic limit (DL), may include the calculation of the change in temperature (ΔT) per unit time (Δt) per a predetermined variable (x) as shown in Equation <NUM>. This predetermined variable (x) is selected based upon the specific application in which the smart heating system is being used. In certain applications, this variable (x) may be the applied voltage, the amount of fuel used, or the mass flow of an exhaust, among others.

According to another aspect of the present disclosure, the smart heating system may comprise more than one temperature sensor. Referring now to <FIG>, a smart heating system <NUM> having a heater <NUM> in contact with more than one temperature sensor <NUM>, alternatively, multiple sensors <NUM>, alternatively, at least three sensors <NUM> is shown. The use of multiple sensors <NUM> allows the smart heating system <NUM> to measure temperature at several locations of the heater element <NUM>, thereby, allowing calculation of differences in the measured locations. The calculation of these temperature differences provides for more precise control of the heater element <NUM> thereby increasing lifetime, as well as avoiding any damage resulting from localized over-heating.

In many applications, thermal gradients will exist in the environment to which the smart heating system is exposed. For example, thermal gradients may exist within a diesel oxidation catalyst (DOC) that can vary as a function of time and/or engine condition. Thermal gradients may also exist in other after treatment components, such as diesel particle filters (DPF), selective catalytic reducers, or lean NOx traps, among other components present in the exhaust stream that include an after-treatment catalyst. At least part of the function of an after-treatment catalyst is to facilitate a chemical reaction with the exhaust gases in order to reduce pollutants to comply with emission regulations. Since such chemical reactions have a dependency on temperature, a variation or gradient in temperature will affect the rate at which these reactions proceed. The use of a smart heating system <NUM> can improve the performance of the after-treatment component by effectively controlling the temperature at a level that facilitates the occurrence of the chemical reaction.

Still referring to <FIG>, in a diesel exhaust system, a smart heating system <NUM> with multiple sensors <NUM> is exposed to exhaust gases. In this application, the smart heating system <NUM> can detect variations in temperature caused by thermal flow distribution of the exhaust gases and compensate or adjust accordingly in order to maximize the performance and/or lifetime of the heater element <NUM>. Thus sensor information includes a measurement of temperature conditions in a location adjacent to the heater element <NUM>. A similar arrangement with a single sensor is also shown in <FIG>. The use of multiple sensors <NUM> can also be used to measure or predict additional diagnostic conditions when used in various applications. A few examples of which include the measurement of temperature gradients (i) downstream in a diesel particulate filter (DPF) in order to determine non-uniform soot build-up in the DPF; (ii) downstream of a diesel oxidation catalyst (DOC) in order to identify the occurrence of non-uniform oxidation or face-plugging of the DOC; and (iii) upstream of a DOC in order to identify non-uniform temperatures so that more accurate energy balance calculations can be obtained.

According to another aspect of the present disclosure, the smart heating system may further comprise a support bracket. In some applications, such as in a diesel exhaust system, among others, the vibrations arising from the application may be to such a degree that at least one support bracket is necessary to mount the smart heating system. Referring now to <FIG>, each mounting bracket <NUM> may be used to support a heating element <NUM> of the smart heating system <NUM>. When desirable the temperature sensor <NUM> may also be supported by one of the brackets <NUM>. When multiple sensors <NUM> are utilized, each sensor <NUM> may be in contact with a bracket <NUM>.

Alternatively, a junction sensor <NUM> may be utilized (<FIG>) with such sensor <NUM> being in contact with the bracket <NUM> in multiple locations. A junction sensor <NUM> provides multiple temperature measurements. As shown in <FIG>, the specific junction sensor <NUM> shown provides for a temperature measurement at the center of the heater can (junction J1) and at four other locations (junctions J2-J5). In <FIG>, a smart heating system <NUM> is shown with a bracket <NUM> providing support for a heater element <NUM> and a junction sensor <NUM> that provides for temperature measurement at three locations (junctions J1-J3). One skilled in the art will understand that many other different sensors <NUM>, <NUM> and bracket <NUM> combinations may be utilized without exceeding the scope of the present disclosure.

In general, a smart heating system <NUM> that has multiple sensors <NUM>, <NUM> measuring temperature commands better performance, lower heater cost, greater reliability and enhanced diagnostic capability than a similar sensor comprising a single sensor <NUM>. The use of a junction sensor <NUM> may become a lower cost alternative as compared to the use of multiple individual sensors <NUM>.

Referring now to <FIG>(A-C), the smart heating system <NUM> may comprise multiple heater elements <NUM>. In <FIG>, multiple circulation heater elements <NUM> having a U-shaped bend are shown in an exhaust component <NUM>. In <FIG>, multiple circulation heater elements <NUM> are shown that have a circular shape. Multiple heater elements <NUM> can be used to create a desired temperature profile. For example, all of the heater elements <NUM> could be powered at the same time or alternated such that an uniform temperature is established in the exhaust / after treatment system <NUM> in order to facilitate the chemical reaction. Alternatively, some of the heater elements <NUM> can be fabricated and powered at different levels in order to create a different amount of heat and to modify the thermal gradient that exists within the exhaust or after treatment component <NUM>. Several specific examples in which heater elements create different amounts of heat include (a) providing heater elements <NUM> located on the periphery with a different amount of power than those located in the interior of the exhaust component <NUM>; and (b) providing heater elements <NUM> located in different quadrants with in the exhaust component <NUM> in order to control thermal gradients on a quadrant by quadrant basis. Alternatively, heater elements <NUM> may be placed only around the periphery of the exhaust component <NUM> in order to establish a single heating zone that can be used to reduce or improve radial temperature gradients.

Similar to the use of multiple heaters, the use of multiple sensors located in predetermined places based on their ability to add value in measuring the thermal gradient. The temperature sensors can be thermocouples, thermistors, resistance temperature devices, and any other known means of measuring or detecting temperature. A heater element having a resistance that varies with temperature may be used as a <NUM>-wire heater/sensor combination. The heater element may include without limitation cable heaters, tubular heaters, cartridge heaters, flexible heaters, layered heaters, metal foils, metal fleece heaters, or any other type of heater known to one skilled in the art.

Referring now to <FIG>, one specific example of a smart heating system <NUM> designed for controlling temperature is shown. In this system <NUM> design, the heater element <NUM> receives power from a switch <NUM> that can be actuated using signal(s) from the heater control unit <NUM>. The heater control unit <NUM> receives information from one or more sensors <NUM> and/or an electronic control unit <NUM>. Based on the information, the heater control unit <NUM> communicates with the power switch <NUM> and relays the power to the heater element <NUM>. The power switch <NUM> relays may be integrated into the heater control unit <NUM> when desirable. The heater elements <NUM> are distributed so that they are capable of providing a preferred or desirable temperature profile in the after treatment exhaust system in order to enhance performance of the after treatment system. Enhanced performance with respect to a diesel exhaust system includes without limitation improved NOx production by the diesel oxidation catalyst (DOC) or in a catalyzed diesel particulate filter (DPF); improving ammonia storage or NOx conversion, or improving other chemical reactions.

During the construction of a smart heating system, the heater may be mounted with the information related to the heater attached to the heater assembly via a barcode, data matrix, RFID tag, or any other known method. Such heater information may include, among others, rating of heating, resistance, maximum voltage as a function of time, etc. Referring now to <FIG>, the smart heating system <NUM> may be utilized via an open loop control mechanism <NUM>. In this mechanism <NUM>, the smart heating system <NUM>, which includes a heater <NUM> along with its related information <NUM>, is in communication with an electronic control unit (ECU) <NUM>. The heater information <NUM> may be either manually or automatically communicated to the ECU <NUM> or to a switching device <NUM> to enable better use of the heater <NUM>. A similar benefit associated with using the heater information <NUM> equally applies to a closed loop control mechanism <NUM> as described in <FIG> that incorporates an external temperature sensor <NUM>.

Alternatively, a smart heating system can be utilized that includes information about both the heater and temperature sensor(s). Referring now to <FIG>, a smart heating system <NUM> that includes both a heater <NUM> and sensor <NUM> combination that is marked with both heater and sensor information <NUM> as previously described above for a smart heating system <NUM> that includes only heater information <NUM> (see <FIG>) or if the sensor is an active sensor with a signal conditioning module (not shown), the information <NUM> may be stored in the memory of the conditioning module. The heater-sensor information <NUM> is communicated to an ECU <NUM> (<FIG>) or to a power switch <NUM> (<FIG>) in order to enhance the utilization of the smart heating system <NUM>. Although the smart heating system <NUM> is shown in <FIG> to be utilized in a closed loop control mechanism <NUM>, one skilled in the art will understand that an open loop control mechanism (not shown) may also be utilized as another option.

Referring now to <FIG>, a third option for using heater-sensor information <NUM> is to communicate this information <NUM> to another control unit <NUM> that controls the functionality of the power switch <NUM>. Optionally, the switch control <NUM> may also be in communication with the ECU <NUM>. Alternatively, as shown in <FIG>, the information <NUM> concerning the switch <NUM> can be incorporated with the switch control <NUM> for use along with the heater-sensor information.

Still referring to <FIG>, the switch information <NUM> may include without limitation, a measurement of the current and/or voltage, as well as the rate of heating associated with the solid state components of the switch <NUM> as a function of the amount of electrical current that is being switched. The rate of heating associated with the sensor <NUM> junction in contact with the switch <NUM> can be determined based on the electrical current (I) and the ability of the switch <NUM> to dissipate heat away from the junction. One skilled in the art will understand the relationship of this current (I) to the resistance (R) associated with a heater element <NUM> resulting in what is known as I<NUM>R heating. Thus the current to temperature relationship of the heater element <NUM> can be measured and stored as heater information <NUM>. At a predetermined fluid flow condition, which can be communicated to the ECU <NUM>, the smart heater system <NUM> comprising a heater <NUM>, sensor <NUM>, and switch <NUM> can be used to compare the rate of fluid temperature change to the rate of change in the switch <NUM> temperature in order to diagnose if the system <NUM> is operating efficiently.

Claim 1:
A smart heating system (<NUM>, <NUM>, <NUM>) comprising: one heater element (<NUM>, <NUM>, <NUM>), one temperature sensor (<NUM>, <NUM>, <NUM>), one switch (<NUM>, <NUM>, <NUM>) connected to the heater element (<NUM>, <NUM>, <NUM>), and a heater control unit (<NUM>, <NUM>, <NUM>),
characterized in that the smart heating system (<NUM>, <NUM>, <NUM>) further comprises a set of predetermined performance information (<NUM>, <NUM>, <NUM>) including heater information specific for the heater element (<NUM>, <NUM>, <NUM>), wherein the heater control unit (<NUM>, <NUM>, <NUM>) controls the heater element (<NUM>, <NUM>, <NUM>) via the switch (<NUM>, <NUM>, <NUM>) based on the heater information and information from the temperature sensor (<NUM>, <NUM>, <NUM>).