Abstract:
A vehicle system comprising: an engine; an aftertreatment system that receives exhaust gas from the engine; a clutch assembly; and a controller configured to direct adjusting slippage of the clutch assembly based on a first temperature that is selected from the group consisting of a temperature of the aftertreatment system and an expected temperature of the aftertreatment system.

Description:
PRIORITY 
     The present application is a non-provisional application of U.S. Provisional Application No. 61/993,813 filed May 15, 2014 titled AFTERTREATMENT THERMAL MANAGEMENT VIA CLUTCH ASSEMBLY, the disclosure of which is incorporated herein by reference and the priority of which is hereby claimed. 
    
    
     FIELD OF THE DISCLOSURE 
     The present disclosure generally relates to internal combustion engine systems that include aftertreatment systems. The present disclosure relates more specifically to engine systems that utilize clutch assembly settings to impact aftertreatment systems operation. 
     BACKGROUND OF THE DISCLOSURE 
     Modern internal combustion engines must meet stringent emission standards that include limits on the amount of soot and nitrogen oxides (NO x ) that may be emitted to the atmosphere. Many engines now utilize aftertreatment systems to reduce emissions to regulatory levels before release to the atmosphere. Such aftertreatment systems may operate most effectively within a certain internal temperature range, and particularly above a minimum internal temperature. However, the temperature of an aftertreatment system may be outside of the desired operating temperature range, especially upon startup of the engine and under certain engine operating conditions when load on the engine is diminished. Therefore, a need remains for systems, apparatuses, and methods to maintain the temperature of aftertreatment systems within a desired temperature range. 
     SUMMARY 
     The present disclosure provides a system and method for controlling the temperature of an aftertreatment system by adjusting slippage of a clutch assembly. 
     According to an exemplary embodiment of the present disclosure, a vehicle system is provided comprising: an engine; an aftertreatment system that receives exhaust gas from the engine; a clutch assembly; and a controller configured to direct adjusting slippage of the clutch assembly based on a first temperature that is selected from the group consisting of a temperature of the aftertreatment system and an expected temperature of the aftertreatment system. 
     According to another embodiment of the present disclosure, a method is provided including: adjusting slippage of a clutch assembly responsive to determining a first temperature selected from the group consisting of a temperature of an exhaust aftertreatment system and an expected temperature of the exhaust aftertreatment system. 
     According to another embodiment of the present disclosure, a computer readable medium containing non-transitory instructions thereon, that when interpreted by at least one processor cause the at least one processor to: adjust slippage of a clutch assembly responsive to determining a first temperature selected from the group consisting of a temperature of an exhaust aftertreatment system and an expected temperature of the exhaust aftertreatment system. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above-mentioned and other features and advantages of this disclosure, and the manner of attaining them, will become more apparent and the invention itself will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein: 
         FIG. 1  is a schematic block diagram of an embodiment of a vehicle system according to the present disclosure; and 
         FIG. 2  is a flowchart showing operation of the controller of  FIG. 1 . 
     
    
    
     Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate exemplary embodiments of the invention and such exemplifications are not to be construed as limiting the scope of the invention in any manner. 
     DETAILED DESCRIPTION 
     For the purposes of promoting an understanding of the principles of the invention, reference will now be made to a number of embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended. 
     Referring initially to  FIG. 1 , an illustrative vehicle system  10  is shown including an engine  12 . Engine  12  is any type of internal combustion engine, such as a diesel, gasoline, or natural gas engine, and/or combinations thereof 
     The illustrative system  10  of  FIG. 1  also includes an aftertreatment system  14  fluidly coupled to engine  12  to receive and treat exhaust gases from engine  12  before releasing the exhaust gases to the atmosphere. Aftertreatment system  14  illustratively includes one or more oxidation catalyst components (e.g., a diesel oxidation catalyst (“DOC”)), NO x  treatment components (e.g., a three-way catalyst, a lean NO x  catalyst, a selective catalytic reduction (“SCR”) catalyst), filtration components, either catalyzed or uncatalyzed (e.g., a diesel particulate filter (“DPF”)), and/or cleanup catalyst components (e.g., an ammonia oxidation catalyst). 
     The illustrative system  10  of  FIG. 1  further includes a drivetrain  20  coupled to engine  12  to deliver power from engine  12  to motive elements (e.g., wheels) to propel the vehicle. Drivetrain  20  includes a transmission  22  coupled to engine  12  via a clutch assembly  24  having a clutch disc or plate  26 . In one embodiment, clutch assembly  24  is a wet clutch, wherein the clutch plate  26  is immersed in a fluid that provides cooling and lubrication. Embodiments are envisioned using a dry clutch as well. In  FIG. 1 , clutch assembly  24  is shown between engine  12  and transmission  22 , but it is also within the scope of the present disclosure that clutch assembly  24  is located within transmission  22  (e.g., controlling one of multiple planetary gear sets of an automatic transmission). It is also within the scope of the present disclosure that clutch assembly  24  is a torque converter lock-up clutch. 
     The clutch plate  26  is illustratively moved relative to a flywheel  28  of engine  12  under hydraulic pressure or another suitable pressure source. When full pressure (e.g., 100% pressure) is applied to the clutch plate  26 , the clutch plate  26  is positioned in full frictional engagement (e.g., 100% engagement) with a flywheel  28  of engine  12  to rotatably couple clutch plate  26  to flywheel  28 . In this arrangement, engine  12  delivers power downstream to drivetrain  20  and the motive elements of the vehicle. When the pressure on the clutch plate  26  is removed, the clutch plate  26  is illustratively biased to separate from flywheel  28  and uncouple engine  12  from drivetrain  20  and the motive elements of the vehicle. 
     In certain situations, as discussed further below, a partial pressure (e.g., 95%, 90%, 85%, or less pressure) is applied to clutch plate  26  to position clutch plate  26  in partial engagement (e.g., 95%, 90%, 85%, or less engagement) with flywheel  28  to create a relatively loose or slip condition. This partial engagement is sufficient to transfer some of the power from engine  12  to drivetrain  20  and the motive elements of the vehicle, but some of the power from engine  12  is dissipated when the clutch plate  26  slips past the flywheel  28 . 
     The illustrative system  10  of  FIG. 1  further includes one or more controllers  30  for controlling engine  12 , aftertreatment system  14 , and/or drivetrain  20 . Controller  30  illustratively includes one or more computing devices having memory, processing, and communication hardware and/or software to receive one or more inputs, process the inputs, and generate one or more outputs based on the inputs. In one example, controller  30  is a single device. However, embodiments are envisioned where controller  30  is a distributed device. Controller  30  illustratively includes one or more modules structured to functionally execute the operations of controller  30 . These modules are illustratively implemented in hardware and/or software on a non-transient computer readable storage medium, and modules may be distributed across various hardware or software components. Controller  30  illustratively communicates information via datalinks, network communications, and/or electronic signals (e.g., a voltage, frequency, current, or pulse-width modulation (PWM) signal), for example. System  10  further includes slippage inducer  50 . Slippage inducer  50  is illustratively one or more processors (such as processors of controller  30 ) executing code to control operation of clutch assembly  24 . 
     In  FIG. 1 , controller  30  is shown in communication with a temperature sensor  40  that measures an indicating temperature (T i ) of aftertreatment system  14 . In one embodiment, a temperature of exhaust gasses being supplied to and treated by aftertreatment system  14  is used as the temperature (T i ) of aftertreatment system  14 . In other embodiments, a temperature at a certain point within aftertreatment system  14  is used as the temperature (T i ) of aftertreatment system  14 . Thus, while temperature sensor  40  is shown at an inlet to aftertreatment system  14 , embodiments are envisioned utilizing other locations for temperature sensor  40  in aftertreatment system  14 . Regardless of the specific point chosen to provide the temperature (T i ) of aftertreatment system  14 , the corresponding minimum temperature (T min ), discussed below, is chosen/determined based on the chosen point for measuring the temperature (T i ) of aftertreatment system  14 . 
     Controller  30  is also shown in communication with an engine speed sensor  42  that measures the speed of engine  12  and a vehicle speed sensor  44  that measures the actual or commanded speed (e.g., from an operator or cruise control input) of the vehicle. Additional sensors may be provided to send appropriate information to controller  30 . 
     Depending upon the specific aftertreatment components used in aftertreatment system  14 , in certain embodiments, T i  of aftertreatment system  14  affects the ability of aftertreatment system  14  to function properly, to function efficiently, and/or to regenerate or recover storage capacity or catalytic activity. Aftertreatment system  14  is associated with, at least in some operating conditions, a minimum temperature (T min ). T min  is illustratively selected such that a response is initiated when T i  is below or expected to fall below T min , as discussed further below. For example, T min  is illustratively selected as: a value at or near (e.g., within 10° C., within 25° C.) an efficient operating point for aftertreatment system  14 ; a value at or near (e.g., within 10° C., within 25° C.) a capable operating point for aftertreatment system  14 , where aftertreatment system  14  is still capable of meeting emissions targets; or a value at or near (e.g., within 10° C., within 25° C.) a “hold-warm” target for aftertreatment system  14 , where aftertreatment system  14  is expected to be capable of reaching efficient or capable operating points within a prescribed time period, within a prescribed performance impact, and/or within a prescribed fuel economy impact. T min  illustratively varies based on various system conditions. For example, T min  is be increased when an air flow rate through engine  12  is high, and/or when heat transfer to ambient from aftertreatment system  14  is high, such as in cold ambient temperatures, at high vehicle speeds, and in road splash conditions. Such conditions may be detected directly or inferred from temperature modeling and/or temperature feedback parameter comparisons. 
     In operation, controller  30  illustratively determines when T i  of aftertreatment system  14  is below or expected to fall below T min . (Block  205 ) In one embodiment, this determination is made based on information received directly from temperature sensor  40 . In another embodiment, this determination is made based on information received from an aftertreatment thermal support unit (not shown) in communication with temperature sensor  40 . If necessary, controller  30  takes corrective action to increase T i  of aftertreatment system  14  above T min . 
     According to an exemplary embodiment of the present disclosure, controller  30 , including slippage inducer  50 , controls slippage of clutch assembly  24  based on the above-described T i  of aftertreatment system  14 . Controlling slippage of clutch assembly  24  illustratively involves altering the pressure applied to clutch plate  26  of clutch assembly  24  against flywheel  28  of engine  12 . Controller  30  also controls slippage of clutch assembly  24  based on information from the engine speed sensor  42 , information from the vehicle speed sensor  44 , and/or other vehicle information. In such embodiments, such vehicle/engine speed sensor and other vehicle information is used to provide a confirmation of the conditions generated by the clutch setting instructed by controller  30 . Indeed, it is expected that vehicle conditions generated by a clutch setting will differ as clutch assembly  24  wears over time. Accordingly, vehicle sensors provide an avenue by which the desired settings and heat profile generated thereby can be monitored and confirmed or adjusted. 
     When T i  of aftertreatment system  14  is below or expected to fall below T min , (Block  210 ) controller  30  attempts to increase T i  by causing slippage in clutch assembly  24 . If clutch plate  26  is fully engaged with flywheel  28 , controller  30  decreases the pressure on clutch plate  26  to a partial pressure to loosen clutch plate  26  relative to flywheel  28  and allow slippage between clutch plate  26  and flywheel  28  (Blocks  215 ,  220 ,  225 ,  230 ,  235 ). As discussed above, the slipping clutch assembly  24  transfers some of the power from engine  12  to the motive elements of the vehicle. However, the slipping clutch assembly  24  increases the power demand on engine  12  due to the power that dissipates when the clutch plate  26  slips past the flywheel  28 . The slipping clutch assembly  24  also increases the temperature of any fluid surrounding the clutch assembly  24 . As a result, the temperature of the exhaust gases from engine  12 , and ultimately T i  of aftertreatment system  14 , increases. When T i  of aftertreatment system  14  is sufficiently high, controller  30  returns the clutch plate  26  into normal engagement with flywheel  28  (Block  245 ). It should be appreciated that there is a minimum amount of engagement (maximum induced slippage) that is permitted during running operation. In one embodiment, when T i  of aftertreatment system  14  is determined to be above a reference temperature, then controller  30  reduces the induced slippage, eventually returning the clutch plate  26  into normal engagement with flywheel  28 . In another embodiment, when T i  is greater than T min  controller  30  determines if any artificial slippage is being directed. If so, then such induced slippage is reduced. This continues until all induced slippage is removed and engine  12  and aftertreatment system  14  is able to continue normal operation. 
     In one embodiment, controller  30  provides varying levels of slippage based on T i  of aftertreatment system  14 . For example, controller  30  provides more slippage (e.g., 85% engagement) when T i  is low and less slippage (e.g., 95 % engagement) as T i  increases toward T min . Thus, in one embodiment, when T i  is below T min  and below another intermediate reference temperature (T Int ) (Block  215 ) a setting of maximum slippage is illustratively instructed (Block  230 ). Upon detecting T i  above T Int , but still below T min , a second lower amount of slippage is illustratively called for (Block  220 ). It should be appreciated that while only one intermediate temperature and slippage setting is discussed, embodiments are envisioned where multiple gradations are used. Also, once the minimum temperature is achieved, any induced slippage (Block  240 ) is reduced (Block  245 ) until the induced slippage is fully removed. In one example, controller  30  adjusts slippage by reducing slippage in response to detecting that the temperature has risen relative to a previously detected temperature. Furthermore, once a slippage adjustment is ordered, controller  30  waits a delay time (Blocks  225 ,  235 ,  250 ) and then determines the temperature or expected temperature again (Block  205 ). 
     Controller  30  also controls T i  of aftertreatment system  14  by, for example, commanding engine  12  to run at a higher speed idle condition, providing post fuel injection, increasing an exhaust gas recirculation (“EGR”) fraction, bypassing all or a portion of an EGR cooler, bypassing all or a portion of a charge air cooler, increasing a back pressure on engine  12  with a variable geometry turbocharger (“VGT”), changing valve timing to reduce an engine air flow rate, increasing an accessory load on engine  12 , and/or reducing heat transfer to an engine radiator. 
     Other aspects of system  10  may be found in International Patent Application No. PCT/US2014/016818, entitled “System, Method, and Apparatus for Managing Aftertreatment Temperature,” filed Feb. 18, 2014, the disclosure of which is expressly incorporated herein by reference in its entirety. 
     It should be appreciated that while certain functionality and properties are discussed herein with respect to controller  30  and with respect to slippage inducer  50 , it is understood that there is not intended to be a bright line between the two. Indeed, slippage inducer  50  is illustratively part of controller  30  and features attributed to controller  30  are further understood to be attributed to slippage inducer  50  in certain embodiments. 
     While this invention has been described as having exemplary designs, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.