Patent Publication Number: US-8973536-B2

Title: Engine compensation for fan power

Description:
TECHNICAL FIELD 
     The present disclosure relates to internal combustion engines. More particularly, the present disclosure relates to internal combustion engines with interconnected cooling systems. 
     BACKGROUND 
     Machines, such as motorgraders, wheel loaders, wheel dozers, track type tractors, track loaders, etc., are powered by internal combustion engines, such as, for example, diesel engines, that are connected to an engine cooling system. Generally, engine coolant is pumped from a reservoir to the engine, heated, provided to a radiator, cooled, and returned to the reservoir. The coolant flows through, and is heated within, various passages in the engine block; similarly, the coolant flows through, and is cooled within, various passages in the radiator. While there may be some radiative cooling, air is forced over the radiator to provide convective cooling. Machines use a cooling fan to provide air flow over the radiator to transfer heat from the coolant, such as, for example, a hydraulic fan, an electric fan, a belt-driven fan, etc. For example, a hydraulic cooling fan may be connected to a hydraulic circuit that includes a hydraulic pump powered by the engine. As a parasitic load, the hydraulic cooling fan draws power from the engine, and may consume a certain, noticeable percentage of the engine power output, such as, for example, 5%, 10%, 15%, etc. Reduced engine power output affects the performance of the machines, such as, for example, the drawbar performance of a motorgrader. 
     For a machine engine that provides power to intermittent loads, such as a manually-operated implement, as well as to parasitic loads, such as an automatically-operated electrical load, hydraulic load, etc., one known engine control method adjusts gross engine power to provide a predetermined net power to a main power recipient (MPR) component of the vehicle, such as, for example, a transmission system, drive train and the like. U.S. Pat. No. 6,842,689 discloses a method that determines a predetermined net power to be provided to the MPR component, determines parasitic and/or intermittent load power during operation, and adjusts gross engine power to provide the predetermined net power to the MPR component during operation. A method that adjusts gross engine power, generally, to compensate for parasitic loads, such as a hydraulic cooling fan, is desirable. 
     SUMMARY 
     One aspect of the present disclosure provides a method for controlling the power of an engine. The method includes determining a baseline fuel amount based on a speed of the engine, determining an engine cooling fan operating condition based on at least one engine operating parameter, determining an engine cooling fan command based on the engine cooling fan operating condition, determining an engine cooling fan power level based on an engine speed and the engine cooling fan command, determining an additional fuel amount based on the engine cooling fan power level, adding the additional fuel amount to the baseline fuel amount to create a compensated fuel amount, and providing the compensated fuel amount to the engine. 
     Another aspect of the present disclosure provides an engine system. The engine system includes an engine, a fuel system coupled to the engine, a cooling system, coupled to the engine, including a radiator and a hydraulic cooling fan coupled to a hydraulic pump, and an engine controller coupled to the engine, the fuel system and the hydraulic pump. The engine controller includes a processor adapted to perform a set of instructions that control the power of the engine which include determining an engine cooling fan operating condition based on at least one engine operating parameter, determining an engine cooling fan command based on the engine cooling fan operating condition, determining an engine cooling fan power level based on an engine speed and the engine cooling fan command, determining an additional fuel amount based on the engine cooling fan power level, adding the additional fuel amount to the baseline fuel amount to create a compensated fuel amount, and providing the compensated fuel amount to the engine. 
     Another aspect of the present disclosure provides a method for controlling the power of an engine that includes determining a baseline fuel amount for the engine, determining an increased fuel amount greater than the baseline fuel amount to compensate for cooling fan power, and providing the increased fuel amount to the engine. Yet another aspect of the present disclosure provides a method for controlling the power of an engine that includes determining a maximum fuel amount for the engine, determining a reduced fuel amount less than the maximum fuel amount to compensate for the difference between a maximum cooling fan power and an actual cooling fan power, and providing the reduced fuel amount to the engine. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side view of a machine, in accordance with an embodiment of the disclosure. 
         FIG. 2  is a schematic representation of certain components of an engine system, a fuel system and a cooling system for a machine, in accordance with the disclosure. 
         FIG. 3  presents hydraulic cooling fan compensation curves, in accordance with the present disclosure. 
         FIG. 4  presents a hydraulic cooling fan engine speed compensation curve, in accordance with the present disclosure. 
         FIG. 5  presents a hydraulic cooling fan altitude compensation curve, in accordance with the present disclosure. 
         FIG. 6  presents a flow chart depicting a method for controlling the power of an engine, in accordance with the present disclosure. 
         FIG. 7  presents a flow chart depicting another method for controlling the power of an engine, in accordance with the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     The disclosure will now be described with reference to the drawing figures, in which like reference numerals refer to like parts throughout. 
       FIG. 1  presents a side view of a machine  10 , in accordance with an embodiment of the present disclosure. While machine  10  is depicted in  FIG. 1  as a motorgrader, other types of machines, such as, for example, wheel loaders, wheel dozers, track type tractors, track loaders, etc., are also contemplated by the present disclosure. 
     Machine  10  includes a front frame  12  and a rear frame  14 , coupled together via an articulated hitch  16 . Alternatively, machine  10  may include a non-articulated mainframe. Front frame  12  is supported by a pair of articulated front wheels  26 , while rear frame  14  is supported by a pair of tandem rear wheels  28 . Alternatively, machine  10  may include a single pair of rear wheels, a pair of track assemblies, etc. Front frame  12  supports an operator cab  18 , while rear frame  14  supports an engine compartment  20 . Cab  18  houses the operator and includes one or more joysticks, control pods, foot pedals, operator displays, electronic control modules, etc., while engine compartment  20  houses an engine system, including an engine, an intake system, an exhaust system and an engine control system, as well as other engine support systems, such as, for example, a fuel system, a cooling system, a lubrication system, etc. A hydraulic system, including one or more hydraulic circuits, may also be housed within engine compartment  20 . The engine control system may include one or more microprocessor-based controllers that are coupled to the engine, intake and exhaust systems, as well as other support systems, and configured to control the function of these components. The cooling system may include a reservoir, a pump, a radiator and a hydraulic cooling fan coupled to, and powered by, a hydraulic circuit. Various hoses and lines connect the components of the cooling system to the engine. Other types of fans may be used within the cooling system, such as, for example, electric fans, belt-driven fans, etc. 
     Blade assembly  30  is coupled to a front portion of front frame  12  via drawbar  31 , and to a central portion of front frame  12  via linkage  33 . Various hydraulic actuators  34 , such as, for example, blade lift cylinders  35 , blade side shift cylinder, blade pitch cylinder, circle rotation cylinder, drawbar center shift cylinder, etc., articulate blade assembly  30  and blade  32  with respect to the ground. Optional work tools may include a ripper or scarifier  40  attached to rear frame  14 , and a dozer blade or counterweight  42  attached to front frame  12 . 
       FIG. 2  presents a schematic representation of certain components of an engine system, a fuel system and a cooling system for a machine, in accordance with the disclosure. 
     Engine system  50  may include an engine control module, engine control unit or engine controller  52 , an engine  54 , an intake system  56  and an exhaust system  58 . Engine controller  52  may include one or more microprocessors, volatile and non-volatile memory, and input and output ports that are connected to various sensors and actuators. Engine  54  may be an internal combustion engine, such as, for example, a diesel engine, a gasoline engine, a natural gas engine, etc., or any other gaseous fuel engine whose power at any given engine speed may be controlled by regulating the amount of fuel delivered to the engine by the fuel system  80 . In one embodiment, engine  54  may be a diesel engine including an engine block with four or more cylinders arranged in an “in-line” or “V” configuration. 
     One or more engine speed sensors, such as active single or dual Hall Effect sensors, measure the rotational speed of the engine crankshaft, or, alternatively, a drivetrain component, and are coupled to the engine controller  52 . In one embodiment, engine controller  52  controls engine power by varying the amount of fuel delivered to the engine cylinders, according to one or more engine performance curves or tables, correlating engine power or torque at different engine speeds to the required fuel quantity, which may be stored in memory. One or more atmospheric pressure sensors  53  may also be coupled to engine controller  52 , and may be disposed within the engine block, the enclosure, one or more electronic control modules (ECM), the intake system  56 , the engine air intake passages, etc. 
     Intake system  56  delivers air to the engine  54 , while exhaust system  58  directs combustion gases to the atmosphere. Fuel system  80  may include a fuel tank, one or more pumps, filters, etc., and various hoses and pipes to connect the fuel system components to the engine  54 . Similarly, lubrication system  82  may include an oil tank, one or more pumps, filters, etc., and various hoses and pipes to connect the lubrication system components to the engine  54 . 
     Cooling system  60  may include a cooling circuit  62 , at least one radiator  64  and a hydraulic cooling fan  66  powered by a constant displacement hydraulic motor  68 . Cooling system  60  may provide coolant to engine  54 , as well as to other support systems within engine system  50 . Additionally, other support systems, such as, for example, the lubrication system  82 , may include one or more radiators or heat exchangers within their respective fluid circuits, which may be serviced by the hydraulic cooling fan  66 . In other words, hydraulic cooling fan  66  may provide cooling air not only to radiator  64 , but also to one or more radiators within other support systems. 
     Hydraulic circuit  70  may include a solenoid-controlled variable displacement hydraulic pump  72  coupled to the hydraulic cooling fan  66  and a pressure sensor  74 , and a reservoir  76  coupled to the hydraulic pump  72  and the hydraulic cooling fan  66 . The solenoid of hydraulic pump  72  may be connected to the engine controller  52 , which controls the displacement of the hydraulic pump  72  by setting an electrical current provided to the solenoid. Alternatively, hydraulic circuit  70  may include a constant displacement hydraulic pump with a pressure bypass to control hydraulic cooling fan  66 . 
     INDUSTRIAL APPLICABILITY 
     Embodiments of the present disclosure advantageously provide methods that adjust engine power to compensate for hydraulic cooling fan loads. Additional embodiments adjust engine power to compensate for hydraulic cooling fan loads at different altitudes above sea level. While these methods offer engine performance improvements for machines, such as motorgraders, wheel loaders, wheel dozers, track type tractors, track loaders, etc., any engine system that includes a parasitic engine cooling fan load may benefit. 
     Engine power control may be facilitated through the use of engine power curves that provide the amount of fuel required to be delivered by fuel system  80  to produce a given engine power at various engine speeds. 
     Engine cooling requirements are determined by engine controller  52  based on temperature measurements, machine load determinations, etc., and include the desired operating speed of hydraulic cooling fan  66 . Generally, engine controller  52  adjusts the speed of hydraulic cooling fan  66  by commanding hydraulic pump  72  to a certain displacement, which provides a certain pressure within hydraulic circuit  70 . As discussed above, hydraulic pump  72  is solenoid controlled, so engine controller  52  determines and sets a current to the solenoid to change the displacement of hydraulic pump  72 . Since hydraulic cooling fan  66  is powered by a constant displacement hydraulic motor, the operating speed of hydraulic cooling fan  66  is proportional to the pressure within hydraulic circuit  70 . Advantageously, the operating speed of hydraulic cooling fan  66  is constant when the pressure within hydraulic circuit  70  is constant. Pressure sensor  74  measures the hydraulic pressure within hydraulic circuit  70 , and provides these data to engine controller  52 . Both open and closed loop control system architectures may be used. For example, a closed loop control system architecture may incorporate pressure sensor  74  data, while an open loop control system architecture, once calibrated, may not incorporate pressure sensor  74  data. 
     In known systems, the parasitic power consumed by hydraulic cooling fan  66  reduces the available engine power, which creates a commensurate reduction in machine performance, such as, for example, motorgrader drawbar performance. Adjusting the engine power upwards at a given engine speed, by increasing the amount of fuel provided to the engine  54 , compensates for this parasitic loss and recovers machine performance. In one example, the engine  54  may be operating at a given engine speed under a derated power curve, and additional power may be generated by increasing the fuel provided to engine  54  from the amount specified by the derated power curve up to the maximum fuel amount specified by the full power curve for that engine speed. The amount of the increase in fuel is based on a hydraulic cooling fan performance curve, which may be stored in the non-volatile memory of engine controller  52 . 
       FIG. 3  presents a hydraulic cooling fan power compensation curves  90  at sea level, in accordance with the present disclosure. Fan power compensation curves  90   a ,  90   b ,  90   c  present the amount of power consumed by the hydraulic cooling fan  66  as a function of engine speed for three different fan commands. Engine controller  52  determines the power consumed by the hydraulic cooling fan  66  at a given engine speed, converts the power to a torque value, estimates the additional fuel amount required to compensate for this torque value, and adds this additional fuel amount to the baseline fuel amount, determined by the particular engine power curve currently employed, to yield the compensated fuel amount. Operating engine  54  at a derated percentage of maximum engine power advantageously provides headroom to compensate for parasitic hydraulic cooling fan power losses. If the compensated fuel amount exceeds the maximum fuel amount provided by the full power curve, then the compensated fuel amount may be reduced to the maximum fuel amount to avoid exceeding full engine power. 
     Additionally, the effects of altitude on parasitic hydraulic cooling fan power losses may also be considered, either separately or in combination with the above methodology.  FIG. 4  presents a nominal hydraulic cooling fan power compensation curve  92 , in accordance with the present disclosure, while  FIG. 5  presents a hydraulic cooling fan altitude compensation curve  94 , in accordance with the present disclosure. 
     Fan power compensation curve  92  provides the amount of power consumed by the hydraulic cooling fan  66  as a function of engine speed for a nominal fan command, while fan altitude compensation curve  94  provides derate factors as a function of altitude. Pressure sensor  53  measures atmospheric pressure, and provides these data to engine controller  52 . When used separately from above methodology, engine controller  52  determines the power consumed by the hydraulic cooling fan  66  at the given engine speed and the altitude derate factor at the given altitude, multiplies these values together, converts the power to a torque value, estimates the additional fuel amount required to compensate for this torque value, and adds this additional fuel amount to the baseline fuel amount, determined by the engine power curve, to yield an altitude compensated fuel amount. If the compensated fuel amount exceeds the maximum fuel amount provided by the full power curve, then the compensated fuel amount may be reduced to the maximum fuel amount to avoid exceeding full engine power. 
     When used in conjunction with the above methodology, engine controller  52  determines the steady state power consumed by the hydraulic cooling fan  66  at the given engine speed and the altitude derate factor at the given altitude, multiplies these values together to produce an altitude compensated power, compares the sea level compensated power to the altitude compensated power, selects the minimum power, converts the minimum power to a torque value, estimates the additional fuel amount required to compensate for this torque value, and adds this additional fuel amount to the baseline fuel amount, determined by the engine power curve, to yield the compensated fuel amount. If the compensated fuel amount exceeds the maximum fuel amount provided by the full power curve, then the compensated fuel amount may be reduced to the maximum fuel amount to avoid exceeding full engine power. This method accounts for fan power when limited by the altitude air density or the fan controller system. 
       FIG. 6  presents a flow chart depicting a method  100  for controlling the power of an engine, in accordance with the present disclosure. 
     Engine controller  52  determines a baseline fuel amount  102  for engine  54 . Engine controller  52  may determine the baseline fuel amount by inspecting a derated engine power curve that includes fuel amount as a function of engine speed. 
     Engine controller  52  determines an engine cooling fan operating condition  104  based on at least one engine operating parameter. The engine operating parameter may be an engine speed, an engine block temperature, a transmission temperature, an air temperature, a coolant temperature, a hydraulic oil temperature, or various combinations of these parameters. The engine cooling fan operating condition may be the speed of the hydraulic cooling fan  66 , or, alternatively, the engine cooling fan operating condition may be the pressure within hydraulic circuit  70 , as measured by pressure sensor  74 . The operating condition may be expressed as percentage, such as, for example, 70%. 
     Engine controller  52  determines an engine cooling fan command  106  based on the engine cooling fan operating condition. The hydraulic cooling fan  66  may be connected to a constant displacement hydraulic motor  68  that is coupled to a solenoid-controlled variable displacement hydraulic pump  72 . As discussed above, because hydraulic cooling fan  66  is powered by a constant displacement hydraulic motor  68 , the operating speed of hydraulic cooling fan  66  is proportional to the pressure within hydraulic circuit  70 . Engine controller  52  adjusts the speed of hydraulic cooling fan  66  by commanding hydraulic pump  72  to a certain displacement, which provides a certain pressure within hydraulic circuit  70  that is associated with the desired operating speed of the hydraulic cooling fan  66 . The relationship between hydraulic cooling fan operating speed and hydraulic circuit pressure may be set forth in a curve or table stored in non-volatile memory in engine controller  52 . Engine controller  52  may also close a control loop around the pressure in the hydraulic circuit  70  using the measured pressure provided by pressure sensor  74 . In one embodiment, the engine cooling fan command  106  is a solenoid current that is based on the calculated pressure. 
     Engine controller  52  determines an engine cooling fan power level  108  based on the engine speed and the engine cooling fan command. For example, engine controller  52  may inspect fan power compensation curve  90   b , which may be a nominal fan command, for consumed power level based on the engine speed. Alternatively, the engine cooling fan power level  108  may be determined from the pressure measured by pressure sensor  74  and the fan speed or hydraulic pump displacement. 
     Engine controller  52  determines an additional fuel amount  110  based on the engine cooling fan power level. Engine controller  52  may convert the consumed power level to an engine torque value by dividing the power level by the operating speed of the engine  54 . Engine controller  52  then determines or estimates the additional fuel amount based on the torque value by consulting a curve or table stored in non-volatile memory in engine controller  52 , or, alternatively, by direct calculation. 
     Engine controller  52  adds the additional fuel amount  111  to the baseline fuel amount to produce a compensated fuel amount. 
     Engine controller  52  then provides the compensated fuel amount  112  to the engine  54 . More particularly, engine controller  52  provides control signals to engine  54  and/or fuel system  80  to provide the compensated fuel amount to engine  54 . 
     Additionally, engine controller  52  may determine a maximum fuel amount  114  based on the speed of the engine  54 , compare the compensated fuel amount to the maximum fuel amount  116 , and if the compensated fuel amount is greater than the maximum fuel amount, reduce the compensated fuel amount to the maximum fuel amount  118 . Engine controller  52  may determine the maximum fuel amount by inspecting the full power curve. 
       FIG. 7  presents a flow chart depicting another method  120  for controlling the power of an engine, in accordance with the present disclosure. Method  120  is an extension of method  100 , and the symbol “A” in a circle links methods  100  and  120  depicted in  FIGS. 6 and 7 , respectively. In this feature, the engine cooling fan power level calculated in method  100  is a sea level compensated power level. 
     Engine controller  52  determines a steady state engine cooling fan power level  122  based on the engine speed. Engine controller  52  may inspect fan power compensation curve  92  for the steady state engine cooling fan power level. 
     Engine controller  52  determines a derate factor  124  based on an altitude of the engine. Engine controller  52  may inspect fan altitude compensation curve  94  for the derate factor. Engine controller  52  multiplies the derate factor and the steady state power level to produce an altitude compensated power level  126 . Engine controller  52  compares the sea level compensated power level to the altitude compensated power level and selects the minimum power level  128 . Engine controller  52  then converts the minimum power level to a minimum torque value  130 , as described above. Engine controller  52  estimates the additional fuel amount required to compensate for the minimum torque value  132 . 
     Generally, the present disclosure advantageously provides methods for controlling the power of an engine. For example, one method for controlling the power of an engine includes determining a baseline fuel amount for the engine, determining an increased fuel amount greater than the baseline fuel amount to compensate for cooling fan power, and providing the increased fuel amount to the engine. Another method for controlling the power of an engine includes determining a maximum fuel amount for the engine, determining a reduced fuel amount less than the maximum fuel amount to compensate for the difference between a maximum cooling fan power and an actual cooling fan power, and providing the reduced fuel amount to the engine. 
     The many features and advantages of the present disclosure are apparent from the detailed specification, and, thus, it is intended by the appended claims to cover all such features and advantages of the present disclosure which fall within the true spirit and scope of the present disclosure. Further, since numerous modifications and variations will readily occur to those skilled in the art, it is not desired to limit the disclosure to the exact construction and operation illustrated and described, and, accordingly, all suitable modifications and equivalents may be resorted to that fall within the scope of the present disclosure.