Abstract:
Systems and methods for providing auxiliary power to a large diesel engine allow shutdown of the engine in various weather conditions. An auxiliary power unit (APU) comprising a secondary engine coupled to an electrical generator is provided. An automatic control system shuts down the primary engine after a period of idling, and the APU provides electrical power for heating and air conditioning. The APU automatically starts in response to a low coolant temperature, low battery voltage, and low air reservoir pressure. It may also start automatically after extended shutdown to ensure reliability. Automatic primary engine shutdown is defeated if the secondary engine is disabled.

Description:
[0001]    This application is a continuation-in-part of co-pending U.S. patent application Ser. No. 09/773,072, entitled SYSTEM AND METHOD FOR SUPPLYING AUXILIARY POWER TO A LARGE DIESEL ENGINE, filed Jan. 30, 2001, the contents of which are incorporated herein by reference. 
     
    
     
       BACKGROUND  
         [0002]    1. Field  
           [0003]    Embodiments of the present invention relate to large engine systems.  
           [0004]    2. Description of Related Art  
           [0005]    In diesel fuel powered transportation environments, extremely cold temperatures adversely affect diesel engine operation. Generally, large diesel engines, such as locomotive engines, are not shut down during cold weather conditions due to the difficulty in restarting. Diesel engines do not have the benefit of an electric spark to generate combustion and must rely on heat generated by compressing air to ignite fuel in the engine cylinders.  
           [0006]    In low temperature conditions (ambient temperatures below about 40° F.), various factors contribute to the difficulty in starting a diesel engine. First, cold ambient air drawn into the engine must be increased in temperature sufficiently to cause combustion. Second, diesel fuel tends to exhibit poor viscous qualities at low temperatures. Furthermore, engine oil that provides lubrication for an engine is most effective within specific temperature limits, generally corresponding to normal operating temperature of the engine. When cold, the engine lube-oil tends to impede engine starting. Moreover, most engines require a large electrical supply, typically provided by a battery, in order to turn over and start the engine. Batteries are also adversely affected by severe cold weather.  
           [0007]    In cold weather, large engines are typically idled overnight to avoid the need to restart in the morning and to provide heat to the crew space. Locomotives that must operate in extremely cold environmental conditions must be run continuously, at high fuel cost, or, when shut down, must be drained of engine coolant and provided with supplemental electrical service and heaters, also at high cost. To avoid engine damage, locomotives typically include a dump valve that activates if the engine coolant comes close to freezing by dumping all of the engine coolant. If a locomotive dumps its main engine coolant, a tank car or tank truck must replenish the coolant prior to restarting of the locomotive, creating delays and increased costs.  
           [0008]    In warm weather, locomotive engines typically idle to provide air conditioning and other services, including lighting, air pressure, and power to electrical appliances. If a locomotive is shut down, solid-state static inverters that transform dc power from the locomotive batteries to useful ac power can provide electrical power for air conditioning and other services. Devices such as inverters are parasitic loads that tend to drain the batteries, which may adversely affect engine reliability. Alternatively, wayside electrical power can be supplied, but such power generally does not maintain air conditioning.  
           [0009]    Long term idling of large diesel engines results in additional deleterious effects. For example, large diesel engines are susceptible to “wet stacking” due to piston ring leakage caused by idling for long periods of time in cold weather. Moreover, long term idling is economically inefficient, resulting in primary engine wear, and high fuel and lube-oil consumption, for example.  
           [0010]    Several systems have attempted to maintain warmth in a large diesel engine under low temperature ambient conditions. For example, U.S. Pat. No. 4,424,775 discloses an auxiliary engine for maintaining the coolant, lube-oil, and batteries of a primary diesel engine in restarting condition by using the heat of the auxiliary engine exhaust to keep coolant, lube-oil, and batteries sufficiently warm. U.S. Pat. No. 4,762,170 discloses a system for facilitating the restarting of a truck diesel engine in cold weather by maintaining the fuel, coolant, and lube-oil warm through interconnected fluid systems. U.S. Pat. No. 4,711,204 discloses a small diesel engine for providing heat to the coolant of a primary diesel engine in cold weather. The small engine drives a centrifugal pump with restricted flow such that the coolant is heated and then pumped through the primary cooling lines in reverse flow. In such systems, an electrical generator or inverter may be included to maintain a charge for the batteries.  
           [0011]    U.S. Pat. No. 5,072,703 discloses an apparatus for restarting a truck diesel engine to maintain a comfortable sleeper compartment temperature. Inputs require that the truck be parked prior to restarting the engine. U.S. Pat. No. 4,577,599 discloses a remote starter for an internal combustion engine that adjusts fuel and air input to the engine based upon engine speed and temperature.  
         SUMMARY  
         [0012]    An object of embodiments of the present invention is to enable a reliable auxiliary power supply system to allow for shutting down a primary diesel engine in all weather conditions.  
           [0013]    Another object is to enable a control system that automatically shuts down a primary engine after a certain predetermined period of time, regardless of ambient temperature.  
           [0014]    Another object is to enable a control system that automatically starts an auxiliary power supply system having a secondary engine to maintain a primary engine warm in response to a predetermined temperature.  
           [0015]    Another object is to enable a control system that maintains fuel, coolant, and lube-oil of a primary engine at a sufficiently warm temperature to facilitate restarting such primary engine in cold weather.  
           [0016]    Yet another object is to control starting of a secondary engine based on a variety of conditions. A more specific object is to enable starting of the secondary engine based on an air pressure condition. Another specific object is to enable starting of the secondary engine based on a battery voltage condition. A further specific object is to enable starting of the secondary engine based on inactive time of the secondary engine.  
           [0017]    Another object is to isolate a primary engine&#39;s batteries when such primary engine is shut down to prevent discharge of the batteries. A more specific object is to provide an electrical generator for charging the primary engine&#39;s batteries, as well as for generating standard 240 vac and 120 vac to permit the use of non-vital and hotel loads.  
           [0018]    Still another object is to enable a system that disables automatic shutdown features when an auxiliary power supply system is not available to protect the primary engine.  
           [0019]    Embodiments of the present invention enable an improved system for providing heating or cooling and electricity to a railroad locomotive in all operating environments, and saves locomotive fuel and lubricating oil. Embodiments herein may further reduce engine emissions by more than 95% and may allow a locomotive operator to obtain EPA (Environmental Protection Agency) credits. An auxiliary power unit comprising a diesel engine coupled to an electrical generator is installed in a locomotive cab. In an embodiment, the engine may be a turbo-charged, four-cylinder diesel engine, such as one manufactured by Kubota, and rated at about 32 brake horsepower, at 1800 RPM. The auxiliary unit engine can draw fuel directly from the main locomotive fuel tank. Equipping the auxiliary unit with a 20-gallon lube-oil sump and recirculating pump to permit extended oil change intervals may reduce maintenance of such auxiliary unit engine. For protection of the auxiliary unit engine, it may also be equipped with over-temperature and low lube-oil pressure shutdowns to prevent engine damage in the event that the engine overheats or runs low on lube-oil.  
           [0020]    In an embodiment, the electrical generator may be a 17 kva, 240 vac/60 Hz single-phase generator, mechanically coupled to such engine. A 240 vac/74 vdc battery charger, such as a Lamarche A-40 locomotive battery charger, is provided to maintain the locomotive batteries charged whenever the auxiliary unit is operating.  
           [0021]    Embodiments of the present invention allow for automatic shutdown of a primary engine instead of extended idling operation while maintaining a charge on the primary engine&#39;s battery. Embodiments of the present invention allow for the operation of cab air conditioning while the primary engine is shut down. Embodiments provide electrical power in standard household voltages for hotel and non-vital loads, allowing for the installation and use of commonly available electrical devices without the need to maintain the primary engine operating. Embodiments provide power to an air compressor without requiring the primary engine to start, and only respond to air pressure signals if a train is attached to the locomotive. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0022]    [0022]FIG. 1 is a schematic overview of components of an embodiment of the present invention.  
         [0023]    [0023]FIG. 2 is a flowchart of a process according to an embodiment of the present invention.  
         [0024]    [0024]FIG. 3 is a partial flowchart of a process according to an embodiment of the present invention relating to air control operation.  
         [0025]    [0025]FIG. 4 is a partial flowchart of a process according to an embodiment of the present invention relating to battery voltage control operation.  
         [0026]    [0026]FIG. 5 is a partial flowchart of a process according to an embodiment of the present invention relating to inactive time control operation.  
         [0027]    [0027]FIG. 6 is a functional schematic diagram of inputs to defeat the primary engine idle time features of a system according to an embodiment of the present invention.  
     
    
     DETAILED DESCRIPTION  
       [0028]    Referring now to the drawings, there is presented a system overview of an exemplary embodiment of the present invention. In a specific embodiment, illustrated in FIG. 1, primary locomotive engine  10  includes an integral cooling system having radiator  13  for dissipating heat absorbed from primary locomotive engine  10  and support components such as lube-oil cooler  15 . The flow path of coolant forms a closed loop. Such coolant flows through conduits, such as conduit  22 , to oil cooler  15  wherein heat is transferred from lubricating oil. Such coolant reenters primary locomotive engine  10  at a suitable location, such as strainer housing  27 . Engine coolant drain line  28  may enable removal of coolant during cold weather to prevent freeze damage, if necessary.  
         [0029]    Locomotive engine lube-oil provides lubrication for locomotive engine  10  and helps remove heat of combustion. Such lube-oil transfers heat to the locomotive coolant in oil cooler  15  and returns to primary locomotive engine  10  in a closed loop. Filter drain line  30  connects to a suitable location, such as strainer housing  27 , and may enable draining of oil from the system during periodic maintenance. During periodic oil changes, lube-oil may be drained from the entire system through a lube-oil drain  33 .  
         [0030]    In accordance with embodiments of the present invention, there is provided an auxiliary power unit (APU)  45 , comprising a secondary engine  46  having an electrical generator  48  mechanically coupled to such secondary engine  46 . Secondary engine  46  draws fuel directly from the locomotive engine fuel tank through a common fuel supply for primary locomotive engine  10  at fuel connections  51 ,  52 . Secondary engine  46  includes a separate closed loop coolant system  55  including heat exchanger  57 , which is designed to transfer heat generated by operation of secondary engine  46  to a system designed to maintain primary locomotive engine  10  warm.  
         [0031]    Two auxiliary loops may be provided to maintain primary locomotive engine  10  warm in cold environmental conditions utilizing two pumps  62 ,  65 . Pump  62  is used for conditioning of coolant. Pump  65  is used for conditioning of lube-oil. The inlet of pump  62  is operatively connected by a conduit to a suitable location in the coolant system of primary locomotive engine  10 . The inlet of pump  65  is operatively connected by a conduit to a suitable location in the lube-oil system of primary locomotive engine  10 . Coolant heater  68  augments heat exchanger  57  to add heat to primary engine coolant. Oil heater  70  in the lube-oil loop adds heat to locomotive engine lube-oil.  
         [0032]    The system of FIG. 1 and other embodiments may be operated in a variety of modes. FIG. 2 is a flowchart of an operational process according to an embodiment of the present invention. In one embodiment, APU  45  can be selected for operation locally at an engine control panel or remotely in the locomotive cab. Control logic may permit operation in any of three exemplary mode—“thermostat,” “cab,” and “manual”—described below.  
         [0033]    During normal operation of primary locomotive engine  10 , APU  45  is not in operation. An engine idle timer at task  200  determines if primary engine  10  has been idled for a predetermined period of idle operation, such as 30 minutes. After such period of inactivity, the mode of operation of APU  45  is determined.  
         [0034]    If APU  45  is selected to the “thermostat” mode, indicated at task  205 , automatic control features shut down primary engine  10  and isolate the primary engine batteries, as indicated at task  210 . The “thermostat” mode is an exemplary mode of operation for maintaining primary engine  10  warm during cold weather ambient conditions. In “thermostat” mode, the control system shuts down the primary engine  10  after a predetermined period of idle operation, such as 30 minutes.  
         [0035]    In response to a first predetermined condition  215 , such as low locomotive coolant temperature, low locomotive lube-oil temperature, or low air pressure, the secondary engine  46  will start  220  in order to warm primary engine systems and/or recharge air reservoir pressure. When a second predetermined condition  225 , such as the selected temperature or air pressure, exceeds an established set point, secondary engine  46  automatically shuts down  230 . In one embodiment, such condition may be engine coolant temperature as measured by a primary engine block thermostat, or alternate conditions as described below with reference to FIGS. 3, 4, and  5 .  
         [0036]    If APU  45  is selected to the “cab” mode, indicated at task  235 , automatic control features shut down primary engine  10  and isolate the primary engine batteries after a predetermined period of idle operation, as indicated at task  240 . The “cab” mode is an exemplary mode of operation for warm weather operation to maximize fuel savings by limiting idling operation of primary engine  10 . In “cab” mode, the control system may automatically shut down primary engine  10  after a predetermined period of idle operation, such as 30 minutes. An operator can start APU  45  manually as indicated at task  245 . APU  45  may remain responsive to operator command.  
         [0037]    In an alternate embodiment, a reset switch can be included in the control logic. Such switch requires that an operator confirm manual operation of APU  45  in “cab” mode. A timer determines the amount of run time of secondary engine  46 . After secondary engine  46  has operated for a predetermined time  250 , such as two hours, a warning signal  255  is generated. Such warning  255  can be audible, visual, or both, and in some embodiments may send a signal to a remote location. The operator can reset such timer at task  260 , in which case the APU  45  may continue to operate. Otherwise, after a predetermined time, such as five minutes after the warning, the secondary engine will shut down at task  230 .  
         [0038]    In “cab” mode, if an operator does not start secondary engine  46 , it may start automatically in response to a first predetermined condition, such as low coolant temperature, low lube-oil temperature, or low air pressure, and shut down when the selected condition exceeds an established set point as described for “thermostat” control above. In a further alternate embodiment, an override may be provided to permit extended idling operations at the discretion of the operator.  
         [0039]    The “manual” mode, indicated at task  265 , allows APU  45  to be started by manually priming secondary engine  46 . This provision may allow for operation of APU  45  in the event that automatic start up features malfunction, or to prime secondary engine  46  in the event that it runs out of fuel.  
         [0040]    In the described modes of operation, APU  45  may charge the primary engine batteries and provide power to thermostatically controlled cab heaters and 120 vac lighting and receptacles. In operation, when primary engine  10  is shut down automatically, an analog or solid state device (such as a relay or transistor) may automatically isolate the primary batteries from 74 vdc loads to prevent discharge of the locomotive batteries after a period of time following a main engine shutdown and during the shutdown period.  
         [0041]    In another embodiment, startup of APU  45  can be conditioned on a variety of parameters to protect the locomotive engine and minimize emissions. For example, if a stationary locomotive is alone or isolated, it may not be necessary to maintain air pressure for the train brakes. However, if such locomotive has a train behind it, then it may be important to maintain sufficient pressure in the brake pipe.  
         [0042]    [0042]FIG. 3 is a partial flowchart of a process according to an embodiment of the present invention. In the embodiment of FIG. 3, APU  45  is started by air pressure. Entry point A and exit point B correspond to like notations in FIG. 2 concerning first and second predetermined conditions.  
         [0043]    If secondary engine  46  is not running at task  300 , then the control logic checks to see if the air compressor breaker is shut. This task may be omitted if the secondary engine  46  mechanically drives the air compressor. If the breaker is shut, then the reservoir air pressure is checked to determine if such pressure is below a predetermined setpoint and is decreasing  310 . The pressure in the train brake pipe is checked to determine if pressure is between approximately 60 psi and approximately 75 psi at task  315 . Train brake pipe pressure may only be within this band if a train is attached to the locomotive. If all the conditions are met, APU  45  is started at task  220 . The control logic will only start the APU  45  due to air pressure in order to charge the air reservoir if a train is attached to the locomotive.  
         [0044]    Once APU  45  is operating, it may stay running to warm the coolant and lube-oil or charge the primary batteries. If any of the temperature or voltage conditions are not met at task  325 , the APU continues to operate. If other conditions are met, then the control logic checks to determine if a train is attached at task  330 . If not, the APU is shut down  230 . Otherwise, a check is made to determine if the air reservoir pressure has risen above a predetermined setpoint  335 . When air pressure is restored, APU  45  can be shut down  230 .  
         [0045]    Primary engine  10  cannot be started if the primary batteries have insufficient voltage. FIG. 4 is a partial flowchart of a process according to an embodiment of the present invention. In the embodiment of FIG. 4, APU  45  is started by low voltage on the primary batteries. Entry point A and exit point B correspond to like notations in FIG. 2 concerning first and second predetermined conditions.  
         [0046]    If secondary engine  46  is not running at task  300 , then the control logic checks to determine if the voltage on the primary batteries is below a predetermined level at task  340 . If so, the secondary engine  46  is started at task  220 .  
         [0047]    Once APU  45  is operating, it may stay running to warm the coolant and lube-oil or recharge the air reservoir. If any of the temperature and pressure conditions are not met at task  325 , the APU continues to operate. If other conditions are met, then the control logic checks to determine if the primary batteries are recharged  345 . When battery voltage is restored, APU  45  can be shut down  230 .  
         [0048]    To keep the primary engine  10  safe and ensure that APU  45  will start when required for cold weather protection or to maintain brake pipe air pressure, secondary engine  46  may be periodically operated for brief periods to detect any potential difficulties.  
         [0049]    [0049]FIG. 5 is a partial flowchart of a process according to an embodiment of the present invention. In the embodiment of FIG. 5, inactive time control operation of the system is implemented. Entry point A and exit point B correspond to like notations in FIG. 2 concerning first and second predetermined conditions.  
         [0050]    If secondary engine  46  has been inactive for a predetermined period of time, such as  48  hours or  72  hours, as indicated at task  350 , then APU  45  can be automatically started based on time  220 . In such a case, secondary engine  46  may be operated for a predetermined period of time, such as 30 minutes to an hour (task  355 ), to allow temperatures in secondary engine  46  to stabilize and enable sufficient time for an operator or automated verification mechanism, such as a processor, to verify correct running of the system.  
         [0051]    Once APU  45  has been operating for a predetermined period of time, it may stay running to warm the coolant and lube-oil, recharge the air reservoir, and/or charge the primary batteries. If any of the conditions are not met at task  325 , the APU continues to operate. If other conditions are met, secondary engine  46  is shut down  230 .  
         [0052]    In an alternate embodiment, external audible and visual alarms can sound and light if APU  45  fails to start during any automatically initiated attempt to start. These alarms may be battery operated so they are not reliant on the secondary engine running. In an exemplary implementation, such alarms may include a wireless communication system to connect to a remote operator center.  
         [0053]    If APU  45  is not available to protect primary engine  10 , then it may not be safe to automatically shut down primary engine  10 . FIG. 6 is a functional schematic diagram of inputs to defeat the primary engine idle time features of a system according to an embodiment of the present invention.  
         [0054]    Main engine shutdown device  400  normally receives power from 74 vdc primary batteries. Sensor input to the shutdown device  400  comprises an idle sensor  405 , and output of the shutdown device  400  goes to fuel pump relay  407 , to stop fuel to the primary engine  10 . Idle shutdown is defeated when the APU emergency stop switch  410  is activated, if the APU mode selector switch  415  is selected to “OFF,” or if power is removed from the APU automatic start at its circuit breaker  420 . By integrating such exemplary inputs, the primary engine may be protected from automatic shutdown if the APU is not available.  
         [0055]    It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the invention as shown in the specific embodiments without departing from the spirit or scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.  
         [0056]    While specific values, relationships, materials and steps have been set forth for purposes of describing concepts of the invention, it should be recognized that, in the light of the above teachings, those skilled in the art can modify those specifics without departing from basic concepts and operating principles of the invention taught herein. Therefore, for purposes of determining the scope of patent protection, reference shall be made to the appended claims in combination with the above detailed description.