Abstract:
The present invention provides an apparatus and method of operating a refrigeration system. The apparatus and method includes providing a fuel pressure monitoring device that is disposed along a fuel line, automatically shutting down the engine if the fuel pressure meets a first condition, restarting the engine, and operating the engine in an unrestricted mode if the fuel pressure monitoring device records a second condition and shutting down the engine if the fuel pressure monitoring device does not record the second condition. An apparatus and method of operating a diesel engine of a refrigeration system that is coupled to an inline fuel injection system is also disclosed.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    This invention relates to refrigeration systems and, more particularly, to fuel systems for refrigeration systems.  
           [0002]    Refrigeration systems often incorporate a diesel engine to drive the compressor and blower components. Diesel engines operate by compressing a quantity of air in a cylinder and then injecting fuel into the compressed air. The heat of the compressed air spontaneously ignites the fuel, causing the cylinder volume to expand and drive a shaft.  
           [0003]    A number of fuel injection systems are known to exist for introducing fuel into the cylinder in a diesel engine. In a distributor type injection system, a single injector pump and plunger mechanism move the fuel from the fuel filter to a distributor that distributes the fuel to the cylinders in proper sequence and time. In an inline-injection type system, each cylinder is associated with its own injection pump and plunger mechanism. A camshaft with a timing device drives the plungers and introduces fuel into the cylinders in the proper sequence and at the proper time.  
           [0004]    Diesel engines can be difficult to start if the fuel line contains an excess of air. Air can get into the fuel line when the fuel level drops to the point where the fuel pump receives air. In this situation, the engine typically will not start until the air is removed from the fuel line. To do this, diesel fuel systems commonly include a mechanism for bleeding the air out of the fuel line.  
           [0005]    Diesel fuel injection systems, particularly those with inline fuel injection systems, commonly do not exhibit symptoms of low fuel prior to air being drawn by the fuel pump. The engine typically will die suddenly, without exhibiting any fluctuations or erratic RPM levels. When the engine shuts down, the engine will already have drawn a large quantity of air into the fuel line, making it difficult to restart the engine. This problem is especially prevalent when the refrigeration system is used in connection with a truck trailer where the truck driver cannot constantly monitor the fuel level.  
         SUMMARY OF THE INVENTION  
         [0006]    The present invention provides a method of operating a refrigeration system that includes a compressor driven by a diesel engine coupled to an inline fuel injection system, a fuel line connecting the fuel injection system to a fuel source, a fuel pump disposed along the fuel line for drawing fuel from the fuel source to the fuel injection system, and a fuel filter disposed along the fuel line. The method is designed to prevent the fuel pump from drawing excess air into the fuel line. The method includes providing a fuel pressure monitoring device disposed along the fuel line, automatically shutting down the engine if the fuel pressure monitoring device records a first condition, restarting the engine in a restricted mode, operating the engine in an unrestricted mode if the fuel pressure monitoring device records a second condition, and shutting down the engine if the fuel pressure monitoring device does not record the second condition.  
           [0007]    The invention further yet provides a refrigeration system including a diesel engine, a compressor driven by the diesel engine, an inline injection system coupled to the diesel engine through a fuel line, a fuel source connected to the inline injection system via the fuel line, a fuel pump disposed along the fuel line for drawing fuel from the fuel source to the fuel injection system, a fuel filter disposed along the fuel line between the fuel pump and the inline injection system, a fuel pressure monitoring device disposed along the fuel line, a fuel solenoid operatively coupled to the inline injection system to selectively enable fuel to enter the engine, and a controller operatively coupled to the fuel pressure monitoring device and the fuel solenoid to receive an input from the fuel pressure monitoring device and control the fuel solenoid according to the input.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]    [0008]FIG. 1 shows a schematic diagram of a preferred embodiment of a refrigeration system according to the present invention;  
         [0009]    [0009]FIG. 2 shows the refrigeration system of FIG. 1 mounted to a truck trailer;  
         [0010]    [0010]FIG. 3 shows a schematic diagram of the refrigeration system of FIG. 1; and  
         [0011]    [0011]FIG. 4 shows a flow chart illustrating a preferred method in the form of a computer program that can be used to practice the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0012]    Referring to FIGS. 1 and 2, a preferred embodiment of a refrigeration system  20  utilizing the present inventive method and apparatus is illustrated and controls the temperature of a conditioned space  21  to a specified temperature range that includes a thermal set point. One of ordinary skill in the art will recognize that many refrigeration systems may utilize the present inventive method and apparatus and that the illustrated refrigeration system  20  is for illustrative purposes only. The refrigeration system  20  is especially suitable for use in transport applications, and may be mounted on a transport vehicle, such as, for example, a container, a truck, or a trailer.  
         [0013]    The refrigeration system  20  has a closed fluid refrigerant circuit or flow path  24  that includes a refrigerant compressor  26  driven by a prime mover arrangement  28 . The illustrated prime mover arrangement  28  includes an internal combustion engine  30  and an optional stand-by electric motor  32 . The engine  30  and motor  32 , when both are utilized, are coupled to the compressor  26  by a suitable clutch or coupling  34 , which disengages the engine  30  while the motor  32  is operative.  
         [0014]    Discharge ports of the compressor  26  are connected to an inlet port of a three-way valve  36  via a discharge service valve  38  and a hot gas line  40 . The functions of the three-way valve  36 , which selects heating and cooling cycles, may be provided by two separate valves, if desired. The three-way valve  36  has a first outlet port  42  that is selected to initiate a cooling cycle with the first outlet port  42  being connected to the inlet side of a condenser coil  44 . The three-way valve  36  has a second outlet port  46  that is selected to initiate a heating cycle.  
         [0015]    When the three-way valve  36  selects the cooling cycle outlet port  42 , it connects the compressor  26  in a first refrigerant flow path  48 , which includes the condenser coil  44 , a one-way condenser check valve  45 , a receiver  50 , a liquid line  52 , a refrigerant drier  54 , a heat exchanger  56 , an expansion valve  58 , a refrigerant distributor  60 , an evaporator coil  62 , a compressor throttling valve  64 , a second path through the heat exchanger  56 , an accumulator  66 , a suction line  68 , and back to a suction port of the compressor  26  via a suction line service valve  70 . The compressor throttling valve  64  may be replaced by a controllable suction line modulation valve, as taught by U.S. Pat. No. 4,977,751, which is assigned to the same assignee as the present application, to protect the operative prime mover against overload. The expansion valve  58  is controlled by a thermal bulb  71  and an equalizer line  73 .  
         [0016]    When the three-way valve  36  selects the heating cycle outlet port  46 , it connects the compressor  26  in a second refrigerant flow path  72 . The second refrigerant flow path  72  by-passes the condenser coil  44  and the expansion valve  58 , connecting the hot gas output of the compressor  26  to the refrigerant distributor  60  via a hot gas line  74  and a defrost pan heater  76 . A hot gas by-pass solenoid valve  77  may optionally be disposed to inject hot gas into the hot gas line  74  during a cooling cycle. A by-pass or pressurizing line  78  connects the hot gas line  74  to the receiver  50  via by-pass and check valves  80 , to force refrigerant from the receiver  50  into an active refrigerant flow path during heating and defrost cycles.  
         [0017]    A conduit or line  82  connects the three-way valve  36  to the low pressure side of the compressor  26  via a normally closed pilot solenoid valve  83 . When the solenoid valve  83  is de-energized and thus closed, the three-way valve  36  is spring biased to select the cooling cycle outlet port  42 . When the evaporator coil  62  requires defrosting, and when a load being conditioned in the conditioned space  21  requires heat to maintain thermal set point, the pilot solenoid valve  83  is energized and the low pressure side of the compressor  26  operates the three-way valve  36  to select the heating cycle outlet port  46  to initiate a heating cycle or a defrost cycle.  
         [0018]    A condenser fan or blower (not shown), which may be driven by the prime mover arrangement  28 , causes ambient air  84  to flow through the condenser coil  44 , with the resulting heated air  86  being discharged to the atmosphere. A bulkhead  85  can preferably run the entire height of the load space  21 , however, this is not necessary. A return air port  89  disposed at the bottom of the bulkhead  85  and a discharge air port  91  disposed at the top of bulkhead  85  define a return air path and discharge air path, respectively. An evaporator fan or blower  87 , which also may be driven by the prime mover arrangement  28 , draws return air through the return air port  89  and discharges conditioned cooled or heated air into the load space  21 . A defrost damper  93  is disposed in the discharge air port  91  and may be closed during an evaporator defrost cycle.  
         [0019]    A controller  94  controls the refrigeration system  20  and includes a microprocessor based controller  96 , electrical control circuits and components  98 , and a number of sensors, relays, solenoids, and the like. The microprocessor  96  can sample data collected at these temperature sensors at a rate of ten samples per second, however, other rates of sampling can be used and still be within the spirit and scope of the present invention. The microprocessor  96  also controls the throttling valve  64 , the hot gas valve  77 , and a throttle or high speed solenoid  120  that selects high and low operating speeds of engine  30 .  
         [0020]    Referring to FIG. 3, a preferred embodiment of the present invention is schematically shown. The compressor  26  is driven by the diesel engine  30 , which is capable of operating at variable speeds, such as, for example, a low speed and a high speed. The low speed and high speed of the engine  30  is determined by the opening and closing of the throttle or high speed solenoid  120 , which is operatively connected to the microprocessor  96 .  
         [0021]    Fuel is introduced into the cylinders of engine  30  by an inline fuel injection system  124 . A fuel pump  126  supplies fuel to the fuel injection system  124  from a fuel source  128  via a fuel line  130 . In a preferred embodiment when the fuel in the fuel source  128  is not low, fuel pressure in the fuel line  130  is around  12  psi when the engine  30  is operating at high speed and is around  7  or  8  psi when the engine  30  is operating in low speed. However, one of ordinary skill in the art will recognize that other operating parameters are suitable. A fuel filter  132  is disposed along the fuel line  130  between the fuel pump  126  and the fuel injection system  124 . A pressure monitoring device or pressure switch  134  is preferably disposed at the inlet of fuel filter  132  and is operatively connected to the controller  94  comprising the microprocessor  96  and the electrical control  98 . Although a pressure switch  134  is illustrated and described herein, any type of pressure monitoring device may be utilized and still be within the spirit and scope of the present invention. One of ordinary skill in the art will recognize that the pressure switch  134  can be disposed anywhere between the fuel pump  126  and fuel filter  132  to monitor fuel pressure. The illustrated microprocessor  96  is preferably a data acquisition sensor chip with at least one input and output receptor and capable of running delay and timer functions. In a preferred embodiment of the present invention, the microprocessor  96  runs a 15-second delay and a 2-minute timer function (discussed in greater detail below). However, the microprocessor  96  can run any delay or timer functions and still be within the spirit and scope of the present invention.  
         [0022]    An alarm  138  and fuel solenoid FS are also operatively connected to the controller  94 . An energized fuel solenoid FS enables the engine  30  to run and a de-energized fuel solenoid FS shuts the engine  30  down. In a preferred embodiment, the engine  30  runs in low speed when the fuel solenoid FS is energized. One of ordinary skill in the art will recognize that the controller  94  (including the microprocessor  96  and the electrical circuits and components  98 ), the pressure switch  134 , the alarm  138 , the fuel solenoid FS, and the throttle or high speed solenoid  120  can be utilized with any refrigeration system.  
         [0023]    Referring to FIG. 4, a flow chart illustrating a preferred method in the form of a computer program that can be used to practice the present invention is illustrated. The program starts at block  140 . From block  140 , the program proceeds to block  142  where the program determines if the engine  130  is running. If the engine  130  is not running (NO at block  142 ), the program returns to block  140 . If the engine  130  is running (YES at block  142 ), the program proceeds to block  144  where the program determines if the alarm  138  is set. If the alarm  138  is not set (NO at block  144 ), the program proceeds to block  148  where the program determines if the fuel pressure is less than or equal to a predetermined pressure value. In a preferred embodiment of the present invention, the predetermined pressure value is  2  psi, however, the predetermined pressure value can be any pressure value and still be within the spirit and scope of the present invention. If the fuel pressure is not less than or equal to the predetermined pressure value (NO at block  148 ), the program returns to block  140 . If the fuel pressure is less than or equal to the predetermined pressure value (YES at block  148 ), the program proceeds to a delay at block  150 . Upon the fuel pressure dropping below or equal to the predetermined pressure value, the pressure switch  134  closes and the delay initiates. In a preferred embodiment, the delay is about 15 seconds, however, the delay can be any period of time and still be within the spirit and scope of the present invention. From block  150 , the program proceeds to block  152  where the program determines if the fuel pressure is less than or equal to the predetermined pressure value. If the fuel pressure is not less than or equal to the predetermined pressure value (NO at block  152 ), the program returns to start at block  140 . The pressure switch  134  once again opens after the fuel pressure is above the predetermined pressure value. If the fuel pressure is less than or equal to the predetermined pressure value (YES at block  152 ), the program proceeds to block  154  where the engine  30  is shut down and alarm  138  is set. The controller  94  shuts down the engine  30  by de-energizing the fuel solenoid FS and sets the alarm  138  due to the low fuel pressure. From block  154 , the program returns to start at block  140 .  
         [0024]    Referring back to block  144 , if the alarm  138  is set (YES at block  144 ), the program proceeds to block  156  and the engine  30  is operating in a Restricted Mode. From block  156 , the program proceeds to block  158  where the engine  30  is put into high speed operation. The engine is put into high be by the microprocessor  96  relaying a signal to the throttle or high speed solenoid  120  to open, therefore, allowing more fuel into the engine. High speed operation of the engine  30  is intended to bring the fuel pressure above the predetermined pressure value in a relatively short period of time. From block  158 , the program proceeds to block  160  where a timer initiates. The timer provides a period of time in which the engine  30  can operate in high speed to bring the fuel pressure above the predetermined pressure value. In a preferred embodiment of the present invention, the timer is set for 2 minutes, however, the timer can be set for any period of time and still be within the spirit and scope of the present invention. From block  160 , the program proceeds to block,  162 , where the program determines if the timer is expired. If the timer is not expired (NO at block  162 ), the program proceeds to block  164  where the program determines if the fuel pressure is less than or equal to the predetermined pressure value. If the fuel pressure is less than or equal to the predetermined pressure value (YES at block  164 ), the program returns to block  162 . If the fuel pressure is not less than or equal to the predetermined pressure value (NO at block  164 ), the program proceeds to block  166  where the alarm  138  is cleared. At this point, the fuel pressure has been raised to an acceptable pressure (above the predetermined pressure value) by the engine  30  and the alarm  138  is automatically cleared by the controller  94 . From block  166 , the program proceeds to block  168  where the timer is cleared. From block  168 , the program proceeds to block  170  where the engine  30  returns to normal speed control. From block  170 , the program proceeds to block  171  where the engine  30  operates in an Unrestricted Mode. In the Unrestricted Mode, the pressure switch  134  is open and the fuel solenoid FS is energized as long as the fuel pressure is greater than the predetermined pressure value.  
         [0025]    Referring back to block  162 , if the timer is expired (YES at block  162 ), the program proceeds to block  172  where the program determines if the fuel pressure is less than or equal to the predetermined pressure value. If the fuel pressure is not less than or equal to the predetermined pressure value (NO at block  172 ), the program proceeds to block  166  and continues therefrom in a manner similar to that discussed above. If the fuel pressure is less than or equal to the predetermined pressure value (YES at block  172 ), the program proceeds to block  154  and the engine  30  is shut down and the alarm  138  remains set. At any point when the engine  30  is shut down due to low fuel pressure, the transport vehicle operator, e.g. the truck driver, can enable restart the engine  30  while the system is in shut down, however, the transport vehicle operator cannot clear the alarm  138 . The alarm  138  can only be cleared by the controller  94  after the fuel pressure rises above the predetermined pressure value within the period of time set into the timer. After the controller  94  clears the alarm  138 , the engine  30  changes from operating in the restricted mode to operating in the unrestricted mode.  
         [0026]    Although particular embodiments of the present invention have been shown and described, other alternative embodiments will be apparent to those skilled in the art and are within the intended scope of the present invention. Accordingly, it is intended that the invention should not be limited except as may be necessary in view of the appended claims.