Abstract:
A method and apparatus is disclosed for starting and stopping a generator set that supplies power to a refrigeration system. An ambient temperature sensor is used rather than an in-box sensor in addition to a programmed microprocessor to regulate the operation of the generator. Unnecessary use of the generator is, thereby, limited which contributes to cost, energy and equipment savings and a cleaner environment while ensuring the required in-box temperature is maintained and the quality of perishable goods are not compromised.

Description:
BACKGROUND OF THE INVENTION  
       [0001]    The present invention relates generally to a method of controlling a refrigeration system. More particularly, the invention relates to a method of controlling the start/stop of a generator that powers a refrigeration system used on containers transporting frozen goods via rail or roadway. 
         [0002]    It is common in the field of transport refrigeration to control the start/stop of the generator and thereby, the compressor (refrigeration system) and circulating fans by monitoring the temperature of the inside of the container with an in-box temperature sensor. 
         [0003]    In a typical system, frozen goods at 0 degrees Fahrenheit are loaded into an insulated refrigeration container destined for transit by ship, railcar or truck. Each container is supplied with its own independent refrigeration system and circulating fans. The system and fans are designed with sufficient capacity to maintain a pre-set box temperature of varying degrees F. for the duration of the trip. While on board ship, the containers can be connected to a ship&#39;s generator to provide power to the refrigeration systems. When the containers are in port, they may be connected to a power source provided by a local utility. 
         [0004]    When, however, the containers are in transit by railcar or truck, it must have its own generator. For railcar transport, up to 10 refrigeration containers may be loaded on a single railcar and powered by one generator mounted on the same railcar. For truck transport, each container must have its own generator which is clipped directly to the container or fastened to a container chassis. The generators are usually the gas or diesel fuel-type and consume an average of 1 gallon per hour. The generator&#39;s fuel tank typically holds 130 gallons of fuel. 
         [0005]    The refrigeration compressor automatically cycles on as the in-box temperature sensor signals the need for a reduction in temperature and off when the pre-set temperature is reached. The in-box sensor only controls the operation of the compressor. The generator is not turned off. It continues to run throughout the trip to power the circulating fans regardless of whether the compressor is on or off and regardless of the in-box temperature or the ambient temperature (the temperature outside the box). 
         [0006]    On most cross-country rail or roadway trips, continuous operation of the generator consumes the entire 130 gallons of fuel well before the container&#39;s destination. This requires a refueling process, the man-power and fueling facilities at various points along the way. Since containers begin and end their routes from various locations, it is virtually impossible to predict where and when refueling is required. Quite often, along the route, a generator dies for lack of fuel and does not get refueled and restarted and the frozen contents of the container are at the risk of perishing. 
         [0007]    It is well known that the circulating fans in the container have minimal effect in efficiently moving chilled air to every part of a container fully loaded with frozen goods. It is also well known that circulating fans generate a significant amount of BTUs/min., thereby counterproductively contributing to the raising of the in-box temperature. In addition, should the compressor experience failure during transit, the fans, since they are not controlled by the in-box temperature sensor, would continue to run and ultimately raise the in-box temperature to a point where the frozen goods would perish. 
         [0008]    It is, therefore, questionable that the continuous operation of the circulating fans is justified considering: (1) the amount of fuel and expense required to operate the generator when it is operating solely to power the fans; (2) the effectiveness of the fans; (3) the fact that the fans themselves, when operating, contribute to raising the in-box temperature, thereby decreasing the overall efficiency of the refrigeration system, and; (4) the risk of loosing a load of perishable goods if the compressor were to fail in transit. 
         [0009]    This is especially questionable, when the container is transported through an area of the country where the ambient temperature is the same as or below the required in-box temperature. In these conditions, there is no need for the circulating fans to be operating and therefore, no need for the generator to be running. While the generator is operated during this period: (1) generator running time and its associated maintenance costs, man power and fuel consumption are a total waste, and; (2) the environment is unnecessarily contaminated. 
         [0010]    A number of devices and methods have been proposed for controlling generators. None of these, however, have addressed the serious problem of generators that are operating unnecessarily. 
         [0011]    U.S. Pat. No. 5,977,646 to Lenz et al. discloses a method for automatically restarting a generator set following a nuisance shutdown. 
         [0012]    U.S. Pat. No. 5,561,330 to Crook discloses an automatic electric power generator control that automatically starts the generator engine and the generator when a demand is made for electric power. 
         [0013]    U.S. Pat. No. 4,286,683 to Zeigner et al. and U.S. Pat. No. 5,072,703 to Sutton disclose systems for automatically stopping and restarting the internal combustion engine of a vehicle. 
         [0014]    The foregoing illustrates limitations known to exist in present devices and methods. Thus, it would be advantageous to provide an alternative device and method of limiting the running time of a generator during its transit so as to reduce fuel consumption, reduce overall operational and maintenance costs, and reduce environmental contamination while safely ensuring the goods in transit are kept frozen at the required in-box temperature. 
       SUMMARY OF THE INVENTION  
       [0015]    It is, therefore, an object of the present invention to provide a generator start/stop controller that uses an ambient temperature sensor rather than an in-box sensor in addition to a programmed microprocessor to regulate the operation of the generator. When the container is transported through an area where the ambient temperature is the same as or less than the required in-box temperature, the generator is automatically turned off completely. This contributes enormously to cost, energy and equipment savings and provides a cleaner environment. 
         [0016]    In addition, it is an object of the present invention to provide a generator start/stop controller that uses pre-calculated settings and programming to automatically turn the generator back on, not simply when the ambient temperature is the same as or greater than the required in-box temperature, but only when the container has experienced a period of time in a high heat zone sufficient to compromise the required in-box temperature and the quality of the frozen goods in transport. This further contributes to cost, energy and equipment savings and also a cleaner environment. 
         [0017]    The invention proposes to avoid having to provide an in-box temperature sensor and an electrical conductor for the temperature sensor connected between the container and the generator as is the case with in-box temperature sensing systems. This is especially advantageous on a railway system where several refrigerated containers are operated via individual power cords from a single generator/compressor unit. These power cords must provide a separate conductor dedicated to the temperature sensor. Since ambient temperature is used in the present invention to control the run-time of the generator, the temperature sensor may be installed with the controller directly on the generator unit and the separate temperature sensor conductor is not required. In addition to cost savings in the reduced quantity of sensors and conductors required per generator unit, there are installation, maintenance, and operational advantages, as well. 
         [0018]    The invention also proposes to be capable of controlling the start/stop of generators manufactured by any major manufacturer of such components and be retrofitably installed on such components. 
     
     
       BRIEF DESCRIPTION OF THE DRAWING  
         [0019]    The invention will become more apparent by reading the following detailed description in conjunction with the drawing, which is shown by way of example only, wherein: 
           [0020]      FIG. 1  is a block diagram of a generator start/stop controller which may be operated according to the methods of the invention. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0021]    Referring now to  FIG. 1 , a generator set  10  in accordance with the present invention is shown in block drawing form. Generator set  10  includes three principle components, a generator  12 , engine  14  and a controller  16 . The controller is enclosed by enclosure walls  62  represented in a dash-lined box in  FIG. 1 . 
         [0022]    Engine  14  is preferably an industrial duty diesel engine. Such an engine would include a cooling system, an oil lubricant system, an electrical system including a battery, an alternator and glow plugs. Its fuel system would include a fuel tank and a fuel solenoid for controlling the flow of fuel to the cylinders. A drive shaft  30  transfers energy from the engine to the generator. The engine  14  also includes means for shutting down and restarting the engine  14 . The shutting down/restarting means is identified generally at  63  in  FIG. 1 . The shutting down/restarting means  63  is collectively comprised of well known electronically actuated components such as a fuel valve and a starter, and also may include a fuel/engine preheating device if the engine  14  is a diesel engine. As shown in  FIG. 1 , means  63  is in signal receiving relation with controller  16 . When it is necessary to shut down the engine, the controller  16  sends a signal to each of the components comprising the shutting down/restarting means  63 , which thereby closes or otherwise shuts down the components and as a result, causes the engine  14  to shut down. Conversely, when it is necessary to restart the engine  14 , a signal is sent by the controller  16  to the shutting down/restarting means  63  components to open an/or actuate the components and thereby restart the engine  14 . 
         [0023]    Generator  12  could be, for example, a 15 KW, 18.75 KVA, 230, 460 VAC, 3-phase, 60 Hz direct drive, brushless generator. Anyone skilled in the art would recognize that other generators could be advantageously used and that the specifically recited generator is an example only. The above-described generator, as indicated, can be wired for 230 V and 460 V AC power output. Power cable  18  can be used to deliver power to a temperature control unit for a cargo container or other application. 
         [0024]    Controller  16  includes the standard controls for operating a generator set as known to those skilled in the art. The controller  16  is connected to the engine  14  and generator  12  to perform routine functions such as operator-initiated engine startups and shutdowns. The engine  14  and generator  12  are electrically connected to controller  16  by connecting cable means  32  and  34  respectively. The controller  16  is also connected to various engine component sensors. For example, the controller  16  can be connected to a water temperature sensor, engine rpm sensor, oil pressure sensor, and air flow sensor. Such sensors are represented generally as  40   a,    40   b,    40   c,  and  40   d  in  FIG. 1  and are shown in signal transmitting relation with the controller  16 . 
         [0025]    Controller  16  includes processor logic which can be executed by a microprocessor to make various engine operating decisions in response to determined engine operating parameters based upon control sensor readings. These control processors are discussed in more detail below. 
         [0026]    Controller  16  preferably includes an operator interface including a controller display  20 , which could be, for example, an LCD display. Controller  16  also includes a keyboard  22  for entering commands. Controller  16  includes a memory unit  24 , such as a Random Access Memory (RAM) which can maintain a log of certain engine operating parameters, their values and the time at which those values occurred particularly when an engine shutdown resulted. Memory unit  24  can be used to store other data as well. 
         [0027]    The arrangement of generator set components described above can advantageously be used to execute the method of the present invention by one skilled in the art. If a generator set shutdown occurs, the engine will not automatically restart if the processor determines that, based upon sensor readings, certain engine operating parameters are outside of the appropriate ranges. 
         [0028]    Engine shutdowns can be controller-initiated if a generator set operating parameter being monitored by the controller is determined by the controller to be outside of normal operating ranges. 
         [0029]    Additional controls to perform the alternative method, in accordance with the present invention, are hereby described. The start/stop controller  70  is connected between generator  12  and load  26  via power cable  18  so that high voltage current flow may be interrupted for control purposes. During normal generator running operations the load sensor  72  sends a signal to the start/stop controller  70 . The start/stop controller  70  thereby, determines when to disconnect the high voltage current between generator  12  and load  26  and then disconnect the control voltage to controller  16  thereby initiating the engine  14  shutdown. During the shut down cycle ambient temperature sensor  74  sends a signal to the start/stop controller  70 . The processor logic of start/stop controller  70  determines when to reconnect control voltage to controller  16  and, therefore, initiate the engine  14  start sequence. After a predetermined time, the processor logic of start/stop controller  70  determines when to reconnect high voltage current between generator  12  and load  26 . 
         [0030]    This invention is intended to work in conjunction with and supplemental to, existing controls and in no way to interfere with normal engine control systems. All existing safety circuits, automatic control methods and other integral system components are left undisturbed. 
         [0031]    Numerous characteristics and advantages of the invention covered by this disclosure have been set forth in the foregoing description. It will be understood, however, that this presentation is, in many respects, only illustrative. Changes may be made in details, particularly in matters of shape, size and arrangement of parts without exceeding the scope of the invention. To those skilled in the art, it will be apparent that the method described in this disclosure as the present invention is not limited to refrigeration systems used on containers transporting frozen goods via rail or roadway, but to any such refrigeration system that would benefit from the method herein described. 
       REFERENCE NUMERALS IN THE DRAWING  
       [0000]    
       
           10  generator set 
           12  generator 
           14  engine 
           16  controller 
           18  power cable 
           20  controller display 
           22  controller keyboard 
           24  controller memory unit 
           26  load 
           30  drive shaft 
           32  connection cable means 
           34  connection cable means 
           40   a  sensor 
           40   b  sensor 
           40   c  sensor 
           40   d  sensor 
           62  enclosure walls 
           63  shutting down/restarting means 
           70  start/stop controller 
           72  load sensor 
           74  ambient temperature sensor