Abstract:
An engine starter system that predicts when starter failure is imminent. The engine starter system monitors engine starter crank speed, battery voltage and ambient air temperature. The crank speed, battery voltage and ambient air temperature are communicated to a controller which compares the crank speed for the measured battery voltage and air temperature to a predicted crank speed for the measured battery voltage and air temperature. If the crank speed is lower than the predicted crank speed, a signal is sent to an alarm.

Description:
BACKGROUND 
       [0001]    The present invention relates to an engine starter predictive maintenance system. Engine starters are known to fail periodically. An engine starter failure in a transport refrigeration unit can result in downtime for a transport trailer and the loss of goods in the transport trailer. 
       SUMMARY 
       [0002]    In one embodiment, the invention provides an engine starter system for an engine. The engine starter system includes an engine starter operable to engage the engine and rotate at a crank speed. The system also includes a battery in electrical communication with the engine starter, a crank speed sensor operable to measure the crank speed of the engine starter, a voltage sensor operable to measure the voltage of the battery, and a temperature sensor operable to measure the ambient air temperature. An additional component of the system is a controller in electrical communication with the engine starter, the crank speed sensor, the voltage sensor, and the temperature sensor, wherein the controller is programmed with predicted engine crank speed values based on battery voltage and ambient air temperature. The controller compares the measured crank speed of the engine starter to the predicted crank speed value for the measured battery voltage and measured ambient air temperature. 
         [0003]    In another embodiment, the invention provides a method of operating an engine starter. The method includes engaging an engine with an engine starter, rotating the engine starter at a crank speed, measuring the crank speed of the engine starter, measuring the voltage of a battery in electrical communication with the engine starter, and measuring the ambient air temperature. The method also includes comparing the measured crank speed to a programmed predicted crank speed value for the measured battery voltage and ambient air temperature. 
         [0004]    In yet another embodiment, the invention provides a transport refrigeration system. The system includes an engine, a refrigeration system including a compressor driven by the engine, an engine starter engageable with the engine and rotatable at a crank speed, a battery in electrical communication with the engine starter, a crank speed sensor operable to measure the crank speed of the engine starter, a voltage sensor operable to measure the voltage of the battery, and a temperature sensor operable to measure the ambient air temperature. The system also includes a controller in electrical communication with the engine starter, the crank speed sensor, the voltage sensor, and the temperature sensor. The controller is programmed with predicted engine crank speed values based on battery voltage and ambient air temperature. The controller compares the measured crank speed of the engine starter to the predicted crank speed value for the measured battery voltage and measured ambient air temperature. 
         [0005]    Other aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]      FIG. 1  is a perspective view of a vehicle including a transport refrigeration system. 
           [0007]      FIG. 2  is a schematic of an engine starter system. 
           [0008]      FIG. 3  is a graph showing a hypothetical example of engine cranking speed vs. voltage vs. temperature. 
       
    
    
     DETAILED DESCRIPTION 
       [0009]    Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. 
         [0010]      FIG. 1  is a perspective view of a vehicle  10  including a transport refrigeration system  12 . The vehicle  10  includes a tractor  14  and trailer  16 . Goods are placed in the trailer  16  for transport. The transport refrigeration system  12  is coupled to the front of the trailer  16  and serves to maintain the interior of the trailer  16  at a temperature. With additional reference to  FIG. 2 , the transport refrigeration system  12  includes a diesel engine  18 , an engine starter  20 , a battery  22 , and a refrigeration system  24 , which includes a compressor (not shown), condenser (not shown), evaporator (not shown), and one or more fans (not shown). In the illustrated embodiment an engine starter system  26  is shown as part of a transport refrigeration system  12  on a trailer  16 , but can also be used on other cargo transportation systems such as rail cars, shipping containers, trucks, and the like. In addition, the engine starter system  26  can be used with any internal combustion engine not limited to transport refrigeration applications. 
         [0011]      FIG. 2  is a schematic view of the engine starter system  26 . The engine starter  20  is electrically coupled to the battery  22 . A crank speed sensor  28  is coupled to the engine starter  20  and is operable to measure the crank speed of the engine starter  20 . A voltage monitor  30  is electrically coupled to the battery  22  and is operable to measure the voltage of the battery  22 . A temperature sensor  32  is operable to measure the ambient air temperature. The temperature sensor  32  need not be coupled to the engine starter  20 . A controller  34  is in communication with the engine starter  20 , the crank speed sensor  28 , the voltage monitor  30 , and the temperature sensor  32 . The controller  34  is programmed with predicted engine  18  crank speed values based on battery voltage and ambient air temperature. 
         [0012]      FIG. 3  is a graph showing a hypothetical example of engine  18  cranking speed vs. voltage. The X-axis of the graph is battery voltage, and the Y-axis of the graph is engine  18  cranking speed in rotations per minute (rpm). A number of lines are plotted on the graph, each line corresponding to an ambient air temperature. The graph is produced by plotting data that is captured during actual testing. During testing a known good engine  18  and a known good engine starter  20  are used for testing. Engine  18  cranking speed may vary depending on the engine  18  model and engine starter  20  model being used. The graph shown in  FIG. 3  is a hypothetical graph for a Yanmar 2.1 liter, TK486V engine  18  with an OEM Hitatchi engine starter  20 , TK part number 45-2177. The test data assumes use of 15W-40 mineral oil (non-synthetic), a cold-cranking cycle with the fuel solenoid disconnected, a battery  22  rated at 750 CCA at O degrees Fahrenheit, and 1/0 gauge battery cables. 
         [0013]    The engine starter system  26  functions as follows. During a pre-trip routine, the engine starter  20  receives a signal from the controller  34  to start the engine  18 . Before the engine  18  starts cranking, the controller  34  communicates with the voltage monitor  30  and the temperature sensor  32  to receive the current battery  22  voltage and ambient air temperature. The engine starter  20  then cold-cranks the engine  18  without supplying fuel to the engine  18  until a signal is received telling the engine starter  20  to stop cranking. While the engine  18  is cranking the crank speed sensor  28  measures the crank speed of the engine starter  20 . The controller  34  then communicates with the crank speed sensor  28  to receive the crank speed. Next, the controller  34  compares the actual crank speed to a predicted crank speed for the measured battery  22  voltage and ambient air temperature. If the actual crank speed is less than the predicted crank speed, then the controller  34  sends a signal to trigger an alarm  36 . In an alternative embodiment, the crank speed sensor  28  measures the battery  22  voltage while the engine starter  20  is cranking. The controller  34  is also programmed with a predicted crank speed at a given ambient air temperature and a battery  22  voltage that is measured while the engine starter  20  is cranking. The alarm  36  can be one or more of an audible alarm, a visual alarm, and an alarm code displayed along with pre-trip diagnostic results. The alarm  36  may be displayed on one or more of the trailer  16 , the tractor  14 , a computer (not shown), and a diagnostic machine (not shown). In one embodiment the signal to trigger the alarm  36  is transmitted wirelessly. 
         [0014]    In another embodiment the controller  34  triggers an alarm  36  when the measured crank speed is less than the product of the predicted crank speed value multiplied by a sensitivity factor. The sensitivity factor is a value between 0 and 1. The sensitivity factor may be set by the engine starter system  26  manufacturer. In an alternative embodiment, the sensitivity factor is adjustable by the operator. The sensitivity factor allows the engine starter system  26  to be more or less sensitive, depending on the needs of the operator. In another embodiment the controller  34  sends a signal to indicate that the engine starter  20  is functioning properly when the measured crank speed is equal to or more than the product of the predicted crank speed value multiplied by a sensitivity factor. 
         [0015]    In an alternative embodiment, the crank speed sensor  28  is coupled to the engine  18 . The crank speed sensor  28  measures the speed of the engine  18 , communicates the engine  18  speed to the controller  34 , and the controller  34  derives the crank speed of the engine starter  20  from the speed of the engine  18 . In yet another embodiment, the crank speed sensor  28  is part of an engine control module (ECM) (not shown) and the controller  34  communicates with the ECM to get the engine starter  20  crank speed. 
         [0016]    An alternative embodiment of the engine starter system  26  includes counting the number of cranking cycles. A counter (not shown) is connected to the engine starter  20  and counts each cranking cycle that occurs. The counter then communicates the number of cranking cycles that have occurred to the controller  34 . The controller  34  is programmed with a lifetime number of cranking cycles and is programmed to trigger an alarm  36  when the number of cranking cycles counted by the counter is equal to or greater than the lifetime number of cranking cycles. The counter is able to be reset by a mechanic when the engine starter is replaced. In another embodiment, the counter and method of counting cranking cycles is used in combination with the other methods and devices described herein. 
         [0017]    In yet another embodiment, the engine starter system  26  includes a thermal switch (not shown) coupled to the engine starter housing. The thermal switch can be coupled to the engine starter housing during manufacture of the engine starter  20 , or it can be added to the exterior of the housing at a later date. The thermal switch is set to trigger the alarm  36  if the temperature of the engine starter housing is greater than a set temperature. In an alternative embodiment, the thermal switch sends a signal to the controller  34  if the temperature of the engine starter housing is greater than a set temperature. As an example, if the thermal switch is set to trigger an alarm  36  at 250 degrees Fahrenheit, then the alarm  36  will be triggered if the temperature of the engine starter housing is equal to or greater than 250 degrees Fahrenheit. If the temperature of the engine starter housing is less than 250 degrees Fahrenheit, then no alarm  36  is triggered. In another embodiment, the thermal switch and associated alarm  36  is used in combination with other methods and devices described herein. 
         [0018]    The alarm  36  is provided to alert the operator and/or maintenance personnel during the pre-trip inspection that the engine starter  20  is not functioning as predicted and should be evaluated for repair or replacement. Replacing an engine starter  20  before it fails during transit is desirable because an engine starter  20  that fails during transit can result in lost cargo due to the transport refrigeration system  12  being unable to function and maintain the cargo at a set temperature. In addition, a failed engine starter  20  can result in downtime for the tractor  14  and trailer  16  while a replacement engine starter  20  is sourced and installed. Hence it is desirable to replace an engine starter  20  before it fails to avoid these additional costs. 
         [0019]    Various features and advantages of the invention are set forth in the following claims.