Patent Publication Number: US-2017363022-A1

Title: Generator having confined space shutdown

Description:
RELATED APPLICATIONS 
     This application claims priority to U.S. Provisional Patent Application No. 62/351,903, filed on Jun. 17, 2016, the entire contents of which are hereby incorporated by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to generators and, in particular, shutting down generators in a confined space. 
     SUMMARY 
     Existing methods of determining when a generator is in a confined area approximate an oxygen level at an intake of the engine of the generator. Such methods can be unreliable, and may cause shutdown of the generator when the generator is not in a confined space or may not detect a problem until it is too late. 
     In one embodiment, a generator is provided that includes an internal combustion engine. The generator further includes an alternator having a rotor driven by the internal combustion engine and a stator in which alternator output power is induced when the rotor is driven. The generator further includes a power outlet coupled to the alternator to provide power to a device coupled to the power outlet. The generator further includes an electronic processor communicatively coupled to the engine. The electronic processor is configured to obtain an engine speed of the engine, and determine that the engine speed is below an engine speed threshold. The electronic processor is further configured to determine, in response to determining that the engine speed is below the engine speed threshold, that a predetermined number of a plurality of secondary parameters of the generator have crossed respective secondary thresholds. The electronic processor is further configured to shut down the generator in response to determining that the predetermined number of the secondary parameters have crossed the respective second thresholds. 
     In another embodiment, a method of shutting down a generator is provided. The method includes obtaining, with an electronic processor, a value of a plurality of parameters of the generator. The method further includes determining, with the electronic processor, that a predetermined number of the values of the plurality of parameters have crossed respective thresholds. The method further includes shutting down the generator with the electronic processor in response to determining that the predetermined number of the values of the plurality of parameters have crossed the respective thresholds. 
     In another embodiment, a method of shutting down a generator is provided. The method includes obtaining, with an electronic processor, an engine speed of an engine of a generator. The method further includes determining, with the electronic processor, that the engine speed is below an engine speed threshold. The method further includes determining, with the electronic processor and in response to determining that the engine speed is below the engine speed threshold, that a predetermined number of a plurality of secondary parameters of the generator have crossed respective secondary thresholds. The method further includes shutting down the generator with the electronic processor in response to determining that the predetermined number of the secondary parameters have crossed the respective second thresholds. 
     Other features and aspects of the invention will become apparent by consideration of the following detailed description and accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is perspective view of a generator according to one embodiment of the invention. 
         FIG. 1B  is a block diagram of the generator of  FIG. 1A  according to one embodiment of the invention. 
         FIG. 2  is a block diagram of a controller included in the generator of  FIGS. 1A and 1B  according to one embodiment of the invention. 
         FIG. 3  is a flowchart of an example method executed by a processor of the generator of  FIGS. 1A and 1B  to determine whether the generator is operating in a confined space according to one embodiment of the invention. 
         FIG. 4  is a flowchart of another example method executed by a processor of the generator of  FIGS. 1A and 1B  to determine whether the generator is operating in a confined space according to one embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION 
     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. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. The terms “mounted,” “connected” and “coupled” are used broadly and encompass both direct and indirect mounting, connecting and coupling. Further, “connected” and “coupled” are not restricted to physical or mechanical connections or couplings, and can include electrical connections or couplings, whether direct or indirect. 
     It should be noted that a plurality of hardware and software based devices, as well as a plurality of different structural components may be utilized to implement the invention. Furthermore, and as described in subsequent paragraphs, the specific configurations illustrated in the drawings are intended to exemplify embodiments of the invention and that other alternative configurations are possible. The terms “processor” “central processing unit” and “CPU” are interchangeable unless otherwise stated. Where the terms “processor” or “central processing unit” or “CPU” are used as identifying a unit performing specific functions, it should be understood that, unless otherwise stated, those functions can be carried out by a single processor, or multiple processors arranged in any form, including parallel processors, serial processors, tandem processors or cloud processing/cloud computing configurations. 
       FIG. 1A  is a perspective view of a generator  100  according to one embodiment and  FIG. 1B  is a block diagram of the generator  100  according to one embodiment. As shown in  FIG. 1A , the generator  100  includes a frame  105  having a folding handle  110 . The generator  100  further includes a fuel tank  120  with a fuel cap  122 , a main panel  130 , an internal combustion engine  140 , and an alternator  145 . Although not shown, in some instances, two or more wheels are secured to the bottom of the frame  105  to ease in the transport of the generator  100 . The generator  100  further includes a pull starter cord  155  to optionally start the engine  140 . In some embodiments, the generator  100  includes a fuel valve to open/close a fuel supply line connecting the fuel tank  120  to the engine  140 . 
     The main panel  130  is positioned adjacent to the fuel tank  120  and above the engine  140 . In the illustrated embodiment, the main panel  130  includes power outlets, for example four alternating current (AC) outlets  160 , each having terminals for connecting to a three prong plug of an AC load. The AC outlets  160  are ground fault circuit interrupter (GFCI) outlets, although other outlet types may be included. The main panel  130  further includes a 120/240 Volt AC outlet  165 . The AC outlets  160  and  165  are protected from water and contaminant (e.g., dust) infiltration via covers, which may be made of rubber or another suitable material. In some embodiments, DC outlets  180  are also provided on the main panel  130  or elsewhere on the generator  100 . 
     As shown in  FIG. 1B , the engine  140  is coupled to the alternator  145  (for example, an output shaft of the engine  140  rotates a rotor of the alternator  145 ). The rotating rotor of the alternator  145  induces an AC output from a stator of the alternator  145 . The alternator  145  is coupled to an AC/DC converter  175  and provides the AC output to the AC/DC converter  175 . The AC/DC converter  175  converts the AC output to a DC output and may additionally condition the received AC output to provide a regulated, consistent output. In some embodiments, the AC/DC converter  175  provides the DC output to one or more DC outlets  180  that can provide DC power to a device coupled to the DC outlet  180 . In some embodiments, the AC/DC converter  175  provides the DC output to an AC/DC inverter  185 . The AC/DC inverter  185  converts the DC output to a conditioned AC output. The AC/DC inverter  185  provides the conditioned AC output to one or more of the AC outlets  160  such that the AC outlets  160  provide, for example, approximately 120V/60 Hz or 240V/50 Hz to devices coupled to the AC outlets  160 . 
     The block diagram of  FIG. 1D  also illustrates a controller  190  communicatively coupled to the engine  140 . In some embodiments, the controller  190  monitors a speed of the engine  140  and controls the speed of the engine  140 . For example, the controller  190  may adjust a throttle of the engine  140  to control a speed of the engine  140 . In some embodiments, the controller  190  controls the throttle by sending control signals to a stepper motor or other device that receives the control signals and provides mechanical control of the throttle. Although electronic control of the engine speed is described above, in some embodiments, the engine speed is controlled through a mechanical control system. In addition to or as a part of the throttle control, the controller  190  is configured to disable or shut down the engine  140  via the communicative coupling to the engine  140 . The block diagram of  FIG. 1D  is merely an example. In some embodiments, the generator  100  may include additional or fewer components in configurations different from that illustrated in  FIG. 1D . In some embodiments, the controller  190  may also be communicatively coupled to other components of the generator  100  including, for example, the AC/DC inverter  185 . For example, the controller  190  may provide switch control signals to control a switching bridge used to invert the DC signal. 
       FIG. 2  is a block diagram of the controller  190  according to one embodiment. The block diagram of  FIG. 2  is merely an example. In some embodiments, the controller  190  may include additional or fewer components in configurations different from that illustrated in  FIG. 2 . The controller  190  includes an electronic fuel injection (EFI) system, which monitors various parameters of the generator  100 . In the illustrated embodiment, the generator  100  utilizes sensors of the EFI system to detect whether the generator  100  is operating in a confined space. If the generator  100  is operating in a confined space, the generator  100  will shut itself down (i.e., the controller  190  will shut down the engine  140  by, for example, cutting off air or fuel to the engine  140 ). A generator that evaluates oxygen levels or engine speed alone to determine whether a low oxygen level exists (e.g., the generator is in a confined space) may not detect a problem in a timely manner. In the illustrated embodiment, the controller  190  monitors a variety of parameters as well as rates of change and trends of change in certain parameters. For example, when an oxygen negative correction value (as explained in greater detail below) quickly and consistently moves in a negative direction, the controller  190  determines a low oxygen condition exists and can shut down the engine  140 . As another example, when ambient temperature increases at a rapid rate, the controller  190  may determine a low oxygen condition exists. Technologies described herein provide a more accurate and timely detection of the generator  100  operating in a confined space. 
     As shown in  FIG. 2 , the controller  190  includes an electronic processor  205  and a memory  210 . The memory  210  includes read only memory (ROM), random access memory (RAM), other non-transitory computer-readable media, or a combination thereof. The electronic processor  205  is configured to receive instructions and data from the memory  210  and execute, among other things, the instructions. In particular, the electronic processor  205  executes instructions stored in the memory  210  to perform the methods described herein. The electronic processor  205  controls and is coupled to the engine  140  as indicated by  FIG. 1D  and as explained previously. 
     In the illustrated embodiment, the controller  190  includes a variety of sensors, such as an engine speed sensor  220 , an oxygen sensor  225 , an engine load sensor  230 , an ambient temperature sensor  235 , and an engine head temperature sensor  240 . The sensors  220 ,  225 ,  230 ,  235 , and  240  monitor parameters of the generator  100  and of the environment surrounding the generator  100  during operation of the generator  100 . For example, the engine speed sensor  220  monitors rotational speed of the engine  140 . The oxygen sensor  225  monitors the oxygen in an exhaust stream of the engine  140 . The engine load sensor  230  monitors a manifold pressure of the engine  140 . The ambient temperature sensor  235  measures an ambient temperature of the manifold of the engine  140 . In alternate embodiments, the ambient temperature sensor  235  monitors an ambient temperature of the environment surrounding the generator  100 . The engine head temperature sensor  240  measures the temperature at the engine head. As shown in  FIG. 2 , the sensors  220 ,  225 ,  230 ,  235 , and  240  are coupled to the electronic processor  205 . 
     The electronic processor  205  receives signals from at least one of the sensors  220 ,  225 ,  230 ,  235 , and  240  and monitors the operation of the generator  100  based on the received signals. For example, the electronic processor  205  may determine operating parameters of the generator  100  based on at least one of the received signals. The electronic processor  205  may also compare these parameters to respective thresholds for each parameter to determine when each parameter increases or decreases beyond its respective threshold. For example, Table 1 illustrates six example parameters that may be monitored by the electronic processor  205  using the sensors  220 ,  225 ,  230 ,  235 , and  240 . 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                 Parameter 
                 Unit 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                 First 
                 (1) Engine speed 
                 Rotations per 
               
               
                 Category 
                   
                 minute (RPM) 
               
               
                   
                 (2) Amount of time that engine speed has 
                 Seconds 
               
               
                   
                 been below the engine speed threshold 
               
               
                 Second 
                 (3) Oxygen negative correction value 
                 Percent 
               
               
                 Category 
                 (4) Oxygen negative correction rate of 
                 Percent per 
               
               
                   
                 change 
                 second 
               
               
                   
                 (5) Manifold pressure (i.e., engine load) 
                 Kilopascals 
               
               
                   
                 (6) Temperature 
                 Degrees Celsius 
               
               
                   
               
            
           
         
       
     
     The electronic processor  205  monitors engine speed (i.e., parameter 1) by evaluating a signal received from the engine speed sensor  220 . The electronic processor  205  determines whether the engine speed is below an engine speed threshold (e.g., 2440 RPM). The electronic processor  205  also determines the amount of time that the engine speed has been below the engine speed threshold (i.e., parameter 2). Furthermore, the electronic processor  205  determines whether this amount of time exceeds a predetermined period of time (e.g., sixty seconds). In further embodiments, the electronic processor  205  evaluates how many times the engine speed falls below the engine speed threshold (i.e., crosses over the threshold) within the predetermined period of time. 
     With respect to oxygen negative correction value (i.e., parameter 3), in some embodiments, the electronic processor  205  controls the engine  140  to run at a preset air fuel ratio. The oxygen sensor  225  monitors the excess oxygen in the exhaust stream of the engine  140  and provides a signal to the electronic processor  205  indicative of the oxygen level. The electronic processor  205  then makes adjustments to attempt to achieve the preset air fuel ratio. For example, the electronic processor  205  may adjust a fuel injector pulse width or may adjust a fuel pressure of the engine  140 . These adjustments are referred to as the oxygen negative correction value (i.e., parameter 3) and correspond to the oxygen level in the engine  140 . In some embodiments, the electronic processor  205  determines whether the oxygen negative correction value has reached its maximum negative value (e.g., −15%, −25%, −32%, −45.7%, etc.). These maximum negative values are merely examples and may be different depending on the engine  140  included in the generator  100  (e.g., higher than −15% or lower than −45.7% for some engines). 
     In some embodiments, the electronic processor  205  monitors an oxygen negative correction rate of change (i.e. parameter 4). The oxygen negative correction rate of change is the rate of change of the oxygen negative correction value (i.e., parameter 3) over a predetermined period of time. In some embodiments, the predetermined period of time is the same as the predetermined period of time described above with respect to parameter 2. In other embodiments, the predetermined period of time is different than the predetermined period of time described above with respect to parameter 2. The electronic processor  205  determines whether the oxygen negative correction rate of change (i.e., parameter 4) decreases below its respective threshold (e.g., −0.12336% per second). 
     In some embodiments, the electronic processor  205  also monitors a manifold pressure of the engine  140  (i.e., parameter 5), which may also be referred to as engine load, by evaluating a signal received from the engine load sensor  230 . The electronic processor  205  determines whether the manifold pressure of the engine  140  exceeds an engine load threshold (e.g., 780 kilopascals). 
     In some embodiments, the electronic processor  205  also monitors an ambient temperature of the manifold of the engine  140  (i.e., parameter 6) by evaluating a signal received from the ambient temperature sensor  235 . The electronic processor  205  determines whether the temperature exceeds a temperature threshold (e.g., fifty degrees Celsius). In some embodiments, the electronic processor  205  additionally or alternatively monitors a temperature at the engine head by evaluating a signal received from the engine head temperature sensor  240 . In such embodiments, the electronic processor  205  determines whether the engine head temperature exceeds an engine head temperature threshold. 
     In some embodiments, the electronic processor  205  stores received signals from the sensors  220 ,  225 ,  230 ,  235 , and  240  in the memory  210  for comparison to later-received signals. In such embodiments, the electronic processor  205  compares stored received signals to later-received signals to determine a rate of change of a parameter, for example as previously explained with respect to the oxygen negative correction rate of change (i.e., parameter 4). In some embodiments, the electronic processor  205  also determines the rate of change of the engine speed or the temperature over a time period and determines whether such rates of change exceed a predetermined rate of change threshold for each parameter. Furthermore, the parameters shown in Table 1 are merely examples and additional or fewer parameters may be monitored by the electronic processor  205  and compared to respective predetermined thresholds. Additionally, the values provided for the predetermined thresholds above are merely examples and may be higher or lower depending on the type of engine used in the generator  100 . For example, the values of such predetermined thresholds can be adjusted during manufacturing to be compatible with different types of engines. In other words, through testing, the predetermined thresholds for each parameter of a certain engine may be determined such that shut down of the generator in a confined space occurs as desired. 
     As described in more detail with respect to  FIG. 3  below, the electronic processor  205  determines that the generator  100  is operating in a confined space when the electronic processor  205  determines that one or more parameters have crossed their respective thresholds. 
       FIG. 3  is a flowchart of an example method  300  executed by the electronic processor  205  to determine whether the generator  100  is operating in a confined space. In executing the method  300  to determine whether the generator  100  is operating in a confined space, the electronic processor  205  evaluates multiple parameters against a respective threshold for each parameter as described above. As shown in Table 1, in some embodiments, a first set of parameters is categorized into a first category and may be referred to as primary parameters. A second set of parameters is categorized into a second category and may be referred to as secondary parameters. In some embodiments, the electronic processor  205  determines that the generator  100  is operating in a confined space and stops operation of the generator  100  when a predetermined number of predetermined thresholds of the respective parameters in each category are met. Additionally, in some embodiments, a predetermined number of predetermined thresholds of the parameters in the first category must be met to trigger an evaluation of the parameters in the second category. In some embodiments, additional sets of parameters are included in additional categories (e.g., a third category or a fourth category). In such embodiments, the parameters may be grouped into other categories (e.g., the temperature may be included in the third category instead of the second category). In some embodiments, a predetermined number of predetermined thresholds of the parameters in the prior categories (e.g., the respective first and second categories) must be met to trigger an evaluation of the parameters in a latter category (e.g., the third category). As explained in greater detail below, in some embodiments, the parameters may be grouped into a single category. 
     As illustrated in  FIG. 3 , at block  302 , the electronic processor  205  obtains the engine speed of the engine  140  (for example, by receiving a signal from the engine speed sensor  220 ). At block  305 , the electronic processor  205  evaluates the primary parameters (e.g., parameters 1 and 2 of Table 1) and compares the primary parameters to the respective thresholds. In other words, at block  305 , the electronic processor  205  determines whether the engine speed is below the engine speed threshold. For example, the electronic processor  205  may determine whether the engine speed is below the engine speed threshold for a predetermined period of time. As another example, the electronic processor  205  may determine whether the engine speed has decreased below the engine speed threshold a predetermined number of times (e.g., ten times) within the predetermined period of time. In this example, the electronic processor  205  is able to determine that the engine speed is fluctuating near the engine speed threshold when the engine speed may not remain below the engine speed threshold for the predetermined period of time. With respect to this example, the value of ten times for the engine speed to decrease below the engine speed threshold is merely an example and may be higher or lower depending the type of engine used in the generator  100  and the desired operation of the generator  100 . For example, the values of such a threshold can be adjusted during manufacturing to be compatible with different types of engines. In some embodiments, the engine speed threshold is an engine speed delta from a given point. In other words, in some embodiments, the engine speed threshold may be a dynamic value based on historical speeds of the engine  140  instead of a static speed value. For example, the engine speed threshold may be one hundred RPM less than an average speed of the engine  140  over the previous five minutes. When the engine speed is not below the engine speed threshold, the method  300  proceeds back to block  302  to obtain the engine speed and the electronic processor  205  continues to evaluate the parameters of the first category. On the other hand, when the engine speed is below the engine speed threshold, at block  305 , the electronic processor  205  determines that the engine speed is below the engine speed threshold and the method  300  proceeds to block  310 . 
     In response to determining that the engine speed is below the engine speed threshold (at block  305 ), at block  310 , the electronic processor  205  evaluates the secondary parameters (e.g., parameters 3-6 of Table 1) and compares the secondary parameters to the respective thresholds as explained previously herein. As shown in  FIG. 3 , at block  310 , the electronic processor  205  determines whether a predetermined number of secondary parameters have crossed the respective secondary thresholds. For example, in some embodiments, three or more of the four secondary parameters must cross the respective secondary thresholds for the electronic processor  205  to determine that the generator  100  is in a confined space. In this example, when the electronic processor  205  determines that three or more of the four secondary parameters have crossed the respective secondary thresholds (at block  310 ), at block  315 , the electronic processor  205  shuts down the generator  100 . On the other hand, when the electronic processor  205  determines that the predetermined number of secondary parameters have not crossed the respective secondary thresholds, the method  300  proceeds back to block  302  and then to block  305 . The above explanation is merely an example. At block  305 , if the engine speed has not increased above the engine speed threshold, the method  300  will proceed back to block  310  to continue to evaluate the secondary parameters. Thus, in some embodiments, the electronic processor  205  will continue to evaluate the secondary parameters until the engine speed increases above the engine speed threshold or until the electronic processor  205  determines that the generator  100  is in a confined space. 
     As explained above, when executing the method  300 , the electronic processor  205  does not shut down the generator  100  based on the secondary parameters (see Table 1) until the primary parameters have crossed the respective thresholds (i.e., until the engine speed decreases below the engine speed threshold). However, in some embodiments, the electronic processor  205  may nonetheless monitor the secondary parameters whenever the generator  100  is operating (e.g., to store received signals from the sensors  220 ,  225 ,  230 ,  235 , and  240  to be used in rate of change determinations as described above). 
     Additionally, with respect to the above description of block  310 , the number of parameters that must exceed the respective thresholds to indicate that the generator  100  is in a confined space is merely an example. In some embodiments, a different number of parameters may be used. For example, the electronic processor  205  may determine that the generator  100  is in a confined space and shut down the generator  100  in response to at least one of the secondary parameters crossing its respective threshold. In some embodiments, the electronic processor  205  may determine that the generator  100  is in a confined space and shut down the generator  100  in response to all of the secondary parameters crossing their respective thresholds. As another example, the electronic processor  205  may determine that the generator  100  is in a confined space and shut down the generator  100  in response to a predetermined percentage of the secondary parameters crossing their respective thresholds (for example, 25%, 33%, 50%, 66%, 75%, and the like). Similar alternatives are possible for the primary parameters as well. For example, at block  305 , the method  300  may proceed to block  310  to evaluate the secondary parameters in response to at least one of the primary parameters being determined to cross the respective thresholds. Furthermore, in some embodiments, one or more of the primary parameters in Table 1 may be secondary parameters, and vice versa. 
       FIG. 4  is a flowchart of another example method  400  executed by the electronic processor  205  to determine whether the generator  100  is operating in a confined space. As mentioned above, in some embodiments, the parameters may be grouped into a single category. In such embodiments, at block  405 , the electronic processor  205  obtains a value of a plurality of parameters of the generator  100  (e.g., from the sensors  220 ,  225 ,  230 ,  235 , and  240  as explained previously). At block  410 , the electronic processor  205  determines that a predetermined number of the values of the plurality of parameters have crossed respective thresholds (e.g., as explained previously with respect to other embodiments). For example, the predetermined number may correspond to 50%, 75%, 80%, etc. of the parameters being monitored. In response to determining that the predetermined number of the values of the plurality of parameters have crossed the respective thresholds, at block  415 , the electronic processor  205  shuts down the generator  100 . In some embodiments, the plurality of parameters includes an engine speed that is compared to an engine speed threshold. In some of these embodiments, one of the parameters that is determined to cross its respective threshold may be the engine speed (i.e., the engine speed is determined to have decreased below the engine speed threshold). In another of these embodiments, the electronic processor  205  may shut down the generator  100  when the engine speed has not decreased below an engine speed threshold. In other words, in some embodiments, the electronic processor  205  may determine that a predetermined number of the values of the plurality of parameters have crossed respective thresholds and shut down the generator  100  when engine speed has not decreased below an engine speed threshold. For example, the predetermined number may be three parameters, and the electronic processor  205  may shut down the generator  100  in response to determining that oxygen negative correction value, manifold pressure, and temperature (i.e., parameters 3, 5, and 6) have crossed their respective thresholds. 
     Thus, the methods  300  and  400  allow the electronic processor  205  to evaluate monitored parameters of the generator  100  to predict when the generator  100  is in a confined space. 
     In alternate embodiments, the generator  100  is an idle down or variable speed generator. In such embodiments, the thresholds relating to rates of change of parameters (e.g., the threshold of parameter 4 described above) may be dependent on the engine speed of the generator  100 . For example, in some embodiments, the memory  210  includes a look-up table for the electronic processor  205  to reference to determine a threshold for the rate of change of one or more parameters based on the engine speed of the generator  100 . For example, with reference to the method  300 , after block  305 , the electronic processor  205  may use the determined engine speed to retrieve associated thresholds for one or more of the secondary parameters, which are then used as the thresholds in the determination of block  310 . 
     Although the invention has been described in detail with reference to certain preferred embodiments, variations and modifications exist within the scope and spirit of one or more independent aspects of the invention as described.