Abstract:
A method to operate an electronically controlled air compressor powered by an internal combustion engine, wherein the air compressor is selectively activated when the air compressor minimum threshold value differs from the air compressor minimum threshold hysteresis by a predetermined value, and is deactivated when the air compressor maximum threshold value and the air compressor maximum threshold value hysteresis value differ by a predetermined value.

Description:
TECHNICAL FIELD 
       [0001]    There is a continuing need and desire to optimize energy consumption in the operation of a vehicle, especially heavy duty trucks. In applications employing an air compressor, this need is especially felt, as the air compressor is usually operated from the operation of engine, which generally results in a decrease in fuel economy. It has become desirable to operate an air compressor from a power source that can take advantage of passive operation of the air compressor, as well as active operation of the air compressor in order to improve fuel consumption efficiency while operating the air compressor. 
       BRIEF SUMMARY 
       [0002]    In one non limiting embodiment, there is disclosed a method to operate an air compressor powered by a power source, which may be an internal combustion engine. If the power source is an internal combustion engine that powers a vehicle, the engine may have an engine brake, and the vehicle may also be equipped with a Global Positioning System (GPS). The compressor is controlled by an electronic control unit (ECU) having memory, and may be a separate ECU for controlling the compressor, or it may be an ECU that controls the engine. The compressor is in fluid communication with an air storage unit, and the air storage unit may be in fluid communication with various auxiliary devices, such as brakes, dash board mounted controls, horns, etc. 
         [0003]    In one non limiting embodiment, the method may include the steps of:
       a) determining an air compressor pressure minimum threshold value;   b) determining an air compressor pressure minimum threshold hysteresis value;   c) determining whether the air compressor minimum threshold value differs from the air compressor minimum threshold hysteresis by a predetermined value;   d) activating the air compressor to deliver compressed air to a remote location;   e) deactivating the air compressor.       
 
         [0009]    In another non-limiting embodiment, deactivating the air compressor may include the steps of:
       a) determining an air compressor maximum threshold hysteresis value;   b) determining an air compressor maximum threshold value;   c) determining whether the air compressor maximum threshold value differs from the air compressor maximum threshold value hysteresis value by a predetermined value;   d) determining whether the engine has a fueling demand less than or equal to a predetermined value;   e) determining a hybrid air compressor activation value from the difference between the air compressor maximum threshold value differs from the air compressor maximum threshold value hysteresis value;   f) deactivating the air compressor when the difference between the air compressor maximum threshold value and the air compressor maximum threshold value hysteresis value exceeds a predetermined value.       
 
         [0016]    In another non limiting embodiment, when the engine is used to power a vehicle, the method may include determining travel topography to anticipate engine fueling demand. The topography may be determined by resort to a Global Positioning System (GPS) wherein the elevations of a road are determined and that information is used by the ECU to control fueling demand by the engine so that the vehicle coasts in a downhill situation, fueling demand is reduced and the movement of the vehicle powers the compressor without the expenditure of fuel. 
         [0017]    In another non limiting embodiment, the method may include initiating operation of the air compressor based upon data signals from a pressure sensor to transmit data signals indicative of air pressure in an air storage reservoir. When the data signals indicate the air pressure is below a predetermined value, the air compressor is activated, and when the data signals indicate that the pressure in the air storage reservoir meet or exceed a predetermined value, the air compressor is deactivated. The pressure sensor is connected to an ECU to operate the air compressor, and the ECU may further be used to operate the engine as well as the compressor. 
         [0018]    In another non limiting embodiment, the method may utilize a pressure switch in the air storage reservoir rather than a pressure sensor. When the pressure in the air storage reservoir is below a predetermined value, the compressor is activated, and when the pressure in the reservoir exceeds a predetermined value, the switch deactivates that air compressor. 
         [0019]    In another non limiting embodiment, the present invention may be directed to and air compressor in fluid connection to an air storage unit, comprising a controller configured to
       a) determine an air compressor pressure minimum threshold value;   b) determine an air compressor pressure minimum threshold hysteresis value;   c) determine whether the air compressor minimum threshold value differs from the air compressor minimum threshold hysteresis by a predetermined value;   d) activate the air compressor to deliver compressed air to a remote location;   e) determine an air compressor maximum threshold hysteresis value;   f) determine an air compressor maximum threshold value;   g) determine whether the air compressor maximum threshold value differs from the air compressor maximum threshold value hysteresis value by a predetermined value;   h) determine whether the engine has a fueling demand less than or equal to a predetermined value;   i) determine a hybrid air compressor activation value from the difference between the air compressor maximum threshold value differs from the air compressor maximum threshold value hysteresis value; and   j) deactivate the air compressor when the difference between the air compressor maximum threshold value and the air compressor maximum threshold value hysteresis value exceeds a predetermined value.       
 
         [0030]    These and other aspects of the invention will become apparent upon a review of the drawings and a reading of the specification and claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0031]      FIG. 1  is a schematic representation of an air compressor actuated by a power source. 
           [0032]      FIG. 2  is a schematic representation of a flowchart showing one embodiment of a method for optimizing energy consumption during the operation of an air compressor. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0033]    Turning now to the drawings wherein like numbers refer to like structures, and particularly to  FIG. 1 , depicted therein is a schematic representation of a system  10  to operate an air compressor according to one non limiting embodiment of the invention. 
         [0034]    Specifically, power source  12  is depicted as an internal combustion engine with a block  14  and cylinders  16  disposed therein for reciprocal movement to drive a crank shaft  22  in the manner well known in the art. While an internal combustion engine is shown as the power source, it is equally understood that the power source could be an electric motor, or a hybrid electric motor/internal combustion engine, or even a fuel cell power source. What is important to understand that each instance, a power source consumes energy to create the rotational motion to rotate the drive shaft to power the air compressor  26  in a manner to be hereinafter described. 
         [0035]    A controller, such as an electronic control unit (ECU)  43 , may be included in the system  10  to control various operations of the engine  12  and other system or subsystems associated therewith, such as the clutch mechanism associated with the compressor  26 . Various sensors may be in electrical communication with the controller via input/output ports  94 . The ECU may include a microprocessor unit (MPU)  45  in communication with various computer readable storage media via a data and control bus  100 . The computer readable storage media may include any of a number of known devices which function as read only memory  102 , random access memory  104 , and non-volatile random access memory  106 . 
         [0036]    In operation, the controller  92  receives signals from various engine/vehicle sensors and executes control logic embedded in hardware and/or software to control the system  10 . The computer readable storage media may, for example, include instructions stored thereon that are executable by the controller  92  to perform methods of controlling all features and sub-systems in the system  10 . The program instructions may be executed by the controller in the MPU  98  to control the various systems and subsystems of the engine and/or vehicle through the input/output ports  94 . In general, the dashed lines shown in  FIG. 1  illustrate the optional sensing and control communication between the controller and the various components in the powertrain system. Furthermore, it is appreciated that any number of sensors and features may be associated with each feature in the system for monitoring and controlling the operation thereof. 
         [0037]    In one non-limiting aspect of the present invention, the controller  92  may be the DDEC controller available from Detroit Diesel Corporation, Detroit, Mich. Various other features of this controller are described in detail in a number of U.S. patents assigned to Detroit Diesel Corporation. Further, the controller may include any of a number of programming and processing techniques or strategies to control any feature in the system  10 . Moreover, the present invention contemplates that the system may include more than one controller, such as separate controllers for controlling system or sub-systems, including an exhaust system controller to control exhaust gas temperatures, mass flow rates, and other features associated therewith. In addition, these controllers may include other controllers besides the DDEC controller described above. 
         [0038]    Turning now to  FIG. 2 , there is illustrated one schematic representation of a method  78  according to one non limiting embodiment of the present invention. 
         [0039]    Specifically, it is useful to first describe the set path logic  79  for actuating the air compressor. At step  80 , an air compressed pressure sensor switch is shown to activate the compressor to replenish air supply into the air storage reservoir. In a vehicle application, it is contemplated to use a sensor as the switch to take advantage of using the kinetic energy of the vehicle when it is coasting to power the compressor. For example, in a vehicle application, the air compressed pressure may operate air brakes, horns, pneumatic dash board controls, as well as flows through the exhaust system to assist in regeneration efforts to maintain emission standards as previously described. 
         [0040]    Step  82  is determining an air compressor minimum threshold value. This may be accomplished by a sensor or pressure switch in a reservoir as previously described. Step  84  is determining the air compressor minimum threshold hysteresis value. The air minimum threshold hysteresis value is used to eliminate sensor or switch margin of error. 
         [0041]    At step  86 , the air compressor minimum threshold value is compared to the air compressor minimum threshold hysteresis value to determine whether the air compressor minimum threshold value differs from the air compressor minimum threshold hysteresis by a predetermined value. At step  88 , if the pressure is less than the predetermined value the air compressor the compressor is to be engaged, step  90  a set, reset to activate the clutch to engage the compressor to the drive shaft, as previously described, if the air compressor minimum pressure is less than the air compressor minimum hysteresis. 
         [0042]    The reset logic path  101  will now be discussed. Based upon the pressure in the air storage reservoir, the air compressor maximum threshold pressure is determined at step  104 , and the air compressor maximum hysteresis is determined at step  102 . Step  103  is determining whether the air compressor maximum threshold value differs from the air compressor maximum threshold value hysteresis value by a predetermined value. If it is determined at step  100  that the difference between the air compressor maximum threshold value and the air compressor maximum threshold hysteresis value is less than a predetermined value, then step  98 . If it is determined at  106  that the difference between the air compressor maximum threshold pressure and the air compressor maximum threshold hysteresis exceed a predetermined value, then the reset at step  98  is activated and no signal proceeds to step  108 . 
         [0043]    At the same time that steps  102 ,  104 ,  103 ,  100 ,  106  and  98  are occurring, the ECU also determined whether the engine brake, such as a Jake Brake from Jacobs engine brake company, is activated at step  110 . In addition the ECU may determine whether a power source demand is made at step  112 , such as for example pneumatic horns signals on a vehicle, such as a truck, or there is demand for compressed air by the operator for pneumatic dash controls for a vehicle, as indicated at step  116 . At  114 , a determination is made whether the power source demand and the available air pressure is less than or equal to a predetermined value. In addition, a Global Positioning System  118  may produce signals indicative of the road conditions for a traveling vehicle. If it is determined at step  120  that the engine brake is engaged, or the GPS system indicates that road conditions are such that is desirable to engage the clutch to take advantage of declines in the road to passively power the air compressor, or if it is determined at  116  that the pneumatic dash controls are activated, then the method proceeds to step  108 , wherein the inputs from step  120  as well as the input from step  98  are both used as iput to step  92  to activate the air compressor at step  94 . 
         [0044]    It is understood that the words are intended to be words of description, and not words of limitation. Many variations and modifications are possible without departing form the scope and spirit of the invention as set forth in the appended claims.