Abstract:
An engine controller causes a propulsion engine of a motor vehicle to be fueled in a fueling mode of operation and not to be fueled in a non-fueling mode of operation. A controlled device, such as a clutch or regulator, controls operation of a pneumatic compressor which forces compressed air into a storage tank. The controlled device is controlled according to a strategy which distinguishes between the fueling mode and the non-fueling mode for improving overall vehicle fuel economy.

Description:
TECHNICAL FIELD 
       [0001]    This disclosure relates to a motor vehicle which has a self-contained pneumatic system including, a pneumatic compressor operated by a combustion engine which propels the vehicle for compressing a gas such as air, at least one tank into which the compressor compresses gas for storage, and at least one pneumatic load, such as air-operated foundation, or service, brakes, which is operated by compressed gas supplied from the at least one tank. 
       BACKGROUND 
       [0002]    Certain motor vehicles, such as large highway tractors which can tow trailers, have pneumatic-operated foundation brakes. While a particular configuration for, and particular components used in, a pneumatic foundation brake system depend on specifications for a particular vehicle, the pneumatic system in the vehicle would comprise a pneumatic compressor operated by a combustion engine which propels the vehicle and at least one tank into which the compressor compresses gas. Pressure of gas stored in a tank is typically regulated by a control system which operates the compressor to maintain a target pressure range in the tank. Operation of the compressor is controlled by controlling a device such as a clutch or a regulator, depending on the particular type of compressor. 
         [0003]    In a system controlled by a clutch, an input shaft of a compressor is coupled through the clutch to an output shaft of the combustion engine. When the clutch is disengaged, the compressor input shaft is disconnected from the engine output shaft, and the compressor does not operate. When the clutch is engaged, the combustion engine output shaft drives the compressor input shaft through the clutch, operating the compressor, which then becomes a load on the engine. 
         [0004]    In a system controlled by a regulator, a compressor input shaft is coupled to an engine output shaft. When pressure in a gas storage tank becomes less than some minimum pressure limit, the regulator causes the compressor to operate and compress gas into the tank. When pressure in the tank becomes greater than some maximum pressure limit, the regulator causes the compressor not to operate, although the compressor input shaft may continue to be rotated by the engine output shaft. 
       SUMMARY OF THE DISCLOSURE 
       [0005]    The present disclosure relates to a pneumatic compressor control strategy which distinguishes between propulsion engine operation in a fueling mode and in a non-fueling mode. for improving overall vehicle fuel economy An engine controller causes a propulsion engine of a motor vehicle to be fueled in a fueling mode of operation and not to be fueled in a non-fueling mode of operation. 
         [0006]    A general aspect of the disclosure relates to a motor vehicle comprising a propulsion engine operated by combustion of fuel to propel the vehicle. An engine controller is operable in a fueling mode of operation to cause the engine to be fueled and in a non-fueling mode of operation to cause the engine not to be fueled. 
         [0007]    A pneumatic system includes a pneumatic compressor operable by the propulsion engine for compressing a gas, at least one tank into which the compressor compresses gas for storage, and at least one pneumatic load which is operated by compressed gas supplied from the at least one tank. 
         [0008]    A controlled device causes the propulsion engine to selectively operate the pneumatic compressor. 
         [0009]    A pressure data source provides data indicative of pneumatic pressure in the at least one tank. 
         [0010]    A device controller is operable, in the fueling mode of operation, for controlling the controlled device to cause the propulsion engine to start operating the pneumatic compressor when data provided by the pressure data source discloses that pneumatic pressure in the at least one tank has become less than a first pressure, to cause the propulsion engine to continue operating the pneumatic compressor so long as data provided by the pressure data source discloses that pneumatic pressure in the at least one tank is less than or equal to a second pressure which is greater than the first pressure, and for controlling the controlled device to cause the propulsion engine to discontinue operating the pneumatic compressor when data provided by the pressure data source discloses that pneumatic pressure in the at least one tank has become greater than the second pressure. 
         [0011]    The device controller is operable, when the engine controller switches from fueling mode of operation to non-fueling mode of operation while data provided by the pressure data source discloses that pneumatic pressure in the at least one tank is less than a third pressure which is both greater than the first pressure and equal to or less than the second pressure, for controlling the controlled device to cause the propulsion engine to start operating the pneumatic compressor and to continue operating the pneumatic compressor so long as data provided by the pressure data source discloses that pneumatic pressure in the at least one tank continues to be less than or equal to the second pressure, and to cause the propulsion engine to stop operating the pneumatic compressor when data provided by the pressure data source discloses that pneumatic pressure in the at least one tank has become greater than the second pressure. 
         [0012]    The device controller is operable, when the engine controller switches from fueling mode of operation to non-fueling mode of operation while data provided by the pressure data source discloses that pneumatic pressure in the at least one tank is both equal to or greater than the third pressure and equal to or less than the second pressure, for controlling the controlled device to cause the propulsion engine to continue not operating the pneumatic compressor, and during continuance of the non-fueling mode of operation to cause the propulsion engine to start operating the pneumatic compressor when data provided by the pressure data source discloses that pneumatic pressure in the at least one tank has become less than the third pressure and to cause the propulsion engine to stop operating the pneumatic compressor when data provided by the pressure data source discloses that pneumatic pressure in the at least one tank has become greater than the second pressure. 
         [0013]    Still another general aspect relates to a strategy for controlling the controlled device. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]      FIG. 1  illustrates a first embodiment of pneumatic system in a motor vehicle which is propelled by a combustion engine. 
           [0015]      FIG. 2  illustrates a second embodiment of pneumatic system in a motor vehicle which is propelled by a combustion engine. 
           [0016]      FIG. 3  is a diagram depicting certain modes of operation of a pneumatic system. 
           [0017]      FIG. 4  is a diagram graphically illustrating operation in both a fueling mode of operation and a non-fueling mode of operation. 
       
    
    
     DETAILED DESCRIPTION 
       [0018]      FIG. 1  shows a motor vehicle  10 , a highway tractor for example, which is propelled by an internal combustion propulsion engine  12 , such as a turbocharged diesel engine for example. Engine  12  is fueled by a fueling system  14  which in the case of a diesel engine comprises fuel injectors for injecting fuel into engine cylinders where the fuel is combusted to operate the engine. Fueling system  14  is controlled by a fueling strategy embodied in an engine controller, or engine control module (ECM)  16 , to place engine  12  in either a fueling mode of operation or a non-fueling mode of operation. 
         [0019]    As engine  12  operates, the energy of combustion results in the delivery of torque to a crankshaft  18  which is accessible on the engine&#39;s exterior for mounting a pulley  20  for rotation with crankshaft  18 . Torque can be transmitted from crankshaft  18  to various devices mounted on engine  12  via a drive belt  22  which is trained around pulley  20 . 
         [0020]    Motor vehicle  10  also comprises a pneumatic system  24  which includes a pneumatic compressor  26  operable to compress a gas, typically air, and at least one tank  28  into which compressor  26  compresses gas for storage. 
         [0021]    At least one pneumatic load is operated by compressed gas supplied from tank  28 , and  FIG. 1  shows four pneumatic- operated foundation brakes  30  which can be operated by compressed gas from tank  28 . 
         [0022]    When the compressor  26  operates, it forces compressed gas into tank  28  through a conduit  32 . Compressed gas is communicated from tank  28  through a conduit  34  to an inlet of a service brake control valve  36  which has two outlets  38 ,  40 . One outlet  38  is communicated to brakes  30  for right and left front wheels  42 ,  44  of motor vehicle  10  while the other outlet  40  is communicated to brakes  30  for right and left rear wheels  46 ,  48  of motor vehicle  10 . 
         [0023]    When a driver of motor vehicle  10  depresses a brake pedal of service brake control valve  36 , compressed air is conveyed from tank  28  through brake control valve  36  to brakes  30 , causing the brakes to be applied at the four wheels. 
         [0024]    A clutch  50  is an example of a controlled device for selectively enabling and unenabling compressor  26  to be operated by engine  12 . Clutch  50  comprises an input shaft  52  on which a pulley  54  is mounted so that both input shaft and pulley rotate together. Drive belt  22  is trained around pulley  54  to enable rotation of crankshaft  18  and pulley  20  to rotate input shaft  52  and pulley  54 . Clutch  50  comprises an output to which an input shaft  56  of compressor  26  is coupled. 
         [0025]    When clutch  50  is disengaged, it does not transmit rotation of its own input shaft  52  to input shaft  56  of compressor  26 . When clutch  50  is engaged, it does transmit rotation of its own input shaft  52  to input shaft  56  of compressor  26 . 
         [0026]    Pressure of compressed air inside tank  28  is measured by a sensor  58  to provide pressure data indicative of pneumatic pressure inside tank  28  to ECM  16 . 
         [0027]    An accelerator position sensor  60  is associated with an accelerator pedal  62  of vehicle  10  to provide data indicative of the position of accelerator pedal  62  to ECM  16 . 
         [0028]    A control strategy for clutch  50 , graphically portrayed by  FIG. 3 , is embodied in ECM  16 , although it could be embodied in a separate control module. Whenever data provided by sensor  58  discloses that pneumatic pressure inside tank  28  is greater than a pressure P2, clutch  50  is disengaged, causing propulsion engine  12  not to operate compressor  26 . This is “Compressor Off” state. Whenever data provided by sensor  58  discloses that pneumatic pressure inside tank  28  is less than a pressure P1, clutch  50  is engaged, causing propulsion engine  12  to operate compressor  26 . This is “Compressor On” state. Whenever data provided by sensor  58  discloses that pneumatic pressure inside tank  28  is both equal to or greater than pressure P1 and equal to or less than pressure P2, how clutch  50  is controlled depends on whether propulsion engine  12  is operating in the fueling mode or in the non-fueling mode as shown by  FIG. 4 . 
         [0029]    In the fueling mode of operation, clutch  50  is engaged to cause propulsion engine  12  to start operating compressor  26  when data provided by sensor  58  discloses that pneumatic pressure inside tank  28  has become less than pressure P1. Engine  12  continues operating compressor  26  so long as data provided by sensor  58  discloses that pneumatic pressure inside tank  28  is less than or equal to pressure P2. Clutch  50  is disengaged to cause engine  12  to discontinue operating compressor  26  when data provided by sensor  58  discloses that pneumatic pressure in tank  28  has become greater than pressure P2. 
         [0030]    When ECM  16  switches from fueling mode of operation to non-fueling mode of operation while data provided by sensor  58  discloses that pneumatic pressure inside tank  28  is less than pressure P3 which is both greater than pressure P1 and equal to or less than pressure P2, clutch  50  is engaged to cause engine  12  to start operating compressor  26  and to continue operating compressor  26  so long as data provided by sensor  58  discloses that pneumatic pressure inside tank  28  continues to be less than or equal to pressure P2. Clutch  50  is disengaged to cause engine  12  to stop operating compressor  26  when data provided by sensor  58  discloses that pneumatic pressure inside tank  28  has become greater than pressure P2. 
         [0031]    When ECM  16  switches from fueling mode of operation to non-fueling mode of operation while data provided by sensor  58  discloses that pneumatic pressure inside tank  28  is both equal to or greater than pressure P3 and equal to or less than pressure P2, clutch  50  remains disengaged, causing engine  12  to continue not operating compressor  26 . During continuance of the non-fueling mode of operation, clutch  50  will become engaged to cause engine  12  to start operating compressor  26  when data provided by sensor  58  discloses that pneumatic pressure inside tank  28  has become less than pressure P3 and will become disengaged to cause engine  12  to stop operating compressor  26  when data provided by sensor  58  discloses that pneumatic pressure in tank  28  has become greater than pressure P2. 
         [0032]      FIG. 2  illustrates a second embodiment in which like reference numerals identify the same elements appearing in  FIG. 1 .  FIG. 2  differs from  FIG. 1  is that operation of compressor  26  is controlled by a regulator  64  rather than a clutch. Pulley  24  is mounted directly on input shaft  56  of compressor  26  so that input shaft  56  will always rotate with rotation of crankshaft  18 . However, compressor  26  will operate only when allowed by ECM  16  acting on regulator  64 . 
         [0033]    The strategy can be applied not only to a vehicle having a brake system as described above but to vehicles having various pneumatic loads including other and different types wheel brakes. The strategy can also be applied to other types of compressor drives such as a gear drive which could replace the belt drives shown in  FIGS. 1 and 2 .