Abstract:
A dual displacement engine system is provided including a first crankshaft for providing driving torque to a transmission and a second crankshaft that can be utilized to supplement the driving torque of the first engine crankshaft to meet higher torque demand requirements. An overrunning clutch device is provided for introducing the torque provided by the secondary engine crankshaft.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to a power unit for a vehicle and more particularly, a dual crankshaft engine coupling arrangement.  
         BACKGROUND AND SUMMARY OF THE INVENTION  
         [0002]    Internal combustion engines have been used for many years for providing motive power for driving a vehicle. Most vehicles on the road today are provided with either a four, six, or eight cylinder internal combustion engine which is selected based upon the typical torque demand requirements for the individual type vehicle being designed. For example, four cylinder engines are typically used for commuter vehicles which are compact and typically have low load requirements and limited performance expectations. Six cylinder and eight cylinder engines are typically employed in larger vehicles wherein larger load carrying capacity and higher performance are expected. Some of the existing vehicle designs have suffered from low fuel efficiency due to the fact that the internal combustion engine for the vehicle has to be designed with a sufficient capacity to meet the high torque demands that are only occasionally required.  
           [0003]    The dual displacement engine of the present invention overcomes these deficiencies by providing a powertrain system that includes a dual engine system with one of the engine portions being independently operable for providing driving torque to a transmission while the second engine portion can be utilized to supplement the driving torque of the first engine portion to meet higher torque demand requirements. Operation of the dual engine system is provided such that during normal driving at constant speeds and typical driving loads, the first engine portion is utilized for providing driving torque to the wheels of the vehicle. During periods of operation where increased levels of torque are required, such as during acceleration, pulling a heavy load, or climbing a hill, the second engine portion is operated in conjunction with the first engine portion for meeting the higher torque demand requirements. A coupling device is provided including an overrunning clutch in driving engagement with a drive member drivingly connected to the second crankshaft while an output shaft is in driving engagement with the first crankshaft and the overrunning clutch.  
           [0004]    Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0005]    [0005]FIG. 1 is a schematic view of a vehicle powertrain system incorporating a dual engine crankshaft coupling arrangement according to the principles of the present invention;  
         [0006]    [0006]FIG. 2 is a cross-sectional view of a coupling device for coupling a first and second crankshaft of a dual engine system according to the principles of the present invention;  
         [0007]    [0007]FIG. 3 is a schematic view of a vehicle powertrain system incorporating a dual engine crankshaft coupling arrangement according to a second embodiment of the present invention;  
         [0008]    [0008]FIG. 4 is a cross-sectional view of a coupling device for a dual engine crankshaft system according to the second embodiment of the present invention;  
         [0009]    [0009]FIG. 5 is a schematic diagram of the layout of the dual crankshaft system of the engine shown in FIG. 1; and  
         [0010]    [0010]FIG. 6 is a diagram of a control system of the dual engine power train system according to the principles of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0011]    The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses.  
         [0012]    With reference to FIG. 1, a vehicle  10  is shown provided with a power train system  12  including a dual displacement engine  14  (which will be described in greater detail herein) connected to an automatic transmission  16 . A pair of drive wheels  20  are drivingly connected to the transmission  16  via a differential  22 .  
         [0013]    The dual displacement engine  14 , as illustrated in FIG. 5, includes a primary engine portion  14 A including a primary or first crankshaft portion  24  having a plurality of pistons  26  connected thereto by corresponding connecting rods  28 . Each of the pistons  26  are disposed in a corresponding cylinder  30  as is well known in the engine art. For purposes of illustration, four pistons  26  are mounted to the first crankshaft portion  24 , although it should be understood that more or fewer pistons can be connected to the first crankshaft portion  24  without departing from the spirit and scope of the present invention.  
         [0014]    With continued reference to FIG. 5, a secondary engine portion  14 B including a second crankshaft portion  32  is drivingly coupled to the first crankshaft  24  by an overrunning clutch device  34 . A plurality of pistons  36  are connected to the second crankshaft  32  by corresponding connecting rods  38 . Each of the pistons  36  are disposed in a corresponding cylinder  42  as is well known in the engine art.  
         [0015]    A central processor unit  40  (FIG. 6) is provided for controlling the transmission  16 , as well as the primary and secondary engine systems  14 A,  14 B.  
         [0016]    A first embodiment of the coupling device, according to the principles of the present invention, is shown in FIG. 2. The coupling device  34  couples the two engine crankshafts  24 ,  32  in parallel such that a primary engine, connected directly to a transmission can be used to propel a vehicle for a majority of its operating time, and a second engine crankshaft can be coupled to the first engine crankshaft via the overrunning clutch device  34  when additional power is needed for rapid accelerations or high load operating conditions.  
         [0017]    As shown in FIG. 2, the primary engine crankshaft  24  is connected to a first input shaft  50  which is connected to an output coupling  52 , which is adapted to be connected to an input shaft of transmission  16 . A second input shaft  56  is connected to the second crankshaft  32 . A drive sprocket  58  is fixedly mounted to the second input shaft. A driven sprocket  60  is mounted on the first input shaft  50 . The overrunning clutch  34  is mounted inside a hub portion and the driven sprocket. A drive chain  62  is connected between the drive sprocket  58  and driven sprocket  60 . When the speed of the driven sprocket  60  is equal to the speed of the first input shaft  50 , the overrunning clutch  34  delivers torque to the first input shaft  50 .  
         [0018]    When it is determined by the central processor unit  40 , based on the driver&#39;s throttle pedal  96  position and movement, that the non-running secondary engine  14 B is needed to provide additional power to assist the primary engine  14 A, the non-running secondary engine  14 B can be started, brought up to the speed of the running primary engine  14 A, and used to supplement the torque provided by the primary engine. At a specific desirable speed threshold of the secondary engine crankshaft  32 , the secondary engine  14 A is provided fuel, air, and ignition control via the central processor unit  40  so that the second engine  14 B runs at a desired speed to provide needed torque.  
         [0019]    To turn off the secondary engine  14 B, it is only necessary to turn off the ignition and fuel to the secondary engine  14 B.  
         [0020]    According to an alternative embodiment, as illustrated in FIG. 3, each of the primary and secondary engine crankshafts  24 , 32  are axially offset from the overrunning clutch  34 . Specifically, a primary engine crankshaft  24  is connected to a first input shaft  80  having a first drive sprocket  82  mounted thereon. First drive sprocket  82  is drivingly connected to a first driven sprocket  84  by a drive chain  86 . The first driven sprocket  84  is fixedly mounted to an output shaft  88  having an output coupling  90  adapted to be connected to an input shaft of a transmission  16 . An overrunning clutch  34  is mounted within a driven sprocket  92  provided on the output shaft  88 . The driven sprocket  92  is driven by a second drive chain  94  which is driven by a second drive sprocket  96  mounted to a secondary input shaft  98 . The secondary input shaft  98  is connected to the secondary engine crankshaft  32 .  
         [0021]    During operation, the primary engine crankshaft  24  drives the first input shaft  80  which drives drive sprocket  82  for providing torque through the drive chain  86  to the first driven sprocket  84 . The driven sprocket  84  is fixedly mounted to the output shaft  88  for providing torque to the transmission  16 . When the vehicle controller  40  (FIG. 6) determines that additional torque is required, the secondary engine crankshaft engine  32  is started up and torque is delivered via the second input shaft  98 , second drive sprocket  96 , second driven chain  94 , and driven sprocket  92  and to the overrunning clutch  34  for providing additional torque to the output shaft  88 .  
         [0022]    In each of the embodiments disclosed above, the overrunning clutch  34  can be of a sprag type, roller type, vane type, or any other overrunning clutch as is known in the art.  
         [0023]    The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.