Abstract:
A variable cam timing phaser for an internal combustion engine having a concentric camshaft can include a stator ( 14 ) having an axis of rotation. An outer rotor ( 20 ) can rotate independently relative to the axis of rotation of the stator ( 14 ). A combination of an outer vane ( 22 ) and cavity ( 20   a ) can be associated with the outer rotor ( 20 ) to define first and second outer variable volume working chambers ( 20   b,    20   c ). A radially inner located rotor ( 30 ) can rotate relative to the axis of rotation and independently of both the stator ( 14 ) and the outer rotor ( 20 ). A combination of an inner vane ( 32 ) and a cavity ( 30   a ) can be associated with the inner rotor ( 20 ) to define first and second inner variable volume working chambers ( 30   b,    30   c ). When the first and second, outer and inner chambers ( 20   b,    30   b,    20   c,    30   c ) selectively communicate with a source of pressurized fluid, phase orientation of the outer and inner rotors ( 20, 30 ) with respect to one another and with respect to the stator ( 14 ) is facilitated.

Description:
FIELD OF THE INVENTION 
       [0001]    The invention relates to a mechanism intermediate a crankshaft and a poppet-type intake or exhaust valve of an internal combustion engine for operating at least one such valve, wherein the mechanism varies the time period relative to the operating cycle of the engine, and more particularly, wherein the mechanism operably engages with a concentric camshaft to vary an angular position of one camshaft and an associated cam relative to another camshaft and associated cam. 
       BACKGROUND 
       [0002]    The performance of an internal combustion engine can be improved by the use of dual camshafts, one to operate the intake valves of the various cylinders of the engine and the other to operate the exhaust valves. Typically, one of such camshafts is driven by the crankshaft of the engine, through a sprocket and chain drive or a belt drive, and the other of such camshafts is driven by the first, through a second sprocket and chain drive or a second belt drive. Alternatively, both of the camshafts can be driven by a single crankshaft powered chain drive or belt drive. A crankshaft can take power from the pistons to drive at least one transmission and at least one camshaft. Engine performance in an engine with dual camshafts can be further improved, in terms of idle quality, fuel economy, reduced emissions or increased torque, by changing the positional relationship of one of the camshafts, usually the camshaft which operates the intake valves of the engine, relative to the other camshaft and relative to the crankshaft, to thereby vary the timing of the engine in terms of the operation of intake valves relative to its exhaust valves or in terms of the operation of its valves relative to the position of the crankshaft. 
         [0003]    As is conventional in the art, there can be one or more camshafts per engine. A camshaft can be driven by a belt, or a chain, or one or more gears, or another camshaft. One or more lobes can exist on a camshaft to push on one or more valves. A multiple camshaft engine typically has one camshaft for exhaust valves, one camshaft for intake valves. A “V” type engine usually has two camshafts (one for each bank) or four camshafts (intake and exhaust for each bank). 
         [0004]    Variable cam timing (VCT) devices are generally known in the art, such as U.S. Pat. No. 7,841,311; U.S. Pat. No. 7,789,054; U.S. Pat. No. 7,270,096; U.S. Pat. No. 6,725,817; U.S. Pat. No. 6,244,230; and U.S. Published Application No. 2010/0050967. Known patents and publications disclose hydraulic couplings for single phaser assemblies in which an annular space is provided between a drive member concentrically surrounding a single driven member. The annular space is divided into segment-shaped or arcuate variable volume working chambers by one or more vanes extending radially inward from an inner surface of the drive member and one or more vanes extending radially outward from an outer surface of the single driven member. As hydraulic fluid is admitted into and expelled from the various chambers, the vanes rotate relative to one another and thereby vary the relative angular position of the drive member and the single driven member. Hydraulic couplings that use radial vanes to apply a tangentially acting force will be referred to herein as vane-type hydraulic couplings. Each of these prior known patents and publications appears to be suitable for its intended purpose. However, dual variable cam timing (VCT) devices with variable volume working chambers that are positioned axially spaced with respect to one another require additional axial space for the dual VCT assembly, while those dual VCT devices with variable volume working chambers that are positioned circumferentially spaced with respect to one another potentially suffer from reduced angular actuation distance of the associated rotor and vane, and can potentially suffer from reduced actuation force as a result of limited number of vanes, limited vane surface area, and limited actuation fluid chamber size. Therefore, it would be desirable to provide a configuration that requires less axial space for a dual VCT assembly. It would also be desirable to provide increased angular actuation distances for a dual VCT assembly. Further, it would be desirable to provide increased actuation force capabilities for a dual VCT assembly. 
       SUMMARY 
       [0005]    A dual variable cam timing phaser can be driven by power transferred from an engine crankshaft and delivered to a concentric camshaft having a radially inner shaft and a radially outer shaft for manipulating two sets of cams. The phaser can include a drive stator connectible for rotation with an engine crankshaft and two concentric driven rotors, each rotor connectible for rotation with a respective one shaft of the concentric camshaft supporting the corresponding two sets of cams. The drive stator and the driven rotors are all mounted for rotation about a common axis. The driven rotors are coupled for rotation with the drive stator by a plurality of radially stacked, (as opposed to axially stacked or circumferentially stacked), vane-type hydraulic couplings to enable the phase of the driven rotors to be adjusted independently of one another relative to the drive stator. It should be recognized that this configuration requires less axial space for a dual VCT assembly. Furthermore, this configuration can provide increased angular actuation distances for a dual VCT assembly. This configuration can also provide increased actuation force capabilities for a dual VCT assembly. 
         [0006]    A dual variable cam timing phaser for an internal combustion engine having a concentric camshaft with a radially inner shaft and a radially outer shaft can include a stator having an axis of rotation. An outer rotor can be rotatable relative to the axis of rotation of the stator independently of the stator. A radially outer located vane-type hydraulic coupling can include a combination of an outer vane and cavity associated with the outer rotor to define first and second outer variable volume working chambers. An inner rotor can be rotatable relative to the axis of rotation of the stator independently of both the stator and the outer rotor. The inner rotor can be located radially inwardly within an innermost periphery of the outer rotor. A radially inner located vane-type hydraulic coupling can include a combination of an inner vane and cavity associated with the inner rotor to define first and second inner variable volume working chambers. A plurality of fluid passages can connect the first and second, outer and inner working chambers with respect to a source of pressurized fluid for facilitating angular phase orientation of the outer and inner rotors independently with respect to each other and independently with respect to the stator. 
         [0007]    Other applications of the present invention will become apparent to those skilled in the art when the following description of the best mode contemplated for practicing the invention is read in conjunction with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    The description herein makes reference to the accompanying drawings wherein like reference numerals refer to like parts throughout the several views, and wherein: 
           [0009]      FIG. 1  is a cross sectional view taken transverse to an axis of rotation of a dual variable cam timing phaser for an internal combustion engine having a concentric camshaft according to the present invention; 
           [0010]      FIG. 2  is a cross sectional view taken along an axis of rotation of the dual variable cam timing phaser of  FIG. 1 ; 
           [0011]      FIG. 3  is a perspective end view of the dual variable cam timing phaser of  FIGS. 1-2 ; 
           [0012]      FIG. 4  is a cross sectional view taken transverse to an axis of rotation of a dual variable cam timing phaser for an internal combustion engine having a concentric camshaft according to another configuration of the present invention; 
           [0013]      FIG. 5  is a cross sectional view taken along an axis of rotation of the dual variable cam timing phaser of  FIG. 4 ; 
           [0014]      FIG. 6  is a perspective end view of the dual variable cam timing phaser of  FIGS. 4-5 . 
       
    
    
     DETAILED DESCRIPTION 
       [0015]    Referring now to  FIGS. 1-3 , a dual variable cam timing phaser  10  can be driven by power transferred from an engine crankshaft (not shown) to be delivered to a concentric camshaft  12  for manipulating two sets of cams (not shown). A portion of a variable cam timing (VCT) assembly  10  is illustrated including the concentric camshaft  12  having an inner shaft  12   a  and an outer shaft  12   b . Primary rotary motion can be transferred to the concentric camshaft  12  through the sprocket ring  52  of annular flange  16  operably associated with drive stator  14 . Secondary rotary motion, or phased relative rotary motion between inner camshaft  12   a  and outer camshaft  12   b , can be provided by the dual variable cam timing phaser  10 . The phaser  10  can include the drive stator  14  to be connected by an endless loop, flexible, power transmission member for rotation with the engine crankshaft. Two concentric driven rotors  20 ,  30  can be associated with the stator  14 . Each rotor  20 ,  30  can be connected for rotation with a respective one shaft  12   a ,  12   b  of the concentric camshaft  12  supporting the corresponding two sets of cams. The drive stator  14  and the driven rotors  20 ,  30  are all mounted for rotation about a common axis. A plurality of radially stacked, vane-type hydraulic couplings  40 ,  50  for coupling the driven rotors  20 ,  30  for rotation with the drive stator  14  enable the phase of the driven rotors  20 ,  30  to be adjusted independently of one another relative to the drive stator  14 . 
         [0016]    The plurality of radially stacked, vane-type hydraulic couplings can include a radially outer located vane-type hydraulic coupling  40  and a radially inner located vane-type hydraulic coupling  50 . The radially outer located vane-type hydraulic coupling  40  can include at least one radially outer located vane  22  and at least one corresponding radially outer located cavity  20   a  associated with the radially outer located rotor  20  to be divided by the at least one radially outer located vane  22  into a first outer variable volume working chamber  20   b  and a second outer variable volume working chamber  20   c . The radially inner located vane-type hydraulic coupling  50  can include at least one radially inner located vane  32  and at least one corresponding radially inner located cavity  30   a  adjacent the radially inner located rotor  30  to be divided by the at least one radially inner located vane  32  into a first inner variable volume working chamber  30   b  and a second inner variable volume working chamber  30   c.    
         [0017]    The radially outer located vane-type hydraulic coupling  40  can include a combination of an outer vane  22  and cavity  20   a  associated with the outer rotor  20  to define first and second outer variable volume working chambers  20   b ,  20   c . The combination of the outer vane  22  and cavity  20   a  can be defined by the stator  14  having a wall portion  14   a  with a radially outer surface  14   b  defining the outer vane  22 , and the outer rotor  20  surrounding the radially outer surface  14   b  of the stator  14  to define the outer cavity  20   a . The radially inner located vane-type hydraulic coupling  50  can include a combination of an inner vane  32  and cavity  30   a  associated with the inner rotor  30  to define first and second inner variable volume working chambers  30   b ,  30   c . The combination of the inner vane  32  and cavity  30   a  can be defined by the stator  14  having a wall  14   a  with a radially inner surface  14   c  defining the inner cavity  30   a , and the inner rotor  30  having an outer surface  30   d  defining the inner vane  32 . 
         [0018]    As best seen in  FIGS. 1 and 2 , the drive stator  14  is connected to the annular flange  16  and associated sprocket ring  52  through fasteners  24 . Outer rotor  20  is connected to inner concentric camshaft  12   a  through end plate  34 , outer fasteners  36  and central fastener  38 . Inner rotor  30  is directly connected to an outer surface  42  of outer concentric camshaft  12   b.    
         [0019]    In operation, a dual variable cam timing phaser  10  provides radially outer annular spaces or cavities  20   a  and radially inner annular spaces or cavities  30   a  with respect to the drive stator  14  and the concentrically located driven outer and inner rotors  20 ,  30 . The annular spaces or cavities  20   a ,  30   a  are divided into segment-shaped or arcuate variable volume working chambers  20   b ,  20   c ,  30   b ,  30   c  by outer and inner vanes  22 ,  32  extending radially from a surface of the outer and inner rotors  20 ,  30  and one or more vanes or walls  18  extending radially from a surface of the drive stator  14 . As hydraulic fluid is admitted into and expelled from the various chambers  20   b ,  20   c ,  30   b ,  30   c , the vanes  22 ,  32  rotate relative to one another and thereby vary the relative angular position of the driven outer and inner rotors  20 ,  30  with respect to each other and with respect to the stator  14 . 
         [0020]    Referring now to  FIGS. 4-6 , and as previously described with respect to  FIGS. 1-3 , a dual variable cam timing phaser  10  can be driven by power transferred from an engine crankshaft (not shown) to be delivered to a concentric camshaft  12  for manipulating two sets of cams (not shown). A portion of a variable cam timing (VCT) phaser assembly  10  is illustrated including the concentric camshaft  12  having an inner camshaft  12   a  and an outer camshaft  12   b . Primary rotary motion can be transferred to the concentric camshaft  12  through the assembly of sprocket ring  52  to annular flange  16  operably associated with drive stator  14 . Secondary rotary motion, or phased relative rotary motion between inner camshaft  12   a  and outer camshaft  12   b , can be provided by the dual variable cam timing phaser  10 . The phaser  10  can include the drive stator  14  to be connected for rotation with the engine crankshaft. Two concentric driven rotors  20 ,  30  can be associated with the stator  14 . Each rotor  20 ,  30  can be connected for rotation with a respective one of the concentric camshafts  12  supporting the corresponding two sets of cams. The drive stator  14  and the driven rotors  20 ,  30  are all mounted for rotation about a common axis. A plurality of radially stacked, vane-type hydraulic couplings  40 ,  50  for coupling the driven rotors  20 ,  30  for rotation with the drive stator  14  enable the phase of the driven rotors  20 ,  30  to be adjusted independently of one another relative to the drive stator  14 . In this configuration, the stator  14  includes a radially outer wall portion  14   d , and a radially inner wall portion  14   f.    
         [0021]    The plurality of radially stacked, vane-type hydraulic couplings can include a radially outer located vane-type hydraulic coupling  40  and a radially inner located vane-type hydraulic coupling  50 . The radially outer located vane-type hydraulic coupling  40  can include at least one radially outer located vane  22  and at least one corresponding radially outer located cavity  20   a  associated with the radially outer located rotor  20  to be divided by the at least one radially outer located vane  22  into a first outer variable volume working chamber  20   b  and a second outer variable volume working chamber  20   c . The radially inner located vane-type hydraulic coupling  50  can include at least one radially inner located vane  32  and at least one corresponding radially inner located cavity  30   a  adjacent the radially inner located rotor  30  to be divided by the at least one radially inner located vane  32  into a first inner variable volume working chamber  30   b  and a second inner variable volume working chamber  30   c.    
         [0022]    The radially outer located vane-type hydraulic coupling  40  can include a combination of an outer vane  22  and cavity  20   a  associated with the outer rotor  20  to define first and second outer variable volume working chambers  20   b ,  20   c . The combination of the outer vane  22  and cavity  20   a  can be defined by the stator  14  having a radially outer wall portion  14   d  with an inner surface  14   e  defining the outer cavity  20   a , and the outer rotor  20  having an outer surface  20   d  defining the outer vane  22 . The radially inner located vane-type hydraulic coupling  50  can include a combination of an inner vane  32  and cavity  30   a  associated with the inner rotor  30  to define first and second inner variable volume working chambers  30   b ,  30   c . The combination of the inner vane  32  and cavity  30   a  can be defined by the stator  14  having a radially inner wall portion  14   f  interposed radially between the outer rotor  20  and the inner rotor  30 . The inner wall portion  14   f  can have a radially inner surface  14   g  defining the inner cavity  30   a , and the inner rotor  30  can have an outer surface  30   d  defining the inner vane  32 . 
         [0023]    As best seen in  FIGS. 4-5 , the outer wall portion  14   d  of drive stator  14  is connected to the flange  16  and associated sprocket ring  52  through fasteners  24 . Outer rotor  20  is connected to inner concentric camshaft  12   a  through end plate  34 , outer fasteners  36 , and central fastener  38 . The inner wall portion  14   f  of drive stator  14  is connected to the flange  16  and associated sprocket ring  52  through fasteners  26 . The inner rotor  30  is connected directly to an outer surface  42  of the outer concentric camshaft  12   b.    
         [0024]    In operation, a dual variable cam timing phaser assembly provides radially outer annular spaces or cavities  20   a  and radially inner annular spaces or cavities  30   a  with respect to the drive stator  14  and the concentrically located driven outer and inner rotors  20 ,  30 . The annular spaces or cavities  20   a ,  30   a  are divided into segment-shaped or arcuate variable volume working chambers  20   b ,  20   c ,  30   b ,  30   c  by outer and inner vanes  22 ,  32  extending radially from a surface of the outer and inner rotors  20 ,  30  and one or more vanes or walls  18  extending radially from a surface of the drive stator  14 . As hydraulic fluid is admitted into and expelled from the various chambers  20   b ,  20   c ,  30   b ,  30   c , the vanes  22 ,  32  rotate relative to one another and thereby vary the relative angular position of the driven outer and inner rotors  20 ,  30  with respect to each other and with respect to the stator  14 . 
         [0025]    While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiments but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims, which scope is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures as is permitted under the law.