Abstract:
A spool valve for a camshaft phasing system for an internal combustion engine. The spool valve includes a housing, a check valve, a retention clip, a spring and a hollow spool. The spring and hollow spool are disposed in a bore of the housing. The spring is disposed at least partly in a bore or retention pocket within the hollow spool, and biases between that element and an opposite inner surface of the housing facing the spool bore or retention pocket. The spool valve enables compact operation of a cam phasing system by selectively aligning oil pathways into and out of a camshaft phaser.

Description:
[0001]    This application claims the benefit of provisional U.S. Application No. 61/103,755, filed Oct. 8, 2008, which is hereby incorporated by reference, as if set forth fully herein. 
     
    
     TECHNICAL FIELD 
       [0002]    The invention relates to the field of variable cam timing and more particularly, relates to a spool valve that is used to control a camshaft phaser to vary the timing of a camshaft of an internal combustion engine. 
       RELATED ART 
       [0003]    U.S. Pat. No. 7,000,580, entitled “Control Valves with Integrated Check Valves”, by Franklin R. Smith et al., and issued on Feb. 21, 2006, generally shows a construction of a spool valve used in a camshaft phasing system with an integrated check valve. U.S. Pat. No. 7,000,580 is incorporated by reference herein in its entirety, as if set forth fully herein. 
         [0004]    Camshaft phasers are generally known in two forms, a piston-type phaser with an axially displaceable piston and a vane-type phaser with vanes that can be acted upon and pivoted in the circumferential direction. With either type, the camshaft phaser is fixedly mounted on the end of a camshaft. An example mounting may be performed as disclosed in U.S. Pat. No. 6,363,896, entitled “Camshaft Adjuster for Internal Combustion Engines”, by Wolfgang Speier, issued on Apr. 2, 2002, by the clamping screw forming the element of the camshaft phaser that effects centering relative to the camshaft. U.S. Pat. No. 6,363,896 is incorporated by reference herein in its entirety, as if set forth fully herein. 
         [0005]    In order to operate either of these types of phasers it is necessary to selectively supply hydraulic fluid to ports in order to initiate movement. The vane-type phaser, in particular, requires supply of hydraulic fluid, normally engine oil, to opposing chambers in the phaser in order to shift the vane within the phaser circumferentially and thus selectively phase cam timing. To accomplish this, spool valves are utilized, either external to the camshaft phaser or, as here, integrated in the phaser. 
         [0006]    Spool valves accomplish the task of supplying and purging hydraulic fluid from the required cavities of the camshaft phaser. An example spool valve known in the art may comprise a housing, a plurality of check valves to prevent oil purging, a perforated hollow spool, a spring, and various ports bringing oil to the valve and carrying oil away, as needed. An external force, often supplied by a magnet mounted on the end of the spool valve, moves the spool fore and aft. As the spool is displaced relative to the housing, annular spaces align with holes in the housing to allow oil egress or ingress. 
       SUMMARY OF THE INVENTION 
       [0007]    As with many components in the modern internal combustion engine and automobile, it can be useful to reduce weight and size of spool valves, along with a camshaft phaser, in general. 
         [0008]    An example aspect of the invention comprises a spool valve for a camshaft phaser, wherein a spring retention pocket is formed in the spool itself, and is used in place of a spring retention recess in the spool valve housings of known devices, providing a uniformly flat surface upon which the spring makes contact in exerting a force to return the spool to starting position. In one example embodiment of the invention, the assembly comprises a housing, a check valve, a hollow spool within the housing, and a spring inserted into a spring retention pocket within the spool. 
         [0009]    According to one example embodiment of the invention, the spool valve also comprises a spool with a reduced inner diameter (ID), requiring a smaller transition from the internal ID to the spring retention pocket. 
         [0010]    A further example aspect of the invention may utilize a chamfered end of the spool at the insertion point of the spring into the spring retention pocket. In addition, a further example embodiment may utilize a tapered spring at the contact surface with the spool valve housing. 
         [0011]    A method for operating the spool valve, as described above, also is provided. 
     
    
     
       DESCRIPTION OF DRAWINGS 
         [0012]    The above mentioned and other features and advantages of this invention, and the manner of attaining them, will become apparent and be better understood by reference to the following description of at least one example embodiment of the invention in conjunction with the accompanying drawings. A brief description of those drawings now follows. 
           [0013]      FIG. 1  is a cross sectional view of an example spool valve known in the art. 
           [0014]      FIG. 2  is a cross sectional view of a spool valve, according to an example embodiment of the invention. 
           [0015]      FIG. 3  is a cross-sectional view of a spool valve, according to another example embodiment of the invention with a reduced internal diameter of a spool thereof. 
           [0016]      FIG. 4  is a cross-sectional view of a spool valve, according to another example embodiment of the invention with a chamfered retention pocket. 
           [0017]      FIG. 5  is a cross sectional view of a spool valve, according to a further example embodiment of the invention with a tapered spring. 
           [0018]      FIG. 6  is a perspective cross sectional view of a camshaft phasing assembly including the spool valve of  FIG. 2 . 
           [0019]      FIG. 7  is a cross sectional view of the camshaft phasing assembly of  FIG. 6  taken along line A-A of  FIG. 6 . 
       
    
    
       [0020]    Identically labeled elements appearing in different one of the figures refer to the same elements but may not be referenced in the description for all figures. The exemplification set out herein illustrates at least one example embodiment of the invention, in at least one form, and such exemplification is not to be construed as limiting the scope of the invention in any manner. 
       DETAILED DESCRIPTION 
       [0021]    It is well known in the art that for obtaining the most effective and fuel saving operation possible of an internal combustion engine, it can be useful to change cam lobe (lift event) timing to crank shaft timing while the engine is operating. Camshaft phasers replace sprockets or pulleys on camshafts. The cam lobe angular position, or phase relationship, is controlled by the internal vane mechanism of the cam phaser. These vanes are moved circumferentially around the cam phaser by the use of oil supplied to either side of the vane, advancing or retarding the camshaft position. Commands from the engine control module (or central engine computer) adjust the position of a spool in the oil control valve, in turn, controlling the oil flow. According to an example aspect of the invention, this function can be achieved in a small space, utilizing less material and reducing mass of the system with improved ease of assembly as compared to known systems by incorporating a spring retention pocket in the spool, and removing the existing recess in the spool valve housing. 
         [0022]      FIG. 1  shows a cross section of a known embodiment of a spool valve  1 , shown with an integrated check valve as described in U.S. Pat. No. 7,000,580 and an integrated clamping screw as described in U.S. Pat. No. 6,363,896. Spool valve  1  comprises spool valve housing  2 , spring  3 , spool  4 , one or more check valves  5 , one or more annular ridges  6 , spool housing spring retention recess  8 , spool inner diameter oil channel  9 , spool spring groove  10  and retention clip  11 . In this valve  1 , spring  3  is provided in housing spring retention recess  8  prior to assembling spool  4  into spool valve housing  2 . A limitation of such a construction can occur when spring  3  is improperly seated and comes into contact with contact chamfer  7  of spool  4 , causing pinching or other functional or assembly problems of spring  3 . External force  31  is shown applied in the indicated direction in order to displace spool  4  within housing  2  and effect the valve operation. 
         [0023]      FIG. 2  is a cross section of a spool valve  12  constructed according to an example embodiment of the invention. Spool valve  12  comprises spool valve housing  2 , spring  13  with a reduced diameter relative to spring  3 , one or more check valves  5 , one or more annular ridges  6 , spool spring retention pocket  14  formed in spool  4 , spool spring retention pocket channel  15 , and spool inner diameter oil channel  9 . Although three annular ridges  6 , and one check valve  5  are shown, any number of annular ridges  6 , and check valves  5  are anticipated by the invention. Consecutive annular ridges  6  form spaces between them, allowing passage of oil between the ridges  6 , while ridges  6  maintain contact with the inside diameter wall of housing  2  to prevent oil flow between the ridges  6  and housing  2 . Also shown are retention clip  11 , oil access path  16 , oil ports  17 , oil exhaust A  18 , oil exhaust B  19 , oil port A  20 , and oil port B  21 . In this example embodiment, spring  13  may be inserted into spring retention pocket  14  prior to both being assembled into housing  2 , eliminating or substantially reducing the possibility of improper placement of spring  13  within valve  12  upon assembly. In addition, further reduction in mass and size of spool valve  12  may be accomplished by reducing the size of spring  13  and spool  4  and eliminating material from spool housing  2  between points B and C. 
         [0024]      FIG. 3  shows a cross section of a spool valve  24  according to another example embodiment of the invention. Valve  24  is similar to valve  12  of  FIG. 2 , except that the spool inner diameter oil channel  9  is reduced in diameter relative to that of valve  12  due to the non-inclusion in valve  24  of a transition diameter formed by spool spring retention pocket channel  15  of spool inner diameter oil channel  9  included in the valve  12  of  FIG. 2 . Similar to valve  12  of  FIG. 2 , spool valve  24  comprises spool valve housing  2 , reduced diameter spring  13 , one or more check valves  5 , one or more annular ridges  6 , spool spring retention pocket  14  formed in spool  4 , and spool inner diameter oil channel  9 . Although three annular ridges  6 , and one check valve  5  are shown, any number of annular ridges  6 , and check valves  5  are anticipated by the invention. Also shown are retention clip  11 , oil access path  16 , oil ports  17 , oil exhaust A  18 , oil exhaust B  19 , oil port A  20 , and oil port B  21 . Reducing the diameter of oil channel  9  and not including channel  15  can be useful to ease machining of spool  4  and flow of hydraulic fluid through channel  9 . 
         [0025]      FIG. 4  shows a cross section of a spool valve  25  according to another example embodiment of the invention, wherein the valve  25  is like that of  FIG. 2  but the spool spring retention pocket  14  includes a lead-in chamfer  26  to guide spring  13  into pocket  14  and prevent spring  13  from becoming deformed by improperly contacting a sharp corner during insertion of spring  13  into pocket  14 . Instead of or in conjunction with lead-in chamfer  26 , the edge portion of spool  4  at the location of chamfer  26  may be widened or otherwise displaced apart to allow for a wider opening to receive spring  13 . 
         [0026]      FIG. 5  shows a spool valve  27  according to another example embodiment of the invention, wherein the valve  27  is like that of  FIG. 2 , except that reduced diameter spring  13  is replaced with another spring  29  that includes a tapered portion  28  where it contacts the spool valve housing  2 . Although the spring  29  has a tapered portion  28  in this example embodiment, variation of the spring  29  diameter in other manners besides that depicted, is also anticipated by this invention. 
         [0027]      FIG. 6  shows a perspective cross sectional view of an example embodiment of a camshaft phasing assembly  30 , including spool valve  12  and  FIG. 7  shows the camshaft phasing assembly  30  of  FIG. 6 , taken along line A-A of  FIG. 6 . In this example embodiment, hydraulic fluid enters the spool  4  of spool valve  12  through oil access port  36  in camshaft phaser  32  and oil port  17  in spool valve  12 . Spool  4 &#39;s position within housing  2  controls hydraulic fluid entering and exiting associated cam phaser  32 . Cam phaser  32  is controlled by hydraulic fluid entering and exiting one side of camshaft phaser vane  35  of camshaft phaser  32  through spool valve oil port B  21  in spool valve  12  and camshaft phaser oil port B  34  in phaser  32 . Similarly, oil enters and exits the other side of vane  35  through spool valve oil port A  20  in spool valve  12  and camshaft phaser oil port A  37  within camshaft phaser  32 . By controlling fluid flow to one side of vane  35  or the other in such a manner, vane  35  is moved circumferentially around camshaft phaser  32 , phasing the associated camshaft (not shown) on the end of which camshaft phasing assembly  30  is assembled. Also shown is sprocket  33  which is driven by a chain (not shown) generally from the engine crankshaft (not shown). Although a sprocket  33  is shown, any other form of driving mechanism also can be employed. 
         [0028]    According to an example aspect of the invention, for each of the embodiments depicted in  FIGS. 2-5 , the spring  13  ( FIGS. 2-4 ) or spring  29  ( FIG. 5 ) can be assembled into spool retention pocket  14 , both of which can be inserted into spool  4 , which then can be collectively inserted into housing  2 . Then retention clip  11  can be inserted in order to retain those components in the housing  2  in the manner shown. In addition, this can be done with a smaller mass and volume of material in the example spool valves,  12  ( FIG. 2 ),  24  ( FIG. 3 ),  25  ( FIGS. 4 ), and  27  ( FIG. 5 ), as described above. 
         [0029]    The manner in which hydraulic fluid is supplied for a camshaft phasing operation according to an example aspect of the invention will now be described with reference to  FIGS. 2-7 . Oil at typical system pressure is supplied through check valve  5 . This oil is filtered through oil supply passage  22 , entering external supply passages in cam phaser  32  through oil access path  16 . Oil re-enters the spool valve through camshaft phaser oil access port  36  and then through a plurality of oil ports  17 , filling a central annular space of spool  4  formed by annular ridges  6 . In the position shown, oil from spool valve  12  enters one side of a vane  35  of the cam phaser  32  through oil port A  20 , and oil exits the opposite side of vane  35  of the cam phaser  32  through oil port B  21 . The oil from port B  21  enters oil exhaust B  19 , and flows through spring retention pocket  14 , channel  15  (in the case of  FIGS. 2 ,  4  and  5 ), spool inner diameter oil channel  9 , and back into the engine oil system at oil exhaust port  23 . When the engine control module (ECM, not shown) supplies a signal to an external actuator (not shown) to provide a force  31  acting on spool  4 , spool  4  is displaced in such a manner that oil port A  20  aligns with oil exhaust A  18 , allowing oil from the one side of vane  35  of cam phaser  32  to exit from cam phaser  32 , and oil from port  17  is supplied to the opposite side of the cam phaser vane  35  through oil port B  21 . Oil exiting from cam phaser  32  through oil exhaust A  18 , flows into oil channel  9  and exits back into the engine system through oil exhaust  23 . 
         [0030]    When force  31  is removed, spring  13  exerts a force on spool  4  displacing spool  4  in such a manner that oil port A  20  aligns with the central annular space formed by ridges  6  on spool  4 , allowing communication with oil port  17  and providing oil to one side of vane  35 . In turn, oil exhaust B  19  aligns with oil port B  21 , allowing oil from the other side of vane  35  of cam phaser  32  to exit from cam phaser  32  through oil exhaust B  19  and into channel  9 . Oil from channel  9  exits camshaft phasing assembly  30  back into the engine system through oil exhaust  23 . 
         [0031]    A result of the above method is to actively change cam lobe (lift event) timing to crank shaft timing while the engine is operating, thus improving efficiency and performance of an internal combustion engine. 
         [0032]    In the foregoing description, example aspects of the invention are described with reference to specific example embodiments thereof. The specification and drawings are accordingly to be regarded in an illustrative rather than in a restrictive sense. It will, however, be evident that various modifications and changes may be made thereto, without departing from the broader spirit and scope of the present invention. 
         [0033]    In addition, it should be understood that the figures illustrated in the attachments, which highlight the functionality and advantages of the present invention, are presented for example purposes only. The architecture or construction of example aspects of the present invention is sufficiently flexible and configurable, such that it may be utilized (and navigated) in ways other than that shown in the accompanying figures. 
         [0034]    Although example aspects of this invention have been described in certain specific embodiments, many additional modifications and variations would be apparent to those skilled in the art. It is therefore to be understood that this invention may be practiced otherwise than as specifically described. Thus, the present example embodiments of the invention should be considered in all respects as illustrative and not restrictive.