Patent Publication Number: US-6216654-B1

Title: Phase changing device

Description:
FIELD OF INVENTION 
     This invention relates to a valve train of an internal combustion engine and, more particularly, concerns a device for varying the timing of the opening and closing of the intake and/or exhaust valves with respect to the phase of the piston stroke. 
     BACKGROUND OF THE INVENTION 
     My U.S. Pat. No. 5,673,659 entitled “Lead Screw Driven Shaft Phase Control Mechanism”, issued on Oct. 7, 1997 and assigned to the assignee of this invention, discloses a mechanism that provides a selective timing or phase adjusting system between a drive gear and a driven camshaft with the drive gear being coaxially mounted and axially affixed with respect to the driven camshaft for rotation together. An intermediate connecting member is coaxially mounted with respect to the drive gear and the camshaft and is capable of axial movement and angular movement with respect to either the camshaft or the drive gear when experiencing its relative axial movement. The intermediate connection and a coupling member are connected to a geared device that is selectively activated by an electric motor which produces axial movement of both the intermediate connection and the coupling member with respect to the camshaft and the drive gear to any desired axial position between predetermined first and second positions. The gearing device provides a unidirectional drive system which allows the electric control motor to drive the mechanism to provide the optimum shaft phasing and is operably connected to a sleeve that is axially affixed to the intermediate connecting member. When in operation, the gearing device moves the sleeve axially, which in turn, moves the intermediate member axially with respect to both the drive gear and the camshaft. The intermediate connection member is an axially shifting member that has helical splines that rotationally affix it to the camshaft to allow relative rotation of the camshaft with respect to the drive gear. In one embodiment, the gearing device drives the sleeve while in another embodiment the gearing device is a threaded lead screw engaging complementary threads formed on the sleeve. In a third embodiment disclosed in the patent, the gearing device is a part of a gear sprocket that has an internally threaded hub that engages complementary external threads on the sleeve. 
     In my U.S. Pat. No. 5,860,328 entitled “SHAFT PHASE CONTROL MECHANISM WITH AN AXIALLY SHIFTABLE SPLINED MEMBER”, which issued Jan. 19, 1999 and assigned to the assignee of this invention, I disclose a two part variable valve timing system. In my co-pending patent application, Ser. No. 09/283,019, entitled “TWO PART VARIABLE VALVE TIMING MECHANISM”, filed on Apr. 1, 1999 and assigned to the assignee of this invention, I disclose a new form of power transmission that is substituted for the threaded jackscrew system which executes the axial motion of the shifting sleeve. Inasmuch as the lowest possible friction level is desired in phase changing devices to minimize wear and to allow use of a small electric motor for varying the position of the camshaft, it is important to have a transmission arrangement with less friction than an ACME screw. As stated in the aforementioned patent application, the optimum replacement for an ACME screw would be the ball-nut recirculating screw device which enjoys very low friction in operation. However, irrespective of the many advantages provided by such a device, using it for phase changing device is not possible from a practical standpoint because the required ball-return duct would interfere with the drive gear. Accordingly, in the mechanism covered by the above patent application, I have incorporated into the phase changing device one of the ball-nut transmissions disclosed in my co-pending patent application, Ser. No. 09/271,229, entitled “BALL-NUT TRANSMISSION”, filed on Mar. 17, 1999, and assigned to the assignee of this invention. 
     SUMMARY OF THE INVENTION 
     The present invention has certain similarities to the mechanism shown in my patent application, Ser. No. 09/283,019, entitled “TWO PART VARIABLE VALVE TIMING MECHANISM”, filed on Apr. 1, 1999, but differs therefrom in that the splined connection between the camshaft and the quill shaft, rather than being grouped together at one end or the other of the mechanism are, instead, separated so that the helical spline connection is incorporated with the control assembly and the straight spline connection is incorporated with the timing drive assembly. The advantage of so doing is to simplify the construction of the rear control assembly of the phase changing device. In addition, the power transmission includes one form of the ball-nut transmission disclosed in my above-mentioned co-pending patent application. 
     One object of the present invention is to provide a new and improved phase changing device that is provided with two major parts one of which is located at the front end of an internal combustion engine and the other is located at the rear end of the engine and in which the control section of the mechanism incorporates a ball-nut transmission for providing linear movement of a quill shaft interacting with straight splines incorporated with the timing drive assembly and helical splines incorporated with control section for changing the phase of a camshaft. 
     Another object of the present invention is to provide a new and improved phase changing device which has an axially movable quill shaft extending through a hollow camshaft and has one end of the quill shaft directly connected to the camshaft through helical splines and has the other end of the quill shaft connected by straight splines to the timing gear so that axial movement of the quill shaft provided by a ball nut transmission located at the other end of the quill shaft serves to rotate the camshaft a predetermined distance upon actuation of an electric stepper motor. 
     A further object of the present invention is to provide a new and improved phase changing device incorporating a non-recirculating ball-nut transmission for linearly moving a quill shaft and in which balls are encapsulated in hemispherical cavities formed in an axially movable sleeve surrounded by a nut member having a helical groove which cooperates with the balls for providing axial movement of the quill shaft and operates through helical splines at one end of the quill shaft to reposition the camshaft relative to the drive gear which forms a part of the timing gear assembly. 
     The above objects and others are realized in accordance with the invention by a phase changing device for an internal combustion engine that comprises a timing drive assembly located at one end of the engine and a control assembly located at the other end of the engine. The timing drive assembly has a drive gear adapted to be driven by the crankshaft of the engine and a hollow camshaft extends between the timing drive assembly and the control assembly. A quill shaft is co-axially mounted within the hollow camshaft and has a first portion located at the other end and is connected to the hollow camshaft by a plurality of helical splines surrounding the first portion of the quill shaft. A hub member is fixed with the drive gear and a second portion of the quill shaft is located at the above-mentioned one end of the engine and is connected to the hub member by a plurality of straight splines. An axially movable sleeve member is connected to and surrounds the first portion of the quill shaft located at the other end. A nut member surrounds the sleeve member and is drivingly connected to the sleeve member through a plurality of circumferentially spaced non-recirculating balls encapsulated in one of the members and located in a helical groove formed in the other of the members so that, upon rotation of the nut member, the sleeve member and the quill shaft move axially relative to the camshaft and simultaneously through the helical splines and the straight splines cause the camshaft to change its angular position with respect to the drive gear. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other objects and advantages of the present invention will be more apparent from the following detailed description of the invention when taken with the drawings in which: 
     FIG. 1 is a schematic representation of the phase changing device according to the present invention combined with an internal combustion engine with the timing drive assembly of the mechanism located at the front end of the engine and connected to the crankshaft of the engine and with the control assembly located at the rear of the engine; 
     FIG. 2 is an isometric view with parts broken away and some parts in section so as to show the various parts of the timing drive assembly of the phase changing device according to the present invention; and 
     FIG. 3 is an isometric view with parts broken away and some parts sectioned so as to show the various parts of the control assembly that is a part of the phase changing device according to the present invention; 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to the drawings and more particularly to FIG. 1 thereof, an in-line internal combustion engine  10  is shown schematically in block form as being equipped with a split or divided two-part phase changing device made in accordance with the present invention. The phase changing device shown is intended to be incorporated with the intake camshaft that operates a number of intake valves (not shown) disposed in the cylinder head  11  of the engine  10 . It will be understood that a similar phase changing device can control the exhaust camshaft of the engine  10 . 
     The phase changing device includes a timing drive assembly  12 , as shown in FIG. 2, that is mounted at the front end of the engine  10  and a control assembly  14 , as seen in FIG. 3, mounted at the rear of the engine  10 . One reason for splitting the timing drive assembly  12  from the control assembly  12  is that in transverse engine installations, there is little space at the front timing-end of the engine, but more space at the rear end of the engine over the transaxle. Accordingly, by dividing the phase changing device into two parts, the space available under the hood of an automobile is more efficiently utilized. 
     The crankshaft  16  of the engine is drivingly connected to the timing drive assembly  12  through a gearing arrangement  18  depicted, in this instance, by the dotted lines extending between the timing drive assembly  12  and the crankshaft  16 . Alternatively, rather than having a direct gearing arrangement for providing drive to the timing drive assembly  12 , a chain or belt drive can be used for this purpose in which case one sprocket would be connected to the crankshaft  16  and another sprocket would be a part of the timing drive assembly  12 . In either case, the drive provided to the timing drive assembly  12  would be a 2:1 speed ratio. 
     As seen in FIG. 2, the timing drive assembly  12  includes a drive gear  20  which is operatively associated with the front portion of a hollow camshaft  22 , the rear portion of which is operatively associated with the control assembly  14  seen in FIG. 3. A bearing sleeve  23  may be interposed between the drive gear  20  and the front portion of the camshaft  22 . An elongated and cylindrical quill shaft  24  extends through the hollow camshaft  22  and, in effect, interconnects the timing drive assembly  12  with the control assembly  14 . As will become more apparent as the description of the invention proceeds, axial movement of the quill shaft  24  relative to the camshaft  22  serves to change the timing or phase relationship between the camshaft  22  and the crankshaft  16 . 
     More specifically and as seen in FIG. 2, the front portion of the timing drive assembly  12  together with the camshaft  22  is supported for rotation by a bearing assembly  26  which includes a semi-cylindrical bearing cap  28  secured by bolts  30  (only one shown) to a bearing saddle  32  integrally formed as part of the cylinder head  11  of the engine  10 . In general, the timing drive assembly  12  comprises the drive gear  20 , a hub member  34 , and the front portions of the camshaft  22  and the quill shaft  24  all of which are interconnected for rotation about the longitudinal center axis of the camshaft  22 . The camshaft  22  is restrained from axial movement by a pair of integrally formed and axially spaced thrust flanges  38  and  40  which abut the opposed sides of the bearing assembly  26  and are annular in configuration. In addition, the drive gear  20  is secured from axial disengagement relative to the camshaft  22  by a thrust bearing-snap ring combination  41  in which the snap ring is located in a groove formed in the front end of the camshaft  22 . 
     The front portion of the quill shaft  24  extends through the camshaft  22  and has its front portion formed with a plurality of circumferentially and equally spaced straight splines  42  which mate with complementary straight splines  44  formed in a rearwardly extending cylindrical section  46  integral with the front end of the hub member  34 . The cylindrical section  46  is received within a counter-bore  48  formed in the front end of the camshaft  22 . A disk-shaped portion  50  of the hub member  34  is bolted to the drive gear  20  by a plurality of circumferentially spaced bolts, two of which are only shown in FIG.  2  and identified by reference numeral  52 . Each of the bolts  52  extends through a curved slot  54  formed in the circular portion  50  of the hub member  34  so as to permit limited angular adjustment of the drive gear  20  relative to the hub member  34  upon loosening of the bolts  52 . 
     The control assembly  14  seen in FIG. 3 is positioned at the rear of the engine  10  as aforementioned and as seen in FIG.  1  and provides the axial movement of the quill shaft  24  for a change in timing or phasing of the camshaft  22  relative to the crankshaft  16 . The control assembly  14 , in general, comprises the rear portion of the quill shaft  24 , the rear portion of the camshaft  22 , an axially movable sleeve member  56 , a nut member  58 , and a stepper motor  60 . The stepper motor  60  receives input pulses from an electronic control system (not shown) and is adapted to drivingly rotate the nut member  58  through a pair of gears  62  and  64 . 
     In most engines, the timing or phase relationship between a camshaft and a crankshaft is set and is not adjustable during the operation of the engine. However, various engine related operational conditions or parameters, such as speed, load, temperature, or other operative factors, are functional factors that together relate to an ideal timing or phasing of the camshaft relative to the crankshaft. The parameters or factors are sensed by various devices and inputted as signals to an electronic control unit (ECU) which then produces an appropriate desirable output control signal in the form of control pulses that can afterwards be fed to a stepper motor  60  such as in the control assembly  14  for ideal angular phasing of the camshaft. An ECU for providing such control pulses can be seen in my aforementioned U.S. Pat. No. 5,673,659 and attention is directed to that patent for a full explanation of the manner that the stepper motor  60  of this invention receives the input pulses from an ECU. 
     As seen in FIG. 3, the rear portion of the camshaft  22  is supported for rotative movement by a bearing cap  66  secured to a bearing saddle  68  integral with the cylinder head  11  of the engine  10 . The rear portion of the quill shaft  24  extends through the hollow camshaft  22  and terminates with a reduced diameter portion  70 . Forwardly of the reduced diameter portion  70 , a plurality of circumferentially and equally spaced helical splines  71  are formed on the rearward portion of the quill shaft  24 . The splines  71  mate with complementary helical splines  72  formed on the internal cylindrical surface of the rear portion of the camshaft  22 . The rear portion of the quill shaft  24  and the camshaft  22  are located in a housing  73  covering the internal parts of the control assembly  14 . The inner flange  74  of the housing  73  is secured to a plate  76  by a plurality of bolts, two of which are only shown in FIG.  3  and each is identified by the reference numeral  78 . The plate  76 , in turn, is secured to the cylinder head  11  by a plurality of bolts  80  ( one of which is only shown). The electric reversible D.C. stepper motor  60  is adapted to operate through a speed reducing gear set (not shown) located within a gear case  82  fastened to the housing  73  and serving to drive the gear  62  upon energization of the stepper motor  60 . 
     As seen in FIG. 3, the gear  62  meshes with the gear  64  which is integral with the nut member  58  that provides axial movement of the sleeve member  56 . In this regard, the nut member  58  is cylindrical in cross section and has its inner cylindrical surface formed with a semi-circular helical groove  84  simulating a screw thread. Similarly, the sleeve member  56  includes a cylindrical section  86  and has a plurality of spherical balls  88  each of which is disposed in an individual hemispherical cavity  89  formed in the outer cylindrical surface of the sleeve member  56 . The balls  88  are located along a helical path which matches the helical groove  84  formed in the nut member  58 . 
     The cylindrical section  86  of the sleeve member  56  is integrally formed with a radially inwardly extending flange  90  that is supported by a sleeve bearing  92  and a pair of thrust bearing  94  and  96  located on the reduced portion  70  of the quill shaft  24 . The thrust bearings  94  and  96  are held in place by a snap ring  98  located in an annular groove (not shown) formed in the rear end of the quill shaft  24 . The outer cylindrical surface of the sleeve member  56  is connected to the housing  73  by a plurality of circumferentially spaced tongue and groove connections one which is only shown consisting of a longitudinally extending groove  100  and a set screw  102 . As should be apparent, the lower cylindrical end of the set screw  102  is located in the groove  100  so as to restrict the sleeve member  56  and the quill shaft to axial movement relative to the housing  73  and the camshaft  22 . 
     The phase changing device composed of the timing drive assembly  12  and the control assembly  14  seen in FIGS. 2 and 3 and described above operates as follows: 
     When the stepper motor  60  receives an input signal and pulses from the ECU calling for a phase change of the camshaft  22 , the gear  62  will be drivingly rotated a predetermined amount and in a direction as dictated by the input signal and pulses. The rotation of the gear  62  will cause corresponding rotation of the nut member  58  through the gear  64 . As the nut member  58  rotates about the sleeve member  56 , the helical groove  84  acts through the encapsulated balls  88  to cause the sleeve member  56 , together with the quill shaft  24 , to move axially relative to the camshaft  22  as controlled by the tongue and groove connections provided by each of the grooves  100  and cooperating set screws  102 . This axial movement causes the helical splines  71  on the quill shaft  24  to move along the complementary helical splines  72  of the camshaft  22  resulting in a rotation of the camshaft  22  relative to the drive gear  16 . This occurs due to the fact that the quill shaft  24  is restricted from any rotative movement by the straight splines  42  and  44  and the connection between the drive gear  16  and the hub member  34 . Thus, in this manner, a phase change in the operation of the valves of the engine  10  occurs by the repositioning of the camshaft  22  relative to the position of the drive gear  20 . 
     It should be noted that the sleeve member  56  connected to the nut member  58  through the helical groove  84  and the balls  88  constitutes a ball-nut transmission of the type shown in my co-pending patent application, Ser. No. 09/271,229 referred to earlier in this specification. Inasmuch as the balls  88  are located in the hemispherical cavities  89  and encapsulated between the individual cavity supporting each ball  88  and the groove  84  in the nut member  58 , this ball-nut transmission provides an efficient linear movement of the sleeve member  56  with a minimum of friction and without the need for a return duct for the balls as found in the conventional ball-nut-screw devices. 
     Various changes and modifications can be made in the phase changing devices described above without departing from the spirit of the invention. Such changes and modifications are contemplated by the inventor and he does not wish to be limited except by the scope of the appended claims.