Abstract:
Deactivation apparatus for selected cylinders of an engine include switching hydraulic lash adjusters or valve lifters forming part of a valve train for actuating engine valves of the selected cylinders and operable to actuate or release their respective valves in response to an oil pressure signal. A gallery carrying the lash adjusters includes oil passages fed by an engine pressure oil supply through a control valve to supply oil to switching portions of the lash adjusters. The control valve is operative to close or open communication of the oil supply with the lash adjusters and to relieve oil pressure in the passages when communication with the pressure oil supply is closed. Various bypass alternatives between the pressure oil supply and the oil passages carry oil to portions of the oil passages to purge air from the passages when the three-way valve exhaust port is open.

Description:
TECHNICAL FIELD 
     This invention relates to engine cylinder deactivation apparatus and, in particular, to hydraulic lost motion deactivation apparatus incorporating a gas/vapor purge. 
     BACKGROUND OF THE INVENTION 
     It is known in the art of engine cylinder deactivation to provide switchable hydraulic lash adjusters operable to either actuate the valves of a deactivation cylinder or to maintain the valves closed through lost motion features of the hydraulic lash adjusters (HLA). Similar mechanisms may be provided in a hydraulic valve lifter (HVL) which includes internally a hydraulic lash adjusting mechanism and so may be referred to broadly as a hydraulic lash adjuster. 
     Conventional lash adjusters are supplied with pressurized oil through a lash adjuster gallery or lifter gallery to annular feed grooves or intake ports which provide oil pressure to take up the lash in the valve train between the valve and its associated tappet or other-actuator. Lash adjusters and valve lifters with cylinder deactivation have an additional port for a lock pin which connects through control passages and a control channel with a valved oil pressure supply. A three-way solenoid-actuated hydraulic control valve may be used to connect oil pressure to the lock pin for cylinder deactivation or switching of the lash adjusters in a supply mode of the three-way valve and to exhaust oil pressure from the oil passages and control gallery in an exhaust mode. 
     Such cylinder deactivation apparatus typically use complex systems of bypass channels and hydraulic bleeds in order to purge air or other gas/vapor from the system to insure consistent response to control signals. This is necessary to provide reliable actuation or deactivation of the switchable hydraulic lash adjusters in the apparatus when the hydraulic control valve is actuated to make a change in operation. These bleed and bypass systems may add considerable complexity to the deactivation apparatus itself. Thus, a simplified system for purging gas/vapor, primarily air, from the hydraulic cylinder deactivation apparatus is desired. 
     SUMMARY OF THE INVENTION 
     The present invention provides simplified cylinder deactivation apparatus wherein the oil supply passages and control channels utilized for actuating the switchable hydraulic lash adjusters are purged of air with oil flow through restricted bypass means from the pressure oil supply. The control channel or the complete oil passage and control channel system are purged by exhausting the bypass oil flow through a solenoid-actuated hydraulic control valve exhaust port during engine start up and optionally during operation in the non-pressurized mode of the cylinder deactivation apparatus. 
     In one embodiment, a restricted bypass from the oil pressure supply enters the control channel at a distal end and is exhausted from the control channel through the solenoid valve exhaust port at the other end of the control channel adjacent the control valve. Air or other gas or vapor accumulating in the control channel is thus purged from the system during early stages of the engine operation. 
     In an alternative embodiment, the pressure oil supply from the lash adjuster gallery to the lash adjuster or valve lifter inlet is connected at each of the switchable lash adjusters with the deactivation port of the respective lifter through a restricted bypass groove in the lifter body. When the deactivation supply pressure is shut off by the hydraulic control valve, pressure oil is fed through the restricted bypass in each lash adjuster body to the gallery passages and control channel of the deactivation apparatus. The oil thus supplied purges the system of air which is exhausted from the system through the open exhaust valve of the three-way hydraulic control valve. 
     In both cases, when the control valve is actuated to close the exhaust and open the supply line, pressure oil is fed through the control channel and associated passages to the switchable hydraulic lash adjusters at the deactivation ports, thereby switching the lash adjusters to deactivated mode. In this condition, the oil pressure supplied to the deactivation channels and passages balances the pressure supplied to the lash adjuster mechanism itself and thus there is no loss of oil or purge flow through the system. With these arrangements, the purging of air from the control channel and connecting passages is accomplished primarily through the control channel and connecting passages themselves, without the need for additional separate channels and bleed passages that add to the complexity of the system. 
     In modifications of the two foregoing embodiments, a hydraulic seal is added to the lifter body. An annular channel is provided below the locking pin of each deactivation valve lifter and is supplied with pressurized oil through a vertical channel from the oil gallery. In one case, the annular channel is always below the associated control passage and the oil pressure prevents air from below the lifter gallery from entering the control passage and causing air bubbles that may interfere with the timing of deactivation actuation. In another case, the annular channel is positioned below the control passage on the actuating cam base circle but in alignment with the control passage when the cam raises the lifter to open an engine valve. In the lower position, the seal functions as in the first case above. However, when the lifter is raised cyclically as the cam rotates, oil passes from the oil gallery through the annular channel into the control passage to help flush aerated oil out of the system. Thus, entry of air from below the lifter gallery is prevented and, in the latter case, flushing of air out of the system is aided. 
    
    
     These and other features and advantages of the invention will be more fully understood from the following description of certain specific embodiments of the invention taken together with the accompanying drawings. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic diagram illustrating a first embodiment of cylinder deactivation apparatus utilizing switchable hydraulic valve lifters in a system purged of air by providing bypass oil flow to the control channel when the hydraulic control valve is in the exhaust mode; 
     FIG. 2 is a view similar to FIG. 1 wherein the purge oil flow is provided from the lifter gallery pressure oil supply through bypass grooves in the lifter body to the control passages and channel; 
     FIG. 3 is an enlarged pictorial view of a switchable hydraulic valve lifter with internal lash adjuster, illustrating the bypass groove arrangement; 
     FIG. 4 is a view similar to FIGS. 1 and 2 but showing a third embodiment in which stationary hydraulic lash adjusters are provided with purge oil flow from the gallery pressure oil feed and bypass grooves in the lifter bodies to purge oil from the system through the hydraulic control valve; 
     FIG. 5 is an enlarged pictorial view of a stationary hydraulic lash adjuster having a bypass groove according to the invention; 
     FIG. 6 is a view similar to FIG. 1 showing an alternative embodiment including a valve lifter with a lower hydraulic seal groove fed by a vertical groove from the oil gallery; 
     FIG. 7 is a view similar to FIG. 6 wherein the seal groove is raised to act as an air purge bypass during actuation of the lifter; and 
     FIG. 8 is a view similar to FIG. 7 showing the lifter in an actuated position wherein air purge oil flow occurs. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring first to FIG. 1 of the drawings in detail, numeral  10  generally indicates a first embodiment of cylinder deactivation apparatus including a purge bypass in accordance with the invention. Apparatus  10  includes a lifter gallery  12  having a plurality of through bores  14  containing hydraulic valve lifters  16 . Lifters  16  include roller followers  18  that are engaged by a camshaft, not shown, for actuating the lifters in timed relation to engine speed. Each lifter forms part of a valve train, not shown, which is connected to operate one of the valves of an engine cylinder that it is desired to deactivate by holding the cylinder valves closed during certain engine operating conditions. The valve lifters  16  are of a known deactivating or switching type which is actuated by an oil pressure signal to cause the lifter to telescope and allow its valve to remain closed while the engine is running. Upon removal of the oil pressure signal, the valve is again operated in a conventional manner. 
     The lifter gallery  12  includes a pressure oil supply passage or main gallery  20 , a portion of which communicates with annular feed grooves  22  that feed the pressure oil to lash adjusters contained within the valve lifters. Each of the lifters also has a locking pin  24  carried in a pin bore. The pin is exposed to control passages  26  extending in the lifter gallery  12  to a control channel  28  which may be internal or external to the lifter gallery. The control channel communicates with a solenoid-actuated hydraulic control valve  30  having a center port  32  alternately connectable with a supply port  34  and an exhaust port  36 . The supply port is connected with the engine main oil supply  38  which also feeds the lifter feed passages  20 . The exhaust port  36  returns discharged oil to the engine oil system. 
     In accordance with the invention, the main oil supply  38  is separately connected to the control channel  28  by a restricted bypass  40 . The bypass connects with the control channel  28  through a distal end  42  which is opposite to the feeder end  44  that connects directly with the center port  32  of the control valve. 
     In operation of the apparatus as described, the control valve  30  is de-energized when the engine is inoperative. The de-energized valve remains in an exhaust position, draining pressure oil from the control channel and locking pins of the associated lifters so that the lifters are placed in their normal operating positions. Upon starting of the engine, pressure is developed in the main oil system  38  and the engine operates normally on all cylinders. A restricted flow of oil is conducted through bypass  40  from the main oil supply  38  to the control channel  28 . As the oil passes through the control channel  28 , it carries with it air or gas-entrained oil which is purged from the system and carried out through the exhaust port  36  of the control valve. 
     After a predetermined interval, an engine power control module, not shown, is enabled to operate the solenoid control valve to deactivate selected ones of the engine cylinders having deactivating lifters. This is done only when engine operating conditions call for engine operation on less than all the engine cylinders. Cylinder deactivation is accomplished by opening the control valve  30  to feed pressure oil through the control channel  28  and passages  26  to disconnect the locking pins  24  of the lifters and allow the lifters to telescope within themselves. During deactivation, the valves connected with the deactivated lifters remain closed and the lifter followers oscillate freely without moving the valves from their seats. When conditions calling for all-cylinder operation are present, the solenoid valve is actuated to the exhaust position, removing pressure from the control passages and control channel and allowing the locking pins to reseat. Then the lifters again actuate the valves in their opening and closing motions as driven by the associated cams of the camshaft. 
     This embodiment of the invention provides purging of entrained air and other vapors and gases from the control channel  28  during start up of the engine and during other times when the lifters are operating normally and oil pressure in the control channel  28  is reduced. However, when the lifters are in the deactivation position, the control channel is pressurized with the same oil feed pressure as the main oil supply  38  so that there is no bypass flow between the supply  38  and the main oil channel. 
     Referring now to FIG. 2 of the drawings, numeral  46  generally indicates a second embodiment of cylinder deactivation apparatus. Apparatus  46  is similar in many ways to apparatus  10  previously described so that like numerals are used to indicate like parts. Apparatus  46  differs in that the restricted bypass  40  is omitted. Instead, bypass oil flow is provided through restricted grooves  48  formed in the deactivating or switching lifters  50 , which connect the annular feed grooves  22  of the lifter bodies  52  with the locking pin feed openings  54  that communicate with the control passages  26 . FIG. 3 shows an enlarged pictorial view illustrating the position of the restricted grooves in the lifters  50 . 
     In operation of embodiment  46  upon engine starting, main oil pressure from the gallery oil passages  20  is provided to the annular feed grooves  22  for actuating the hydraulic lash adjusters in the lifters  50 . Simultaneously, a restricted amount of oil flow passes through the bypass grooves  48  of each of the deactivating or switching lifters  50 , providing a restricted flow of oil from the pin feed openings  54  through the control passages  26  and control channel  28  back to the control valve  30  which is in the exhaust position. Thus, aerated or vapor-entrained oil in the control passages  26  and channel  28  is purged by the bypass oil flow from the system through the control valve exhaust port  36 . Thereafter, the system operates normally. In a supply mode, the control valve  30  supplies pressure oil to the control channel and deactivating pins  24  when it is desired to deactivate the selected engine cylinders. In an exhaust mode, valve  30  exhausts oil pressure from the control channel and passages so that the locking pins are released and again allow normal valve actuation for all the cylinders. 
     Referring now to FIG. 4 of the drawings, numeral  56  generally indicates a cylinder deactivation apparatus which is generally similar to FIG.  2  and wherein like numerals indicate like parts. Apparatus  56  differs in that the deactivating devices are stationary hydraulic lash adjusters  58  which are fixedly mounted in a lash adjuster gallery  60 . The remainder of the apparatus  56  is identical to and operates in the same manner as the apparatus  46  of FIG. 2 so that like numerals are used for like parts. FIG. 5 shows an enlarged pictorial view of a stationary lash adjuster  58 , showing the connection of an annular feed groove  22  with the pin feed opening  54  through restricted bypass groove  48  as in the hydraulic valve lifter body of FIG.  3 . 
     Since the embodiment of FIGS. 4 and 5 operates in a manner identical to that of FIGS. 2 and 3, except for the use of stationary hydraulic lash adjusters, further description of the embodiment of FIGS. 4 and 5 is believed unnecessary. 
     FIG. 6 of the drawings shows an alternative cylinder deactivation apparatus  62  that is a variation of the embodiment of FIG.  1  and in which like numerals indicate like parts. Apparatus  62  includes modified switching valve lifters  64 . Each lifter  64  includes a lifter body  66  having a vertical channel  68  extending from the lifter oil gallery  20  to an annular channel  70  circumscribing a lower portion of the body  66 . Pressurized oil in the annular channel  70  acts as a fluid seal against the wall of the lifter gallery bore  14  to prevent the entry of air bubbles from below the lifter gallery  12  entering the bore  14  and passing into the control channel  26 . The seal prevents aeration of the control channel oil, which can interfere with the timing of the deactivation process during engine operation. 
     FIGS. 7 and 8 illustrate a cylinder deactivation apparatus  72  that is a variation of the embodiment of FIG. 2 wherein like numerals indicate like parts. This variation also includes modified switching valve lifters  74 . Each lifter  74  includes a lifter body  76  having a vertical channel  78  extending from the lifter oil gallery  20  to an annular channel  80  circumscribing a portion of the body  76  slightly below the pin feed openings  54 . Pressurized oil in; the annular channel  80  again acts as a fluid seal against the wall of the,lifter gallery bore  14  to prevent the entry of air bubbles from below the lifter gallery  12  entering the bore  14  and passing into the control channel  26 . The seal prevents aeration of the control channel oil, which can interfere with the timing of the deactivation process during engine operation. 
     The upward relocation of the annular channel  80  allows the channel  80  to supplement the function of purging air from the control channels during engine operation. FIG. 7 shows the operating condition when the lifter actuating cam  82  is on the base circle and the associated valve is closed. The annular channel  80  is then located below the control passage  26  so that channel  80  acts as a seal, preventing air entry from below into the control channel  26 . FIG. 8 shows the condition when the cam  82  raises the lifter  74  to its maximum lift. Annular channel  80  is then aligned with the control passage  26  to provide oil flow from the oil gallery  12  through the vertical channel  78  and annular channel  80  to the control passage  26 . The oil flow purges the control channel  26  from aerated oil which is carried out through the control valve exhaust  36  and returned to the engine oil pan, not shown. When the cam again returns to the base circle, the annular channel continues to form a fluid seal, preventing the admission of air to the oil from below. 
     While the invention has been described by reference to certain preferred embodiments, it should be understood that numerous changes could be made within the spirit and scope of the inventive concepts described. Accordingly, it is intended that the invention not be limited to the disclosed embodiments, but that it have the full scope permitted by the language of the following claims.