EP1143120A2

EP1143120A2 - Valve deactivator assembly for internal combustion engine

Info

Publication number: EP1143120A2
Application number: EP01302059A
Authority: EP
Inventors: Keith Hampton; Richard Lee Madden
Original assignee: Eaton Corp
Current assignee: Eaton Corp
Priority date: 2000-03-08
Filing date: 2001-03-06
Publication date: 2001-10-10
Also published as: KR20010089206A; JP2001271620A; EP1143120A3

Abstract

A valve deactivator assembly (43) including a rocker arm (33) having a pivot location (39) about which the rocker arm (33) normally pivots in response to rotation of the cam shaft (25). The valve deactivator assembly includes an HLA (hydraulic lash adjuster) (41) which serves as the pivot point for the rocker arm. The HLA includes a body (49) and a plunger assembly (53), including a plunger portion (67) having an engagement portion (69) surrounding the plunger portion (67) and in engagement with the pivot portion (39) of the rocker arm. A latch mechanism (79-91) is operable to either latch the engagement portion (69) to the plunger portion, for operation in a normal mode, or unlatch the engagement portion, for operation in a deactivated mode. Thus, the latch mechanism of the present invention does not add to the overall size of the main part of the HLA, or of the bore (45) in the cylinder head (11) in which the HLA is located.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

Not applicable

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable

MICROFICHE APPENDIX

Not applicable

BACKGROUND OF THE DISCLOSURE

The present invention relates to an improved valve train for an internal combustion engine, and more particularly, to a valve deactivator assembly for use therein.
Although the valve deactivator assembly of the present invention may be utilized to introduce some additional lash into the valve train, such that the valves open and close by an amount less than the normal opening and closing, the invention is especially suited for introducing into the valve train sufficient lash (also referred to hereinafter as "lost motion"), such that the valves no longer open and close at all (i.e., the valves are "deactivated"), and the invention will be described in connection therewith.
Valve deactivators of the general type to which the invention relates are known in connection with various types of internal combustion engine valve gear train, including overhead valve ("OHV") gear train of the pushrod type. Valve deactivators are also known in connection with overhead cam ("OHC") type valve gear train of both the center pivot rocker arm type and the end pivot rocker arm type. Although the particular structure of the present invention is not necessarily limited to use in the OHC, end pivot rocker arm type of valve gear train, it is especially suited for use therewith, and will be described in connection with that type of valve gear train.
In a typical valve gear train of the end pivot rocker arm type, the rocker arm pivots about a pivot location defined by the rocker arm. The pivot location engages the ball plunger of an HLA (hydraulic lash adjuster), the HLA being disposed in a bore in the cylinder head. It is known in the prior art to provide the HLA with some sort of valve deactivation capability, in those applications in which there is enough room in the cylinder head to replace the conventional HLA with a deactivation device, which typically takes up substantially more space than a conventional HLA.
Unfortunately, in many vehicle applications in which it would be desirable to have valve deactivation capability, there is barely enough room for even a conventional HLA, let alone one which is larger by virtue of added structure. The added structure referred to herein is typically some sort of latching and lost motion mechanism, by means of which, for example, the plunger assembly of the HLA either may be latched to the body for normal operation, or may be unlatched, and engage in lost motion, for operation in a valve deactivation mode. Such added structure would obviously add substantially to the overall size and complexity and cost of the conventional HLA.
For example, in the latching type of valve deactivator shown in U.S. Patent No. 5,655,487, the latching mechanism involves latch members which move radially under the influence of either a spring or hydraulic pressure to latch or unlatch the body and the plunger assembly. It is apparent that in such a valve deactivator, the overall diameter of the device will be substantially greater than that of a conventional HLA, which needs only the conventional wall thickness for the body and the plunger. In addition, the presence of a plunger which must be able to move between a latched position and an unlatched position, relative to the body, increases the overall length required for the bore in the cylinder head which contains the HLA body.

BRIEF SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide a valve deactivator assembly which is especially suited for use in an end pivot rocker arm type of valve gear train, wherein the addition of valve deactivation capability does not substantially increase the overall size of the hydraulic lash adjuster.
It is a more specific object of the present invention to provide such an improved valve deactivator assembly which accomplishes the above-stated object, and more specifically, which does not require a larger bore in the cylinder head than is already required to accommodate a conventional hydraulic lash adjuster.
The above and other objects of the invention are accomplished by the provision of a valve deactivator assembly for an internal combustion engine having valve means for controlling the flow to and from a combustion chamber, drive means for providing cyclical motion for opening and closing the valve means in timed relationship to the events in the combustion chamber, and valve gear means operative in response to the cyclical motion to effect cyclical opening and closing of the valve means. The valve gear means includes a rocker arm having a valve contact portion in engagement with the valve means, and a pivot location about which the rocker arm normally pivots in response to the cyclical motion of the drive means. The valve deactivator assembly includes a hydraulic lash adjuster adapted to be disposed in a bore in a cylinder head and serving as the pivot point for the pivot location of the rocker arm.
The hydraulic lash adjuster is characterized by a body member being disposed in the bore, and a plunger assembly operably associated with the body member and reciprocable relative thereto. The plunger assembly includes a plunger portion and an engagement portion surrounding the plunger portion and being in engagement with the pivot location of the rocker arm. A latch mechanism is operable to latch the engagement portion relative to the plunger portion, in an extended position, during operation in a normal mode, and being operable to unlatch the engagement portion relative to the plunger portion during operation in a deactivated mode. The lash adjuster includes means biasing the engagement portion toward the extended position.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a somewhat schematic, fragmentary, cross-section taken through a vehicle internal combustion engine, illustrating a typical valve gear train of the type with which the present invention may be utilized.
FIG. 2 is a greatly enlarged, fragmentary, cross-section, taken on line 2-2 of FIG. 1, illustrating the valve deactivator assembly of the present invention in its normal, latched condition.
FIG. 3 is a fragmentary, perspective view, similar to FIG. 1, illustrating the valve gear train with the valve deactivator assembly of the present invention in its unlatched condition.
FIG. 4 is a further enlarged, fragmentary cross-section, similar to FIG. 2, illustrating in greater detail the valve deactivator of the present invention in the latched condition.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to the drawings, which are not intended to limit the invention, FIG. 1 illustrates a valve actuating drive train of the end pivot rocker arm type, which is especially suited use of the present invention. FIG. 1 illustrates a cylinder head 11 defining a flow passage 13, by means of which there may be a flow to or from a combustion chamber, generally designated 15.
The flow to or from the combustion chamber 15 is controlled by means of an engine poppet valve 17 which is biased, by means of a valve spring 19 from the open position shown in FIG. 1 toward a closed position. The poppet valve 17 includes a valve seat 21 which, when the poppet valve 17 is closed, is in engagement with a valve seat insert, not shown herein, but well known to those skilled in the art.
A cam shaft 25 includes a cam profile, generally designated 27 which defines a base circle portion 29 and a lift portion 31. As is well known to those skilled in the art, the function of the cam shaft 25 is to provide cyclical motion for opening and closing the engine poppet valve 17 in timed relationship to the events in the combustion chamber 15.
The cyclical motion of the cam shaft 25 is transmitted to the engine poppet valve 17 by means of a rocker arm 33, illustrated herein as being of the end pivot type. It may be seen by comparing FIGS. 1 and 3 that in FIG. 1, the view of the rocker arm 33 is an axial cross section taken through the rocker arm 33. The rocker arm 33 includes a valve contact portion ("pad") 35 which is in engagement with the upper end of the stem of the poppet valve 17. The rocker arm 33 also includes a rotatable cam follower 37, mounted on a shaft 38, such that the cam follower 37 remains in engagement with the cam profile 27. Finally, the rocker arm 33 includes a pivot portion, generally designated 39, which defines a pivot location (also to be referred to hereinafter by "39"), i.e., a location about which the rocker arm 33 normally pivots as the cam follower 37 engages, alternately, the base circle portion 29 and then the lift portion 31. In the subject embodiment, and by way of example only, the pivot portion 39 comprises the rocker arm 33 having a pair of side walls 40, each of which defines a generally half-circular support surface 40s, shown best in FIG. 2. In engagement with the support surfaces 40s of the pivot portion 39 is an HLA (hydraulic lash adjuster) generally designated 41 in FIGS. 1, 2, and 3.
Referring now primarily to FIG. 2, it will be understood that the rocker arm 33 and the hydraulic lash adjuster 41 together comprise a valve deactivator assembly, generally designated 43. The cylinder head 11 defines a bore 45 extending to an upward surface of the cylinder head 11. The head 11 also defines an oil passage 47, which is typically in communication with the engine lubrication oil circuit. As will be understood by those skilled in the art, the oil passage 47 comprises one "source of pressurized fluid" which is required to operate the HLA 41, in the conventional manner, well known to those skilled in the art of hydraulic lash adjustment.
The hydraulic lash adjuster 41 includes a generally cylindrical body 49 disposed within the bore 45, the body 49 defining an internal blind bore 51. A plunger assembly, generally designated 53, is slidably disposed within the blind bore 51, and includes an upper plunger element 55, a lower plunger element 57, and a leakdown plunger 58. The plunger elements 55, 57 and 58 cooperate to define a low pressure chamber 59 (also referred to hereinafter as a "reservoir"). The blind bore 51 and the leakdown plunger element 58 cooperate to define a high pressure chamber, which for simplicity will also bear the reference numeral "51", and which is shown in approximately its minimum volume condition in FIG. 2.
A check valve assembly, generally designated 61, is operable to permit fluid communication between the reservoir 59 and the high pressure chamber 51, in a manner generally well known to those skilled in the art. Although the present invention is illustrated in conjunction with an HLA of the "conventional leakdown" type, it should be understood that the present invention is not necessarily so limited, and could also be used in conjunction with various other types of HLA. Although the present invention is illustrated in connection with an HLA of the type having the moveable plunger assembly disposed within a stationary body member, it should be understood that the present invention is not so limited. By way of example only, it would be possible within the scope of the invention for the moveable plunger assembly to surround the stationary body member. All that is essential to the present invention is that there be a body member and that there be a plunger assembly which is moveable (reciprocable) relative to the body member.
Referring still primarily to FIG. 2, the body 49 defines a fluid port 63, which is in open fluid communication with the oil passage 47. The upper plunger element 55 defines a radial bore 65, in open communication with the port 63, thus permitting pressurized fluid to flow from the passage 47 through the port 63 and bore 65. The lower plunger element 57 defines an axially extending passage 66p, the upper end of which communicates with a port 66 near the upper end of the lower plunger member 57, such that low pressure fluid in the oil passage 47 flows through the passage 66p, then through the port 66 and into the low pressure chamber 59.
Disposed to the left in FIG. 2 of the HLA 41, the cylinder head 11 defines an oil passage 11c, which is in fluid communication with an engine oil circuit which is separate from the circuit connected to the oil passage 47. The oil passage 11c comprises the "source of pressurized fluid" which is required to control (operate) the valve deactivator assembly 43 of the present invention. Therefore, it must be possible to control the oil pressure in the passage 11c, selectively providing either a relatively low pressure or a relatively high pressure, as is well known to those skilled in the art of engine hydraulics. By way of example only, the pressure in the passage 11c may be controlled by means of a solenoid valve (not shown herein). The body 49 defines an opening in which is disposed a generally cylindrical member 49m, which could comprise a roll pin or similar structure. The member 49m extends far enough radially inward into an opening 55o defined by the upper plunger element 55, such that the element 55 is substantially prevented from rotating, relative to the body 49. The lower plunger element 57 defines another axially extending passage 57p, by means of which the control pressure in the passage 11c can flow through the interior of the member 49m, then through the opening 55o, then through the passage 57p, for reasons which will be explained subsequently.
On a conventional HLA, the upper plunger element 55 would include a ball plunger portion which would engage an adjacent surface of the rocker arm. In accordance with one important aspect of the present invention, the upper plunger element 55 includes a separate plunger portion 67 (which is merely the upper end of the element 55) and engagement portion, generally designated 69, the engagement portion 69 surrounding the cylindrical plunger portion 67, and being disposed for movement (in a vertical direction in FIG. 2) relative to the plunger portion 67. A compression (lost motion) spring 71 surrounds the lower part of the plunger portion 67, and is operable to bias the engagement portion 69 upward, toward a fully extended position as shown in FIG. 2.
In the above-described fully extended position shown in FIGS. 2 and 4, the engagement portion 69 is biased into engagement with a snap ring (retaining clip) 72, which limits upward travel of the engagement portion 69. The engagement portion 69 is in engagement with the pivot portion 39, and doesn't permit any vertical movement of the pivot portion 39 when the valve deactivator assembly is in the activated (latched) mode (see FIG. 2), as will be described in greater detail subsequently. When the sliding engagement portion 69 is in engagement with the snap ring 72, part of the force exerted by the lost motion spring 71 is transmitted directly to the snap ring 72, i.e., not all of the force of the spring 71 is exerted on the rocker arm 33. Instead, the force transmitted to the rocker arm 33 is equal to approximately the force exerted on the upper plunger member 55 by the pressure in the high pressure chamber 51.
Referring now primarily to FIG. 4, the upper plunger element 55 defines an axially extending passage 75 which terminates at, but is in open communication with one or more radially extending bores 79. Surrounding the plunger portion 67 is a generally block-shaped portion (seen best in FIG. 3) of the engagement portion 69, and extending oppositely from the block-shaped portion is a pair of generally cylindrical latch housing portions 81. Together, the latch housing portions 81 comprise a fulcrum for the surfaces 40s of the rocker arm 33, as is best seen in FIG. 2. Each latch housing portion 81 defines a radially extending bore 83, which are aligned with the bores 79 when the engagement portion 69 is in the extended position shown in FIGS. 2 and 4. Each bore 83 is sealed at its radially outer end by a plug 85. Disposed in each bore 83 for reciprocal movement therein is a latch pin 87, biased toward the latched position shown in FIG. 4 by means of a compression (latching) spring 89, the radially outer ends of the springs 89 being seated against the respective plug 85.
Disposed within the bores 79 is a pair of pistons 91 which, in the latched condition shown in FIG. 4, may be biased radially inward into engagement with each other, by the latch pins 87 under the influence of the latching springs 89. In this latched condition, the latch pins are biased radially inward into the bores 79, as shown in FIG. 4, thus latching the engagement portion 69 to the plunger portion 67. In order to achieve this latched condition, relatively low pressure fluid is communicated from the control pressure source 11c to the passage 75, and the springs 89 have been selected such that the springs 89 are able to overcome the force of the low pressure fluid acting on the radially inner surfaces of the pistons 91. Thus, the springs 89 bias the latch pins 87 and the pistons 91 to the latched position shown. In the latched condition, the fulcrum defined by the latch housing portions 81 remains in the position shown in FIGS. 1, 2 and 4, such that the pivot portion 39 of the rocker arm 33 pivots, but does not move vertically. The rocker arm 33 operates in its normal manner, moving the engine poppet valve 17 between its open and closed positions in response to the cyclical motion of the cam shaft 25, as is well known to those skilled in the art.
When it is desired to operate in the valve deactivated mode, it is first necessary to increase the fluid pressure at the control pressure source 11c to a relatively higher pressure, the pressure being sufficient to bias the pistons 91 radially outward, in opposition to the force of the latching springs 89. The pistons 91 are biased outwardly far enough to disengage the latch pins 87 from the bores 79, thus unlatching the engagement portion 69 from the plunger portion 67. In other words, the engagement portion 69 is no longer fixed relative to the plunger portion 67, but is now free to move vertically downward, away from the snap ring 72, in opposition to the force of the lost motion spring 71. As will be understood by those skilled in the art, when the cam follower 37 is in engagement with the base circle portion 29 of the cam shaft 25, there is not sufficient force acting on the engagement portion 69 to overcome the lost motion spring 71. However, the valve spring 19 is substantially stronger than the lost motion spring 71, and therefore, when the lift portion 31 of the cam profile engages the cam follower 37, there will be a downward force on the rocker arm 33 which will overcome the lost motion spring 71, and move the pivot portion 39 downward as shown in FIG. 3. In this valve deactivated condition just described, the rocker arm 33 now pivots about the pad portion 35, but with no movement of the poppet valve 17 occurring, because of the force of the valve spring 19.
Thus, it may be seen that the present invention provides a valve deactivator assembly which permits the use of a hydraulic lash adjuster which is of conventional size, as far as the required size of the bore 45 in the cylinder head 11. Unlike the known prior art, all of the mechanism needed to achieve the valve deactivation is disposed external to the main part of the HLA, being associated only with the plunger portion 67, in an area where more space is typically available.
The invention has been described in great detail in the foregoing specification, and it is believed that various alterations and modifications of the invention will become apparent to those skilled in the art from a reading and understanding of the specification. It is intended that all such alterations and modifications are included in the invention, insofar as they come within the scope of the appended claims.

Claims

A valve deactivator assembly (43) for an internal combustion engine having valve means (17) for controlling the flow to and from a combustion chamber (15), drive means (25) for providing cyclical motion for opening and closing said valve means (17) in timed relationship to the events in said combustion chamber (15), and valve gear means operative in response to said cyclical motion to effect cyclical opening and closing of said valve means (17); said valve gear means including a rocker arm (33) having a valve contact portion (35) in engagement with said valve means (17), and a pivot location (39) about which said rocker arm (33) normally pivots in response to said cyclical motion of said drive means (25); said valve deactivator assembly (43) including a hydraulic lash adjuster (41) adapted to be disposed in a bore (45) in a cylinder head (11), and serving as the pivot point for said pivot location (39) of said rocker arm (33); said hydraulic lash adjuster (41) being characterized by:

(a) a body member (49) disposed in said bore (45);

(b) a plunger assembly (53) operably associated with said body member (49) and reciprocable relative thereto;

(c) said plunger assembly (53) including a plunger portion (67) and an engagement portion (69) surrounding said plunger portion (67), and in engagement with said pivot location (39) of said rocker arm (33);

(d) a latch mechanism (79-91) operable to latch said engagement portion (69) relative to said plunger portion, in an extended position (FIG. 2), during operation in a normal mode (FIG. 1), and operable to unlatch said engagement portion (69) relative to said plunger portion (67), during operation in a deactivated mode (FIG. 3); and

(e) means (71) biasing said engagement portion (69) toward said extended position (FIG. 2).
A valve deactivator assembly (43) as claimed in claim 1, characterized by said drive means comprising a camshaft (25) defining a cam profile including a base circle portion (29) and a lift portion (31), and said rocker arm (33) includes a cam follower (37).
A valve deactivator assembly (43) as claimed in claim 1, characterized by said pivot location (39) of said rocker arm (33) comprising a pair of side walls (40) being in engagement with said engagement portion (69) and being disposed adjacent an upper end of said plunger portion (67) when said latch mechanism is in said normal, latched condition (FIG. 1), said upper end of said plunger portion (67) extending between said side walls (40) when said latch mechanism (79-91) is in said unlatched condition (FIG. 3) during operation in a deactivated mode, as said drive means (25) exerts a force on said rocker arm (33) in opposition to the force of said means (71) biasing said engagement portion (69) toward said extended position (FIG. 2).
A valve deactivator assembly (43) as claimed in claim 1, characterized by said cylinder head (11) defining a source (11c) of pressurized control fluid operably associated with said latch mechanism (79-91) and operable to bias said latch mechanism toward said unlatched condition (FIG. 3), said latch mechanism including spring means (89) operable to bias said latch mechanism toward said latched condition (FIG. 4).
A valve deactivator assembly (43) as claimed in claim 4, characterized by said plunger assembly (53) defining a fluid passage (57p) in open communication with said source (11c) of pressurized control fluid, and said plunger portion (67) defining a fluid passage (75) providing open fluid communication from said fluid passage (57p) to said latch mechanism (79-91).
A valve deactivator assembly (43) as claimed in claim 5, characterized by said engagement portion (69) and said plunger portion (67) cooperating to define aligned bores (79,83) when said engagement portion (69) is in said extended position (FIG. 2), said latch mechanism including a pair of diametrically opposite latch pins (87) biased radially inward, into latching engagement (FIG. 4) with said plunger portion (67) when said source (11c) of pressurized control fluid contains fluid at relatively low pressure.
A valve deactivator assembly (43) as claimed in claim 6, characterized by said plunger portion (67) defining a generally diametrically oriented bore (79), a pair of pistons (91) disposed in said diametrically oriented bore, and being operable in response to relatively high pressure fluid in said source (11c) of pressurized control fluid, to be biased radially outward, moving said latch pins (87) radially outward, out of latching engagement with said plunger portion (67).