The present invention relates to hydraulic lash adjusters (HLAs) in internal combustion engines; more particularly, to such HLAs having means for selectively engaging and disengaging activation of valves in valvetrains; and most particularly, to an improved valve deactivating HLA for oriented, non-rotatable mounting in an engine such that the axis of the lock pins can be made substantially parallel to the axis of the camshaft.
It is well known that overall fuel efficiency in a multiple-cylinder internal combustion engine can be increased by selective deactivation of one or more of the engine valves under certain engine load conditions.
For an overhead-cam engine, a known approach is to equip the hydraulic lash adjusters for those valvetrains with means whereby the roller finger followers (RFFs) may be rendered incapable of transferring the cyclic motion of engine cams into reciprocal motion of the associated valves. Such lash adjusters are known in the art as Deactivating Hydraulic Lash Adjusters (DHLAs).
A prior art DHLA includes a conventional hydraulic lash elimination means disposed in a plunger having a domed head for engaging the RFF. The plunger itself is slidably disposed in a pin housing containing the lock pins which in turn is slidably disposed in a DHLA body. The pin housing may be selectively latched and unlatched hydromechanically to the body by the selective engagement of a spring and pressurized engine oil on lock pins.
During engine operation in valve deactivation mode, the lock pins are withdrawn from lock ledges in the body, which may be an annular groove, and the pin housing is reciprocally driven in oscillation by the socket end of the RFF which pivots on its opposite pad end on the immobile valve stem as the cam lobe actuates the RFF. The pin housing is returned during half the lost motion reciprocal cycle by one or more lost motion springs disposed within the body.
In a prior art DHLA, the angular orientation of the DHLA body is not specified with respect to the cylinder head. As a result, the axis of the lock pins is free to assume any random orientation, even for the case when the orientation of the pin housing is fixed relative to the body. This variability in orientation can result in the problem of unequal load sharing for locking mechanisms utilizing two pins, the solution to which is the subject of the present invention.
During valve actuation, the displacement of the RFF by the cam lobe creates cyclically-imposed force vectors on the head of the DHLA plunger. Specifically, as the RFF roller climbs the opening flank of the cam eccentric, the RFF body is urged in a first direction transverse to the axis of the camshaft; and as the RFF roller descends the closing flank of the cam eccentric, the RFF body is urged in a second and opposite direction. Since the orientation of the lock pin axis is not explicitly specified, there are times when the pin axis will assume an orientation co-planar with the cyclic side loads described above. In this situation (wherein the pin axis is perpendicular to the axis of the camshaft), when the side loads reach a sufficient magnitude relative to the axial load, the entire load is entirely supported by only one of the lock pins. When the side load subsequently changes direction, the aforesaid pin is completely unloaded and the other pin assumes the full axial load. Instead of both pins equally sharing the axial load as desired, the lock pins cyclically alternate between supporting the entire load individually and being totally unloaded.
This problem can be relieved by orienting the lock pin axis to be substantially parallel to the axis of the camshaft, thus enabling both lock pins to share the torque load equally. Such orientation can also be used to locate vulnerable points, known in the art as “stress risers”, in the DHLA body and pin housing in positions of low tensile stress.
What is needed in the art is an improved arrangement for fixing the orientation of a DHLA body within a bore in an engine head such that the axis of the lock pins in the pin housing is always parallel to the axis of the engine camshaft.
It is a principal object of the present invention to reduce wear in, and extend the operating life of, a deactivating hydraulic lash adjuster in an internal combustion engine.
Briefly described, an improved deactivating hydraulic lash adjuster in accordance with the present invention comprises a pin housing slidably disposed in a lash adjuster body as in the prior art, and having opposed, spring-loaded pins disposed in a transverse bore in the pin housing for extending into receiver features in the body to lock the two together during periods of engine operation in valve non-deactivation mode.
The present improvement consists in providing a first orienting feature for the DHLA body that engages a second orienting feature on an engine head to provide a preferred orientation of the body within a bore in the engine head. In a currently preferred orientation, the axis of the lock pins is substantially parallel to the axis of the engine camshaft.
This improvement necessitates that the orientation of the pin housing with respect to the body must also be invariant. One known means for achieving this restraint is insertion of a pin or ball through a radial bore in the body into a longitudinal groove in the pin housing.
The present invention will now be described, by way of example, with reference to the accompanying drawings, in which:
Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate currently preferred embodiments of the invention, and such exemplifications are not to be construed as limiting the scope of the invention in any manner.
Referring to
Orientation of pin housing 12 about the axis 11 of DHLA 10 with respect to body 14 must be invariant in order to ensure the lock pin axis is maintained in the desired relationship. A known means for prohibiting rotation of the pin housing within the body is insertion of a stop means such as a pin or ball 36 through a radial bore 38 in body 14 into a longitudinal groove 40 in pin housing 12.
Referring to
The unequal load sharing described above arises when vectors 56,58 and 62,64 as well as axis 17 are contained in a common plane and is undesirable for causing increased stress and wear on lock pins and their mating features on the body 10. Note further than if axis 17 can be made parallel to camshaft axis 66 by rotation of DHLA 10 90° about its own axis 11, then vectors 56, 58 and 62, 64 are not contained in a common plane with axis 17 and therefore the axial load is shared approximately equally by the lock pins.
Fixing the orientation of the body and the pin housing also enables reduced tensile forces vulnerable areas known as stress risers, shown in
As noted above, the object of the present invention is to fix the orientation of a DHLA with respect to a bore in an engine head. This may be accomplished by equipping the DHLA with a first feature extending from the DHLA body that engages a second feature on the engine head. The second feature may be a new feature formed in the head specifically to interact with the DHLA feature; or the second feature may be an otherwise occurring feature, for example, a camshaft bearing tower. The latter case is generally preferred since no modification of prior art head design and manufacture is required. The following is a description of examples of both types of non-rotation features in accordance with the present invention.
Referring to
Body 14 includes an annular lash ring groove 28, as shown in
Referring now to
Since pin housing 12 is constrained from rotation within body 14 (
Clip 122 may take any of several forms within the scope of the invention. For example, a spring clip 122′ as shown in
While the DHLA, in accordance with the invention, has been described as a switchable support member used in conjunction with an engine having an overhead-camshaft valvetrain, it is understood that the invention is also applicable to other types of switchable members in a valvetrain having one or more hydromechanically locking pins such as a deactivating valve lifter used in a pushrod engine.
While the invention has been described by reference to various specific embodiments, it should be understood that numerous changes may be made within the spirit and scope of the inventive concepts described. Accordingly, it is intended that the invention not be limited to the described embodiments, but will have full scope defined by the language of the following claims.
This application claims the benefit of U.S. Provisional Application No. 61/065,343, filed Feb. 11, 2008.
Number | Name | Date | Kind |
---|---|---|---|
7086360 | Schnell et al. | Aug 2006 | B1 |
20090007871 | Bugescu | Jan 2009 | A1 |
Number | Date | Country | |
---|---|---|---|
20090199805 A1 | Aug 2009 | US |
Number | Date | Country | |
---|---|---|---|
61065343 | Feb 2008 | US |