System for engine valve actuation comprising lash-prevention valve actuation motion

Abstract

A system for actuating engine valve comprises a main valve actuation motion source configured to supply main valve actuation motions to the at least one engine valve via a main motion load path, and an auxiliary valve actuation motion source separate from the main valve actuation motion source and configured to supply complementary auxiliary valve actuation motions to the at least one engine valve via an auxiliary motion load path. A lost motion component is configured, in one state, to maintain lash between the auxiliary valve actuation motion source and the auxiliary motion load path or within the auxiliary motion load path and, in another state, to take up this lash. The auxiliary valve actuation motion source is further configured to supply at least one lash-prevention valve actuation motion that substantially matches at least one of the main valve actuation motions.

Claims

1. A system for use in an internal combustion engine having at least one engine valve associated with a cylinder, the system comprising: a main valve actuation motion source configured to supply main valve actuation motions to the at least one engine valve via a main motion load path; an auxiliary valve actuation motion source separate from the main valve actuation motion source and configured to supply auxiliary valve actuation motions to the at least one engine valve via an auxiliary motion load path, wherein the auxiliary valve actuation motions are complementary to the main valve actuation motions; and a lost motion component configured, in, one state, to maintain lash between the auxiliary valve actuation motion source and the auxiliary motion load path or within the auxiliary motion load path and, in another state, to take up the lash between the auxiliary valve actuation motion source and the auxiliary motion load path or within the auxiliary motion load path, the auxiliary valve actuation motion source further comprising a lash-prevention valve actuation motion component for providing at least one lash-prevention valve actuation motion that substantially matches a primary valve lift of the main valve actuation motions.

2. The system of claim 1, wherein the auxiliary valve actuation motion source is a cam, and the at least one lush-prevention valve actuation motion component is implemented as an additional lobe on the cam.

3. The system of claim 1, wherein the lost motion component comprises a hydraulically controlled piston.

4. The system of claim 1, wherein the auxiliary motion load path includes the main motion load path.

5. The system of claim 1, wherein the main motion load path comprises an automatic lash adjuster.

6. The system of claim 1, wherein the auxiliary motion load path comprises an automatic lash adjuster.

7. The system of claim 1, wherein the at least one engine valve comprises at least one exhaust valve.

8. The system of claim 1, wherein the at least one engine valve comprises at least one intake valve.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The features described in this disclosure are set forth with particularity in the appended claims. These features and attendant advantages will become apparent from consideration of the following detailed description, taken in conjunction with the accompanying drawings. One or more embodiments are now described, by way of example only, with reference to the accompanying drawings wherein like reference numerals represent like elements and in which:

(2) FIGS. 1, 6 and 8 are schematic block diagrams of a system for actuating engine valves in accordance with prior art techniques;

(3) FIGS. 2, 7 and 9 show both main and auxiliary valve lift curves in accordance with prior art techniques;

(4) FIGS. 3-5 are schematic, cross-sectional illustrations of a lost motion component in accordance with prior art techniques;

(5) FIGS. 10 and 11 show both main and auxiliary valve lift curves in accordance with the instant disclosure;

(6) FIG. 12 illustrates an auxiliary valve actuation motion source in the form of a cam that may be used to implement a lash-prevention valve actuation motion in accordance with the instant disclosure; and

(7) FIG. 13 is a schematic block diagram of a system for actuating engine valves in accordance with the instant disclosure.

DETAILED DESCRIPTION OF THE PRESENT EMBODIMENTS

(8) Referring now to FIGS. 10 and 11, examples of a main valve lift curve 1002 and an auxiliary valve lift curve 1008 for an exhaust valve that may be caused by respective ones of the main and auxiliary valve actuation motion sources 102, 1202. In the illustrated examples, the main lift curve 1002 comprises a base circle portion 1004 in which no lift is provided, as well as a main lift event 1006, whereas the auxiliary lift curve 1008 comprises a base circle portion 1010, a BGR lift event 1012, a compression-release lift event 1014 and a lash-prevention valve actuation motion 1016. As in the case of FIGS. 2 and 7, with the exception of the lash-prevention valve actuation motion 1016, the non-zero lifts in each curve 1002, 1008 are complementary to each other in that they do not overlap and yet provide the complete set of motions to be applied to the valve. As in the case with FIG. 2, the curves 1002, 1008 illustrated in FIG. 10 assume that the lost motion component 118 (not shown in FIG. 13) is currently in a state where the auxiliary valve lifts 1008 are lost, as illustrated by the lash 1020 such that that the auxiliary lift events 1012, 1014 are below the base circle portion 1004 of the main valve lift curve 1002.

(9) As noted, however, the lash-prevention valve actuation motion 1016 is not complementary to the lifts illustrated in the main valve lift curve 1002. In fact, the lash-prevention valve actuation motion 1016 substantially matches the main lift event 1006, as best illustrated in FIG. 11 (corresponding to that state in which the lost motion component 118 takes up the lash 1020 between the curves 1002, 1008). An example of an auxiliary valve actuation motion source 1202 that may be used to implement the auxiliary valve lifts 1008 is illustrated in FIG. 12. In particular, the auxiliary valve actuation motion source 1202 is implemented in FIG. 12 as a cam having a base circle portion 1210 (corresponding to the zero lift portion 1010 of FIG. 10), a BGR cam lobe 1212 (corresponding to the BGR lift event 1012 of FIG. 10), a compression-release cam lobe 1214 (corresponding to the compression-release lift event 1014 of FIG. 10) and a lash-prevention cam lobe 1216 (corresponding to the lash-prevention valve actuation motion 1016 of FIG. 10). As will be appreciated by those having skill in the art, the cam lobes 1212, 1214, 1216 illustrated in FIG. 12 do not necessarily match the exact profile of the valve lifts 1012, 1014, 1016 illustrated in FIG. 10.

(10) As best shown in FIG. 11, the substantially matching characteristics (e.g., maxim valve lift, duration, shapes, etc.) of the lash-prevention valve actuation motion 1016 and, in the illustrated example, the main lift event 1006 results in the establishment of substantially no or little lash space between the auxiliary motion load path 114 and the bridge pin 116 during application of the main lift event 1006 to the valve bridge 110 (at and around time t.sub.2 shown in FIG. 11). This is illustrated in FIG. 13, in contrast with FIG. 8, in which the auxiliary motion load path 114 remains in contact with the bridge pin 116 thereby eliminating the additional lash 802 shown in FIG. 8, and thereby further avoiding any extension of the lost motion component 118 (or automatic lash adjuster 124, if provided) in an effort to take up such additional lash space 802.

(11) Consequently, provision of the lash-prevention valve actuation motion 1016 eliminates the need for complex and costly configurations of the lost motion component 118 found in prior art solutions. Additionally, by substantially eliminating one of the complications arising from use of an automatic lash adjuster 124 in the auxiliary motion load path 114, both the main and auxiliary motion load paths 108, 114 may operate in a lashless manner, thereby eliminating the time- and labor-intensive need to set lash in these load paths 108, 114 experienced with prior art solutions.

(12) It should be noted that, while examples have been described in the instant disclosure in terms of exhaust valves, it is understood that the techniques described herein may be equally applied to intake valves.

(13) While particular preferred embodiments have been shown and described, those skilled in the art will appreciate that changes and modifications may be made without departing from the instant teachings. It is therefore contemplated that any and all modifications, variations or equivalents of the above-described teachings fall within the scope of the basic underlying principles disclosed above and claimed herein.