The present invention relates to a valve train assembly having a rocker arm for control of valve actuation.
Dual lift rocker arms for control of valve actuation by alternating between at least two or more modes of operation are known. Such rocker arms typically involve multiple bodies, such as an inner arm and an outer arm, that are latched together to provide one mode of operation and are unlatched, and hence can pivot with respect to each other, to provide a second mode of operation. The so called Type II valve train (i.e. end pivot rocker arm, overhead cam) is the most commonly used valve train in both modern petrol and diesel internal combustion engines. Dual lift rocker arms for this type of valve train often use a three lobe camshaft wherein a first and a second of the lobes control one type of valve lift and the third of the lobes control another type of valve lift. Typically in such arrangements, the outer arm of the dual lift rocker arm is provide with a pair of arcuate metal pads each for making a sliding contact with a respective one of the first and second of the lobes, and the inner arm is provided with a roller for making a rolling contact with the third of the lobes. The manufacturing of such rocker arms involves producing the sliding contacts by investment casting, attaching them by soldering and coating them with a low-friction coating. This is an involved and relatively expensive process.
It would be desirable to produce a rocker arm that can be manufactured more easily and cost effectively.
An aspect of the invention provides a valve train assembly, comprising: a rocker arm comprising: a first body supporting a first axle on which is mounted a first roller configured to engage a first rotatable cam surface, wherein at least part of the rocker arm can be pivoted by at least the first rotatable cam surface to move a valve to cause a first valve event; a second body supporting a second axle on which is mounted a further roller configured to engage a further rotatable cam surface, wherein at least part of the rocker arm can be pivoted by the further rotatable cam surface to move the valve to cause a second valve event, wherein one of the first and second bodies is pivotally mounted with respect to the other of the first and second bodies; wherein the rocker arm is configurable in a first mode of operation in which one of the first and second valve events occurs and a second mode of operation in which both the first and second valve events occur or the other of the first and second valve events occurs; wherein the rocker arm further comprises a latch configured to latch and unlatch the first and second bodies together and wherein which of the first and second modes the rocker arm is configured in depends upon whether the first and second bodies are latched or are unlatched; wherein the latch comprises a latch member moveable between a latched position whereby the latch member latches the first and second bodies together and an unlatched position in which the first and second bodies are unlatched; and wherein the valve train assembly further comprises a latching actuator configured to move the latch member between the latched position and the unlatched position, wherein the latching actuator comprises a rotatable shaft attached to a biasing member, wherein rotating the rotatable shaft from a first position to a second position causes the biasing member to move the latch member between the latched position and the unlatched position.
The present invention will be described in even greater detail below based on the exemplary figures. The invention is not limited to the exemplary embodiments. All features described and/or illustrated herein can be used alone or combined in different combinations in embodiments of the invention. The features and advantages of various embodiments of the present invention will become apparent by reading the following detailed description with reference to the attached drawings which illustrate the following:
In an embodiment, the invention provides a rocker arm comprising: a first roller for engaging a first rotatable cam surface whereby at least part of the rocker arm can be pivoted by at least the first rotatable cam surface to move a valve to cause a first valve event; and a further roller for engaging a further rotatable cam surface whereby at least part of the rocker arm can be pivoted by the further rotatable cam surface to move the valve to cause a second valve event which is different from the first valve event.
Referring first to
The rocker arm 2 is provided with a pair of main lift rollers 22a and 22b rotatably mounted on an axle 24 carried by the outer body 10. One of the main lift rollers 22a is located one side of the outer body 10 and the other of the main lift rollers 22b is located the other side of the outer body 10. The rocker arm 2 is further provided with a secondary lift roller 26, located within the inner body 8 and rotatably mounted on an axle (not visible in
A three lobed camshaft 30 comprises a rotatable camshaft 32 mounted on which are first 34 and second 36 main lift cams and a secondary lift cam 38. The secondary lift cam 38 is positioned between the two main lift cams 34 and 36. The first main lift cam 34 is for engaging the first main lift roller 22a, the second main lift cam 36 is for engaging the second main lift roller 22b and the secondary lift cam 38 is for engaging the secondary lift roller 26. The first main lift cam 34 comprises a lift profile (i.e. a lobe) 34a and a base circle 34b, second main lift cam 36 comprises a lift profile 36a and a base circle 36b and the secondary lift cam 38 comprises a lift profile 38a and a base circle 38b. The lift profiles 34a and 36a are substantially of the same dimensions as each other and are angularly aligned. The lift profile 38a is smaller than the lift profiles 34a (both in terms of the height of its peak and in terms of the length of its base) and is angularly offset from them.
The rocker arm 2 is switchable between a dual lift mode which provides two operations of the valve 4 (a valve operation is an opening and corresponding closing of the valve) per engine cycle (e.g. full rotation of the cam shaft 32) and a single lift mode which provides a single operation of the valve 4 per engine cycle. In the dual lift mode, the inner body 8 and the outer body 10 are latched together by a latching arrangement 40 (see
During engine operation in the dual lift mode, as the cam shaft 32 rotates, the first main lift cam's lift profile 34a engages the first main lift roller 22a whilst, simultaneously, the second main lift cam's lift profile 36a engages the second main lift roller 22b and together they exert a force that causes the outer body 10 to pivot about the lash adjuster 6 to lift the valve stem 16 (i.e. move it downwards in the sense of the page) against the force of a valve spring thus opening the valve 4. As the peaks of the lift profiles 34a and 36a respectively pass out of engagement with the first main lift roller 22a and the second main lift roller 22b, the valve spring begins to close the valve 4 (i.e. the valve stem 16 is moved upwards in the sense of the page). When the first main lift cam's base circle 34b again engages the first main lift roller 22a and the second main lift cam's 36 lift profile engages the second main lift roller 22b the valve is fully closed and the main valve lift event is complete.
As the camshaft 32 continues to rotate, then, the secondary lift cam's lift profile 38a engages the secondary lift roller 26 exerting a force on the inner body 8 which force, as the inner body 8 and the outer body 10 are latched together, is transmitted to the outer body 10 causing the outer body 10 to pivot about the lash adjuster 6 to lift the valve stem 16 against the force of a valve spring thus opening the valve 4 a second time during the engine cycle. As the peak of the lift profile 38a passes out of engagement with the secondary lift roller 26 the valve spring begins to close the valve 4 again. When the secondary lift cam's base circle 38b again engages the secondary lift roller 26 the valve 4 is fully closed and the second valve lift event for the current engine cycle is complete.
The lift profile 38a is shallower and narrower than are the lift profiles 34a and 36a and so consequently the second valve lift event is lower and of a shorter duration than is the first valve lift event.
In the single lift mode the inner body 8 and the outer body 10 are not latched together by the latching arrangement 40 and hence in this mode, the inner body 8 is free to pivot with respect to the outer body 10 about the shaft 12. During engine operation in the single lift mode, as the cam shaft 32 rotates, when the first main lift cam's lift profile 34a engages the first main lift roller 22a and the second main lift cam's lift profile 36a engages the second main lift roller 22b, the outer body 10 pivots about the lash adjuster 6 and, in an identical way as in the dual lift mode, a main valve lift event occurs. As the camshaft 32 continues to rotate, then, the secondary lift cam's lift profile 38a engages the secondary lift roller 26 exerting a force on the inner body 8. In the single lift mode, however, as the inner body 8 and the outer body 10 are not latched together, this force is not transmitted to the outer body 10 which hence does not pivot about the lash adjuster 6 and so there is no additional valve event during the engine cycle. Instead, as the secondary lift cam's lift profile 38a engages the secondary lift roller 26, the inner body 8 pivots with respect to the inner body 10 about the shaft 12 accommodating the motion that otherwise would be transferred to the outer body 10. A torsional lost motion spring is provided to return the inner body 8 to its starting position relative to the outer body 10, once the peak of the lift profile 38a has passed out of engagement with the secondary lift roller 26.
In one embodiment, this arrangement may be used to provide switchable Internal Exhaust Gas Recirculation (IEGR) control. For example, if the valve 4 is an exhaust valve for an engine cylinder, the main valve lift acts as the main exhaust lift of an engine cycle, and the timing of the secondary valve lift may be arranged so that it occurs when an intake valve for that cylinder, controlled by a further rocker arm mounted pivotally on a further lash adjuster and which pivots in response to an intake cam mounted on the cam shaft 32, is open. The simultaneous opening of the intake and exhaust valves in this way ensures that a certain amount of exhaust gas remains in the cylinder during combustion which, as is well known, reduces NOx emissions. Switching to the single lift mode deactivates the IEGR function, which deactivation may be desirable under certain engine operating conditions. As will be appreciated by those skilled in the art, this switchable IEGR control may also be provided if the valve 4 is an intake valve with the timing of the secondary valve lift arranged to occur when an exhaust valve for that cylinder is open during the exhaust part of an engine cycle.
The first base portion 64a defines a recess 76 for engaging the end of the valve stem 16 and the second base portion 64b defines a part spherical recess 78 to permit pivoting about a part spherical end of the lash adjuster 6.
Advantageously, as the rocker arm 2 incorporates three roller contacts for the camshaft 30 and no slider contacts, the outer body 10 and the inner body 8 may be manufactured from stamped sheet metal. The latch contact surface 54 may be formed in the inner body 8 by stamping (shearing) using a suitable stamping tool. The use of stamped sheet metal provides for a cost effective manufacturing process. The roller contacts also provide relatively low friction contacts with the cams without the need for low friction coatings.
As is best understood from
As is also best seen from
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An actuator 94 is provided to move the latching arrangement 40 between the un-latched and latched positions. In this example, the actuator comprises an actuator shaft 96 and a biasing means 98, preferably a leaf spring. In the default unlatched configuration, the leaf spring 98 does not engage the latching arrangement 40. To enter the latched configuration, the shaft 96 is rotated a certain amount (for example 12 degrees) causing the leaf spring 98 to engage the roller 88 and to push the latching arrangement 40 into the latched position. A spring 85 mounted over the latch pin 80 and supported between an outer face of the end wall 66 and the winged members of the member 84 is biased to caused the latching arrangement 40 to return to its unlatched position when the actuator shaft 96 is rotated back to its unlatched position and the leaf spring 98 disengages the roller 88.
Other types of actuators for the latching arrangement that may for example make use of pressurised oil, electromechanical systems or pneumatic systems will be known to those skilled in the art.
The actuator shaft 94 may also be used as an oil spray bar that sprays oil to lubricate or cool the valve train components.
Advantageously, when the base circle 38b engages the inner bushing/axle 43, the inner bushing axle 43 stops always on the axle 24 which ensures that the orientation of the various components is such that the latch pin 80 is free to move in and out of the latched and unlatched positions.
As previously mentioned, in an alternative arrangement (not illustrated) the valve 4 is an intake valve rather than an exhaust valve (making the rocker arm 2 an intake rocker arm) and an exhaust rocker arm operates an exhaust valve in response to an exhaust cam mounted on the cam shaft. In this alternative arrangement the cams are arranged so that in any given engine cycle, the additional smaller opening of the intake valve occurs when the exhaust valve is open to thereby provide a degree of internal exhaust gas recirculation.
The above embodiment is to be understood as an illustrative example of the invention only. Further embodiments of the invention are envisaged. For example, in an alternative embodiment the inner body 8 is permanently fixed with respect to the outer body 10 such that there is only one mode of operation in which the main and secondary valve lifts occur in every engine cycle. Although in the described embodiment, in one mode of operation, there are two different valve lifts per engine cycle (a high lift at one point in the cycle and a low lift in another part of the cycle) the rocker arm may be arranged to provide alternative types of dual mode operation, for example, a first mode in which there is a single type of valve lift (e.g. a high lift) per engine cycle and a second mode in which there is a different single type of valve lift (e.g. a lower lift) per engine cycle. The different lifts may be at the same point or at different points in the engine cycle. Accordingly, although in the described embodiment the valve train 1 is arranged so that the additional lift provides for IEGR, it is to be understood that this is only a preferred example of a use of an embodiment of the invention. It is to be understood that any feature described in relation to any one embodiment may be used alone, or in combination with other features described, and may also be used in combination with one or more features of any other of the embodiments, or any combination of any other of the embodiments. Furthermore, equivalents and modifications not described above may also be employed without departing from the scope of the invention, which is defined in the accompanying claims.
While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive. It will be understood that changes and modifications may be made by those of ordinary skill within the scope of the following claims. In particular, the present invention covers further embodiments with any combination of features from different embodiments described above and below. Additionally, statements made herein characterizing the invention refer to an embodiment of the invention and not necessarily all embodiments.
The terms used in the claims should be construed to have the broadest reasonable interpretation consistent with the foregoing description. For example, the use of the article “a” or “the” in introducing an element should not be interpreted as being exclusive of a plurality of elements. Likewise, the recitation of “or” should be interpreted as being inclusive, such that the recitation of “A or B” is not exclusive of “A and B,” unless it is clear from the context or the foregoing description that only one of A and B is intended. Further, the recitation of “at least one of A, B, and C” should be interpreted as one or more of a group of elements consisting of A, B, and C, and should not be interpreted as requiring at least one of each of the listed elements A, B, and C, regardless of whether A, B, and C are related as categories or otherwise. Moreover, the recitation of “A, B, and/or C” or “at least one of A, B, or C” should be interpreted as including any singular entity from the listed elements, e.g., A, any subset from the listed elements, e.g., A and B, or the entire list of elements A, B, and C.
Number | Date | Country | Kind |
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12164703 | Apr 2012 | EP | regional |
This application is a continuation of U.S. application Ser. No. 14/395,500, filed Oct. 20, 2014, which is a U.S. National Stage application under 35 U.S.C. § 371 of International Application No. PCT/EP2013/058208, filed on Apr. 19, 2013, claiming benefit to European Patent Application No. 12164703.6, filed on Apr. 19, 2012, all of which applications are hereby incorporated by reference herein in their entireties. The International Application was published in English on Oct. 24, 2013, as WO 2013/156610 A1 under PCT Article 21(2).
Number | Name | Date | Kind |
---|---|---|---|
4151817 | Mueller | May 1979 | A |
5524580 | Muir | Jun 1996 | A |
5529033 | Hampton | Jun 1996 | A |
6314928 | Baraszu et al. | Nov 2001 | B1 |
6439179 | Hendriksma et al. | Aug 2002 | B2 |
6732685 | Leman | May 2004 | B2 |
7730861 | Ng | Jun 2010 | B2 |
9470116 | Cecur | Oct 2016 | B2 |
20010023675 | Lee et al. | Sep 2001 | A1 |
20010027765 | Hendriksma et al. | Oct 2001 | A1 |
20010035140 | Fernandez et al. | Nov 2001 | A1 |
20060144356 | Sellnau et al. | Jul 2006 | A1 |
20070101958 | Seitz | May 2007 | A1 |
20080127917 | Riley et al. | Jun 2008 | A1 |
20080223324 | Ng | Sep 2008 | A1 |
20100043737 | Elnick et al. | Feb 2010 | A1 |
20100236507 | Kang et al. | Sep 2010 | A1 |
20100275864 | Gemein et al. | Nov 2010 | A1 |
20110005483 | Manther et al. | Jan 2011 | A1 |
20110197842 | Manther et al. | Aug 2011 | A1 |
20110226208 | Zurface et al. | Sep 2011 | A1 |
Number | Date | Country |
---|---|---|
2753197 | Jun 1978 | DE |
102010011826 | Dec 2011 | DE |
0735249 | Oct 1996 | EP |
0767296 | Apr 1997 | EP |
1149988 | Oct 2001 | EP |
1338760 | Aug 2003 | EP |
1561013 | Aug 2005 | EP |
1785595 | May 2007 | EP |
WO 2011156684 | Dec 2011 | WO |
Number | Date | Country | |
---|---|---|---|
20170002698 A1 | Jan 2017 | US |
Number | Date | Country | |
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Parent | 14395500 | US | |
Child | 15265878 | US |