This application is directed to deactivating rocker arms for internal combustion engines.
Many internal combustion engines utilize rocker arms to transfer rotational motion of cams to linear motion appropriate for opening and closing engine valves. Deactivating rocker arms incorporate mechanisms that allow for selective activation and deactivation of the rocker arm. In a deactivated state, the rocker arm may exhibit lost motion movement. In order to return to an activated state from a deactivated state, the mechanism may require that the rocker arm be in a particular position or within a range of positions that may not be readily achieved while undergoing certain unconstrained movement while in the deactivated state, such as during excessive lash adjuster pump-up.
In one embodiment, a rocker arm for engaging a cam having at least one lift lobe and at least one substantially circular safety lobe is provided. The lift lobes that the rocker arm is configured to be capable of engaging have a lift lobe base circle, each having a base circle diameter, while the circular safety lobes are positioned concentrically with the base circle of the lift lobe and have a diameter less than the diameter of the base circle. The rocker arm has an outer arm, an inner arm, a pivot axle, a lift lobe contacting bearing, a bearing axle, and a bearing axle spring. The outer arm and inner arm have first and second side arms. The first and second outer side arms have at least one safety lobe contacting surface among them configured to be spaced from the safety lobes during normal engine operation. The first and second outer side arms also have outer pivot axle apertures configured to accept the pivot axle. The inner arm is disposed between the first and second outer side arms. The first and second inner side arms also have inner pivot axle apertures configured to accept the pivot axle. The first and second inner side arms have inner bearing axle apertures configured to accept the bearing axle. The pivot axle is mounted within the inner pivot axle apertures and the outer pivot axle apertures, while the bearing axle is mounted in the bearing axle apertures of the inner arm. One or more bearing axle springs are secured to the outer arm and are in biasing contact with the bearing axle. The lift lobe contacting bearing is mounted to the bearing axle between the first and second inner side arm.
In another embodiment, a rocker arm for engaging a cam having a lift lobe and at least one safety lobe comprises a cam contacting member for transferring motion from the cam to the rocker arm, and at least one biasing spring. An outer arm of the rocker arm has at least one safety lobe contacting surface configured to be capable of contacting one or more safety lobes only during abnormal rocker arm operation. The inner arm is disposed between the first and second side arms of the outer arm, and has a first and second inner side arm. The cam contacting member is disposed between the first and second inner side arms.
In yet another embodiment, a deactivating rocker arm for engaging a cam having a lift lobe and a first and second safety lobe is provided. The rocker arm comprises a first end and a second end, an outer arm, an inner arm, a pivot axle, a lift lobe contacting member for transferring motion from the cam to the rocker arm, a latch for selectively deactivating the rocker arm, and at least one biasing spring. The outer arm has a first and second outer side arm. The first and second outer side arms have safety lobe contacting surfaces configured to be in contact with the first and second safety lobes only during abnormal rocker arm operation. Axle slots in the outer side arms are configured to accept the lift lobe contacting member and are also configured to permit lost motion movement of the inner arm relative to the outer arm.
It will be appreciated that the illustrated boundaries of elements in the drawings represent only one example of the boundaries. One of ordinary skill in the art will appreciate that a single element may be designed as multiple elements or that multiple elements may be designed as a single element. An element shown as an internal feature may be implemented as an external feature and vice versa.
Further, in the accompanying drawings and description that follow, like parts are indicated throughout the drawings and description with the same reference numerals, respectively. The figures may not be drawn to scale and the proportions of certain parts have been exaggerated for convenience of illustration.
Certain terminology will be used in the following description for convenience in describing the figures will not be limiting. The terms “upward,” “downward,” and other directional terms used herein will be understood to have their normal meanings and will refer to those directions as the drawing figures are normally viewed.
As shown in
The rocker arm 100 has a bearing 190 comprising a roller 116 that is mounted between the first inner side arm 110 and second inner side arm 112 on a bearing axle 118 that, during normal operation of the rocker arm, serves to transfer energy from a rotating cam (not shown) to the rocker arm 100. Mounting the roller 116 on the bearing axle 118 allows the bearing 190 to rotate about the axle 118, which serves to reduce the friction generated by the contact of the rotating cam with the roller 116. As discussed herein, the roller 116 is rotatably secured to the inner arm 108, which in turn may rotate relative to the outer arm 102 about the pivot axle 114 under certain conditions. In the illustrated embodiment, the bearing axle 118 is mounted to the inner arm 108 in the bearing axle apertures 260 of the inner arm 108 and extends through the bearing axle slots 126 of the outer arm 102. Other configurations are possible when utilizing a bearing axle 118, such as having the bearing axle 118 not extend through bearing axle slots 126 but still mounted in bearing axle apertures 260 of the inner arm 108, for example.
When the rocker arm 100 is in a deactivated state, the inner arm 108 pivots downwardly relative to the outer arm 102 when the lifting portion of the cam (324 in
As shown in
With continued reference to
Other configurations other than bearing 190 also permit the transfer of motion from the cam to the rocker arm 100. For example, a smooth non-rotating surface (not shown) for interfacing with the cam lift lobe (320 in
The mechanism for selectively deactivating the rocker arm 100, which in the illustrated embodiment is found near the second end 103 of the rocker arm 100, is shown in
In the assembled rocker arm 100, the latch 202 alternates between activating and deactivating positions. To deactivate the rocker arm 100, oil pressure sufficient to counteract the biasing force of latch spring 204 may be applied, for example, through the port 212 which is configured to permit oil pressure to be applied to the surface of the latch 202. When the oil pressure is applied, the latch 202 is pushed toward the second end 103 of the rocker arm 100, thereby withdrawing the latch 202 from engagement with the inner arm 108 and allowing the inner arm 108 to rotate about the pivot axle 114. In both the activated and deactivated states, the linear portion 250 of orientation clip 214 engages the latch 202 at the flat surface 218. The orientation clip is mounted in the clip apertures 216, and thereby maintains a horizontal orientation of the linear portion 250 relative to the rocker arm 100. This restricts the orientation of the flat surface 218 to also be horizontal, thereby orienting the latch 202 in the appropriate direction for consistent engagement with the inner arm 108.
With reference to
During normal operation, which may occur when the rocker arm 100 is in an activated or deactivated state, a gap 330 separates the safety lobes 310 from the first and second safety lobe contacting surfaces 120, 122. However, during certain abnormal operation, the safety lobes 310 may come into contact with the first and second safety lobe contacting surfaces 120, 122. In one such scenario, a deactivated rocker arm 100 is subjected to excessive pump-up of the lash adjuster 340, whether due to excessive oil pressure, the onset of non-steady-state conditions, for example as a result of dynamic mis-motion that may be caused by high revolutions per second, or other causes. This results in an increase in the effective length of the lash adjuster 340 as pressurized oil fills its interior. Such a scenario may occur for example during a cold start of the engine, and could take significant time to resolve on its own if left unchecked and could even result in permanent engine damage. Under such circumstances, the latch 202 may not be able to activate the rocker arm 100 until the lash adjuster 340 has returned to a normal operating length. In this scenario, the lash adjuster 340 applies upward pressure to the outer arm 102, bringing the outer arm 102 closer to the cam 300. As the outer arm 102 continues upward, the safety lobe contacting surfaces 120, 122 come into contact with the safety lobes 310, preventing further upward movement of the outer arm 102, which, if unimpeded, could result in a portion of the rocker arm 100 near the rocker arm second end 103 undesirably contacting the cam 300. This illustrated embodiment allows for relatively quicker return to normal operating conditions for the rocker arm 100, and in addition may allow for the rocker arm 100 to return to an activated state more quickly, thus avoiding an excessively long recovery time waiting for the rocker arm 100 to return to an activated state.
Still other scenarios may result in the safety lobe contacting surfaces 120, 122 coming into contact with the safety lobes 310. For example, a failure of the roller 116 or the bearing axle 118, or a failure of the lift lobe 320 may result in the safety lobe contacting surfaces 120, 122 coming into contact with the safety lobes 310. It should be noted that not all abnormal operating circumstances for the rocker arm will result in the safety lobes 310 coming into contact with the first and second safety lobe contacting surfaces 120, 122.
For the purposes of this disclosure and unless otherwise specified, “a” or “an” means “one or more.” To the extent that the term “includes” or “including” is used in the specification or the claims, it is intended to be inclusive in a manner similar to the term “comprising” as that term is interpreted when employed as a transitional word in a claim. Furthermore, to the extent that the term “or” is employed (e.g., A or B) it is intended to mean “A or B or both.” When the applicants intend to indicate “only A or B but not both” then the term “only A or B but not both” will be employed. Thus, use of the term “or” herein is the inclusive, and not the exclusive use. See, Bryan A. Garner, A Dictionary of Modern Legal Usage 624 (2d. Ed. 1995). Also, to the extent that the terms “in” or “into” are used in the specification or the claims, it is intended to additionally mean “on” or “onto.” Furthermore, to the extent the term “connect” is used in the specification or claims, it is intended to mean not only “directly connected to,” but also “indirectly connected to” such as connected through another component or multiple components. As used herein, “about” will be understood by persons of ordinary skill in the art and will vary to some extent depending upon the context in which it is used. If there are uses of the term which are not clear to persons of ordinary skill in the art, given the context in which it is used, “about” will mean up to plus or minus 10% of the particular term. From about X to Y is intended to mean from about X to about Y, where X and Y are the specified values.
While the present disclosure illustrates various embodiments, and while these embodiments have been described in some detail, it is not the intention of the applicant to restrict or in any way limit the scope of the claimed invention to such detail. Additional advantages and modifications will readily appear to those skilled in the art. Therefore, the invention, in its broader aspects, is not limited to the specific details and illustrative examples shown and described. Accordingly, departures may be made from such details without departing from the spirit or scope of the applicant's claimed invention. Moreover, the foregoing embodiments are illustrative, and no single feature or element is essential to all possible combinations that may be claimed in this or a later application.