Patent Grant
10077686
The instant disclosure relates generally to actuating one or more engine valves in an internal combustion engine and, in particular, to valve actuation including a lost motion system.
As known in the art, valve actuation in an internal combustion engine controls the production of positive power. During positive power, intake valves may be opened to admit fuel and air into a cylinder for combustion. One or more exhaust valves may be opened to allow combustion gas to escape from the cylinder. Intake, exhaust, and/or auxiliary valves may also be controlled to provide auxiliary valve events, such as (but not limited to) compression-release (CR) engine braking, bleeder engine braking, exhaust gas recirculation (EGR), internal exhaust gas recirculation (IEGR), brake gas recirculation (BGR) as well as so-called variable valve timing (VVT) events such as early exhaust valve opening (EEVO), late intake valve opening (LIVO), etc.
As noted, engine valve actuation also may be used to produce engine braking and exhaust gas recirculation when the engine is not being used to produce positive power. During engine braking, one or more exhaust valves may be selectively opened to convert, at least temporarily, the engine into an air compressor. In doing so, the engine develops retarding horsepower to help slow a vehicle down. This can provide the operator with increased control over the vehicle and substantially reduce wear on the service brakes of the vehicle.
One method of adjusting valve timing and lift, particularly in the context of engine braking, has been to incorporate a lost motion component in a valve train linkage between the valve and a valve actuation motion source. In the context of internal combustion engines, lost motion is a term applied to a class of technical solutions for modifying the valve motion dictated by a valve actuation motion source with a variable length mechanical, hydraulic or other linkage assembly. In a lost motion system the valve actuation motion source may provide the maximum dwell (time) and greatest lift motion needed over a full range of engine operating conditions. A variable length system may then be included in the valve train linkage between the valve to be opened and the valve actuation motion source to subtract or “lose” part or all of the motion imparted from the valve actuation motion source to the valve. This variable length system, or lost motion system may, when expanded fully, transmit all of the available motion to the valve and when contracted fully transmit none or a minimum amount of the available motion to the valve.
An example of such a valve actuation system 100 comprising a lost motion component is shown schematically in
The controller 150 may comprise any electronic (e.g., a microprocessor, microcontroller, digital signal processor, co-processor or the like or combinations thereof capable of executing stored instructions, or programmable logic arrays or the like, as embodied, for example, in an engine control unit (ECU)) or mechanical device for causing all or a portion of the motion from the valve actuation motion source 110 to be transferred, or not transferred, through the rocker arm 120 to the engine valve(s) 140. For example, the controller 150 may control a switched device (e.g., a solenoid supply valve) to selectively supply hydraulic fluid to the rocker arm 120. Alternatively, or additionally, the controller 150 may be coupled to one or more sensors (not shown) that provide data used by the controller 150 to determine how to control the switched device(s). Engine valve events may be optimized at a plurality of engine operating conditions (e.g., speeds, loads, temperatures, pressures, positional information, etc.) based upon information collected by the controller 150 via such sensors.
Where the lost motion component 130 is hydraulically actuated, the supply of the necessary hydraulic fluid is of critical importance to the successful operation of the valve actuation system 100. This is particularly true of so-called bridge brake systems in which the lost motion component 130 is supported by or deployed within a valve bridge (not shown) and hydraulic fluid for actuating the lost motion component 130 is supplied via the rocker arm 120. In the related U.S. patent application Ser. No. 14/799,813, structures are described for biasing the rocker arm 120 and a valve bridge-based lost motion component 130 into contact with each other, particularly in systems in which the rocker arm 130 is biased into contact with the valve actuation motion source 110, which, as noted above, may include a pushrod-based valve train. As known in the art, pushrod-type engines have valve trains with comparatively large reciprocating mass and it is necessary to maintain contact between the pushrod and valve actuation motion source, e.g., a cam or cam follower. Consequently, the forces required to control the pushrod motion are often higher than can be reasonably provided by systems that bias the rocker arm against the pushrod, i.e., the valve actuation motion source. Alternatively, where the rocker arm is biased toward a lost motion component in a valve bridge, excessive play or lash in the pushrod-to-rocker arm, or pushrod-to-cam follower interface leads to noise, impact loading, etc.
In order to maintain contact between a pushrod and its corresponding valve actuation motion source, it is known to incorporate spring biasing into the pushrod itself, as illustrated in
The instant disclosure describes a pushrod assembly for an internal combustion engine comprising a pushrod having a first end and a second end, the first end being configured to receive valve actuation motions from a valve actuation motion source and the second end being configured to impart the valve actuation motions to a valve train component. Furthermore, the pushrod comprises a resilient element engagement feature. The pushrod assembly further comprises a fixed support and a resilient element operatively connected to the resilient element engagement feature and the fixed support. The resilient element is further configured to bias the pushrod, via the resilient element engagement feature, toward the valve actuation motion source. In an embodiment, the resilient element engagement feature may be disposed proximally to the second end of the pushrod and, in another embodiment, the resilient element engagement feature may comprise a retainer affixed to the pushrod. The resilient element may comprise a coil spring surrounding the pushrod.
An internal combustion engine may comprise the pushrod assembly described herein. A follower assembly may be provided to maintain contact between second end of the pushrod and the valve train component, where the follower assembly comprises a sliding member operatively connected to a sliding member resilient element that, in turn, is configured to bias the sliding member toward the pushrod. The sliding member may be disposed within a bore formed in the valve train component and the sliding member resilient element may be operatively connected to the valve train component. The valve train component may comprise a first contact surface and the sliding member may comprise a second contact surface complementary to the first contact surface such that engagement of the first and second contact surface permits the valve actuation motions to be conveyed to the valve train component. In another embodiment, the follower assembly may further comprise an adjustable housing disposed within the bore and having its own internal bore, wherein the sliding member is disposed within the internal bore and the sliding member resilient element is operatively connected to the adjustable housing. In this embodiment, the adjustable housing may comprise the first contact surface configured to mate with the second contact surface formed on the sliding member. In yet another embodiment, the valve train component is a rocker arm.
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:
Referring now to
Though not illustrated in
As shown, the motion imparting end 314 of the rocker arm 310 conveys valve actuation motions (solid arrows) provided by the valve actuation motion source 110 to the lost motion component 330 of the valve bridge 320. Though not shown in
The valve bridge 320 operatively connects to two or more engine valves 140 that, as noted previously, may comprise intake valves, exhaust valves and/or auxiliary valves, as known in the art. The lost motion component 330 is supported by the valve bridge 320 and is configured to receive the valve actuation motions and hydraulic fluid from the motion imparting end 314 of the rocker arm 310. The lost motion component 330 is hydraulically-actuated in the sense that the supply of hydraulic fluid causes the lost motion component 330 to either assume a state in which the received valve actuation motions are conveyed to the valve bridge 320 and, consequently, the valves 140, or a state in which the received valve actuation motions are not conveyed to the valve bridge 320 and are therefore “lost.” An example of a lost motion component in a valve bridge is taught in U.S. Pat. No. 7,905,208, the teachings of which are incorporated herein by this reference, in which valve actuation motions from the rocker arm are lost when hydraulic fluid is not provided to the lost motion component, but are conveyed to the valve bridge and valves when hydraulic fluid is provided to the lost motion component. In lost motion components 330 of this type, a check valve (not shown) is provided to permit one-way flow of hydraulic fluid into the lost motion component 330. The check valve permits the lost motion component 330 to establish a locked volume of hydraulic fluid that, due to the substantially incompressible nature of the hydraulic fluid, allows the lost motion component 330 to operate in substantially rigid fashion thereby conveying the received valve actuation motions.
As further illustrated in the embodiment of
It is noted that the rocker arm 310 is a specific implementation of a valve train component that receives valve actuation motions from the valve actuation motion source 110. As those skilled in the art will appreciate, other types of valve train components may be used to receive the valve actuation motions. For example, a tappet may be positioned as an intervening element between the pushrod 350 and the rocker arm 310. Thus, where reference is made herein to a rocker arm as receiving the valve actuation motions from a pushrod, it is understood that a more generalized valve train component of the types known in the art may be equally employed.
In an embodiment, the pushrod 350 comprises a resilient element engagement feature configured to be operatively connected to a resilient element 352. For example, the resilient element engagement feature may comprise an opening, indentation, protuberance, shoulder, etc. integrally formed in the pushrod 350 capable of receiving, and conveying to the pushrod 350, bias force provided by the resilient element 352. Alternatively, the resilient element engagement feature may comprise a component that is affixed to, but not otherwise integrally formed in, the pushrod 350, an example of which is further described below. The resilient element 352 may comprise any of a variety of springs (such as compression or tension springs in the form of coil or flat springs, etc.) or equivalents thereof.
As further shown in
As alluded to above, in some embodiments, it may be desirable to bias the rocker arm 310 into contact with the valve bridge 320, particularly in order to ensure proper flow of hydraulic fluid from the motion imparting end 314 of the rocker arm 310 to the lost motion component 330 of the valve bridge 320. This problem can be even more pronounced where the above-described pushrod assembly (i.e. pushrod 350, resilient element 352 and fixed support 354), as described above, biases the pushrod 350 away from the pushrod/rocker arm interface. Consequently, lash or gaps may be present between the motion receiving end 312 of the rocker arm 310 and the pushrod 350, which in turn could result in noise, undesirable impact loading or possible dislodgement of ball/socket joints between the rocker arm 310 and pushrod 350. To avoid such lash, as the potential problems that may result, the rocker arm 310 may be equipped with a follower assembly comprising a sliding member 370 that is biased into contact with the pushrod 350 by a corresponding sliding member resilient element 372. Various embodiments of pushrod and follower assemblies in accordance with the instant disclosure are further illustrated and described below with respect to
Referring now to
In the implementation of
The sliding member resilient element 522, which may comprise any of the above-mentioned types of springs or the like, is operatively connected to the adjustable housing 524 (or rocker arm 502 if the adjustable housing 524 is not provided) and the sliding member 520 such that the sliding member is biased toward the pushrod assembly 400. As best shown in
Conversely, in those instances in which the rocker arm 502 rotates or is biased away from the pushrod assembly 400, as best shown in
As described above relative to
As further shown, the pushrod assembly 700 includes a follower assembly comprising the pushrod sliding member 206 of
As further shown, the sliding member 206 may further comprise a receptacle or socket 722 to rotatably receive a corresponding coupling member of another valve train component as described above. Additionally, the sliding member 206 comprises a first contact surface 726 configured to engage with a complementary second contact surface 728 formed in the second end 404 of the pushrod 402. Thus, when lash between the pushrod assembly 700 and the valve train component arises, the sliding member 206 is biased toward the valve train component, thereby taking up the lash space. Conversely, movement of the pushrod 402 during valve lift motions sufficiently high to take up any existing lash causes the first and second contact surfaces 726, 728 to engage, thereby establishing a rigid interface between the pushrod 402 and sliding assembly 206. This rigid interface then permits the sliding member 206 to convey such motions from the pushrod 402 to the valve train component.
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.
The instant application claims the benefit of Provisional U.S. Patent Application Ser. No. 62/024,629 entitled “Valve Bridge With Integrated Lost Motion System” and filed Jul. 15, 2014, the teachings of which are incorporated herein by this reference. The instant application is also related to co-pending U.S. patent application Ser. No. 14/799,813, entitled “Bias Mechanisms For A Rocker Arm And Lost Motion Component Of A Valve Bridge”, and to co-pending U.S. patent application Ser. No. 14/799,837, entitled “System Comprising An Accumulator Upstream Of A Lost Motion Component In A Valve Bridge”, both filed on even date herewith.
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