Patent Application
20180094553
The present disclosure relates to valve systems for internal combustion engines. More particularly, the present disclosure relates to a valve bridge that includes a guide structure for guiding the valve bridge with one or more valves of the valve system.
When a cylinder applied in an internal combustion engine is equipped with more than one of the same type of gas exchange valves (e.g., more than one intake valve and/or more than one exhaust valve), all valves of the same type are typically opened and closed at about the same time. In order to reduce a number of camshafts, cam lobes, rocker arms, and/or the like components, required to open the valves, a valve bridge is often used to interconnect the same type of valves with a common rocker arm. Valve bridges are typically actuated by a rocker arm, to contact terminal ends of valve stems associated with the same type of valves to cause the valves to synchronously operate between an open and a closed position. Typically, the rocker arm articulates and executes a to-and-fro motion and slides against the valve body to cause the valve body to reciprocate relative to the cylinder. During a sliding motion, however, a point of contact between the rocker arm and the valve bridge may dynamically change. As a result, the rocker arm may distribute unequal forces and stresses to the valve bridge causing the valve bridge to tilt in one or more dimensions. Such a situation may in turn increase the chances for the valve bridge to be dislodged or be unseated from the valves, leading to increased chances of a dropped valve.
U.S. Pat. No. 7,984,705 ('705 reference) relates to an Engine Braking Apparatus with Two-Level Pressure Control Valves. The '705 reference discloses a valve bridge that is supported by two spring seats. A supporting spring is used to bias the spring seat to a spring retainer that acts as a guide to a sliding of the spring seat.
In one aspect, the disclosure is directed towards a valve bridge for a valve system of an engine. The valve system includes one or more valves and a valve rotator coupled to the one or more valves. The valve bridge includes one or more end portions. A seat is formed at the end portions to receive the valves. An extension portion extends outwardly from the end portions. Further, a cavity is defined within the extension, and which is configured to accommodate the valve rotator, and guide the valve bridge with the valve rotator during each opening and closing of the one or more valves relative to the engine.
In another aspect, the disclosure relates to a valve system for an engine. the valve system includes one or more valves, a valve rotator coupled to the one or more valves, and a valve bridge. The valve bridge includes one or more end portions, an extension portion extending outwardly from the one or more end portions and defining a cavity within the extension portion. The cavity is configured to accommodate the valve rotator, and guide the valve bridge with the valve rotator during each opening and closing of the one or more valves relative to the engine.
In yet another aspect, the disclosure is directed to a valve bridge for a valve system of an engine. The valve bridge includes a tappet head, a first arm and a second arm radially extending away from the tappet head to respectively define a first end portion and a second end portion. Further, the valve bridge includes a seat formed at each of the first end portion and the second end portion that are configured to receive a gas exchange valve of the engine. An extension portion extends outwardly from each of the first end portion and the second end portion, and each of the first end portion and the second end portion defines a cavity. The cavity is configured to accommodate a valve rotator coupled to the gas exchange valve, and guide the valve bridge with the valve rotator during each opening and closing of the gas exchange valve relative to the engine.
Referring to
The engine 102 may be a four-stroke internal combustion engine. However, the engine 102 may also operate according to be a two-stroke principle. In general, the engine 102 may include or represent any type of an internal combustion engine, including a gasoline engine, a spark-ignition engine, a compression-ignition engine, a gaseous fuel-powered engine, and the like. The engine 102 may include a cylinder 108 with a combustion chamber 110. The cylinder 108 may include a piston 114 and a connecting rod 116 coupled to the piston 114, as is customary. Although a single cylinder configuration is shown in
Referring to
The valves 124, 124′ are categorized into a first valve 124 and a second valve 124′. The first valve 124 and the second valve 124′ may be a fluid exchange valve or a gas exchange valves that facilitate gas exchange between the combustion chamber 110 and a gas exchange manifold 140 structured within a cylinder head 142 of the engine 102, as shown. For the purposes of the present disclosure, a gas exchange may pertain to one of an inflow of fuel or an outflow of combustions gases relative to the engine 102, and the term ‘gas exchange valves’ may pertain to valves that facilitate such inflow and/or outflow. In this regard, the valves 124, 124′ may be one of intake valves or exhaust valves, and the gas exchange manifold 140 may be one of an intake manifold or an exhaust manifold depending upon the type of valves used (i.e. intake or exhaust). A first port 146, and a second port 146′ may be structured into the cylinder head 142, or a wall 144 of the cylinder head 142, to facilitate the gas exchange between the combustion chamber 110 and the gas exchange manifold 140. The first port 146 may include a first valve seat 148. The first port 146 may be selectively closed (i.e. a closed position) and opened (i.e. an open position) by a reciprocal movement of the first valve 124, relative to the engine 102. Similarly, the second port 146′ may be selectively closed (i.e. a closed position) and opened (i.e. an open position) by a reciprocal movement of the second valve 124′, relative to the engine 102. The reciprocal movement of the valves 124, 124′ may be synchronous, following a general practice of the art. For clarity and ease in understanding, further description includes discussions of a structure and arrangement of the first valve 124 alone. These discussions may be equivalently applied to the second valve 124′ as well. Wherever applicable, the second valve 124′ may also be discussed by way of specific references.
The first valve 124 includes a first disk portion 150, a first valve stem 152, and a first spring 154 arranged around the first valve stem 152. In the closed position of the first valve 124, the first disk portion 150 is configured to lock the first port 146 by being engaged or locked against the first valve seat 148, thereby disallowing the gas exchange to occur through the first port 146. In the open position, conversely, the first disk portion 150 may be disengaged or distanced from the first valve seat 148, allowing a gas exchange to occur through the first port 146. In both cases, the first valve stem 152 may pass through the first port 146 and the wall 144 of the cylinder head 142, with the first spring 154 biasing the first valve 124 against the valve bridge 136 and the rocker arm 134. The depicted orientation of the valve system 104 of
In some implementations, additional valves may be incorporated into the engine 102 depending upon the engine's output requirement. Further, the gas exchange manifold 140 may also represent or include a number of manifolds that facilitate gas exchange. In one exemplary embodiment, the valves 124, 124′ are intake valves and the gas exchange manifold 140 is an intake manifold. In this regard, the engine 102 may also include exhaust valves (see
Referring again to
In some implementations, a motion from the cam lobe 132 to the cam roller portion 158 of the rocker arm 134 may be transmitted through a push rod arrangement (not shown). Further, a cam lobe (not shown), similar to the cam lobe 132, may be coupled to the camshaft 130 to facilitate an operation of the exhaust valves, such as the first exhaust valve 124a, as well. A working of such a cam lobe may remain similar to a working of the cam lobe 132, as has been discussed above. In some implementations, the engine 102 may include multiple cam lobes depending upon engine specifications and cylinder design. Although details and embodiments of the crankshaft 120, the camshaft 130, and the rocker arm 134, have been discussed above, it will be appreciated that these details and embodiments are not limited in any way.
Referring
The valve bridge 136 may include a first seat 206 formed on the base 186, at the first end portion 194. The first seat 206 is configured to receive the first valve 124. More specifically, the first seat 206 includes and/or is structured in the form of a recess or a stem guide pocket that may receive an end 210 (or an upper surface) of the first valve stem 152 of the first valve 124, as depicted in
In some implementations, the recess of the first seat 206 may be machined or made up of mild steel and manufactured by a milling process. Alternatively, the recess may be manufactured by a single process involving casting, for example. In some implementations, the recess may be omitted from the valve bridge 136 to serve a design requirement, such as a space constraint, and the like, of the engine system 100. In such a case, the first seat 206 may include no recess at all, and may rather include a flattened surface, flush in relation to a surrounding surface of the base 186. In such a case, the end 210 may be unable to extend or be inserted into the first seat 206 to retain the valve bridge 136, and rather, the end 210 of the first valve stem 152 may simply abut against the flattened surface of the first seat 206, in assembly. Therefore, aspects of the present disclosure, directed to the first seat 206 having a recess, need not be seen as being limiting in any way. Further, a second seat 206′, similar to the first seat 206 in form and function, may be provided at the second end portion 196, as well.
In some implementations, the tappet head 176 may include a bore 214 (see
The set of valve rotators 128, 128′ includes a first valve rotator 128 and a second valve rotator 128′. The first valve rotator 128 is positioned around the first valve stem 152, and placed adjacent to the end 210, so that when the first valve 124 is opened and closed, the first valve 124 will rotate (see direction, E) a small amount with each opening and closing. With each reciprocation (see direction, C), since the first valve rotator 128 ensures that the first valve 124 rotates this small amount, a concentration of a valve defect or deformations at a sole region on the first valve 124, particularly at the first disk portion 150 of the first valve 124, is avoided. The first valve rotator 128 may include a circular, dished, or a disk shaped structure, and may include a retainer flange 224 bounded by an offset peripheral flange (or simply a peripheral flange 226). The retainer flange 224 may be rigidly coupled to the first valve stem 152 at a portion adjacent to the end 210, while the retainer flange 224 may be press fitted into the peripheral flange 226. The peripheral flange 226 includes a flat circular portion termed as a circular shoulder 228, where an upper end 230 of the first spring 154 (as seen in the orientation of the
The guide structure 184 is configured to guide the valve bridge 136 with the valve rotators 128, 128′ (and in turn with the valves 124, 124′) during each opening and closing of the valves 124, 124′. The guide structure 184 includes a first guide 236 and a second guide 236′. The first guide 236 and the second guide 236′ are respectively structured and arranged on the base 186, at the first end portion 194 and the second end portion 196. As with the description above, for clarity, ease in understanding, and referencing, further discussions of the guide structure 184 will be divulged by focusing on the first guide 236 alone, and it will be understood that those discussions may be equivalently applicable to the second guide 236′ as well. Wherever applicable references to the second guide 236′ may also be used.
The first guide 236 includes an integrally and contiguously extending extension portion 240. The extension portion 240 extends partly from each of the first lateral face 200, the forward face 190, and the rearward face 192, at the first end portion 194. As visualized by viewing
The extension portion 240 includes a cavity 246. The cavity 246 is configured to accommodate the first valve rotator 128 and guide the valve bridge 136 with the first valve rotator 128 during each opening and closing of the first valve 124 relative to the engine 102 (see direction, C). In some implementations, the cavity 246 is circular shaped, and the first valve rotator 128 is substantially co-axially accommodated within the cavity 246. When viewing
In some implementations, a height H1 of the peripheral edge 248 may be based upon a height H2 of the outer circular edge 232. In another example, if the engine 102 is generally subject to relatively increased vibrations, a peripheral edge with a relatively increased height H1 may be applicable. This is because a heightened peripheral edge 248 may have a higher degree of contact surface area or positive contact surface with the outer circular edge 232 of the first valve rotator 128, thus restraining a disengagement between the first valve rotator 128 and the valve bridge 136. In some implementations, the heights H1 and H2 may be substantially same.
Moreover, the cavity 246 and the recess (first seat 206) define a stepped configuration (see
In some implementations, exhaust valves, such as the first exhaust valve 124a, of the valve system 104 may also work in conjunction with a valve bridge 136′, similar to the valve bridge 136. In some implementations, a gas exchange within each cylinder of the engine 102, such as cylinder 108, may be facilitated with one or more of such valve bridges, as well.
During operation, as fuel is combusted in the engine 102, the piston 114 executes a linear stroke which is translated to a rotary movement of the crankshaft 120. Since the crankshaft 120 is coupled to the camshaft 130, the camshaft 130 rotates according to a rotation of the crankshaft 120 and angularly varies the cam lobe 132 to move the cam roller portion 158 of the rocker arm 134. Consequently, the opposite end 168 of the rocker arm 134 oscillates inversely in relation to a movement (or an oscillation) of the cam roller portion 158. Since the rocker arm 134 is slidably abutted to the valve bridge 136, the reversed oscillation is translated to a reciprocatory movement (see direction, C) of the valve bridge 136 and the valves 124, 124′, relative to the engine 102. In some implementations, a single articulating motion (or stroke) imparted to the valve bridge 136 by the rocker arm 134 at the tappet head 176 may result in a lifting (open position) of the valves 124, 124′ by about the same amount and at about the same timing. At every such instance of the rocker arm 134 transmitting motion to the valve bridge 136, the elephant foot 172 may slide against the tappet head 176, causing a dynamic change (see direction, D) to a point of contact 250 between the two components. Such dynamic change to the point of contact 250 may in turn lead to the distribution of unequal forces in the valve bridge 136.
To counter conditions, such as a tilt of the valve bridge 136, arising out of unequal force distribution, the cavity 246 may be configured to accommodate and guide the valve bridge 136 with the first valve rotator 128 during each opening and closing (see direction, C) of the first valve 124 relative to the engine 102. In either of the closed position or the open position, since the peripheral edge 248 of the first guide 236 encompasses the outer circular edge 232 of the first valve rotator 128, and since the first valve rotator 128 may be retained within the cavity 246 by the relatively strong positive contact of the cavity 246, a dislodgement and a consequent tilt of the valve bridge 136 may be well avoided. As a result, conditions such as a dropped valve, that may otherwise damage the engine 102, is well avoided.
In some implementations, the recess of the first seat 206 may be absent, and the end 210 of the first valve stem 152 may be unable to be extended or inserted into the first seat 206 to retain the valve bridge 136. Instead, the end 210 may be abutted against a flattened surface, flush in relation to a surrounding surface of the base 186, as aforementioned. In such a case, the extension portion 240 may solely retain and guide the first valve rotator 128 against a dislodgement from the valve bridge 136.
It should be understood that the above description is intended for illustrative purposes only and is not intended to limit the scope of the present disclosure in any way. Thus, one skilled in the art will appreciate that other aspects of the disclosure may be obtained from a study of the drawings, the disclosure, and the appended claim.
