Embodiments of the subject matter disclosed herein relate to a V type engine, engine components, and an engine system, for example.
Diesel and gasoline V-engines utilize intake and exhaust valves to control intake air entering engine cylinders for combustion and exhaust gases exiting the engine cylinders after combustion. The timing of opening and closing of these valves may affect the amount of air available for combustion and the power output and NOx production of the engine. As such, intake and exhaust valve events may be optimized to reduce emissions and improve fuel consumption. However, if valve timing is optimized for high loads, the acceleration performance of the engine at low loads may suffer.
In one example, various hydraulic and electrical variable valve timing mechanisms may provide variable valve timing at different engine operating conditions. However, these systems may require complicated control mechanisms and comprise many components.
In one embodiment, an engine method (e.g., method for controlling an engine) comprises pivoting a first cam follower for a first cylinder of a first bank and a second cam follower for a second cylinder of a second bank about a rotatable pivot shaft, driving the first cam follower and the second cam follower with a camshaft to operate a respective first valve of the first cylinder and a second valve of the second cylinder, and rotating the pivot shaft to vary a valve timing of the first cylinder and the second cylinder.
In one example, a pivot shaft coupled to a series of cam followers may be used to adjust the timing of when a lobe of a camshaft contacts a cam follower and actuates an intake or exhaust valve coupled through a pushrod to the cam follower, thereby adjusting the timing of the valve. By rotating the pivot shaft, valve timing on a left and right bank of cylinders of the V-engine may be adjusted. In this way, timing of the intake and/or exhaust valves of the V-engine may be adjusted at different engine operating conditions with the pivot shaft and a single, central camshaft.
In another embodiment, a system for an engine comprises a V-engine with a single, central camshaft, a rotatable pivot shaft offset from the camshaft, a first group of cam followers driven by the camshaft and pivoted about the rotatable pivot shaft, and a first group of pushrods operative to drive valves of a first cylinder group. The first group of pushrods is operatively coupled with the first group of cam followers. The system further comprises a second group of cam followers driven by the camshaft and pivoted about the rotatable pivot shaft, and a second group of pushrods operative to drive valves of a second cylinder group. The second group of pushrods is operatively coupled with the second group of cam followers.
In this way, valve timing of intake and exhaust valves on a first bank of cylinders and a second bank of cylinders may be adjusted with the same pivot shaft and a single camshaft. Further, by rotating the pivot shaft during different engine operating conditions, valve timing may be optimized for increased engine performance.
It should be understood that the brief description above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.
The present invention will be better understood from reading the following description of non-limiting embodiments, with reference to the attached drawings, wherein below:
The following description relates to various embodiments of a cam follower system to vary valve timing in a V-engine. The cam follower system may include a single camshaft centralized between two banks of cylinders in the V-engine. For each intake and exhaust valve of each cylinder, a cam follower or rocker may be coupled to the valve. A cam follower may be driven by the camshaft, actuating the valve as a cam lobe on the camshaft contacts one end of the cam follower. Each cam follower may be coupled at another end to an eccentric pivot point on a pivot shaft. The pivot points may be offset from a main axis of the pivot shaft. As such, rotating the pivot shaft may translate the position of the pivot points, thereby shifting the position of the cam followers and the point at which they contact the camshaft. This shifting the position of the cam followers may cause valve timing to be adjusted. Depending on the amount of pivot points and the location of the pivot points relative to the pivot shaft, the timing of the intake and/or exhaust valves may be adjusted by rotating a single pivot shaft. In one example, a controller may adjust the pivot shaft to adjust valve timing based on engine operating conditions. For example, the pivot shaft may be adjusted to advance intake valve timing during high engine loads and then adjusted again to retard intake valve timing during low engine loads. In this way, valve timing may be adjusted to increase engine efficiency and reduce emissions.
Engine 104 is a Vee engine (e.g., V-engine). In the example embodiment depicted in
As depicted in
Thus, the engine includes a first, donor cylinder group configured to route exhaust to the intake and/or atmosphere, and a second, non-donor cylinder group configured to route exhaust only to atmosphere. The non-donor cylinder exhaust manifold 117 and donor cylinder exhaust manifold 119 are maintained separately from each other. Other than the cross-over passage controlled by a first valve 164, the manifolds do not include common passageways enabling communication between the non-donor cylinder manifold and the donor cylinder manifold. However, both the first, donor cylinder group and second, non-donor cylinder group receive the same intake air via the intake manifold 115, and are subject to equal intake manifold pressure.
In the example embodiment shown in
Further, the EGR system 160 includes a first valve 164 disposed between the exhaust passage 116 and the EGR passage 162. The second valve 170 may be an on/off valve controlled by the control unit 180 (for turning the flow of EGR on or off), or it may control a variable amount of EGR, for example. In some examples, the first valve 164 may be actuated such that an EGR amount is reduced (exhaust gas flows from the EGR passage 162 to the exhaust passage 116). In other examples, the first valve 164 may be actuated such that the EGR amount is increased (e.g., exhaust gas flows from the exhaust passage 116 to the EGR passage 162). In some embodiments, the EGR system 160 may include a plurality of EGR valves or other flow control elements to control the amount of EGR.
In such a configuration, the first valve 164 is operable to route exhaust from the donor cylinders to the exhaust passage 116 of the engine 104 and the second valve 170 is operable to route exhaust from the donor cylinders to the intake passage 114 of the engine 104. As such, the first valve 164 may be referred to as an exhaust valve, while the second valve 170 may be referred to as an EGR valve. In the example embodiment shown in
As shown in
As depicted in
The engine system 100 further includes an exhaust treatment system 130 coupled in the exhaust passage in order to reduce regulated emissions. As depicted in
The engine system 100 further includes the control unit 180, which is provided and configured to control various components related to the engine system 100. In one example, the control unit 180 includes a computer control system. The control unit 180 further includes non-transitory, computer readable storage media including code for enabling on-board monitoring and control of engine operation. The control unit 180, while overseeing control and management of the engine system 100, may be configured to receive signals from a variety of engine sensors, as further elaborated herein, in order to determine operating parameters and operating conditions, and correspondingly adjust various engine actuators to control operation of the engine system 100. For example, the control unit 180 may receive signals from various engine sensors including, but not limited to, engine speed, engine load, boost pressure, ambient pressure, exhaust temperature, exhaust pressure, etc. Correspondingly, the control unit 180 may control the engine system 100 by sending commands to various components such as traction motors, alternator, cylinder valves, throttle, heat exchangers, wastegates or other valves or flow control elements, etc.
The first piston 216 and the second piston 224 are coupled to the crankshaft 212 so that reciprocating motion of the pistons is translated into rotational motion of the crankshaft around an axis of rotation 210. In some embodiments, the engine may be a four-stroke engine in which each of the cylinders fires in a firing order during two revolutions of the crankshaft 212. In other embodiments, the engine may be a two-stroke engine in which each of the cylinders fires in a firing order during one revolution of the crankshaft 212.
The first intake valve 218 controls the intake air entering the first cylinder 214 from the intake manifold 115 (shown in
The timing of the intake and/or exhaust valves is controlled by a cam follower system 240. The cam follower system 240 includes a camshaft 242 driven by the rotation of the crankshaft 212 around the axis of rotation 210. The camshaft 242 is rotatable around an axis of rotation 236 of the camshaft. In embodiments, the camshaft 242 is the single, or only, camshaft for engine 104, and may be centrally located between the left bank 232 and the right bank 234 on the vertical axis 230. The camshaft 242 extends in a lateral direction along the lateral axis 206, along the length of the cylinder banks. A plurality of cam lobes may be disposed along the length of the camshaft 242, such as a first cam lobe 244 and a second cam lobe 280. In the example shown in
The cam follower system 240 further includes a rotatable pivot shaft 246 offset from the camshaft 242. The pivot shaft 246 extends along the lateral axis 206 along the bank of cylinders. An axis of rotation 238 of the pivot shaft 246 is located vertically above, with respect to the vertical axis 204, the axis of rotation 236 of the camshaft 242, both axes laterally positioned (e.g., axes positioned along the lateral axis 206) in the V-engine.
One embodiment of a pivot shaft 246 is shown in
In another embodiment, the pivot shaft 246 may have a third group of eccentric pivot points and a fourth group of eccentric pivot points, each group of pivot points offset from the axis of rotation 238 of the pivot shaft 246. Each group of pivot points may control the valve timing of a different set of valves. For example, a position of the first group of pivot points may control the timing of a group of intake valves on the left bank while a position of the second group of pivot points may control the timing of a group of intake valves on the right bank. Further, a position of the third group of pivot points may control the timing of a group of exhaust valves on the left bank and a position of the fourth group of pivot points may control the timing of a group of exhaust valves on the right bank. It should be understood that the pivot shaft 246 may have a number of combinations of eccentric pivot points offset in different directions and by different amounts from the axis of rotation 238 of the pivot shaft 246. In this way, the timing of the intake and exhaust valves may be adjusted based on engine operating requirements.
Engine 104 may comprise a plurality of cam followers; each cam follower drives a pushrod coupled through a rocker to either an intake or exhaust valve. As such, movement of each cam follower may drive the actuation of the cam follower's respective valve. Each cam follower of engine 104 may be coupled to one segment or pivot point on the pivot shaft 246. For example, the cam follower may be coupled to a segment of the main shaft 302, or an offset segment of the pivot shaft 246 such as first pivot point 304 or second pivot point 308. One end of the cam follower may be coupled around a pivot point or shaft segment such that the cam follower is rotatable around the pivot point. In one example, the cam follower may comprise a ring at a first end of the cam follower, the ring encircling the pivot point. An outer circumference of the pivot point and an inner circumference of the ring of the cam follower may be separated by an amount of space in order to allow free rotation of the ring of the cam follower around the pivot point.
Specifically, as shown in
The second pivot point 308 on the pivot shaft 246 is coupled to a first end of a second cam follower 260. The second cam follower 260 is coupled at a second end of the second cam follower 260 to a second roller 262. The second roller 262 contacts the camshaft 242 at a second contact point 264. The second roller 262 is further coupled to a first end of a second pushrod 266. The second pushrod 266 is coupled at a second end to a second rocker 268. The second rocker 268 is further coupled to the second intake valve 226.
As discussed above, in one embodiment, the pivot shaft 246 may have a third group of eccentric pivot points and a fourth group of eccentric pivot points. In this example, the third pivot points (not shown) may be coupled to a third cam follower (not shown), wherein the third cam follower is coupled at a second end of the third cam follower to a third roller (not shown). Referring to
Further, a fourth pivot point (not shown) may be coupled to a fourth cam follower (not shown), wherein the fourth cam follower is coupled at a second end of the fourth cam follower to a fourth roller (not shown). Referring to
In this system, the first group of pushrods may drive a first group of intake valves and a first group of exhaust valves of the first cylinder group and the second group of pushrods may drive a second group of intake valves and a second group of exhaust valves of the second cylinder group. Further, the cam followers may pivot about pivot points on the rotatable pivot shaft, the pivot points eccentrically positioned with respect to the axis of rotation of the rotatable pivot shaft.
In one example, the pivot shaft may have a first group of eccentric pivot points offset from the axis of rotation of the pivot shaft and a second group of eccentric pivot points offset from the axis of rotation of the pivot shaft, the first group of cam followers being rotatable about the first group of eccentric pivot points, and the second group of cam followers being rotatable about the second group of eccentric pivot points. The first group of eccentric pivot points may be coupled through the first group of pushrods to a first group of intake valves of the first cylinder group and the second group of eccentric pivot points may be coupled through the second group of pushrods to a second group of intake valve of the second cylinder group.
In some examples, the pivot shaft may have a third group of eccentric pivot points driving a first group of exhaust valves of the first cylinder group and a fourth group of eccentric pivot points driving a second group of exhaust valves of the second cylinder group.
In an alternate embodiment of engine 104, an optional second pivot shaft may be included. As shown in
In some embodiments of engine system 100, a control unit 180 (e.g., controller) may be configured to vary a valve timing of the first cylinder and the second cylinder by rotating the pivot shaft. Rotating the pivot shaft may include translating the first pivot point and the second pivot point, thereby shifting the first cam follower and the second cam follower and their respective contact points on the camshaft. As such, the direction and/or degree of rotation of the pivot shaft may determine whether valve timing is advanced, retarded, or neutral. Further details on adjusting the pivot shaft to adjust valve timing are presented below with reference to
As introduced above, intake and exhaust valves control intake air entering engine cylinders for combustion and exhaust gas exiting the engine cylinders after combustion, respectively. The timing of opening and closing these valves may affect the amount of air available for combustion and the power output and NOx production of the engine. As such, intake and exhaust valve events may be optimized to reduce emissions and improve fuel consumption. For example, by closing the intake valve at or before bottom dead center of the piston stroke, the air capture in the cylinder and the effective compression ratio may be reduced, thereby reducing NOx production and increasing engine efficiency at high engine power levels. Bottom dead center may be defined as the point in a piston stroke when the piston is at the bottom of the cylinder and closest to the crankshaft. However, if valve timing is optimized in this way at high engine loads, the acceleration performance of the engine at low engine loads may suffer. For example, when the intake valve timing is advanced such that the valve closes at or before bottom dead center during low engine loads, the engine may not get enough intake air. Boost produced by the turbocharger of the engine may compensate for decreased air capture. However, this may result in decreased turbocharger air flow and low air fuel ratio, thereby reducing acceleration at low engine loads. Thus, during low engine load conditions, retarding intake valve timing may increase engine performance. By adjusting the timing (e.g., opening and closing) of intake and/or exhaust valves based on engine operating conditions such as engine load, engine efficiency may be increased.
In one example, the pivot shaft described above with reference to
As shown in
The pivot shaft 246 may rotate the first pivot point 304 into a first position 402 to advance valve timing. In the first position 402, the pivot point 304 is to the right of the vertical axis 230 and above the horizontal axis 416. A line of contact 418 shows that the first roller 250 contacts the camshaft 242 at a point which is closer to the vertical axis 230 than the horizontal axis 414 of the camshaft 242. As such, as the camshaft 242 rotates in the direction shown by arrow 408, a first cam lobe 244 will contact and move the first roller 250 sooner in the camshaft rotation than a neutral or standard position (shown at position 404, discussed below). This may cause a first pushrod 254, attached to the first roller 250, to actuate a first valve (intake or exhaust) earlier than the standard set timing, thereby advancing valve timing.
In one example, the pivot shaft 246 may rotate in one direction, in the direction shown by arrow 410. In another example, the pivot shaft 246 may rotate in the direction shown by arrow 410 and a direction opposite the direction shown by arrow 410. As shown in
In the second position 404, the first pivot point 304 is below the horizontal axis 416 and to the right of the vertical axis 230. This shifts the first cam follower 248, thereby moving the first roller 250 downward and closer to the horizontal axis 414 of the camshaft 242. As shown by a line of contact 420, the first roller 250 contacts the camshaft 242 at a point between the vertical axis 230 and the horizontal axis 414. As the camshaft 242 rotates in the direction shown by arrow 408, the first cam lobe 244 may contact the first roller 250 later in the camshaft rotation than in the first position 402. As a result, valve timing may be neutral (e.g., neither advanced nor retarded) when the first pivot point 304 is in the second position 404.
The pivot shaft 246 rotates in the direction shown by arrow 412 to translate the first pivot point 304 from the second position 404 (e.g., neutral position) to a third position 406 (e.g., retarded position). In the third position 406, the first pivot point 304 is to the left of the vertical axis 230 and in-line with the horizontal axis 416. This position shifts the first cam follower 248, thereby moving the first roller 250 downward and closer to the horizontal axis 414 of the camshaft 242. As shown by a line of contact 422, the first roller 250 contacts the camshaft 242 at a point closer to the horizontal axis 414 than the vertical axis 230. As the camshaft 242 rotates in the direction shown by arrow 408, the first cam lobe 244 may contact the first roller 250 later in the camshaft rotation than in the first position 402 and the second position 404. This may cause the first pushrod 254, attached to the first roller 250, to actuate the first valve (intake or exhaust) later than the standard set timing, thereby retarding valve timing.
As shown in
In
Now turning to
As shown in
The pivot shaft 246 may rotate the second pivot point 308 into a first position 502 to advance valve timing. In the first position 502, the pivot point 308 is to the right of the vertical axis 230 and in-line with the horizontal axis 416. A line of contact 518 shows that the second roller 262 contacts the camshaft 242 at a point which is closer to the horizontal axis 414 than the vertical axis 230 of the camshaft 242. As such, as the camshaft 242 rotates in the direction shown by arrow 408, a first cam lobe 244 will contact and move the second roller 262 sooner in the camshaft rotation than a neutral or standard position (shown at second position 504, discussed below). This may cause a second pushrod 266, attached to the second roller 262, to actuate a second valve (intake or exhaust) earlier than the standard set timing, thereby advancing valve timing.
In one example, the pivot shaft 246 may rotate in one direction, in the direction shown by arrow 510. In another example, the pivot shaft 246 may rotate in the direction shown by arrow 510 and a direction opposite the direction shown by arrow 510. As shown in
In the second position 504, the second pivot point 308 is below the horizontal axis 416 and to the left of the vertical axis 230. This shifts the second cam follower 260, thereby moving the second roller 262 upward and closer to the vertical axis 230 of the camshaft 242. As shown by a line of contact 520, the second roller 262 contacts the camshaft 242 at a point between the vertical axis 230 and the horizontal axis 414. As the camshaft 242 rotates in the direction shown by arrow 408, the first cam lobe 244 may contact the second roller 262 later in the camshaft rotation than in the first position 502. As a result, valve timing may be neutral (e.g., neither advanced nor retarded) when the second pivot point 308 is in the second position 504.
The pivot shaft 246 rotates in the direction shown by arrow 512 to translate the second pivot point 308 from the second position 504 (e.g., neutral position) to a third position 506 (e.g., retarded position). In the third position 506, the second pivot point 308 is to the left of the vertical axis 230 and above the horizontal axis 416. This shifts the second cam follower 260, thereby moving the second roller 262 upward and closer to the vertical axis 230 of the camshaft 242. As shown by a line of contact 522, the second roller 262 contacts the camshaft 242 at a point closer to the vertical axis 230 than the horizontal axis 414. As the camshaft 242 rotates in the direction shown by arrow 408, the first cam lobe 244 may contact the second roller 262 later in the camshaft rotation than in the first position 502 and the second position 504. This may cause the second pushrod 266, attached to the second roller 262, to actuate the second valve (intake or exhaust) later than the standard set timing, thereby retarding valve timing.
As shown in
At 604, the method determines whether there is a request to advance valve timing. A request to advance valve timing may include a request to advance intake valve timing, exhaust valve timing, or both. The request to advance valve timing may be based on engine operating conditions. For example, in response to an engine load above an upper threshold level, a request to advance valve timing of the intake valves may be generated. If there is a request to advance valve timing, the control unit may rotate the pivot shaft in a direction which moves the pivot points into the first position at 606, as described above with regard to
However, if there is not a request to advance valve timing, the method continues on to 608 to determine if there is a request to retard valve timing. A request to retard valve timing may include a request to retard intake valve timing, exhaust valve timing, or both. The request to retard valve timing may be based on engine operating conditions. For example, in response to an engine load below a lower threshold level, a request to retard valve timing of the exhaust valves may be generated. If there is a request to retard valve timing, the control unit may rotate the pivot shaft in a direction which moves the pivot points into the third position at 610, as described above with regard to
However, if there is not a request to retard valve timing, the method continues on to 612 to maintain the pivot shaft in a neutral position. Alternatively at 612, if the pivot shaft is not currently in a neutral position, the control unit may rotate the pivot shaft into the second position, as described above with regard to
In this way, a method for varying valve timing of an engine may include rotating a pivot shaft of a cam follower system. With reference to
Pivoting the first and second cam follower may include translating a first pivot point and a second pivot point on the pivot shaft away from the centerline, the first pivot point coupled to a first end of the first cam follower and the second pivot point coupled to a first end of the second cam follower. Further, translating the first pivot point includes moving a first contact point between a first roller coupled to a second end of the first cam follower and the camshaft, relative to a cam lobe on the camshaft. Similarly, translating the second pivot point includes moving a second contact point between a second roller coupled to a second end of the second cam follower and the camshaft, relative to the cam lobe on the camshaft.
In one example, the first contact point of the first cam follower may be moved towards the vertical centerline on the camshaft to advance the valve timing of the first valve and the second contact point of the second cam follower may be moved away from the vertical centerline to advance the valve timing of the second valve. In another example, the first contact point of the first cam follower may be moved away from the vertical centerline on the camshaft to retard the valve timing of the first valve and the second contact point of the second cam follower may be moved further from the vertical centerline to retard the valve timing of the second valve.
A shown above, rotating the pivot shaft causes the cam follower to shift and changes the valve timing by the same amount on both cylinder banks (e.g., right and left bank). If the intake valve timing is varied and the exhaust valve timing is fixed, only the intake valve pivot points may be eccentric (e.g., offset from axis of rotation of the pivot shaft). If both the corresponding intake and exhaust valve pivot points are eccentric then both valve timings may vary as the pivot shaft rotates. In one example, both the intake and exhaust timing may advance or retard together. In another example, one of the intake or exhaust timing may advance while the other may retard, depending on the phase or position of the eccentric pivot points in the pivot shaft.
In this way, a cam follower system may enable the adjustment of a valve timing of intake and/or exhaust valves on both a right and left bank of cylinders in a V-engine. The cam follower system may include a single camshaft centralized between the two banks of cylinders and a cam follower coupled through a pushrod to each intake and exhaust valve of each cylinder. The cam followers may be driven by the camshaft, actuating the valves as a cam lobe on the camshaft contacts one end of the cam follower. Each cam follower may be coupled at another end to an eccentric pivot point on a pivot shaft. The pivot points may be offset from a main axis of the pivot shaft. As such, rotating the pivot shaft may translate the position of the pivot points, thereby shifting the position of the cam followers and the point at which they contact the camshaft. This shifting the position of the cam followers may adjust the valve timing. Depending on the amount of pivot points and the location of the pivot points relative to the pivot shaft, the timing of the intake and/or exhaust valves may be adjusted by rotating a single pivot shaft. In one example, a controller may adjust the pivot shaft to adjust valve timing based on engine operating conditions such as engine load. In this way, valve timing may be adjusted based on engine load to increase engine efficiency and reduce emissions.
As used herein, an element or step recited in the singular and proceeded with the word “a” or “an” should be understood as not excluding plural of said elements or steps, unless such exclusion is explicitly stated. Furthermore, references to “one embodiment” of the present invention are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features. Moreover, unless explicitly stated to the contrary, embodiments “comprising,” “including,” or “having” an element or a plurality of elements having a particular property may include additional such elements not having that property. The terms “including” and “in which” are used as the plain-language equivalents of the respective terms “comprising” and “wherein.” Moreover, the terms “first,” “second,” and “third,” etc. are used merely as labels, and are not intended to impose numerical requirements or a particular positional order on their objects.
This written description uses examples to disclose the invention, including the best mode, and also to enable a person of ordinary skill in the relevant art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those of ordinary skill in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.
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