Patent Application
20110139099
The invention relates to variable valve lift systems for internal combustion engines; more particularly, to a system for variable valve lift of dual intake valves; and most particularly, to such a system wherein the valvetrain of one of the dual intake valves includes means for multi-lift positioning of that valve and the valvetrain of the other valve includes means for lost motion valve deactivation of that valve.
Variable valve lift systems are known in the engine arts. See, for example, the systems disclosed in U.S. Pat. No. 6,668,779 and US Patent Application Publication No. 2008/0072855 published Mar. 27, 2008, the disclosures of which are both expressly incorporated herein by reference. Such systems typically incorporate a two-step roller finger follower to selectively transmit motion of either a high-lift cam lobe or a low-lift cam lobe of the engine's camshaft to an intake valve.
Valve deactivation systems for selectively activating and deactivating valves are also known. See, for example, U.S. Pat. No. 6,321,704 that discloses a deactivation hydraulic lash adjuster, and U.S. Pat. No. 7,093,572 that discloses a deactivation roller finger follower, the disclosures of which are both expressly incorporated herein by reference. Each of these deactivation systems prevents the rotary motion of a camshaft lobe from being translated into reciprocal motion of the associated valve stem by absorbing the equivalent motion within itself (“lost motion”). Thus the valve is “deactivated” and prevented from opening on schedule.
Customers' expectations of better engine performance and vehicle drivability, ever more stringent governmental regulations regarding engine emissions, and a mutual desire for higher fuel economy are increasingly at odds. Compromises inherent with fixed valve lift and event timing in conventional valvetrains have prompted engine designers to consider variable valve lift systems for more flexible air flow control optimized for each engine load and speed condition, and some variable valve lift systems have now been introduced on production engines. However, addressing critical engineering challenges concerning turbulence (swirl or tumble) enhancement in variable valve lift engines currently requires combustion chamber masking.
Engine combustion strategies in prior variable valve lift systems allow the intake valve to have discrete operational states known as high-lift and low-lift. In the high-lift operational state, the intake valve is allowed to reach a maximum open position, while in the low-lift operational state, the intake valve is only allowed to reach an open position intermediate of the closed and maximum open positions. However, variable valve lift mechanisms on dual intake valve engines have thus far been limited to providing the same lift on both intake valves of each cylinder, which cannot provide any in-cylinder air flow turbulence enhancement.
What is needed in the art is an internal combustion engine variable valve lift system wherein in-cylinder turbulence is enhanced during variable valve lift operation. Therefore, it is a principal object of the present invention to provide increased in-cylinder turbulence during variable valve lift operation of an internal combustion engine.
Briefly described, the present invention provides a dual intake valve system for an internal combustion engine having a variable valve lift system for both intake valves of one or more engine cylinders. In each such cylinder, the valvetrain of one of the intake valvetrains includes a valve deactivation device and the valvetrain of the other intake valve includes a variable valve lift device such as a two-step roller finger follower.
The intake valvetrain including the valve deactivation device may include a deactivation hydraulic lash adjuster or a deactivation roller finger follower. Optionally, the intake valvetrain including the valve deactivation device can also include a variable valve lift device such as a two-step roller finger follower.
To improve in-cylinder air flow turbulence, each intake valve can be selectively operated at a different lift height, thereby resulting in a higher flow rate of intake air or air/fuel mixture through one intake valve which generates strong swirl by unbalanced flow. In one example of operating dual intake valves of an engine cylinder at different lift heights, one intake valve is operated at high-lift while the other intake valve is operated at low-lift. In another example of operating dual intake valves at different lift heights, one intake valve is operated at high-lift while the other intake valve is deactivated. In yet another example of operating dual intake valves at different lift heights, one intake valve is operated at low-lift while the other intake valve is deactivated.
Thus, the present invention provides a system for variable actuation of first and second intake valves of a cylinder in an internal combustion engine having a camshaft, including a selectively locked two-step actuation device operatively engaging the camshaft and the first intake valve, and a selectively locked valve deactivation device operatively engaging the camshaft and the second intake valve. The two-step actuation device has a high-lift operational state in which the first intake valve reaches a maximum lift open position and a low-lift operational state in which the first intake valve reaches only to an open lift position intermediate a closed position and its maximum lift open position. Selective locking of the two-step actuation device places it in one of its high-lift and low-lift operational states, and selective unlocking of the two-step actuation device places it in the other of its high-lift and low-lift operational states. The valve deactivation device has an activated state of operation in which the second intake valve reaches an open position and a deactivated state of operation in which the second intake valve remains in a closed position. Selective locking of the valve deactivation device places it in one of its activated and deactivated states of operation, and selective unlocking of the deactivation device places it in the other of its activated and deactivated states of operation. The present invention also provides an internal combustion engine having such a system.
The present invention further provides a method of introducing a mixture charge into a combustion chamber of an engine cylinder having a first intake valve and a second intake valve for introducing the mixture charge into the combustion chamber, including: selecting a first valve lift position for the first intake valve that is only one of a high-lift position corresponding to a high-lift operational state and a low-lift position corresponding to a low-lift operational state; opening the first intake valve to the selected first lift position; selecting a second valve state of operation that is only one of an activated state of operation corresponding to the second intake valve reaching an open position and a deactivated state of operation corresponding to the second intake valve remaining closed; and operating at the selected second valve state of operation.
Further features and advantages of the invention will appear more clearly on a reading of the following detailed description of preferred embodiments of the invention, which are given by way of non-limiting example only and with reference to the accompanying drawings.
This invention will be further described with reference to the accompanying drawings in which:
In accordance with a first preferred embodiment of the invention,
In the first preferred embodiment, first valve actuation means 28a includes first two-step actuation device 29a for selectively applying high-lift and low-lift to first intake valve 22a. The high-lift operational state is characterized by permitting first intake valve 22a to open to a maximum position while low-lift is characterized by permitting first intake valve 22a to open only to a position intermediate of the high-lift and valve closed positions. In this embodiment, first two-step actuation device 29a takes the form of a two-step rocker arm, and more specifically first two-step roller finger follower 30a.
First two-step roller finger follower 30a includes first high-lift follower 32a to engage and receive input from first high-lift lobe 34a of engine camshaft 26. First two-step roller finger follower 30a also includes first low-lift rollers 38a to selectively engage and receive input from first low-lift lobes 36a of engine camshaft 26.
When first two-step roller finger follower 30a is selectively in a locked state of operation, or its high-lift operational state, motion from first high-lift lobe 34a is transmitted to first intake valve 22a through first two-step roller finger follower 30a by way of first high-lift follower 32a, consequently pivoting first two-step roller finger follower 30a about first hydraulic lash adjuster 31a, thereby causing first intake valve 22a to open to its maximum valve opening position. In this locked state of operation, first low-lift lobes 36a do not transmit valve lifting motion to first low-lift rollers 38a.
When first two-step roller finger follower 30a is selectively in an unlocked state of operation, or its low-lift operational state, motion from first high-lift lobe 34a is no longer transmitted to first intake valve 22a through first two-step roller finger follower 30a by way of first high-lift follower 32a. In the unlocked state of operation, first high-lift lobe 34a is still permitted to transmit motion to first high-lift follower 32a, but the motion is “lost” and not transmitted to first intake valve 22a by allowing first high-lift follower 32a to pivot about first two-step shaft 40a. In its unlocked state of engagement, first high-lift follower 32a maintains contact with first high-lift lobe 34a by using a spring (not shown) urging first high-lift follower 32a into contact with first high-lift lobe 34a. When first high-lift follower 32a pivots about first two-step shaft 40a, motion from first low-lift lobes 36a is transmitted to first intake valve 22a through first two-step roller finger follower 30a by way of first low-lift rollers 38a, consequently pivoting first two-step roller finger follower 30a about first hydraulic lash adjuster 31a, thereby causing first intake valve 22a to open to only a low-lift position which is intermediate of the closed and maximum open positions.
First two-step roller finger follower 30a is selectively switched between its locked and unlocked states of operation by selectively applying pressurized oil to a latch mechanism (not shown) and selectively relieving the pressurized oil from the latch mechanism. The latch mechanism is locked when pressurized oil is applied thereto, thereby preventing first high-lift follower 32a from rotating about first two-step shaft 40a. The latch mechanism is unlocked when the pressurized oil is relieved therefrom, thereby causing first high-lift follower 32a to pivot about first two-step shaft 40a.
In the first preferred embodiment, second valve actuation means 28b includes valve deactivation device 41 which takes the form of a deactivation rocker arm, and more specifically, deactivation roller finger follower 42. Valve deactivation device 41 selectively activates and deactivates second intake valve 22b. Deactivation roller finger follower 42 includes high-lift roller 44 that engages and receives input from second high-lift lobe 34b of engine camshaft 26. Deactivation roller finger follower 42 also includes null pads 46 that follow null lobes 48 of engine camshaft 26. When deactivation roller finger follower 42 is selectively in a locked, or activated state of operation, motion from second high-lift lobe 34b is transmitted through deactivation roller finger follower 42 by way of high-lift roller 44, consequently pivoting deactivation roller finger follower 42 about second hydraulic lash adjuster 31b, thereby causing second intake valve 22b to open to a maximum valve opening position. In this locked state of operation, null lobes 48 are in contact with null pads 46 only when second high-lift lobe 34b is not providing lifting motion to second intake valve 22b.
Deactivation roller finger follower 42 is selectively switched between its locked and unlocked states of operation by selectively applying pressurized oil to a latch mechanism (not shown) and selectively relieving the pressurized oil from the latch mechanism. The latch mechanism is locked when pressurized oil is applied thereto, thereby preventing high-lift roller 44 from pivoting about deactivation shaft 50. The latch mechanism is unlocked when the pressurized oil is relieved therefrom, thereby allowing high-lift roller 44 to pivot about deactivation shaft 50.
When deactivation roller finger follower 42 is selectively in an unlocked, or deactivated state of operation, second high-lift lobe 34b is still permitted to transmit motion to high-lift roller 44, but the motion is “lost” by allowing high-lift roller 44 to pivot about deactivation shaft 50. High-lift roller 44 maintains contact with second high-lift lobe 34b by a spring (not shown) urging high-lift roller 44 into contact with second high-lift lobe 34b.
When high-lift roller 44 pivots about deactivation shaft 50, null lobes 48 are allowed to maintain contact with null pads 46 for the entire rotation of engine camshaft 26. Null lobes 48 are circular, and sized such that motion is not transmitted to second intake valve 22b as engine camshaft 26 rotates, consequently leaving second intake valve 22b in a closed position.
In accordance with a second preferred embodiment of the invention,
When deactivation hydraulic lash adjuster 54 is selectively in a locked, or activated state of operation, motion from second high-lift lobe 34b is transmitted through conventional roller finger follower 52, consequently pivoting conventional roller finger follower 52 about deactivation hydraulic lash adjuster 54, thereby causing second intake valve 22b to open to a maximum valve opening position. When deactivation hydraulic lash adjuster 54 is selectively in an unlocked, or deactivated state of operation, second high-lift lobe 34b acting on conventional roller finger follower 52 causes deactivation hydraulic lash adjuster 54 to compress, thereby allowing second intake valve 22b to remain in its closed position under the force of its valve spring regardless of the rotational position of engine camshaft 26.
Deactivation hydraulic lash adjuster 54 is selectively switched between its locked and unlocked states of operation by selectively applying pressurized oil to a latch mechanism (not shown) and selectively relieving the pressurized oil from the latch mechanism. The latch mechanism is unlocked when pressurized oil is applied thereto, thereby allowing deactivation hydraulic lash adjuster 54 to compress. The latch mechanism is locked when the pressurized oil is relieved therefrom, thereby preventing deactivation hydraulic lash 54 from compressing.
In accordance with a third preferred embodiment of the invention,
When second two-step roller finger follower 30b is selectively in a locked state of operation, or its high-lift operational state, and valve deactivation device 41 is simultaneously in a locked, or activated state of operation, motion from second high-lift lobe 34b is transmitted to second intake valve 22b through second two-step roller finger follower 30b by way of second high-lift follower 32b, consequently pivoting second two-step roller finger follower 30b about deactivation hydraulic lash adjuster 54, thereby causing second intake valve 22b to open to a maximum valve opening position. In the locked state of operation, second low-lift lobes 36b do not transmit valve lifting motion to second low-lift rollers 38b.
When second two-step roller finger follower 30b is selectively in an unlocked state of operation, or its low-lift operational state, and valve deactivation device 41 is simultaneously in a locked, or activated state of operation, motion from second high-lift lobe 34b is no longer transmitted to second intake valve 22b through second two-step roller finger follower 30b by way of second high-lift follower 32b. In the unlocked state of operation, second high-lift lobe 34b is still permitted to transmit motion to second high-lift follower 32b, but the motion is “lost” by allowing second high-lift follower 32b to pivot about second two-step shaft 40b. Second high-lift follower 32b maintains contact with second high-lift lobe 34b by a spring (not shown) urging second high-lift follower 32b into contact with second high-lift lobe 34b. When second high-lift follower 32b pivots about second two-step shaft 40b, motion from second low-lift lobes 36b is transmitted to second intake valve 22b through second two-step roller finger follower 30b by way of second low-lift rollers 38b, consequently pivoting second two-step roller finger follower 30b about deactivation hydraulic lash adjuster 54 and causing second intake valve 22b to open only to a position intermediate of the closed and maximum opened positions.
Second two-step roller finger follower 30b is selectively switched between its locked and unlocked states of operation by selectively applying pressurized oil to a latch mechanism (not shown) and selectively relieving the pressurized oil from the latch mechanism. The latch mechanism is locked when pressurized oil is applied thereto, thereby preventing second high-lift follower 32b from rotating about second two-step shaft 40b. The latch mechanism is unlocked when the pressurized oil is relieved therefrom, thereby causing second high-lift follower 32b to pivot about second two-step shaft 40b.
In order to achieve the benefit offered by including first two-step actuation device 29a and valve deactivation device 41 as described in each of the three aforementioned embodiments, the ability to selectively choose between high-lift and low-lift operation of first two-step actuation device 29a is independent of the ability to selectively choose between activation and deactivation operation of valve deactivation device 41. Additionally, in the third aforementioned embodiment, the ability to selectively choose between high-lift and low-lift operation of second two-step actuation device 29b is independent of both the ability to selectively choose between high-lift and low-lift operation of first two-step device 29a and the ability to selectively choose between activation and deactivation operation of valve deactivation device 41. The ability to independently select the operation state of each of these devices allows first and second intake valves 22a, 22b to be operated at different amounts of lift with respect to one another in order to generate in-cylinder air flow turbulence.
The differences in lift height are illustrated in
Although not illustrated, one of ordinary skill in the art will now recognize and appreciate that other valve lift combinations can be achieved in accordance with the present invention. For example, first intake valve 22a may be in a high-lift operational state while second intake valve 22b is simultaneously in a high-lift operational state; first intake valve 22a may be in a low-lift operational state while second intake valve 22b is simultaneously in a low-lift operational state; and first intake valve 22a valve may be in a high-lift operational state while second intake valve 22b is simultaneously in the low-lift operational state.
Although not illustrated, one of ordinary skill in the art will now also recognize and appreciate that a valve deactivation device could also be included with the valvetrain for first intake valve 22a. Including a valve deactivation device with the valvetrain for first intake valve 22a allows for further lift combinations including maintaining both intake valves 22a, 22b in the closed position for cylinder deactivation.
Although not illustrated, one of ordinary skill in the art will now also recognize and appreciated that further lift combinations can be achieved by providing engine camshaft 26 with first high-lift lobe 34a having a different profile than second high-lift lobe 34b. Similarly, further lift combinations can be achieved by providing engine camshaft 26 with first low-lift lobes 36a having a different profile than second low lift lobes 36b.
While the preferred variable valve actuation system embodiments have been described with intake valvetrains commonly known as Type 2 valvetrain, it is to be understood that this invention is similarly applicable to variable valve actuation systems with intake valvetrains of other configurations. Type 2 valvetrains are configured to include a camshaft which provides input to a rocker arm/roller finger follower at a point intermediate of first and second ends of the rocker arm/roller finger follower. The first end of the rocker arm/roller finger follower pivots about a hydraulic lash adjuster while the second end of the rocker arm/roller finger follower provides input to an intake valve.
One alternative valve train configuration that may be used includes a camshaft which provides input to a valve lifter which is placed between the camshaft and an intake valve. This valvetrain configuration is commonly known as Type 1 valvetrain, or direct acting valvetrain.
A second alternative valve train configuration that may be used includes a camshaft that provides input to one end of a rocker arm/roller finger follower while the other end of the rocker arm/roller finger follower provides input to an intake valve. This valvetrain configuration is commonly known as Type 3 valvetrain.
A third alternative valvetrain configuration that may be used includes a camshaft that provides input to a valve lifter which is placed between the camshaft and one end of a rocker arm/roller finger follower while the other end of the rocker arm/roller finger follower provides input to an intake valve. This valvetrain configuration is commonly known as Type 4 valvetrain.
A forth alternative valvetrain configuration that may be used includes a camshaft that provides input to a valve lifter and a push rod which are placed between the camshaft and one end of a rocker arm while the other end of the rocker arm provides input to an intake valve. This valvetrain configuration is commonly known as Type 5 valvetrain, or push rod valvetrain.
While the preferred variable valve actuation system embodiments have been described with two-step actuation devices 29a, 29b, it is to be understood that this invention is similarly applicable to other multi-step actuation devices such as three or more step actuation devices which are known in the valvetrain art. It is to be understood that a two-step actuation device encompasses these other multi-step actuation devices.
While the preferred variable valve actuation system embodiments have been describe with first and second two-step roller finger followers 30a and 30b, deactivation roller finger follower 42, and deactivation hydraulic lash adjuster 54 being selectively switched between locked and unlocked states of operation by selectively applying pressurized oil to a latch mechanism (not shown) and selectively relieving the pressurized oil from the latch mechanism, it is to be understood that the latching mechanism could be actuated by means other than pressurized oil. For example, actuation of the latching mechanism could be accomplished electrically. Electrical operation of the latching mechanism could be accomplished, by way of example, with a solenoid actuator, piezoelectric actuator, stepper motor, or any other electric actuation means known to one skilled in the art.
While this invention has been described in terms of preferred embodiments thereof, it is not intended to be so limited, but rather only to the extent set forth in the claims that follow.
