Patent Application
20090173297
The present invention refers to a variable valve timing device usable with and for in internal combustion engine.
EP 1 347 154 A2 shows a swivel-type adjuster that is designated to be used with a control shaft of a variable valve train. A first hydraulic rotatable mechanism is connected to a second hydraulic rotatable mechanism so that by choosing a raw adjustment and by choosing a fine tuning adjustment an exact position for an eccenter of the variable valve train can be picked. Accordingly, it can be said that the angular position of the eccenter is depicted by a two-stage system.
U.S. Pat. No. 2,911,956 describes a plate-like shaft positioner by which a swivel movement of a first plate influences the swivel range of a second plate and so forth.
WO 01/12996 shows in FIG. 5a a two stator vane cam phasing system in which a rotor is limited in its swivel movements by rotating first and second stator.
Further, by studying U.S. Pat. No. 5,233,948 a person skilled in the art would realize that many advantages can be found by a camshaft with cams that can be superposed. Consequently, for many years there has been a need to design some kind of phase adjuster that can operate such a camshaft. However, practical solutions that actually work in an engine environment can rarely be found. As in U.S. Pat. No. 5,233,948, many basics are only laid open on a theoretical level but there is no teaching how to make them work in practice.
Attempts how to make such camshafts work can be derived from FIGS. 4a, 4b, 4c of U.S. Pat. No. 5,235. In this document, the figures show a coaxially arranged double camshaft with at least two sets of cams which are offset by an angle. The cams are mounted by fastening pins and fastening clips onto the bearing camshaft. A similar embodiment can be found in WO 2005/040 562 A1. The documents teach a type of hydraulic linear cylinder to select certain positions for the cam. Further, a similar design is shown in FIG. 1 of DE 43 32 868 A1. A further linear adjustable device for camshafts is shown in EP 0 397 540 A1. A different system can be seen in FIGS. 5 and 6 of U.S. Pat. No. 4,332,222 in which a contour bearing pin determines the angle of two cams and by that the position of the camshaft. A document that teaches a very simple and light hollow camshaft is DE 36 24 827. The hollow camshaft taught in that document is, however, outdated in the meantime because nowadays both camshafts have to offer a phase adjustment option. Further reasoning for creating a special contour of a cam can be found in DE 199 14 909 A1, which shows an auxiliary cam for adjusting the contour of the main cam with the purpose to control the gas exchange valves a second time. For reasons of completeness, the two documents JP 11 17 31 20 and WO 1992 012 333 are named.
From the foregoing prior art, it can be concluded that for years and years the industry has been looking for a workable design which enables the adjusting of the phasing of occurrences in a gas exchange valve train.
The further graphical representation of a double camshaft can be seen in DE 10 2005 014 680 A1 wherein the graphics stop at the oil distribution bearing. It may be assumed that the Applicant stopped at the point because further components were still needed. The document WO 2005/040562 describes a camshaft with at least two cams. The cams are axially arranged and displaceable. However, the document falls short in teaching how to operate the camshaft in a combustion engine.
A first sprocket and a second sprocket for a cam phaser attached to a hollow camshaft can be seen in U.S. Pat. No. 6,253,719 B1. Instead of arranging both sprockets in parallel, a different design is shown in U.S. Pat. No. 6,725,817 B2. A first cam phaser that is the inner cam phaser is surrounded by a second cam phaser that is the outer cam phaser. In the meantime, it is known from many different car manufacturers that both types of systems do not work as expected. There is a need to enhance the possible angle of adjustment.
U.S. Pat. No. 6,076,492 shows that it is widely known that the alignment of a cam phaser, a cylinder head, and a control valve together with a camshaft in a stationary manner is quite difficult. For example, one difficulty can be found by the canting of the components one to the other.
The described embodiments in the prior art of two offsetable and adjustable gas exchange valve actuation means on one single control shaft have been discussed above to include and incorporate them in the specification in order to enhance the specification and to lead the reader to the more challenging aspects of the present invention.
A gas exchange valve control shaft comprising two camshafts encroaching each other preferably coaxially arranged with the outer camshaft surrounding the inner camshaft, is also referred to as a double camshaft. A double camshaft is a camshaft which is assembled from two pieces. Persons skilled in the art often associate only one single shaft when hearing a camshaft of which all cams are placed in stationary relationship one to the other. A camshaft within the scope of the present invention is a camshaft of one, two or even more camshafts, especially camshafts having the same axle.
It is desirable to offer a cam phasing device as part of a variable valve timing device that is applicable to internal combustion engines. Especially with camshafts that comprise adjustable cams for intake and exhaust gas exchange valves on the same camshaft, a cam phaser device may be needed. Advantageously, any kind of camshaft can be operated that has two different sets of cams on the very same camshaft. The device shall be applicable in an automotive environment as an automotive component.
A variable valve timing device of an internal combustion engine is a device that changes or adapts the relative position of a gas exchange valve actuating component like a cam in respect to a further shaft like a crankshaft. It is widely known to use camshafts for transmitting the actuating impulse. The impulse is applicable on at least one—normally several—gas exchange valves via a control shaft. The control shaft is of a kind that the shaft has at least two concentrically arranged camshafts. The camshafts are adjustable in a rotatable manner with respect to each other. The adjustment is achieved by adjusting a cam of the first camshaft in terms of its angle towards a cam of the second camshaft. To select the position, a cam phasing device is needed. The cam phasing device operates by rotatable vanes provoking a swivelling relative movement between a driven member and an output member. In one embodiment the vanes are profiled. In a further embodiment, the vanes are flat, three-dimensional blocks extending out of a central rotor which can be referred to as rotor cores. Central rotor and vanes are part of a vane adjuster. The cam phasing device comprises at least two pivotable vane adjusters. Each pivotable vane adjuster is assigned to one of the two camshafts. In particular, a first vane adjuster is fixed to a first camshaft and a second vane adjuster is fixed to a second camshaft. The first vane adjuster operates the first camshaft whereas the second vane adjuster operates the second camshaft. The pivotable vane adjusters are arranged axially one after the other in a direction of a valve control shaft. Both vane adjusters are on a common axis. The vane adjusters do not influence each other in their maximum swivel range. The first vane adjuster may still cover its full range while the second vane adjuster has picked any position between its maximum advanced and its maximum retarded position. With this design, the position of a first a camshaft does not influence the selectability of a position for the second camshaft still occupying the same elongated space.
The variable valve timing device further comprises rotor type vane adjusters in that each pivotable vane adjuster is designed in a rotor-type manner. Each rotor type vane adjuster can be changed in respect of its phase by hydraulic pressure in two sets of hydraulic chambers. The phase is measured in respect of a further shaft like the camshaft. The two sets of hydraulic chambers form counter moving chambers to each other. The pivotable vane adjusters each constitute an output member of one of the cam-shafts. Each output member comprises a vane rim. The vane rims are attached to rotor cores being movable between a first position and a second position limited by division bars of a surrounding stator housing. By using the design of vane type cam phasers—which are known to a certain extent by themselves—a very fast and very responsive adjuster can be created.
The variable valve timing device has a double camshaft. The gas exchange valve control shaft is a coaxially arranged double camshaft. Of that double camshaft the first camshaft is formed as an hollow body and in the hollow body the second camshaft is aligned and placed in a manner so that through at least one recess a cam of the second camshaft pokes out to an outside of the first camshaft. The double camshaft is very efficient in terms of space. It occupies very little additional space outside of the camshaft as is necessary and advantageous in internal combustion engines.
The variable valve timing device has only one drive pulley. The drive pulley is exposed to a driving means like a chain or a belt. The cam phasing device has only one drive pulley such as a sprocket adapted to be driven by a chain which can surround a crankshaft of the internal combustion engine. The variable valve timing device has a side which is a near side of the camshaft, and the variable valve timing device has a side which is a far side from the camshaft. The variable valve timing device is planar. The variable valve timing device has a communication collar on the near side. The near side bears conduits for intake and piping of a hydraulic fluid to each of the sets of chambers of the first and said second pivotable vane adjuster. The communication collar moves synchronously along with the drive pulley. The integration of hydraulic conduits for the first and second vane adjuster contributes to the compactness of the variable valve timing device. The same applies to using only one drive pulley.
The variable valve timing device has at least four conduits. Two of the four conduits are located in the vicinity of an axis of the camshaft which channel fluid from the communication collar to the pivotable vane adjuster. They conduct hydraulic fluid like engine oil to the vane adjuster which is located farther away from the communication collar than the second pivotable vane adjuster. The two of the four conduits are located remotely to the axis of the camshaft channel from the communication collar to the second pivotable vane adjuster. The second vane adjuster is located nearer to the communication collar. In a very dense circular cross section all conduits necessary for operation can be placed in the rotor core and the core of the variable valve timing device.
In a further advantageous embodiment, the variable valve timing device bears an oil distribution adapter. The oil distribution adapter is centered in the cam phasing device. The cam phasing device is penetrated by at least four longitudinal fluid passages. In one embodiment, each one of the fluid passages is of a different length. The fluid passages open out into one of the sets of hydraulic chambers. This alternative design in respect of oil distribution can be easily manufactured while being still very reliable.
The variable valve timing device has at least two output members. One of the output members is located farther away from the gas exchange valve control shaft and operates the camshaft which is an inner camshaft in comparison to the second camshaft. One of the output members is located nearer to the gas exchange valve control shaft and operates the camshaft which is an outer camshaft and encloses the inner camshaft. The output member which is farther away is screwed to the inner camshaft whereas the output member which is located nearer to the gas exchange valve control shaft is shrink fitted on the outer camshaft. The type of fixation is a fast and reliable method for fixing the vane adjusters to the camshafts.
The variable valve timing device has four hydraulic ports. The four hydraulic ports are placed in the communication collar. The ports form channels from a stationary part such as a cylinder head of the internal combustion engine to each set of hydraulic chambers of each pivotable vane adjuster so that the communication collar forms part of a bearing ring. By this means, the hydraulic fluid is tuneable in each channel. Each vane adjuster can take up a desirable position independent from the other vane adjuster.
The variable valve timing device has a spring. The spring can be a coil spring. The spring can be designed as an inlay in the driven member. The spring props on one side against the pulley and pushes one of the pivotable vane adjusters in a pre-selected state. Preferably, the intake valves take on a pre-selected position in case of emergency or uncontrolled hydraulic pressure. As a result, the internal combustion engine may be operated even when the hydraulic circuit does not work as anticipated.
The present invention will hereinafter be described in conjunction with the appended drawing figures, wherein like reference numerals denote like elements, and:
The ensuing detailed description provides exemplary embodiments only, and is not intended to limit the scope, applicability, or configuration of the invention. Rather, the ensuing detailed description of the exemplary embodiments will provide those skilled in the art with an enabling description for implementing an embodiment of the invention. It should be understood that various changes may be made in the function and arrangement of elements without departing from the spirit and scope of the invention as set forth in the appended claims.
In
One example embodiment of a locking mechanism comprising the components locking pin 34, lock spring 35, and spring plate 36 is shown in
The cam phasing device 1 in accordance with
A further example embodiment in accordance with the invention can be seen in
A further advantageous example embodiment of a cam phasing device 1 with two camshafts 16, 18 in accordance with the invention can be seen in
Although only three example embodiments of the present invention have been described in detail, it should be apparent to someone skilled in the art that the described embodiments can only be understood as examples that do not impose any limitation on the scope of the invention and how to realize the invention.
Consequently, the scope of the invention also includes the usage of more than just two individual rotors. The scope of the invention also covers a cam phasing device with and without additional adapters between camshafts and cam phasing device. The drive torso can be actuated by a crank shaft, by a belt, by meshing gears, and by an electric motor.
The present invention has many advantages. Only one single device is needed to operate and actuate two shafts. This contributes to the reduction in size and package. One component can be handled more easily and can be attached to the concentric camshaft easier than all devices known up to now.
In addition, by using two parallel plans for the rotors, the dual camshaft phaser, also called cam phasing device 1, is able to drive the dual concentric camshaft. The dual phaser consists of two individual phasers stacked at the end of the concentric camshafts 16, 18. The individual phasers drive the separate camshafts in the dual concentric camshafts. The two phasers are using common designed stators 6, 8 and rotors 4, 5 with a shared center plate 7. The stacked stators 6, 8 and rotors 4, 5 are sandwiched inside the sprocket with back plate 9 and the front plate 2. Screws 10 pass through the sprocket with back plate 9, back stator 8, center plate 7, front stator 6, and front plate 2, holding them together as a single stacked assembly.
A spindle 3 is attached to the front rotor 4 and reaches through the back rotor 5 to drive the center shaft 18 of the dual concentric camshaft 101. The spindle 3 has fluid passages 20, 21, 22, 23 to feed hydraulic fluid (oil) through. These passages can also feed from the rear of the phaser through the camshaft 101. The oil is supplied from the engine oil system by two control valves (not shown in the figures). One of the control valves controls the oil feed 20, 21 to the front rotor 4. This oil moves through the passages 24, 25 of the rotor 4 to either side of the vanes to rotate the center shaft 18 to the desired position. The position is infinite within a set value between 30 to 70 degrees (usually around 50 degrees) of the crankshaft rotational position.
The rear rotor 5 is attached to the rear adapter 11, which drives the outside shaft 16 of the dual concentric camshaft, which is attached through first journal 15. A second control valve controls oil feed through passages 22, 23 in the area of the spindle 3 that reaches through the rear rotor 5. The oil moves through passages 26, 27 to either side of the vanes of the rear rotor 5 to rotate the outer shaft 16 to a desired position. The position is infinite within a set value between 30 to 70 degrees (usually around 50 degrees) of the crankshaft rotational position.
At engine startup both rotors 4, 5 can be locked (in an alternative example embodiment) in a determined position when the rotors 4, 5 are in the locked position with the lock pins 34. The lock pins are held in place by the lock spring 35 and spring plate 36. As the engine starts and the control valves feed the oil pressure to disengage the lock pins 34 the rotors are free to move.
Although the invention has been described in connection with various illustrated embodiments, numerous modifications and adaptations may be made thereto without departing from the spirit and scope of the invention as set forth in the claims.
