The present invention relates to a device for controlling the kinematics of at least one valve, the device comprising at least one opening cam and one closing cam, and at least one lever device cooperating with the valve and subject, together with the latter, to the action of an elastic member.
The variable control of valves, i.e. variable timing, is a complex problem that has often been approached. According to several recent studies, the majority of the systems suggested up to now comprise a limited variability of opening durations or do not offer a progressive variation of the opening durations. Certain electro-hydraulic systems offer a higher flexibility of the opening duration, but they suffer from the disadvantage of being very complex and are subject to technical problems that are difficult to solve, such as delays and the compressibility in the hydraulic circuits as well as the space consumption of their components.
Based on this state of the art, it is an object of the present invention to propose a control device as cited above which allows to control the opening and closing duration of the valve over a wide range (comprised, for the opening, between 210° and 350° of camshaft rotation approximately), while varying the opening and closing times of the valve(s) independently of each other. The implementation of this device may be provided for a wide range of engines. This object is attained by a control device wherein the elastic member constitutes a detent means acting upon the assembly composed of the lever device and of the stem of the valve in the opening direction of the valve, and in that the assembly comprising the rocker arm and the cam allows the opening of the valve and furthermore generates the return movement of said valve onto its seat for its closure.
Embodiments of the invention will be described by way of non-limiting examples hereinafter with reference to the enclosed drawings where:
a and 5b are front views of the opening and closing cams in
Opening cam 5 includes three distinct geometric portions: a first concentric portion Y-A (corresponding to the retention of valve 8 against its seat 10 and to the takeover of rocker arm 1 during the closed valve phase (large radius R2 of the cam)), a second eccentric portion A-B (causing the opening movement of the valve), and a third concentric portion B-L (small radius R1 of the cam).
In analogy, closing cam 6 comprises a first concentric portion K-B′ (zone of takeover of rocker arm 1 during the open phase of valve 8 (small radius R3 of the cam)), a second eccentric portion B′-C (causing the closing movement of the valve), and a third concentric portion C-X, corresponding to the retention of valve 8 against its seat 10 (large radius R4 of the cam).
Valve 8 is provided at its lower end with a tulip 9 adapted to press against a seat 10, the tulip being followed by a stem 11 that is guided by a valve stem guide 12 and fastened by means of a locking device comprising a valve spring seat 13 cooperating with a circular clip 14 and sliding in a tubular valve retainer 15 whose upper part is fitted with a locking ring 16 allowing the closure of a non-referenced valve retainer chamber. Locking ring 16 is provided with a threaded bore for receiving an adjusting pin 16G for adjusting the initial tension of a spring 17 adapted to act upon stem 11 of the valve (through elements 13, 14).
This damping spring 17 is accommodated in the space formed between the bottom of valve retainer 15 and valve spring seat 13. The function of this damping spring is easily understood when comparing
Inversely to valve controls of the prior art, an elastic member acting upon valve 8 and rocker arm 1 is formed of a valve relieving spring 18. The latter tends to open the valve and allows the rocker arm, which retains the valve through valve retainer 15, damping spring 17 and locking device 13, 14, to follow the profile of the cams. Spring 18 is maintained by an upper spring seat 19, on one hand, and on the other hand, by a circular shoulder 20 formed around valve retainer 15.
In this embodiment for four valves per cylinder, the rocker arm is not actuated by a spring that is positioned in the axis of the valve stem but by a detent spring 28 one shank of which rests on a stop 29 while the other shank rests on a stop 30. The arrangement of the rocker arm is such that detent spring 28 tends to open the valve, as illustrated in
The stem, retainer, guide, and seat of the valve are similar to those of the preceding embodiment, as well as the damping system with damping spring 31, which is retained between a sleeve or threaded ring 16B closing a non-referenced chamber of a support 32 and sliding on the valve extension rod 57 with threaded end, on one hand, and a support nut 33 that is blocked by a counternut 34. Valve stem 11 and extension rod 57 are assembled by means of a coupling sleeve 35 that is retained between two counternuts 36.
Control pieces 50 and 51 are fitted on a distance over the ends of the camshafts. The ends comprise an internal coupling by straight spline 52, 53 and an external coupling by helicoidal grooves 43, 44.
In order to effect the mutual angular offset of cams 5, 6, one or the other of the control pieces (50, 51), or both, are slidingly displaced to obtain a shorter or longer valve opening duration.
This control device is also applicable in other timing gear systems, e.g. with finger control or with direct actuation.
Rocker arm 54, oscillating around its shaft 55, is similar to the one illustrated in
According to the example illustrated in
In
It follows that in a general manner, and conversely to the traditional devices of the prior art, the elastic detent means 18, 28 acts upon the pair [lever device (1; 21; 54)−valve stem (11)] in the opening direction of the valve (8), whereas the pair [rocker arm device−opening cam 5/closing cam 6] fulfills a double function, namely to allow the opening of the valve and to move it back to its seat 10 for its closure. Based on this original conception as described above, the operating mode may be demonstrated as follows (see particularly
The fact that the drives of the opening and of the closing camshafts are provided with an angular offsetting device with helicoidal grooves, on one hand, and that the profiles of the cams are in agreement, on the other hand, allows to vary the opening and the closing time of the valve independently of each other. Furthermore, the damping device ensures tightness between the seat and the valve without shocks in the timing gear and compensates for the lengthening of the valve due to thermal dilatation.
The cams can be mounted on their shafts in different ways and may be rotationally driven in the same direction. It is also possible to provide a respective shaft for each cam or a common shaft or common shafts.
Thanks to the original cam profiles, it is possible to obtain short (
Number | Date | Country | Kind |
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847/01 | May 2001 | CH | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/CH02/00244 | 5/7/2002 | WO | 00 | 4/7/2004 |
Publishing Document | Publishing Date | Country | Kind |
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WO02/090728 | 11/14/2002 | WO | A |
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1633882 | Ballot | Jun 1927 | A |
2641236 | Mansfield | Jun 1953 | A |
3313280 | Arutunoff et al. | Apr 1967 | A |
4420141 | Goloff | Dec 1983 | A |
4724822 | Bonvallet | Feb 1988 | A |
Number | Date | Country |
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100 61 711 | Aug 2001 | DE |
359 715 | Oct 1931 | GB |
WO 9637688 | Nov 1996 | WO |
Number | Date | Country | |
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20040163615 A1 | Aug 2004 | US |