The invention relates to an arrangement for generating a nonlinear force or torque characteristic curve, which can be used in particular in systems for actuating gas exchange valves of internal combustion engines.
Conventional devices for actuating gas exchange valves rely on the spring support for opening and closing the valve (DE 103 58 936 A1; DE 103 11 275 A1; DE 101 40 461 A1). Spring support advantageously reduces the forces to be supplied by the valve actuator with electromagnetic actuation of gas exchange valves, which also reduces the electric energy dissipated by the actuators. The problem remains that the valve actuator must hold at the end positions against the force of the springs. More particularly, when using the “classic” valve spring, the spring must provide the required closing force for the valve, which necessitates large holding forces.
In particular, operating a rotary actuator which transmits its force to two or more valves via a double-sided pivoting lever requires a device which supports the opening process of all valves to be actuated.
Accordingly, it is an object to provide an arrangement which produces at the end positions of the valve motion a force for accelerating the valve, wherein only a small force or no force at all is produced beyond the position “valve closed.”
The object is attained by providing an arrangement for producing a nonlinear force and torque characteristic curve according to the features of the independent claim. Particularly advantageous embodiments of the arrangement are recited in the corresponding dependent claims.
According to a core aspect of the invention, the arrangement of the invention takes over the function of the opening springs, which are otherwise a typical component of electromagnetic valve actuators, and generates a very large force at a very small rotation (e.g., at the beginning of the valve opening)—starting from a center zero position of the rotor of the valve actuator where the supplied force is zero or approximately zero-, which decreases substantially linearly with further rotation.
Starting from the center zero position, this force is oriented so as to support the opening operation of the respective valve(s) for both right-handed and left-handed rotation.
In cooperation with the closing spring which is present in each valve, the arrangement operates as a spring-mass oscillator.
The invention will now be described with reference to an exemplary embodiment. The appended drawings show in:
A double-lever 14 is disposed on the rotor shaft 2 of the reluctance motor of the rotary device for operating two gas exchange valves, wherein the ends of the lever 14 apply the required, intentionally nonlinear operating forces to the respective valve stem ends 9 and 15 of the two gas exchange valves 12 and 18. The classic valve springs 9 and 19 provide the closing forces for the gas exchange valves 12 and 18.
The arrangement AO according to the invention for generating a nonlinear force and/or torque characteristic curve operates as follows, as shown in
When the rotor shaft 2 is at the center position (torque=zero), the permanent magnet segments 3 of the rotor shaft and 7 of the stator 5 are positioned directly opposite one another, wherein the permanent magnet segments 3 and 7 facing each other are magnetized with opposite polarity. The magnetization with opposite polarity produces a torque for a small rotation due to the repulsion of the opposing permanent magnet segments 3 and 7, with a torque operating in the direction of the rotation. The rotation also causes a magnetic flux in the poles 6 of the stator 5 and the poles 4 of the rotor shaft 2, which in cooperation with the permanent magnet segments 3 and 7 which rotate towards the poles 4 and 6, produces a pulling force which operates in addition to the repulsive force that exists between the opposing permanent magnet segments 3 and 7. Further rotation produces an attractive force between the permanent magnet segments 7 of the stator 5 and the permanent magnet segments 3 of the rotor shaft 2, which have the same magnetization direction. These forces then attempt to minimize the air gap between the permanent magnet segments 3 and 7 and produce a torque in the aforementioned direction. When the rotor turns, the torque decreases to zero until the permanent magnet segments face each other.
In principle, the AO arrangement operates according to the invention even if no poles 4 and 6 are formed between the permanent magnet segments 7 of the stator 5 and the permanent magnet segments 3 of the rotor shaft 2. The resulting torque characteristic curve is approximately sinusoidal, as shown in
The resulting torque with respect to right and left rotation can be designed to be asymmetric by making the overlap between the permanent magnet segments 3 of the rotor shaft 2 and the permanent magnet segments 7 of the stator 5, as well at between the poles of rotor shaft 2 and stator 5 different, depending on the rotation direction. The overlap can be made different by decreasing or increasing the installation depth of the permanent magnet segments 3 and 7, respectively, of the stator 5 and the rotor shaft 2, as well as the installation depth of the poles 6 and 4 of the stator 5 and the rotor shaft 2 from one permanent pole segment to another permanent pole segment, or from one pole to another pole. An exemplary embodiment is shown in
The resulting force and/or torque characteristic curve illustrated in
The resulting curve illustrated in
The arrangement according to the invention for generating a nonlinear force and/or torque characteristic curve can also be implemented as a linear arrangement. The arrangement is here composed of a rotor having permanent magnet segments which are magnetized with alternating polarity, preferably perpendicular to the direction of movement, wherein iron poles can be formed between the magnet segments having different polarization. The stator, which is spaced from the rotor on both sides, is constructed of iron or a sheet metal laminate having ferromagnetic properties, and has on the side facing the rotor permanent magnet segments which are also alternatingly magnetized, preferably perpendicular to the direction of movement. Iron poles can be formed between the magnet segments with different polarization.
In another embodiment of the invention, the arrangement for generating a nonlinear force and/or torque characteristic curve includes a cylindrical rotor which performs a translation motion, wherein the stator is here arranged both inside and outside the rotor.
When the described embodiments of the invention are employed in valve controls, the valve actuator is assisted during the opening phase of the operated valves.
The arrangement according to the invention supplies in the end positions of the valve motion a force for accelerating the valves and, more particularly, applies only a small force or no force at all beyond the position “valve closed.”
In summary, the energy efficiency of the electromotive valve control can be significantly improved by employing the arrangement of the invention for generating a nonlinear force and/or torque characteristic curve.
AO arrangement for generating a nonlinear force and/or torque characteristic curve
1 reluctance motor
2 rotor shaft
3 permanent magnet segment (of the rotor shaft)
4 pole
5 stator
6 pole
7 permanent magnet segment (of the stator)
9 valve stem end
10 cylinder
11 piston
12 gas exchange valve
13 valve spring
14 double-lever
15 valve stem end
16 cylinder
17 piston
18 gas exchange valve
19 valve spring
Number | Date | Country | Kind |
---|---|---|---|
10 2006 023 654.8 | May 2006 | DE | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
---|---|---|---|---|
PCT/DE07/00868 | 5/11/2007 | WO | 00 | 11/17/2008 |