US11022232B2 - Valve with proportional electromagnetic actuator

One limitation of conventional monostable solenoïd actuators, especially the proportional ones (which are not only used in ON/OFF regulation but on whole the stroke window, which require radial and not axial airgaps), is that the force that they can provide is quite limited for a given size of actuator. This is because the mobile part is usually set in the center of the actuator and it saturates easily as electromagnetic fluxes concentrate to the center of the actuator. With proportional actuator, it is even truer since radial air gaps are "less efficient" than axial airgap (used especially in ON/OFF actuators). To solve this problem, one can widen the section (and length) of the mobile part but this will also make it more difficult to move and that is not wanted. It is always better for the mobile part to be small and mostly light. In addition, a wider center diameter will induce much heavier coils for the same number of loops (more wiring, resistance increases so the length must increase as well). This leads to exponential actuator size and mass. This invention allows a mobile part that is not in the center of the solenoïd so the mobile part mass can be optimized as wanted. The integration is also easier as the rest of the actuator (fixed parts) can "be designed as once" : dimensions of the mobile part have almost no impact on the size of the center part (and thus on the size and mass of the coil). At last, the magnetic fluxes no longer change direction in the mobile part (only radial direction from one airgap to the other) so it is less prone to saturation singularities (that can become very problematic with proportional actuators).