Fast-Acting Toggling Armature Uses Centring Spring

Abstract

A translating actuator acting between two extreme positions defined by mechanical stops is described. Said actuator comprises: an armature mass movable relative to the armature body, a stiff armature spring set such that the natural resting position of the armature mass is close to the centre of travel between the two extreme positions and pair of latches with sufficient holding force that the armature mass can be held at either extreme position against the restoring force of the spring and can be released quickly relative to the natural period of vibration determined by the armature mass on the armature spring.

Claims

1. A translating actuator acting between two extreme positions defined by mechanical stops comprising: an armature mass movable relative to the armature body, a stiff armature spring set such that the natural resting position of the armature mass is close to the centre of travel between the two extreme positions and a pair of latches with sufficient holding force that the armature mass can be held at either extreme position against the restoring force of the spring and can be released quickly relative to the natural period of vibration determined by the armature mass on the armature spring.

2. A translating actuator as described in claim 1 in which the latches are realised magnetically, held in place by magnetic flux driven by permanent magnet material and releasable very quickly by a pulse of current creating a pattern of magneto-motive force opposing that provided by the permanent magnet material.

3. An actuation system for a poppet valve based on the translating actuator of claim 1 in which the poppet valve is an integral part of the armature mass and in which the pressure difference maintained by the poppet valve at its closed position acts mainly or exclusively to hold the armature mass at that position against the restoring force of the spring.

4. An actuation system of claim 3 that is customised for operation at one specific frequency through the provision of acoustic chambers in the valve body housing such that the dynamic gas pressures within the actuation system do not significantly impede the motion of the armature mass.

5. A translating actuator acting between mechanical stops, said actuator comprising: a valve mass movable between said stops; a valve spring acting on the valve mass, said valve spring having a resting position between said stops; a lower latch for holding the valve mass at a lower end of travel; and an upper latch for holding the valve mass at an upper end of the travel; and wherein each latch are configured to release the valve mass at a speed quicker than the natural period of vibration determined by the valve mass on the valve spring.

6. The actuator according to claim 5, wherein the valve mass comprises a poppet head, a valve stem, stem-to-spring interfaces and a target disc, said disc comprising ferromagnetic material and configured to allow rapid changes in flux through axial faces of the disc.

7. The actuator according to claim 5, wherein the valve spring comprises four parallel planar springs.

8. The actuator according to claim 7, wherein the planar springs comprise spring steel sheet.

9. The actuator according to claim 7, further comprising a valve body in which said valve mass is moveable relative thereto.

10. The actuator according to claim 9, wherein the valve body comprises a valve seat and a bush for maintaining alignment of the valve stem with the valve seat.

11. The actuator according to claim 10, wherein the valve body further comprises a retaining plate for the bush and body pieces, each body piece for securing said planar springs or said latches.

12. The actuator according to claim 5, wherein the lower latch comprises a plurality of pole pieces and corresponding pieces of permanent magnet material.

13. The actuator according to claim 12, wherein the pieces of permanent magnet material are aligned with an energising coil for operating the latch.

Description

DESCRIPTION OF THE FIGURES

[0063] Embodiments will be described, by way of example only, with reference to the drawings, in which

[0064] FIG. 1 shows the invention in schematic form.

[0065] FIG. 2 shows a first embodiment of the invention.

[0066] FIGS. 3 to 6 provide some detail of one possible configuration of magnetic latches that would serve the latch function required in this invention.

[0067] FIG. 7 shows a profile of a single plane of spring steel that can serve the combined functions of guiding the valve stem and providing a spring force that tends to drive the valve stem back towards the centre of travel.

[0068] It should be noted that the Figures are diagrammatic and not drawn to scale. Relative dimensions and proportions of parts of these Figures have been shown exaggerated or reduced in size, for the sake of clarity and convenience in the drawings. The same reference signs are generally used to refer to corresponding or similar feature in modified and different embodiments.

THE GENERIC EMBODIMENT

[0069] FIG. 1 shows the invention in schematic form and exposes the four key elements required to realise this invention: the valve mass (1), the valve spring (2), the lower latch (3) which serves to hold the valve mass at the lower end of its travel and the upper latch (4) which serves to hold the valve mass at the upper end of its travel.

[0070] For improved clarity throughout the description of this invention, we focus on the application to poppet-valve actuation whilst recognising in general that a wider range of applications is possible. In wider applications, the valve mass (1) would simply be the armature mass and the valve spring would be the armature spring.

[0071] The lower and upper latches must each be able to release the valve mass extremely quickly and each one must be capable of doing more work attracting the valve mass towards it than is done against the latch as the valve mass is pulling away during a release event. The difference between these two work quantities must be sufficient to make up the small parasitic losses that inevitably happen during a valve transit event.

A First Embodiment

[0072] FIG. 2 shows a possible embodiment of this invention following the schematic form of FIG. 1. In this embodiment, components (11), (12), (13), (14) and (15) are all elements of the valve mass (1). Correspondingly, components (21), (22), (23) and (24) all combine to form the valve spring (2). The lower latch (3) is shown as a single object in FIG. 2 but FIGS. 3-5 provide further insight into this. Similarly, the upper latch (4) is shown as a single object in FIG. 2 and its nature can be similar or identical to the nature of the lower latch. In FIG. 2, elements of the housing are numbered (51) through (59).

[0073] The valve mass comprises: the poppet head itself (11), the valve stem (12), a first stem-to-spring interface (13), a second stem-to-spring interface (14) and a target disc (15) that comprises ferromagnetic material and is configured (using either highly resistive material or else electrical continuity breaks) to be able to allow very rapid changes in flux through its axial faces.

[0074] The valve spring in this embodiment comprises four parallel planar springs -formed from spring steel sheet as will be described later: (21), (22), (23) and (24) respectively.

[0075] The body of the valve actuation system comprises the valve seat (51), a bush (52) to maintain alignment of the valve stem with the valve seat, a retaining plate (53) for the bush, a first main valve body piece (54), a second main valve body piece (55) that helps to secure two planar springs ((23) and (24)), a third main valve body piece (56) that carries the lower latch (3), a fourth main valve body piece (57) that carries the upper latch (4), a fifth main valve body piece (58) that helps to secure the remaining two planar springs ((21) and (21)) and finally a top piece of the valve body (59) that finally seals the valve chamber.

[0076] FIGS. 3 - 6 show that each the lower latch can be realised as a set of 8 individual ferromagnetic (or ferrimagnetic) pole pieces, (301) - (308), and 8 corresponding pieces of permanent magnet material, (311) - (318). In general, a magnetic latch of this generic configuration may be realised with any even number of pole pieces but 8 is a convenient number for illustration. Note that in this context, the terms ferromagnetic and ferrimagnetic are used to mean materials that are highly permeable to magnetic flux over a good range of flux densities (typically up to ~2 Tesla) and that do not have wide hysteresis loops. The term “soft magnetic material” could be used by some to indicate such material.

[0077] Corresponding to each separate piece of permanent magnet material, there is provided a coil, (321) - (328). When the coil is energised with current in one direction, the MMF produced by that coil opposes the MMF produced by the magnet. By this method, the magnetic latch can be released very quickly. All of the coils are connected together such that all of the permanent magnet MMF contributions are opposed simultaneously.

[0078] FIG. 3 shows the plan view of the lower latch and the direction of magnetisation of the permanent magnet pieces (311) - (318) is clear from the arrows presented in this image. In this figure, any one pole-piece has circumferential faces contacting two different pieces of permanent magnet material and those are magnetised in opposite circumferential senses. That is to say, if the piece of permanent magnet material on one side of a pole-piece is trying to drive flux in a clockwise direction (viewed from above), then the piece of permanent magnet material on the opposite side of that pole-piece is trying to drive flux in the counter-clockwise direction (viewed from above).

[0079] FIG. 4 shows an oblique view of a single pole-piece. FIG. 5 shows a second plan view of the lower latch with clearer indication of the axial face on this figure. The coils (321)-(328) are omitted from this view. FIG. 6 shows an oblique view of the assembled latch - again omitting to include the coils (321)-(328).

[0080] FIG. 7 shows a view of a possible geometry of one of the planar springs (21) -(24). In this, the planar spring is formed by punching or laser-cutting or water-jetting features from a flat sheet blank. The “spokes” that remain connecting the outer annulus to the inner annulus are deliberately much wider close to the outer annulus than they are close to the inner annulus because the intention is that when the planar spring is deflected by its maximum amount, the slope of each “spoke” is close to zero at the outer annulus but is substantial at the inner annulus. In this way, strain energy is concentrated in spring material that does not move much and the main function of the spoke material close to the inner annulus is to transmit force.

[0081] From reading the present disclosure, other variations and modifications will be apparent to the skilled person. Such variations and modifications may involve equivalent and other features which are already known in the art and which may be used instead of, or in addition to, features already described herein.

[0082] Although the appended claims are directed to particular combinations of features, it should be understood that the scope of the disclosure of the present invention also includes any novel feature or any novel combination of features disclosed herein either explicitly or implicitly or any generalisation thereof, whether or not it relates to the same invention as presently claimed in any claim and whether or not it mitigates any or all of the same technical problems as does the present invention.

[0083] Features which are described in the context of separate embodiments may also be provided in combination in a single embodiment. Conversely, various features which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable sub combination. The applicant hereby gives notice that new claims may be formulated to such features and/or combinations of such features during the prosecution of the present application or of any further application derived therefrom.

[0084] For the sake of completeness it is also stated that the term “comprising” does not exclude other elements or steps, the term “a” or “an” does not exclude a plurality, and reference signs in the claims shall not be construed as limiting the scope of the claims.