EP1132581B1 - Electromagnetic valve with pneumatic spring and toggle drive mechanism - Google Patents

Description

The present invention relates to valve control devices with linear movement along an axis comprising, for each valve, an actuator having a pallet of ferromagnetic material attached to a valve push rod movable in an actuator housing by electromagnetic means, having at minus a coil mounted on a ferromagnetic circuit, between two stable positions defined by the support of the pallet against the ferromagnetic circuit, and comprising elastic valve return means to a middle position.

The excitation of the coil or coils creates a force for bringing the pallet towards one of its stop positions, the direction of the force being determined either by the initial position of the pallet in the case where there is only one reel (patent application FR 98 12489), or by that of the coils with opposite actions which is supplied (patent application FR 98 11670 for example).

Conventionally, the elastic return means consist of a spring, or more frequently two helical mechanical springs surrounding the rod (requests for FR 98 11670 and FR 98 12489).

The valve-pallet-spring assembly constitutes an oscillating system having a natural frequency. This natural frequency limits the cadence of the oscillations that we can therefore reach engine speed. This rate is in fact higher the more that the engine fitted with the valves runs at higher speed. To increase the natural frequency, and therefore the regime which it is possible to reach, we proposed to reduce the mass of moving parts, which quickly comes up against limits. We have also proposed to increase the stiffness of the springs. But any increase in stiffness increases stresses and friction. High stiffness reduces the duration of life and increases the risk of seizure or rupture.

It has also already been proposed, for example in EP 0722039, to use pneumatic return springs of valve on camshaft engines, in particular competition engines.

The present invention starts in particular from the observation that a natural frequency high, obtained by a great stiffness of the springs, is essential only for the regimes high motors. It therefore aims to provide a device for adjusting the stiffness of the spring (s) - and therefore the natural frequency of the oscillating system - in according to the needs and for this it uses the possibilities of adjustment of stiffness that offers an air spring, as opposed to a mechanical spring.

The invention therefore provides an actuator valve. electromagnetic of the kind defined above comprising at least one spring tire according to claim 1, in particular making it possible to reduce the bulk in the axial direction of movement of the valves.

In a particular embodiment two pneumatic springs are consisting of two compartments of the same pneumatic cylinder. In another, a only pneumatic spring is provided, the opposing force being provided by a spring mechanical, which reduces air consumption. The stiffness of the oscillator thus formed being directly proportional to the mass of gas in the chambers of the cylinder, the real-time control of the gas pressure makes it possible to adjust the transition speed. Of plus the position of the equilibrium point can be continuously adjusted by controlling the pressures average or maximum in the room (s).

The pressurized air necessary for the "inflation" of each air spring may have various origins, such as those defined in the claims dependent. If the chambers are inflated by transferring part of compression energy from one or more actuators to the vacuum chambers relative to the feed actuator, we compensate for the effect of gas losses without using an external reserve or pneumatic group by transferring a part of the electromagnetic energy supplied by the coil (s) to the entropy compressed gases. All or part of the actuators of a motor are thus used as an air pump.

The invention also provides a method of launching a device above defined, especially with a view to starting an engine, facilitating operations, reducing the current overcurrents required during the initial phase of increase progressive oscillations until "sticking" of the pallet on the ferromagnetic circuit and reducing the risk of jamming, according to which before launching, we leave the valves to be placed without back pressure in the chamber (s); then we pilot the actuator electromagnetically or pneumatically until the initial "sticking" and gradually increases the pressure (s) to define the neutral position and the clean pulsation desired. In the case of a two-coil actuator, the back and forth initial over the entire stroke can be obtained without back pressure.

• la figure 1 montre schématiquement, en coupe longitudinale et à titre explicatif, un actionneur avec ses connexions avec un système de réglage de pression, à pompe à air externe et/ou régulateur de pilotage de pression ;
• la figure 2, similaire à une fraction de la figure 1, montre schématiquement une variante de réalisation à un seul ressort pneumatique ;
• la figure 3 montre une variante avec utilisation d'un régulateur à modulation de largeur d'impulsions ;
• la figure 4 montre un mode de réalisation d'une soupape à actionneur comprenant une liaison à genouillère.

The above characteristics, as well as others, will appear better on reading the following description of a particular embodiment, given by way of non-limiting example. The description refers to the accompanying drawings, in which:

• FIG. 1 schematically shows, in longitudinal section and by way of explanation, an actuator with its connections with a pressure adjustment system, with an external air pump and / or pressure control regulator;
• Figure 2, similar to a fraction of Figure 1, schematically shows an alternative embodiment with a single air spring;
• FIG. 3 shows a variant with the use of a pulse width modulation regulator;
• Figure 4 shows an embodiment of an actuator valve comprising a toggle link.

The actuator 10 shown in Figure 1 consists of an assembly intended to be fixed on the cylinder head 12 of an engine. It generally includes a housing made of material ferromagnetic.

The actuator comprises a pallet 22 made of ferromagnetic material, rectangular plan, advantageously laminated to reduce losses, fixed on a rod 24 valve drive 25. Several valves are mounted side by side.

In the illustrated embodiment, the valve stem 25 is separated from the rod 24. It is guided by a ring fixed to the cylinder head and can rotate in the latter.

Two pneumatic return springs are provided to maintain the valve at rest in a substantially central position between the closed position and the fully open position. One of the springs is compressed between a plate 30 fixed to the rod 24 and the extension of the part 16. The other spring is compressed between a plate 31 fixed to the valve stem and the bottom of the valve well formed in the cylinder head. The distribution clearance between the lifted rod and the closed valve guarantees sealing of the valve.

The case contains a ferromagnetic material carcass 36, advantageously laminated, delimiting a ferromagnetic circuit with the pallet, and a coil 38 placed in the core.

The pallet 22 has bevelled edges parallel to the poles of the core 36. In this arrangement, the armature is not magnetically saturated in its range of operation and the flow is closed mainly by passing through the armature, thanks to the forms pole pieces of the core. To impose the initial direction of movement of the pallet 22 from its rest position, the asymmetry of the upper flow circuit by compared to the lower flow circuit is accentuated by a central boss in the form of bar. When the pallet is in a rest position, and a magnetic flux is generated by the coil 38, closes on its way through the boss 84, which reduces the length of air gaps. When the pallet sticks against the core, in the high position, this boss is short-circuited and does not weaken the bonding forces. This provision significantly reduces the reluctance in the rest position and increases the reliability of the device.

During an initial phase of operation, the mobile assembly constituted by the valve and the pallet is alternately drawn up and down, by application to the coil of electric pulses at a frequency close to the natural frequency of the system. The coil 38 is initially supplied for a period corresponding to a fraction of the natural period, which causes a small amplitude displacement of the pallet, then the current is cut, then restored once the middle position is exceeded.

The current flowing through the coil 38 can be controlled by observing the position of the pallet 22 using a position sensor integrated in the device. The impulses of current in the coil are supplied at times such as at the time of application force, the speed of the paddle has the same direction as the force applied. Strength initial being of a given sign, as a result of the asymmetry, it suffices to apply a pulse only once per period.

In the embodiment illustrated in FIG. 1, a first pneumatic spring consists of a piston 30 fixed to the rod 24 and sliding in a cylinder 40 fixed to the core 36. The second return spring comprises a piston 34 fixed to the valve stem and also sliding in the cylinder 40. In FIG. 1, this cylinder has been shown fully protruding above the cylinder head 12. In practice, it may in part be placed in a well made in the cylinder head. Each of the pistons 30 and 34 carries a seal sliding seal. The stem 24 and the valve stem are guided by extensions of the cylinder bottoms, also bearing seals. Stiffness air springs depends on the maximum pressure in the compartments limited by the pistons 30 and 34. FIG. 1 shows means for adjusting the pressure maximum comprising a solenoid valve 42 controlled by a calculating member 44 which may be the engine control computer. This solenoid valve can take several positions. In one of these positions, it connects the compartments of one and the other of the air springs to a manifold 44 connected to an accumulator 46, via non-return valves 48. In this position, the pressures in the two compartments are equal and are those prevailing in the accumulator, powered by a pump external 50. Another position of the solenoid valve makes it possible to connect the two compartments at a landfill 50. Finally, other positions can also be provided, allowing one of the compartments to be connected to the landfill.

Such an arrangement makes it possible to adjust the pressure prevailing in the compartment. By adjusting the maximum pressures (and therefore the minimum pressures) which reign in two compartments at different values, it is possible to adjust the rest position of the rod 24 and therefore of the valve 25.

The same collector 44 can supply several solenoid valves 42, corresponding to different actuators.

In an alternative embodiment, the solenoid valves are provided to allow at least one of the actuators to operate as a pump, which makes it possible to dispense with an external pump 51. For this, links 52, indicated in dashes in FIG. 1, connect the manifold 44 to the solenoid valves via non-return valves 56 do allowing air flow only from the solenoid valve to the manifold. The calculator 44 can then be provided to place the solenoid valve corresponding to a compartment actuator whose volume is reduced due to the electromagnetic control with the outlet fitted with non-return valve 56.

By appropriate control of the computer 51, it is possible to adjust the maximum pressure in the compartments during normal operation, so as to adjust the stiffness and the rest position, but also to empty the compartments before launching the control device. In this case the first supply of the coil 38 of an actuator causes the pallet 22 to come into abutment, since none antagonistic force is present. The pressure can then be increased gradually, and the time required for the oscillating system to pass alternately in abutment in these two extreme and reduced positions. In normal operation, the stiffness will be fixed so as not to search for a frequency clean of high resonance only when it is necessary due to a high speed of the engine.

The actuator, a fraction of which is shown in Figure 2, or to the elements corresponding to those of FIG. 1 bear the same reference number, includes a single air spring, constituted by the piston 34 fixed to the valve stem 25. The opposing spring is a mechanical spring 54 acting in the closing direction of the valve. Compared to that of FIG. 1, this embodiment has the advantage of more great simplicity and less friction loss due to a reduction in the number of joints. In return, it does not make it possible to fix the rest position independently of stiffness.

FIG. 3 shows an alternative embodiment in which the pressure in the accumulator 46 is regulated by a solenoid valve 56 controlled by modulations pulse width.

Whichever embodiment is adopted, it is possible to reduce the speed when the valve approaches its fully open (or closed) position by a dashpot type device, comprising for example a calibrated tube 58 fixed to the cylinder and a plunger 60 fixed to the piston 34.

In the embodiment of the invention shown in Figure 4, where the organs corresponding to those of FIG. 1 still bear the same reference number, the cylinder is not aligned with valve 25. This valve is fitted with a spring recall 54 of conventional type, compressed between the cylinder head and a plate 60 fixed at the I end valve stem. The rod 24 is fixed to a pivot 62 connecting a rod 64 which turns around a fixed point 66 and a link 68 whose end rotates around an axis 70 belonging to a rocker 72 which rests on the plate 60. The pneumatic spring limited by the piston 34 and the cylinder allows to exert on the pivot 62 a force in the direction of the arrow f, which causes the displacement of the rocker 72 and the opening of the valve. This toggle joint assembly can also be used with an actuator of the above type, with two pneumatic springs.

In an alternative embodiment, the spring 54 is eliminated and the rocker 72 is then constituted by an elastic blade connected to the valve stem 25 to exert a effort in the direction of closing.

In another variant, the spring 54 is omitted and the actuator comprises two air springs comparable to those in Figure 1. The toggle arrangement of Figure 4 can also be used with an actuator with two or more mechanical springs generally with all the actuators of Figures 1 to 3.

The complete device generally comprises as many actuators as there are valves fitted on the engine. It is possible to use a single power circuit air springs of all actuators. However, it will often be preferable to provide a circuit comprising means for adjusting the pressure in the springs separately. Such an arrangement allows for example, when there are two valves intake per cylinder, use only one valve leaving the other closed in permanence during periods of engine operation which does not require heavy filling of combustion chambers. In this case, maintaining a high pressure in the air spring acting in the closing direction with venting the other spring may help avoid leaving the coil or of the actuator coils supplied with current. In the case of an air spring in the opening direction and a mechanical spring in the closing direction, it is enough empty the air spring compartment to leave the valve closed.

The arrangement according to the invention is applicable whatever the type of circuit magnetic provided, including when the actuators of two adjacent valves of same type share the same magnetic circuit (patent application FR 99 04472). The device is also usable both in the case of a reel control using a signal supplied by a position sensor that in the absence of such a position sensor position.

The compartment (s) can be delimited by metal bellows, the possible elasticity participates in the spring function.

Claims (6)

1. A valve for moving linearly along an axis of a linear actuator, said actuator comprising:

   a moving armature (22) of ferromagnetic material fixed to a valve push rod (24) and movable in a housing (40) of the actuator by electromagnetic means having at least one coil (38) mounted on a ferromagnetic circuit, the rod (24) being movable between two stable positions defined by the armature (22) pressing against a ferromagnetic circuit of said means; and

   at least one pneumatic spring for returning the rod (24) provided with means enabling the mean or maximum pressure therein to be adjusted,

      the valve being characterized in that said actuator is placed obliquely relative to the axis of the valve (25) and is connected to the rod (24) via a toggle mechanism (62, 64, 68, 70).
2. A valve according to claim 1, characterized in that the actuator has two pneumatic springs, acting in opposite directions.
3. A valve according to claim 1, characterized in that the actuator has a pneumatic spring and a mechanical spring tuned to the mass of the moving equipment of the valve-actuator assembly and acting in opposite directions to each other.
4. A valve according to any one of claims 1, 2, and 3, characterized in that the adjustment means are designed to reduce or eliminate pressure during starting.
5. A valve according to any one of claims 1 to 4, characterized in that said means comprise an air pump and a buffer accumulator and a regulator for regulating the pressure delivered by the accumulator.
6. A valve according to any one of claims 1 to 4, characterized in that said means enabling the mean or maximum pressure to be adjusted comprise the actuator.

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