WO2016097497A1

WO2016097497A1 - External combustion engine

Info

Publication number: WO2016097497A1
Application number: PCT/FR2015/000222
Authority: WO
Inventors: Alain M. de LARMINAT
Original assignee: Cria Technologies
Priority date: 2014-12-09
Filing date: 2015-12-08
Publication date: 2016-06-23
Also published as: FR3029572A1; FR3029572B1

Abstract

The invention relates to an external combustion engine (1) comprising at least: a cylinder (3), a piston (2) defining a chamber (6), a displacement element (11) displaced by a driving body (12), a heater (4) for heating a hot area (10) and a cooler (5) for cooling a cold area (14) of the cylinder (3), and a mechanism (20, 21, 22) for actuating the translatory movement of the piston (2) in relation to the displacement element (11). The engine (1) also comprises an elastic restraint mechanism (23 to 27) exerting at least elastic restraint on the piston (2) in a position of compression of the chamber or elastic restraint on the piston (2) in a position of expansion of the chamber.

Description

EXTERNAL COMBUSTION ENGINE

The technical sector of the present invention is that of external combustion engines also designated by hot air motor.

Hot air engines of the Stirling type have been the subject of many developments. FR-2354452. filed in 1977 illustrates the principle of operation of a Stirling type engine equipped with a regenerator. The engine includes a burner performing a combustion outside the cylinder. A displacer, also designated by a sweeper, is arranged in the chamber delimited by the piston and the cylinder in order to force the circulation of the gaseous fluid between the hot and cold sources.

Stirling engines that do not require relaxation in the atmosphere. These engines are therefore advantageously particularly quiet. However, their use is generally limited to specific areas such as cogeneration boilers, for which low power is needed. Stirling type motors generally have low efficiencies, in particular because of mechanical friction and heat loss. Unused heat can advantageously be reused in a cogeneration boiler.

The present invention aims to overcome the disadvantages of the prior art by providing an external combustion engine whose structure allows better performance.

This objective is achieved by an external combustion engine comprising at least:

a cylinder having a closed end,

a piston movable in the cylinder delimiting a chamber filled with a gaseous fluid,

a displacer sliding in an unsealed manner in the cylinder and moved by a drive member,

at least one heater of a hot zone of the cylinder and at least one cooler of a cold zone of the cylinder, at least one mechanism for controlling the movement in translation of the piston with respect to the displacer so that the displacer comes at least partly opposite said cold zone in a first compression position of the chamber and at least in part towards said hot zone in a second expansion position of the chamber,

characterized in that it comprises an elastic retaining mechanism exerting at least a first elastic retention of the piston in said first position or a second elastic retention of the piston in said second position.

According to a feature of the invention, said first piston position corresponds to a maximum compression position of the chamber and said second piston position corresponds to a maximum expansion position of the chamber.

According to another particularity of the invention, in said second position the displacer comes entirely opposite the hot zone.

According to another particularity of the invention, in said first position the displacer comes entirely opposite the part of the cold zone in front of the piston.

According to another particularity of the invention, the drive member of the displacer comprises a shaft connected to the displacer and slidably sealed through the piston, the servo mechanism comprising a movable member in driving rotation of a first connecting rod connected to the shaft and a second connecting rod connected to the piston.

According to another feature of the invention, the elastic retaining mechanism exerts a mechanical action on a member integral with the drive shaft of the displacer to exert at least said first elastic retainer or said second elastic retainer.

According to another feature of the invention, the elastic retaining mechanism exerts a mechanical action on the servo mechanism to exert at least said first elastic retainer or said second elastic retainer.

According to another feature of the invention, the resilient retaining mechanism exerts a mechanical action on an element integral with the piston to exert at least said first elastic retainer or said second elastic retainer.

According to another feature of the invention, the elastic retaining mechanism comprises at least one pusher and a spring disposed between the pusher and its support and a portion forming at least a first ramp having a first inclination determined so as to exert a determined retention of the pusher, this portion being integral with the servo mechanism, piston or displacer.

According to another feature of the invention, said portion comprises a second ramp extending said first ramp, the second ramp having a second inclination less than said first inclination, the second inclination being determined so as to achieve a gradual slowing of said portion.

According to another particularity of the invention, the elastic retaining mechanism comprises a member for adjusting the retaining force exerted.

Another object of the invention relates to a cogeneration boiler producing electricity by means of a motor according to the invention for driving at least one core relative to at least one current-generating coil.

A very first advantage of the present invention is that the heating or cooling of the working gas can be optimized. It is indeed possible to achieve heating or isochoric cooling and in a position where the heating or cooling is optimized. Thus the average pressure difference between the expansion and the compression of the chamber is increased. As a result, the engine provides more work that translates into higher efficiency and higher motive power.

Another advantage of the present invention is that the movements of the piston and the sweeper in the cylinder can be performed at an optimum speed. A sudden release can indeed be carried out after a rise in pressure beyond a determined pressure threshold or after a pressure drop below a determined pressure threshold. Here again the efficiency of the engine is optimized.

Another advantage is to allow the adjustment of the driving force by imposing a heating temperature in the cylinder by adjusting the retaining force.

Other features, advantages and details of the invention will be better understood on reading the additional description which will follow of embodiments given by way of example in relation to drawings in which:

- Figure 1 shows a longitudinal sectional view of an engine according to the invention comprising two cylinders mounted opposite to each other and slaved in motion by the same servo mechanism;

- the figures. 2 to 4 show different positions of a piston and a displacer arranged in a motor cylinder according to the invention;

FIG. 5 represents an example of a retaining mechanism exerting an action directly on the shaft connected to the scanner of an engine according to the invention;

FIG. 6 represents an example of a retaining mechanism exerting an action directly on the piston of an engine according to the invention;

FIG. 7 represents an example of a cogeneration boiler comprising an engine according to the invention;

Figures 8 to 10 show different views of an elastic restraining mechanism exerting an action on a shaft.

The invention will now be described in more detail. Figure 1 shows a longitudinal sectional view of an engine comprising two cylinders 3a and 3b mounted opposite one another with their open end 15a and 15b facing each other. Each cylinder 3a or 3b has a closed end 10a or 10b. A piston 2a or 2b and a displacer 11a or 11b are housed in each cylinder 3a or 3b.

The piston 2a in its maximum advanced position in the cylinder 3a delimits a chamber 6a compressed to the maximum. The lia mover is also moved back to the maximum to come closest to the piston 2a. Of course, there is a functional game.

The piston 2b in its retracted maximum position in the cylinder 3b delimits a chamber 6b in a maximum expansion position. The displacer 11b is also advanced to the maximum to come closest to the closed end 10b of the cylinder 3b. Of course, there is a functional game.

Each piston 2a and 2b slides sealingly in a cylinder 3a or 3b, each sealed chamber 6a and 6b closing a gaseous fluid constituting the working gas.

Each mover 11a or 11b is secured to a drive shaft 12a or 12b. Each shaft 12a or 12b slides sealingly in the associated piston 2a or 2b.

A servo mechanism makes it possible to coordinate the movements of each displacer 11a or 11b with the movements of the associated piston 2a or 2b. The servo mechanism here comprises a rotating member 22 connected by a connecting rod 21a or 21b to each piston 2a or 2b and connected by another connecting rod 20a or 20b to each shaft 12a or 12b. The rotating member 22 is for example in the form of a shaft or a disc.

Each piston 2a or 2b is thus pushed towards the closed end 10a or 10b of the cylinder 3a or 3b while the associated displacer 11a or 11b is pulled towards the open end 15a or 15b of the cylinder by the servo mechanism.

Similarly, each displacer 11a or 11b is pushed towards the closed end 10a or 10b of the cylinder 3a or 3b while the associated piston 2a or 2b is pulled towards the open end 15a or 15b of the cylinder by the servo mechanism. The rods connected to the piston and the associated displacer are for example articulated at diametrically opposite points of the rotating member.

Each piston and each displacer is pulled and pushed alternately. The piston 2a or 2b and the displacer 11a or 11b associated are for example in phase opposition.

The pistons 2a and 2b and the displacers 11a and 11b in the two cylinders 3a and 3b are here coordinated in their movements by the same rotating member 22 of the servo mechanism.

Each cylinder 3a or 3b comprises a hot zone 10a or 10b and a cold zone 14a or 14b. A heater 4a or 4b is disposed around the hot zone 10a or 10b of each cylinder 3a or 3b. A cooler 5a or 5b is disposed around the cold zone 14a or 14b of each cylinder 3a or 3b.

The heater 4a or 4b and the cooler 5a or 5b are thermally insulated from each other. A thermally insulating material 7a or 7b is in particular disposed against each cylinder 3a or 3b and between its cooler 5a or 5b and its heater 4a or 4b.

The mechanism for controlling the movement in translation of the piston 2a relative to the displacer 11a makes it possible to bring the displacer 11a opposite the cold zone 14a into a compression position of the chamber 6a.

The displacer 11a which slides loosely in the cylinder 2a then allows to move the majority of the working gas in the hot zone of the cylinder while a negligible amount of gas is cooled in the cold zone.

The mechanism for controlling the translational movement of the piston 2b with respect to the displacer 11b also enables the displacer 11b to be brought into contact with the hot zone 10b in an expansion position of the chamber 6b. The displacer 11b then makes it possible to move the majority of the working gas in the cold zone of the cylinder while a negligible quantity of gas is reheated in the hot zone.

The engine further comprises a retaining mechanism in at least one expansion or compression position of the chambers 6a or 6b. The retaining mechanism here acts on the servo mechanism. When the force induced by the depression or compression exceeds the force exerted by the retaining mechanism, the latter then allows the relative movements of the piston relative to the associated displacer.

The retaining mechanism is here in the form a pusher 25 held elastically against the rotating member 22, the latter comprising two recesses 23 and 24 formed on its peripheral edge to cooperate with the pusher 25. The pusher 25 is for example in the form of an articulated roller or a rotating ball. The end of the pusher can roll or slide on the element against which it comes to rest.

The pusher is held in abutment against the rotating member 22 by a spring 26. The pusher 25 is for example movable in translation in a support 27 secured to a frame fixed relative to the cylinders 3a and 3b of the engine. The spring 26 is disposed between the pusher 25 and the support 27. A set screw 28 allows for example to adjust the position of a shim of the support 27 on which rests the spring 26. This screw allows adjustment of the pushing force of the pusher 25.

Thus the retaining mechanism can stop the rotating member 22 in its rotational movement when the pusher advances in a recess 23 or 24 and blocks each piston and each displacer in position. Each recess has in fact a slope of inclination determined to exert a determined restraint.

The elastic restraint can be made in a compression position of the chamber of each piston or in an expansion position of the chamber of each piston. The elastic restraint can also be performed both in a compression position of the chamber of each piston and in an expansion position of the chamber of each piston.

The motor can be held in the compression position of its chamber which is then heated until the pressure induces a force greater than that exerted by the elastic retaining mechanism. The sudden release of the piston 2a and the displacer 11a allows an optimum movement speed to an expansion position for a cooling of the working gas.

The restraint in the compression position makes it possible to heat the working gas kept compressed in a determined volume which increases the work done. by the engine. The compression position of the chamber in which the elastic restraint is exerted corresponds for example to the maximum compression position. In the maximum compression position where the elastic restraint is exerted, the displacer 11a is completely opposite the cold zone 14a in front of the piston and the heating is further optimized.

In the same way the motor can be retained in the expansion position of the chamber which is then cooled until the depression induces a greater force than that exerted by the elastic retaining mechanism. The sudden release of the piston 2b and the displacer 11b allows an optimum movement speed to a compression position for a warming of the working gas.

The restraint in the expansion position allows a cooling of the working gas maintained at a determined volume which increases the work provided by the engine. The expansion position of the chamber in which the elastic restraint is exerted corresponds for example to the maximum expansion position. In the maximum expansion position where the elastic restraint is exerted, the displacer 11b comes entirely opposite the hot zone 10a and the cooling is thus optimized.

Of course, in the case of a servo mechanism common to several engines, the forces induced by the depressions or compressions can accumulate. The elastic restraint exerted on this servo mechanism is then calculated according to the parameters of this plurality of motors. Moreover, the compression restraint threshold and the pressure lowering retention threshold can be adjusted independently of one another as needed.

Figures 2 to 4 show different positions of a piston and a displacer arranged in a motor cylinder according to the invention. _; The engine comprises a cylinder 3 in which are arranged a piston 2 and a displacer 11 integral with a shaft 12 sealingly sliding in the piston 2. The piston 2 delimits a sealed chamber 6 in the cylinder 3. The displacer 11 slides unsealed in the cylinder. A mechanism for controlling the movements of the piston 2 relative to the displacer comprises a member 22 movable in rotation driving a connecting rod 20 connected to the displacer 11 and a connecting rod 21 connected to the piston 2. The heater 4 is separated from the cooler 5 by a thermally-heated material insulation. The heater 4 is disposed around the hot zone 10 of the piston and the cooler 5 is disposed around the cold zone 14 of the piston. The elastic retaining mechanism exerts an action on the servo mechanism and more particularly on the rotating member 22 which comprises two recesses 23 and 24. These recesses 23 and 24 cooperate with a pusher 25 and correspond to one at a position of compression and the other at an expansion position. The recesses have a determined slope of inclination corresponding to a determined restraint of the pusher.

Figure 2 shows a maximum compression position of the chamber 6 in which the motor 1 is held by the elastic retaining mechanism. The pusher 25 is held elastically in the recess 23 and maintains the member 22 of the servo mechanism. The elastic retaining force corresponds to the inclination of the slope of the recess that must pass the pusher.

The piston is advanced to the maximum in the cylinder and the displacer 11 is disposed vis-à-vis the cold zone 14 in front of the piston 2. The rear of the piston 2 here corresponds to its opposite side facing the room 6.

The warming of the working gas is optimized and the pressure in the chamber increases until the force exerted on the piston allows the release by the elastic retaining mechanism. A rotational movement M30 of the member 22 movable in rotation is then initiated.

The elastic restraint allows a rise in pressure at constant volume. The expansion pressure can thus be adjusted by adjusting the holding force. Moreover, the release occurring at a determined pressure corresponds to a determined driving force. The driving force can be adjusted by adjusting the holding force.

Figure 3 shows the position of the engine 1 at a given moment. In this configuration the piston 2 and the displacer 11 are moving relative to each other. The member 22 movable in rotation is then at a speed 31 not zero. The sudden release of the piston by the elastic retaining mechanism makes it possible to optimize the speed of displacement as a function of the generated motive force. Preferably a high speed is set to shorten the piston displacement phases where cooling and warming of the working gas are not optimal. By adjusting a high speed of the piston, the work provided by the engine is further optimized, that is to say, the efficiency is improved and the power supplied is increased.

Figure 4 shows a maximum expansion position of the chamber 6 in which the motor 1 is held by the elastic retaining mechanism.

The piston 2 is retracted as far as possible into the cylinder 3 and the displacer 11 is placed opposite the hot zone 10 of the piston 3.

The cooling of the working gas is optimized and the pressure in the chamber decreases until the force exerted on the piston 2 allows the release by the elastic retaining mechanism. A rotational movement M32 of the member 22 movable in rotation is then initiated. The displacer and the piston then move to return to the position of the engine 1 shown in FIG.

The elastic restraint allows a lowering of the constant volume pressure. The pressure drop can thus be adjusted by adjusting the holding force. Moreover, the release occurring at a determined pressure, the mean pressure difference between the expansion and the compression of the chamber can thus be optimized. The work of the engine is thus optimized, that is to say that its performance is improved. This better performance translates into lower energy expenditure and higher available motive power. The elastic retaining mechanism here carries a restraint in the maximum compression position and in the maximum expansion position of the chamber.

It is also possible to provide the restraint in an expansion position and a compression position beyond these extremums as needed.

It is also possible to provide the restraint in a single expansion or compression position. The weight can then be used to achieve additional support during compression or during expansion, particularly in the case of a vertically disposed cylinder.

In the following figures, the servo mechanism coordinating the movements of the piston and the associated displacer has not been shown for the sake of clarity. The same references are used to designate the same elements.

FIG. 5 represents an example of a retaining mechanism exerting an action directly on the scanner 11 of the engine 1b. The pusher 25 exerts an elastic thrust on a ramp 8 integral with the shaft 12 itself secured to the displacer 11.

The ramp 8 comprises a straight portion on which the pusher 25 passes during a change of position of the engine lb. The ramp 8 terminates at both ends by two inclined slopes determined to achieve a specific elastic restraint.

Figure 6 shows an example of a retaining mechanism exerting an action directly on the piston of a motor. The pusher 25 exerts an elastic thrust on a ramp integral with the piston 2. The ramp also comprises a straight portion on which the pusher 25 passes during a change of position of the engine. The ramp also ends at both ends by two slopes inclination determined according to the elastic restraint to exercise.

Of course, several elastic retaining mechanisms can exert their action on the piston, the displacer or the servo mechanism in the same motor retaining position.

FIG. 7 represents an example of boiler 52 to cogeneration comprising a motor the heater 4 of which feeds a heating circuit.

The boiler 52 includes a water circuit 40 supplying an appliance 42 such as a domestic heater. The water in the circuit 40 is for example circulated by a pump 41. The water passes through a water heater 33 and is then distributed to the apparatus 42. The water heater 33 comprises an inlet 37 heating circulating between baffles 39 before exiting through a vent orifice 38. A coil 44 is disposed against the baffles 39 in the water heater and is further connected to the water circuit 40.

The heater 4 of the engine is for example heated by a burner 35 fed by a supply of gas 34. The hot gases after passing through the heater 4 are discharged to the inlet 37 of the water heater 33.

The cooler 5 is also equipped with fins 43 for cooling the heat dissipating in the surrounding air around the boiler 52.

In addition, the motor drives a device generating electricity. The shaft 12 drives for example a magnet 56 movable in translation in a coil 55 supplying electricity to a device 57. Of course the drive in translation can also be performed by the piston. One can also provide the drive of a mechanism comprising a flywheel.

FIGS. 8 to 10 represent different views of one and the same elastic retaining mechanism exerting an action on a shaft 61. The action is exerted on a solid shaft 61 such that the shaft 12 integral with the displacer 11 previously described but of course the mechanism is applied in the same way to a hollow shaft such as the piston 2 previously described.

As shown in Figure 8, the shaft 61 comprises a plurality of ramps 62 and 63 distributed over its periphery and extending longitudinally over a predetermined length of the shaft 61. The successive ramps 62 and 63 are reversed. The shaft 61 here comprises six ramps.

The shaft 61 is movably disposed in translation in a longitudinal central housing 77 of the body 65 of the elastic retention mechanism. The body 65 of the elastic retaining mechanism is intended to be integral with the cylinder of a motor.

The body 65 comprises radial housings extending from its periphery to the longitudinal central housing 77 to each receive a ball 66a or 66b pushed by a spring 67a or 67b otherwise maintained by a shim 68a or 68b.

Crowns 70 and 69 are arranged around the body 65. Each ring is movable in translation relative to the body 65. For this purpose each ring comprises an internal pin 79 or 80 cooperating with a longitudinal groove 78 or 81 of the body 65. The groove 81 is in particular visible in FIG. 9. Each ring comprises holding plates for the holds.

Two rings 71 and 72 are screwed around the body 65 to bear each against a ring.

A first set of balls 66a is intended to cooperate with a first set of ramps 63 of the shaft 61 and a second set of balls 66b is intended to cooperate with a second set of ramps 62 of the shaft 61. Each of these sets here includes three balls. The sets of balls are arranged in two planes offset longitudinally with respect to the central housing 77.

As shown in section in FIG. 9 along a section plane passing through the center of the balls of the first set, each radial housing comprises a portion 73 of circular section opening into the central passage extended by an enlarged portion 75 of rectangular section emerging at the periphery of the body 65. The portion 73 of circular section receives a ball 66a while the portion 75 of rectangular section receives a shim 68a of corresponding section. A spring 67a is disposed between a ball 66a and a shim 68a. A housing is made in each shim 68a on its inner face to receive an end of the spring 67a.

Each shim 68a also comprises an external face inclined towards a plate of the ring 69. The pads a crown are also inclined at the same inclination as the wedges with which they cooperate. It is thus understood that by moving longitudinally a ring gear 69, it settles the depression of the wedges 68a in their housing 75. The bearing force of the spring is thus more or less important. Advantageously, this adjustment makes it possible to adjust the retaining force but also to compensate for wear of the balls or ramps or weakening of the spring.

A narrowing 82 may be provided at the end of the portion 73 of circular section opening into the central housing. This constriction 82 allows the balls 66a to be held in their housing 73.

As shown in FIG. 10, the two sets of balls 66a and 66b are pushed towards the shaft 61 with an adjustable definable force. The adjustment in position of the screwed rings 71 and 72 makes it possible to position the rings 69 and 70 to drive more or less the shims 68a and 68b in their housing 75 or 76 rectangular. The holding force exerted by the balls 66a and 66b can thus be adjusted.

The first set of balls 66a carries the restraint on a steeply inclined portion of the ramps 63.

The second set of balls 66b exerts restraint on a steeply inclined portion of the ramps 62.

Each ramp comprises a portion of steep inclination and a portion extending gently down the entire length L64 of the ramp. The length L64 of the ramps corresponds to the longitudinal displacement of the shaft 61 between two elastic retaining positions.

The shaft 61 comprises pairs of ramps extending longitudinally and arranged radially opposite one another. The positions of the two opposite ramps are reversed, so that the steep slopes are arranged at a determined distance L64 from each other.

Thus, while a set of balls 66b is facing a gentle slope, the other set of balls 66a comes opposite a slope of steep slope achieving an elastic restraint and then a sudden release of the shaft. Slope soft also allows a gradual slowdown to the other restraint position.

It should be obvious to those skilled in the art that the present invention allows other embodiments. Therefore, the present embodiments should be considered as illustrating the invention.

Claims

An external combustion engine (1) comprising at least:

a cylinder (3) having a closed end (10),

a piston (2) movable in the cylinder (3) delimiting a chamber (6) filled with a gaseous fluid,

- a displacer (11) slidably unsealed in the cylinder (3) and moved by a drive member (12),

at least one heater (4) of a hot zone (10) of the cylinder (3) and at least one cooler (5) of a cold zone (14) of the cylinder (3),

at least one mechanism (20, 21, 22) for controlling the translational movement of the piston (2) with respect to the displacer (11) so that the displacer (11) is at least partly screwed to -vis of said cold zone (14) in a first compression position of the chamber (6) and comes at least partly opposite said hot zone

(10) in a second expansion position of the chamber (6),

characterized in that it comprises an elastic retaining mechanism (23 to 27) exerting at least a first elastic retention of the piston (2) in said first position or a second elastic retention of the piston (2) in said second position.

2. Engine (1) according to claim 1, characterized in that said first position of the piston (2) corresponds to a maximum compression position of the chamber (6) and said second position of the piston (2) corresponds to a position d maximum expansion of the chamber (6).

3. Engine (1) according to claim 1 or 2, characterized in that in said second position the displacer (11) comes entirely vis-à-vis the hot zone (10).

4. Motor (1) according to one of claims 1 to 3, characterized in that in said first position the displacer (11) comes entirely vis-à-vis the part of the cold zone (14) in front of the piston (2).

5. Motor (1) according to one of claims 1 to 4, characterized in that the driving member of the displacer

(11) comprises a shaft (12) connected to the displacer and sliding sealingly through the piston (2), the servo mechanism comprising a rotatable member (22) for driving a first connecting rod (20) connected to the shaft (12) and a second connecting rod (21) connected to the piston (2).

6. Motor (1) according to claim 5, characterized in that the elastic retaining mechanism exerts a mechanical action on a member (8) integral with the shaft (12) driving the displacer (11) to exercise at least said first elastic retainer or said second elastic retainer.

7. Motor (1) according to one of claims 1 to 6, characterized in that the elastic retaining mechanism exerts a mechanical action on the servo mechanism (20, 21, 22) for exerting at least said first elastic retainer or said second elastic restraint.

8. Motor (1) according to one of claims 1 to 7, characterized in that the elastic retaining mechanism exerts a mechanical action on an integral member of the piston (2) for exerting at least said first elastic restraint or said second restraint. elastic.

9. Motor (1) according to one of claims 1 to 8, characterized in that the> resilient retaining mechanism comprises at least one pusher (25) and a spring (26) disposed between the pusher and its support (27) and a portion forming at least a first ramp having a first inclination determined so as to exert a determined retention of the pusher (25), this portion being integral with the servo mechanism, the piston (2) or the displacer (11) .

10. Motor (1) according to claim 9, characterized in that said portion comprises a second ramp extending said first ramp, the second ramp having a second inclination less than said first inclination, the second inclination being determined so as to slow down progressive portion of said portion.

11. Motor (1) according to one of claims 1 to 10, characterized in that the elastic retaining mechanism comprises a member (28) for adjusting the retaining force exercised.

12. Cogeneration boiler (52) producing electricity by means of a motor (1) according to one of claims 1 to 11 for driving at least one core (56) with respect to at least one coil (55) current generator.