EP0594870B1 - Driving motor - Google Patents

Description

The present invention relates to a control motor, in particular for servo valves, according to the preamble of patent claim 1.

Such a generic control motor is known for example from DE-A-3501836 and is preferably used to actuate a hydraulic pilot stage of a servo valve. The control motor comprises an armature movable between two pole means. The pole means carry electrical control coils to influence the magnetic field generated by a permanent magnet in the armature space. It is considered a disadvantage of this control motor that two control coils are required to move the armature. On the one hand, a control circuit for the excitation of the coils must be provided, which leads to an increased space requirement, on the other hand, this control motor consists of many parts, has a complicated structure and is unreliable in operation, since the failure of a component can already lead to a malfunction of the overall system .

DE-B-1 282 402 discloses a solenoid valve with a piston which can be displaced axially between two operating positions by magnetic force. The valve has two outer legs which carry permanent magnets and an electromagnetic control coil arranged between the legs.

The present invention has for its object to provide a control motor that is simple in construction and reliable in operation.

This object is achieved according to the present invention by a control motor with the features of claim 1.

In the control motor according to the present invention, the pole means are arranged so that the first pole means, between which the pivotable armature is spring centered is held, wear the permanent magnets. The second pole means is provided with at least one control coil, so that the construction of the control motor is very simple. Furthermore, the arrangement of pole means and control coils according to the invention enables the movement of the armature to be controlled precisely and at a higher frequency than was possible with the control motors in the prior art, because the armature has a smaller mass than in conventional control motors. With the control motor constructed according to the invention, valves with higher dynamics can also be controlled.

Furthermore, the side walls can be fastened on the base body so as to be displaceable. By moving the side walls, the working air gaps between the first pole means and the armature can be adjusted in a simple manner.

In a preferred embodiment, the foot parts have at least one vertical through-hole through which a fastening screw is inserted and screwed into the base body. The through hole has a larger diameter than the diameter of the fastening screw, so that the L-shaped side walls can be moved within the play between the through hole and the fastening screw. With such a construction, a rough adjustment of the working air gaps is structurally predetermined and a fine adjustment can be carried out particularly easily afterwards.

The upper ends of the two side walls are preferably connected to one another via a T-shaped closure part, so that the vertical central bar of the closure part provided with at least one coil faces the upper surface of the anchor. A so-called construction air gap is formed between the T-shaped closure part and the armature. The construction air gap allows the armature to move freely within the working air gap. A closed magnetic circuit is formed over the closure part for the two side walls, which leads to an intensification of the magnetic field generated by the permanent magnets in the working air gaps. The magnetic field generated electromagnetically by the second pole means is additionally coupled into this magnetic circuit via the vertical center bar.

In an advantageous embodiment, the two outer ends of the closure part have vertical through bores or slots, through which a fastening screw is inserted and screwed into the side wall. The through holes in turn have a larger diameter than the diameter of the fastening screw. Analogous to the transverse displaceability of the L-shaped side walls, the T-shaped closure part in this embodiment is also very easy to adjust in that it can be moved laterally.

In an advantageous embodiment there are spacer plates between the two outer ends of the closure part and the upper ends of the side walls for adjusting the construction air gap between the T-shaped closure part and the armature in the vertical direction. When using different sized spacer plates of different thickness, the T-shaped closure part in the height is adjusted, which also reduces or increases the construction air gap accordingly.

According to a preferred embodiment, the permanent magnets have pole shoes made of a magnetizable material on the end faces facing the armature. The pole pieces advantageously direct and reinforce the magnetic field in the working air gap.

In an advantageous embodiment, the permanent magnets are horizontally magnetized and consist of a material with high magnetic remanence, preferably neodymium iron or samarium cobalt. The former alloy with a high iron content is inexpensive to manufacture and has a particularly high magnetic remanence. As a result, a permanent magnet with small dimensions can be used in the control motor with the resulting low costs and space savings.

In a further advantageous embodiment of the control motor, the foot parts of the L-shaped side walls and possibly also the permanent magnets and the pole shoes have horizontal through-fit bores through which screw-shaped stops which can be moved in one direction transversely to the side walls are guided. The stops prevent direct contact between the armature and the permanent magnets or pole pieces, which could result in the armature "sticking" with maximum deflection. The stops can be adjusted from outside to adjust the required stroke of the armature even after the control motor has been started up.

The stops are preferably made of a non-magnetic material. This ensures that there are no field distortions in the working air gap.

According to a further exemplary embodiment, the horizontal through bore of the foot part of the side walls is provided with an internal thread, so that a stop provided with a corresponding external thread can be screwed into the foot part from the outside. In this embodiment, a particularly simple and safe setting of the maximum permissible deflection of the armature is possible.

In a further preferred exemplary embodiment, the vertical central bar of the T-shaped closure part has a through hole in the axial direction through which a spring rod is passed, one end of which is connected to the armature. This makes it possible to influence the zero point adjustment and the dynamics of the armature.

According to an advantageous embodiment, the other end of the spring bar is fixed to the T-shaped closure part via an adjustable clamping device. This results in an adjustable zero point adjustment of the armature, and the dynamics of the control motor are also considerably improved as a result of the elastic spring rod exerting a mechanical restoring torque on the deflected armature.

In a variant, the other end of the spring bar is connected to a displaceable actuating device. This results in a mechanical control option for the control motor, for example in the event that the electromagnetic control fails due to a defect.

In an advantageous embodiment, the anchor is fixed to the base body with two vertical bending beams which are guided parallel to one another. With this parallel bracket, the pivoting movement of the armature is only in the preferred plane possible.

According to a preferred embodiment, a control tube is pressed into the armature, at the lower end of which a jet nozzle is formed. The head tube follows the movements of the armature and controls the direction of the oil jet emerging from the nozzle.

In an advantageous embodiment, a flexible pipe pressure line is connected to the control pipe at a point near the pivot point of the armature. If a force, which is generated, for example, by the inertia of the hydraulic fluid, is transmitted to the armature in the pipe pressure line, the resulting torque at the point near the pivot point of the armature is very low. As a result, the influence of such disturbances, which would otherwise lead to incorrect movement of the armature, is reduced.

In a preferred embodiment, the head tube is sealed by means of an O-ring, which is located approximately at the pivot point of the armature. The O-ring prevents hydraulic fluid from escaping and yet, thanks to its location near the pivot point of the armature, allows it sufficient freedom of movement.

• Figur 1 zeigt einen Längsschnitt durch einen Steuermotor nach einem ersten Ausführungsbeispiel der vorliegenden Erfindung;
• Figur 2 zeigt einen Schnitt durch den Steuermotor, welcher in Figur 1 dargestellt ist entlang der Linie A-A;
• Figur 3 zeigt einen Schnitt durch den Steuermotor, welcher in Figur 1 gezeigt ist, entlang der Linie B-B;
• Figur 4 zeigt einen Längsschnitt des Steuermotors nach einem zweiten Ausführungsbeispiel der Erfindung;
• Figur 5 zeigt einen Längsschnitt des Steuermotors nach einem dritten Ausführungsbeispiel der Erfindung; und
• Figur 6 zeigt einen Längsschnitt durch den Steuermotor nach dem ersten Ausführungsbeispiel zur Verdeutlichung der magnetischen Felderverläufe.

Further advantages and details of the invention result from the following description of the preferred exemplary embodiments with reference to the attached drawings, which show:

• Figure 1 shows a longitudinal section through a control motor according to a first embodiment of the present invention;
• Figure 2 shows a section through the control motor, which is shown in Figure 1 along the line AA;
• Figure 3 shows a section through the control motor shown in Figure 1 along the line BB;
• Figure 4 shows a longitudinal section of the control motor according to a second embodiment of the invention;
• Figure 5 shows a longitudinal section of the control motor according to a third embodiment of the invention; and
• FIG. 6 shows a longitudinal section through the control motor according to the first exemplary embodiment to illustrate the magnetic field profiles.

The first exemplary embodiment of the present invention is described below with reference to FIGS. 1-3. Figure 1 shows the control motor according to the invention with an actuator 1 flanged thereon, which has two hydraulic working channels A, B on its underside. The control motor is surrounded by a housing 2 for protection against dirt and moisture. The control motor itself is constructed on a base body 3 with a round profile with a U-shaped cross section. The base body 3 has a centered through hole in the longitudinal direction, into which a sleeve 4 is fitted. A control tube 30 is inserted through the sleeve, the lower end of which projects into the actuator. The sleeve 4 also serves as a receptacle for an O-ring 31.

The control tube 30 has a central part widened in cross section. An armature 5 is connected to the control tube 30 and is essentially cuboid in shape with end faces which are bevelled symmetrically to the center. How from As can be seen in FIG. 2, the armature is additionally held by two vertical bending beams 6 aligned parallel to one another. It is also conceivable to provide a thin-walled bending tube as a resilient anchor foot instead of the parallel bending beam, as is known in the case of control motors from the prior art.

Two side walls 7, 8 with an L-shaped cross section are fastened to the U-shaped base body 3 by means of screw connections 9. A screw connection 9 is completely shown in FIG. 1 in a partially broken representation. The foot parts of the L-shaped side walls have vertical through bores, through which a screw 9 is inserted and screwed into the side wall of the base body 3.

Permanent magnets 10, 11 facing one another are fastened to the end faces of the base parts of the L-shaped side walls, for example by means of adhesive. The mutually facing sides of the permanent magnets each carry a pole piece 12, 13, between which the armature 5 is located. Working air gaps 16, 17 are formed between the pole pieces 12, 13 and the respective side surfaces of the armature 5. It can be seen from FIG. 3 that the pole shoes have a tapered cross-section on the sides facing the armature, so that the opposing longitudinal edges of the armature and the pole shoes match in terms of their position.

The foot parts of the L-shaped side walls, the permanent magnets and the pole pieces have a horizontal through-hole, into each of which a screw-shaped stop for the armature is made. The stops 14, 15 are made of a non-magnetic material and so far through the horizontal through holes that their ends facing the armature over the Pole shoes stick out. An external thread is cut into the stops 14, 15, which fits an internal thread which is formed in an outer region of the foot parts.

The upper ends of the L-shaped side walls (7, 8) are connected to one another via a T-shaped closure part 18. For this purpose, the T-shaped closure part has vertical slots or through holes, through which a fastening screw 19 is passed in each case. The through holes in the T-shaped closure part in turn have a slightly larger diameter than the outer diameter of the screws 19. Around the vertical central bar of the T-shaped closure part, one or more control coils 20 are wound, the electrical connection lines (not shown) of which are led to the outside. The central bar of the T-shaped closure member has a sufficient length so that a construction air gap 21 is formed between its lower end and the surface of the anchor. Spacer plates 22 are inserted between the upper ends of the side walls and the T-shaped closure part in order to vary the construction air gap 21 accordingly.

According to FIG. 2, the actuator 1 has a hydraulic oil pressure supply connection P and a return connection R. The supply connection P is connected via a flexible pressure line 24 to the control tube 30 pressed into the armature 5. The connection between the flexible pressure line 24 and the head tube is provided in the central region of the head tube 30, which is enlarged in cross section. The head tube 30 has at its lower end a nozzle 25 through which the hydraulic oil exits. The emerging oil jet is directed to a receiver 32 according to the nozzle-jet principle, which from a standing position is known in the art. The control tube 30 is connected in a pressure-tight manner to the base body 3 via the sleeve 4 by means of the O-ring 31 provided in the vicinity of the pivot point of the armature.

The mode of operation of the first exemplary embodiment of the present invention will now be explained with reference to FIGS. 1 to 3 and 6.

First, it is assumed that the control motor is in the idle state and the control coil 20 is de-energized. The armature 5 is in the zero position approximately in the middle between the two pole pieces 12, 13. The permanent magnets 10, 11, the arrangement of which is shown in FIG. 1, form a magnetic flux, which is symbolic with solid lines in FIG. 6 is shown.

In a magnetic circuit 36 generated by the permanent magnets, the field lines proceed from the north pole of the permanent magnet 11 shown in the left half of the figure, via the L-shaped side wall 8, the T-shaped closure part 18, the L-shaped side wall 7 to the south pole of the in the Permanent magnet 10 shown on the right half.

From the north pole of the permanent magnet 10 shown in the right half of the figure, field lines form over the pole piece 12, the air gap 16, the armature 5, the air gap 17 and the pole piece 13 to the south pole of the permanent magnet 11 shown in the left half of the picture.

In a similar way, a permanent magnetic circuit 35 closes via the base body 3. The permanent magnetic circuit 35 can also be omitted if the base body is made of non-magnetizable material.

Due to the magnetic fields, which are caused by the two permanent magnets 10, 11, there is a high magnetic induction in the two air gaps 16, 17. When the control coil 20 is not energized, this induction is of equal size in both air gaps, so that the armature 5 assumes a rest position, since the attractive forces acting on the armature in the two working air gaps 16, 17 are approximately the same size.

If an electric current now flows through the control coil 20, a magnetic field is formed, which has the course marked 37, 38 in FIG. 6. This creates a magnetic north pole at the lower end of the vertical central bar of the T-shaped closure part 18 and an opposite south pole (or vice versa) at its upper end. This gives the vertical center bar the function of a coil core for the control coil 20. The direction of this electromagnetic field is determined by the direction of the electric current.

In a first magnetic circuit 37 generated by the control coil 20, which is shown in the left half of FIG. 6, the field lines run from the magnetic north pole via the construction air gap 21, the armature 5, the working air gap 17, the pole piece 13, and the permanent magnet 11 , The L-shaped side wall 8 and the closure member 18 to the south pole of the coil core.

In a second magnetic circuit 38 generated by the control coil, which is shown in the right half of FIG. 6, the field lines run from the magnetic north pole of the coil core via the armature 5, the air gap 16. the pole piece 12, the permanent magnet 10, the L-shaped side wall 7 and the closure part 18 for the magnetic south pole of the coil core.

The magnetic field generated by the control coil increases the magnetic induction generated by the permanent magnets in the air gap 17. In contrast, the magnetic field in the right half of the picture leads to a weakening of the permanent magnet-excited magnetic induction in the air gap 16. Because of the different resulting induction, different attractive forces arise in the air gaps 16 and 17, the resultant of which causes the armature from its zero position in the direction of the arrow, i. H. pivoted to the left. The armature 5 is deflected from its zero position depending on the coil current through the control coil 20.

When the armature 5 is deflected, the elasticity of the two bending beams 6 creates a restoring force which counteracts the magnetic attraction force. The armature 5 is therefore only deflected until the magnetic attraction is in equilibrium with the restoring force of the bending beams. If the magnetic attraction force is greater than the restoring force at maximum deflection of the armature, the armature strikes the mechanical stop 14 or 15. The stop ensures that the armature does not "stick" to the pole piece, but rather returns to its zero position immediately after the coil current has been withdrawn.

It is clear to the person skilled in the art that, depending on the size of the armature 5 and the control coil 20 used, an optimal air gap between the armature 5 and the pole pieces 12, 13 must be set. The size of the armature space or the width of the air gaps 16, 17 can be determined by If the fastening screws 9, 19 are loosened, shift the L-shaped side walls accordingly. The size of the armature space, ie the maximum permissible deflection of the armature, can additionally be set via the stops 14, 15. The adjustment can be done by turning the stops in the threaded holes in the foot parts.

By moving the T-shaped closure part 18 laterally, the induction in the working air gaps 16, 17 can be influenced when the coil is not energized. In this way the zero point of the armature can be set.

When the control motor is operating, the hydraulic oil supply connection P shown in FIG. 2 is connected to the operating pressure line. The pressurized oil is introduced via the flexible pipe pressure line 24 into the control tube 30 of the armature 5 and exits through the nozzle 25 at the end of the control tube. The oil jet generated in this way follows the movement of the armature 5 in its direction. An oil jet which changes in its direction is used to control the receiver 32 of the servo valve. Similarly, the movement of the armature of the control motor according to the invention can also effect the baffle plate in a nozzle-baffle plate. Control the system.

A second embodiment of the control motor according to the invention is described below with reference to FIG. 4. The features of the control motor, which are identical to those of the first exemplary embodiment, are identified in FIG. 4 by the same reference symbols and are not described again.

Essentially, the second embodiment of the control motor according to the invention differs from the first embodiment in that a additional adjustment possibility for the anchor is provided. The vertical center bar of the T-shaped closure part 18 has a centered through hole in the direction of the longitudinal axis through which a spring rod 26 is inserted. The spring rod 26 is at its lower end with the anchor 5, for. B. connected by pressing. The upper end of the spring bar is clamped by means of a clamping device 27, which is connected to the closure part 18 via an adjusting screw 28. The spring rod has sufficient play in the centered through hole in the vertical central beam for a movement which is transmitted to the spring rod by the deflection of the armature.

According to the second exemplary embodiment, the restoring force which acts on the deflected armature has two component parts. The first component is generated by the elastic bending beam 6, as was already the case in the first embodiment. A second component is generated by the elastic spring rod 26 when the armature is deflected out of the zero point position. Since the two components of the restoring force add up, the dynamics of the armature increase, i. H. The overall rigidity of the spring mass system of the beam-armature increases, which means that the natural frequency also increases.

Furthermore, according to the second exemplary embodiment, the zero position of the armature can be changed or set. For this purpose, the adjusting screw 28 is loosened on the T-shaped closure part and the spring bar is brought into its desired position. Then the locking screw is locked. This subsequent adjustment option for the armature is advantageous in this preferred embodiment.

A third embodiment of the control motor according to the invention is shown in FIG. 5. The third embodiment differs from the second embodiment in that no clamping device for the spring bar 26, but instead an actuating device 29 is provided for the mechanical actuation of the spring bar 26. Movements of the actuating device are thus transmitted directly to the armature 5 via the spring rod 25. In this embodiment, the often required emergency manual control that intervenes in the event of a failure of the electromagnetic control is implemented. As an alternative to this, mechanical feedback can also be implemented.

It is clear to a person skilled in the art that deviations from the exemplary embodiments described above can be made without departing from the invention. For example, it is possible to provide several control coils instead of one control coil.

Claims (18)

1. Pilot motor, in particular for servo-valves, having a basic body (3) which is U-shaped in cross section and made of magnetizable material, at least two side walls (7, 8) which are fastened to the basic body and between which first pole means (10-13) are disposed, and an armature (5) capable of swivelling between the first pole means, the armature being held in a spring-centred manner in a neutral middle position between the pole means, characterized in that

   the side walls (7, 8) are disposed so as to be transversely displaceable on the basic body (3) and the first pole means comprise permanent magnets (10, 11),

   that a second pole means (18) provided with at least one control coil (20) is disposed in the region between the side walls (7, 8),

   and that in response to the activating of the control coil the armature is deflected proportionally to the control signal out of the middle position and in the non-active state of the coil the armature automatically returns into the middle position.
2. Pilot motor according to claim 1, characterized in that the side walls (7, 8) are L-shaped in cross section and each comprise a base part, said base parts being directed towards one another, and that the first pole means (10-13) are disposed at the opposing end faces of the base parts.
3. Pilot motor according to claim 2, characterized in that the base parts have at least one vertical through-hole, through which in each case one fastening screw (9) is passed and screwed into the basic body (3), the through-hole having a larger diameter than the diameter of the fastening screw (9).
4. Pilot motor according to at least one of claims 1 to 3, characterized in that the top ends of the two side walls (7, 8) are connected to one another by a T-shaped closure part (18) and that at least one coil (20) is disposed around the vertical middle beam of the T-shaped closure part (18).
5. Pilot motor according to claim 4, characterized in that the two outer ends of the closure part (18) have vertical through-holes or elongated slots, through which in each case one fastening screw (19) is passed and screwed into the side wall (7, 8), the through-holes having a larger diameter than the diameter of the fastening screws (19).
6. Pilot motor according to claim 4 or 5, characterized in that small distance plates (22) are situated between the outer ends of the closure part (18) and the top ends of the side walls (7, 8).
7. Pilot motor according to at least one of claims 1 to 6, characterized in that the permanent magnets (10, 11) on the end faces directed towards the armature (5) comprise pole shoes (12, 13) made of a magnetizable material.
8. Pilot motor according to at least one of claims 1 to 7, characterized in that the two permanent magnets (10, 11) are horizontally magnetized and are made of a material of high magnetic remanence, preferably neodymium iron or samarium cobalt.
9. Pilot motor according to at least one of claims 2 to 8, characterized in that the base parts of the L-shaped side walls (7, 8) and optionally also the permanent magnets (10, 11) and pole shoes (12, 13) have horizontal fitting through-holes, through which are passed helical stops (14, 15) which are displaceable in a direction at right angles to the side walls.
10. Pilot motor according to claim 9, characterized in that the stops (14, 15) are made of a non-magnetizable material.
11. Pilot motor according to claim 9 or 10, characterized in that the horizontal through-hole of the base part of the side walls (7, 8) has an internal thread so that a stop (14, 15) provided with a corresponding external thread may be screwed from the outside into the base part.
12. Pilot motor according to at least one of claims 4 to 11, characterized in that the vertical middle beam of the T-shaped closure part (18) has a through-hole in an axial direction, through which a spring bar (26) is passed, the bottom end of the spring bar being connected to the armature.
13. Pilot motor according to claim 12, characterized in that the top end of the spring bar (26) is fixed by means of an adjustable clamping device (27) to the T-shaped closure part (18).
14. Pilot motor according to claim 12, characterized in that the top end of the spring bar (26) is connected to a displaceable operating device (29).
15. Pilot motor according to at least one of claims 1 to 14, characterized in that the armature (5) is held in a spring-centred manner by means of two vertical bending beams (6), which extend parallel to one another, and is capable of swivelling in a preferred direction.
16. Pilot motor according to at least one of claims 1 to 15, characterized in that pressed into the armature is a control pipe (30), at the bottom end of which a nozzle (25) is formed.
17. Pilot motor according to at least one of claims 1 to 16, characterized in that a flexible pressure line (24) is connected to the control pipe (30) at a point preferably close to the centre of rotation (23) of the armature (5).
18. Pilot motor according to claim 17, characterized in that the control pipe (30) is sealed by means of an O-ring (31) which is situated approximately in the centre of rotation of the armature (5).

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