Electric drive and actuator

Abstract

The invention relates to an electric drive (1) of an actuator (100) for the field of automation technology for actuating a fitting such as a valve for example, comprising: an electric motor (10). The electric drive is characterized by having a magnetic rotation-inhibiting device (20) which is designed to inhibit the rotation of the electric motor in the static or quasi-static state by means of a detent torque, the rotation-inhibiting device (20) providing, when the speed of the electric motor (10) is above a threshold in the dynamic state, a detent torque of less than 5 percent, in particular less than 1 percent, preferably less than 0.2 percent, of the detent torque in the static or quasi-static state.

Description

[0001] Electric drive and actuator

[0002] The invention relates to an electric drive for an actuator in automation technology and such an actuator.

[0003] Electrically driven actuators are known, as can be seen, for example, in W02013004360A2. Such actuators typically exhibit a mechanical self-locking or self-braking mechanism, which must be overcome when the actuator is actuated. This has the advantage of providing a high holding torque, so that the actuator remains in its position after actuation. However, it has the disadvantage of increased energy consumption and mechanical wear during actuation.

[0004] The object of the invention is to propose an electric drive for an actuator and an actuator which has low energy consumption, low wear and high holding torque.

[0005] The problem is solved by an electric drive according to independent claim 1 and by an actuator according to independent claim 14.

[0006] An electric drive of an actuator in automation technology for actuating a fitting such as a valve comprises an electric motor; wherein the electric drive has a magnetic rotation-locking device which is configured to keep the electric motor in a static or quasi-static state.

[0007] to inhibit the rotation of a state with a cogging torque, wherein the rotation inhibiting device in an electric motor in a dynamic state above a first limiting speed has a braking torque of less than 5 percent, and in particular less than 1 percent, and preferably less than 0.2 percent of the cogging torque.

[0008] By releasing the magnetic coupling of the rotational locking device when the first limit speed is exceeded, a high cogging torque and very low mechanical resistance during actuator operation can be achieved. From a practical standpoint, the magnetically mediated braking torque can be reduced to zero.

[0009] In one embodiment, the electric drive is designed to transition to a static state when the following conditions are met: a rotor speed falls below a second limiting speed smaller than the first limiting speed, and a load torque is smaller than the maximum cogging torque.

[0010] In one embodiment, the rotational inhibiting device comprises the following: a rotor dynamically, and in particular statically, coupled to the electric motor, and a stator; a magnetic body with a surface that is in particular rotationally symmetric, in particular a rotationally symmetric magnetic body, wherein the magnetic body is arranged coaxially to the stator; at least one rotating element which is carried along with the rotor and which orbits the surface of the magnetic body in a cross-sectional plane through the magnetic body, wherein the at least one rotating element is magnetically attracted to the magnetic body; at least one track-forming element which is arranged on the surface of the magnetic body and which forces the rotating element to a minimum radial distance to the magnetic body section by section on an orbit and has a maximum height with respect to the surface.

[0011] At a first critical speed, a centrifugal force caused by the carrying motion on the rotating element outweighs the magnetic attraction between them.

[0012] The rotating element and the magnetic body reach their maximum height. Above the limiting speed, the mechanical resistance of the actuator is therefore very low; below the limiting speed, the motor must be driven to overcome the cogging torque, which arises from the interaction of the rotating element and the path-forming element. At the first limiting speed, there is therefore an absolute equality of the magnetic attraction force between the magnetic body and the rotating element and the centrifugal force.

[0013] When the second limiting speed is undershot, the centrifugal force acting on the rotating elements becomes less than the magnetic attraction force when there is no contact with the magnet body or track element, causing the rotating elements to re-establish contact with the magnet body and / or track elements. If the load torque applied to the drive is less than the maximum cogging torque, the rotational energy of the drive is reduced until the drive enters a static state.

[0014] The magnetic body can be, for example, a permanent magnet, or a component of an electromagnet and magnetizable, for example, by a magnetic coil. The magnetic body is designed to exert a magnetic force on the rotating element.

[0015] A rotor dynamically coupled to an electric motor can, for example, be connected to the electric motor via a gearbox or via a shared shaft. A rotor statically connected to an electric motor is not connected to the electric motor via a gearbox; relative to a reference frame of the rotor or electric motor, both behave statically.

[0016] In one embodiment, a guiding device is provided to guide at least the rotating element, wherein the guiding device has a radially extending guide for each rotating element in which the respective rotating element is at least partially arranged, wherein the guiding device is formed by the rotor or is coupled to the rotor.

[0017] The radially extending guide can be, for example, a blind hole or a bore, which is subsequently closed externally, for instance, by means of a closure. The closure can be, for example, a ring such as a metal or plastic ring, which encircles or spans a body of the guiding device. The closure can also be achieved by potting or bonding.

[0018] In one embodiment, the at least one track-forming element is formed by the stator, in particular wherein the magnetic body is formed by the at least one

[0019] The track forming element is fixed radially and / or axially and / or tangentially.

[0020] In one embodiment, the circulation element is spherical.

[0021] In this way, the rotating element can roll along its path of movement. This minimizes wear.

[0022] In one embodiment, the rotating element is cylindrical, wherein a cylinder axis runs parallel or radially to a stator axis, wherein an alignment of the cylinder axis is maintained by the guiding device.

[0023] With a parallel alignment of the cylinder axis, the rotating element can roll along its movement, which reduces wear.

[0024] With a radial orientation of the cylinder axis, the rotating element can be held stably in the guide, with a tip facing the stator being designed to slide along its direction of movement over the at least one track forming element and, if necessary, the stator at a rotational speed less than the limiting rotational speed.

[0025] In one embodiment, at least one path shape element is symmetrical with respect to a longitudinal section plane through the magnetic body.

[0026] In this way, it can be achieved that in both directions of rotation of the electric motor there is an identical transition between cogging torque and actuation.

[0027] In one embodiment, upon the presence of a first point of contact between the circulation element and

[0028] With a guide device and a second point of contact between the circumferential element and the path forming element, a first tangent plane passes through the first point of contact and parallel to the stator axis, and a second tangent plane passes through the second point of contact and parallel to the stator axis, wherein the first tangent plane and the second tangent plane form a line of intersection.

[0029] The contact points define a contact plane parallel to the stator axis.

[0030] The stator axis and the line of intersection are located on the same side of the plane of contact.

[0031] This ensures that the circulation element is not pressed against the web forming element or clamped by the guiding device and the web forming element.

[0032] In one embodiment, the small angle of intersection between the first tangent plane and the second tangent plane is at least 1 degree, and in particular at least 5 degrees, and preferably at least 10 degrees and / or at most 30 degrees, and in particular at least 20 degrees, and preferably at least 15 degrees.

[0033] This ensures that the rotating element can be easily carried along by the guide device.

[0034] In one design, contact between

[0035] A first attractive force exists between the rotating element and the magnetic body, wherein a second attractive force exists at a distance between two nearest points of the rotating element and the magnetic body of a maximum height, wherein the second attractive force is less than 50%, and in particular less than 30%, and preferably less than 20% of the first attractive force.

[0036] This allows a limiting rotational frequency to be set or limited. The limiting frequency is the rotational frequency at which the centrifugal force acting on the rotating elements outweighs the magnetic attraction between the rotating elements and the magnet body.

[0037] In one embodiment, the circumferential element has a radius, where the radius is larger than the maximum height.

[0038] In one embodiment, the at least one rotating element is ferromagnetic and, in particular, soft magnetic.

[0039] An actuator according to the invention for automation technology for actuating a fitting such as a valve comprises: an electric drive according to one of the preceding claims for generating a force or torque; an output for actuating the fitting; a gearbox for transmitting the force or torque to the output; an electronic operating circuit for operating the drive; a housing arrangement with at least one housing chamber in which the drive, the gearbox, the output and the electronic operating circuit are arranged.

[0040] The invention is described below using exemplary embodiments.

[0041] Fig. 1 schematically shows an exemplary electric drive according to the invention;

[0042] Figs. 2 a) and 2 b) show an exemplary embodiment of a rotational locking device according to the invention for an electric drive shown in Fig. 1;

[0043] Fig. 3 shows an exemplary embodiment of a circulation element according to the invention;

[0044] Fig. 4 shows geometric boundary conditions with respect to the rotational inhibiting device;

[0045] Fig. 5 shows an actuator with an electric drive according to the invention.

[0046] Fig. 1 schematically depicts an exemplary electric drive 1 according to the invention for an actuator in automation technology, wherein the actuator is configured, for example, to actuate a fitting such as a valve. The electric drive comprises an electric motor 10 and a rotational braking device 20 mechanically coupled to it, which is configured to brake the electric motor in a static or quasi-static state with a cogging torque, and, in a dynamic state above a limiting speed, to provide a braking torque of less than 5 percent, and in particular less than 1 percent, and preferably less than 0.2 percent of the cogging torque. By utilizing magnetic effects, an electric drive for an actuator can be provided which exhibits high efficiency in operation with low mechanical losses and low mechanical wear.

[0047] Figures 2a) and 2b) show an exemplary embodiment of the rotational locking device according to the invention, comprising a rotor 21 dynamically coupled to the electric motor 10, and a stator 22. The stator surrounds a magnetic body 23, which has a rotationally symmetric surface 23.1, as shown here, and is in particular rotationally symmetric. Furthermore, the rotational locking device exemplarily includes three rotating elements 24, which are carried along by the rotor 21 so that they rotate around the surface of the magnetic body when the electric motor is moving. According to the invention, the at least one rotating element 24 is attracted by the magnetic body and comprises, for example, a ferromagnetic material, and in particular a soft magnetic material.

[0048] At least one track-forming element 25, such as three track-forming elements shown here, is configured to influence the movement of the rotating element 24 around the outer surface of the magnet body in sections and to enforce a minimum radial distance to the outer surface. In a stationary / static electric motor (Fig. 2a), the rotating elements adhere to the magnet body and are prevented by the track-forming elements from moving tangentially to the outer surface, since releasing the rotating elements from the outer surface would require acting against the attractive force between the rotating element and the magnet body. In this way, a cogging torque is generated by the exemplary embodiment according to the invention. When the electric motor is switched on, the torque generated by the motor becomes sufficiently large above a certain motor current to release the rotating elements from the magnet body.Upon reaching a limiting speed, the centrifugal force acting on the rotating elements becomes greater than the attractive force between the rotating element and the magnetic body, causing the rotating elements to move away from the influence of the path-forming elements. In this way, a braking torque of less than 5 percent, and in particular less than 1 percent, and preferably less than 0.2 percent of the cogging torque is established. From a practical point of view, the braking torque in this state can be considered zero.

[0049] The magnetic body can be, for example, a permanent magnet, or a component of an electromagnet and magnetizable, for example, by a magnetic coil. The magnetic body is designed to exert a magnetic attraction on the rotating body.

[0050] Such permanent magnets can, for example, have typical material combinations such as aluminum-nickel-cobalt or neodymium-iron-boron.

[0051] An electromagnetically magnetizable magnetic body can, for example, consist of a soft magnetic material such as iron, low-carbon steels, or alloys of iron with nickel or cobalt.

[0052] As shown in Figs. 2 a) and 2 b), a guiding device 26 can be configured to guide at least the rotating element 24, wherein the guiding device has a radially extending guide 26 . 1 for each rotating element, in which the respective rotating element 24 is at least partially arranged, wherein the guiding device 26 is formed by the rotor 21 or is coupled to the rotor.

[0053] A body training the guides 26.1

[0054] The guide device can be formed in one piece or comprise several joined parts. The radially extending guide 26.1 can, for example, be blind-hole or a bore, which bore is subsequently closed externally, for example, by means of a closure. The closure can, for example, be formed by means of a ring, such as a metal ring or plastic ring, which encircles or spans a body of the guide device. The closure can also be formed by potting or bonding.

[0055] The recirculating elements can be, for example, spherical (Figs. 2a) and 2b)) or cylindrical, with a cylinder axis running parallel (Figs. 2a) and 2b)) or radially (Fig. 3) to a stator axis. In the embodiment shown in Fig. 3, the recirculating element is designed to slide along the track-forming element and the outer surface upon contact; otherwise, a rolling motion is also possible.

[0056] The at least one track-forming element 25 can be formed by the stator 22 as shown here, wherein the magnetic body 23 can be fixed radially and / or axially and / or tangentially by the at least one track-forming element 25. This enables a spatially compact design of the rotation-locking device.

[0057] The at least one track-forming element 25 can be symmetrical with respect to a longitudinal section plane through the stator or magnet body, as shown here. In this way, the effect of the rotation-stopping device can be designed to be the same for both directions of rotation.

[0058] Fig. 4 sketches geometric boundary conditions for the embodiments of Figs. 2 a), 2 b) and 3.

[0059] If there is a first point of contact Bl between the circumferential element 24 and the guide device 26 and a second point of contact B2 between the circumferential element and the path forming element, a first tangent plane TI passes through the first point of contact and parallel to the stator axis, and a second tangent plane T2 passes through the second point of contact and parallel to the stator axis, wherein the first tangent plane and the second tangent plane form a line of intersection SG.

[0060] The contact points Bl and B2 span a contact point plane BE parallel to the stator axis 22 . 1 on .

[0061] The stator axis 22 . 1 and the line of intersection SG are located on the same side of the plane of contact BE .

[0062] In this way it is ensured that the circulation element is not clamped between the guide device and the track forming element 25, since with respect to a direction of movement of the circulation element the point of contact Bl is then arranged behind a geometric center of gravity of the circulation element, and thus can push the circulation element in front of it.

[0063] In one embodiment, the small angle of intersection between the first tangent plane and the second tangent plane is at least 1 degree, and in particular at least 5 degrees, and preferably at least 10 degrees and / or at most 30 degrees, and in particular at least 20 degrees, and preferably at least 15 degrees. In one embodiment, upon contact between

[0064] A first attractive force exists between the rotating element 24 and the magnetic body 23, wherein a second attractive force exists at a distance between two nearest points of the rotating element and the magnetic body of a maximum height, wherein the second attractive force is less than 50%, and in particular less than 30%, and preferably less than 20% of the first attractive force. For example, the limiting rotational speed can be adjusted by adjusting the ratio of the first attractive force to the second attractive force.

[0065] For example, the circulation element 24 can have a radius greater than the maximum height. This ensures that the circulation element is guided securely and robustly by the guiding device and prevents the circulation element from becoming jammed.

[0066] The maximum cogging torque provided by the device is significantly influenced by the product of the attractive force between the rotating element and the magnet body and the sine of a helix angle. The helix angle is defined by the interior angle between the tangent plane T2 and a normal to a second radial plane R2, which passes through the stator axis 22.1 and the contact point B2. A first radial plane RI passes through the stator axis 22.1 and the first contact point Bl.

[0067] At a small helix angle, little work per rotation angle is required, which is associated with a low cogging torque; conversely, at a large helix angle, a large amount of work per rotation angle is required. Fig. 5 shows an exemplary actuator 100 according to the invention with a housing arrangement 5, comprising a housing 5.1 in which an electric drive 1, an output 3, a gearbox 2, and an electronic operating circuit 4 are arranged. The electric drive is configured to generate a torque that is transmitted via the gearbox to the output and converted into a linear or rotary motion. The output is configured to actuate an actuator of a valve.

[0068] / Reference list

[0069] Reference symbol list

[0070] 1 Electric drive

[0071] 2 gearboxes, 3 outputs

[0072] 4 electronic operating circuit

[0073] 5 Housing arrangement

[0074] 5.1 Housing

[0075] 10 Electric motor 20 Rotational locking device

[0076] 21 Rotor

[0077] 22 Stator

[0078] 22.1 Stator shaft

[0079] 23 Magnet body 23 . 1 Surface area

[0080] 24 circulation element

[0081] 25 Track element

[0082] 25.1 Maximum height

[0083] 25. 2 opposite surface 26 With guide device

[0084] 26.1 Leadership

[0085] 100 actuators

[0086] First point of contact

[0087] B2 second point of contact BE point of contact plane

[0088] RI first radial plane

[0089] R2 second radial plane

[0090] SG cut straight

[0091] TI first tangent plane T2 second tangent plane

[0092] / Claims

Claims

Claims 1. Electric drive (1) of an actuator (100) for automation technology for actuating a fitting such as a valve, comprising: an electric motor (10); characterized in that the electric drive has a magnetic rotation inhibiting device (20) which is configured to inhibit the rotation of the electric motor in a static state up to a maximum cogging torque, wherein the electric drive is configured to transition non-destructively from the static state to a dynamic state when the cogging torque is exceeded, wherein the rotation inhibiting device (20) has a braking torque of less than 5 percent, and in particular less than 1 percent, and preferably less than 0.2 percent of the cogging torque when the electric motor (10) is in a dynamic state above a first limiting speed.

2. Electric drive according to claim 1, wherein the electric drive (1) is configured to transition to the static state when the following conditions are met: a rotor speed falls below a second limiting speed smaller than the first limiting speed, and a load torque is smaller than the maximum cogging torque.

3. Electric drive according to claim 1 or 2, wherein the rotation-locking device (20) comprises: a rotor (21) dynamically, and in particular statically, coupled to the electric motor (10), and a stator (22); a magnetic device with a magnetic body (23) having a rotationally symmetrical outer surface (23.1), preferably a rotationally symmetrical magnetic body, wherein the magnetic body is arranged coaxially to the stator (22); at least one rotating element (24) which is carried along with the rotor (21) and orbits the outer surface (23.1) of the magnetic body (23) in a cross-sectional plane through the magnetic body, wherein the at least one rotating element (24) is magnetically attracted to the magnetic body (23); at least one track-forming element (25) which is arranged on the outer surface and guides the rotating element section by section along an orbit to a distance from the The lateral surface (23.1) is forced and has a maximum height (25.1) with respect to the lateral surface (23.1).

4. Electric drive according to claim 3, wherein a guiding device (26) is configured to guide the at least rotating element (24), wherein the guiding device has a radially extending guide (26.1) for each rotating element in which the respective rotating element (24) is at least partially arranged, wherein the guiding device (26) is guided by the rotor (21) is formed, or is coupled to the rotor.

5. Electric drive according to one of claims 3 or 4, wherein the at least one track forming element (25) is formed by the stator (22), in particular wherein the magnet body (23) is fixed radially and / or axially and / or tangentially by the at least one track forming element (25).

6. Electric drive according to one of claims 3 to 5, wherein the rotating element (24) is spherical.

7. Electric drive according to one of claims 3 or 5, wherein the rotating element (24) is cylindrical, wherein a cylinder axis runs parallel or radially to a stator axis (22.1), wherein an alignment of the cylinder axis is maintained by the guiding device (26).

8. Electric drive according to one of claims 3 to 7, wherein the at least one path forming element (25) is symmetrical with respect to a longitudinal section plane through the magnetic body (23).

9. Electric drive according to one of claims 3 to 8, wherein, in the presence of a first contact point (Bl) between the rotating element (24) and the guiding device (26) and a second contact point (B2) between the rotating element and the path forming element, a first tangential plane (TI) is formed by the first point of contact and runs parallel to the stator axis, and a second tangent plane (T2) runs through the second point of contact and parallel to the stator axis, wherein the first tangent plane and the second tangent plane form a line of intersection SG, wherein the points of contact Bl and B2 span a plane of contact BE parallel to the stator axis 22 . 1, wherein the stator axis 22 . 1 and the line of intersection SG are on the same side of the plane of contact BE.

10. Electric drive according to claim 9, wherein a small angle of intersection between the first tangential plane and the second tangential plane is at least 1 degree, and in particular at least 5 degrees, and preferably at least 10 degrees and / or at most 30 degrees, and in particular at least 20 degrees, and preferably at least 15 degrees.

11. Electric drive according to one of claims 6 to 10, wherein a first attractive force is present upon contact between the rotating element (24) and the magnetic body (23), wherein at a distance between two nearest points of A second attractive force is present between the rotating element and the magnetic body of a maximum height, wherein the second attractive force is less than 50%, and in particular less than 30%, and preferably less than 20% of the first attractive force.

12. Electric drive according to one of claims 3 to 11, wherein the rotating element (24) has a radius, the radius being greater than the maximum height.

13. Electric drive according to any one of the preceding claims 3 to 12, wherein the at least one rotating element (24) is ferromagnetic and in particular soft magnetic.

14. Actuator (100) for automation technology for actuating a fitting such as a valve, comprising: an electric drive (1) according to one of the preceding claims for generating a force or torque; an output (2) for actuating the fitting; a gearbox (3) for transmitting the force or torque to the output (2); an electronic operating circuit (4) for operating the drive; a housing arrangement (5) with at least one housing (5.1) in which the drive, the gearbox, the output, and the electronic Operating circuits are arranged. 5 / Summary

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