Electric drive and actuator

Abstract

The invention relates to an electric drive (1) of an actuator (100) for automation technology for actuating a fitting such as a valve, comprising: an electric motor (10); characterized by the fact that the electric drive has a magnetic rotation-locking device (20) which is configured to lock the electric motor in its rotation in a static or quasi-static state with a cogging torque, wherein the rotational locking device (20) in a dynamic state above a limiting speed has a cogging torque of less than 5 percent, and in particular less than 1 percent, and preferably less than 0.2 percent of the cogging torque.

Description

[0001] The invention relates to an electric drive for an actuator in automation technology and such an actuator.

[0002] Electrically driven actuators are known, as can be seen, for example, in WO2013004360A2. 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.

[0003] 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.

[0004] The problem is solved by an electric drive according to independent claim 1 and by an actuator according to independent claim 13.

[0005] An electric drive of an actuator in automation technology for operating a fitting such as a valve comprises an electric motor; wherein the electric drive has a magnetic rotation-locking device which is designed to lock the electric motor in its rotation in a static or quasi-static state with a cogging torque, wherein the rotational braking device in an electric motor in a dynamic state above a 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.

[0006] By releasing the magnetic coupling of the rotational locking device when the 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.

[0007] In one embodiment, the rotational locking device has the following features: a rotor and a stator that are dynamically and, in particular, statically coupled to the electric motor; a permanent magnet with a rotationally symmetric surface, in particular a rotationally symmetric permanent magnet, wherein the permanent magnet is arranged coaxially to the stator; at least one rotating element which is carried along with the rotor and rotates around the outer surface of the permanent magnet in a cross-sectional plane through the permanent magnet, wherein the at least one rotating element is magnetically attracted by the permanent magnet; at least one track-forming element which is arranged on the lateral surface of the permanent magnet and forces the orbiting element on an orbit section by section to a radial minimum distance to the permanent magnet and has a maximum height with respect to the lateral surface.

[0008] At a critical speed, the centrifugal force exerted on the rotating element by the movement of the permanent magnet outweighs the magnetic attraction between the rotating element and the permanent magnet when the maximum height is reached. Above the critical speed, the mechanical resistance of the actuator is therefore very low; below the critical speed, the motor must be driven to overcome the cogging torque resulting from the interaction of the rotating element and the path forming element. At the critical speed, the absolute values ​​of the magnetic attraction between the permanent magnet and the rotating element and the centrifugal force are thus equal.

[0009] A rotor dynamically coupled to an electric motor can be connected to it, for example, via a gearbox or a shared shaft. A rotor statically connected to an electric motor is not connected via a gearbox; relative to a reference frame of reference for the rotor or electric motor, both behave statically.

[0010] In one embodiment, a driving device is arranged to drive the at least rotating element, wherein the driving device has a radially extending guide for each rotating element in which the respective rotating element is at least partially arranged. wherein the carrying device is formed by the rotor, or is coupled to the rotor.

[0011] 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 that grips or clamps a body of the guiding device. The closure can also be achieved by potting or bonding.

[0012] In one embodiment, the at least one track forming element is formed by the stator,

[0013] in particular wherein the permanent magnet is fixed radially and / or axially and / or tangentially by the at least one track forming element.

[0014] In one embodiment, the rotating element is spherical.

[0015] In this way, the rotating element can roll along its path of movement. This minimizes wear.

[0016] 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 according to

[0017] With a parallel alignment of the cylinder axis, the rotating element can roll along its movement, which reduces wear.

[0018] 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 arranged to slide along its direction of movement over the at least one path forming element and, if necessary, the stator at a rotational speed less than the limiting rotational speed.

[0019] In one embodiment, at least one track element is symmetrical with respect to a longitudinal section plane through the permanent magnet.

[0020] 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.

[0021] In one embodiment, when there is a first point of contact between the rotating element and the driving device and a second point of contact between the rotating element and the path forming element, a first tangential plane runs through the first point of contact and parallel to the stator axis, and a second tangential plane runs through the second point of contact and parallel to the stator axis, wherein the first tangential plane and the second tangential plane form a line of intersection.

[0022] The contact points define a contact plane parallel to the stator axis.

[0023] The stator axis and the line of intersection are located on the same side of the plane of contact.

[0024] 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.

[0025] 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.

[0026] This ensures that the rotating element can be easily carried along by the carrying device.

[0027] In one embodiment, a first attractive force exists upon contact between the rotating element and the permanent magnet. where a second attractive force exists when the distance between two nearest points of the rotating element and the permanent magnet is 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.

[0028] This allows a limiting rotational speed to be set or limited. The limiting frequency is the rotational speed at which the centrifugal force acting on the rotating elements outweighs the magnetic attraction between the rotating elements and the permanent magnet.

[0029] In one embodiment, the circumferential element has a radius, where the radius is larger than the maximum height.

[0030] In one embodiment, the at least one rotating element is ferromagnetic and, in particular, soft magnetic.

[0031] 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; a drive for operating 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.

[0032] The invention will be described below using exemplary embodiments. Fig. Figure 1 schematically shows an exemplary electric drive according to the invention; Fig. 2 a) and Fig. 2 b) show an exemplary embodiment of a rotational locking device according to the invention of a Fig. 1 electric drive shown; Fig. Figure 3 shows an exemplary embodiment of a rotating element according to the invention; Fig. Figure 4 shows geometric boundary conditions regarding the rotational inhibiting device; Fig. Figure 5 sketches an actuator with an electric drive according to the invention.

[0033] Fig. Figure 1 schematically sketches 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 mechanically coupled rotational braking device 20, 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 exhibits 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.

[0034] By utilizing magnetic effects, an electric drive can be provided for an actuator that exhibits high efficiency in operation with low mechanical losses and low mechanical wear.

[0035] Fig. 2 a) and Fig. Figure 2 b) shows 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 permanent magnet 23, which has a rotationally symmetrical outer surface 23.1, for example, as shown here, and is in particular rotationally symmetrical. Furthermore, the rotational locking device exemplarily comprises three rotating elements 24, which are carried along by the rotor 21 so that they rotate around the outer surface of the permanent magnet when the electric motor is moving. According to the invention, the at least one rotating element 24 is attracted by the permanent magnet and comprises, for example, a ferromagnetic material, and in particular a soft magnetic material.

[0036] At least one track-forming element 25, such as three track-forming elements shown here, is designed to influence the movement of the rotating element 24 around the outer surface of the permanent magnet section by section and to enforce a minimum radial distance to the outer surface. In the case of a stationary / static electric motor ( Fig. 2a) The rotating elements adhere to the permanent magnet and are prevented by the track-forming elements from moving tangentially to the outer surface, since releasing the rotating elements from the outer surface must counteract the attractive force between the rotating element and the permanent magnet. In this way, a detent torque is generated by the exemplary embodiment according to the invention.

[0037] When the electric motor is switched on, the torque generated by the motor becomes sufficiently large above a certain motor current to disengage the rotating elements from the permanent magnet. Upon reaching a critical speed, the centrifugal force acting on the rotating elements becomes greater than the attractive force between the rotating element and the permanent magnet, 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 standpoint, the braking torque in this state can be considered zero.

[0038] As in Fig. 2 a) and Fig. 2 b) shown, a driving device 26 can be configured to drive the at least rotating element 24, wherein the driving 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 driving device 26 is formed by the rotor 21 or is coupled to the rotor.

[0039] The body of the guiding device forming the guides 26.1 can be formed in one piece or comprise several joined parts. The radially extending guide 26.1 can, for example, be a 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 a ring, such as a metal or plastic ring, which engages or clamps a body of the guiding device. The closure can also be formed by potting or bonding.

[0040] The circulation elements can, for example, be spherical ( Fig. 2 a) and Fig. 2 b)) or cylindrical, with one cylinder axis parallel ( Fig. 2 a) and Fig. 2 b)) or radial ( Fig. 3) runs to a stator axis. In the case of the in Fig. In the embodiment shown in section 3, the circumferential element is designed to slide along the track form element and the lateral surface upon contact; otherwise, a rolling movement is also possible.

[0041] The at least one track-forming element 25 can be formed by the stator 22 as shown here, wherein the permanent magnet 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 rotational locking device.

[0042] The at least one track-forming element 25 can be symmetrical with respect to a longitudinal section plane through the stator or permanent magnet, 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.

[0043] Fig. 4 outlines geometric boundary conditions for the designs of the Fig. 2 a), Fig. 2 b) and Fig. 3.

[0044] If there is a first point of contact B1 between the rotating element 24 and the guiding device 26 and a second point of contact B2 between the rotating element and the path forming element, a first tangential plane T1 runs through the first point of contact and parallel to the stator axis, and a second tangential plane T2 runs through the second point of contact and parallel to the stator axis, wherein the first tangential plane and the second tangential plane form a line of intersection SG.

[0045] The contact points B1 and B2 span a contact point plane BE parallel to the stator axis 22.1.

[0046] The stator axis 22.1 and the line of intersection SG are located on the same side of the plane of contact BE.

[0047] In this way, it is ensured that the recirculating element is not clamped between the driving device and the track forming element 25, since with respect to a direction of movement of the recirculating element the contact point B1 is then arranged behind a geometric center of gravity of the recirculating element, and can thus push the recirculating element in front of it.

[0048] 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.

[0049] In one embodiment, a first attractive force exists when the rotating element 24 and the permanent magnet 23 are in contact. At a maximum distance between two nearest points of the rotating element and the permanent magnet, a second attractive force is present, 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 speed can be adjusted by changing the ratio of the first attractive force to the second attractive force.

[0050] For example, the rotating element 24 can have a radius greater than its maximum height. This ensures that the rotating element is guided securely and robustly by the driving device and prevents it from becoming jammed.

[0051] The cogging torque provided by the device is significantly influenced by the product of the attractive force between the rotating element and the permanent magnet 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 R1 passes through the stator axis 22.1 and the first contact point B1.

[0052] At a small angle of inclination, little work needs to be done per angle of rotation, which is associated with a low cogging torque, and conversely, at a large angle of inclination, a large amount of work needs to be done per angle of rotation. Reference symbol list 1 Electric drive 2 Drive 3 gearboxes 4 electronic operating circuit 5 Housing arrangement 5.1 Housing 10 Electric motor 20 Rotational locking device 21 Rotor 22 Stator 22.1 Stator shaft 23 Permanent magnet 23.1 Surface area 24 Circulating element 25 Track element 25.1 Maximum height 25.2 far-facing surface 26 Carrying device 26.1 Leadership 100 actuators B1 first point of contact B2 second point of contact BE Touchpoint level R1 first radials R2 second radial SG straight section T1 first tangent plane T2 second tangent plane QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] WO 2013004360A2

[0002]

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 by , that the electric drive has a magnetic rotation-locking device (20) which is configured to lock the electric motor in its rotation in a static or quasi-static state with a cogging torque, wherein the rotational locking device (20) in a dynamic state above a 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. [2] Electric drive according to claim 1, wherein the rotational locking device (20) comprises: a rotor (21) dynamically and in particular statically coupled to the electric motor (10), and a stator (22); a permanent magnet (23) with a rotationally symmetric surface (23.1), in particular a rotationally symmetric permanent magnet, wherein the permanent magnet is arranged coaxially to the stator (22); at least one rotating element (24) which is carried along with the rotor (21) and which rotates around the outer surface (23.1) of the permanent magnet (23) in a cross-sectional plane through the permanent magnet, wherein the at least one rotating element (24) is magnetically attracted by the permanent magnet (23); at least one path-forming element (25) which is arranged on the lateral surface and forces the orbital element on an orbit to a distance to the lateral surface (23.1) section by section and has a maximum height (25.1) with respect to the lateral surface (23.1). [3] Electric drive according to claim 2, wherein a driving device (26) is arranged to drive the at least rotating element (24), wherein the driving 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 carrying device (26) is formed by the rotor (21) or is coupled to the rotor. [4] Electric drive according to one of claims 2 or 3, wherein the at least one path forming element (25) is formed by the stator (22), in particular wherein the permanent magnet (23) is fixed radially and / or axially and / or tangentially by the at least one track forming element (25). [5] Electric drive according to one of claims 2 to 4, wherein the rotating element (24) is spherical. [6] Electric drive according to one of claims 3 or 4, 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). [7] Electric drive according to one of claims 2 to 6, wherein the at least one path forming element (25) is symmetrical with respect to a longitudinal section plane through the permanent magnet (23). [8] Electric drive according to any one of claims 3 to 7, wherein, in the presence of a first contact point (B1) 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 (T1) runs through the first contact point and parallel to the stator axis, and a second tangential plane (T2) passes through the second point of contact and parallel to the stator axis, where the first tangent plane and the second tangent plane form a line of intersection SG, wherein the contact points B1 and B2 span a contact point plane BE parallel to the stator axis 22.1, where the stator axis 22.1 and the line of intersection SG are located on the same side of the plane of contact BE. [9] Electric drive according to claim 8, where there is a small angle of intersection between the first tangent plane and the second tangent plane 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. [10] Electric drive according to any one of claims 5 to 9, where a first attractive force exists when the rotating element (24) and the permanent magnet (23) are in contact, where a second attractive force exists when the distance between two nearest points of the rotating element and the permanent magnet is 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. [11] Electric drive according to any one of claims 2 to 10, wherein the rotating element (24) has a radius, the radius being greater than the maximum height. [12] Electric drive according to any one of the preceding claims 2 to 11, wherein the at least one rotating element (24) is ferromagnetic and in particular soft magnetic. [13] Actuator (100) for automation technology for actuating a fitting such as a valve, comprising: an electric drive (1) according to any of the preceding claims for generating a force or torque; a drive (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) comprising at least one housing (5.1) in which the drive, the gearbox, the output and the electronic operating circuit are arranged.

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