ACTUATOR WITH AN ELECTRIC MOTOR AND AN ELECTROMAGNET MOVABLE TO ITS ROTOR FOR APPLYING A CONTACT-BASED HOLDING TORQUE VIA A REMANENCE MAGNET FIELD

Description

[0001] The invention relates to an actuator for a damper or valve for adjusting a gaseous or liquid volume flow, particularly for HVAC applications for heating, ventilation, or cooling. The actuator comprises a housing containing an electric motor, a downstream gearbox (in particular a reduction gearbox), and an output element with an actuating connection for the damper or valve. The electric motor also includes a stator and a rotor rotating around an axis of rotation of the electric motor. The rotor is, in particular, magnetic. "Magnetic" here means that, for testing purposes, a permanent magnet would adhere to the rotor of the electromagnet.

[0002] From EP 1 258 969 A1, a drive device for actuating an actuator is known, comprising an electric motor, a return spring, and a centrifugal brake. The actuator can be actuated in a first direction of movement by the electric motor, which is activated by a control or regulating device, and in a second direction of movement by the return spring. A brake element of the centrifugal brake is arranged directly on the rotor of the electric motor. The centrifugal brake can be designed such that a braking effect is only generated when the actuator is driven by the return spring. The centrifugal brake limits the achievable rotational speeds to such an extent that no disturbing vibrations or noise occur.

[0003] US Patent 3,423,661 A discloses an electrically driven actuator for a valve that incorporates a torque-responsive and inertial energy-absorbing overload control. This control detects an overload condition of the valve and immediately shuts off the electric drive motor and applies a brake. The energy absorption of the device during torque overload is achieved by a gearbox connecting the electric drive motor and the driven shaft of the device. This gearbox includes a torque overload response element that, in the event of a torque overload, is movable against a spring preload to actuate a switch, thereby de-energizing the motor and applying the brake.

[0004] From EP 1 655 259 A1, a lifting device is known which comprises a stationary frame element, a main shaft, a stationary element arranged on the stationary frame element, a rotatable frame element which is supported on the main shaft and extends in a radial direction relative to the stationary frame element, a rotating element which is arranged on the rotatable frame element relative to the stationary element, a brake unit with a brake section which extends through an opening in the stationary frame element, and a pulley which is arranged on the rotatable frame element for rotation with it.

[0005] From EP 1 642 858 A2, an elevator tractor is known with an inner stator fixed in a support structure, with an outer rotor fitted over it, and with a rotating traction sheave connected to and attached to the outer rotor. The elevator tractor further comprises a brake gearbox coordinated with the brake sheave and an encoder capable of measuring the speed and relative position of the magnetic fields of the stator and rotor.

[0006] From DE 15 38 927 Al, an electric motor with a braking device is known in which the rotor of the electric motor is designed as an external rotor and simultaneously serves as a brake drum. The external rotor is surrounded in the area of ​​the engaging brake lining by an aluminum layer or by a ring of material with good frictional properties.

[0007] From US Patent 2020 / 0224742, a rotary coupling device is known with an armature configured to be coupled to a shaft in order to rotate with the shaft about an axis, but to be axially movable relative to the shaft. An electromagnet assembly is arranged on one side of the armature and fixed against rotation. On the opposite side of the armature, a collar is arranged which is designed to rotate with the shaft, but is fixed against axial movement relative to the shaft and also includes a permanent magnet. When a current of a first polarity is applied to the electromagnet assembly, the armature moves in an axial direction into engagement with an element of the coupling device to transmit a torque between the element and the armature.The permanent magnet pushes the armature in the opposite axial direction to release the armature from the element when no current is supplied to the electromagnet assembly.

[0008] From US patent 10,454,341 B1, a system is known comprising a rotatable disk with a plurality of ferromagnetic elements arranged in a radial configuration on a surface of the disk. The system includes at least one electro-permanent magnet (EPM) located adjacent to the disk, such that a gap separates the disk from the respective EPM. Applying an electrical pulse to the EPM changes its magnetic state, thereby generating an external magnetic field that passes through the gap between the disk and the EPM and interacts with one of the plurality of ferromagnetic elements, thus altering the rotational speed of the disk as it rotates.

[0009] From DE 198 32 694 A1, a braking device of the type of pole friction brake for braking an object moving along a linear path is known. It comprises a movable unit with an inner pole, an outer pole, and a coil, and furthermore provides an armature fixed perpendicular to the linear path, which can be selectively brought into frictional contact with an outer pole surface and with an inner pole surface. The movable object is coupled to the movable unit via a spring device.

[0010] From DE 1 290 244 B, an electromagnetic brake for electric motors with an external stator is known, in which a brake shoe firmly connected to a movable armature of an electromagnet presses against a brake ring attached to the motor shaft by spring force when the motor is de-energized and is lifted again by magnetic force against the spring force when the motor is switched on.

[0011] From DE 10 2018 210 167 A1, a drive device for driving movable components of a motor vehicle is known, comprising a flat electric motor with a stator and a disc rotor mounted to rotate about a rotational axis. The drive device has a locking device designed to lock the disc rotor. The locking device comprises a locking element movably mounted between a holding position and a release position, an actuating actuator device with a movably mounted actuator element for moving the locking element from the holding position to the release position, and a return device for returning the locking element from the release position to the holding position. In the holding position, the locking element is mechanically engaged with a locking section of the disc rotor.

[0012] In such actuators, the flap or valve is moved around an axis by the actuator's actuating element, or even at least partially formed directly by it. The actuator is often designed to move the actuating element from a first position to a second position. Both positions can typically be end stops. A first position can also be called the start or rest position, to which the actuator returns the actuating element when the drive element (i.e., the electric motor) is de-energized, particularly by means of a pre-tensioned return spring. Such actuators are also referred to as fail-safe actuators. The second position can be called the actuating position or end position.The actuator can be rotatably arranged about its actuator axis within a predetermined rotational angle range between a rest position (start position) and an actuating position (end position). The maximum rotational angle range between these two positions is preferably 90° ± 10°.

[0013] In the case of non-fail-safe actuators, electric motors with increased self-holding torque are often required to prevent the actuator from "continuing to run" beyond the applied torque of the load, i.e., the flap or valve. The electric motors designed for this purpose typically feature a rotor with a detent gear.

[0014] The actuators under consideration can alternatively be linear actuators, which effect a linear positioning movement of the actuating element along an actuating axis at the actuator connection, for example to control a valve to open, partially open, or close. Such actuators can be designed to be either fail-safe or non-fail-safe.

[0015] To keep a fail-safe actuator in the actuated position, the simplest method is to maintain the electric motor in this position using a continuously applied holding current (minimum current). Only when the power supply, and thus the holding current, fails, does the spring compress, and the actuator moves the actuator element to its safe rest position.

[0016] In another known solution, a solenoid engages in the reduction gear of the actuator to prevent the actuator from automatically returning to its safe rest position. If the power supply is interrupted or fails, the solenoid disengages from the gear. The gear then rotates freely, allowing the actuator to return the actuator to its safe rest position.

[0017] Both of the aforementioned solutions have a relatively high power consumption when in operation. For example, the duty cycle of safety-relevant fire dampers is practically 100% (ED 100%).

[0018] It is therefore an object of the present invention to at least partially eliminate the disadvantages described above in actuators.

[0019] Another objective of the invention is to provide a more flexibly deployable actuator.

[0020] Ultimately, the task is to specify a fail-safe actuator that requires less electrical power (current consumption).

[0021] The object of the invention is achieved by the features of the main claim. Advantages and embodiments of the invention, which can be used individually or in combination with one another, are the subject of the dependent claims.

[0022] According to the invention, the rotor is located externally, coaxially with the axis of rotation of the electric motor. The actuator has an electromagnet arranged adjacent to an outer surface of the rotor. The electric motor is therefore not part of the rotor itself. The electromagnet comprises a coil assembly with a magnetic core. The actuator has an electrical circuit for controlling the electromagnet. A first, preferably short-duration, current pulse can be impressed into the coil assembly by means of the circuit, so that a residual magnetic field subsequently remains in the core. This allows the actuator to apply a contact-based holding torque to the outer surface of the electric motor rotor by building up a mechanical preload in a holding position.By means of the circuit arrangement, a second, preferably short-term, current pulse can be impressed into the coil arrangement in order to subsequently essentially extinguish the remanent magnetic field still present in the coil core in order to release the contact-related holding torque by forming an air gap between the electromagnet and the outside of the rotor of the electric motor.

[0023] The electromagnet is arranged in such a way that it is movable adjacent to the outside of the rotor, so that, under mechanical preload, the electromagnet rests against the outside of the rotor in the holding position to apply the holding torque.

[0024] The first short-term current pulse can be impressed into the coil arrangement in such a way that the electromagnet closes the air gap towards the holding position by means of magnetic force and remains magnetically attached to the outside of the rotor by means of the remanent magnetic field remaining in the coil core, applying the holding torque.

[0025] The second short-term current pulse is imprinted into the coil arrangement in such a way that the remanent magnetic field still present in the coil core is essentially extinguished, whereby the electromagnet moves automatically away from the outside of the rotor towards the freewheeling position, forming the air gap, and remains there.

[0026] The coil arrangement can comprise a single coil or winding wound around the magnetic core, which can then be energized by a positive and negative excitation current. Alternatively, the coil arrangement can also comprise two coils or windings wound around the magnetic core, which can be energized separately by an excitation current.

[0027] The magnetic coil core can be a soft magnetic or hard magnetic coil core.

[0028] The term "soft magnetic" refers to materials suitable for coil cores, such as iron, cobalt, nickel alloys, or ferrites, which readily magnetize in a magnetic field. This magnetic polarization can be generated, for example, by an electric current in a current-carrying coil around the core or by the presence of a permanent magnet. In all soft magnetic materials, this polarization results in a magnetic flux density many times higher than that produced by an externally applied magnetic field in air. Soft magnetic materials for coil cores typically have a coercive field strength of less than 1000 A / m.

[0029] The term "hard magnetic" means that the hard magnetic materials suitable for the coil core possess very high coercivity (HC) and therefore offer high resistance to external magnetic fields. Magnetization reversal (or demagnetization) is only achieved through the application of very strong external magnetic fields. For operation in an actuator according to the invention, the electromagnets under consideration are advantageously extremely resistant and robust. Hard magnetic materials include, for example, alloys of AlNiCo (for aluminum, nickel, and cobalt), CuNiFe (for copper, nickel, and iron), FeCoCr (for iron, cobalt, and chromium), MnAlC (for manganese, aluminum, and carbon), or PtCo (for platinum and cobalt). The hard magnetic materials can also be hard ferrites or martensitic steels.The hard magnetic materials for the coil core have a coercive field strength of at least 1000 A / m, in particular at least 5000 A / m.

[0030] The term "essentially eliminated" or "compensated" means that the remaining magnetic field generated at the electromagnet (remanent magnetic field) has a (maximum) flux density value that is less than 20%, in particular less than 10%, preferably less than 5%, compared to the (maximum) flux density value of the remanent magnetic field. Magnetic remanence or residual magnetism, in this context, refers to the magnetization that a previously magnetized particle, saturated by an external magnetic field (e.g., by means of a current-carrying coil or a permanent magnet), retains after the external field is removed.

[0031] A "short-term" first or second current pulse refers to a pulse length in the range of 5 ms to 1000 ms, particularly in the range of 5 ms to 200 ms, and preferably in the range of 10 ms to 50 ms. Due to the relatively long time intervals between a change from the holding position to the freewheeling position and vice versa, the pulse length of the first or second current pulse can also be in the range of seconds or minutes. However, such a long pulse length would lead to an unnecessarily high thermal load on the coil assembly in an electromagnet.

[0032] The mechanical preload can be achieved, for example, by means of a spring element, a bending spring, or a rubber buffer. The restoring force back to the freewheel position caused by the mechanical preload is considerably smaller than the holding force caused by the remanent magnetic field on the outside of the rotor.

[0033] By means of the "switchable" remanent magnetic field remaining at the electromagnet, it is advantageously possible that electrical energy is only required for the switching process from the freewheeling position to the holding position and vice versa. For the vast majority of the time between switching processes, only a negligible amount of electrical power is advantageously required.

[0034] For example, the fail-safe operation of a known actuator requires a continuous electrical power of 2 watts to hold the electric motor in the actuated position against the restoring torque of the return spring. This results in an annual electrical energy consumption of approximately 17 kWh. In contrast, the actuator according to the invention advantageously requires an annual electrical energy consumption of less than 1 kWh due to the only occasional test activations and the even less frequent actual activations in an emergency.

[0035] Another major advantage is that, due to the typically very high gear reduction in the range of 1:1000 to 1:10000 and the lever being located very far out on the rotor for applying the electromagnet, only a relatively small holding force of less than 1 N, in particular less than 0.1 N, is required to hold the actuating element of the actuator in position.

[0036] The term "movable" generally refers to movements of the electromagnet, preferably with only one degree of freedom, i.e., axial movement towards and away from the axial outer surface of the rotor, or radial movement towards and away from the radial outer surface of the rotor. The air gap, if present, can have values ​​in the range of 1 mm to 5 mm, preferably in the range of 1.5 mm to 3 mm.

[0037] In one embodiment, the electric motor is fixedly mounted on a base plate within the actuator housing. The electromagnet is movably mounted on the base plate within the housing and has a magnetically active end. The electromagnet is oriented on the base plate such that, in the free-running position, its active end faces a radial outer surface of the rotor, forming the air gap.

[0038] In an alternative embodiment to the previous embodiment, the electric motor is arranged on a base plate within the actuator housing. The electromagnet is movably mounted on a bracket of the housing and has a magnetically active end. The electromagnet is aligned on the bracket such that, in the free-running position, the active end of the electromagnet faces a radial outer surface on the axial outer side of the rotor, forming the air gap.

[0039] In both of the preceding embodiments, the respective electromagnet can preferably form two pole shoes at its magnetic effective end, which are adapted in their shape to guide the magnetic field into the opposite rotor outer side.

[0040] In particular, according to one embodiment, the electromagnet is arranged on the housing mounting or on the base plate in the housing by means of a flexible retaining element. In the simplest case, the flexible retaining element is a stamped part made of spring steel.

[0041] According to another embodiment, the coil core is made of a grain-oriented electrical steel.

[0042] According to another embodiment, the coil core is a soft magnetic core. A permanent magnet is arranged in the coil core, which generates a permanent magnetic field within the core. When the second short-duration current pulse is applied to the coil assembly and the air gap at one end of the electromagnet is restored, this field is essentially no longer effective and is thus extinguished.

[0043] The magnetic circuit in the electromagnet is maintained in the holding position by the permanent magnetic field and, after the magnetic field generated by the coil assembly dissipates, by the permanent magnetic field generated by the coil assembly. After the second current pulse is applied to the coil assembly, the magnetic "control" flux of the coil assembly is superimposed on the permanent magnetic flux of the permanent magnet integrated into the coil core. At this moment, the magnetically active end of the electromagnet is essentially field-free. The electromagnet moves away from the "magnetic short circuit" through the outer surface of the rotor, or rather, the first end of the lever element moves away from the magnetically active end of the electromagnet. As the air gap that now forms increases, so does the magnetic resistance at the active end of the electromagnet, until the permanent magnetic field inside the coil core creates a magnetic flux with lower magnetic resistance.After the magnetic field generated by the coil arrangement is dissipated, the magnetic flux of the permanent magnet field inside the coil body remains closed. The magnetically active part of the electromagnet remains essentially magnetically inactive.

[0044] According to a further embodiment, the part adhering to the outer surface of the rotor in the holding position comprises a brake lining, wherein the brake lining has a coefficient of friction for the brake lining-rotor outer surface of at least 0.5, in particular at least 0.8. This significantly increases the static friction and thus the static frictional torque on the outer surface of the rotor. The brake lining can be a thin layer of rubber, plastic, or the like, with a maximum layer thickness in the range of 0.1 mm to 0.5 mm.

[0045] In an advantageous embodiment, the rotor has on its outer surface a toothed arrangement with alternating teeth and gaps, rotating tangentially with respect to an axis of rotation of the electric motor. The gaps have a tangential dimension. A part adhering to the outer surface of the rotor in the holding position has such a maximum tangential dimension that it engages with one of the gaps of the toothed arrangement in the holding position.

[0046] The radial depth of a tooth gap is preferably in the range of 0.3 mm to 1.5 mm. This further increases the holding torque acting on the rotor through positive locking. Because the electric motor is initially decelerated via the motor control and the electromagnet is then applied to the stationary rotor, there is effectively no friction braking. Furthermore, the braking effect is much higher for the same magnetic force due to the toothed design.

[0047] According to one embodiment, the actuator has a control unit for receiving a control signal and for correspondingly controlling the electric motor to move the actuator from a predetermined first actuation position to a predetermined second actuation position. The control unit is configured to control the electrical circuitry for the electromagnet such that the electromagnet switches from the holding position to the freewheeling position before or at the same time as the electric motor is activated to move the actuator from the first actuation position to the second actuation position. Furthermore, the control unit is configured to control the electrical circuitry such that the electromagnet switches from the freewheeling position to the holding position at or after the second actuation position of the actuator terminal has been reached. The control unit can, for example, be a higher-level microcontroller of the actuator.

[0048] This embodiment is particularly advantageous for non-fail-safe actuators. Due to the time-coordinated transition from the holding position to the release position and back again, no detent wheel is required for moving the actuator.

[0049] According to an alternative embodiment to the previous embodiment, the actuator has a control unit for controlling the electric motor when the actuator's power supply is switched on or when a switch-on signal is received, in order to move the actuator from a safe rest position to an actuated position. The actuator has a return spring for providing a return torque acting on the actuator to automatically move the actuator to its safe rest position, particularly when the power supply to the actuator fails. The return torque, via the reduction gear, causes a rotor return torque on the electric motor. The holding torque applied to the rotor in the holding position by means of the electromagnet is greater than the rotor return torque acting on the rotor. In particular, the holding torque is at least 1.5 to 3 times greater than the rotor return torque.This ensures that the actuator reliably remains in the actuated position.

[0050] The control unit is designed to control the electrical circuit arrangement upon receiving a switch-off signal in such a way that the electromagnet changes from the holding position to the freewheeling position, so that the actuator automatically returns to the safe rest position.

[0051] Alternatively, the electrical circuit arrangement can be configured so that, when the power supply fails, the electromagnet switches from the holding position to the freewheeling position, so that the actuator automatically returns to the safe rest position.

[0052] In a further embodiment, alternative to the two preceding embodiments, the actuator has a control unit for controlling the electric motor when the actuator's power supply is switched on or when a switch-on signal is received, in order to move the actuator from a safe rest position to an actuated position. The actuator includes a return spring for providing a return torque acting on the actuator to automatically move the actuator to its safe rest position, particularly when the power supply to the actuator fails. The flap or valve connected to the actuator port, together with the return spring, exert a combined torque on the actuator. This combined torque further induces a combined rotor torque via the reduction gear.The holding torque applied to the rotor of the electric motor in the holding position by means of the electromagnet is greater than the total rotor torque acting on the rotor, in particular at least 1.5 to 3 times greater. This ensures that the actuator remains reliably in the actuated position even when considering connected loads such as flaps or valves.

[0053] The control unit is configured to activate the electrical circuitry upon receiving a power-off signal, such that the electromagnet switches from the holding position to the freewheeling position, allowing the actuator to automatically return to its safe rest position. Alternatively, the electrical circuitry can be configured so that the electromagnet switches from the holding position to the freewheeling position when the power supply is interrupted, allowing the actuator to automatically return to its safe rest position.

[0054] According to another embodiment, the electrical coil arrangement of the electrical circuit arrangement comprises an electrical coil, wherein the electrical coil is connected in series with a capacitor. The series circuit is connected at one end to a common reference potential. A second end can be switched (optionally) to a supply voltage or to the common reference potential via a switching element of the electrical circuit arrangement. The switching element can, for example, be a changeover switch. The inductance of the electrical coil and the capacitance of the capacitor are dimensioned such that when the second end of the series circuit is connected to the supply voltage, the first short-term current pulse can be impressed into the electrical coil, and that when the second end of the series circuit is connected to the common reference potential, the second short-term current pulse can be impressed into the electrical coil with the opposite current direction.

[0055] According to one embodiment, the switching element of the electrical circuit arrangement can be controlled by the control unit of the actuator, so that the electromagnet changes from the holding position to the freewheeling position and vice versa.

[0056] Further advantages, features, and details of the invention will become apparent from the following description, in which exemplary embodiments of the invention are described in detail with reference to the drawings. The features mentioned in the claims and in the description can each be essential to the invention individually or in any combination. Elements with the same function and mode of operation are shown in the Figuren 1 bis 5 Each is labelled with the same reference symbols. They show schematically: FIG 1 a sectional view through an exemplary actuator with a first and second electromagnet for applying a contact-based holding torque via a remanent magnetic field according to the invention, each on an axial and alternatively radial outside of the rotor and each in a freewheeling and holding position, FIG 2 the example according to FIG 1 in a top view and with a toothing on the radial outside of the rotor according to one embodiment, FIG. 3 a top view of the electromagnet according to the one shown in FIG 1 The direction of view shown in Figure III, Figure 4 shows the principle of an electrical circuit arrangement for selectively controlling the electromagnet for a possible application of the holding torque by means of a first and second current pulse that can be impressed into the coil arrangement of the electromagnet, and Figure 5 shows an exemplary technical realization of the electrical circuit arrangement according to Figure 5. FIG 4 and with a refresh function according to one embodiment.

[0057] FIG 1 shows a sectional view through an exemplary actuator with a first and second electromagnet E1, E2 for applying a contact-based holding torque via a remanent magnetic field according to the invention, each on an axial and alternatively radial outer side RA, AA of the rotor RO and each in a freewheeling and holding position.

[0058] The actuator shown is designed for a flap or valve to adjust the flow rate of a gaseous or liquid. The actuator further comprises an electric motor MO mounted on a housing-mounted base plate GP. The electric motor is housed in a housing of the actuator (not shown). The latter includes a stator, designed as a multiple armature with a plurality of armature coils, which is fixedly mounted on the base plate GP or on a circuit carrier LP of the actuator. The armature coils of the stator ST are supplied with current via an electronic motor controller of the actuator, with phase control. The circuit carrier LP is itself fixedly mounted on the base plate GP. A rotor RO, designed as a rotor bell GL or rotor cup, is arranged coaxially or radially outwards to the stator ST.The rotor RO typically comprises a plurality of permanent magnets arranged tangentially to the axis of rotation A along the radial inner surface of the rotor bell GL. The rotor bell GL itself is made of a magnetic material, such as iron, nickel, or ferrite. The rotor RO includes an unspecified motor shaft, which, for example, passes through the base plate GP located in the actuator housing and terminates in a motor gear MZ as part of a reduction gear G of the actuator. The motor gear MZ meshes with a gear ZR of the reduction gear G.

[0059] The reduction gear G typically includes several gears connected in series, particularly those mounted in the base plate GP, to achieve the desired reduction of an actuating element of the actuator. The actuating element can be, for example, a gear segment. The actuating element itself has an actuating port for connecting the actuator to the aforementioned flap or valve as a load. Depending on the design of the output, a predefinable rotary movement about an actuating axis of the actuator or a predefinable linear actuating movement along the actuating axis is possible at the actuating port.

[0060] In this example, the reduction gear G is connected to a return spring RF, which is pre-tensioned in an actuated position of the actuator. In the event of a power failure or interruption of the actuator's power supply, the return spring moves the actuating element back to a safe rest position via the reduction gear G. Such an actuator is called a fail-safe actuator or a spring-return actuator. In this example, the return spring RF is a coil spring or a drive spring.

[0061] According to the invention, the actuator has an electromagnet E1, E2 movably arranged on an outer surface RA, AA of the rotor RO such that, in a free-running position, it forms an air gap LS to the outer surface RA, AA of the rotor RO, and in a holding position, it is in contact with the outer surface RA, AA of the rotor RO. In this context, RAD is the radius of the rotor RO or the rotor bell GL, and AB is the (mean) radial distance of the FIG 1 The upper second electromagnet E2 is shown, and h G is the (axial) height of the rotor bell GL.

[0062] In the upper left part of the FIG 1 The second electromagnet E2 is spaced apart from the axial rotor outer surface RA by the air gap LS. The second electromagnet E2 is therefore in the freewheeling position and consequently does not exert any contact-related holding torque on the axial rotor outer surface RA. The second electromagnet E2 is, for example, attached to a housing-fixed mounting HA via a flexible component BS, such as a flexible rod, and is mechanically stress-free.

[0063] In anticipation of the FIG 3 The electromagnets E1, E2 form one, preferably two, pole shoes P at their effective end W opposite the rotor outer surface RA, AA, at which a magnetic field is generated when the electromagnet E1, E2 is energized. In the example of the present FIG 1 The electromagnets E1 and E2 each have a brake shoe B at their respective effective end W to increase the holding torque. The electromagnets E1 and E2 each comprise a coil assembly L and a soft magnetic coil core K. For power supply, the electromagnets E1 and E2 are connected via a supply line Z to an electrical connection AN of a circuit arrangement designed for this purpose to control the electromagnets E1 and E2 according to the invention. A permanent magnet PM can also be arranged in the coil core K, as shown by the dashed line, which generates a permanent magnetic field in the coil core K. In this case, the coil core K is a soft magnetic coil core. The permanent magnetic field is no longer effective and thus essentially compensated when the second short-duration current pulse is applied to the coil assembly L and after the air gap LS at the pole shoe P has been restored.

[0064] In the upper right part of the FIG 1 The second electromagnet E2 is now directly attached to the axial outer surface AA of the rotor, applying a magnetic force F acting in the axial direction, and thus in the normal direction to the axial outer surface AA of the rotor. µH is a dimensionless coefficient of friction that characterizes the material pairing of the material and surface properties of the axial outer surface AA of the rotor RO and the directly adjacent brake shoe B. Thus, according to the physical relationship, the force F is applied to the axial outer surface AA of the rotor RO. Reibkraft = Normalkraft ⋅ Reibungskoeffizient the frictional force F · µ H on or across the mean radial distance AB to the second electromagnet E2 the holding torque M FH (see FIG 2 ) as the product of frictional force and mean radial distance AB on the axial rotor outer surface AA.

[0065] In the lower part of the FIG 1 Analogous to the two upper electromagnets E2, a first electromagnet E1 is shown, which can now be moved radially from the freewheeling position to the holding position towards a radial outer surface RA of the rotor RO by means of a magnetic force F. In the lower left part of the FIG 1 The first electromagnet E1 is shown in the freewheeling position. In the lower right part of the FIG 2 The first electromagnet E1 is shown in the holding position. h1 and h2 are shown as examples of two installation heights for the first electromagnet E1, where the holding torque or static friction torque MFH is typically greater the greater the installation height h1, h2 of the first electromagnet E1.

[0066] In the present example, the electrical connection for connecting the supply line Z is located on the circuit carrier LP, on which the stator ST of the electric motor MO is also arranged. Generally, for all embodiments of the actuator according to the invention, it is advantageous if the electrical circuit arrangement for the electrical control of the electromagnets E1, E2 is also located on this circuit carrier LP. Additional electrical and electronic components can also be arranged on the circuit carrier LP, such as the motor control and / or a control unit (microcontroller) of the actuator and / or a power supply unit for the actuator or for the motor control.

[0067] According to the invention, for a change from the freewheeling position to the holding position, a first short-term current pulse can be impressed into the coil arrangement L by means of the circuit arrangement, so that the electromagnet E1, E2 closes the air gap LS towards the holding position by means of magnetic force F and adheres to the outside AA of the rotor RO by means of the remanent magnetic field remaining in the coil core K by applying a holding torque M FH.

[0068] Furthermore, according to the invention, a second short-term current pulse can be impressed into the coil arrangement L for a change from the holding position to the freewheeling position by means of the circuit arrangement, so that the remanent magnetic field present in the coil core K of the electromagnet E1, E2 is essentially compensated and the electromagnet E1, E2 moves away from the outside RA, AA of the rotor RO towards the freewheeling position and remains there, forming the air gap LS.

[0069] Generally, only a single electromagnet E1, E2 per electric motor MO can be provided to apply a static friction torque M FH to the outer surface RA, AA of the rotor RO. Alternatively, two radially opposed electromagnets E1, E2 per electric motor MO can be provided to each apply a preferably equal static friction torque M FH to the outer surface RA, AA of the rotor RO. In the latter case, advantageously no bending moment acts on the motor shaft of the electromagnet.

[0070] FIG 2 The example shows according to FIG 1 In a top view, it is clearly visible how the holding torque MFH applied by the first electromagnet E1 to the radial outer surface RA of the rotor in the right part of the figure is greater than the motor restoring torque MRF acting on the electric motor MO or the rotor RO via the return spring RF and the reduction gear G. This keeps the electric motor MO in the holding position. It is also evident how the first electromagnet E1, which is movably mounted on the circuit carrier LP by means of a flexible component BS, is moved towards the radial outer surface RA of the rotor by magnetic force F and remains there. The flexible component BS could, for example, be an L-shaped stamped part made of spring steel.

[0071] In the present case FIG 2 A toothing VZ on the radial outer surface RA of the rotor RO is also shown according to one embodiment of the invention. The toothing VZ, which rotates tangentially with respect to the axis of rotation A of the electric motor MO, has alternating teeth ZA and tooth gaps ZL. The tooth gaps ZL have a tangential tooth gap dimension. A part P, such as the pole shoe P of the first electromagnet E1, which adheres to the outer surface RA of the rotor RO in the holding position, has a maximum tangential dimension T such that this part P engages with one of the tooth gaps ZL of the toothing VZ in the holding position. This further increases the holding torque M FH acting on the rotor RO by means of positive locking. The radial depth of a tooth gap ZL is preferably in the range of 0.3 mm to 1.5 mm.

[0072] FIG 3 shows a top view of an electromagnet E1, E2 according to the in FIG 1 View direction shown in Figure III. In the present example, the electromagnet E1, E2 has a magnetic pot-shaped coil core K in which a cylindrical pot (coil) L is inserted. Depending on the direction of the excitation current flowing through the coil L, two opposite magnetic poles N, S are formed at both pole shoes P. In this example, a radially outer magnetic north pole N is formed at the radially outer pole shoe P and a radially inner magnetic south pole S is formed at the inner pole shoe P.

[0073] FIG 4 Figure 1 illustrates the principle of an electrical circuit arrangement for selectively controlling the electromagnets E1 and E2 to apply the holding torque MFH by means of a first and second short-duration current pulse that can be impressed into the coil L of the electromagnets E1 and E2. The circuit arrangement comprises a series connection consisting of the coil L of the electromagnets E1 and E2, a capacitor C, and a changeover switch WS. One end of the series connection and one contact of the changeover switch WS for the freewheeling position are each connected to ground as a common reference potential. When the changeover switch WS is in the position marked "holding position," the capacitor C is charged via a supply voltage potential applied through the contact for the holding position and via the series-connected coil L until the capacitor C is saturated.A brief current pulse thus flows through coil L, the duration of which is determined by the time constant derived from the inductance of coil L and the capacitance of capacitor C. A current pulse, initially increasing and then decreasing, flows through coil L, generating a corresponding magnetic field. Generally, the pulse duration of the current pulse is in the range of 5 ms to 1000 ms, particularly in the range of 5 ms to 200 ms, and preferably in the range of 10 ms to 50 ms. When the changeover switch WS is switched from the holding position to the freewheeling position, capacitor C discharges through coil L with the current flowing in the opposite direction and generating a corresponding magnetic field with the opposite magnetic polarity.

[0074] FIG 5 shows an exemplary technical implementation of the electrical circuit arrangement according to FIG 4 and with a refresh function according to one embodiment. When a positive switching voltage UE is applied to set the holding position of the electromagnet E1, E2, the push-pull stage formed by the two transistors T2, T3 switches the positive supply voltage to the series circuit consisting of the coil L of the electromagnet E1, E2 and the capacitor C. The resistor R1, the transistor T1, and the two resistors R2, R3 function here as an inverter. As long as the switching voltage UE is applied to the circuit arrangement, the capacitor C is charged until it is saturated. The electromagnet E1, E2 is moved towards the rotor outer surface RA, AA by the magnetic force F of the magnetic field, which also forms in pulses. After charging, the circuit arrangement shown is advantageously in a steady-state power-saving mode.Due to the remanent magnetic field, the electromagnet E1, E2 remains attached to the outer surface of the rotor RA, AA and thus in the holding position. When the positive switching voltage UE drops towards 0V, the push-pull stage connects the coil L to the common reference potential (ground). The capacitor C is discharged in reverse, generating an opposite magnetic field in the coil L. This compensates for the remanent magnetic field, and the electromagnet E1, E2 moves away from the outer surface of the rotor RA, AA back into the freewheeling position.

[0075] In the right part of the FIG 5The diagram shows another transistor T4 and two further resistors R4 and R5, which are provided for a refresh function according to one embodiment of the invention. When a positive switching voltage UR is applied to refresh the electromagnet E1, E2, the capacitor C is discharged and the electromagnet E1, E2 is "refreshed" to maintain the remanent magnetic field. This refresh can occur, for example, once a day or several times a week to prevent an unacceptable weakening of the remanent magnetic field over time. The control of the additional transistor T4 can be achieved, for example, by the circuit arrangement itself or by a higher-level control unit of the actuator. Control can be effected by applying another short-duration voltage pulse UR, particularly in the range of 5 ms to 200 ms.The component shown above transistor T4 is an optional suppressor diode, which limits excessively high voltages from coil L if necessary. Reference symbol list

[0076] A Rotation axis, motor axis AA Axial outer surface AB Radial distance AN Electrical connection B Brake pad BS Bending rod, flexible component, beam C Capacitor, electrolytic capacitor D Lever rotation axis, pivot point E1, E2 Electromagnet, remanent magnet F Force, magnetic force, attracting force G Gearbox GL Rotor bell GP Base plate, housing part h1, h2 Component height of the electromagnets HA Mounting hG Height of the rotor, height of the rotor bell K Coil core LP Circuit carrier, printed circuit board L Coil assembly, coil L Air gap MFH Holding torque, static torque MO Motor, electric motor MRF Motor restoring torque MZ Motor gear, motor pinion N North pole P Pole shoe PM Permanent magnet R1-R5 Ohmic resistors RA Radial outer surface of the rotor RAD Radius of the rotor bell RB Radial outer surface of the axial outer surface RF Restoring spring RO Rotor, rotor bell, rotor cup S South pole ST Stator Tangential dimension T1-T4 transistors,electronic switching elements UE Switching voltage for holding operation of the electromagnet UR Switching voltage for refresh of the electromagnet VZ Gearing WW Contacting WS Changeover switch Z Supply line, connecting cable, conductor foil ZA Tooth ZL Tooth gap ZR Gear µ H Coefficient of friction S South pole ST Stator T Tangential dimension T1-T4 Transistors, electronic switching elements UE Switching voltage for holding operation of the electromagnet UR Switching voltage for refresh of the electromagnet VZ Gearing WW Contacting WS Changeover switch WW Magnetic material Z Supply line, connecting cable, conductor foil ZA Tooth ZF Tension spring, spring element ZL Tooth gap ZR Gear µ H Coefficient of friction,

Claims

1. Actuator for a flap or for a valve for adjusting a gaseous or fluid volume flow, wherein the actuator has a housing, an electric motor (MO) accommodated therein, a downstream reduction gear (G) and, as a take-off, a actuating element with an actuator connection for the flap or the valve, wherein the electric motor (MO) has a stator (ST) and a rotor (RO) circumferential to an axis of rotation (A) of the electric motor (MO), characterised in that, - the rotor (RO) is a rotor (RO) lying coaxially outside in relation to the axis of rotation (A) of the electric motor (MO), - the actuator has an electromagnet (E1, E2) arranged adjacent to an outer side (RA, AA) of the rotor (RO), wherein this (E1, E2) comprises a coil arrangement (L) with a magnetic coil core (K), - the actuator has an electrical circuit arrangement for activation of the electromagnet (E1, E2), - by means of the circuit arrangement a first brief current pulse is able to be injected into the coil arrangement (L), so that subsequently a remanent magnetic field remains in the coil core (K), in order, in a holding position of the actuator, while a mechanical pre-tensioning is set up, to apply a holding torque with contact (MFH) to the outer side (RA, AA) of the rotor (RO), and - by means of the circuit arrangement a second brief current pulse is able to be injected into the coil arrangement (L), in order subsequently essentially to extinguish the remanent magnetic field still present in the coil core (K) for releasing the holding torque (MFH) with contact, while an air gap (LS) between the electromagnet (E1, E2) and the outer side (RA, AA) of the rotor (RO) is formed, - the electromagnet (E1, E2) is arranged movably adjacent to the outer side (RA, AA) of the rotor (RO) in such a way that the electromagnet (E1, E2), while the mechanical pretensioning in the holding position for applying the holding torque (MFH) is formed, rests against the outer side of the rotor, - the first brief current pulse is able to be injected into the coil arrangement (L) in such a way that the electromagnet (E1, E2) closes the air gap (LS) by means of magnetic force (F) towards the holding position and, through the remanent magnetic field remaining in the coil core (K), while the holding torque (MFH) to the outer side (RA, AA) of the rotor (RO) is formed, sticks magnetically, and - the second brief current pulse is able to be injected into the coil arrangement (L) in such a way that that a remanent magnetic field still present in the coil core (K) is essentially extinguished, wherein the electromagnet (E1, E2) moves away automatically, while the air gap (LS) is formed, from the outer side of the rotor towards the free running position and remains there.

2. Actuator according to claim 1, wherein the electric motor (MO) is arranged on a base plate (GP) in the housing of the actuator, wherein the electromagnet (E1) is arranged movably on the base plate (GP) in the housing and has a magnetic working end (W), wherein the electromagnet (E1) is aligned in such a way on the base plate (GP) that the working end (W) of the electromagnet (E1), in the free running position, lies against a radial outer side (RA) of the rotor (RO) while the air gap (LS) is formed.

3. Actuator according to claim 2, wherein the electromagnet (E1) is arranged by means of an elastic holding element (BS) for setting up the mechanical pretensioning on the bracket (HA) of the housing or on the base plate (GP) in the housing.

4. Actuator according to one of the preceding claims, wherein the coil core (K) is a soft magnetic coil core (K), wherein a permanent magnet (PM), which creates a permanent magnetic field in the coil core (K), is arranged in the coil core (K), wherein the permanent magnetic field, on injection of the second brief current pulse into the coil arrangement (L) and after re-establishment of the air gap (LS) to a working end (W) of the electromagnet (E1, E2), is essentially no longer effective and is thus extinguished.

5. Actuator according to one of the preceding claims, wherein a part (E1, E2) adhering to the outer side (RA, AA) of the rotor (RO) in the holding position comprises a brake coating (B), wherein the brake coating (B) has a coefficient of friction (µH) for the pairing of brake coating and outer side of the rotor of at least 0.5, in particular of at least 0.8.

6. Actuator according to one of the preceding claims, wherein the rotor (RO), on its outer side (RA, AA), has toothing (VZ) running around it tangentially with regard to an axis of rotation (A) of the electric motor (MO) with alternating teeth (ZA) and tooth gaps (ZL), wherein the tooth gaps (ZL) have a tangential tooth gap dimension and wherein a part (E1, E2, B) adhering to the outer side (RA, AA) of the rotor (RO) in the holding position, has a maximum tangential dimension (T), so that this latches in the holding position with one of the tooth gaps (ZL) of the toothing (VZ).

7. Actuator according to one of claims 1 to 6, - wherein the actuator has a control unit for receiving a control signal and for corresponding activation of the electric motor (MO) for moving the actuating element from a predetermined first actuation position to a predetermined second actuation position, - wherein the control unit is configured to activate the electrical circuit arrangement for activating the electromagnet (E1, E2) in such a way that the electromagnet (E1, E2), before or with the activation of the electric motor (MO) for moving the actuating element from the first actuation position to the second actuation position, switches from the holding position into the free running position, and - wherein the control unit is configured to activate the electrical circuit arrangement in such a way that the electromagnet (E1, E2), as or after it reaches the second actuation position of the actuating element, switches from the free running position into the holding position.

8. Actuator according to one of claims 1 to 6, - wherein the actuator has a control unit for activation of the electric motor (MO) when the power supply of the actuator is switched on or when a switch-on signal to drive the actuating element from a safe idle position to an actuation position is received, - wherein the actuator has a return spring (RF) for providing a return torque acting on the actuating element for automatically moving the actuating element into the safe idle position, in particular when the power supply for the actuator is lost, wherein the return element brings about a rotor return torque (MFR) at the electric motor (MO) via the reduction gear (G), - wherein the holding torque (MFH) applied by means of the electromagnet (E1, E2) to the rotor (RO) in the holding position is greater that the rotor return torque (MFR) acting on the rotor (RO), in particular at least 1.5 times to 3 times as great, and - wherein the control unit is configured to activate the electrical circuit arrangement on receipt of a switch-off signal in such a way that the electromagnet (E1, E2) switches from the holding position into the free running position, so that the actuating element is moved back automatically into the safe idle position, or - wherein the electrical circuit arrangement is configured in such a way that, when the power supply is lost, the electromagnet (E1, E2) switches from the holding position into free running position, so that the actuating element is moved back automatically into the safe idle position.

9. Actuator according to one of claims 1 to 6, - wherein the actuator has a control unit for activation of the electric motor (MO) when the power supply of the actuator is switched on or when a switch-on signal for moving the actuating element from a safe idle position to an actuation position is received, - wherein the actuator has a return spring (RF) for providing a return torque acting on the actuating element for automatically moving the actuating element into the safe idle position, in particular when the power supply for the actuator is lost, - wherein the flap connected to the actuator connection, or the valve connected to the actuator connection as well as the return spring (RF) exert an overall torque on the actuating element, wherein the overall torque brings about an overall rotor torque at the rotor (RO) via the reduction gear (G), - wherein the holding torque (MFH) applied by means of the electromagnet (E1, E2) to the rotor (RO) of the electric motor (MO) in the holding position is greater than the overall rotor torque acting on the rotor (RO), in particular at least 1.5 times to 3 times as great, and - wherein the control unit is configured to activate the electrical circuit arrangement on receipt of a switch-off signal in such a way that the electromagnet (E1, E2) switches from the holding position into the free running position, so that the actuating element is moved back automatically into the safe idle position, or - wherein the electrical circuit arrangement is configured in such a way that the electromagnet (E1, E2) switches from the holding position into the free running position when the power supply is lost, so that the actuating element is moved back automatically into the safe idle position.

10. Actuator according to one of the preceding claims, wherein the coil arrangement of the electrical circuit arrangement has an electrical coil (L), wherein the electrical coil (L) is connected in series with a capacitor (C), wherein the series circuit is connected by a first end to a common reverence potential, wherein a second end is able to be switched via a switching means (WS) of the electrical circuit arrangement to a supply voltage or to the common reference potential, wherein the inductance value of the electrical coil (L) and the capacitance value of the capacitor (C) are dimensioned in such a way that, when the second end of the series circuit is switched to the supply voltage, the first brief current pulse is able to be injected into the electrical coil (L) and, when the second end of the series circuit is switched to the common reference potential, the second brief current pulse is able to be injected into the electrical coil (L) with the reversed current direction.