Actuator

Abstract

Actuator (1, 16) with a motor (2), a gear (4, 17) coupled to the motor (2), an output (5), and a spring element that can be tensioned by means of the motor (2) and is designed to move the output (5) into a defined end position when the motor (2) is de-energized by energy stored in the tensioned spring element, wherein the actuator (2) has a controller (10) that is fed by induced back EMF (electromotive force) converted into electrical energy when the motor (2) is de-energized and is coupled to a sensor (13) for detecting the angle of rotation and / or the position of the output (5), wherein the controller (10) is designed to control the movement of the motor (2) as a function of the detected angle of rotation and / or the detected position of the output (5) before reaching the defined end position by generating a braking torque that counteracts the movement of the motor (2). to brake, characterized inthat the controller (10) is designed to increase the braking torque before reaching the defined end position, wherein the motor (2) is accommodated in an explosion-proof manner in an encapsulated housing (3) filled with a casting compound (15).

Description

The invention relates to an actuating drive having a motor, a transmission coupled to the motor, a drive output and a spring element which can be tensioned by means of the motor and is designed to move the drive output into a defined end position when the motor is not energized by energy stored in the tensioned spring element, wherein the actuating drive has a controller which is fed by induced back electromotive force (electromotive force) converted into electrical energy when the motor is not energized and which is coupled to a sensor for detecting the angle of rotation and / or the position of the drive output, wherein the controller is designed to brake the movement of the motor as a function of the detected angle of rotation and / or the detected position of the drive output before reaching the defined end position by generating a braking torque counteracting the movement of the motor.A generic actuator is known from DE 10 2015 200 289 A1. The electromechanical drive described there is provided for actuating a movable leaf of a door. When the wing is opened by an electric motor, a mechanical energy store is charged, which is discharged again when it is closed. The movement of the wing is braked by means of a brake device. In an emergency operation, the electric motor is operated as a generator and electrical energy is stored in a capacitor for supplying energy to an emergency control electronics.Such actuators with spring return are used for actuating actuators, in particular flaps in heating, air conditioning and ventilation systems. Actuating drives, which are also referred to as spring return drives, have a restoring spring which is tensioned by an electric motor and a reduction gear coupled thereto. The energy stored in the return spring is released as soon as the electric motor becomes de-energized. The spring return ensures that in the event of a power failure the actuator, in particular the flap, is moved into a defined end position. Usually, the defined end position is a closed position. Such an actuator is known from EP 0 697 546 A1.For certain applications, actuating drives are also used in which the flap is open in the end position.From EP 0 697 571 A1 an actuator is known which has a braking device to conserve the reduction gear during spring return.Adjusting drives in which the restoring movement is terminated by a mechanical stop have a limited service life due to the impact-like load occurring. It has therefore already been proposed to provide a hydraulic damper or a freewheel in order to reduce the loads occurring when the end position is reached or when it hits an end stop.The invention is therefore based on the object of specifying an actuating drive in which no impact-like load occurs when the end position is reached.To achieve this object, an actuating drive having the features of claim 1 is provided.In the actuator according to the invention, the controller is designed to increase the braking torque before reaching the defined end position, wherein the motor is accommodated in an encapsulated housing filled with a potting compound in an explosion-proof manner.The invention is based on the finding that the back EMF induced during spring return can be used to supply an electrical energy to a controller. The controller initiates a targeted braking of the movement of the output before reaching the end position and thus before impacting an end stop. This results in the advantage that no separate power supply, in particular no separate power supply for the controller, is required. The desired braking during the spring return therefore also works if the spring return is triggered on account of a power failure of the power supply of the motor. If the power supply of the motor is switched off or has failed, the motor is automatically moved into the defined end position under the action of the energy stored in the spring element. In this operating state, the motor acts as a generator, so that a voltage is generated at the terminals of the motor and can be tapped. The kinetic energy present during the spring return is at least partially converted into electrical energy which is available to the controller as operating voltage. The controller influences the spring return in such a way that it generates a braking torque that is opposite to the direction of rotation of the spring return, whereby the mechanical spring return and thus the movement of the transmission coupled to the motor and of the output drive are braked in a controlled manner and finally stopped completely. This results in the advantage that when the end position is reached, no force peaks occur which otherwise can lead to an early failure of transmission components and thus of the entire actuator in conventional actuating drives. The actuator according to the invention is thus distinguished on the one hand by a particularly simple construction and on the other hand by a long service life.In the actuator according to the invention, the controller is designed to brake the movement of the motor as a function of the detected angle of rotation of the output and / or the detected position of the output. This has the advantage that the braking behavior and in particular the generated braking torque can be matched exactly to the current angle of rotation and / or the current position of the output drive. For example, the braking torque can be changed, in particular increased, in a desired manner depending on the angle of rotation or depending on the position of the output drive. As a result, the rotational speed of the output drive or of a transmission component mechanically coupled thereto can be reduced in a controlled manner.In the actuator according to the invention, it is provided that the controller is designed to increase the braking torque before the defined end position is reached. In this way, progressive deceleration of the output drive can be effected, whereby an impact-like impact of the output drive or of a transmission component connected thereto, for example the impact of a gearwheel segment against an end stop, can be prevented or greatly reduced. It can also be provided that each angle of rotation of the output is assigned a specific braking torque, which is controlled by the controller. Similarly, a particular position of the output may be associated with a particular braking torque generated by the controller. The braking torque is generated by means of the induced electromotive force, which can be tapped at the motor terminals when the motor is not energized. The electrical energy generated during the generator mode of the engine is used by the controller to generate the braking torque.It is also within the scope of the invention that the sensor for detecting the angle of rotation and / or the position is a contactless sensor. A contactless sensor is characterized by a simple mechanical construction. In particular, no mechanical connection is required between a moving component, for example the output, and a stationary sensor component.According to a variant of the actuator according to the invention, the sensor can be a magnetic encoder cooperating with a permanent magnet. A permanent magnet generates a magnetic field whose magnetic field lines can be detected by means of the magnet encoder. The magnetic encoder supplies a signal which comprises information regarding the angle of rotation and / or the position of the output or a component of the transmission connected to the output.According to the invention, it can be provided that the permanent magnet is arranged on or on a shaft or on or on a gearwheel of a next-to-last transmission stage before the output drive. In this way, the resolution of the sensor increases.A variant of the actuator according to the invention is particularly preferred, in which the sensor is arranged in a housing or embedded in a casting compound. In such a configuration, the sensor is reliably protected from external influences, whereby the operational reliability is increased. A contactless sensor can be arranged or embedded in the housing or in the casting compound in which the motor is located, since contactless measurement of the angle of rotation or the position of the moving component is possible.According to an alternative embodiment, the angle-of-rotation sensor can be a potentiometer. The potentiometer comprises a stationary component which can be arranged, for example, on a base body, for example on the housing in which the motor is accommodated. In addition, the potentiometer comprises a movable component, for example a section which can be rotated together with the output and is arranged thereon. The rotatable section is firmly connected to the output drive, so that the current angle of rotation or the current position of the output drive can be detected on the basis of the current resistance value of the potentiometer.A preferred embodiment of the actuator according to the invention provides that the sensor is also accommodated in a housing designed to be explosion-proof. This results in the particular advantage that no passage of a sensor component, for example a potentiometer shaft, through or into an encapsulated and explosion-proof region is necessary. Due to the preferably explosion-proof housing, the actuator according to the invention can also be used in environments in which explosive gases or other explosive substances are present.In the actuator according to the invention, it is also possible for the controller to be electrically connected to the motor in such a way that, when the motor is not energized, the controller is moved from a rest state into an active state by the counter-EMF generated. During normal operation, the controller is preferably inactive, i.e., in a sleep state. In this state, the controller does not consume power. When the motor is de-energized, the safety function of the actuator is activated and the spring return is triggered under the action of the energy stored in the spring. By means of the back EMF generated by induction, the controller is supplied with electrical energy and automatically set into the active state.In a further embodiment of the invention, it can be provided that the controller of the actuator according to the invention is connected to an electrical energy store. The electrical energy store can be designed as a capacitor, as a supercapacitor (supercap), as a battery or as a rechargeable battery.The invention is explained below on the basis of exemplary embodiments with reference to the drawings. The drawings are schematic representations and show: FIG. 1 shows a schematic sectional side view of an actuator according to the invention, FIG. 2 shows a view of the transmission of the actuator according to the invention shown in FIG. 1, and FIG. 3 shows a further exemplary embodiment of an actuator according to the invention in a sectional side view.The actuator 1 shown in a sectional view in FIG. 1 comprises a motor 2 which is accommodated in a housing 3 in an explosion-proof manner. The housing 3 is encapsulated and filled with a potting compound 15.The engine 2 is coupled to a transmission 4, shown schematically. The transmission 4 is designed as a reduction gear and reduces the speed of the motor shaft to a lower speed of an output 5, the output 5 being coupled in a rotationally fixed manner to a hollow shaft 6, into which a shaft (not shown) can be inserted, by means of which a flap or the like can be actuated. The output drive 5 is designed such that it enables a rotation of approximately 90°.FIG. 2 shows the essential components of the transmission 4 of the actuating drive 1 shown in FIG. 1, an output shaft 7 of the motor 2 is coupled via a plurality of gearwheels which are in engagement with one another to a gearwheel segment 9 of the output drive 5, which is coupled rotationally fixedly to the hollow shaft 6.The transmission 4 comprises a spring element (not shown) designed as a torsion spring, which serves as an energy store.When the motor 2 is switched on, the output shaft 7 is rotated, which rotates the output 5 through 90° by means of the components of the transmission 4, whereby a flap coupled to the hollow shaft 6 is actuated. Usually, the flap is thereby opened. This rotational movement stresses the spring element. When a safety function is triggered, the motor 2 is switched off. The same situation occurs when a power failure occurs. In this case, the tensioned spring element accelerates the components of the transmission 4 and the motor 2 coupled thereto. the direction of rotation is opposite to the direction of rotation during operation of the motor 2. the potential energy stored in the spring element is converted into kinetic energy. At the same time, the flap coupled to the output drive 5 or another component coupled to the output drive 5 is moved into a fixed position, usually the flap is closed. Alternatively, the actuating drive can also be designed such that the flap is in an open position in the end position.Under the action of the energy stored in the spring element, the gears of the transmission 4 are accelerated. It can be seen in FIG. 1 that the actuating drive 1 has a controller 10 which interacts with a sensor 13 which is arranged in the housing 3. In this exemplary embodiment, the sensor 13 is designed as a contactless sensor and interacts with a permanent magnet 11 arranged on the outside of the hollow shaft 6. The sensor 13 is a magnetic encoder. By means of the sensor 13, the angle of rotation of the output drive 5 or of the gearwheel segment 9 connected thereto in a rotationally fixed manner can be detected. The controller 10 is configured to decelerate the clockwise rotation of the motor 2 by generating a braking torque opposing the movement of the motor 2.It can be seen in FIG. 2 that a stop 12 is assigned to the gearwheel segment 9. In order to prevent the gearwheel segment 9 from impacting the stop 12 in an un-braked manner when the end position is reached, the controller 10 decelerates the rotational movement of the motor 2 and of the gearwheel segment 9 coupled thereto via the transmission 4.The controller 10 permanently monitors the state of the actuating drive 1. If the power supply to the motor 2 is omitted, the controller 10 is supplied with electrical energy by the movement of the output 5 and of the gearwheel segment 9 triggered by the spring element and is set into an active state. The electric power supplied to the controller 10 is based on the electromotive force generated by the spring member that accelerates the motor 2 in the reverse rotational direction. In this state, the engine 2 is operated as a generator. The voltage induced at the terminals of the motor 2 is used to supply power to the controller 10.The sensor 13 designed as a magnet encoder comprises the permanent magnet 11 attached to the output 5. The back EMF induced voltage is used by the controller 10 to generate a braking torque for braking the motor 2. In the exemplary embodiment shown in FIG. 2, the braking torque acts counterclockwise, counter to the direction of rotation of the gearwheel segment 9, and the transmission 4 and the output 5 are accordingly also braked. The magnitude of the braking torque is dependent on the detected angle of rotation. When an edge 14 of the gear segment 9 approaches the stop 12, the braking torque is increased, so that the movement is stopped or at least greatly braked shortly before an impact, so that no or only a small, non-critical impulse arises in the event of contact between the edge 14 of the gear segment 9 and the stop 12. Since the mechanical load of the components of the transmission 4 can be significantly reduced in this way, the service life of the transmission 4 is considerably increased.The housing 3, which contains both the motor 2 and the sensor 13 designed as a magnetic encoder and the controller 10, is encapsulated with the encapsulation compound 15. The motor 2 is encapsulated in an explosion-proof manner. The contactless detection of the angle of rotation offers the advantage that no passage of the sensor 13 through the explosion-proof encapsulated housing 3 is necessary.FIG. 3 is a sectional view showing another embodiment of an actuator 16. The output shaft 7 connects the motor 2 to a transmission 17, which comprises a plurality of transmission stages and the output 5 of which is coupled to the hollow shaft 6. The controller 10 is located in the housing 3 encapsulated with potting compound 15. The sensor 13 is also located within the housing 3, which sensor is designed to detect the angle of rotation and / or the position of the output drive 5.The sensor 13 is a contactless sensor which is designed as a magnetic encoder. The sensor 13 interacts with a permanent magnet 18 placed at the next to last stage of the gearbox 4. The permanent magnet 18 is thus located one step in front of the output 5. By arranging the permanent magnet 18 at the next-to-last transmission stage as shown in FIG. 3, the sensor 13 designed as a magnet encoder can detect a rotational angle range of approximately 330°. This results in the advantage that the current angle of rotation of the output drive 5 or its position can be detected with a higher accuracy and resolution. In the embodiment shown, the permanent magnet 18 is located in a bore at one end of a shaft 19 of the transmission 4. According to the first embodiment, the permanent magnet 18 faces the sensor 13, whereby non-contact detection is possible by the case 3 made of, for example, aluminum and sealed with the sealing compound 15.List of reference characters1 Actuating drive 2 Motor 3 Housing 4 Transmission 5 Output 6 Hollow shaft 7 Output shaft 8 Gearwheel 9 Gearwheel segment 10 Controller 11 Permanent magnet 12 Stop 13 Sensor 14 Edge 15 Potting compound 16 Actuating drive 17 Transmission 18 Permanent magnet 19 Shaft

Claims

Actuator (1, 16) having a motor (2), a transmission (4, 17) coupled to the motor (2), an output drive (5) and a spring element which can be tensioned by means of the motor (2) and is designed to move the output drive (5) into a defined end position when the motor (2) is not energized by energy stored in the tensioned spring element, wherein the actuator (2) has a controller (10) which is fed by induced back EMF (electromotive force) converted into electrical energy when the motor (2) is not energized and which is coupled to a sensor (13) for detecting the angle of rotation and / or the position of the output drive (5), wherein the controller (10) is designed to sense the electrical energy and to sense the electrical energy and to sense the electrical energy in the direction of the output drive (5), the movement of the motor (2) as a function of the detected angle of rotation and / or the detected position of the output drive (5) before reaching the defined end position by generating a braking torque counteracting the movement of the motor (2), characterized in that the controller (10) is designed to increase the braking torque before reaching the defined end position, wherein the motor (2) is accommodated in an encapsulated housing (3) filled with a casting compound (15) in an explosion-proof manner.Actuator according to claim 1, characterised in that the sensor (13) for detecting the angle of rotation and / or the position is a contactless sensor (13).Actuator according to one of the preceding claims, characterized in that the sensor (13) is a magnet encoder interacting with a permanent magnet (11, 18).Actuator according to Claim 2 or 3, characterized in that the sensor (13) is arranged in a housing (3) and / or is embedded in a potting compound (15).Actuator according to Claim 3, characterized in that the permanent magnet (18) is arranged on or on a shaft (19) or a gearwheel of a next-to-last transmission stage upstream of the output (5).Actuator according to Claim 1, characterized in that the sensor for detecting the angle of rotation is a potentiometer.Actuator according to one of the preceding claims, characterized in that the sensor (13) is accommodated in the housing (3) designed to be explosion-proof.Actuator according to one of the preceding claims, characterized in that the controller (10) is electrically connected to the motor (2) in such a way that, when the motor (2) is not powered, the controller (10) is set from a rest state into an active state by the counter-EMF generated.Actuator according to one of the preceding claims, characterized in that the controller (10) is connected to an electrical energy store which is preferably designed as a capacitor.

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