Technical Field

The invention relates to a DC motor actuator, developed as an alternative to servo and smart step motors, capable of precise position control in short strokes.

State of the Art

An actuator is a type of gear motor that drives/moves a mechanism or system. It is operated by an energy source. This source is usually electric current, hydraulic fluid pressure, or pneumatic pressure, and is converted into energy by some types of motion. There are numerous linear actuators composed of classical rack and pinion actuator. The rack and pinion actuators consist of a screw - threaded rod, usually fastened by the corresponding gear of a wheel driven by an electric motor.

Today, servo motors or smart step motors are used to perform positioning due to transmission mechanisims with a precision of 0.05 mm or higher. A servo is an automatic device that monitors the operation of any mechanism with the help of an auxiliary feedback mechanism by detecting the error and correcting the error. It is the most widely used type of engine in robot technology. The smart step motor is a brushless DC motor that rotates step by step. It is useful because it can be fully positioned without any feedback sensors representing an open loop controller. The smart step motor consists of a rotor, which is usually a permanent magnet, and is surrounded by stator windings. These servo and smart step motors are suitable for use in continuous running automation applications. However, its use is obliged due to the lack of an available alternative that will operate in automation applications where a position sensitivity above 0.05mm is required but continuous operation is not required (for example a displacement is performed 1 - 100 times in 8 hours); where operations such as pulling towards or pushing away from each other work pieces and shafts in machining and cutting.

These servo and smart step motors increase the cost of the machine produced since they are constly. Not only are the costs of the motors themselves are in question, but also the costs of the machine elements such as Couplings, Screw Shafts and Screw Bearings that connect each other the systems that is to be moved by these. On top of this, it is necessary to add the labor cost of the assembly of the machine elements with servo and step motors. These are substantial costs considering the competitive environment in the market. Therefore, a system that can perform position control via a DC motor actuator is assessed as a more cost - effective solution to accomplish this task.

Today, gear motors with reducers have been developed to achieve the desired torque level. One of the mentioned motors is the invention of patent application no. W02005CH00487. The invention relates to an actuator for actuating a device linearly by means of a tangential rod that can be displaced longitudinally by rotating the torque of a motor - driven pinion, especially for a cover or for a valve. According to the mentioned invention, a normal gear rod, which can be displaced in its axial direction and cut to an individual length, has a radius fixed by rotating towards the actuator. The pinion is positively connected to at least one drive wheel mounted freely rotating and an elastic and/or adjustable pressure element that allows the drive wheels and normal toothed rod to be freely engaged.

Another invention of the patent application no. US19910718292. The invention relates to a gear speed reducer with an input shaft comprising a worm gear mounted on an output shaft and placed at a fixed distance at right angles relative to the input shaft. The worm gear comprises a screw thread that gradually becomes thinner from one end to the other. An adjustable cartridge rotatably mounts one end of the shaft, and the cartridge can be adjusted by inserting a new section of the worm gear into the infinite gear to remove the gap between them, in order to allow axial adjustment of the shaft. Setting is done quickly and easily without having to take the gearbox out of service.

Another invention of the application no. EP20040000714. The invention relates to a fast - moving linear actuator of the type involving a gear wheel connected to motor means holding a corresponding sliding gear stick. The mentioned rod is cylindrical and has threads formed by a spiral gear, and the mentioned gear wheel is in a form that adapt to the shape of the rod. The mentioned actuator is cheaper than the conventional rack and pinion actuators and operates more quietly.

As a result, the requirement for a DC motor actuator, which eliminates the disadvantages of the existing technique, and the lack of existing solutions regarding precise positioning have made it necessary to make an improvement in the related technical field.

Brief Description of the Invention

The present invention relates to a DC motor Actuator that that meet the aforementioned requirements, operates with short strokes (0 - 100mm) where high precision positioning is required, which overcomes the cost and assembling disadvantages of Servo and Smart Step Motors and provide further advantages, and as an alternative to servo and smart step motors, is able to perform positioning with a precision of 0.05 mm or higher.

Based on the state of the art, the aim purpose of the invention is to provide an alternative structure to servo and smart step motors, which perform the same task in the specified stroke range, which can be assembled with less labor and is less costly, with the DC motor actuator developed.

The purpose of the invention is to ensure that the backlash between the gearboxes and the moving shaft itself are removed by means of the spring introduced in the DC motor actuator.

Another purpose of the invention is to allow performance of precise back - and - forth strokes with the removal of backlashes by means of the spring introduced in the DC motor actuator.

Another purpose of the invention is that back and forth strokes are identified separately by means of two reed switches introduced in the DC motor.

Another purpose of the invention is to determine the operating range by taking additional Stroke Limit reference information in addition to the turn information received from available Hall Effect Sensor, by means of the reed switch introduced in the DC motor Actuator.

Another purpose of the invention is to prevent the inner shaft to slip backwards amd to avoid any collisions by means of the Mechanical Stroke Limit introduced in the DC motor Actuator.

Another purpose of the invention is to ensure that the DC motor Actuator serves the same function as servo and smart step motors in terms of the mentioned stroke intervals and Running Time Conditions, while achieving affordable machine production due to the lower cost in comparison with these motors.

The structural and characteristic features and all advantages of the invention will be understood more clearly through the detailed explanation written with the following figures and references to these figures, and therefore assessment should be made by considering these figures and detailed explanation.

Brief Description of Drawings

The structure of the present invention and its advantages with further elements will become clear based on the drawings described below. Figure - 1 ; an outside schematic overview of the DC motor Actuator of the invention in assembled state,

Figure - 2; is a schematic overview of the elements introduced inside the DC motor Actuator of the invention in assembled state,

Figure - 3; a schematic overview of the DC motor Actuator of the invention in disassembled state,

Figure - 4; schematic overview of Position Control Mechanism,

Figure - 5; is a schematic overview of the Mechanical Stroke Limit mechanism.

Reference Numbers 100. DC motor actuator 200. Actuator 210. Actuator shaft 220. Motor compartment 300. Position control module 310. Back cover

320. Backlash removal element

321 . Fixing element

330. Sensor carrier profile

331 . Adjustment gap

332. Motor Connection Profile

333. Freeplay Screw Hole

340. Magnet positioning module

341 . Magnet connector part

342. Magnet (or magnets)

350. Sensor positioning profile

351 . Sensor

352. Sensor positioning element 360. Mechanical limiter Detailed Description of the Invention

In this detailed description, the DC motor Actuator (100) of the invention alternative to servo and smart step motors, that is capable of performing precise position control in short strokes, is explained only as an example for better understanding of the subject and without any imposing any limitations.

The DC motor actuator (100) shown in Figure - 1 comprises a linear actuator (200) with standard worm gear and a position control module (300). The actuator (200) shown in Figure - 2 comprises an actuator shaft (210) with worm gear on it and motor compartment (220) that enables the movement of this actuator shaft (210). The position control module (300) positioned in connection with said actuator (200) provides increased precision of the movement of the actuator shaft (210) and provides position control of the back and forth motion of the actuator shaft (210) by sensing its motion. The backlash removal element

(320), which is introduced on the mentioned position control module (300) which is enclosed by the back cover on the open back side, reduces the backlash of the actuator shaft with the internal backlashes caused by the actuator shaft while the actuator shaft (210) passes through the actuator (200) during its linear of the actuator shaft. The mentioned backlash removal element (320) is connected by means of a fixing element

(321) so that it is not dislodged. The magnet (or magnets) positioning module (340), which is connected to the mentioned actuator shaft (210), houses the magnet (or magnets) (342). The positions of the sensors (351) which sense the back and forth motion of the mentioned actuator shaft (210) is adjusted by the moving sensor positioning profile (350) on a sensor carrier profile (330) connected to the magnet positioning module (340).

The sensor carrier profile (330) shown in Figure - 3 is connected to the actuator (200) by means of a hole on a monolithic motor connection profile (332) formed by bending. The mentioned motor connection profile (332) is connected to the actuator (200) via a Freeplay Screw Hole (333). The mentioned sensor carrier profile (330) has an adjustment gap (331) that allows the positioning of the sensor positioning profile (350) to be adjusted.

The magnet positioning module (340) shown in Figure - 4 contains a magnet (or magnets) (342) for sensors (351) to detect the motion of the actuator shaft (210). The mentioned magnet (or magnets) (342) are connected to a magnet connector part (341). The mentioned sensors (351) are magnetic, electromechanical and similar position sensing elements such as Reed switches or Micro switches, which detect the motion of the magnet (or magnets) (342) connected to the actuator shaft (210) and generate an output by detecting that the actuator shaft (210) is in the forward or backward stroke reference position. This output data and the lap count of the hall effect sensor allow determination of the position of the actuator shaft (210). The mentioned sensors (351) are positioned on a sensor positioning profile (350). A sensor positioning element (352) is introduced to connect the mentioned sensors (351) to the sensor carrier profile (330).

In the mentioned DC motor actuator (100), a mechanical limiter (360) shown in Figure - 5 is positioned to prevent the actuator shaft (210) from slipping back into the actuator (200) due to any problem. The mentioned mechanical limiter (360) is connected to the actuator shaft (210).

The DC motor actuator (100) of the invention, using a linear actuator (200) with a worm gear without the precision at the desired level, as an alternative to servo and smart step motors, can perform precise movements in short strokes. Since the precision of the said linear actuator (200) is not at the desired level, a backlash removal element (320) has been introduced in the actuator shaft (210). The mentioned backlash removal element (320), removes the internal reducer backlash and the total backlash of the screw shaft during the linear motion of the actuator shaft (210) as it passes through the actuator (200), by pushing the actuator shaft (210) backwards. Thereby, the position sensitivity of the actuator (200) reaches the desired level. Also; position control of the actuator (200) is performed with increased precision by means of a magnet positioning module (340) connected to said actuator shaft (210), magnet (or magnets) (342) connected to this magnet positioning module (340) and sensors (351) that detect a magnet (or magnets) (342) and determine back - and - forth stroke and the Hall Effect Sensor of the DC motor actuator (200). The mentioned back - and - forth stroke sensors (351) are connected to a sensor positioning profile (350), while the sensor positioning profile (350) is connected to a sensor carrier profile (330) to adjust the positions of the back - and - forth stroke sensors (351). The mentioned sensor positioning profile (350) is shifted within the adjustment gap (331) introduced in the sensor carrier profile (330), in order to adjust the positions of the back and forth stroke sensors (351). One of the mentioned eccentric sensors (351) is used for the forward stroke and the other for the backward stroke. Therefore, the magnet (or magnets) (342) connected to the actuator shaft (210) move between these sensors (351). When the magnet (or magnets) (342) approaches the sensor (351) positioned for forward stroke detection, the sensor (351) produces the data for forward stroke detection, and when it approaches the sensor (351) positioned for backward stroke detection, the sensor produces the data for backward stroke detection. These data can be combined with the lap count information from the Hall Effect sensor and processed on a controller so that the actuator shaft (210) can be positioned. Therefore, with the said position control, the actuator shaft (210) is positioned in a tolerance range of 0.05 - 0.01 mm +- 10 % by making back - and - forth stroke movement. In the mentioned DC motor actuator (100), sensors (351) can displace the magnet (or magnets) (342) and the magnet (or magnets) (342) can be positioned eccentrically. If the actuator shaft (210) starts moving inside the actuator (200) for some reason during these operations, the mechanical limiter (360) to which it is connected prevents it slipping into the actuator (200). The mentioned mechanical limiter (360) stops the actuator shaft (210) by applying pressure on the actuator (200) body during the motion of the actuator shaft (210) towards the inside.

In a preferred application of the invention, Plug & Play feature was introduced to the DC motor Actuator (100). To enable this feature, an electronic card has been installed in the housing of the DC motor Actuator (100) to serve as a driver and for communication. It is connected to the main processor of the machine or device to which the DC motor Actuator (100) is connected by a multi - pin cable from the output on the card. Thereby, a significant improvement in wiring costs and commissioning times has been achieved.