Drive unit for a robot joint

Abstract

The invention relates to a drive unit (4) for a joint (2) of a robot (1), comprising a drive unit (5) and a gear unit (6) operatively connected thereto, wherein the gear unit (6) comprises a globoidal worm shaft (7) and a gear stage (8). The invention further relates to a joint (2) for a robot (1), comprising such a drive unit (4). The invention also relates to a robot (1) with such a joint (2).

Description

[0001] The invention relates to a drive device for a robot joint, comprising a drive unit and a gear unit operatively connected thereto. The invention further relates to a robot joint with such a drive device. The invention also relates to a robot with such a joint, wherein the joint is operatively connected to an arm segment.

[0002] Cobot systems are increasingly being used in various fields and facilities. This has led to a situation where human workers increasingly share the same space with cobot systems. These robots are designed for particularly collaborative capabilities. For example, movements are intended to stop if objects or workers enter the robot's movement area to prevent damage and injury. Such robots feature so-called "cobot drive joints," which are drive units located in the robot's joints. The term "cobot drive joint" is a combination of "cobot" (collaborative robot) and "drive joint." The drive unit is essential for the mobility and precision of cobots and enables them to work safely alongside humans in a shared work environment.These drive systems often use so-called harmonic drive / harmonic gearboxes.

[0003] For example, US patent 2019 / 305618 A1 discloses a robot drive unit comprising a first element and a second element that rotate relative to a predetermined axis. The robot drive unit includes a housing attached to the first element and an output shaft element, which is supported by the housing so that it can rotate about the axis and is attached to the second element. Furthermore, the robot drive unit includes a hollow shaft, which has a cylindrical shape and is arranged coaxially with the axis. This shaft is attached to one of the housing and output shaft elements and supported by the other of the housing and output shaft elements, allowing it to rotate about the axis.Furthermore, rotary sealing elements are provided, each sealing one gap between the housing and the output shaft element and another between the hollow shaft and the housing and the output shaft element, while allowing relative rotation about the axis. The hollow shaft comprises a shaft body made of a non-ferrous material and a contact surface element attached to the shaft body.

[0004] The object of the invention is to provide a complete, integrated drive unit for a robot that accommodates all necessary components in an extremely confined space without restricting the robot's range of motion due to the risk of collision. Furthermore, the drive unit should have a comparatively low weight while simultaneously featuring an innovative design. This object is achieved by the subject matter of claim 1. Preferred embodiments are described in the dependent claims, the description, and the figures.

[0005] A drive unit according to the invention for a robot joint comprises a drive unit and a gear unit operatively connected thereto, wherein the gear unit has a globoidal worm shaft and a gear stage. In other words, the gear unit is designed as a globoidal gear or globoidal worm gear. The proposed drive unit offers precise and efficient power transmission in a compact design. A further advantage of the globoidal gear, particularly in contrast to previously known shaft gears, is that the globoidal worm shaft, often simply called a "worm," is self-locking. Due to the self-locking of the globoidal worm shaft, the need for an additional brake is eliminated, which reduces the manufacturing costs and complexity of the robot. The drive unit can therefore be operated without an additional brake. Components are thus saved.Furthermore, a control unit can be used more simply, i.e., with a reduced range of functions. This makes the drive system particularly suitable for use in collaborative robots (so-called "cobots").

[0006] The drive unit is an assembly that generates and transmits motion to perform a mechanical function. The drive unit and the gearbox unit together enable power transmission and motion control. The drive unit, preferably an electric motor, provides the mechanical energy. To do this, the drive unit converts electrical energy into rotary motion. The gearbox unit mechanically converts the drive power from the drive unit. It serves to adapt torque and speed to the requirements of the joint.

[0007] The globoidal worm shaft is a rotationally symmetrical gear element of the gearbox unit, which meshes with a worm wheel. Its geometry allows for a compact design and a self-locking effect, resulting in high precision and stability. The globoidal worm shaft preferably serves as the drive for the gearbox unit.

[0008] The gear stage enables the transmission between the globoidal worm shaft and the drive unit. Depending on the design, the gear stage can also accommodate an axial offset between the drive unit and the globoidal worm shaft. In one embodiment, the drive unit is designed as an electric motor, with the rotational axis of a rotor shaft of the electric motor arranged parallel to and spaced apart from the rotational axis of the globoidal worm shaft.

[0009] Preferably, the globoidal worm shaft is rotatably mounted in a main support. The main support forms at least part of the housing for the drive unit and the gearbox unit. The main support combines high stability with lightweight construction and integrates geometries for accommodating additional components. The main support has several openings, flange surfaces, interfaces, or the like for attaching and / or accommodating other robot components. As an integral component, the main support enables both mechanical load bearing and the attachment of other components. The main support is preferably made of aluminum using sand casting or die casting processes. The main support can be post-processed to achieve optimal weight reduction and load-bearing capacity.

[0010] Additional housing elements and / or enclosures may be provided, attached to the main beam. These may be made of plastic to save weight. The main beam, enclosures, and housing elements feature a modular design to facilitate easy maintenance and assembly.

[0011] The drive unit, designed as an electric motor, is controlled and its position regulated optionally via at least one output rotary encoder, at least one input rotary encoder, at least one Hall sensor, or a combination of these encoders and sensors. This allows for optimal position control and regulation of the drive unit.

[0012] Preferably, the globoidal worm shaft engages with a worm gear that is configured to be rotationally fixed to an output component. The worm gear serves as the output. The worm gear is rotatably mounted on the main support, for example, by means of ball bearings. This gives the worm gear high tilting stiffness. The worm gear can be rotationally fixed to an output component, in particular an output flange, which is designed to accommodate an actuator, an arm segment, or another driven component of the robot.

[0013] The worm gear preferably has an inner diameter through which a cable can be routed. The larger the inner diameter, the easier it is to implement a cable routing in the drive unit.

[0014] The invention includes the technical teaching that the gear stage comprises a worm gear connected to the globoid worm shaft in a rotationally fixed manner, which in turn is operatively connected to the drive unit.

[0015] The worm gear can be operatively connected to a pinion either directly or via at least one intermediate gear. The pinion forms the input component of the transmission stage. The pinion can be rotationally fixed to an output shaft of the drive unit, in particular a rotor shaft. In this sense, an intermediate gear is preferably arranged between the pinion and the worm gear, which enables flexible power transmission. It is conceivable that the transmission stage has two or more intermediate gears to achieve greater flexibility in the gear ratio. Preferably, each intermediate gear is axially fixed, for example by a combination of a wave spring and a washer.

[0016] In one embodiment, a threaded ring is provided that adjusts the preload of the bearing elements of the globoid worm shaft. This allows for fine-tuning to optimize functionality.

[0017] According to a second aspect of the invention, a joint for a robot comprises a drive unit according to the first aspect of the invention, wherein the drive unit is operatively connected to an arm segment of the robot on the output side. The integration of the drive unit into the joint improves the precision and efficiency of the robot. The drive unit can also be operatively connected to an actuator to extend the degrees of freedom of the arm segment.

[0018] The robot's joint is a connecting unit between two arm segments or between an arm segment and the robot's base, enabling precise motion control in multiple degrees of freedom. The joint forms the mechanical basis for the robot's mobility and contains the aforementioned drive unit. Due to the drive unit's compact design, the joint can be integrated into existing cobot arm segments without altering their range of motion.

[0019] According to a third aspect of the invention, a robot comprises a joint according to the second aspect of the invention and / or a drive unit according to the first aspect of the invention. The robot can be designed as an industrial robot for precise tasks such as assembly, inspection, or palletizing. Alternatively, the robot can be used in medical robotics, for example, in surgical assistance systems or rehabilitation robots. Furthermore, the robot can alternatively be a service robot, for example, in logistics, the food service industry, or healthcare. In particular, the robot can be a humanoid robot.

[0020] The above definitions and descriptions of technical effects, advantages and advantageous embodiments of the drive device according to the first aspect of the invention also apply mutatis mutandis to the joint according to the second aspect of the invention and to the robot according to the third aspect of the invention, and vice versa.

[0021] Further measures improving the invention are described in more detail below, together with a description of a preferred embodiment of the invention, with reference to the figures, wherein identical or similar components are provided with the same reference numeral. The figures show... Fig. 1 a highly schematic representation of a robot according to the invention, only partially depicted, with a joint according to the invention, Fig. 2 a schematic exploded view of a joint after Fig. 1 arranged, according to the invention drive device, Fig. 3 a first sectional view of the drive device according to the invention Fig. 2, Fig. 4 a second sectional view of the drive device according to the invention Fig. 2 and Fig. 3, and Fig. 5 a third sectional view of the drive device according to the invention Fig. 2 to Fig. 4.

[0022] According to Fig. 1 in conjunction with Fig. Figure 2 shows a robot 1, only partially depicted here. The robot 1 has a joint 2 to which an arm segment 3 is attached. The joint 2 includes a drive unit 4 to generate drive power and transmit it to the arm segment 3. The structure and function of the drive unit 4 are described in more detail below.

[0023] The drive unit 4 comprises, according to Fig. 2 to Fig. 5 a drive unit 5 and a gear unit 6 connected thereto. The gear unit 6 is a globoidal worm gear and includes a globoidal worm shaft 7, which meshes with a worm gear 12, and a gear stage 8 comprising a pinion 16, an intermediate gear 15 and a worm gear 14. The intermediate gear 15 transmits the power between the pinion 16 and the worm gear 14.

[0024] The drive unit 5 is designed as an electric motor. The electric motor exhibits the following characteristics: Fig. Figure 5 comprises a housing-fixed stator 35 and a rotatably arranged rotor 36. A rotor shaft 39 is non-rotatably connected to the pinion 16. A rotational axis 40 of the rotor shaft 39 is arranged parallel to a rotational axis 19 of the globoidal worm shaft 7. Fig. 2 A wave spring 37 is provided for motor preloading. The worm gear 14 is rotationally fixed to the globoid worm shaft 7.

[0025] The globoidal worm shaft 7 is mounted in a main support 9, which is designed as an aluminum casting, and rotatably supported by two bearing elements 18. The main support 9 forms the basic structure of the drive unit 4. A threaded ring 17 is provided to adjust the axial preload of the bearing elements 18. The main support 9 absorbs all loads and partially serves as a housing. Additional housing elements 20 are provided to spatially define the interior of the main support 9 and the drive unit 4, thus protecting it from external influences. These can be made of plastic and are attached to the main support 9 in the assembled state. The housing elements 20 therefore serve as protective enclosures for the drive unit 4. The main support 9 has geometries on almost all sides to accommodate further components of the robot 1.

[0026] An optional radial shaft seal 27 can be provided between the threaded ring 17 and the worm gear 14 if different lubrication systems are used for the globoid worm shaft 7 and the gears 14, 15, 16 of the gear unit 6. The radial shaft seal 27 can be omitted if the globoid worm shaft 7 and the gear unit 6 are lubricated with the same means.

[0027] The gearbox unit 6 with the gearbox pre-stage 8 is covered by a cover 24, which is fastened to the main support 9 by means of a set of screws 34. The electric motor is concealed by a shield 32, which is fastened to the main support 9 by means of a set of screws 33.

[0028] The worm gear 12 serves as the output of the drive unit 4 and is also rotatably mounted in the main support 9 by two bearing elements 21, 30. The worm gear 12 has a large inner diameter 22 in order to accommodate Fig.3 to enable the passage of cables 38 in a simple manner. The bearing element 30 is axially preloaded by means of a washer 28 and a wave spring 29. The worm gear 12 is also rotationally fixed to an output component 13 in the form of an output flange via a first set of screws 23, wherein a threaded ring 31 is arranged axially between the worm gear 12 and the output component 13 for axial preloading of the bearing element 21.

[0029] Furthermore, a control unit 25 is provided for controlling the electric motor. The control unit 25 is attached to the main support 9 via a bracket 26. The control unit 25 is connected via signal transmission to an input rotary encoder 10 on the electric motor and an output rotary encoder 11 on the worm gear 12, thereby enabling position control of the drive unit 5 and the electric motor, respectively.

[0030] In operation, precise power transmission with simultaneous self-locking is ensured, thus eliminating the need for an additional brake. The component arrangement enables cost-effective manufacturing while adhering to weight specifications. Reference symbol list 1 robot 2 joint 3 arm segment 4 Drive unit 5 Drive unit 6 Gear unit 7 Globoid worm shaft 8 Gear pre-stage 9 main supports 10 Input rotary encoders 11 Output rotary encoder 12 worm gear 13 Drive component 14 Worm gear of the gearbox pre-stage 15 Intermediate gear of the gearbox pre-stage 16 pinions of the gearbox pre-stage 17 threaded ring 18 Bearing element of the globoid worm shaft 19 Rotation axis of the globoid worm shaft 20 Housing element 21 Bearing element of the worm gear 22 inner diameter 23 screws 24 lids 25 Control unit 26 holders 27 Radial shaft seal 28 disc 29 wave spring 30 Bearing element of the worm gear 31 Threaded ring 32 sign 33 screw 34 screw 35 Stator 36 Rotor 37 wave spring 38 cables 39 Rotor shaft 40 Rotation axis of the rotor shaft QUOTES INCLUDED IN THE DESCRIPTION

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

[0000] US 2019 / 305618 A1

[0003]

Claims

[1] Drive unit (4) for a joint (2) of a robot (1), comprising a drive unit (5) and a gear unit (6) operatively connected thereto, characterized by , that the gear unit (6) comprises a globoid worm shaft (7) and a gear stage (8). [2] Drive device (4) according to claim 1, characterized by , that the globoid worm shaft (7) is rotatably mounted in a main support (9). [3] Drive device (4) according to claim 1 or claim 2, characterized by , that the drive unit (5) is designed as an electric motor, wherein a rotation axis (40) of a rotor shaft (39) is arranged parallel to a rotation axis (19) of the globoid worm shaft (7). [4] Drive device (4) according to claim 3, characterized by , that an input rotary encoder (10), an output rotary encoder (11) and / or a Hall sensor is or are provided for position control of the electric motor. [5] Drive device (4) according to one of the preceding claims, characterized by , that the globoid worm shaft (7) is in tooth mesh with a worm wheel (12) which is designed to be rotationally fixed to an output component (13). [6] Drive device (4) according to one of the preceding claims, characterized by , that the gear stage (8) comprises a worm gear (14) which is non-rotatably connected to the globoid worm shaft (7) and which in turn is operatively connected to the drive unit (5). [7] Drive device (4) according to claim 6, characterized by , that at least one intermediate gear (15) is effectively arranged between a pinion (16) and the worm gear (14). [8] Drive device (4) according to one of the preceding claims, characterized by a threaded ring (17) for adjusting a preload of at least one bearing element (18) of the globoid worm shaft (7). [9] Joint (2) for a robot (1), comprising a drive unit (4) according to one of the preceding claims, wherein the drive unit (4) is operatively connected to an arm segment (3) of the robot (1) on the output side. [10] Robot (1) comprising a joint (2) according to claim 9 and / or a drive unit (4) according to any one of claims 1 to 8.

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