Robot arm with a freewheel clutch for limiting a transmissible torque on a rotating drive axis of an end effector of a robot, as well as robots

Abstract

Robot arm (503, 505) for a medical robot (501), with a freewheel clutch (121) for limiting a transmissible torque on a rotating drive axis (105) of an end effector of a medical robot, wherein the freewheel clutch (121) has an input side, a coupling element (123, 141) and an output side, wherein the input side can be mechanically connected to the output side by means of the coupling element (123, 141) for transmitting a torque and the coupling element (123, 141) is designed to be axially separable for breaking a connection when a limit torque is reached, wherein the coupling element (123, 141) has a drive element (123) connected to the input side and an output element (141) connected to the output side, wherein the drive element (123) and the output element (141) are held against each other by means of an axial pressure force. pressed, corresponding ramp-shaped surfaces (129,143) for transmitting the torque, such that the connection is interrupted upon reaching the limit torque by means of a sliding of the ramp-shaped surfaces (129, 143) against each other in the opposite direction of the axial pressure force, characterized in that a gear (107, 127) is assigned to the drive element (123) and / or the driven element (141), such that the input side and the output side are arranged in different axes of action (181, 191).

Description

[0001] The invention relates to a robot arm with a one-way clutch for limiting a transmittable torque on a rotating drive axis of an end effector of a robot, in particular a medical robot. The one-way clutch has an input side, a coupling element, and an output side. The input side can be mechanically connected to the output side by means of the coupling element for transmitting a torque, and the coupling element is designed to be axially separable for interrupting a connection when a limit torque is reached. Furthermore, the invention relates to a robot arm, in particular for a medical robot, with a one-way clutch, and to a robot, in particular a medical robot, with such a robot arm.

[0002] For robots, especially medical robots, effective limitation of the transmittable torque towards an end effector, for example, a drive shaft, is essential. Especially in such robots, a delayed or incomplete shutdown of the drive of such an end effector, or a failure to limit the drive torque, can lead to overloading of the end effector or to injury or even destruction of a patient being treated. Both negative effects must be reliably prevented.

[0003] Various solutions are known for this. Limiting the torque applied to the end effector can be achieved, for example, by software controlling a drive motor. This makes it possible, for example, to use a current measurement of the motor and a corresponding evaluation of the motor current in the software to shut down a drive motor in the event of overload or imminent overload. However, such software-implemented torque limitation is often only possible with a delay, so that even if the software successfully shuts down the motor, damage to mechanical components may already have occurred.

[0004] It is also known to separate end effectors using a predetermined breaking point, for example, one that is triggered at a specific torque. However, if such a predetermined breaking point is activated, it results in components having to be replaced or damage to other components. Furthermore, an ongoing operation, for example, cannot be continued with the same end effector, which can pose a risk to the patient and result in costs due to an extended operation time. In any case, high costs for repairs or additional labor are incurred.

[0005] US Pat. No. 6,132,435 A discloses a one-way clutch for limiting the transmittable torque for tightening a surgical screw. This clutch limits the maximum torsional moment by means of balls and a spring force. The balls are located in recesses in axially interacting discs and are pressed together by the spring force. Such a one-way clutch is constructed from a multitude of components and requires corresponding assembly effort.

[0006] DE 198 32 015 A1 describes an actuating device that serves as a clutch actuator in a motor vehicle. The actuating device comprises a spring-loaded multi-plate clutch with intermeshing, wave-shaped spur gears. It releases in the event of an overload moment, thus decoupling the drive torque.

[0007] DE 10 2019 133 159 A1 concerns an overload damper for a vehicle drive shaft. Here, too, spring-loaded, wave-shaped spur gears are used to implement the overload function.

[0008] EP 3 346 087 B1 discloses an overload clutch for an electric screwdriver. A spring-loaded spur gear serves as a torque limiter, with a trigger torque selectable using an adjustment ring.

[0009] DE 60 2004 011 451 T2 discloses a torque limitation, wherein a triggering torque for separating a drive of agricultural equipment is realized by means of a trapezoidal axial toothing under spring load.

[0010] DE 10 2012 009 149 A1 discloses a safety clutch for controlling functions in aircraft. Spur gear drive components achieve torque limitation, with the drive side being lockable when the safety clutch is triggered.

[0011] EP 3 483 477 A1 discloses a drive device for an aerodynamic flap on a vehicle. A slip clutch for limiting a potentially transmittable torque within a spur gear is disclosed.

[0012] The object of the invention is to improve the state of the art.

[0013] The object is achieved by a robot arm for a medical robot with a freewheel clutch for limiting a transmittable torque on a rotating drive axis of an end effector of a robot, in particular a medical robot, wherein the freewheel clutch has an input side, a coupling element and an output side, wherein the input side is mechanically connectable to the output side by means of the coupling element for transmitting a torque and the coupling element is designed to be axially separable for interrupting a connection when a limit torque is reached, wherein the coupling element has a drive element connected to the input side and an output element connected to the output side, wherein the drive element and the output element have mutually corresponding ramp-shaped surfaces pressed against one another by means of an axial compressive force for transmitting the torque,so that by sliding the ramp-shaped surfaces against each other against the axial compressive force, the connection is interrupted when the limit torque is reached.

[0014] Such a one-way clutch is simple to manufacture and requires few components. Furthermore, the transmittable limit torque can be determined by selecting an appropriate angle for the ramp-shaped surfaces. The limit torque can also be dependent on the selection of appropriate sliding properties and / or surface finish and / or materials used for interconnected components, or can even be defined by this selection. In conjunction with the corresponding axial compressive force, a defined limit torque is thus available for breaking the connection. Furthermore, such a one-way clutch is easy to manufacture and completely reversible with regard to breaking the connection. If the transmittable limit torque is again undershot, the input side is reconnected to the output side.According to the invention, a gear is assigned to the drive element and / or the output element, so that the input side and the output side are arranged in different effective axes.

[0015] This allows, for example, the input side—that is, the application of torque to the overrunning clutch—to be relocated from the main operating axis to a robot arm, for example. This makes the overrunning clutch particularly easy to integrate into an existing system.

[0016] The following terms are explained here:

[0017] A “drive axle” can be any rotary machine element that is suitable for transmitting a drive torque to the overrunning clutch, for example from a drive motor or an actuator.

[0018] In robotics, an "end effector" is known as the final element in a kinematic chain. For example, such an end effector can be a tool or manipulator at the tip of a robot arm. Such an end effector could be, for example, a gripper, a cutting instrument, a laser, a gripping unit, or another device that is suitable for fulfilling a desired application purpose of the robot together with the robot. For example, such an end effector could also consist of various actuators or functional units, each of which fulfills a specific application purpose together with the robot.

[0019] A "robot" is a technical device capable of performing repetitive or defined mechanical work. Robots are known as both stationary and mobile machines and are controlled by appropriate software. Robots have drive motors, for example, to drive different axes of movement of a robot so that corresponding forces can be applied to an end effector. In the present example, such a robot can also be a very small, delicate technical unit that assists in medical interventions or the medical treatment of a human or animal. Such a robot is designed, for example, as a 3-axis linear robot or as a multi-axis articulated-arm robot, in particular with 3 to 6 axes or even 7 or 8 axes.

[0020] An “input side” can be any side of the overrunning clutch connected to the drive axle, by means of which the torques supplied via the drive axle are introduced into the overrunning clutch.

[0021] A "coupling element" is, for example, a device for mechanically connecting the input side to an output side, particularly in a rotationally fixed but detachable manner. Such a coupling element is, for example, a claw clutch or a friction surface.

[0022] An “output side” is, for example, the side of the overrunning clutch, by means of which the torques transmitted via the input side and the coupling element from the overrunning clutch are passed back towards the end effector.

[0023] A “limit torque” is a defined torque selected, calculated or otherwise determined to protect the end effector, which is just large enough to safely prevent overloading of the end effector or damage to objects, persons or animals manipulated by the end effector.

[0024] "Axially separable" describes a separation direction that runs, in particular, along or substantially along a rotational axis of the input side and / or the output side, as well as the coupling element of the torque-transmitting overrunning clutch. In particular, during a corresponding separation process, one component is removed from another component along an axis and / or two components are disengaged from each other.

[0025] A “drive element” is a mechanical element of the coupling element, which can absorb torques coming from the input side in the coupling element and transmit them to an output element.

[0026] An “output element” is, for example, the part of the coupling element which absorbs the torque introduced by the drive element in the case of an active transmission or connection for the torque through the overrunning clutch and transmits it to the output side.

[0027] A "ramp-shaped surface" can be any surface inclined about a radial axis on the drive element and / or the output element, for example, on an end face of the drive element or the output element. For example, such a ramp-shaped surface is formed by a widened, prismatic arrangement on an end face of the drive element or the output element.

[0028] "Breaking" the connection describes the process in which the transmission of torque from the drive element to the output element is reliably prevented. If such an interruption occurs, the one-way clutch is "disconnected." In contrast, connecting the drive element and the output element would be equivalent to a "closed" or "coupled" one-way clutch, which can transmit torque.

[0029] A "gearbox" can be any machine element or any combination of machine elements by means of which motion quantities can be changed or converted. Such a gearbox can convert forces or torques, as well as the associated movements or speeds, into one another. The ratio of such a gearbox describes the relationship between an input speed and an output speed.

[0030] An “effective axis” can be any axis in which, for example, a drive axis or output axis runs, i.e. within which a technical effect is achieved or mechanical power is transmitted.

[0031] In order to achieve a soft interruption and a uniform separation of the coupling element, the ramp-shaped surfaces on the drive element and the ramp-shaped surfaces on the output element have the same ramp angle.

[0032] A “ramp angle” is the angle at which the ramp-shaped surface is arranged relative to an end face of the drive element or the output element arranged orthogonally to a longitudinal axis.

[0033] In one embodiment, the ramp-shaped surfaces are arranged radially, in particular symmetrically radially, on the drive element and on the output element.

[0034] Such a radial, particularly symmetrical radial, arrangement results in the overrunning clutch engaging and disengaging particularly smoothly and evenly, and the overrunning clutch is also easy to manufacture. Furthermore, the overrunning clutch can be achieved with consistent engagement and disengagement behavior regardless of the rotational position of the input and output sides relative to each other.

[0035] In order to be able to adjust the limit torque of the overrunning clutch, an adjusting element is arranged on the drive element and / or on the output element, whereby an angle of the respective ramp-shaped surfaces can be adjusted by means of the adjusting element.

[0036] An "adjustment element" can be any technical device that allows for the angle of the respective ramp-shaped surface to be adjusted. For example, such an adjustment element could be an adjusting screw, a wedge, a hydraulic device, or a spindle drive.

[0037] In one embodiment, the axial compressive force is applied by means of a spring, in particular a helical spring, acting axially on the drive element and / or the output element and supported on a fixed point of the overrunning clutch.

[0038] Such a spring, especially a coil spring, is inexpensive and readily available as a machine element. Furthermore, such a spring, especially a coil spring, has a defined spring characteristic curve. This makes it easy to determine the limit torque of the overrunning clutch.

[0039] A "fixed point" can be any boundary or component of the overrunning clutch, for example, part of a housing or surrounding technical equipment. Such a fixed point is particularly suitable for absorbing spring forces.

[0040] In order to be able to adjust the limit torque of the overrunning clutch even more easily and conveniently, the limit torque can be adjusted by adjusting a mechanical preload of the spring, in particular the coil spring, between the fixed point and the drive element and / or the output element.

[0041] Such adjustment of the preload of the mechanical spring can be achieved, for example, by moving the fixed point, in particular by means of a thread or a fixed point mounted in a thread. For example, the fixed point is a disk with an internal thread, which is guided on a shaft with an external thread. Furthermore, the spring can be shortened and the mechanical preload increased by means of one or more spacers, for example, disks, between the fixed point and the spring.

[0042] In order to make the transmission simple and reliable, the transmission has spur gears and / or a belt drive, in particular a toothed belt drive.

[0043] In one embodiment, the drive element and / or the output element is or are designed as a spur gear.

[0044] By designing the drive element and / or the output element as a spur gear, a transmission, in particular a spur gear, can be realized as compactly and simply as possible. Particularly when using a one-way clutch of the aforementioned embodiments within a medical robot, a compact design is essential to avoid having to make the medical robot too bulky.

[0045] In order to reliably detect an effective position or a corresponding position of an end effector, a sensor for determining a rotational position of the output element is assigned to the output side and / or the output element.

[0046] Using such a sensor, the rotational position of the output element can be reliably determined even if the overrunning clutch causes the connection to be interrupted when the limit torque is reached or exceeded. This allows, for example, a measured value from the sensor to be transmitted to a central control system, providing the central control system with clear information about the rotational position of the output element. This also allows the position or operating position of a respective end effector to be reliably determined.

[0047] In one embodiment, the sensor is a magnetic sensor, a Hall sensor, an optical sensor and / or an incremental encoder.

[0048] A magnetic sensor, a Hall sensor, an optical sensor and / or an incremental encoder are known elements of measurement technology and can be compactly and easily integrated into a freewheel clutch according to the invention.

[0049] In order to be able to process information about an interruption of the connection when the limit torque is reached in a higher-level control system of the robot, the sensor generates a signal for the rotational position of the output element, which can be transmitted to a control system of the robot or.

[0050] This also ensures that the robot's control system does not overload the end effector due to further movements or additional forces applied by the robot, or that a patient undergoing treatment is not harmed.

[0051] According to the invention, the object is achieved by a robot arm, in particular for a medical robot, with a freewheel clutch according to one of the previously described embodiments for limiting a drive torque for a drive axis of an end effector.

[0052] Such a robot arm with a freewheel clutch of the aforementioned embodiments provides a reliable and secure basis for end effectors to be mounted on the robot arm. In particular, the design of the robot arm itself ensures a safe limitation of the drive torque for the correspondingly mounted end effectors. The freewheel clutch can be designed such that the drive torque is sufficiently limited for one, several, or even all end effectors that can be mounted on this robot arm.

[0053] In a further aspect, the object is achieved by a robot, in particular by a medical robot, with a robot arm of the aforementioned embodiment. Such a robot is also designed in such a way that a corresponding end effector cannot be overloaded. Thus, such a robot can be used safely, especially in the treatment of human or animal patients.

[0054] The invention will be explained below using exemplary embodiments. Fig. 1 a schematic representation of a gearbox for an end effector drive of a medical robot with a freewheel clutch, Fig. 2 a schematic side view of the overrunning clutch of the Fig. 1, Fig. 3 a schematic side view of a drive wheel of the overrunning clutch of the Fig. 1, Fig. 4 a schematic representation of a control system for the end effector drive, as well as Fig. 5 a schematic representation of a medical robot with an end effector drive and an end effector.

[0055] A transmission 101 has a drive shaft 103 with a gear 107 mounted on the drive shaft 103 in a rotationally fixed manner. The drive shaft 103 is arranged for rotation about an axis 181 and is driven by a motor 161. The gear 107 serves to drive a one-way clutch 121 of the transmission 101.

[0056] The overrunning clutch 121 has a drive gear 123 with external teeth 127. The teeth 127 mesh with teeth 108 of the gear 107. Thus, the drive gear 123 is driven by the motor 161 via the drive shaft 103 and the gear 107.

[0057] The drive wheel 123 is rotatably mounted along an axis 191 by means of an auxiliary shaft 145. On one end face 130, the drive wheel has a claw toothing 129 with claws 133. Opposite the end face 130, a spring 151 is mounted on the drive wheel 123, which is supported on a stop 147 on the auxiliary shaft 145. The spring 151 exerts a compressive force between the stop 147 and the drive wheel 123. By displacing the stop 147 on the auxiliary shaft 145, the preload of the spring 151 can be adjusted (not shown in detail).

[0058] In an alternative, the spring 151 is arranged on the output shaft 105 and acts on the output shaft 141. A corresponding abutment is then arranged on the output shaft 105, analogous to the stop 147, and the output shaft 141 is arranged longitudinally displaceably but non-rotatably on the output shaft 105. For this purpose, a key connection is arranged, for example, between the output shaft 141 and the output shaft 105.

[0059] Opposite the drive gear 123, namely on its end face 130, an output shaft 141 is arranged along the axis 191. The output shaft also has a claw toothing 143 in the direction of the drive gear 123, which geometrically corresponds to the claw toothing 129. The output shaft 141 is connected to an output shaft 105 in a rotationally fixed manner.

[0060] The claw toothing 143 on the output shaft 141 engages with the claw toothing 129 on the drive gear 123. For this purpose, the drive gear 123 is pressed in the direction of the output shaft 141 by means of the spring 151.

[0061] The claw toothing 129 on the drive gear 123 has individual claws 133 arranged radially around the axis 191. The claws 133 are conically shaped, so that a claw angle 135 is formed between individual claws 133. The claw toothing 143 on the output shaft 141 is designed analogously and has an identical claw angle.

[0062] An increment strip 203 is arranged on a circumferential surface 142 of the output shaft 141, which can be read by a sensor 201. Thus, the rotational position of the output shaft 141 and thus of the output shaft 105 can be determined by means of the sensor 201. The sensor 201 is designed as an increment encoder.

[0063] The gear 101 is a component of an end-effector drive 210. In addition to the gear 101 and the sensor 201, the end-effector drive 210 includes a controller 211. A signal regarding the rotational position of the output shaft 105, determined by the sensor 201, can be transmitted to the controller 211 via a measuring line 215.

[0064] By means of a cable 213, the controller can then conduct current to the motor 161, so that by means of the motor 161, a torque can be conducted via the drive shaft 103 and the gear 107 into the transmission 101, controlled by the controller 211.

[0065] A robot 501 has a foot 502 and an arm 503. The arm 503 has joints 505. An end effector 511 is arranged at an end region 510 of the arm 503. The end effector 511 is driven by the motor 161 via the drive shaft 103 and protected by the gear 101 with the output shaft 105.

[0066] The function of the gearbox 101, the overrunning clutch 121 and the robot 501 with the end effector 511 will be explained below:

[0067] For example, assume that any desired manipulation is to be performed using robot 501 and end effector 511. End effector 511 is mechanically limited by an interfering contour (not shown). In the normal state, the torque introduced by motor 161 via drive shaft 103 into gearbox 101 is transmitted to output shaft 105 via the engaged overrunning clutch 121. This drives end effector 511.

[0068] If the end effector 511 is mechanically limited in its freedom of movement or, for example, blocked by the aforementioned interfering contour, the torque introduced by the motor 161 exceeds a maximum permissible limit torque for the end effector 511. This limit torque is mechanically determined by the claw angle 135 and the force applied by the spring 151 and is based on a maximum permissible torque for the end effector 511.

[0069] When the end effector 511 is mechanically limited, the output shaft 105 is now inhibited in its rotation about the axis 191. The claw teeth 129 and the claw teeth 143 now slide against each other due to the effective inclined planes of the respective claws and displace the drive gear 123 along a sliding path 195 in the direction of the stop 147. In the process, the spring 151 is compressed. The drive gear 123 is thus transferred to a freewheeling position, so that the mechanical connection between the drive gear 123 and the output shaft 141 is severed by the claw teeth 129 sliding relative to the claw teeth 143. The torque transmitted from the motor 161 toward the end effector 511 is thus interrupted.

[0070] Sensor 201 ensures that controller 211 receives information about the rotational position of output shaft 105 even though overrunning clutch 121 is no longer transmitting torque and thus no longer transmitting rotational movement. This allows controller 211 to detect any excess of the permissible torque.

[0071] The controller 211 reduces the torque generated by the motor 161, so that the drive wheel 123 is moved back along the sliding path 195 to its original position by means of the spring 151. The claw teeth 129 and the claw teeth 143 are thus re-engaged, so that a torque below the limit torque can be transmitted from the motor 161 to the end effector 511. The torque limitation by the overrunning clutch 121 is thus reversible. List of reference symbols 101 Gearboxes 103 Drive shaft 105 Output shaft 107 Gear 108 Gearing 121 Overrunning clutch 123 Drive wheel 127 Gearing 129 Claw toothing 130 front side 133 claws 135 claw angle 141 Output shaft 142 circumferential area 143 claw teeth 145 Auxiliary shaft 147 attack 151 spring 161 engine 181 Axis 191 Axis 195 sliding path 201 Sensor 203 increment strips 210 End effector drive 211 controllers 213 cables 215 measuring line 501 robots 502 feet 503 Arm 505 joint 510 End area 511 End effector

Claims

[1] Robot arm (503, 505) for a medical robot (501), with a freewheel clutch (121) for limiting a transmittable torque on a rotating drive axis (105) of an end effector of a medical robot, wherein the freewheel clutch (121) has an input side, a coupling element (123, 141) and an output side, wherein the input side is mechanically connectable to the output side by means of the coupling element (123, 141) for transmitting a torque and the coupling element (123, 141) is designed to be axially separable for interrupting a connection when a limit torque is reached, wherein the coupling element (123, 141) has a drive element (123) connected to the input side and an output element (141) connected to the output side, wherein the drive element (123) and the output element (141) are connected by means of an axial Compressive force pressed against each other, corresponding ramp-shaped surfaces (129,143) for transmitting the torque, so that by sliding the ramp-shaped surfaces (129, 143) against each other against the axial compressive force, the connection is interrupted when the limit torque is reached, , characterized by that a gear (107, 127) is assigned to the drive element (123) and / or the output element (141), so that the input side and the output side are arranged in different effective axes (181, 191). [2] Robot arm according to claim 1, characterized by that the ramp-shaped surfaces (129) on the drive element (123) and the ramp-shaped surfaces (143) on the output element (141) have the same ramp angle (135). [3] Robot arm according to claim 1 or 2, characterized by that the ramp-shaped surfaces (129, 143) are arranged radially on the drive element (123) and on the output element (141). [4] Robot arm according to one of the preceding claims, characterized bythat the axial compressive force is applied by means of a spring (151) acting axially on the drive element and / or on the output element and supported on a fixed point (147) of the overrunning clutch. [5] Robot arm according to claim 4, characterized by that the limit torque is adjustable by adjusting a mechanical preload of the spring (151) between the fixed point (147) and the drive element (123) and / or the output element (141). [6] Robot arm according to one of the preceding claims, characterized by that the gearbox has spur gears and / or a belt drive. [7] Robot arm according to claim 6, characterized by that the drive element (123) and / or the output element (141) is or are designed as a gear. [8] Robot arm according to one of the preceding claims, characterized bythat the output side and / or the output element (141) is assigned a sensor (201) for determining a rotational position of the output element (141). [9] Robot arm according to claim 8, characterized by that the sensor (201) is a magnetic sensor, a Hall sensor, an optical sensor and / or an incremental encoder. [10] Robot arm according to claim 8 or 9, characterized by that the sensor (201) generates a signal for the rotational position of the output element (141), which can be transmitted to a controller (211) of the robot (501). [11] Medical robot (501) comprising a robot arm (503, 505) according to one of the preceding claims 1 to 10.

Images