A motor drive unit for a robot or a robot joint having a braking function

Abstract

The present disclosure relates to a motor drive unit (1) for a robot, comprising a housing (2), a motor shaft element (3) rotatably mounted relative to the housing (2) about a rotation axis (A), and a brake element (4) including a ratchet (4a), the brake element (4) being connected to the housing (2), the ratchet (4a) being movable relative to the housing (2) to enable a braking function of the motor drive unit (1), the ratchet (4a) engaging an annular member (5) in a locked position of the ratchet (4a), a brake disk element (6) mounted on the motor shaft element (3), the annular member (5) being rotatable relative to the brake disk element (6), at least one set of friction surfaces being provided between the brake disk element (6) and the annular member (5) to provide a predetermined static friction or a predetermined dynamic friction, and the friction surfaces extending in a plane perpendicular to the rotation axis (A) in order to realize an improved braking function within the motor drive unit (1) for a robot joint.

Description

Technical Field

[0001] The present disclosure relates to a motor drive unit for a robot or a robot joint, comprising a housing, a motor shaft element rotatably attached to the housing about a rotation axis, and a brake element including a ratchet. The brake element is connected to the housing, and the ratchet is movable relative to the housing to enable a braking function of the motor drive, and the ratchet engages with an annular member of the motor drive unit in a locked position of the ratchet.

Background Art

[0002] Robots such as manufacturing robots usually include several robot joints driven by respective motor drive units. The motor drive unit not only realizes fast and accurate operation of the robot joint, but also features a braking function. Each braking mechanism should not only operate reliably in normal situations, but also be adapted to emergency braking.

[0003] Currently, there are two main braking technologies established for robot joints. One is a clutch-type brake, and the other is a so-called pin brake. Known clutch-type brakes are expensive, take up space, and are heavy. Therefore, they are not considered below.

[0004] The pin brake includes an electromagnetic actuator that blocks the rotation of the motor by engaging a pin with a rotating annular member of the motor. This rotating annular member is called a brake star due to its shape. Compared with the clutch-type brake, the pin brake is cheaper, lighter, smaller, and easier to install and maintain.

[0005] An exemplary pin brake is described in Patent Document 1, which describes a joint for a robot. The document discloses a pin brake that can withstand a stop in Stop Category 0 (SC0 in the case of an emergency). A stop in Stop Category 0 is characterized by quickly removing the force on the mechanical actuator, that is, it is related to an uncontrolled stop. An uncontrolled stop means stopping the mechanical operation by removing the power to the mechanical moving parts. Therefore, the pin of the electromagnetic actuator may engage with the rotating annular member of the motor drive device at full speed force. In such an emergency case SC0, usually, the pin of the pin brake cannot withstand the resulting force. This is because the rotating annular member stopped by the pin is connected to all the rotating parts of the robot joint, such as the rotor, shaft, transmission, load part, etc. Therefore, it is considered that the inertia and speed of the rotor and other rotating parts must be absorbed by the pin. This damages either the pin or the interacting rotating annular member.

[0006] In Patent Document 1, this problem is overcome by adding a slip coupling between the brake star and the remaining rotating parts, whereby the brake star can also be disconnected from the load when the pin of the brake mechanism is stopped by the pin and as a result, when the static friction of the slip coupling is overcome. However, the system described in Patent Document 1 takes up a lot of space and furthermore, does not provide a reliable and clearly defined braking force.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0008] Therefore, the problem to be solved by the present invention at present can be regarded as providing an improved braking function, particularly a braking function that enables a compact design of the motor drive unit, within the motor drive unit for a robot joint.

Means for Solving the Problem

[0009] This problem is solved by the subject matter of the invention of the independent claims. Advantageous embodiments are apparent from the dependent claims, the description text, and the figures.

[0010] One aspect relates to a motor drive unit for a robot joint, the motor drive unit including a housing, a motor shaft element, and a brake element having a ratchet. The housing may include a gear, a motor stator, a control electronic circuit, and further elements. The motor shaft element is rotatably arranged, i.e., pivotally mounted, with respect to the housing about a rotation axis. The motor shaft element may be part of a rotor. The brake element is mechanically connected to the housing, i.e., attached or fixed to the housing. The ratchet is movable back and forth linearly with respect to the housing between a locked position and a released position to enable the braking function of the motor drive unit. For this purpose, the ratchet is configured to engage within an annular member of the motor drive device in the locked position of the ratchet. In particular, the brake element may be configured for an emergency braking function, i.e., for stop category 0.

[0011] Furthermore, the motor drive unit includes a brake disk element and the aforementioned annular member. The brake disk element is attached to the motor shaft element, i.e., it is fixed or provided. The brake disk element may be part of the motor shaft element. That is, the brake disk element and the motor shaft element may be of an integrated design. Thus, in this case, the brake disk element is fixed on the motor shaft element, and they can be regarded as one part. The brake disk element and the motor shaft element not only rotate about the same axis of rotation but also preferably rotate at the same rotational speed. The annular member is rotatably attached to the brake disk element and the housing and about the same axis of rotation. As a result, the motor shaft element, the annular member, and the brake disk element can be arranged concentrically.

[0012] At least one set of friction surfaces is provided to provide a predetermined static friction and / or a predetermined dynamic friction between the brake disk element and the annular member. The said friction may also be called braking friction, which is the friction that must be adjusted / set for proper braking function. In that case, one set of friction surfaces includes two friction surfaces that face each other and, during the intended use, result in static friction and / or dynamic friction by the physical interaction of the two surfaces. Each surface may be the surface of any two adjacent elements of the motor drive unit, i.e., the surface of the brake disk element, the annular member, but also the surface of the spring element, the bearing disk element, or the friction disk element described later. In any case, the friction surfaces extend in a plane perpendicular to the axis of rotation.

[0013] The predetermined static friction is preferably selected to be small enough to prevent damage to the brake disk element or the annular member in case of an emergency stop, and the predetermined dynamic friction is preferably selected to be large enough to stop the motor fast enough for the current application. This can be achieved by appropriate selection of the material or coating of each friction surface or additional elements such as the spring element described later for increasing friction.

[0014] This results in the advantage that the friction required for stopping the motor is realized on a clearly defined surface with a large diameter. Also, the use of the brake disk element changes the direction from the radial force required for friction at the state of the art to the axial force. The axial direction of the friction, which is the braking force of the braking function, and the larger diameter enhance the effect of the frictional force for braking. Therefore, the force required for braking is smaller and can be adjusted more precisely. As a result, the design is much more flexible in terms of the dosage of the frictional force. Furthermore, the size of the friction surface can be adjusted without requiring a larger space in the axial direction. As a result, a more flexible and, moreover, smaller motor drive unit is realized.

[0015] In an advantageous embodiment, a spring element configured to push an annular member in a direction parallel to the rotation axis towards the brake disk element or a part of the brake disk element is provided in the motor drive unit. The spring element may have a ring shape and may be arranged concentrically with respect to the annular member around the rotation axis. This results in the advantage that the friction can be adjusted accurately and reliably, i.e., without a significant decrease over time. For this purpose, the spring element may be made of metal.

[0016] In another advantageous embodiment, the motor drive device includes a support disk element provided between the spring element and the annular member, preferably with the spring element attached to the brake disk element or the motor shaft element. The support disk element is preferably a low-friction support disk element. This means that the support disk element is designed to provide only minimal friction when rotating in contact with adjacent elements. This results in minimizing the friction in the spring element and / or the shaft element, leading to a reduction in tearing of the spring element and / or the shaft element. Thereby, it is ensured that the spring element maintains its spring force and thus the desired amount of friction is maintained throughout the service life of the motor drive device without the need for significant construction space.

[0017] In a further advantageous embodiment, the motor drive device includes a friction disk element provided between the annular member and the brake disk element. In particular, the annular member can be arranged axially between the support element and the friction element. The friction disk element is preferably a high-friction disk element. As a result, compared to the low-friction support disk element described above, it provides higher friction with adjacent elements. This enables higher friction to be achieved between the brake disk element and the annular member and, as a result, faster braking can be achieved with the same compact design.

[0018] Preferably, the support element and / or the friction element includes a tube portion adapted to the inner diameter of the annular member at its outer diameter in addition to a disk portion extending mainly perpendicular to the axis of rotation (flange). This provides the advantage that the respective elements can be inserted into one another and thus more accurate guidance of the various elements relative to one another can be achieved. This results in a more precisely defined behavior of the brake.

[0019] In another advantageous embodiment, the inner diameter of the friction surface that provides friction between the brake disk element and the annular member is at least 50%, preferably at least twice as large, and even more preferably at least three times as large as the diameter of the motor shaft element. The diameter of the motor shaft element can be the minimum outer diameter of the motor shaft element and / or the inner diameter of the motor shaft element. The diameter of the motor shaft element is preferably measured in the immediate vicinity of the brake disk element. This provides the advantage that the effect of the frictional force is improved and a greater braking force is provided without requiring a significantly larger axial space.

[0020] In yet another advantageous embodiment, the annular member includes, on its radially outer surface, at least one latching nose, preferably at least three latching noses, or a protrusion protruding in a direction parallel to the axis of rotation from the main extending surface of the annular member. The latching nose is configured to engage a ratchet that is only in the locked position of the ratchet. The ratchet and the latching nose may be configured such that, in the locked position, the ratchet does not extend into the main extending surface of the annular member. This provides the advantage that, if the braking force is too large, the braking force is absorbed by deforming the latching nose. Correspondingly, the latching nose can be designed to absorb the braking force, i.e., it can be designed to deform without deforming the rest of the annular member if the braking force is too large. For example, the latching nose can be designed elastically. Also, the use of latching noses allows the ratchet to be moved to an effective locked position at high rotational speeds of the motor, depending on the number of latching noses. In principle, at higher rotational speeds, the ratchet allows fewer latching noses to reach the locked position, but when the locked position is reached, it results in greater rattling. This can be overcome by latching noses that taper towards their ends, or additional latching noses extending in the direction of the axis of rotation that are fewer than the first latching noses. Next, the ratchet first engages the initial latching nose to stop the motor shaft element and then engages the additional latching nose to fix the motor shaft element in a predetermined position, thereby reducing rattling after the motor shaft element has stopped.

[0021] In a further advantageous embodiment, the motor drive unit preferably includes a magnetic and / or optical encoder target disk element made of or using a magneto-elastomer, and the encoder target disk element is applied onto the brake disk element. This provides the advantage of requiring less space as no separate encoder encoding is necessary.

[0022] In another advantageous embodiment, the ratchet is movable parallel to the axis of rotation and is automatically driven to the locked position by a passive spring mechanism, while another active mechanism holds the ratchet in the released position and the other mechanism is actuated. Thus, in the released position, the annular member can rotate freely without the ratchet engaging with it. This provides the advantage of a very simple emergency braking function when a signal and / or electricity is actually required to hold the ratchet in the released position, and the loss of signal / electricity actuates the braking mechanism automatically because when the other mechanism stops operating due to the lack of signal / electricity, the passive spring mechanism drives the ratchet to the locked position.

[0023] A further aspect relates to a robot joint or a robot comprising a motor drive unit according to any of the described embodiments.

[0024] The functions and combinations of functions described above, as well as those disclosed only in the graphical description or the figures in the general introduction section, can be used not only alone or in the described combinations, but also together with other functions or without using some of the disclosed functions, without departing from the scope of the present invention. As a result, embodiments that are not explicitly shown and not depicted in the figures but can be created by separately combining the individual functions disclosed in the figures are also part of the present invention. Therefore, embodiments and combinations of functions that do not include all the functions of the initially devised independent claims should be considered disclosed. Furthermore, embodiments and combinations of functions that are different from or extend beyond the combinations of functions described by the dependent claims of the claims should be considered disclosed.

[0025] Exemplary embodiments will be further described below with reference to schematic drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0026]

Figure 1

Figure 2

Figure 3

Best Mode for Carrying Out the Invention

[0027] In different figures, the same or functionally identical elements have the same reference numerals.

[0028] FIG. 1 shows a motor drive unit 1 for a robotic joint, comprising a housing 2, a motor shaft element 3, and a brake element 4. The housing 2 includes, in this example, a gear and a control unit not described in detail herein. The motor shaft element 3 is rotatably attached to the housing 2 about a rotation axis A. The brake element 4 includes a ratchet 4a (FIGS. 2 and 3) and is mechanically connected to the housing 2. The ratchet 4a is movable relative to the housing 2 to enable the braking function of the motor drive unit 1. For this purpose, the ratchet 4a can engage with an annular member 5 in a locked position of the ratchet 4a. Further, the motor drive unit 1 includes a brake disk element 6 fixed on the motor shaft element 3. The annular member 5 is rotatably attached to the brake disk element 6 and to the housing 2. Further, at least a pair of friction surfaces provide friction between the brake disk element 6 and the annular member 5. These friction surfaces extend in a plane perpendicular to the rotation axis A.

[0029] In this example, the brake disk element 6 is actually a sandwich brake disk element 6 comprising a first brake disk element part 6a and a second brake disk element part 6b, where additional elements are arranged between the two parts 6a and 6b in this example. This enables the pre-configuration of the brake disk element 6 including the additional elements and the installation of these elements as a single unit, i.e., simply and reliably. In an alternative design, it is considered that the function of the second brake disk element part 6b can be realized by the motor shaft element 3. For example, the motor shaft element 3 may form a support that undertakes the function of the second brake disk element part 6b of this example.

[0030] One exemplary additional element is the spring element 7, which is ring-shaped in this specification and is arranged within the motor drive unit 1, and presses the annular member 5 in a direction parallel to the rotation axis A towards the brake disk element 6, i.e., the first part 6a of the brake disk element 6. A further exemplary additional element is the bearing disk element 8 provided between the spring element 7 and the annular member 5, and the spring element 7 is attached onto the second part 6b of the brake disk element 6. The bearing disk element 8 is a low-friction bearing element in this example, and thus protects the spring element 7 when the annular member 5 is blocked, i.e., during braking.

[0031] Another exemplary additional element is the friction disk element 9 provided between the annular member 5 and the brake disk element 6, in this example the first part 6a of the brake disk element 6. Here, the annular member 5 is arranged between the bearing element 8 and the friction element 9. Since the bearing element 8 is a low-friction element and the friction disk element 9 is a high-friction element, the resulting friction between the annular member 5 and the brake disk element 6 is almost invariably determined by the friction element 9 and the force by which the spring element 7 presses the annular member 5 towards the brake disk element 6 thereby. Thus, the friction can be defined, i.e., pre-set very precisely.

[0032] In this example, the motor drive unit 1 also includes a magnetic encoder target disk element 10, which is ring-shaped and is applied on the brake disk element 6, i.e., here on the first part 6a of the brake disk element 6.

[0033] The annular member 5 includes at least one latching nose 5a, here exactly three latching noses 5a, which project from the main extension surface of the annular member 5 in a direction parallel to the rotation axis A. The latching nose 5a is configured to engage with the ratchet 4a that is only in the locked position of the ratchet 4a.

[0034] FIG. 2 shows details of the friction element 9 having a disk portion 9a that extends mainly perpendicular to the rotation axis A, and a tube portion 9b that extends mainly along the rotation axis A. The outer diameter fto of the tube portion 9b is adapted to the inner diameter ai of the annular member 5 for an accurate and reliable fit between the friction element 9 and the annular member 5. In FIG. 3, various diameters are shown in detail. Thus, the inner diameter fi of the friction surface provided by the friction element 9 and the brake disk element 6 is at least three times larger than the diameter s of the motor shaft element 3 in the vicinity of the brake disk element 6 in this example.

[0035] As a result, the friction disk element 9 and the bearing disk element 8 provide a defined bearing and a defined frictional torque between the motor shaft element 3 and the annular member 5. This results in wear and lack of life. The torque due to the spring element 7 can continue to be constant over the life of the bearing and can be considered while adjusting the braking torque of the system to a specific magnitude.

[0036] Also, the latching nose 5a can be made elastically, and as a result, large collisions that occur in the emergency braking state can be absorbed by a spring-like elastic structure that only undergoes elastic deformation, without the need to be absorbed by harder parts or elements of the motor drive unit. Thus, the energy of the emergency braking moment is at least partially absorbed by elastic deformation and can be reabsorbed when the static friction is overcome.

[0037] The operation of the braking mechanism of the illustrated motor drive unit 1 will be briefly described below.

[0038] When the brake element 4 is not braking, that is, when the ratchet 4a is held against the spring force exerted by the spring mechanism 4b and thus not engaged with the annular member 5, the annular member 5 rotates freely at the same rotational speed as the motor shaft element 3 due to the friction between the annular member 5 and the brake disc element 6.

[0039] As soon as a (very) braking state occurs, the ratchet 4a is driven forward in a direction parallel to the rotation axis A towards the annular member 5, and the ratchet engages with one of the latching noses 5a at several points. As a result, the annular member 5 immediately stops its rotation regardless of the static frictional force between the annular member 5 and the friction disc element 9. When the static frictional force is overcome, the dynamic frictional force or spring force between the stopped annular member 5 and the still-rotating brake disc element 6 decelerates the rotation of the motor shaft element 3 and thus realizes the braking function.

Explanation of reference numerals

[0040] 1 Motor drive unit 2 Housing 3 Motor shaft element 4 Brake element 4a Ratchet 4b Spring mechanism 5 Annular member 5a Latching nose 6 Brake disc element 6a First brake disc element, first part 6b Second brake disc element, second part 7 Spring element 8 Support disc element 9 Friction disc element 9a Disc portion 9b Tube portion 10 Magnetic encoder target disk element A Rotation axis ai Inner diameter of (the annular member) fi Inner diameter of (the friction surface) fto Outer diameter of (the tube part) s Diameter of (the motor shaft element) SC0 In case of emergency

Claims

1. A robot, in particular a motor drive unit (1) for a robot joint, comprising: - a housing (2); - a motor shaft element (3) rotatably mounted relative to the housing (2) about a rotation axis (A); - a brake element (4) including a ratchet (4a), the brake element (4) being connected to the housing (2), the ratchet (4a) being movable relative to the housing (2) to enable a braking function of the motor drive unit (1), the ratchet (4a) engaging an annular member (5) in a locked position of the ratchet (4a); - a brake disk element (6) attached to the motor shaft element (3); characterized in that: - the annular member (5) is rotatable relative to the brake disk element (6); - at least one set of friction surfaces is provided between the brake disk element (6) and the annular member (5) to provide a predetermined static friction or a predetermined dynamic friction, the friction surfaces extending in a plane perpendicular to the rotation axis (A). A motor drive unit (1).

2. The motor drive unit (1) according to claim 1, further comprising a spring element (7) configured to push the annular member (5) in a direction parallel to the rotation axis (A) towards at least a part (6a) of the brake disk element (6). The motor drive unit (1) according to claim 1.

3. The motor drive unit (1) according to claim 2, further comprising a support disk element (8) provided between the spring element (7) and the annular member (5). The motor drive unit (1) according to claim 2.

4. The motor drive unit (1) according to any one of claims 1 to 3, further comprising a friction disk element (9) provided between the annular member (5) and the brake disk element (6), in particular the annular member (5) being arranged between the support disk element (8) and the friction disk element (9). The motor drive unit (1) according to any one of claims 1 to 3.

5. The motor drive unit (1) according to claim 3 or 4, wherein the support disk element (8) and / or the friction disk element (9) includes a tube portion (9b) adapted to an inner diameter (ai) of the annular member (5) at its outer diameter (fto) in addition to a disk portion (9a) extending mainly perpendicular to the rotation axis (A). The motor drive unit (1) according to claim 3 or 4.

6. The inner diameter (fi) of the friction surface is at least 50% larger, preferably at least twice as large, than the diameter of the motor shaft element (3), resulting in friction between the brake disk element (6) and the annular member (5). The motor drive unit (1) according to any one of claims 1 to 5.

7. The annular member (5) includes at least one latching nose (5a), preferably at least three latching noses (5a), protruding from its outer surface in the direction parallel to the rotation axis (A) from the main extension plane of the annular member (5). The latching nose (5a) is configured to engage with the latch (4a) only in the locked position of the latch (4a). The motor drive unit (1) according to any one of claims 1 to 6.

8. Characterized by comprising a magnetic and / or optical encoder target disk element (10), preferably made of or using a magneto-elastomer, applied on the brake disk element (6). The motor drive unit (1) according to any one of claims 1 to 7.

9. The latch (4a) is movable parallel to the rotation axis (A) and is driven to the locked position by a spring mechanism (4b). When another mechanism is actuated, the other mechanism holds the latch (4a) in the released position. The motor drive unit (1) according to any one of claims 1 to 8.

10. A robot joint or a robot, particularly a mobile robot, comprising the motor drive unit (1) according to any one of claims 1 to 9.

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