Motor driving device with braking function for robot or robot joint

Abstract

The present disclosure relates to a motor drive (1) for a robot, comprising a housing (2); comprising a motor shaft element (3) which is rotatably mounted about an axis of rotation (A) relative to a housing (2); comprising a braking element (4) comprising a ratchet wheel (4a), where the braking element (4) is connected to the housing (2) and the ratchet wheel (4a) is movable relative to the housing (2) to activate a braking function of the motor drive (1), where the ratchet wheel (4a) engages an annular member (5) in a locked position of the ratchet wheel (4a); comprising a brake disc element (6) attached to a motor shaft element (3); wherein the annular member (5) is rotatable relative to the brake disc element (6), and at least one set of friction surfaces is provided to provide a given static friction or a given dynamic friction between the brake disc element (6) and the annular member (5), and wherein the friction surfaces extend in a plane perpendicular to the axis of rotation (A), to provide an improved braking function in a motor drive (1) for a robot joint.

Description

Technical Field

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

[0002] Robots, such as manufacturing robots, usually include multiple robot joints that are driven by respective motor drives. The motor drives not only provide fast and precise drive to the robot joints, but also have a braking function. The corresponding braking mechanism needs to work reliably not only in normal situations, but also needs to be suitable for emergency braking.

[0003] At present, there are two main types of braking technologies for robot joints. One is a clutch brake and the other is a so-called pin brake. Known clutch brakes are expensive, take up a lot of space, and are heavy, so they will not be considered below.

[0004] The pin-type brake includes an electromagnetic drive that stops the rotation of the motor by engaging a pin with a rotating annular member of the motor. Depending on the shape of the rotating annular member, the rotating annular member may also be called a brake star. Compared to clutch-type brakes, pin-type brakes are cheaper, lighter, smaller, and easier to install and maintain.

[0005] An exemplary pin brake is described in EP 3 045 273 B1, which describes a robot joint. The document discloses a pin brake capable of withstanding a zero-stage stop (emergency SCO). A zero-stage stop is characterized by the immediate disconnection of the power supply to the machine drive, that is, it involves an uncontrolled stop. An uncontrolled stop means stopping the machine operation by disconnecting the power supply to the machine starter. As a result, the pin of the electromagnetic drive may engage with the rotating annular member of the motor drive at full speed. In such an emergency SCO, the pin of the pin brake is generally unable to withstand the forces generated by the emergency SCO. This is because the rotating annular member to be stopped by the pin is connected to all rotating parts of the robot joint, such as the rotor, shaft, gearbox, load, etc. Therefore, the inertia and speed of the rotor and other rotating parts must be absorbed by the pin. This can damage the pin or the interacting rotating annular member.

[0006] In EP 3 045 273 B1, this problem is overcome by adding a sliding coupling between the brake star and the remaining rotating parts, which allows the pin of the brake mechanism to be disengaged from the load once the static friction of the sliding coupling has been overcome when the brake star is stopped by the pin. However, the system described in EP 3 045 273 B1 is very space-consuming and, moreover, does not generate a reliable, well-defined braking force.

[0007] Therefore, the problem to be solved by the present disclosure can be seen as providing an improved braking function in a motor drive of a robot joint, in particular a braking function that allows a compact design of the motor drive. Summary of the invention

[0008] The above problems can be solved by the content of the independent claims. Preferred embodiments are evident from the dependent claims, the description and the drawings.

[0009] On the one hand, a motor drive device for a robot joint is provided, which includes a housing, a motor shaft element and a brake element with a ratchet. The housing may include gears, a motor stator, control electronics and other components. The motor shaft element is rotatably mounted about a rotation axis relative to the housing, i.e., pivotally mounted. The motor shaft element may be part of a rotor. The brake element is mechanically connected to the housing, i.e., the brake element is attached or fixed to the housing. The ratchet can move back and forth in a linear direction between a locked position and a released position relative to the housing to enable the braking function of the motor drive device. To this end, the ratchet is configured to engage an annular member of the motor drive device in the locked position of the ratchet. Specifically, the brake element can be configured for an emergency braking function, i.e., for a zero-level stop.

[0010] In addition, the motor drive device includes a brake disc element and the above-mentioned annular member. The brake disc element is attached to the motor shaft element, i.e. fixed or mounted to the motor shaft element. The brake disc element can also be a part of the motor shaft element, i.e. the brake disc element and the motor shaft element can be of one-piece design. Therefore, in this case, the brake disc element can also be regarded as being fixed to the motor shaft element because they are one-piece. Preferably, the brake disc element and the motor shaft element not only rotate around the same rotation axis, but also rotate at the same speed. The annular member is rotatably mounted relative to the brake disc element and the housing, and rotates around the same rotation axis. Therefore, the motor shaft element, the annular member and the brake disc element can be coaxially arranged.

[0011] At least one set of friction surfaces is provided in order to provide a given static friction and / or a given dynamic friction between the brake disc element and the annular member. The friction may be referred to as braking friction, which is the friction that must be adjusted / set to achieve a proper braking function. A set of friction surfaces comprises two friction surfaces facing each other and providing static and / or dynamic friction by the physical interaction of the two surfaces during the intended use. The corresponding surfaces may be the surfaces of any two adjacent elements of the motor drive, for example, the surfaces of the brake disc element, the annular member, and the surfaces of the elastic element, the bearing disc element or the friction disc element mentioned below. In any case, the friction surfaces extend in a plane perpendicular to the axis of rotation.

[0012] Preferably, the given static friction is selected to be small enough to prevent damage to the brake disc element or the annular member in the event of an emergency stop, and the given dynamic friction is selected to be large enough to stop the motor quickly enough for the current application. This can be achieved by selecting appropriate materials or coatings of the respective friction surfaces, or additional elements such as the elastic elements mentioned below, to increase the friction.

[0013] This has the advantage that the friction force required to stop the motor is achieved on a well-defined surface with a large diameter. The use of a brake disc element also changes the direction from the radial force required for friction in the prior art to an axial force. The axial direction of the friction, i.e. the braking force of the friction force of the braking function, and the larger diameter lead to an increased leverage effect of the braking friction force. As a result, the force required for braking is smaller and can be adjusted more precisely. As a result, a more flexible design can also be made with regard to the magnitude of the friction force. In addition, the size of the friction surface can be adjusted without taking up more space in the axial direction. As a result, a more flexible but more compact motor drive can be achieved.

[0014] As a preferred embodiment, the motor drive comprises an elastic element, which is configured to press the annular member towards the brake disc element or a part of the brake disc element in a direction parallel to the rotation axis. The elastic element can be annular in shape and can be arranged coaxially with the annular member around the rotation axis. This has the advantage that the friction force can be adjusted accurately and reliably, that is, the friction force does not decrease significantly over time. For this purpose, the elastic element can be made of metal.

[0015] As another preferred embodiment, the motor drive comprises a bearing disc element between the elastic element and the annular member, preferably the elastic element is mounted on the brake disc element or the motor shaft element. Preferably, the bearing disc element is a low-friction bearing disc element. This means that the bearing disc element is designed to provide only minimal friction when rotating relative to an adjacent element. This has the advantage that the friction at the elastic element and / or the shaft element is minimized, thereby reducing the tearing of the elastic element and / or the shaft element. This ensures that the elastic element maintains its elastic force, thereby ensuring that the expected amount of friction is maintained throughout the service life of the motor drive without requiring significant structural space.

[0016] As a further preferred embodiment, the motor drive comprises a friction disc element arranged between the annular member and the brake disc element. In particular, the annular member can be arranged axially between the bearing element and the friction element. Preferably, the friction disc element is a high-friction disc element. Therefore, it has a higher friction force with adjacent elements than the above-mentioned low-friction bearing disc element. This has the advantage that a higher friction force between the brake disc element and the annular member can be achieved, so that faster braking can be achieved in the same compact design.

[0017] Preferably, the bearing element and / or the friction element comprises, in addition to a disk-shaped part (flange) extending mainly perpendicularly to the axis of rotation, a tubular part, the outer diameter of which is adapted to the inner diameter of the annular member. This has the advantage that the individual elements can be inserted into one another, thereby providing a more precise guidance of the different elements relative to one another. This makes the performance of the brake element more precise and more defined.

[0018] As another preferred embodiment, the inner diameter of the friction surface providing the friction between the brake disc element and the annular member is at least 50% larger than the diameter of the motor shaft element, preferably at least twice as large, even more preferably at least three times as large. The diameter of the motor shaft element may be the smallest outer diameter of the motor shaft element and / or the inner diameter of the motor shaft element. Preferably, the diameter of the motor shaft element is measured in the direct vicinity of the brake disc element. This brings the advantage that the leverage of the friction force is improved, resulting in a greater braking force without taking up more space in the axial direction.

[0019] As another preferred embodiment, the annular member includes at least one latch nose, preferably at least three latch noses or lugs, on its radial outer surface, which protrude from the main extension plane of the annular member in a direction parallel to the rotation axis. The latch nose is configured to engage with the ratchet only in the locked position of the ratchet. The ratchet and the latch nose can be configured in the locked position so that the ratchet does not extend into the main extension plane of the annular member. The advantage brought by this is that if the braking force is too large, the braking force can be absorbed by deforming the latch nose. Accordingly, the latch nose can be designed to absorb the braking force, that is, it is designed to deform when the braking force is too large, so that the rest of the annular member is not deformed. For example, the latch nose can be designed to be elastic. According to the number of latch noses, the use of the latch nose can also move the ratchet to an effective locking position when the motor rotates at a high speed. In principle, fewer latch noses can make the ratchet reach the locked position at a higher speed, but once the locked position is reached, a larger gap will result. This problem can be overcome by a latching nose which tapers toward its end, or an additional latching nose which extends less than the original latching nose in the direction of the rotation axis. The ratchet will then first engage with the original latching nose to stop the motor shaft element, and engage with the additional latching nose to fix the motor shaft element in a given position with reduced play after the motor shaft element has stopped.

[0020] As a further preferred embodiment, the motor drive comprises a magnetic and / or optical encoder target disc element, preferably made of or made of a magnetic elastomer, which is applied to the brake disc element. Since a separate encoder ring is not required, it has the advantage of requiring less space.

[0021] As a further preferred embodiment, the ratchet can be moved parallel to the axis of rotation and is automatically driven to the locked position by a passive elastic mechanism, and when another mechanism is activated, the activated mechanism holds the ratchet in the released position. Thus, in the released position, the annular member can rotate freely without the ratchet engaging with it. The advantage of this is that the emergency brake function is very simple, in which a signal and / or power is actually required to hold the ratchet in the released position, since the passive elastic mechanism will drive the ratchet to the locked position when the other mechanism is deactivated due to lack of signal / power, so the lack of signal and / or power automatically activates the brake mechanism.

[0022] Further aspects relate to a robot joint or a robot having a motor drive according to one of the described embodiments.

[0023] The above-mentioned features and feature combinations, including the features and feature combinations described in the introduction, as well as the features and feature combinations described in the drawings or disclosed separately in the drawings, can be used not only alone or in the described combination, but also together with other features without departing from the scope of the invention, or without using certain disclosed features. Therefore, embodiments that are not explicitly shown and described in the drawings but can be produced by combining the individual features disclosed in the drawings separately are also part of the present invention. Therefore, if an embodiment has certain features or combinations of features that are not included in the original independent claim, then these embodiments should also be deemed to have been disclosed. In addition, if certain embodiments have features that are different from or exceed the feature combinations described in the dependent claims, then these embodiments should also be deemed to have been disclosed. DETAILED DESCRIPTION

[0024] The exemplary embodiments will be further described below by means of schematic diagrams.

[0025] Figure 1 An exploded view of an exemplary embodiment of a motor drive for a robotic joint is shown;

[0026] Figure 2 Shows Figure 1 a side view of the exemplary embodiment shown; and

[0027] Figure 3 A cross-sectional view of the exemplary embodiment is shown.

[0028] In different figures, identical elements or elements having the same function are provided with the same reference symbols.

[0029] Figure 1 The motor drive device 1 for a robot joint is shown, comprising a housing 2, a motor shaft element 3 and a brake element 4. In this example, the housing 2 comprises a gear and a control unit (not described in detail herein). The motor shaft element 3 is rotatably mounted about a rotation axis A and is rotatable relative to the housing 2. The brake element 4 comprises a ratchet 4a ( Figure 2 , 3 ), and is mechanically connected to the housing 2. The ratchet 4a is movable relative to the housing 2 in order to implement a braking function of the motor drive 1. To this end, the ratchet 4a can engage the annular member 5 in a locked position of the ratchet 4a. In addition, the motor drive 1 comprises a brake disc element 6, which is fixed to the motor shaft element 3. The annular member 5 is rotatably mounted relative to the brake disc element 6 and relative to the housing 2. In addition, at least one set of friction surfaces provides friction between the brake disc element 6 and the annular member 5. These friction surfaces extend in a plane perpendicular to the rotation axis A.

[0030] In the present embodiment, the brake disc element 6 is actually a sandwich brake disc element 6, having a first brake disc element part 6a and a second brake disc element part 6b, wherein in the present embodiment, the additional element is arranged between the two parts 6a, 6b. In this way, the brake disc element 6 including the additional element can be pre-configured and these elements can be installed as a whole, i.e. simply and reliably. In another design, the function of the second brake disc element part 6b can be provided by the motor shaft element 3. For example, the motor shaft element 3 can form a bracket, which assumes the function of the second brake disc element part 6b in the present embodiment.

[0031] One of the exemplary additional elements may be an elastic element 7, which is annular here and is arranged in the motor drive 1 to press the annular member 5 toward the brake disc element 6, i.e. the first part 6a of the brake disc element 6, in a direction parallel to the rotation axis A. Another exemplary additional element is a bearing disc element 8 located between the elastic element 7 and the annular member 5, wherein the elastic element 7 is mounted on the second part 6b of the brake disc element 6. The bearing disc element 8 is a low-friction bearing element in this example, so that in the case where the annular member 5 is blocked, i.e. in the case of braking, the bearing disc element 8 can protect the elastic element 7.

[0032] Another exemplary additional element is a friction disc element 9 arranged between the annular member 5 and the brake disc element 6 (in this example, the first part 6a of the brake disc element 6). Here, the annular member 5 is arranged between the bearing disc element 8 and the friction disc element 9. Since the bearing disc element 8 is a low-friction element and the friction disc element 9 is a high-friction element, the friction generated between the annular member 5 and the brake disc element 6 is almost completely determined by the force of the friction disc element 9 and the elastic element 7 pressing the annular member 5 toward the brake disc element 6. Therefore, the friction can be defined very accurately, i.e. the preset friction.

[0033] In this embodiment, the motor drive unit 1 further comprises a magnetic encoder target disk element 10 , which is annular and attached to the brake disk element 6 , that is, attached to the first component 6 a of the brake disk element 6 .

[0034] The annular member 5 comprises at least one latching nose 5a, here specifically three latching noses 5a, which project from a main extension plane of the annular member 5 in a direction parallel to the rotation axis A. The latching noses 5a are configured to mesh with the ratchet 4a only in its locked position.

[0035] Figure 2Details of the friction disc element 9 are shown, the disc-shaped part 9a of the friction disc element 9 mainly extends perpendicularly to the rotation axis A, and the tubular part 9b of the friction disc element 9 mainly extends along the rotation axis A. The outer diameter fto of the tubular part 9b is adapted to the inner diameter ai of the annular member 5, so that the friction disc element 9 and the annular member 5 are accurately and reliably matched. Figure 3 The different diameters are shown in more detail. Thus, in the present example, the inner diameter fi of the friction surface provided by the friction disc element 9 and the brake disc element 6 is at least three times larger than the diameter s of the motor shaft element 3 in the vicinity of the brake disc element 6 .

[0036] The friction disk element 9 and the bearing disk element 8 thus provide a defined bearing and a defined friction torque between the motor shaft element 3 and the annular component 5. No wear will occur and the service life can be extended. Due to the presence of the elastic element 7, the torque will remain constant over the service life of the bearing and can be taken into account when determining the braking torque of the system.

[0037] The latch nose 5a can also be made elastic, so that the large impact occurring in the emergency braking situation can be absorbed by the spring-like elastic structure, which is only affected by the elastic deformation and does not have to be absorbed by the harder parts or components of the motor drive. Therefore, the energy of the emergency braking torque can be at least partially absorbed by the elastic deformation and reabsorbed when overcoming the static friction.

[0038] The following briefly describes the working principle of the brake mechanism of the motor drive device 1:

[0039] When the brake element 4 is not braked, that is, the ratchet 4a overcomes the elastic force provided by the elastic mechanism 4b and is blocked, and thus is not engaged with the annular component 5, due to the friction between the annular component 5 and the brake disc element 6, the annular component 5 rotates freely at the same speed as the motor shaft element 3.

[0040] When a (emergency) braking situation occurs and the ratchet 4a is driven forward to the ring member 5 in a direction parallel to the rotation axis A, it engages with one of the latch noses 5a at a certain point. As a result, the ring member 5 stops rotating immediately despite the static friction between the ring member 5 and the friction disc element 9. Once the static friction is overcome, the dynamic friction or sliding force between the stopped ring member 5 and the still rotating brake disc element 6 slows down the rotation of the motor shaft element 3, thus achieving a braking function.

Claims

1. A motor drive device (1) for a robot, in particular for a robot joint, comprising: - a housing (2); - a motor shaft element (3), the motor shaft element (3) being rotatably mounted relative to the housing (2) about a rotation axis (A); - a brake element (4), said brake element (4) comprising a ratchet (4a), wherein: The brake element (4) is connected to the housing (2), and the ratchet (4a) is movable relative to the housing (2) to enable a braking function of the motor drive (1), wherein the ratchet (4a) engages an annular member (5) in a locked position of the ratchet (4a); It is characterized in that - a brake disc element (6) which is attached to the motor shaft element (3); and, - the annular member (5) is rotatable relative to the brake disc element (6); and - providing at least one set of friction surfaces to provide a given static friction or a given dynamic friction between the brake disc element (6) and the annular member (5), wherein the friction surfaces extend in a plane perpendicular to the rotation axis (A).

2. The motor drive (1) according to the preceding claim, It is characterized in that The elastic element (7) is configured to press the annular member (5) toward at least a portion (6a) of the brake disc element (6) in a direction parallel to the rotation axis (A).

3. The motor drive (1) according to the preceding claim, It is characterized in that A bearing disk element (8) is arranged between the elastic element (7) and the annular member (5).

4. The motor drive (1) according to claim 1, It is characterized in that A friction disk element (9) is arranged between the annular component (5) and the brake disk element (6). Specifically, the annular component (5) is arranged between the bearing disk element (8) and the friction disk element (9).

5. The motor drive (1) according to one of the two preceding claims, It is characterized in that The bearing disk element (8) and / or the friction disk element (9) comprises, in addition to a disk-shaped component (9a) extending mainly perpendicularly to the rotation axis (A), a tubular component (9b), the outer diameter (fto) of which is adapted to the inner diameter (ai) of the annular member (5).

6. The motor drive (1) according to claim 1, It is characterized in that The inner diameter (fi) of the friction surface providing friction between the brake disc element (6) and the annular member (5) is at least 50% larger than the diameter (s) of the motor shaft element (3), preferably at least twice larger.

7. The motor drive (1) according to claim 1, It is characterized in that The annular member (5) includes at least one latch nose (5a) on its outer surface, and preferably includes at least three latch noses (5a), which protrude from the main extension plane of the annular member (5) in a direction parallel to the rotation axis (A), wherein the latch nose (5a) is configured to engage with the ratchet (4a) only in the locked position of the ratchet (4a).

8. The motor drive (1) according to claim 1, It is characterized in that The magnetic and / or optical encoder target disc element (10) applied to the brake disc element (6) is preferably manufactured using or made of a magnetic elastomer.

9. The electric motor drive (1) according to claim 1, It is characterized in that The ratchet (4a) can be moved parallel to the rotation axis (A) and is driven to the locking position by an elastic mechanism (4b), and when another mechanism is activated, the other mechanism holds the ratchet (4a) in the release position.

10. A robot joint or a robot, in particular a mobile robot, having a motor drive (1) according to one of the preceding claims.

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