Rotatably mounted element, system with a rotatably mounted element and a power source, and method for variably coupling a hub to a shaft

Abstract

Rotatably mounted element (1000; 2000) comprising a shaft (100; 200) with a shaft body (10); a hub (300), wherein the shaft (100; 200) is at least partially enclosed by the hub (300); at least one groove (12a; 12b), wherein the at least one groove is arranged in the shaft body (10); at least one brake shoe (14a; 14b), wherein the at least one brake shoe (14a; 14b) is arranged at least partially in the at least one groove (12a; 12b); and a tension element (16), wherein the tension element (16) is coupled to the at least one brake shoe (14a; 14b), wherein the tension element (16) is at least partially made of a shape memory material, wherein the tension element (16) is designed to act on the at least one brake shoe (14a; 14b) with a first greater tensile force in a first state of the shape memory material, so that the at least one brake shoe is held completely in the at least one groove, and wherein the tension element (16) is designed to act on the at least one brake shoe (14a; 14b) with a second, lower tensile force in a second state of the shape memory material.

Description

[0001] The invention relates to a rotatably mounted element having a shaft and a hub, a system having a rotatably mounted element and a power source, and a method for variably coupling a hub to a shaft.

[0002] To hold a rotatably mounted element in position, either a positive or a frictional connection can be used. The major disadvantage of a positive connection, for example, due to a detent, is that it requires incrementation, meaning a holding function can only be implemented in defined positions. Holding a position using frictional connection often requires large forces and an additional actuator to apply them. Such a setup often requires too much space and is therefore usually not feasible, especially with compact adjustment units.

[0003] The use of shape memory alloys is known from the prior art, for example to compensate for play in drum brakes (DE 31 00 678 A1) or to exert a braking force on a rotating axle (DE 197 44 356 C1, JP H02-310 856 A, JP S63-130 935 A, US 8,087,498 B2). In the latter case, a change in the expansion of the shape memory alloy is used to press a braking element against a rotating axle from the outside when the shape memory alloy is at a greater extent, thus decelerating the rotating axle. When the shape memory alloy is at a lesser extent, the braking element is released from the axle, thus allowing it to rotate. DE 10 2006 019 350 B3 shows a braking and / or clamping device for shafts with a clamping ring. US 4,823,035 A shows an electric motor with a locking device comprising a shape memory alloy.

[0004] There is a need to provide a concept for a variable coupling of a shaft with a hub that allows a continuous change of the coupling.

[0005] This need is met by the rotatably mounted element, the system comprising the rotatably mounted element and the power source, and the method for variably coupling a hub to a shaft.

[0006] This problem is solved by a shape memory alloy-actuated element. The invention is based on the idea of ​​establishing the coupling between shaft and hub through a frictional connection. This connection is based on the fact that brake shoes, which are arranged in grooves in a shaft body of the shaft or in the hub, are retracted into the grooves when a change in the position of the hub relative to the shaft is to be made. For this purpose, the brake shoes are coupled to a tension element made of a shape memory material. The shape memory material can assume two states: a first in which the tension element exerts a greater tensile force on the brake shoes, so that they are held completely in the grooves and a frictional connection between shaft and hub is canceled, and a second in which the tension element exerts a lower tensile force on the brake shoes, so that they couple the shaft to the hub in a frictional connection.For this purpose, the brake shoes can be integrated into grooves in the shaft and pressed against the hub by a spring, thereby "holding" the shaft in place. If the shaft needs to be rotated or repositioned, the tension element made of shape memory material (such as a shape memory alloy (SMA) wire connected to the two brake shoes) is energized, causing it to heat up and contract. The reduction in length pulls the brake shoes back into the grooves and the shaft is "released" or can rotate. As soon as the positioning is successful, the SMA wire is no longer activated, causing it to return to its original length. The brake shoes once again press against the hub or shaft via the spring, fixing the shaft in the set position. The effect can also be reversed, so that the brake element holds the shaft in the activated state and releases it in the deactivated state.

[0007] Embodiments provide a rotatably mounted element having a shaft with a shaft body and with a hub. The shaft is at least partially enclosed by the hub. The rotatably mounted element further comprises at least one groove arranged in the shaft body. The rotatably mounted element further comprises a brake shoe, which is at least partially arranged in the at least one groove, and a tension element, which is coupled to the at least one brake shoe. The tension element is at least partially made of a shape memory material. The tension element is designed to act on the at least one brake shoe with a first, greater tensile force in a first state of the shape memory material, such that the at least one brake shoe is held completely in the at least one groove.The tension element is designed to act on the at least one brake shoe with a second, lower tensile force in a second state of the shape memory material. Thus, in the first state of the shape memory material, the brake shoes disappear completely into the groove. If the brake shoes are used to couple the shaft to a hub, a frictional connection between the brake shoes and the hub or shaft is eliminated in the first state. The shaft can thus be continuously repositioned relative to the hub.

[0008] The rotatably mounted element can, for example, comprise at least one spring coupled to the at least one brake shoe. The at least one spring can be configured to exert a force on the at least one brake shoe, such that at least a portion of the at least one brake shoe protrudes from the at least one groove if the shape memory material is in the second state. If a portion of the at least one brake shoe protrudes from the at least one groove, this portion can be used to provide a frictional connection between the shaft and a hub.

[0009] In a preferred embodiment, the spring can correspond to the tension element. This is shown, for example, in the Fig. 2a and Fig. 2b. This allows for a simplified design of the shaft or hub.

[0010] Alternatively, the at least one spring can be implemented in addition to the tension element. This allows for greater freedom in the selection of materials and element sizes for the tension element and the spring.

[0011] In embodiments according to the invention, the at least one groove is arranged in the shaft body. The tension element can be designed such that the at least one brake shoe exerts a force on the hub if the shape memory material is in the second state, so that the shaft and the hub are frictionally coupled in the second state of the shape memory material. The integration of the groove into the shaft body enables a compact design of the rotatably mounted element.

[0012] In some embodiments, the rotatably mounted element further comprises an interface for a power source, wherein the interface is coupled to the tension element. The interface can be configured to provide a current flow from a power source to the tension element, so that the tension element contracts in the first state of the shape memory material. The power source can be used, for example, to heat the tension element through the current flow and thereby activate the first state or the second state of the shape memory material.

[0013] Embodiments provide a system comprising such a rotatably mounted element and the power source. The power source is configured to provide the current flow for the tension element via the interface.

[0014] For example, the shape memory material can have the first state in a first time interval and the second state in a second time interval. The current source can be designed to provide the current flow for the tension element in the first time interval. If the current flow is required to transform the shape memory material into the first state, power consumption can be reduced with only occasional repositioning of the shaft relative to the hub. Alternatively, the current source can be designed to provide the current flow for the tension element in the second time interval. The tension element can thus be designed such that it assumes the second state when a current flow is provided and such that it assumes the first state when no current flow is provided.For example, a frictional connection between the shaft and the hub can be deactivated in a power-off state, enabling applications that require a "normally open" state in the event of a power failure or shutdown.

[0015] Embodiments further provide a method for variably coupling a hub to a shaft of a rotatably mounted element. The shaft is at least partially enclosed by the hub. The shaft comprises a shaft body. At least one groove of the rotatably mounted element is arranged in the shaft body. The rotatably mounted element further comprises at least one brake shoe, which is at least partially arranged in the at least one groove, and a tension element. The tension element is coupled to the at least one brake shoe and is at least partially made of a shape memory material. The method comprises transforming the shape memory material of the tension element into a first state, such that the tension element acts on the at least one brake shoe with a first, greater tensile force and the at least one brake shoe is held completely in the groove.The method further comprises, after or during the transformation of the shape memory material of the tension element into the first state, changing a position of the hub relative to the shaft while the at least one brake shoe is fully held in the at least one groove. The method further comprises, after changing the position of the hub relative to the shaft, transforming the shape memory material of the tension element into a second state such that the tension element acts on the at least one brake shoe with a second, lower tensile force and the at least one brake shoe exerts a force on the hub, such that the shaft and the hub are force-locked. This enables a variable force-locked coupling of the hub to the shaft.

[0016] They show: Fig. 1a shows an embodiment of a rotatably mounted element with a shaft and a hub, wherein a tension element of the shaft and a spring of the shaft are designed separately; Fig. 1b shows an embodiment of a system comprising a rotatably mounted element with a shaft and a hub and with a power source, wherein a tension element of the shaft and a spring of the shaft are designed separately; Fig. 2a and Fig. 2b shows a further embodiment of a rotatably mounted element with a shaft and a hub, wherein a tension element of the shaft is formed by a spring; Fig. 3 shows an embodiment of a rotatably mounted element with a shaft and a hub, wherein a groove in which a brake shoe is arranged is arranged in the hub; and Fig. 4 an embodiment of a method for variably coupling a hub to a shaft.

[0017] Fig. 1a shows a sectional view of an embodiment of a rotatably mounted element 1000 with a shaft 100 and a hub 300. The shaft 100 comprises a shaft body 10 with at least one groove. The rotatably mounted element further comprises at least one brake shoe, which is at least partially arranged in the at least one groove. Fig. The shaft shown in Figure 1a has two grooves 12a and 12b arranged on radially opposite sides of the shaft. Two brake shoes 14a; 14b are arranged in the grooves 12a; 12b. The rotatably mounted element further comprises a tension element 16 made at least partially from a shape memory material. The tension element 16 is coupled to the brake shoes 14a; 14b. The tension element 16 is designed to exert a tensile force, i.e., a force directed from the brake shoes in the direction of the tension element 16, on the brake shoes 14a; 14b. The tension element 16 is designed to act on the brake shoes 14a; 14b with a first, greater tensile force in a first state of the shape memory material, so that the brake shoes are fully held in the grooves (i.e., are fully arranged in the grooves). The tension element 16 is designed to act on the brake shoes 14a; 14b with a second, lower tensile force in a second state of the shape memory material.If the tension element 16 acts with the second, lower tensile force on the brake shoes 14a; 14b, at least a part of the brake shoes can protrude from the grooves.

[0018] For this purpose, the rotatably mounted element, such as the shaft, can be Fig. 1a, at least one spring 18. The spring is coupled to the brake shoes 14a; 14b. The spring is designed to exert a force on the brake shoes 14a; 14b, so that at least a portion of the brake shoes protrudes from the grooves if the shape memory material has the second state. In this case, the spring can, as shown in Fig. 1a and Fig. 1b as spring 18, in addition to the tension element 16. Alternatively, the spring can be designed as in the Fig. 2a and Fig. 2b, correspond to the tension element 16. If, as shown in Fig. 1a and Fig. 1b, the spring and the tension element 16 are designed as separate components, the spring 18 can be dimensioned such that the force exerted by the spring on the brake shoes 14a; 14b is greater than the second, smaller tensile force of the tension element and smaller than the first, larger tensile force of the tension element. This results in the brake shoes being held completely in the grooves (i.e., not exceeding a radius of the shaft body) if the shape memory material has the first state, and in at least a portion of the brake shoes protruding from the grooves if the shape memory material has the second state. If the hub 300 now encloses the shaft 100 at the location on the shaft body where the grooves and the brake shoes are arranged, the position of the hub 300 relative to the shaft can be changed if the shape memory material has the first state (and consequently the brake shoes are arranged completely in the grooves).If the shape memory material is in the second state, the force exerted by the spring 18 on the brake shoes predominates, and the brake shoes are pressed against the hub 300, so that the hub 300 (via the brake shoes 14a; 14b) is frictionally coupled to the shaft 100. The brake shoes can, for example, be friction elements, i.e., elements that have a higher coefficient of friction than a material of the shaft body. The tension element 16 of the rotatably mounted element is designed such that the at least one brake shoe 14a; 14b exerts a force on the hub 300 if the shape memory material is in the second state, so that the shaft 100 and the hub 300 are frictionally coupled in the second state of the shape memory material.

[0019] The tension element 16 is at least partially made of a shape memory material. In other words, at least a portion of the tension element 16 can consist of the shape memory material or comprise the shape memory material. For example, the tension element can comprise two coupling elements that are mechanically coupled to the brake shoes 14a; 14b, and an element of variable length that consists of shape memory material or comprises shape memory material. Shape memory materials (also known as shape memory alloys) are materials that can exist in two different crystal structures. Shape memory materials are characterized by their ability to "remember" a previous shape despite subsequent deformation, meaning they can reassume the previous shape upon actuation. This actuation can be based, for example, on heating the shape memory material or on a magnetic field.

[0020] In order for the shape memory material to assume the first state or the second state, it can be influenced by an external entity. In many cases, the shape memory material is a temperature-dependent shape memory material. In at least some embodiments, the shape memory material of the tension element is designed for a two-way shape memory effect, i.e. the shape memory material of the tension element can be designed for a first shape (which is linked, for example, to a first temperature threshold) and a second shape (which is linked, for example, to a second temperature threshold). The first shape can correspond approximately to the first state of the shape memory material and the second shape can correspond to the second state of the shape memory material. The first shape can have a greater extent than the second shape.For example, the shape memory material can assume the first state or the first shape (e.g., be transformed into the first state) if a temperature of the shape memory material exceeds the first temperature threshold, and assume the second state or the second shape if the temperature of the shape memory material falls below the second temperature threshold (or vice versa). This can be achieved, for example, by a current flow through at least the part of the tension element that comprises the shape memory material. The current flow can cause at least the part of the tension element that comprises the shape memory material to act as a heating resistor, so that the shape memory material is heated such that the temperature of the shape memory material exceeds or falls below the first or second temperature threshold, and the shape memory material assumes the first state or the second state.

[0021] This current flow may be caused by a current source 24. In at least some embodiments, the rotatably mounted element, as shown in Fig. 1b, an interface 22 for a power source 24 is shown, which is coupled to the tension element 16, for example, ohmically electrically connected. For example, the power source with the interface can be arranged entirely in the shaft or the hub. For example, the power source can comprise an energy source, such as a battery, which is arranged in the shaft or hub. Alternatively, the interface can be provided for connection to an external energy source / power source. For example, the rotatably mounted element, such as the shaft or the hub, can comprise an interface 22 to an external power source 24, which functions as the power source of the rotatably mounted element. Embodiments further provide a system comprising the rotatably mounted element and the power source 24, wherein the power source 24 is designed to provide the current flow for the tension element 16 via the interface 22.If the power source is an external power source, the interface for the power source can be, for example, an inductive interface or a wired interface. For example, the interface can comprise one or more induction coils and / or one or more sliding contacts arranged along the shaft. If the shaft's rotational angle is limited, for example, to ± 45°, the interface can be a wired interface for a flexible cable.

[0022] For example, the current source 24 can comprise a control mechanism configured to control the current flow of the current source. The control mechanism can be configured to set or transform the shape memory material into the first state or into the second state by controlling the current flow. For example, the shape memory material can have the first state in a first time interval and the second state in a second time interval. The current source, such as the control mechanism of the current source, can be configured to provide the current flow for the tension element 16 in the first time interval, such as to heat the shape memory material in the second time interval through the current flow. Thus, in this exemplary embodiment, the first temperature threshold can be higher than the second temperature threshold.The shape memory material can assume the first state (e.g., the first shape) if the temperature of the shape memory material exceeds the first temperature threshold, and the shape memory material can assume the second state (e.g., the second shape) if the temperature of the shape memory material falls below the second temperature threshold. Alternatively, the current source can be configured to provide the current flow for the tension element 16 in the second time interval, for example, to heat the shape memory material in the second time interval through the current flow. In this exemplary embodiment, the first temperature threshold can be lower than the second temperature threshold.The shape memory material may assume the first state (such as the first shaping) if the temperature of the shape memory material falls below the first temperature threshold, and the shape memory material may assume the second state (such as the second shaping) if the temperature of the shape memory material exceeds the second temperature threshold.

[0023] In a preferred embodiment, as shown in the Fig. 1, Fig. 2a and Fig. As shown in Figure 2b, the shaft comprises a first groove 12a, a second groove 12b, a first brake shoe 14a, and a second brake shoe 14b. The first groove 12a and the second groove 12b can be arranged on opposite (radial) sides of the shaft body 10. The first brake shoe 14a can be arranged at least partially in the first groove 12a, and the second brake shoe 14b can be arranged at least partially in the second groove 12b. The tension element 16 can be arranged between the first brake shoe and the second brake shoe. Such a (symmetrical) arrangement allows the tension element to be used for multiple brake shoes.

[0024] In the Fig. 1, Fig. 2a and Fig. Figure 2b shows exemplary embodiments of shafts, each with two grooves and two brake shoes. Furthermore, exemplary embodiments with a different number of grooves / brake shoes are also conceivable, such as one groove per brake shoe, three grooves per brake shoes, four grooves per brake shoes, or more. In a further development according to the invention, several hubs can be frictionally coupled to a shaft by means of brake shoes.

[0025] The Fig. 2a and Fig. 2b show a further embodiment of a rotatably mounted element 2000 with a shaft 200 and a hub 300. The rotatably mounted element 2000 can be implemented similarly to the rotatably mounted element 1000 shown in the Fig. 1a and Fig. 1b. In particular, embodiments also provide a system comprising the rotatably mounted element 2000 and the power source 24. The rotatably mounted element 2000 can further comprise the interface 22 for the power source 24.

[0026] In contrast to the wave 100 of the Fig. 1a and Fig. 1b includes wave 200 of the Fig. 2a and Fig. 2b no separate spring. In the Fig. 2a and Fig. 2b, the spring corresponds to the tension element 16, i.e., the tension element 16 is a spring. Consequently, the spring 16 can be dimensioned such that, if the shape memory material has the first state, the first greater tensile force of the spring 16 holds the brake shoes completely in the grooves 12a; 12b (for example, such that the brake shoes 14a; 14b do not protrude beyond a radius of the shaft body), and, if the shape memory material has the second state, the force exerted by the spring 16 on the brake shoes 14a; 14b causes the brake shoes 14a; 14b to protrude at least partially from the grooves 12a; 12b, so that a frictional connection is achieved between the shaft 200 (via the brake shoes 14a; 14b) and the hub 300.

[0027] In Fig. 2a, the second state or the second shaping of the shape memory material of the tension element / spring 16 is shown. As in Fig. 2a, the tension element / spring 16 exerts a force on the brake shoes 14a; 14b in this state, so that they protrude from the grooves 12a; 12b and are coupled to the hub 300 by a frictional connection.

[0028] In Fig. Figure 2b shows the first state or the first shaping of the shape memory material of the tension element / spring 16. The first, larger tensile force of the tension element / spring 16 predominates, so that the brake shoes 14a; 14b are held completely in the grooves 12a; 12b.

[0029] In Fig. 3 shows a further embodiment of a rotatably mounted element 3000, in which the at least one groove 12c is arranged in the hub 350. In contrast to the rotatably mounted elements of Fig. 1a to 2b, a force is thus exerted on the shaft body 10 of the shaft 400 by the at least one brake shoe if the shape memory material has the second state. Otherwise, the rotatably mounted element can be implemented similarly to the rotatably mounted elements as shown in the Fig. 1a to 2b are shown.

[0030] If the shape memory material is in the second state, the tension element made of shape memory material acts on the brake shoe 14c with the second, lower tensile force, so that the brake shoe is pressed against the shaft body and the shaft 400 and the hub 450 are frictionally coupled. If the shape memory material is in the first state, the tension element made of shape memory material acts on the brake shoe 14c with the first, greater tensile force, so that the brake shoe is held completely in the groove 12c. In this state of the shape memory material, the brake shoe 14c does not protrude beyond an inner radius of the hub 350 into the hub, so that a frictional connection between the hub and the shaft is eliminated. The brake shoe can, for example, have a flat profile on the side facing the shaft, as shown. Alternatively, the brake shoe can have a concave profile on the side facing the shaft.

[0031] Fig. 3 also shows the interface 22 for the power supply 24 as well as the power supply 24. Thus, Fig. 3 furthermore the system comprising the rotatably mounted element 3000 and the power supply 24.

[0032] Fig. Figure 4 shows an embodiment of a method for variably coupling a hub to a shaft. The shaft and the hub can be implemented similarly to the shafts 100; 200, 400 and the hub 300, 350 as shown in the Fig. 1a to 3. The shaft is at least partially enclosed by the hub. The shaft comprises at least one groove 12a; 12b; 12c, which is arranged in a shaft body of the shaft or in the hub, at least one brake shoe 14a; 14b; 14c, which is at least partially arranged in the at least one groove 12a; 12b; 12c, and a tension element 16. The tension element 16 is coupled to the at least one brake shoe 14a; 14b; 14c and is at least partially made of a shape memory material.

[0033] The method comprises transforming 110 the shape memory material of the tension element 16 into a first state, so that the tension element 16 acts with a first greater tensile force on the at least one brake shoe 14a; 14b; 14c and the at least one brake shoe is held completely in the groove. The transformation 110 of the shape memory material into the first state may, for example, comprise providing a current flow for the tension element 16, for example via an interface 22 for a current source 24, as shown in Fig.1b. Due to the current flow, the shape memory material of the tension element 16 can be heated above the first temperature threshold and consequently assume the first state. In other words, the transformation 110 of the shape memory material into the first state can include or correspond to providing the current flow through the current source. Alternatively, the transformation 110 of the shape memory material into the first state can include or correspond to switching off the current flow, for example, if the temperature must fall below the first temperature threshold in order to transform the shape memory material into the first state.

[0034] The method further comprises changing 120 a position of the hub relative to the shaft while the at least one brake shoe 14a; 14b; 14c is held completely in the at least one groove 12a; 12b; 12c. Changing 120 the position of the hub relative to the shaft can comprise or correspond to rotating the shaft. The shaft can be rotated, for example, by a motor. In at least some embodiments, the motor is coupled to the power source. For example, a current flow for the motor and the current flow via the interface can occur simultaneously. In at least some embodiments, the rotatably mounted element, which comprises the shaft and the hub, is a suspension of a sensor. For example, the rotatably mounted element can be a suspension of a LIDAR sensor, for example for a LIDAR sensor as described in patent application WO 2017 / 081 294 A1.To adjust the positioning of the sensor, the position of the hub relative to the shaft can be changed 120 in order to achieve a continuous position fixation of the sensor.

[0035] The method further comprises transforming 130 the shape memory material of the tension element 16 into a second state, so that the tension element 16 acts with a second, lower tensile force on the at least one brake shoe 14a; 14b and the at least one brake shoe 14a; 14b; 14c exerts a force on the hub 300 or the shaft body 10, so that the shaft 100 and the hub 300 are force-lockingly coupled.The transformation 130 of the shape memory material of the tension element 16 into the second state can be carried out in the opposite way to the transformation 130 of the shape memory material of the tension element 16 into the first state: If a current flow is provided to transform the shape memory material into the first state, the transformation 130 of the shape memory material into the second state can comprise or correspond to switching off the current flow; If the current flow is switched off to transform the shape memory material into the first state, the transformation 130 of the shape memory material into the second state can comprise providing the current flow to heat the shape memory material by the current flow and exceed the second temperature threshold. Reference symbol 10 shaft bodies 12a groove 12b groove 12c groove 14a brake shoe 14b brake shoe 14c brake shoe 16 Tension element, spring 18 spring 22 Interface 24 Power source 100 Wave 110 Transforming a shape memory material of a tensile element into a first state 120 Changing the position of a hub relative to a shaft 130 Transforming the shape memory material of the tension element into a second state 200 wave 300 hub 350 hub 400 wave 1000 Rotatable element 2000 Rotatable element 3000 Rotatable element

Claims

[1] Rotatably mounted element (1000; 2000) comprising a shaft (100; 200) with a shaft body (10); a hub (300), wherein the shaft (100; 200) is at least partially enclosed by the hub (300); at least one groove (12a; 12b), wherein the at least one groove is arranged in the shaft body (10); at least one brake shoe (14a; 14b), wherein the at least one brake shoe (14a; 14b) is arranged at least partially in the at least one groove (12a; 12b); and a tension element (16), wherein the tension element (16) is coupled to the at least one brake shoe (14a; 14b), wherein the tension element (16) is at least partially made of a shape memory material, wherein the tension element (16) is designed to act on the at least one brake shoe (14a; 14b) with a first greater tensile force in a first state of the shape memory material, so that the at least one brake shoe is held completely in the at least one groove, and wherein the tension element (16) is designed to act on the at least one brake shoe (14a; 14b) with a second, lower tensile force in a second state of the shape memory material. [2] The rotatably mounted element (1000; 2000) according to claim 1, wherein the rotatably mounted element comprises at least one spring, wherein the at least one spring is coupled to the at least one brake shoe (14a; 14b), wherein the at least one spring is configured to exert a force on the at least one brake shoe (14a; 14b) such that a part of the at least one brake shoe protrudes from the at least one groove (12a; 12b) if the shape memory material has the second state. [3] The rotatably mounted element (2000) according to claim 2, wherein the spring corresponds to the tension element (16). [4] The rotatably mounted element (1000) according to claim 2, wherein the at least one spring is additional to the tension element (16). [5] The rotatably mounted element (1000; 2000) according to one of the preceding claims, wherein the at least one groove is arranged in the shaft body (10), wherein the tension element (16) is designed such that the at least one brake shoe (14a; 14b) exerts a force on the hub (300) if the shape memory material has the second state, so that the shaft (100; 200) and the hub (300) are force-fittingly coupled in the second state of the shape memory material. [6] The rotatably mounted element (1000; 2000) according to one of claims 1 to 5, further comprising an interface (22) for a power source (24), wherein the interface is coupled to the tension element (16), wherein the interface (22) is designed to provide a current flow of the power source (24) for the tension element (16) such that the tension element (16) contracts in the first state of the shape memory material. [7] System comprising a rotatably mounted element according to claim 6 and a power source (24), wherein the power source (24) is designed to provide the current flow for the pulling element (16) via the interface (22). [8] The system according to claim 7, wherein the shape memory material has the first state in a first time interval and wherein the shape memory material has the second state in a second time interval, wherein the current source (24) is configured to provide the current flow for the tension element (16) in the first time interval. [9] The system (20) according to claim 7, wherein the shape memory material has the first state in a first time interval and wherein the shape memory material has the second state in a second time interval, wherein the current source (24) is configured to provide the current flow for the tension element (16) in the second time interval. [10] Method for variably coupling a hub to a shaft of a rotatably mounted element, wherein the shaft is at least partially enclosed by the hub, wherein the shaft comprises a shaft body (10), wherein at least one groove (12a; 12b) is arranged in the shaft body (10), wherein at least one brake shoe (14a; 14b) is at least partially arranged in the at least one groove (12a; 12b), and comprises a tension element (16), wherein the tension element (16) is coupled to the at least one brake shoe (14a; 14b) and is at least partially made of a shape memory material, the procedure includes: Transforming (110) the shape memory material of the tension element (16) into a first state, so that the tension element (16) acts with a first greater tensile force on the at least one brake shoe (14a; 14b) and the at least one brake shoe is held completely in the groove; Changing (120) a position of the hub relative to the shaft while the at least one brake shoe (14a; 14b) is held completely in the at least one groove (12a; 12b); and Transforming (130) the shape memory material of the tension element (16) into a second state, so that the tension element (16) acts with a second, lower tensile force on the at least one brake shoe (14a; 14b) and the at least one brake shoe (14a; 14b) exerts a force on the hub or on the shaft body (10), so that the shaft and the hub are force-locked.

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