Drive unit

Abstract

A drive unit according to the present disclosure comprises: an elastic structure that includes at least one spiral-shaped spring; a motor that imparts a rotational drive force to the spiral-shaped spring; a first link that is fixed to a body part of the motor; and a second link that is removeable with respect to the spiral-shaped spring.

Description

Drive unit

[0001] The present disclosure relates to a drive unit.

[0002] Patent Document 1 discloses a walking assist device that can reduce the burden on the user's body. This walking assist device assists walking by swinging a lower leg attachment relative to a thigh attachment by driving a motor.

[0003] Japanese Patent Application Laid-Open No. 2016-106955

[0004] Most drive units in the prior art have been used only for specific purposes such as walking assistance, like the motor in Patent Document 1. After extensive research, the inventors of the present application have come up with the idea of ​​a drive unit that can be used for a wider variety of purposes.

[0005] That is, an object of the present disclosure is to provide a drive unit that can be used for a wider variety of purposes.

[0006] One aspect of the drive unit according to the present disclosure comprises an elastic structure including at least one spiral spring, a motor that applies a rotational driving force to the spiral spring, a first link fixed to a main body of the motor, and a second link that is detachable from the spiral spring.

[0007] According to the present disclosure, a drive unit that can be used for a wider variety of purposes can be provided.

[0008] FIG. 15 is a perspective view of a drive unit (joint mode) according to the present embodiment. FIG. 16 is a perspective view of a drive unit (wheel mode) according to the present embodiment. FIG. 17 is an exploded perspective view of the drive unit shown in FIG. 1. FIG. 3 is a view of the detachable section shown in FIG. 3 alone, viewed from the axial direction. FIG. 4 is an enlarged perspective view of the periphery of the rib in FIG. 4. FIG. 5 is a view illustrating a procedure for switching the drive unit of FIG. 1 from joint mode to wheel mode. FIG. 6 is a block diagram illustrating a control system of the drive unit according to the present embodiment. FIG. 6 is a view illustrating an example of an application of the drive unit according to the present embodiment. FIG. 6 is a view illustrating an example of an application of the drive unit according to the present embodiment. FIG. 6 is a view illustrating an example of an application of the drive unit according to the present embodiment. FIG. 6 is a view illustrating an example of an application of the drive unit according to the present embodiment. FIG. 6 is a perspective view of a drive unit (wheel mode) according to a modified example. FIG. 14 is a perspective view of the drive unit shown in FIG. 14, viewed from a different angle. FIG. 15 is an exploded perspective view of the drive unit shown in FIG. 14.

[0009] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Note that the scope of the present disclosure is not limited to the following embodiments and can be modified as desired within the scope of the technical concept of the present disclosure.

[0010] 1 and 2 are perspective views showing a drive unit 1 according to this embodiment. Fig. 1 shows the drive unit 1 in a "joint mode," and Fig. 2 shows the drive unit 1 in a "wheel mode." That is, the drive unit 1 according to this embodiment can switch between the joint mode and the wheel mode.

[0011] As shown in FIGS. 1 and 2 , the drive unit 1 includes an elastic structure 10, two motors (a first motor 31 and a second motor 32), a first link 60, a second link 50, and a detachable unit 40. The motors 31 and 32 may be, for example, DC motors, or other types of motors. In the joint mode shown in FIG. 1 , the first link 60 and the second link 50 oscillate around a central axis O. In the wheel mode shown in FIG. 2 , the elastic structure 10 rotates around the central axis O while maintaining the relative positions of the first link 60 and the second link 50. The central axis O coincides with the rotation centers of the motors 31 and 32.

[0012] (Direction Definition) In this specification, the direction along the central axis O is referred to as the "axial direction." When viewed from the axial direction, the direction intersecting the central axis O is referred to as the radial direction, and the direction going around the central axis O is referred to as the circumferential direction.

[0013] 3 is an exploded perspective view of the drive unit 1. As shown in FIG. 3, the elastic structure 10 includes two spiral springs (a first spiral spring 11 and a second spiral spring 12). The two spiral springs 11 and 12 are arranged side by side in the axial direction. The two spiral springs 11 and 12 have different winding directions. That is, when viewed from the direction along the central axis O, one of the two spiral springs 11 and 12 is wound in the clockwise direction, and the other is wound in the counterclockwise direction.

[0014] The spiral springs 11 and 12 are formed, for example, from a thin metal plate. However, the material of the spiral springs 11 and 12 may be changed. The drive unit 1 has a first connecting member 13 (see FIG. 6( a)) and a second connecting member 14. The radially inner end of the spiral spring 11 (i.e., the center of the spiral) is fixed to the connecting member 13. The radially inner end of the spiral spring 12 is fixed to the connecting member 14. The connecting members 13 and 14 are cylindrical and extend in the axial direction. The connecting members 13 and 14 are arranged side by side in the axial direction.

[0015] The holes in the connecting members 13 and 14 are so-called D-cut shaped and fit over the rotating shafts 31b and 32b of the motors 31 and 32, respectively. The tips of the rotating shafts 31b and 32b also have D-cut shapes. Therefore, the rotational driving forces of the motors 31 and 32 are transmitted to the spiral springs 11 and 12, respectively, via the connecting members 13 and 14. That is, the connecting member 13 connects the spiral spring 11 to the motor 31, and the connecting member 14 connects the spiral spring 12 to the motor 32. The connection state between the motors 31 and 32 and the spiral springs 11 and 12 remains unchanged regardless of whether the drive unit 1 is in joint mode or wheel mode.

[0016] As shown in Fig. 3, the drive unit 1 includes two expandable tubes (a first tube 21 and a second tube 22). The tube 21 is disposed inside the spiral gap of the spiral spring 11. The tube 22 is disposed inside the spiral gap of the spiral spring 12. The tubes 21 and 22 are each tubular. Although not shown in Fig. 3 and other figures, the ends of the tubes 21 and 22 are connected to the pump 5 (see Fig. 7). It is more preferable that the tubes 21 and 22 have elasticity.

[0017] When the pump 5 supplies air to the tubes 21, 22, the tubes 21, 22 expand. Note that the drive unit 1 may have two pumps 5, and each pump 5 may be connected to a tube 21, 22 individually. Alternatively, two tubes 21, 22 may be connected to one pump 5. Instead of the pump 5, another type of air supply device may be connected to the tubes 21, 22. The tubes 21, 22 in the expanded state function as dampers that attenuate and transmit force.

[0018] As shown in FIG. 3 , the second link 50 is fixed to the detachable portion 40. The second link 50 and the detachable portion 40 may be formed as a single unit. The first link 60 has a connecting member 61, a first support member 62, and a second support member 63. Although detailed description will be omitted, the connecting member 61, the first support member 62, and the second support member 63 are fixed to one another by screws or the like. The first link 60 may be composed of two or less members or four or more members. Furthermore, the members of the first link 60 may be fixed to one another by fixing means other than screws.

[0019] The first support member 62 has a first side wall portion 62a and a first support portion 62b. The second support member 63 has a second side wall portion 63a and a second support portion 63b. The first side wall portion 62a and the second side wall portion 63a are each plate-shaped. As shown in FIG. 1 , the first side wall portion 62a and the second side wall portion 63a face each other in the axial direction. The elastic structure 10 and the detachable portion 40 are located between the first side wall portion 62a and the second side wall portion 63a.

[0020] The first support portion 62b is located at the radially inner end of the first side wall portion 62a, and the second support portion 63b is located at the radially inner end of the second side wall portion 63a. The first support portion 62b and the second support portion 63b are cylindrical and extend in the axial direction. The main body portion 31a of the motor 31 is fixed to the inside of the first support portion 62b. The main body portion 32a of the motor 32 is fixed to the inside of the second support portion 63b. Therefore, the motors 31 and 32 can rotate their respective rotation shafts 31b and 32b with their respective main bodies 31a and 32a supported by the first support portion 62b and the second support portion 63b.

[0021] The connecting member 61 connects the radially outer end of the first side wall portion 62 a to the radially outer end of the second side wall portion 63 a. The connecting member 61, the first support member 62, and the second support member 63 form the first link 60 into an overall C-shape.

[0022] As shown in FIG. 4 , the detachable portion 40 has an annular portion 41, a plurality of ribs 42, a plurality of retaining portions 43, and a protruding portion 44. The annular portion 41 is annular when viewed in the axial direction. When the drive unit 1 is in joint mode, the elastic structure 10, tubes 21, 22, etc. are disposed inside the annular portion 41. The plurality of ribs 42 and the plurality of retaining portions 43 are formed on the inner peripheral surface of the annular portion 41 at intervals in the circumferential direction. The protruding portion 44 protrudes radially outward from the annular portion 41. A second link 50 is fixed to the protruding portion 44.

[0023] As shown in Fig. 5, the rib 42 extends in the axial direction. The holding portion 43 has a flange portion 43a and a facing portion 43b. The flange portion 43a extends radially inward from the rib 42. The facing portion 43b extends axially from the radially inner end of the flange portion 43a. The facing portion 43b and the annular portion 41 face each other in the radial direction. The rib 42 is disposed in a portion of the annular portion 41 facing the facing portion 43b.

[0024] A gap is provided between the opposing portion 43b and the annular portion 41, and the outermost peripheral portions of the spiral springs 11 and 12 are accommodated in this gap. The outermost peripheral portion of the spiral spring 11 is formed with a plurality of grooves 11a that fit into the plurality of ribs 42, respectively (see FIG. 3). Similarly, the outermost peripheral portion of the spiral spring 12 is formed with a plurality of grooves 12a that fit into the plurality of ribs 42, respectively. The grooves 11a and 12a are recessed radially inward from the outer peripheral surfaces of the spiral springs 11 and 12 and extend in the axial direction. The grooves 11a of the spiral spring 11 and the grooves 12a of the spiral spring 12 may fit into a common rib 42. Alternatively, the grooves 11a and 12a may fit into different ribs 42, respectively.

[0025] When the drive unit 1 is in the joint mode (FIG. 1), the rib 42 is engaged with the grooves 11a and 12a. On the other hand, when the drive unit 1 is in the wheel mode (FIG. 2), the engagement between the rib 42 and the grooves 11a and 12a is released.

[0026] In this specification, the spiral springs 11, 12, connecting members 13, 14, tubes 21, 22, first link 60, second link 50, and detachable part 40 may be collectively referred to as the "conversion mechanism M." The conversion mechanism M enables the drive unit 1 to be converted between the wheel mode and the joint mode. The procedure for converting the drive unit 1 from the joint mode (FIG. 1) to the wheel mode (FIG. 2) will be described using FIG. 6.

[0027] First, as shown in FIG. 6( a), the detachable portion 40 and the second link 50 are slid in the axial direction (the direction of the arrow in FIG. 6( a)). This causes the rib 42 of the detachable portion 40 to disengage from the grooves 11a and 12a of the spiral springs 11 and 12. Next, as shown in FIG. 6( b), the detachable portion 40 and the second link 50 are rotated around the central axis O. This places the drive unit 1 in the wheel mode shown in FIG. 2. The second link 50 and the first link 60 may be fixed with a fastener or the like so that the relative positions (relative angles around the central axis O) between the second link 50 and the first link 60 are stable. In particular, when the elastic structure 10 is used as a wheel of a wheelchair or the like, it is preferable to fix the relative positions of the second link 50 and the first link 60. After the drive unit 1 is switched to the wheel mode, an elastic annular member may be fitted around the outer peripheries of the spiral springs 11 and 12 (i.e., the outer periphery of the elastic structure 10). The annular member can be provided with functions such as absorbing shocks like a tire and preventing slippage between the annular member and the traveling surface. Examples of materials for the annular member include rubber and silicone. To switch from wheel mode to joint mode, simply follow the steps described above in reverse.

[0028] The operation of each part in the joint mode and the wheel mode will be described below.

[0029] <In the joint mode> In the joint mode, the rib 42 of the detachable portion 40 is fitted into the grooves 11a, 12a of the spiral springs 11, 12. In this state, the spiral springs 11, 12 and the detachable portion 40 are fixed at least at the fitted portions. The outermost peripheral portions of the spiral springs 11, 12 are sandwiched between the annular portion 41 and the retaining portion 43, so that the fitted state between the rib 42 and the grooves 11a, 12a is maintained. In other words, the retaining portion 43 serves to maintain the fitted state between the rib 42 and the grooves 11a, 12a.

[0030] When motors 31, 32 rotate, the rotation is transmitted to the central portions of spiral springs 11, 12 via connecting members 13, 14. Because spiral springs 11, 12 are elastic, spiral springs 11, 12 can move relative to detachable part 40 at locations away from the portion where they engage with rib 42. For example, when motor 31 rotates in the direction opposite to the winding direction of spiral spring 11, the central portion of spiral spring 11 is wound around the outer periphery of connecting member 13. At this time, at least a portion of the rotational force of motor 31 is also transmitted to detachable part 40 via spiral spring 11. Note that the "winding direction" refers to the direction of rotation of the spiral from the center of the spiral shape toward the outside.

[0031] Like the motor 31, at least a portion of the rotational force of the motor 32 is also transmitted to the detachable part 40. The detachable part 40 is fixed to the second link 50. In other words, when the drive unit 1 is in joint mode, the rotation of the motors 31 and 32 causes the second link 50 and the first link 60 to swing about the central axis O. The responsiveness (transmission rate of rotational force, response speed, etc.) when the input, that is, the rotation of the motors 31 and 32, appears as an output, that is, the swing of the second link 50 and the first link 60, can be controlled by the pressure of the air supplied to the tubes 21 and 22.

[0032] For example, when air is supplied to the tubes 21 and 22, the tubes 21 and 22 expand inside the gaps between the spiral springs 11 and 12. When the tubes 21 and 22 expand and come into close contact with the spiral springs 11 and 12, the apparent rigidity of the elastic structure 10 increases. This increases the transmission rate and response speed of the rotational force from the input (rotation of the motors 31 and 32) to the output (oscillation of the second link 50 and the first link 60). The apparent rigidity of the elastic structure 10 is correlated with the air pressure in the tubes 21 and 22. In other words, increasing the air pressure in the tubes 21 and 22 increases the transmission rate and response speed of the rotational force, and decreasing the air pressure decreases the transmission rate and response speed of the rotational force.

[0033] <Wheel Mode> In wheel mode, as shown in Figure 2, the spiral springs 11 and 12 are not housed inside the annular portion 41 of the detachable portion 40. In other words, the elastic structure 10 is exposed. When the motors 31 and 32 are rotated in this state, the spiral springs 11 and 12 rotate around the central axis O. Therefore, the elastic structure 10 can be considered as a single wheel. It is also possible to change the outer diameter of the elastic structure 10 by controlling the pressure of the air supplied to the tubes 21 and 22 and the direction of rotation of the motors 31 and 32.

[0034] For example, when the pressure of the air supplied to the tubes 21 and 22 is increased, the tubes 21 and 22 expand, and the outer diameter of the elastic structure 10 increases. Conversely, when the pressure of the air supplied to the tubes 21 and 22 is decreased, the tubes 21 and 22 contract, and the outer diameter of the elastic structure 10 decreases. Furthermore, for example, when the motor 31 is rotated in the direction opposite to the winding direction of the spiral spring 11, the outer diameter of the spiral spring 11 increases. Conversely, when the motor 31 is rotated in the same direction as the winding direction of the spiral spring 11, the outer diameter of the spiral spring 11 decreases. Figure 2 shows a state in which the outer diameter of the elastic structure 10 is larger than the outer diameter of the annular portion 41 of the detachable portion 40.

[0035] The drive unit 1 has at least six control parameters (the rotation direction of the motor 31, the rotation speed of the motor 31, the rotation direction of the motor 32, the rotation speed of the motor 32, the pressure in the tube 21, and the pressure in the tube 22). Using these six control parameters, it is possible to control the outer diameter, the rotation direction, and the rotation speed of the elastic structure 10 as a wheel.

[0036] Next, the control system of the drive unit 1 will be described using FIG. 7 . As shown in FIG. 7 , the drive unit 1 is controlled by a control unit C. In this specification, the drive unit 1 and the control unit C may be collectively referred to as the "drive system S." As shown in FIG. 7 , the drive unit 1 includes an IMU (Inertial Measurement Unit) sensor 4. The IMU sensor 4 is capable of measuring physical quantities such as the attitude or rotational speed of the conversion mechanism M. The "attitude of the conversion mechanism M" includes, for example, the angle between the first link 60 and the second link 50 when the drive unit 1 is in joint mode. The "rotational speed" includes, for example, the rotational speed of the elastic structure 10 when the drive unit 1 is in wheel mode. Physical quantities other than those described above may also be measured by the IMU sensor 4. The measurement results by the IMU sensor 4 are input to the control unit C. The control unit C may perform feedback control of the drive unit 1 based on the measurement results by the IMU sensor 4.

[0037] The control unit C includes a controller 2, an embedded system 3, a pressure sensor 6, a motor sensor 7, a driver 8, etc. When the pump 5 supplies air to the tubes 21, 22, the pressure inside the tubes 21, 22 increases. This pressure is measured by the pressure sensor 6. The motor sensor 7 includes a current sensor that measures the current flowing through the motors 31, 32, an encoder that measures the rotation angles of the motors 31, 32, etc. Measurement data from the pressure sensor 6 and the motor sensor 7 is input to the embedded system 3.

[0038] The controller 2 receives information from the embedded system 3 and generates a control signal for controlling the drive unit 1. The control signal may reflect the calculation result of feedback control. The control signal is input to the driver 8 via the embedded system 3. Based on the control signal, the driver 8 supplies current and voltage to the motors 31, 32 and the pump 5. As a result, the motors 31, 32 rotate the elastic structure 10, and the pump 5 supplies air to the tubes 21, 22.

[0039] Each function of the controller 2, the embedded system 3, etc. is realized by a hardware processor such as a CPU (Central Processing Unit) executing a program (software). Some or all of these components may be realized by hardware (including circuitry) such as an LSI (Large Scale Integration), an ASIC (Application Specific Integrated Circuit), an FPGA (Field-Programmable Gate Array), or a GPU (Graphics Processing Unit), or may be realized by a combination of software and hardware. The program may be stored in a storage device (not shown) in advance, or may be stored on a removable storage medium (non-transitory storage medium) such as a DVD or CD-ROM, and installed in the storage device by inserting the storage medium into a drive device.

[0040] Next, examples of applications of the drive unit 1 will be described. Note that Figs. 8 to 13 schematically show the components of the drive unit 1. As shown in Fig. 8, the drive unit 1 can be used as part of a walking assist device. Specifically, the drive unit 1 is in joint mode, and the second link 50 and the first link 60 each form part of the exoskeleton of the walking assist device. The swinging of the second link 50 and the first link 60 can assist the user's walking.

[0041] As shown in Figure 9, the drive unit 1 can be used as part of a wheelchair. Specifically, the drive unit 1 is in wheel mode, the elastic structure 10 is used as a wheel, and the second link 50 and the first link 60 are used as the supporting frame of the chair. By changing the outer diameter of the elastic structure 10, the wheel size can be adjusted to suit the user's body type. It is also possible to realize the walking assist device shown in Figure 8 and the wheelchair shown in Figure 9 using the same drive unit 1.

[0042] As shown in Figure 10, the drive unit 1 can be used in a device that assists a user in standing up. Specifically, as shown in Figure 10(a), in the drive unit 1 (wheel mode) used as part of a wheelchair, the outer diameter of the elastic structure 10 is deformed to be smaller as shown in Figure 10(b). At this time, elastic energy is stored in the spiral springs 11 and 12. By releasing this elastic energy and deforming the outer diameter of the elastic structure 10 to be larger, it is possible to assist the user in standing up, as shown in Figure 10(c).

[0043] As shown in Figure 11, the drive unit 1 can be used as part of a wheelchair whose wheels have variable outer diameters. Specifically, the elastic structures 10 provided in each of the two drive units 1 are used as both wheels of the wheelchair. As shown in Figures 11(a) to 11(c), when one wheel goes over a step, the outer diameter of that wheel (elastic structure 10) is reduced, while the outer diameter of the other wheel remains constant. In this case, it is possible to prevent the user's posture from being disrupted when the wheelchair goes over a step.

[0044] As shown in FIG. 12 , the drive unit 1 can be used as part of a wheelchair equipped with an automatic braking function. Specifically, four drive units 1 are provided on the wheelchair. The elastic structures 10 of the two front drive units 1 are referred to as front wheels Wf. The elastic structures 10 of the two rear drive units 1 are referred to as rear wheels Wr. As shown in FIGS. 12( a) and 12(b), when a moving wheelchair approaches an obstacle, the outer diameter of the rear wheels Wr is reduced and the outer diameter of the front wheels Wf is increased. This causes the center of gravity G of the wheelchair to move toward the rear wheels Wr, and the distance between the center of gravity G and the ground is reduced. In this state, the force experienced by the user when the wheelchair suddenly stops is reduced. An automatic braking function may be realized by equipping the wheelchair with an obstacle sensor that detects obstacles ahead and incorporating the obstacle sensor into the drive system S (see FIG. 7 ). Inertial force sensors may also be provided at multiple locations on the wheelchair to monitor the position, status, etc. of the wheelchair system.

[0045] 13, the drive unit 1 can be used as a wheel for a vehicle. By changing the outer diameter of the elastic structures 10 used as the front and rear wheels of the vehicle, it becomes possible to control the attitude of the vehicle with a high degree of freedom.

[0046] In this embodiment, the elastic structure 10 includes two spiral springs 11 and 12. However, the number of spiral springs may be one. Also, the tubes 21 and 22 may be omitted. In these cases, the drive unit 1 can be switched between joint mode and wheel mode, and can be used for a variety of purposes. The number of tubes and motors provided in the drive unit 1 may be one, depending on the number of spiral springs.

[0047] As described above, the drive unit 1 according to the present disclosure includes an elastic structure 10 including at least one spiral spring (first spiral spring 11 or second spiral spring 12), a motor (first motor 31 or second motor 32) that applies a rotational driving force to the spiral spring, a first link 60 fixed to a main body of the motor, and a second link 50 that is detachable from the spiral spring. According to the present disclosure, a drive unit 1 that can be used for a variety of purposes can be provided.

[0048] The drive unit 1 may further include an expandable tube (first tube 21 or second tube 22) disposed in the spiral gap of the spiral spring. In this case, by controlling the pressure of air supplied to the tube, it is possible to change the damping performance of the tube or the apparent rigidity of the elastic structure 10.

[0049] Furthermore, the elastic structure 10 may include two spiral springs 11, 12, the two spiral springs 11, 12 having different winding directions, and the second link 50 may be detachable from the two spiral springs 11, 12. Using two spiral springs 11, 12 in this manner increases the degree of freedom in controlling the drive unit 1, making it possible to use it for a wider variety of applications.

[0050] The drive unit 1 may also include two expandable tubes 21, 22 arranged in the spiral gaps of the two spiral springs 11, 12. In this case, the degree of freedom in controlling the drive unit 1 can be further increased by using the pressure of the air supplied to each of the two tubes 21, 22 as a control parameter.

[0051] The drive unit 1 may also include two motors 31 and 32, which apply rotational drive forces to the two spiral springs 11 and 12, respectively. In this case, the degree of freedom in controlling the drive unit 1 can be further increased by using the rotation directions and rotation speeds of the two motors 31 and 32 as control parameters.

[0052] The drive unit 1 further includes a detachable part 40 fixed to the second link 50. The detachable part 40 has an annular part 41 capable of accommodating the elastic structure 10 and a rib 42 formed on the inner peripheral surface of the annular part 41 and extending in the axial direction (direction along the central axis O) of the motors 31 and 32. The spiral springs 11 and 12 may have grooves 11a and 12a that engage with the rib 42. In this case, in the joint mode, the rib 42 engages with the grooves 11a and 12a, so that the driving force of the motors 31 and 32 can be transmitted to the second link 50 via the spiral springs 11 and 12 and the detachable part 40. This allows the first link 60 and the second link 50 to swing. In the wheel mode, the rib 42 is disengaged from the grooves 11a and 12a, allowing the elastic structure 10 to rotate relative to the first link 60 and the second link 50, allowing the elastic structure 10 to be used as a wheel. By sliding the detachable portion 40 in the axial direction relative to the elastic structure 10, the drive unit 1 can be switched between the joint mode and the wheel mode.

[0053] (Modification) Next, a modification of the embodiment will be described. A drive unit 1A according to the modification is shown in Fig. 14. In the drive unit 1A, parts that are the same as those in the drive unit 1 are given the same reference numerals, and their description will be omitted.

[0054] As shown in FIG. 14 , the drive unit 1A includes a detachable portion 40A, a second link 50A, a pair of detachable motors 33, a pair of swing arms 70, and a pair of bearings 80. One end of the swing arm 70 is connected to the first link 60 via the bearing 80. The bearing 80 is arranged coaxially with the central axis O. This allows the swing arm 70 to swing around the central axis O. However, the bearing 80 has an electromagnetic locking function, allowing the swing arm 70 to be switched between a swingable state and a non-swingable state. Each detachable motor 33 is fixed to the other end of each swing arm 70. The second link 50A is fixed to the detachable portion 40A. The second link 50A includes a pair of motor connectors 51. Each motor connector 51 extends from the second link 50A toward the corresponding detachable motor 33. The motor connection part 51 is directly or indirectly connected to the detachment motor 33. The motor connection part 51 is a part for transmitting the rotational driving force of the detachment motor 33 to the second link 50A and the detachment part 40A.

[0055] The detachable portion 40A has an arc-shaped portion 41A. The arc-shaped portion 41A is semicircular. When the drive unit 1A is in joint mode (not shown), the arc-shaped portion 41A abuts or approaches the elastic structure 10 from the radially outer side. When the drive unit 1A is in wheel mode (FIG. 14), the arc-shaped portion 41A is separated from the elastic structure 10.

[0056] 15, a plurality of electromagnetic locks 42A are provided on the inner peripheral surface of the arc-shaped portion 41A. A plurality of permanent magnets 15 are fixed to the outer peripheral surface of the elastic structure 10 (i.e., the outer peripheral surfaces of the spiral springs 11 and 12) so as to correspond to these electromagnetic locks 42A.

[0057] When the drive unit 1A is in joint mode, the electromagnetic lock 42A is supplied with power and functions as an electromagnet, generating an attractive force (magnetic force) between the electromagnetic lock 42A and the permanent magnet 15. This attractive force fixes the detachable part 40A to the outer peripheral surface of the elastic structure 10. Therefore, when the motors 31 and 32 are driven, the rotational driving force is transmitted to the detachable part 40A via the elastic structure 10. The detachable part 40A is also connected to the swing arm 70 via the second link 50A. As a result, when the motors 31 and 32 are driven, the second link 50A and the first link 60 swing relatively around the central axis O. Note that when the second link 50A and the first link 60 swing relatively, the electromagnetic lock of the bearing 80 is turned off. To fix the relative angle between the second link 50A and the first link 60, the electromagnetic lock of the bearing 80 can be turned on.

[0058] When the drive unit 1A is switched from the joint mode to the wheel mode, the electromagnetic lock 42A of the detachable part 40A is turned off. Also, the detachable motor 33 is driven to rotate the second link 50A around the central axis O1 of the detachable motor 33. This separates the detachable part 40A from the elastic structure 10, and the drive unit 1A enters the wheel mode.

[0059] When switching the drive unit 1A from wheel mode to joint mode, the detachment motor 33 is driven to rotate the second link 50A around the central axis O1 of the detachment motor 33. This causes the detachment part 40A to approach the elastic structure 10. Furthermore, the electromagnetic lock 42A of the detachment part 40A is turned on. This causes an attractive force to act between the electromagnetic lock 42A and the permanent magnet 15, fixing the detachment part 40A and the elastic structure 10, and the drive unit 1A enters wheel mode.

[0060] As described above, the drive unit 1A according to the modified example includes the detachable part 40A fixed to the second link 50A and the detachable motor 33 that can move the detachable part 40A toward and away from the elastic structure 10. The permanent magnet 15 is disposed on the outer peripheral surface of the elastic structure 10, and the detachable part 40A has an electromagnetic lock 42A that can generate an attractive force between the permanent magnet 15 and the detachable part 40A. With this configuration, switching between the joint mode and the wheel mode is possible by controlling the electromagnetic lock 42A and the detachable motor 33. Therefore, it is possible to provide a drive unit 1A that can more easily switch modes.

[0061] The technical scope of the present disclosure is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present disclosure.

[0062] For example, in the above embodiment, the second link 50 is detachable from the spiral springs 11, 12 together with the detachable portion 40. However, a configuration may be adopted in which the detachable portion 40 and the second link 50 are integrally formed, and the second link 50 itself has the annular portion 41 or the like.

[0063] In addition, the above-described embodiments and modifications may be combined as appropriate.

[0064] DESCRIPTION OF SYMBOLS 1, 1A... Drive unit 10... Elastic structure 11, 12... Spiral spring 11a, 12a... Groove 15... Permanent magnet 21, 22... Tube 31, 32... Motor 33... Detachable motor 40, 40A... Detachable portion 41... Annular portion 42... Rib 42A... Electromagnetic lock 50, 50A... Second link 60... First link

Claims

1. an elastic structure including at least one spiral spring; a motor for applying a rotational driving force to the spiral spring; A first link fixed to a main body of the motor; a second link that is detachable from the spiral spring.

2. The drive unit of claim 1 , further comprising an expandable tube disposed in a spiral gap of the spiral spring.

3. the elastic structure includes two spiral springs including the spiral spring, The two spiral springs have different winding directions, The drive unit according to claim 1 , wherein the second link is detachable from the two spiral springs.

4. The drive unit according to claim 3 , further comprising two expandable tubes disposed in the spiral gaps of the two spiral springs, respectively.

5. Two motors including the motor are provided, The drive unit according to claim 3 , wherein the two motors provide rotational drive forces to the two spiral springs, respectively.

6. A detachable part is further provided, the detachable part being fixed to the second link. the detachable portion has an annular portion capable of accommodating the elastic structure, and a rib formed on an inner circumferential surface of the annular portion and extending in an axial direction of the motor, The drive unit according to claim 1 , wherein the spiral spring has a groove that mates with the rib.

7. A detachable portion fixed to the second link; a motor for attaching and detaching the attachment part to and from the elastic structure, A permanent magnet is disposed on the outer circumferential surface of the elastic structure, The drive unit according to claim 1 , wherein the attachment / detachment section has an electromagnetic lock capable of generating an attractive force between the electromagnetic lock and the permanent magnet.