Drive device

Abstract

A drive device 10 includes: a center pulley 12 (rotor) rotatable around a center axis X; a motor 14 rotating the center pulley 12 in a first direction; a spiral spring 16 (energy storage part) having one end 16A attached to the center pulley 12, extending in association with rotation of the center pulley 12, accumulating energy, contracting when energy is released, and moving around the center axis X so that another end 16B approaches one end 16A; an output part 18 rotating with the movement of the spiral spring 16; and a lock mechanism 20 capable of switching between a lock state for restricting movement of the spiral spring 16 and a lock release state for releasing restriction of movement of the spiral spring 16.

Description

Drive unit

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

[0002] Japanese Patent Application Laid-Open No. 2013-255969 discloses an arm mechanism in which an actuator stretches a tension coil spring to store energy while an arm is fixed by a locking means, and the energy of the spring is released by releasing the arm from the locking means, which then serves as a rotational force for the arm.

[0003] If legged mobile robots could not only walk on flat ground but also perform dynamic movements such as jumping and running, they would be able to overcome steps and the range of tasks they could perform would be expanded. The joint drive units required to operate legged robots that perform high jumps, agile running, and other dynamic movements frequently must be able to output high speeds and large torques in short intervals. Additionally, reducing the mass of the drive units is desirable to achieve high acceleration.

[0004] When trying to obtain a large output using a small actuator with low output power in order to reduce mass, if energy is stored in a spring over a long period of time with a high reduction ratio and high torque, the energy that can be extracted from the actuator will be large. However, because such a structure requires a long time to store energy, while it is suitable for movements such as a one-time vertical jump, it is not suitable for movements such as continuous jumping.

[0005] In the above-mentioned conventional example, in order to rotate the arm in the same way again, it is necessary to return the rotated arm to its initial position, and it is considered difficult to operate the arm in a short interval.

[0006] An object of the present disclosure is to enable a drive device to intermittently repeat outputs at short intervals.

[0007] In this drive device, an actuator constantly rotates a rotating body. One end of an energy storage unit is attached to the rotating body. When the rotating body is rotated in a locked state in which the movement of the energy storage unit is restricted by a locking mechanism, the energy storage unit expands and stores energy. When the locking mechanism is unlocked and the restriction on the movement of the energy storage unit is released in the energy-stored state, the energy storage unit contracts and moves around the central axis so that the other end of the energy storage unit approaches the one end. At this time, the energy stored in the energy storage unit is released. This energy is output from an output unit that rotates due to the movement of the energy storage unit. Note that, because the rotating body to which one end of the energy storage unit is attached is constantly rotated by the actuator, the rotating body is prevented from rotating in the reverse direction so that the one end of the energy storage unit approaches the other end when the energy is released.

[0008] Since the rotor is constantly rotating, locking the energy storage unit after releasing the energy immediately starts storing energy. This means there is no need to return the rotor to its initial position for the next energy storage. This means that output can be repeated intermittently at short intervals.

[0009] By using the output of the output unit to move the legs of the robot, for example, dynamic movements such as jumping and running can be performed with high frequency.

[0010] The drive device of the first aspect includes a rotating body that is rotatable around a central axis, an actuator that rotates the rotating body in a first direction, an energy storage unit that has one end attached to the rotating body, expands as the rotating body rotates to store energy, and contracts when the energy is released, moving around the central axis so that the other end approaches the one end, an output unit that rotates as the energy storage unit moves, and a locking mechanism that can switch between a locked state that restricts movement of the energy storage unit and an unlocked state that releases the restriction on movement of the energy storage unit.

[0011] In a second aspect, in the drive device according to the first aspect, the energy storage unit is a constant force spring.

[0012] In this drive device, the energy storage section is a constant force spring, so even if the actuator is small, lightweight, and relatively weak, it is possible to extend the energy storage section and store energy.

[0013] In a third aspect, in the drive device according to the first aspect, the energy storage unit also stores, as energy, an external force input so as to extend the energy storage unit, in addition to the input from the actuator.

[0014] In this drive unit, the energy storage unit stores as energy an external force input to extend the energy storage unit, such as a reaction force when the robot's legs touch the ground, thereby enabling higher performance to be achieved.

[0015] In a fourth aspect, the drive device according to the third aspect further includes a planetary gear mechanism including a sun gear, planetary gears that mesh with the sun gear and revolve around the sun gear while rotating on their axes, and an internal gear that meshes with the planetary gear, wherein the actuator rotates the sun gear in addition to the rotating body, the other end of the energy storage unit is attached to a carrier that supports the planetary gear, and the output unit outputs the rotational torque of the internal gear.

[0016] In this drive unit, the inputs to the planetary gear mechanism include the input from the actuator to the sun gear and the input from the energy storage unit to the carrier. The input from the energy storage unit to the carrier includes energy stored by external forces. The output from the planetary gear mechanism is output from the internal gear to the output unit. The output is determined by the difference between the rotation of the sun gear and the rotation of the carrier.

[0017] According to the present disclosure, the output can be repeated intermittently at short intervals.

[0018] Fig. 1 is a diagram schematically showing a drive device according to the present embodiment; Fig. 2 is a diagram schematically showing an operation when an energy storage unit is placed in a locked state and energy is stored in the energy storage unit in the drive device according to the present embodiment; Fig. 3 is a diagram schematically showing an operation when an energy storage unit is placed in an unlocked state and energy is released from the energy storage unit in the drive device according to the present embodiment; Fig. 4 is a diagram showing the appearance of a test device; Fig. 5 is a diagram showing test results;

[0019] Hereinafter, embodiments for carrying out the present disclosure will be described with reference to the drawings. Components indicated by the same reference numerals in each drawing are the same or similar components. Note that duplicated explanations and reference numerals may be omitted in the embodiments described below. Furthermore, all drawings used in the following description are schematic, and the dimensional relationships, ratios, etc. of each element shown in the drawings do not necessarily match those in reality. Furthermore, the dimensional relationships, ratios, etc. of each element between multiple drawings do not necessarily match.

[0020] In FIG. 1, a drive device 10 according to this embodiment includes a central pulley 12 as an example of a rotating body, a motor 14 as an example of an actuator, a spiral spring 16 as an example of an energy storage unit, an output unit 18, a locking mechanism 20, and a planetary gear mechanism 22.

[0021] The central pulley 12 is rotatable about a central axis X. A gear 24 is attached coaxially to the central pulley 12.

[0022] The motor 14 is a drive source for rotating the central pulley 12 in a first direction, specifically, the left direction in FIGS. 2 and 3 , and steadily rotates during operation. A small gear 26 and a large gear 28 are coaxially attached to the rotation shaft of the motor 14. The small gear 26 meshes with the gear 24 of the central pulley 12. The large gear 28 meshes with a gear 30 that is rotatable around the central axis X. A sun gear 36 of the planetary gear mechanism 22 is attached, for example, coaxially to the gear 30. As the gear 30 rotates, the sun gear 36 also rotates. In this embodiment, the motor 14 rotates in the direction opposite to the first direction (rightward), and the central pulley 12 and the sun gear 36 rotate in the first direction (leftward).

[0023] The power spring 16 is a constant force spring that has one end 16A attached to the central pulley 12, expands as the central pulley 12 rotates, stores energy, and contracts when the energy is released, moving around the central axis X so that the other end 16B approaches the one end 16A. A constant force spring is a spring in which the load is approximately constant regardless of the stroke. One end 16A of the power spring 16 is attached to, for example, the outer circumferential surface of the central pulley 12. The other end 16B of the power spring 16 is attached to an arm 42A extending from a carrier 42 of the planetary gear mechanism 22, which will be described later. Note that other members may be interposed between the one end 16A and the other end 16B of the power spring 16. Any configuration is possible as long as one end 16A can move around the central axis X so that it expands and moves away from the other end 16B as the central pulley 12 rotates when energy is stored, and contracts and moves the other end 16B closer to the one end 16A when energy is released.

[0024] The output portion 18 is a portion that rotates in accordance with the movement of the power spring 16, and corresponds to the shaft of the bevel gear 44 in FIG. 1, and to the internal gear 40 of the planetary gear mechanism 22 described later in FIGS.

[0025] The locking mechanism 20 is a mechanism that can switch between a locked state ( FIG. 2 ) in which movement of the spiral spring 16 is restricted and an unlocked state ( FIG. 3 ) in which the restriction on movement of the spiral spring 16 is released. As an example, the locking mechanism 20 includes a motor 32 and a latch 34 as an example of a locking member. The latch 34 is driven by the motor 32 and configured to be able to engage with the carrier 42 or a member that rotates together with the carrier 42. For example, when the latch 34 engages with the carrier 42, the locking mechanism 20 is in a locked state in which rotation of the carrier 42 is restricted, and when the latch 34 is released from the engagement, the locking mechanism 20 is in an unlocked state in which the carrier 42 is rotatable.

[0026] The power spring 16 is configured to store, as energy, an external force input to extend the power spring 16, in addition to the input from the motor 14. To achieve this, a one-way clutch such as a ratchet may be used in the lock mechanism 20. In other words, in Figures 2 and 3, the carrier 42 in the locked state cannot rotate counterclockwise, in which case the power spring 16 contracts, but may be able to rotate clockwise, in which case the power spring 16 expands.

[0027] The planetary gear mechanism 22 includes a sun gear 36, for example, three planetary gears 38 that mesh with the sun gear 36 and revolve around the sun gear 36 while rotating, and an internal gear 40 that meshes with the planetary gears 38.

[0028] The motor 14 rotates the sun gear 36 via the pinion 26, the gear 28, and the gear 30 as described above, in addition to the central pulley 12. The other end 16B of the spiral spring 16 is attached to a carrier 42 that supports the planetary gears 38. The output section 18 is configured to output the rotational torque of the internal gear 40.

[0029] The planetary gear mechanism 22 is depicted as a differential device in FIG. 1 . Because a planetary gear mechanism is a type of differential device, the planetary gear mechanism 22 may also be a differential device. In the differential device of FIG. 1 , rotation of the motor 32 is input to a side gear 46 via the large gear 28 and the gear 30. Rotation of a member corresponding to the carrier 42 attached to the other end 16B of the spiral spring 16 is transmitted to a side gear 50 facing the side gear 46. A pinion gear 48 meshes with the side gears 46, 50. A ring gear 52 is attached to a case 49 supporting the pinion gear 48. The ring gear 52 meshes with the bevel gear 44 of the output unit 18. In the differential device of FIG. 1 , the pinion gear 48 rotates along the side gears 46, 50 due to the difference in rotation between the side gears 46, 50, causing the ring gear 52 to rotate, and the rotational torque of the bevel gear 44 is output from the output unit 18.

[0030] In this mechanism, when energy is stored, the central pulley 12 (referred to as "A") and the carrier 42 (referred to as "B") rotate in opposite directions relative to each other through an angle θ ｏ１ and θ, the angle by which the carrier 42 rotates when the energy is released. ｏ２ However, the directions are opposite to each other and the magnitudes are equal (θ ｏ１ = -θ ｏ２ The procedure for designing such a planetary gear mechanism 22 will be described. First, the rotation angle of A is set to θ ａ , the rotation angle of B is θ ｂ and the output angle θ via the planetary gear mechanism 22 is ｏ = k ａ θ ａ +k ｂ θ ｂ In this case, k ａ , k ｂ is the transfer ratio to the output for each input. Next, when energy is stored, A moves at an angle θ ａ = θ rotation. Since B is fixed, θ ｂ = 0. Therefore, the rotation angle θ ｏ１ = k ａOn the other hand, when the energy is released, B moves by the amount of elastic energy stored in the power spring 16, so θ ｂ When the energy is released, the motor 14 continues to rotate, but when the energy is released, the ａ is negligibly small (θ ａ ≒0), then the output angle θ ｏ２ = k ｂ θ is. θ ｏ１ = -θ ｏ２ Since k ａ = -k ｂ Therefore, the output of the planetary gear mechanism 22 is expressed as follows:

[0031]

[0032] From this equation, it can be said that this operating mechanism is a mechanism that outputs the difference in angle between A and B, i.e., the amount of extension of the spiral spring 16, as an angle, regardless of the positions of the central pulley 12 (A) and the carrier 42 (B).

[0033] The contribution of the two inputs to the output in the planetary gear mechanism 22 is expressed as follows: First, the relationship between the input sun gear 36 and the output internal gear 40 is expressed as follows: If the rotation angle of the motor 14 during energy storage is θi, the contribution to the output θ ｏ１ is expressed as follows:

[0034]

[0035] Here, Z ａ , Z ｃ are the numbers of teeth of the sun gear 36 and the internal gear 40, respectively, and N ｉ１ is the reduction ratio between the motor 14 and the sun gear 36. Next, if the spring system is considered as the input of the carrier 42, the arrangement of the solar type planetary gear device is obtained. In addition, the rotation angle of the carrier 42 is equal to the rotation angle of the central pulley 12 when energy is stored. If the reduction ratio between the motor 14 and the central pulley 12 is N ｉ２ Then, the contribution to the final output is ｏ２ is expressed as follows:

[0036]

[0037] Therefore, the final output θ using this planetary gear mechanism 22 ｏ is expressed as follows:

[0038]

[0039] In order for this to be equivalent to equation (1), θ ｏ１ / θ ｏ２ = -1. Therefore, the following relationship must be satisfied:

[0040]

[0041] Since the number of teeth that can be selected when configuring the planetary gear mechanism 22 is limited, in actual design, first Z ａ , Z ｃ After selecting N ｉ１ , N ｉ２ As a design example, Z ａ = 19, Z ｃ = 57, N ｉ１ = 1 / 2, N ｉ２ =2.

[0042] (Operation) This embodiment is configured as described above, and its operation will be described below. In Figures 2 and 3, thin arrows indicate rotation originating from the motor 14, thick arrows indicate rotation originating from the spiral spring 16, and dashed lines indicate directly connected rotation transmission. In other words, the members connected by dashed lines rotate integrally. The arrow labeled "OUTPUT" indicates rotation of the output unit 18. The two-dot chain arrow in Figure 2 indicates rotation of the carrier 42 due to an external force.

[0043] 2 and 3 , in the drive device 10 according to this embodiment, a motor 14 constantly rotates a central pulley 12. One end 16A of a spiral spring 16 is attached to the central pulley 12. When a locking mechanism 20 is in an unlocked state, the spiral spring 16 rotates integrally with the central pulley 12 (a rotating body). When the central pulley 12 is rotated in a locked state in which the movement of the spiral spring 16 is restricted by the locking mechanism 20, the spiral spring 16 expands and stores energy.

[0044] When the locking mechanism 20 is set to the unlocked state in the state in which energy has been accumulated, and the restriction on the movement of the spiral spring 16 is released, the spiral spring 16 contracts and moves around the central axis X so that the other end 16B of the spiral spring 16 approaches the one end 16A. At this time, the energy accumulated in the spiral spring 16 is released. This energy is output from the output part 18, which rotates due to the movement of the spiral spring 16.

[0045] The central pulley 12, to which one end 16A of the power spring 16 is attached, is constantly rotated by the motor 14, so that the central pulley 12 is prevented from rotating in the reverse direction so that one end 16A of the power spring 16 approaches the other end 16B when releasing energy. Since a larger amount of elastic energy is stored, the maximum efficient torque of the motor 14 can be applied regardless of the displacement of the spring.

[0046] Since the central pulley 12 is constantly rotating in the first direction (leftward in FIGS. 2 and 3) due to the rotation of the motor 14, energy storage begins immediately by locking the spiral spring 16 after releasing the energy. In other words, there is no need to return the central pulley 12 to its initial position for the next energy storage. Therefore, output can be repeated intermittently at short intervals.

[0047] By using the output of the output unit 18 to move the legs of the robot, for example, dynamic movements such as jumping and running can be performed at high frequency. Also, by using the output of the output unit 18 to move the hands of the robot, it is possible to frequently shake an instrument such as a flask at high speed or move a tool such as a knife rhythmically. Furthermore, by using this in processing machines that require a large amount of force instantaneously, such as metal processing presses, high-frequency processing becomes possible.

[0048] In this drive device, a constant force spring 16 is used as the energy storage section, so even a small, lightweight, and relatively weak motor 14 can store energy by expanding the spring 16. Furthermore, by using a constant force spring, the torque at the maximum efficiency of the motor 14 can be loaded regardless of the displacement of the spring, and a larger amount of elastic energy can be stored.

[0049] By using, for example, a one-way clutch in the locking mechanism 20, the power spring 16 can store, as energy, an external force input to extend the power spring 16, such as the reaction force when the robot's leg touches the ground, thereby achieving higher performance.

[0050] When the planetary gear mechanism 22 is used, the inputs to the planetary gear mechanism 22 include the input from the motor 14 to the sun gear 36 and the input from the spiral spring 16 to the carrier 42. The input from the spiral spring 16 to the carrier 42 also includes energy stored due to external forces, such as the reaction force when the robot's legs touch the ground. The output from the planetary gear mechanism 22 is output from the internal gear 40 to the output unit 18. The output is determined by the difference between the rotation of the sun gear 36 and the rotation of the carrier 42.

[0051] In this way, according to this embodiment, the motor 14 can be steadily rotated at maximum efficiency while outputting intermittently at short intervals.

[0052] [Other Embodiments] Although one example of an embodiment of the present disclosure has been described above, the embodiment of the present disclosure is not limited to the above, and it goes without saying that various modifications can be made without departing from the spirit of the present disclosure.

[0053] (Test Example) To evaluate the characteristics of the proposed mechanism, a weight was lifted using a large spring output. In the experiment, as shown in FIG. 4, the drive unit according to this embodiment was fixed to a frame, and a weight was lifted by winding a wire around a pulley connected to the output section. The weights used for the measurements were 500 g, 1000 g, and 1500 g. The angle at which the central pulley was rotated to stretch the spring with each weight was increased in five steps of 45 degrees. Because the position of the spring system shifts between when the locking mechanism is activated and when it completely stops, the input angle and the amount of spring extension are linearly related, rather than proportionally. In this test, locking began when the central pulley was rotated a minimum of 67.5 degrees, so 67.5 + 45 degrees was set as the minimum input angle. The maximum torque and maximum speed of the output section upon energy release in each trial were measured using a torque gauge (UNIPULSE UTM II-10 Nm). Measurements are carried out 10 times under each condition and the average values ​​are obtained.

[0054] The measurement results are shown in Figure 5. In Figure 5, the horizontal axis is the input angle and the vertical axis is the rotational speed. Under all conditions, there is a tendency for the output speed to increase as the input angle increases, but it does not continue to increase linearly; as the input angle increases, the rate of increase in speed tends to decrease. This is thought to be because there is a limit to the speed increase due to factors such as friction in the rotating parts of the device.

[0055] [Additional Notes] Possible aspects of the present disclosure will be added below.

[0056] (Supplementary Note 1) A drive device comprising: a rotating body that is rotatable around a central axis; an actuator that rotates the rotating body in a first direction; an energy storage unit that has one end attached to the rotating body, expands as the rotating body rotates to store energy, and contracts when the energy is released, moving around the central axis so that the other end approaches the one end; an output unit that rotates as the energy storage unit moves; and a locking mechanism that can switch between a locked state that restricts movement of the energy storage unit and an unlocked state that releases the restriction on movement of the energy storage unit.

[0057] (Supplementary Note 2) The drive device according to Supplementary Note 1, wherein the energy storage unit is a constant force spring.

[0058] (Supplementary Note 3) The drive device according to Supplementary Note 1 or Supplementary Note 2, wherein the energy storage unit also stores, as energy, an external force input so as to extend the energy storage unit, in addition to the input from the actuator.

[0059] (Appendix 4) A drive device according to any one of Appendices 1 to 3, further comprising a planetary gear mechanism including a sun gear, planetary gears that mesh with the sun gear and revolve around the sun gear while rotating on their axes, and an internal gear that meshes with the planetary gear, wherein the actuator rotates the sun gear in addition to the rotating body, the other end of the energy storage unit is attached to a carrier that supports the planetary gear, and the output unit outputs the rotational torque of the internal gear.

[0060] The disclosure of Japanese Patent Application No. 2023-144866, filed on September 6, 2023, is incorporated herein by reference in its entirety. All documents, patent applications, and technical standards mentioned herein are incorporated herein by reference to the same extent as if each individual document, patent application, and technical standard was specifically and individually indicated to be incorporated by reference.

[0061] REFERENCE SIGNS LIST 10 Drive device 12 Central pulley (rotating body) 14 Motor 16 Spiral spring (energy storage section) 16A One end 16B Other end 18 Output section 20 Lock mechanism 22 Planetary gear mechanism 36 Sun gear 38 Planetary gear 40 Internal gear 42 Carrier

Claims

1. A drive device having: a rotating body rotatable around a central axis; an actuator that rotates the rotating body in a first direction; an energy storage unit having one end attached to the rotating body and expanding to store energy as the rotating body rotates and contracting when the energy is released, and moving around the central axis so that the other end approaches the one end; an output unit that rotates in conjunction with the movement of the energy storage unit; and a locking mechanism that can be switched between a locked state that restricts the movement of the energy storage unit and an unlocked state that releases the restriction on the movement of the energy storage unit.

2. The drive device according to claim 1, wherein the energy storage unit is a constant force spring.

3. The drive device according to claim 1, wherein said energy storage section also stores as energy an external force input so as to expand said energy storage section, in addition to the input from said actuator.

4. A drive device as described in claim 3, further comprising a planetary gear mechanism including a sun gear, a planetary gear that meshes with the sun gear and revolves around the sun gear while rotating on its axis, and an internal gear that meshes with the planetary gear, wherein the actuator rotates the sun gear in addition to the rotating body, the other end of the energy storage unit is attached to a carrier that supports the planetary gear, and the output unit outputs the rotational torque of the internal gear.

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