Actuator

Abstract

To provide an actuator which can increase an output torque and decrease a characteristic frequency without increasing a size of the actuator.SOLUTION: An actuator 1 includes: a motor 10; a weight 11 (inertial body; Inertia); transmissions T1, T2; a spring (elastic body) 12; and an output shaft 13. A rotational shaft of the motor 10 is connected to a low-speed-side input shaft of the transmission T1. A high-speed-side output shaft of the transmission T1 is connected to the low-speed-side input shaft of the transmission T2. A rotational shaft (center shaft) of the weight 11 is connected to the high-speed-side output shaft of the transmission T2. Also, a low-speed-side input shaft of the transmission T1 which is a rotational shaft of the motor 10 is connected to one end of the spring 12 coaxially. The other end of the spring 12 is connected to the output shaft 13. A transmission ratio (gear ratio) of the transmissions T1, T2 is set such that a rotational speed of the weight 11 is greater than a rotational speed of the motor 10.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an actuator. [Background technology]

[0002] Generally, it is difficult for a vehicle that moves on wheels to overcome steps on its path. A large torque is required to overcome the step, and a large motor is required to increase the torque.

[0003] For example, Patent Document 1 discloses a series elastic actuator (SEA) that assists torque by exciting a spring. The SEA combines an actuator, spring, and load in series, and is expected to improve impact resistance and motion performance such as maximum torque and maximum speed compared to an actuator alone.

[0004] In addition, the SEA stores kinetic energy in a spring, allowing it to provide a large torque or speed to the load. Attaching a weight to the motor's rotating shaft increases the moment of inertia, increasing the motor's kinetic energy and improving its motion performance. Attaching a weight to the rotating part of the motor can lower the natural frequency of the SEA, which has a fixed load and backdrivability. The moment of inertia of the weight and the rotating part of the motor can be added together. As a result, the natural frequency decreases, and the time that the SEA generates torque in one direction can be extended. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2023-87636 Summary of the Invention [Problem to be solved by the invention]

[0006] In the above-mentioned Patent Document 1, there is a problem that as the rotation speed of the motor increases, resistance due to the influence of back electromotive force etc. increases, resulting in a loss of output torque. Also, while increasing the moment of inertia is an effective way to lower the natural frequency, there is a problem that increasing the weight to increase the moment of inertia makes the actuator itself large and heavy.

[0007] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an actuator that can increase the output torque and lower the natural frequency without increasing the size of the actuator itself. [Means for solving the problem]

[0008] In order to solve the above problems, the present invention employs the following means. That is, the actuator according to the first aspect of the present invention comprises a motor, an elastic body connected to a rotating shaft of the motor, an output shaft connected to the elastic body, an inertial body having a central axis, and a transmission, wherein the rotating shaft of the motor is connected to a low-speed input shaft of the transmission, and the central axis of the inertial body is connected to a high-speed output shaft of the transmission.

[0009] In addition, an actuator according to a second aspect of the present invention includes a motor, an elastic body, an output shaft connected to the elastic body, an inertial body having a central axis, a first transmission, and a second transmission, wherein a rotating shaft of the motor is connected to a low-speed input shaft of the first transmission, a central axis of the inertial body is connected to a high-speed output shaft of the first transmission, a rotating shaft of the motor is connected to a high-speed input shaft of the second transmission, and the elastic body is connected to the low-speed output shaft of the second transmission. [Effects of the Invention]

[0010] According to the present invention, it is possible to increase the output torque and lower the natural frequency without increasing the size of the actuator itself. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic diagram showing the configuration of an actuator in a first embodiment of the present invention. [Figure 2] 3A to 3C are schematic diagrams for explaining the basic operation of an SEA applied to the actuator of the first embodiment. [Figure 3] FIG. 10 is a schematic diagram showing the configuration of an actuator according to the second embodiment. [Figure 4] FIG. 1 is a top view showing the configuration of a rocker bogie vehicle using an actuator according to the present invention. [Figure 5] FIG. 1 is a schematic diagram for explaining the operation of a rocker bogie vehicle using an actuator according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. A. First embodiment FIG. 1 is a schematic diagram showing the configuration of an actuator 1 according to a first embodiment of the present invention. As shown in FIG. 1, the actuator 1 is composed of a motor 10, a weight 11 (inertia), transmissions T1 and T2, a spring (elastic body) 12, and an output shaft 13. The rotating shaft of the motor 10 is connected to the low-speed input shaft of the transmission T1. The high-speed output shaft of the transmission T1 is connected to the low-speed input shaft of the transmission T2. ​​The rotating shaft (center shaft) of the weight 11 is connected to the high-speed output shaft of the transmission T2. ​​One end of the spring 12 is coaxially connected to the rotating shaft of the motor 10, which is also the low-speed input shaft of the transmission T1. The other end of the spring 12 is connected to the output shaft 13.

[0013] As described above, in the first embodiment, the rotation shaft of the motor 10 and the rotation shaft of the weight 11 are separated, and the transmissions T1 and T2 are arranged so that rotation is transmitted by gears. The speed ratio (gear ratio) of the transmissions T1 and T2 is set so that the rotation speed of the weight 11 is greater than the rotation speed of the motor 10. Although the transmissions T1 and T2 have two stages, they may have one or more stages. Furthermore, an additional transmission may be installed at the end of the output shaft 13.

[0014] <Basic Configuration of SEA> FIG. 2 is a schematic diagram for explaining the basic operation of the SEA applied to the actuator 1 of the first embodiment. As shown in FIG. 2, the SEA 2 is composed of a motor 20, a spring 21, and a load (weight) 22 connected coaxially. When the motor 20 has back-drivability, the moment of inertia I m [kgm 2 of the rotating part of the motor 20, the moment of inertia I l [kgm 2 of the load 22, and the spring constant k [Nm / rad] of the spring 21 are used, the natural frequency f is expressed by Equation (1). Also, when I m <<I l or when the load 22 is considered fixed until it starts to move, the natural frequency f is expressed by Equation (2).

[0015]

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[0016]

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[0017] When the motor 20 has back-drivability and the load 22 does not move, the natural frequency f depends on the moment of inertia of the motor 20. Generally, since the moment of inertia of the motor 20 is small, the natural frequency is high, and the time for continuously outputting torque in one direction is short.

[0018] By attaching the load (weight) 22 coaxially with the rotation axis of the motor 20, the natural frequency f of the SEA 2 with a fixed load 22 and back-drivability of the motor 20 can be reduced. Since the moment of inertia of the load 22 and the rotating part of the motor 20 can be added, the moment of inertia I m in Equation (2) will increase. As a result, the time for the SEA 2 to output torque in one direction can be extended.

[0019] In Fig. 1, the apparent moment of inertia can be increased by increasing the speed of weight 11 as viewed from spring 12. In the first embodiment, as shown in Fig. 1, weight 11 is placed at a position where the rotation speed of motor 10 is increased by transmissions T1 and T2, and spring 12 is placed coaxially with the rotation axis of motor 10 (at the same speed). Since the moment of inertia of motor 10 is smaller than the moment of inertia of weight 11, the natural frequency f of actuator 1 is expressed by equation (3) regardless of the position of motor 10. The moment of inertia I of weight 11 is i [kgm 2 ], the reduction ratio by transmission T1 is 1 / D1, and the reduction ratio by transmission T2 is 1 / D2. By increasing the speed of weight 11, the natural frequency f of actuator 1 can be effectively reduced.

[0020]

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[0021] Maximum allowable angle θ of spring 21 kmax When the spring vibrates at the angle θ k is expressed by the formula (4). The speed θ' of the spring 21 on the side of the motor 20 or the load (weight) 22 is expressed by the formula (5), and the maximum speed θ' kmax is expressed by equation (6).

[0022]

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[0023]

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[0024]

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[0025] The maximum speed θ′ of the motor 10 in the actuator 1 shown in FIG. mmax is the maximum velocity θ' of the spring 12 kmaxIt is expressed by the formula (7) using

[0026]

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[0027] From this, it can be seen that in this embodiment, the maximum speed of the motor 10 is equal to the maximum speed of the spring 12. The torque τ applied to the spring 12 is expressed by equation (8) using the motor torque τm in the case of the actuator 1 shown in FIG.

[0028]

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[0029] In the actuator 1 shown in FIG. 1, the rotation of the motor 10 is transmitted to the output shaft 13 via the spring 12. The rotation of the motor 10 simultaneously rotates the weight 11 via the transmissions T1 and T2. At this time, the rotation speed of the motor 10 and the spring 12 is less than the rotation speed of the weight 11. If the torque of the output shaft 13 does not reach the torque required to rotate the load, a sensor (not shown) detects that the rotation of the output shaft 13 has stopped, and the rotation direction of the motor 10 is reversed. By repeating this motion, the mechanical energy of the weight 11 increases, a large amount of energy is accumulated in the spring 12, and the torque of the output shaft 13 increases.

[0030] In this way, with actuator 1, the rotation speed of weight 11 is increased when viewed from spring 12, so the apparent moment of inertia can be increased, and increasing the rotation speed of weight 11 can effectively lower the natural frequency f of actuator 1. Furthermore, when increasing the rotation speed of weight 11, the rotation speed of motor 10 can be kept low, reducing loss due to back electromotive force.

[0031] According to the first embodiment described above, it is possible to obtain a large inertia even with a relatively small weight 11, thereby increasing the output torque and lowering the natural frequency, thereby reducing the weight and size of the actuator 1. Furthermore, the rotation speed of the motor 10 is kept lower than the inertial speed of the weight 11, thereby reducing loss due to the resistance of the motor 10.

[0032] B. Second embodiment FIG. 3 is a schematic diagram showing the configuration of an actuator according to a second embodiment of the present invention. As shown in FIG. 3, the actuator 3 comprises a motor 30, a weight 31 (inertia), a first transmission T3, a second transmission T4, a spring (elastic body) 32, and an output shaft 33. The rotating shaft of the motor 30 is connected to the low-speed input shaft of the first transmission T3. The rotating shaft (center shaft) of the weight 31 is connected to the high-speed output shaft of the first transmission T3. The rotating shaft of the motor 30 is further connected to the high-speed input shaft of the second transmission T4, and one end of the spring 32 is connected to the low-speed output shaft of the second transmission T4. The other end of the spring 32 is connected to the output shaft 33. As shown in FIG. 3, in this embodiment, the rotating shaft of the motor 30, the low-speed input shaft of the first transmission T3, and the high-speed input shaft of the second transmission T4 are configured as a single shaft.

[0033] As described above, in the second embodiment, similarly to the first embodiment, the rotation shaft of the motor 30 and the rotation shaft of the weight 31 (Inertia) are separated, and a first transmission T3 is disposed so as to transmit rotation via gears. The speed ratio (gear ratio) of the first transmission T3 is set so that the rotation speed of the weight 31 is greater than the rotation speed of the motor 30. Furthermore, in the second embodiment, the rotation shaft of the motor 30 and the rotation shaft of the spring 32 are separated, and a second transmission T4 is disposed so as to transmit rotation via gears. The speed ratio (gear ratio) of the second transmission T4 is set so that the rotation speed of the output shaft 33 is less than the rotation speed of the motor 30. Maximum speed θ' of the motor 30 of the actuator 3 according to the second embodiment mmax is expressed by the following equation (9): In this case, the reduction ratio of the second transmission T4 is 1 / D2.

[0034]

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[0035] From this, it can be seen that, unlike the first embodiment, the spring 32 is driven via the second transmission T4, and therefore the maximum speed of the motor 30 is faster than the maximum speed of the spring 32. The torque τ applied to the spring 32 is expressed by equation (10) using the motor torque τm in the case of the actuator 3 shown in FIG.

[0036]

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[0037] In this way, the actuator 3 according to the second embodiment can increase the speed of the weight 31 while preventing the effects of viscous resistance and back electromotive force due to the speed of the motor 30 and preventing the motor 30 from rotating at a speed exceeding the no-load rotation speed. This can be said to be a well-balanced arrangement that can reduce the effects of resistance due to the rotation speed while outputting motor torque to the spring 32. Note that a further transmission may be installed at the end of the output shaft 33.

[0038] In the actuator 3 shown in FIG. 3, the rotation of the motor 30 increases in torque via the second transmission T4 and is transmitted to the output shaft 33 via the spring 32. The rotation of the motor 30 simultaneously rotates the weight 31 via the first transmission T3. At this time, the rotation speed of the motor 30 and the spring 32 is less than the rotation speed of the weight 31. If the torque of the output shaft 33 does not reach the torque required to rotate the load, a sensor (not shown) detects that the rotation of the output shaft 33 has stopped, and the rotation direction of the motor 30 is reversed. By repeating this motion, the mechanical energy of the weight 31 increases, a large amount of energy is accumulated in the spring 32, and the torque of the output shaft 33 increases.

[0039] In this way, with actuator 3, the rotation of weight 31 is accelerated relative to spring 32, so the apparent moment of inertia can be increased by the square of the speed-up ratio of first transmission T3, and by increasing the rotation of weight 31, the natural frequency f of actuator 3 can be effectively lowered. Furthermore, when increasing the rotation of weight 31, the rotation speed of motor 30 can be kept low, reducing loss due to back electromotive force. Furthermore, the increased torque is transmitted to spring 32 by second transmission T4, so that spring 32 can be excited efficiently in a short time even with a small motor torque.

[0040] According to the second embodiment described above, in addition to the effects of the first embodiment, it is possible to perform excitation with lower torque by reducing the speed with the second transmission T4. This allows excitation to be performed in a shorter time. Furthermore, the rotation speed of the motor 30, the rotation speed of the weight 31, and the rotation speed of the output shaft 33 can be freely designed by changing the speed ratio (gear ratio) of the first transmission T3 and the second transmission T4. Furthermore, an optimal design can be achieved according to the natural frequency of the application.

[0041] C. Application Examples As an application example of the actuator 3 according to the second embodiment described above, a rocker bogie car 4 using the actuator 3 as a driving force will be described. Figure 4 is a schematic diagram for explaining the operation of the rocker bogie car 4 using the actuator 3 according to the present invention. The rocker bogie car 4 shown in Figure 4 has a left-right symmetrical link configuration and forms a six-wheeled rocker bogie car body. The rocker bogie car 4 is equipped with rocker links 41R, 41L, bogie links 42R, 42L, and link angle actuators 43R, 43L on the left and right sides of the main body.

[0042] The rocker bogie car 4 can independently drive and control six wheels, namely, a right front wheel 40Rf, a left front wheel 40Lf, a right center wheel 40Rm, a left center wheel 40Lm, a right rear wheel 40Rr, and a left rear wheel 40Lr, by using wheel actuators (not shown). By controlling the rotation of these six wheels as forward or reverse, the rocker bogie car 4 can travel forward, backward, sideways, diagonally, or in a spin turn.

[0043] In addition, since the center of gravity of the rocker bogie car 4 is on the bogie links 42R and 42L side, the left and right link angle actuators 43R and 43L lift the left and right rocker links 41R and 41L to overcome steps. Also, if the center of gravity is on the rocker links 41R and 41L side, it is possible to lift the wheels of the bogie links 42R and 42L that are not on the rocker links 41R and 41L side.

[0044] 5(a) to 5(f) are schematic diagrams for explaining the operation (going over a step) of a rocker bogie vehicle 4 using an actuator 3 according to the present invention. The diameter of the wheels of the rocker bogie vehicle 4 is 100 mm, and the height of the step is 95 mm. Since there are no vertical plates, this is a step that a rocker bogie, which does not have power in its joints, cannot traverse.

[0045] As shown in FIG. 5(a), when the rocker bogie vehicle 4 detects a step ahead using a sensor (not shown), the motors (corresponding to motor 30 in FIG. 3) of the link angle actuators 43 (left link angle actuator 43L and right link angle actuator 43R) are rotated to lift the front wheels 40f (front wheels 40Lf, 40Rf), as shown in FIG. 5(b). This causes the springs (corresponding to spring 32 in FIG. 3) to deform due to inertia, and elastic energy is accumulated. When elastic energy is accumulated in the link angle actuators 40, the rocker links 41 (rocker links 41R, 41L) swing up, and as shown in FIG. 5(b), the front wheels 40f are lifted.

[0046] When the rocker link 41 rotates and the front wheel 40f is lifted, the wheels 40m, 40r (middle right wheel 40Rm, middle left wheel 40Lm, rear right wheel 40Rr, and rear left wheel 40Lr) of the bogie link 42 (bogie links 42R, 42L) are driven forward by an actuator (not shown) as shown in FIG. 5(c). When the front wheel 40f moves onto the step, the motor of the link angle actuator 43 is reversed, causing the front wheel 40f to touch the step. When the front wheel 40f touches the step, the spring in the link angle actuator 43 is significantly deformed due to inertia. This spring deformation accumulates elastic energy in the spring, and as shown in FIG. 5(d), the middle wheel 40m (middle right wheel 40Rm, middle left wheel 40Lm) is lifted, causing the front wheel 40f and rear wheel 40r to be driven forward by an actuator (not shown). This allows the middle wheel 40m to overcome the step, as shown in Figure 5(e).

[0047] After the middle wheel 40m has run over the step, as shown in Figure 5(f), if the motor of the link angle actuator 43 is further rotated, the spring in the link angle actuator 43 will be significantly deformed due to inertia. This deformation of the spring accumulates elastic energy in the spring, and the accumulated elastic energy generates torque that rotates the bogie link 42 relative to the rocker link 41, and this torque assists the rear wheel 40r in running over the step.

[0048] In the above-described application example, by applying the actuator 3 according to the second embodiment to the rocker link 41 as a driving force, the moment of inertia of the weight 31 can be increased by the square of the speed-up ratio of the transmission T3, and by lowering the natural frequency f, the rocker link 41 swinging action to increase the mechanical energy of the rocker bogie car 4 can be slowed down. This makes it easier to control the timing of climbing over a step, which would be difficult with a fast swinging action. In addition, the rocker link 41 can be rotated with a small torque, allowing the motor 30 that rotates the rocker link 41 to be made smaller.

[0049] In addition to this, the present invention is not limited to the above-mentioned embodiments and each modified example described with reference to the drawings, and it is possible to select and discard the configurations listed in the above-mentioned embodiments and each modified example, or to change them to other configurations as appropriate, as long as this does not deviate from the gist of the present invention. [Explanation of symbols]

[0050] 1, 3 Actuator 10, 30 motor 11, 31 Weight (inertial body) 12, 32 Spring (elastic body) 13, 33 Output shaft T1~T4 gearbox

Claims

1. A motor; an elastic body connected to a rotation shaft of the motor; an output shaft connected to the elastic body; an inertial body having a central axis; a transmission; An actuator, characterized in that a rotating shaft of the motor is connected to a low-speed input shaft of the transmission, and a central axis of the inertial body is connected to a high-speed output shaft of the transmission.

2. A motor; An elastic body; an output shaft connected to the elastic body; an inertial body having a central axis; a first transmission; a second transmission; a rotating shaft of the motor is connected to a low-speed input shaft of the first transmission, and a central axis of the inertial body is connected to a high-speed output shaft of the first transmission, an actuator, wherein a rotating shaft of the motor is connected to a high-speed input shaft of the second transmission, and the elastic body is connected to a low-speed output shaft of the second transmission.

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