JP7482450B2 - Torque limiter - Google Patents

Description

The present invention relates to a torque limiter.

In rehabilitation settings for people with disabilities, such as paralysis, walking motion assist devices are used to correct the walking motion of the patient so that it is closer to that of a healthy person. For example, the walking motion assist devices in Patent Documents 1 and 2 are attached to the paralyzed leg and assist the plantar flexion and dorsiflexion of the ankle joint through the power of a motor.

During walking training using a walking movement assist device, some factor may cause a force in the dorsiflexion direction to be applied to the patient's ankle joint during the assist movement of plantar flexing the patient's ankle joint. In such a case, a load greater than the rated load is applied to the motor, causing an overload current to flow through the motor, which may cause the motor to break down.

In fields that use motors, such as industrial machinery, a wide variety of torque limiters have been proposed to prevent motor failure due to overload, including those that use springs (e.g., Patent Document 3) and those that use magnetic force (e.g., Patent Document 4).

JP 2017-217039 A JP 2015-58033 A JP 2015-137732 A JP 2002-295510 A

Although a wide variety of torque limiters have been proposed to date, none of them can be said to be suitable for use in human movement assistance devices such as walking assistance devices.

The present invention was made in consideration of the above, and its purpose is to provide a torque limiter with a simple configuration that can also be applied to human body movement assistance devices, etc.

The torque limiter according to the present invention comprises:
An input side part that is directly or indirectly connected to an output shaft of a motor and rotates when driven by the motor;
An output side part that is stacked on the input side part and attached to an object to be attached;
a damping member sandwiched between the input side part and the output side part in a stacking direction of the input side part and the output side part;
a pair of elastic members disposed on a circumference in a rotational direction of the input side part and sandwiched between the input side part and the output side part,
the input side part and the output side part are arranged to be relatively rotatable about a rotation axis of the input side part,
The damping member is disposed on a circumference about the rotation axis,
The pair of elastic members are arranged apart from each other on concentric circles about the rotation shaft,
When the motor is not overloaded, the input side part and the output side part rotate integrally by the damping member and the pair of elastic members, whereas when the motor is overloaded, one of the elastic members contracts and the other elastic member expands, thereby allowing relative rotation between the output side part and the input side part.
It is characterized by:

The damping member may also be an annular member.

The elastic member may be a coil spring.

Moreover, the input side part and the output side part are connected by a fastening member installed along the rotation axis,
A spacer may be provided to keep the fastening member at a constant tightness.

The fastening member may also include a shim that maintains constant the distance between the input part and the output part, and the frictional force between the input part and the output part and the damping member.

The present invention provides a torque limiter with a simple configuration that can be used in devices such as human body movement assistance devices.

FIG. 2 is an external perspective view of a torque limiter. This is a cross-sectional view of A-A' in Figure 1. FIG. 2 is an exploded perspective view of the torque limiter. FIG. 13 is a diagram showing a walking motion assist device equipped with a torque limiter. FIG. 13 is a diagram showing a state in which the torque limiter is attached to the walking movement assist device. This is a cross-sectional view of A-A' in Figure 5. FIG. 11 is a diagram illustrating the operation of the torque limiter when no overload is applied. 11A and 11B are diagrams illustrating the operation of the torque limiter in an overloaded state.

The torque limiter according to this embodiment will be described with reference to the figures. As shown in Figs. 1 to 3, the torque limiter 1 includes an input part 10, an output part 20, a damping member 30, elastic members 40 and 41, a bolt 50, a nut 51, a spacer 52, and a shim 53.

The input part 10 is a part that is directly or indirectly connected to the output shaft of the motor and rotates as the motor is driven. The input part 10 has a disk-shaped outer surface with a portion (approximately 30-40%) of the outer surface protruding outward. The ends of this protruding portion have elastic member fixing portions 11a, 11b. A through hole 12 of approximately the same size as the outer diameter of the spacer 52 is formed in the center of the input part 10, and a groove with a diameter larger than the outer diameter of the spacer 52 is formed around the through hole 12. In addition, the disk-shaped portion of the input part 10 is formed with an annular damping member placement groove 13 in which the damping member 30 is placed. In addition, the disk-shaped portion of the input part 10 is formed with a bolt hole 14 for fixing a connecting member that connects to the output shaft of the motor.

The output part 20 is a part that is attached to an object to which it is attached, and the object to which it is attached rotates as the output part 20 rotates. The output part 20 has a shape similar to that of the input part 10. As with the input part 10, the protruding portion of the disk-shaped outer periphery has elastic member fixing portions 21a, 21b at each end. A through hole 22 is formed in the center of the output part 20, and a groove 23 is formed around it. A ring-shaped damping member placement groove (not shown) in which the damping member 30 is placed is formed in the disk-shaped portion. A bolt hole 24 is formed in the disk-shaped portion of the output part 20 to fix it to the object to which it is attached.

The input side part 10 and the output side part 20 are connected by fastening members, a bolt 50 and a nut 51. Specifically, a cylindrical spacer 52 is inserted into the through holes 12, 22 of the input side part 10 and the output side part 20, and then a bolt 50 is inserted into the spacer 52 and fastened with a nut 51 via an annular shim 53. The input side part 10 and the output side part 20 are stacked with their respective disk-shaped portions facing each other, and are configured to be relatively rotatable around the bolt 50 and spacer 52 as the rotation axis.

The damping member 30 is sandwiched between the input side part 10 and the output side part 20 in the stacking direction so as to fit into the damping member placement groove 13 of the input side part 10 and the output side part 20. The damping member 30 is an annular body with a circular cross section, and is placed on a circumference centered on the rotation axis. The damping member 30 is, for example, a rubber O-ring with a circular cross section. As described below, the damping member 30 has the function of rotating the input side part 10 and the output side part 20 as a single unit by frictional force, and the function of damping the movement of the input side part 10 and the output side part 20 to return to their original positions when the input side part 10 and the output side part 20 rotate relative to each other.

Here, the elastic members 40, 41 are coil springs 40, 41. The coil springs 40, 41 are arranged spaced apart on a circumference centered on the rotation axis, sandwiched between the protruding portions of the input side part 10 and the output side part 20. One end of the coil spring 40 is fixed to the elastic member fixing portion 11a of the input side part 10, and the other end is fixed to the elastic member fixing portion 21a of the output side part 20. One end of the coil spring 41 is fixed to the elastic member fixing portion 11b of the input side part 10, and the other end is fixed to the elastic member fixing portion 21b of the output side part 20. The coil springs 40, 41 have the same length and spring constant.

Next, the operation of the torque limiter 1 will be described using an example in which the torque limiter 1 is applied to a walking motion assist device 60 shown in FIG. 4. This walking motion assist device 60 is a device used for walking training by patients who have difficulty walking on their own, such as patients with one-leg paralysis. The walking motion assist device 60 assists plantar flexion and dorsiflexion of the foot with a motor and a drive mechanism.

The walking motion assist device 60 comprises a shoe-shaped foot brace 61 into which the foot is inserted and fixed, a shin fixing member 62 that fixes the lower part of the knee, a shin frame 63 fixed to the shin fixing member 62, a foot frame 64 fixed to the foot brace 61, and a housing box 65 that houses a motor, a drive mechanism, and a torque limiter 1. The walking motion assist device 60 comprises a control device and a power supply source (not shown), and is driven by instructions from the control device.

The installation state of the torque limiter inside the storage box 65 is shown in Figures 5 and 6. The torque limiter 1 is installed so that its rotation axis is coaxial with the axis of the ankle joint.

The input side part 10 is fixed to the connecting member 72 with a bolt 73. The connecting member 72 is also fixed to the output shaft 71 of the motor 70, and the motor 70 is fixed so that its relative position to the shin frame 63 does not change. The output shaft 71 of the motor 70 and the rotation shaft of the connecting member 72 are coaxial with the rotation shaft of the torque limiter 1. The connecting member 72 and the input side part 10 rotate as the motor 70 is driven.

The output part 20 is fixed to the attachment object, the foot frame 64, with bolts 74, so that the foot frame 64 rotates as the output part 20 rotates.

Figure 7 shows the movement of the walking motion assist device 60 when assisting plantar flexion or dorsiflexion of the ankle joint and the motor 70 is not overloaded. When the motor 70 is driven and the output shaft 71 and the connecting member 72 rotate clockwise on the page, the input side part 10 fixed to the connecting member 72 also rotates clockwise.

When there is no overload, the input side part 10 and the output side part 20 move together due to the frictional force between the damping member 30 and the input side part 10 and the output side part 20, and the biasing force of the springs 40, 41. As a result, the output side part 20 also rotates together with the input side part 10, and the foot frame 64 fixed to the output side part 20 rotates, assisting the plantar flexion or dorsiflexion movement.

On the other hand, Figure 8 shows the movement of the motor 70 when it is overloaded while the walking motion assist device 60 is assisting plantar flexion or dorsiflexion of the ankle joint. There are various situations in which the motor 70 can be overloaded, such as when the patient's knee bends and a force that dorsiflexes the ankle joint is applied while assisting plantar flexion when the patient's toes are off the ground. In this way, the motor 70 can be overloaded when a large force that causes dorsiflexion is applied while assisting plantar flexion, or when a large force that causes plantar flexion is applied while assisting dorsiflexion.

When an overload is applied to the motor 70, the input part 10 is allowed to rotate relative to the output part 20 against the frictional force of the damping member 30 and the biasing force of the coil spring 41. This prevents damage to the motor 70 due to an overload.

After the overload subsides, the restoring forces of the contracted coil spring 40 and the expanded coil spring 41 act, causing the input part 10 and the output part 20 to return to their original positions. At this time, the damping force of the damping member 30 acts, and in addition to causing a sudden return to the original positions, damping caused by the repeated contraction and expansion of the coil springs 40 and 41 is also suppressed.

If the input part 10 and the output part 20 suddenly return to their original positions or if damping occurs, this can hinder the patient's efficient walking training. However, even with a simple configuration, the torque limiter 1 can prevent damage to the motor 70 due to overload and also contributes to efficient walking training.

In addition, the walking movement assist device 60 can perform steep angle control operations because the motor 70 continuously rotates forward and backward to assist the ankle joint from plantar flexion to dorsiflexion and back again. Such a steep change in rotation direction can easily give the patient undergoing walking training the feeling that they are being controlled by the device, which can discourage them from continuing walking training.

Even with a steep angle control operation, the torque limiter 1 rotates the input part 10 slightly relative to the output part 20, and then the output part 20 and the input part 10 return to their original positions while attenuating, so the patient's motivation for walking training is not diminished, leading to more effective walking training.

The above describes an example in which the torque limiter 1 is applied to a walking motion assist device 60 that assists plantar flexion and dorsiflexion of the ankle joint, but the torque limiter 1 can also be applied to motion assist devices that assist the movements of the knee joint, elbow joint, etc., as well as various industrial machines, etc.

The fastening of the bolt 50 and nut 51 is regulated by the length of the spacer 52. Therefore, regardless of which user fastens the bolt 50 and nut 51, the degree of fastening is constant, i.e., the distance between the head of the bolt 50 and the nut 51 is constant.

Then, the thickness of the shim 53 (D shown in FIG. 2) allows the interval (W shown in FIG. 2) between the input side part 10 and the output side part 20 to be adjusted. When the interval between the input side part 10 and the output side part 20 is narrowed by using a thick shim 53, the pressing force of the input side part 10 and the output side part 20 on the damping member 30 becomes relatively strong, so the frictional force between the input side part 10 and the output side part 20 and the damping member 30 can be increased. When the interval between the input side part 10 and the output side part 20 is widened by using a thin shim 53, the pressing force of the input side part 10 and the output side part 20 on the damping member 30 becomes relatively weak, so the frictional force between the input side part 10 and the output side part 20 and the damping member 30 can be reduced. Thus, by changing the thickness of the shim 53, it is possible to respond to the rating of the motor 70 used, the application form of the torque limiter 1, etc. It is to be noted that the same thing can be achieved by preparing multiple shims 53 and changing the number of shims 53 used.

Coil springs 40, 41 with different spring constants may also be used. As long as the damping member 30 performs the above-mentioned functions, there are no limitations on its shape, and it may be an annular body with a rectangular or other cross-section, or multiple spherical or cubic shapes arranged on concentric circles.

REFERENCE SIGNS LIST 1 Torque limiter 10 Input side part 11a, 11b Elastic member fixing portion 12 Through hole 13 Groove for disposing damping member 14 Bolt hole 20 Output side part 21a, 21b Elastic member fixing portion 22 Through hole 23 Groove 24 Bolt hole 30 Damping member 40, 41 Elastic member (coil spring)
50 Bolt 51 Nut 52 Spacer 53 Shim 60 Walking motion assist device 61 Foot brace 62 Shin fixing member 63 Shin frame 64 Foot frame 65 Storage box 70 Motor 71 Output shaft 72 Connecting member 73 Bolt 74 Bolt

Claims (5)

An input side part that is directly or indirectly connected to an output shaft of a motor and rotates when driven by the motor;
An output side part that is stacked on the input side part and attached to an object to be attached;
a damping member sandwiched between the input side part and the output side part in a stacking direction of the input side part and the output side part;
a pair of elastic members disposed on a circumference in a rotational direction of the input side part and sandwiched between the input side part and the output side part,
the input side part and the output side part are arranged to be relatively rotatable about a rotation axis of the input side part,
The damping member is disposed on a circumference about the rotation axis,
The pair of elastic members are arranged apart from each other on concentric circles about the rotation shaft,
When the motor is not overloaded, the input side part and the output side part rotate integrally by the damping member and the pair of elastic members, whereas when the motor is overloaded, one of the elastic members contracts and the other elastic member expands, thereby allowing relative rotation between the output side part and the input side part.
A torque limiter characterized by: The damping member is an annular body.
2. The torque limiter according to claim 1 . The elastic member is a coil spring.
3. The torque limiter according to claim 1 or 2. the input part and the output part are connected by a fastening member installed along the rotation axis,
A spacer is provided to keep the fastening member at a constant tightness.
4. The torque limiter according to claim 1, wherein the torque limiter is a torque limiter having a torque limiting function. The fastening member includes a shim that maintains constant a distance between the input side part and the output side part, and a frictional force between the input side part and the output side part and the damping member.
5. The torque limiter according to claim 4.

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