JP6601873B2 - Overload protection device - Google Patents

Description

  The present invention relates to an overload protection device that transmits a driving force from a driving source to a driving target while cutting the driving target when an excessive load is applied to the driving target.

  Conventionally, Patent Document 1 discloses an overload protection device that interrupts rotation transmission when an overload occurs in a rotation transmission mechanism. The overload protection device includes an input-side hub, an output-side center flange that holds steel balls in a plurality of through-holes provided in the axial direction of the hub, and a center flange that faces the axial direction, A hub flange having a conical recess that engages with the steel ball and a pressing plate that presses the steel ball in the hub flange direction by a spring are provided. During normal rotation transmission, the rotation of the hub is transmitted to the center flange via the steel ball, but when the center flange is overloaded, the steel ball moves against the spring force and disengages from the recess in the hub flange. The rotation to the center flange is blocked, and an excessive load is prevented from being transmitted.

JP 2009-257404 A

In the above-described conventional overload protection device, a frictional force is generated for transmitting rotation during normal rotation transmission below the set torque, and slipping occurs due to relative rotation of the connecting member between the drive source and the drive target during overload. Regardless of the set torque range, the frictional contact member wears out and is subject to deterioration over time.
Therefore, an object of the present invention is to provide an overload protection device that avoids frictional contact between members and has a long product life.

In order to solve the above-described problems, in the present invention, the overload protection device 1 that receives the driving force from the driving source and transmits the driving force to the driving target while restricting the transmission of the excessive load from the driving target to the driving source is driven. It is interposed between the source and the driven object. The overload protection device 1 includes a flywheel 3 that is rotatably supported connected to one of a drive source and a drive target, and a flywheel 3 that is connected to the other of the drive source and the drive target and that has a gap between the flywheel 3. This is accommodated to form a sealed region 12, and includes a flywheel 3 and a casing 4 supported so as to be relatively rotatable. A magnetorheological fluid 7 whose viscosity hardness is increased by application of the magnetic field M is enclosed in a sealed region of the casing 4. With the flywheel 3 and the casing 4 as a part of the magnetic circuit, the magnets 5 and 6 that form the magnetic field M in the gap between the flywheel 3 and the casing 4 in the sealed region 12 are fixed to the casing 4 or the flywheel 3. The magnetic force M applied by the magnets 5 and 6 gives the viscous resistance of the magnetorheological fluid viscosity 7 to the rotation of the casing 4 or the flywheel 3, and the casing 4 and the flywheel 3 are rotated integrally, thereby driving force. On the other hand, the transmission of the load is limited by rotating the casing 4 and the flywheel 3 relative to each other by an excessive load that overcomes the viscous resistance.
The flywheel 3 includes a rotating shaft member 2 that is connected to a driving source and is rotatably supported to receive a driving force. The casing 4 is connected to a drive target and is rotatably supported integrally therewith.
The magnets 5 and 6 are fixed at positions facing the flywheel in the axial direction of the casing.
The magnet 6 is mounted on the casing such that the fixed position can be changed.

  Since the apparatus of the present invention intervenes a magnetorheological fluid between the drive source side and the load side, there is no frictional contact between members, and wear can be avoided, so that the product life can be extended. it can.

1 is a schematic cross-sectional view of an overload protection device according to the present invention. It is explanatory drawing of the magnetic circuit of the overload protection apparatus of FIG. It is explanatory drawing of the magnetic circuit of the overload protection apparatus which concerns on other embodiment. It is a graph which shows the relationship of the rotational torque with respect to the rotational speed of the overload protection apparatus of FIG. It is a graph which shows the relationship of the rotational torque with respect to the fixed position of the movable magnet of the overload protection apparatus of FIG.

Embodiments of the present invention will be described with reference to the drawings.
In FIG. 1, an overload protection device 1 according to the present invention is interposed between a drive source (not shown) and a drive target that receives this drive force. The overload protection device 1 includes a rotary shaft member 2 connected to a drive source, a flywheel 3 key-coupled on the rotary shaft member 2, and a drive target. A casing 4 for housing the wheel 3, magnets 5 and 6 fixed to the casing 4, and a magnetorheological fluid 7 filled and enclosed in the casing 4 are provided.

  The rotary shaft member 2 is rotatably supported relative to the casing 4 with a small diameter portion 2a at one end connected to a drive source at the front bearing 8 of the casing 4 and at the other end 2c with a large diameter portion at the bearing 9. Is done. An intermediate portion of the rotating shaft member 2 is provided with a truncated cone-shaped coupling portion 2c that couples the flywheel 3 with a key.

  The flywheel 3 is made of a disk-like magnetic material or nonmagnetic material, and the center is fixed to the coupling portion 2 c of the rotary shaft member 2.

  The casing 4 includes a connecting portion 13 connected to a driving target at one end, and can rotate integrally with the driving target to which the driving force is transmitted. The casing 4 is made of a substantially cylindrical magnetic material, and accommodates the flywheel 3 with a gap formed from the inner wall. A sealed region 12 is formed between the casing 4, the flywheel 3, and the rotary shaft member 2 by the sealing materials 10 and 11 on the rotary shaft member 2.

  A fixed magnet 5 and a movable magnet 6 made of a coaxial ring-shaped permanent magnet material are fixed to both end walls of the casing 4 so as to face each other. The fixed magnet 5 and the movable magnet 6 form a magnetic field M across the sealed region 12 using the casing 4 and the flywheel 3 as a magnetic circuit. The movable magnet 6 is held by a holder that is screwed into the casing 4, and is fixed so that its position can be changed in the axial direction.

  The magnetorheological fluid 7 is filled and sealed in the sealed region 12. The magnetorheological fluid 7 has its viscosity hardness increased by the magnetic field M generated by the fixed magnet 5 and the movable magnet 6, and a resistance force such as a larger frictional force than normal is generated against the rotation of the flywheel 3. By rotating integrally with the wheel 3, the driving force of the driving source is transmitted to the casing 4. The magnetorheological fluid 7 generates a certain resistance force against the flywheel 3, but if the load to be driven to which the driving force is transmitted is excessive, the resistance force due to the viscous hardness is overcome, and the casing 4 becomes the flywheel. 3 cannot be followed, and the relative driving force limits the transmitted driving force. The maximum load that can be transmitted can be set by adjusting the strength of the magnetic field M according to the relative position of the movable magnet 6 with respect to the fixed magnet 5 and adjusting the viscous hardness of the magnetorheological fluid 7.

  In this overload protection device 1, when the flywheel 3 is made of a magnetic material, as shown in FIG. 2, the sealed region 12 having the casing 4 and the flywheel 3 as a magnetic circuit is formed by the fixed magnet 5 and the movable magnet 6. A transverse magnetic field M is formed, thereby increasing the viscosity hardness of the magnetorheological fluid 7, the casing 4 rotates integrally with the flywheel 3, and the driving force of the driving source connected to the rotating shaft member 2 is changed to the casing 4. Is transmitted to the drive target connected to the. At this time, as shown in FIG. 4, as the rotational speed of the rotary shaft member 2 connected to the drive source increases, the rotational torque that can be transmitted to the casing 4 connected to the drive target decreases. In the range of the load that can be transmitted, the wheel 3 and the casing 4 rotate integrally with the driving force being transmitted to the driving target and the driving source is loaded. If this load becomes excessive, the magnetorheological fluid 7 Thus, the flywheel 3 is rotated in an idling state in which it rotates relative to the casing 4, and the driving force transmitted to the casing 4 is limited, thereby avoiding an excessive burden on the driving source. Since the viscosity hardness of the magnetorheological fluid 7 changes according to the strength of the magnetic field M, the rotational torque of the driving force can be changed by changing the relative fixing position of the movable magnet 6 with respect to the fixed magnet 5 as shown in FIG. As a result, the maximum load that can be transmitted can be set.

  When the flywheel 3 is made of a magnetic material, the fixed magnet 5 and the movable magnet 6 uniformly form a magnetic field M in the axial direction of the flywheel 3 between the magnets 5 and 6, as shown in FIG. As a result, the viscous hardness of the magnetorheological fluid 7 increases, the casing 4 rotates integrally with the flywheel 3, and the driving force of the driving source connected to the rotating shaft member 2 is transmitted to the driving target connected to the casing 4. If the load to be driven becomes excessive, the driving force applied to the casing 4 is limited, and an excessive load on the driving source is avoided.

The magnets 5 and 6 may be electromagnets instead of permanent magnets. In this case, by increasing or decreasing the coil current, the magnetic field strength M can be adjusted to adjust the limit of the driving force to be transmitted.
In addition, a mechanism for removing the driving force instantaneously can be provided by a mechanism for removing the magnet when using a permanent magnet, or by means for interrupting current to the coil when using an electromagnet.

DESCRIPTION OF SYMBOLS 1 Overload protective device 2 Rotating shaft member 3 Flywheel 4 Casing 5 Fixed magnet 6 Movable magnet 7 Magnetorheological fluid 8 Bearing 9 Bearing 10 Sealing material 11 Sealing material 12 Sealing area M Magnetic field

Claims (3)

In the overload protection device that receives the driving force from the driving source and transmits the driving force to the driving target while limiting the transmission of the overload from the driving target to the driving source,
A freely supported flywheel connected to one of the drive source or drive target;
A casing that is connected to the other of the drive source or the drive target, and that contains a gap between the flywheel and accommodates it to form a sealed region, and is supported to be relatively rotatable with the flywheel;
A magnetorheological fluid enclosed in a sealed region of the casing and whose viscosity hardness is increased by application of a magnetic field;
So as to form a magnetic field in the gap between the flywheel and the flywheel and the casing of the sealed area of the casing as a part of the magnetic circuit, it is detachably fixed to the casings grayed, and fixed so as to adjust the intensity of the magnetic field position Ru is changeably mounted; and a magnet,
The magnetic field applied by the magnet gives the viscous resistance of the magnetorheological fluid to the rotation of the casing or the flywheel, and transmits the driving force by rotating the casing and the flywheel integrally, while the viscous resistance is reduced. An overload protection device that limits transmission of a load by rotating a casing and a flywheel relative to each other by an overload to overcome. The flywheel includes a rotating shaft member that is connected to the driving source and is rotatably supported to receive a driving force,
2. The overload protection device according to claim 1, wherein the casing is connected to the drive target and is rotatably supported by the rotary shaft member . 3. The overload protection device according to claim 1, wherein the magnet is fixed to a facing position of the casing that sandwiches the flywheel in an axial direction so that a mutual interval can be changed .

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