KR100849661B1 - Mr rotary brake with permanent magnet - Google Patents

Abstract

A rotary MR(Magneto-Rheological) brake having a permanent magnet is provided to allow the rotation speed of a rotation shaft to be maintained in a constant level through controlling an over speed of the rotation shaft based on the MR fluid viscosity. A rotary MR brake having a permanent magnet comprises a housing(20) coupled to one side of a rotation shaft(70) via a bearing(23) and having a hollow portion(21) formed in the housing, an deceleration chamber(22), a guide rod(30), an interrupter member(40), an elastic spring(50), and MR fluid(60). The deceleration chamber, which has a width narrower than that of the hollow portion, is formed along the inner peripheral edge of the housing. The guide rod is horizontally coupled to the rotation shaft to rotate while being adjacent to the inner peripheral edge of the deceleration chamber. The interrupter member is mounted on the guide rod to slide along the guide rod based on a centrifugal force caused by the permanent magnet.

Description

MR rotary brake with permanent magnet

1A is a longitudinal sectional view of an MR brake according to a preferred embodiment of the present invention.

Figure 1b is a partial cross-sectional perspective view of the MR brake according to the present invention.

2 is a cross-sectional view of the control member according to the present invention.

Figure 3 is a longitudinal cross-sectional view of the MR brake according to another embodiment of the present invention.

4 is a cross-sectional view showing an operating state of the MR brake according to the present invention.

Figure 5 is a schematic diagram showing a tension control process of the elastic spring according to the present invention.

Figure 6 is an installation state showing another embodiment according to the present invention.

7 is a plan view showing a 2D model of the MR brake for electromagnetic field analysis.

8A and 8B are electromagnetic field distribution diagrams according to positions of the intermittent members according to the first embodiment.

9A and 9B are graphs showing the magnetic field strength of Example 1;

10A and 10B are graphs showing torque results of Example 1 and Example 2. FIG.

11 is a plan view showing a 2D model of the MR brake for electromagnetic field analysis according to another embodiment of the present invention.

12A and 12B are electromagnetic field distribution diagrams according to positions of the intermittent members according to the third embodiment.

13A and 13B are graphs showing the magnetic field strength of Example 3;

14A and 14B are graphs showing torque results of Examples 3 and 4. FIG.

15 is a graph showing the torque results of Examples 1 to 4 according to the present invention.

<Explanation of symbols for the main parts of the drawings>

10: speed limit device 20: housing

21: hollow part 22: reduction chamber

23: bearing 30: guide rod

40: intermittent member 41: moving member

42: permanent magnet 43: through hole

50: elastic spring 60: MR fluid

70: rotation axis 71: knob

72: locking rod 73: hook member

721: jamming protrusion 731: locking groove

732: incision groove

The present invention relates to a rotary MR brake using a permanent magnet, and more particularly, an intermittent member, which is a permanent magnet, is installed inside the MR brake housing having a deceleration chamber having a narrow space at an inner circumference so as to be movable by centrifugal force. In the case, the inner space of the housing is filled with MR fluid having excellent reaction speed by the magnetic field, and the intermittent member is introduced into the deceleration chamber by the centrifugal force when the rotating shaft, which is a rotor, is over rotated by a certain speed. The MR fluid filled by increasing the magnetic flux density in the gap between the yarns to form a strong magnetic field is related to a rotating MR brake using a permanent magnet that prevents over-rotation of the rotating shaft by changing the viscosity to generate a large resistance torque. .

In general, brakes are divided into caliper disc brakes, disc disk brakes, internal shoe drum brakes, band brakes and extended, retractable brakes. These brakes are operated by mechanical friction and are operated by mechanical, pneumatic, hydraulic or electrical devices. In addition, as described above, in addition to the brake system that obtains braking force by direct mechanical friction, there are brakes that obtain braking force by a medium made of particles, and typically there are powder brakes and brakes using functional fluids.

The powder brake is a brake that acts to generate a friction force by forming a chain-shaped cluster along the magnetic field lines of the magnetic field by the magnetic field applied to generate a friction force, large size for performance and difficult to expect a high-speed response After a certain time of use has a problem that the powder must be replenished. Therefore, in order to follow the responsiveness of the device rotating at high speed with high precision, a device capable of controlling the viscosity change in units of several ms by an applied magnetic field is required rather than the conventional powder brake, and the method developed for this is a brake using a functional fluid. That's the way. In particular, a brake using a magneto- rheological (MR) fluid is a typical method using a functional fluid.

The conventional brake provided using MR fluid is a method of forming and operating a magnetic field around the MR fluid using current flowing through the coil, and has a disadvantage of being difficult to use due to a complicated structure such as installing a coil inside the rotor. .

The present invention has been made to solve the above problems,

According to the strength of the centrifugal force, the intermittent member, which is a permanent magnet, is movably embedded, and the intermittent member is introduced into the narrow reduction chamber by the centrifugal force when the intermittent member is above a certain speed to increase the magnetic flux density of the gap between the intermittent member and the reduction chamber. Rotating MR to maintain the rotational speed below a certain level by equipping one side of the rotating shaft with a device that generates large friction torque by increasing the viscosity of the MR fluid so as to reduce the rotational speed by increasing the viscosity of the MR fluid only when it is over-rotated. To provide a brake.

Rotary MR brake using a permanent magnet according to the present invention for achieving the above object,

A brake mounted on one side of a rotating shaft to limit the rotation speed, the brake comprising: a housing coupled to one side of the rotating shaft and having a hollow portion therein; A reduction chamber formed in a narrower width than the hollow portion along the inner circumference of the housing; A guide rod coupled to the rotation shaft in a vertical direction, the end of the guide rod being rotated close to the inner periphery of the reduction chamber; An intermittent member mounted to the guide rod and slidably moved on the guide rod by centrifugal force; An elastic spring having one end coupled to the intermittent member and the other end coupled to the rotating shaft to limit movement of the intermittent member; It is configured to include; MR fluid is filled in the hollow portion and the reduction chamber inside the housing to change the viscosity by the magnetic field.

The intermittent member is formed as a permanent magnet so that the magnetic flux density increases in the gap between the intermittent member and the deceleration chamber by the magnetic field of the intermittent member when the inflow chamber is introduced by the centrifugal force so that the MR fluid viscosity changes. In addition, the housing may be formed of a magnetic body of the inner portion constituting the deceleration chamber, the portion of the hollow portion may be formed of a non-magnetic material.

In addition, the elastic spring has one end coupled to the intermittent member and the other end is connected to the knob mounted on the end of the rotary shaft through the inside of the rotary shaft to adjust the distance between the knob and the rotary shaft end to adjust the tension of the elastic spring. The guide rod and the intermittent member may be formed to be symmetrical with respect to the rotation axis.

In addition, the hollow part may be a portion that is connected to the reduction chamber to the inclined surface to allow the MR fluid to flow into the reduction chamber without vortex generation.

Hereinafter, the rotary MR brake using the permanent magnet of the present invention as described above will be described in detail with reference to the accompanying drawings.

Figure 1a is a longitudinal cross-sectional view of the MR brake according to a preferred embodiment of the present invention, Figure 1b is a partial cross-sectional perspective view of the MR brake according to the invention, Figure 2 is a cross-sectional view of the control member according to the invention, Figure 3 Figure 4 is a longitudinal sectional view of an MR brake according to another embodiment of the invention, Figure 4 is a cross-sectional view showing the operating state of the MR brake according to the invention, Figure 5 is a schematic diagram showing a tension control process of the elastic spring according to the present invention. 6 is a state diagram showing another embodiment according to the present invention, Figure 7 is a plan view showing a 2D model of the MR brake for electromagnetic field analysis, Figure 8a and Figure 8b is an intermittent member according to the first embodiment 9A and 9B are graphs showing the magnetic field strength of Example 1, FIGS. 10A and 10B are graphs showing torque results of Examples 1 and 2, and FIG. Of the present invention 12A and 12B are plan views showing electromagnetic field distribution according to the position of the intermittent member according to Example 3, and FIGS. 13A and 13B are examples of the third embodiment of the MR brake for electromagnetic field analysis according to another embodiment. 14A and 14B are graphs showing torque results of Examples 3 and 4, and FIG. 15 is a graph showing torque results of Examples 1 to 4 according to the present invention.

The rotary MR brake 10 using the permanent magnet according to the present invention is mounted on one side of the rotating shaft 70 to rotate by causing the MR fluid's viscosity to be changed by the magnetic force of the intermittent member 40 when the overrotation occurs. Adjust the speed. Such a device includes a housing 20 coupled to a rotating shaft 70, a guide rod 30 and an intermittent member 40 mounted inside the housing, and an MR fluid filled in the space inside the housing.

The housing 20 is a cylindrical body coupled to the bearing 23 on one side of the rotating shaft, the hollow portion 21 is formed therein. The housing 20 may be integrally coupled by a fastening means such as a bolt by separating the front and the rear.

In addition, a deceleration chamber 22 is formed along the inner circumference of the housing 20. The deceleration chamber is a place where the guide rod 30 to be described later is rotated, the width of the deceleration chamber 22 is formed to be narrower than the hollow portion 21.

Next, the guide rod 30 is coupled to the rotation shaft 70 in the vertical direction. The guide rod 30 is rotated together with the rotating shaft, one end of which is fixed to the rotating shaft 70, and the other end extends to a portion near the inner circumference of the deceleration chamber. Of course, the coupling of the guide rod and the rotating shaft may be made in a variety of ways, such as by screw coupling or welding, the cross section of the guide rod may be formed in a circular shape, or a triangular or square polygon.

The guide rod 30 is inserted into the intermittent member 40 has a through hole formed therein. That is, the intermittent member 40 is fastened in a structure capable of sliding along the axis of the guide rod by inserting the guide rod into the through hole therein. The width of the intermittent member is formed to be smaller than the width of the deceleration chamber described above to prevent contact with the inner surface of the deceleration chamber during rotation in the deceleration chamber 22 to prevent wear or deterioration of the rotational force. In addition, since the intermittent member 40 is rotated on the guide rod to be in contact with the inner surface of the deceleration chamber, the intermittent member is formed in a cylinder to prevent contact with the rotating, or the guide rod 30 and the intermittent member 40 are formed. The through-hole of) can be made into a polygon to prevent the intermittent member from rotating.

At this time, the intermittent member 40 has a quadrangular shape of the inner through-hole 43 of the movable member 41 as shown in FIG. 2, and permanent magnets on both sides adjacent to the inner wall of the deceleration chamber, which are both sides of the movable member. (42) can be attached so that a magnetic force can be generated. Here, the intermittent member may be integrated with the moving member and the permanent magnet without forming a separate member to form the entire intermittent member as a permanent magnet.

In addition, the housing 20 forming the hollow part 21 and the reduction chamber 22 may be formed of different materials. As shown in FIG. 3, a portion of the housing 20a that forms the reduction chamber 22 is formed of a magnetic material, and a portion of the housing 20b that forms the hollow portion 21 is formed of a non-magnetic material. The magnetic force of the phosphorus intermittent member 40 can be prevented from increasing the viscosity of the MR fluid, it is possible to increase the viscosity of the MR fluid when the intermittent member is introduced into the deceleration chamber. It is preferable to use iron as a material of the said magnetic body, and it is preferable to use stainless steel as a nonmagnetic material.

As described above, an elastic spring 50 is mounted on one surface of the intermittent member 40 that is moved on the guide rod to limit the moving surface of the intermittent member. That is, the elastic spring 50 is one surface is coupled to the rotation shaft 70 and the other side is coupled to the intermittent member 40 so that the intermittent member is normally located in the hollow portion 21 of the housing, when rotating When the speed exceeds a predetermined speed, the intermittent member is inserted into the deceleration chamber 22 of the housing and rotated by the centrifugal force. Therefore, during the over-rotation, the centrifugal force is greater than the elastic force of the elastic spring 50 which controls the intermittent member 40, so that the intermittent member 40 moves in the outward direction of the rotating shaft and flows into the deceleration chamber 22. do. At this time, the hollow portion may be such that the MR fluid is introduced into the deceleration chamber without vortex generation by using the portion connected to the deceleration chamber as an inclined surface as shown in FIG.

The intermittent member 40 introduced into the deceleration chamber 22 has the magnetic flux density of the gap between the deceleration chamber and the intermittent member due to the magnetic force generated between the intermittent member, which is a permanent magnet, and the deceleration chamber, which is a magnetic body. The viscosity of the fluid becomes high and friction torque is generated. Therefore, the high speed rotation speed is decelerated by the friction torque and the rotation speed is controlled.

In addition, the elastic spring 50 can be adjusted to its tension by an external operation.

As shown in FIG. 4, the elastic spring 50 may be coupled to a knob 71 mounted at one end of the rotating shaft 70 through the inside of the rotating shaft 70. The knob 71 is screwed to the end of the rotary shaft to rotate the knob to be spaced apart from the end by a predetermined distance so that the elastic spring 50 located inside the housing by the length of the knob and the rotary shaft in the interior of the rotary shaft It is possible to shorten the length that is drawn in and exposed to the outside.

As described above, when the length of the elastic spring 50 is shortened, the intermittent member 40 can be introduced into the deceleration chamber at a larger rotational speed than the basic, so that the upper limit of the speed of the rotating shaft is adjusted by adjusting the length of the elastic spring. It can be adjustable.

In addition, the length of the elastic spring 50 can be adjusted in the form shown in FIG. The end of the rotating shaft is screwed to the engaging rod 72 has a locking projection 721 is formed on the inner circumference, the elastic spring 50 is coupled to the end of the locking rod and the locking groove corresponding to the locking projection on the outer circumference 731 is coupled to the hook member 73 is formed to be able to adjust the length of the elastic spring 50 by the combination of the engaging projection and the engaging groove. At this time, when the hook member 73 is pressed in the axial direction, the hook member 73 may be bent by elastic deformation to allow movement within the engaging rod, and to enable elastic deformation of the hook member 73. Both sides of the hook member is preferably formed to form a cutting groove 732 of a predetermined width in the axial direction.

In addition, the length of the adjustment can be made by rotating the knob so that the elastic spring is wound inside the knob. In this case, the knob may be coupled to the rotating shaft in a structure that prevents detachment by rotation.

In this way, in order to increase the strength of the magnetic force, as shown in Figure 6 by installing a plurality of guide rods 30 on the rotating shaft 70, the intermittent member 40 installed in each guide rod when the over-rotation speed By increasing the area in which the high magnetic flux density is generated in the reduction chamber, as the viscosity of the MR fluid increases, a strong torque is generated to decrease the rotation speed. As the centrifugal force decreases when the rotational speed decreases, the intermittent member 40 is moved from the deceleration chamber 22 to the hollow portion 21 by the elastic restoring force of the elastic spring, thereby eliminating the section in which the high magnetic flux density is generated. As the viscosity is lowered, the speed of the rotating shaft may be limited to a predetermined speed or less in a process of suppressing friction torque generation.

It will be described in detail through the following examples.

To verify the performance of the proposed system, we analyzed the system. First, the finite element method is used to analyze the electromagnetic field according to the position of the permanent magnet. The magnetic field strength between the pores between the magnet and the case was obtained by electromagnetic field finite element analysis, and the shear stress of MR fluid was determined according to the position of the permanent magnet using the relationship between the magnetic field strength and the shear stress of the fluid in the MR fluid. . Using the shear stress, the torque of the MR brake according to the radial position of the permanent magnet is obtained, and the performance of the proposed rotary MR brake is verified.

Example 1 - As shown in Fig. 7, the speed limiting device is assumed to be a 2D model of the Cartesian coordinate system, and the housing forming the hollow part and the deceleration chamber is made of steel, and the intermittent member is made of a permanent magnet. At this time, the size of the permanent magnet was 5mm × 5mm × 3mm.

Example 2 - As shown in Fig. 7, the speed limiting device is assumed to be a 2D model of the Cartesian coordinate system, and the housing forming the hollow part and the deceleration chamber is made of steel, and the intermittent member is made of a permanent magnet. At this time, the size of the permanent magnet was 10mm × 5mm × 3mm.

Experimental Example 1 Electromagnetic Field Analysis

Maxwell, a commercial finite element program, was used to analyze the electromagnetic field of the speed limiter. Nd-based magnets were used for permanent magnets, and MDF 122 of Lord Corporation was used for MR fluids.

The initial position of the magnet is assumed to be 5 mm radially away from the center line, and the electromagnetic field analysis is performed according to the radial displacement (dr) at the initial position.

The electromagnetic field analysis results according to the radial position of the magnet when the permanent magnet is located in the hollow part of the housing and the deceleration chamber using Example 1 are shown in FIGS. 8A and 8B, respectively.

As shown in FIG. 8A, the magnetic flux density is 0.2T, but in the case of FIG. 8B, the magnetic flux density is higher when the permanent magnet is located in the deceleration chamber at about 4 times as the magnetic flux density is 0.9T or more.

In addition, the intensity of the magnetic field according to the position is shown in Figs. 9a and 9b, and Example 2 was also summarized in Table 1 under the same conditions.

Experimental Example 2 -Calculation of Torque of Rotary MR Brake

The relationship between magnetic field strength and shear stress in MR fluids is

(τ: shear stress, B: magnetic flux density (T))

As the magnetic flux density increases, the shear stress also increases. The relationship between the magnetic field strength H and the magnetic flux density B is

(μ: Permeability, H: Magnetic field strength (A / m))

to be.

When the shear stress of the MR fluid is obtained through the magnetic field analysis, the torque T of the rotary MR brake at the position x of the permanent magnet is expressed by Equation (3).

(η: viscosity coefficient (Pa-s), g: gap (m), A: area (m ² ), S: relative velocity, F: shear stress)

In addition, the torque T of the rotary MR brake in the case of four permanent magnets is expressed by Equation 4.

Can be expressed as:

Torques were obtained for the rotary MR brakes of Examples 1 and 2 using Table 1 and Equation 4, and are shown in FIGS. 10A and 10B.

In the case of Example 1, it can be seen that the maximum torque is about 0.1Nm in the hollow part, and about 0.52Nm in the deceleration chamber. In Example 2, it can be seen that it is about 0.3Nm in the hollow part and about 1.02Nm in the deceleration room. .

Example 3 - As shown in FIG. 11, the housing forming the hollow part under the same conditions as in Example 1 was made of stainless steel, which is a non-magnetic material, and the housing forming the deceleration chamber was made of steel. It is a permanent magnet. At this time, the size of the permanent magnet was 5mm × 5mm × 3mm.

Example 4 - As shown in FIG. 11, the housing forming the hollow part under the same conditions as in Example 1 was made of stainless steel, which is a nonmagnetic material, and the housing forming the deceleration chamber was made of steel. The member was made into a permanent magnet. At this time, the size of the permanent magnet was 10mm × 5mm × 3mm.

Experimental Example 3 -Electromagnetic Field Analysis

It was carried out under the same conditions as in Experiment 1.

The electromagnetic field analysis results according to the radial positions of the magnets when the permanent magnets are located in the hollow part of the housing and the deceleration chamber using the third embodiment are shown in FIGS. 12A and 12B, respectively.

As shown, it can be seen that the magnetic flux density in FIG. 12A is 0.1T, the magnetic flux density in FIG. 12B is 0.9T, and the magnetic flux density in the hollow portion is lower than those of the first and second embodiments.

In addition, the intensity of the magnetic field according to the position is shown in Figure 13a and 13b, Example 4 was measured and summarized in Table 2 under the same conditions.

Experimental Example 4 -Calculation of Torque of Rotary MR Brake

Torques for Example 3 and Example 4 were calculated in the same manner as in Experimental Example 2 and are shown in FIGS. 14A and 14B.

As shown in Example 3, the maximum torque in the hollow part is 0.03 Nm, and in Example 4, about 0.1 Nm, in Example 3, the torque in the hollow part is reduced by about 70% compared to Example 1, In the case of Example 4, it can be seen that the torque in the hollow portion is reduced by about 67% compared to Example 2. The measured torques of Examples 1 to 4 are shown in FIG. 15.

Therefore, when designing a rotating MR brake using a permanent magnet, it can be seen that the housing of the region (hollow part) where torque is to be minimized should be made of nonmagnetic material.

As described in detail above, the rotary MR brake using the permanent magnet of the present invention,

According to the strength of the centrifugal force, the intermittent member, which is a permanent magnet, is movably embedded, and when the intermittent member is above a certain speed, the intermittent member is introduced into the narrow reduction chamber by the centrifugal force to increase the magnetic flux density of the gap between the intermittent member and the reduction chamber. A device that increases the viscosity of the MR fluid and generates a large friction torque on one side of the rotating shaft is provided so that the rotational speed is kept below a certain level by reducing the rotational speed by increasing the viscosity of the MR fluid only when overrotating. It is possible to provide.

In addition, the above-mentioned example is only an example to demonstrate this invention. Therefore, it is obvious that the ordinary skilled in the art to which the present invention pertains uses the partial change with reference to the detailed description.

Claims (7)

In the brake which is mounted on one side of the rotating shaft of the rotating body to limit the rotation speed, A housing 20 having a bearing 23 coupled to one side of the rotation shaft 70 and a hollow portion 21 formed therein; A reduction chamber 22 formed in a narrower width than the hollow portion along an inner circumference of the housing 20; A guide rod 30 coupled to the rotation shaft 70 in a vertical direction, the end of which is rotated close to the inner circumference of the reduction chamber 22; The permanent magnet mounted on the guide rod 30 is slidably moved on the guide rod by centrifugal force to increase the magnetic flux density in the gap between the reduction chambers by the magnetic field when it enters the reduction chamber 22 to change the MR fluid viscosity. An intermittent member 40; An elastic spring 50 having one end coupled to the intermittent member 40 and the other end coupled to the rotating shaft 70 to limit movement of the intermittent member; The MR fluid (60) is filled in the hollow portion and the reduction chamber inside the housing and the viscosity is changed by the magnetic field; Rotating MR brake using a permanent magnet, characterized in that it comprises a. delete The method of claim 1, The intermittent member 40 includes a moving member 41 formed with a through hole 43 therein to slide on the guide rod 30; Rotary MR brake using a permanent magnet, characterized in that made of a permanent magnet (42) attached to both sides of the moving member in proximity to the inner wall of the hollow portion 21 and the reduction chamber 22 of the housing. The method of claim 1, The housing 20 is a rotating MR brake using a permanent magnet, characterized in that the inner portion constituting the deceleration chamber 22 is formed of a magnetic material, the hollow portion 21 is formed of a non-magnetic material. The method of claim 1, The elastic spring 50 is one end is coupled to the intermittent member 40 and the other end is connected to the knob 71 mounted at the end of the rotary shaft through the inside of the rotary shaft 70 to adjust the distance between the knob and the rotary shaft end Rotary MR brake using a permanent magnet, characterized in that the tension of the elastic spring 50 is adjusted. The method of claim 1, The guide rod 30 and the intermittent member 40 is a rotary MR brake using a permanent magnet, characterized in that the plurality is formed symmetrical about the rotation axis (70). The method of claim 1, The hollow portion 21 is a rotary MR brake using a permanent magnet, characterized in that the MR fluid is introduced into the deceleration chamber without the vortex generated by the portion connected to the deceleration chamber 22 as an inclined surface.

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