JP2012177406A - Magnetic viscous fluid damper - Google Patents

Abstract

In a magnetorheological fluid shock absorber in which a magnet is attached to a cylinder, a damping coefficient is continuously changed with respect to a stroke amount of a piston.
A magnetorheological fluid is formed between a cylinder 10 that is formed in a cylindrical shape by a nonmagnetic material and in which a magnetorheological fluid whose viscosity is changed by the action of a magnetic field is sealed, and an inner periphery of the cylinder 10 that is formed by a nonmagnetic material. Includes a piston 21 slidably disposed in the cylinder 10 with an interval through which the piston 10 can pass, a piston rod 22 to which the piston 21 is coupled, and a magnet 30 for applying a magnetic field in the cylinder 10. It has at least one of a tapered flat surface portion 15 formed on the outer peripheral surface and changing in thickness in a taper shape toward the axial direction, and a tapered inner peripheral portion 216 formed on the inner peripheral surface, The magnet 30 is attached to the outer periphery of the cylinder 10 corresponding to the position where the tapered flat portion 15 and the tapered inner peripheral portion 216 are formed.
[Selection] Figure 1

Description

  The present invention relates to a magnetorheological fluid shock absorber using a magnetorheological fluid whose apparent viscosity changes due to the action of a magnetic field.

  As a shock absorber mounted on a vehicle such as an automobile, there is a shock absorber that changes a damping force by applying a magnetic field to a flow path through which the magnetorheological fluid passes to change an apparent viscosity of the magnetorheological fluid.

  Patent Document 1 discloses a magnetorheological fluid damper in which permanent magnets are attached to both axial ends of a cylinder in which magnetorheological fluid is sealed. In this magnetorheological fluid damper, a yoke material is provided on the outer periphery of a cylinder, and a piston and a part of the piston rod are formed of a ferromagnetic material. When the piston is located in the neutral region, the magnetic force of the permanent magnet does not act on the magnetorheological fluid, but when the piston strokes beyond the neutral region, the permanent magnet passes through the piston rod, piston, and yoke material. A magnetic circuit is formed. As a result, the magnetic force of the permanent magnet acts on the magnetorheological fluid between the piston and the cylinder, and the viscosity of the magnetorheological fluid increases and the damping coefficient increases.

JP 2007-239982 A

  However, the magnetoviscous fluid damper described in Patent Document 1 is such that when the piston strokes beyond the neutral region, the magnetic force of the permanent magnet acts on the magnetorheological fluid to greatly change the damping coefficient. That is, in this magnetorheological fluid damper, the viscosity of the magnetorheological fluid changes stepwise between when the piston is located in the neutral region and when the piston exceeds the neutral position. As a result, the damping coefficient of the magnetorheological fluid damper changes stepwise in accordance with the stroke amount of the piston sliding in the cylinder.

  The present invention has been made in view of the above problems, and an object of the present invention is to continuously change a damping coefficient with respect to a stroke amount of a piston in a magnetorheological fluid shock absorber in which a magnet is attached to a cylinder. .

  According to the present invention, a magnetic viscosity is formed between a cylinder formed of a non-magnetic material and encapsulated with a magnetorheological fluid whose viscosity is changed by the action of a magnetic field, and an inner periphery of the cylinder. A magnetorheological fluid shock absorber comprising: a piston slidably disposed in the cylinder at intervals through which fluid can pass; a piston rod to which the piston is coupled; and a magnet for applying a magnetic field in the cylinder. The cylinder has a tapered portion that is formed on at least one of an outer peripheral surface and an inner peripheral surface thereof and changes in thickness in a tapered shape in the axial direction, and the magnet is formed by the tapered portion. It is attached to the outer periphery of the cylinder corresponding to the position to be performed.

  In the present invention, a tapered portion whose thickness changes in a tapered shape toward the axial direction of the cylinder is formed in the cylinder, and a magnet is attached at a position where the tapered portion is formed. Therefore, the distance between the magnetorheological fluid sealed in the cylinder and the magnet continuously changes following the taper of the taper portion. Therefore, since the strength of the magnetic field acting on the magnetorheological fluid is continuous with respect to the stroke amount of the piston, the damping coefficient can be continuously changed.

It is sectional drawing of the magnetorheological fluid shock absorber concerning the 1st Embodiment of this invention. It is sectional drawing of the magnetorheological fluid shock absorber concerning the 2nd Embodiment of this invention. It is sectional drawing of the magnetorheological fluid shock absorber which concerns on the 3rd Embodiment of this invention. It is a graph explaining the effect | action of the magnetorheological fluid shock absorber which concerns on each 1st-3rd embodiment of this invention.

  Embodiments of the present invention will be described below with reference to the drawings.

(First embodiment)
First, with reference to FIG. 1, the magnetorheological fluid shock absorber 100 according to the first embodiment of the present invention will be described.

  The magnetorheological fluid shock absorber 100 is a damper whose damping coefficient can be changed by using a magnetorheological fluid whose viscosity changes by the action of a magnetic field. The magnetorheological fluid shock absorber 100 is formed such that its damping coefficient changes in proportion to the stroke amount.

  The magnetorheological fluid shock absorber 100 includes a cylinder 10 in which magnetorheological fluid is sealed, a piston 21 slidably disposed in the cylinder 10, a piston rod 22 to which the piston 21 is coupled, and an outer periphery of the cylinder 10. And a magnet 30 that is fixed and causes a magnetic field to act in the cylinder 10.

  The magnetorheological fluid sealed in the cylinder 10 has an apparent viscosity that is changed by the action of a magnetic field, and is a liquid in which fine particles having ferromagnetism are dispersed in a liquid such as oil. The viscosity of the magnetorheological fluid changes according to the strength of the applied magnetic field, and returns to its original state when the magnetic field is no longer affected.

  The cylinder 10 includes a cylindrical portion 11 formed in a cylindrical shape having openings at both ends thereof, and a head member 12 and a bottom member 13 attached to the openings at both ends of the cylindrical portion 11.

  The cylindrical portion 11 has a screwing portion 11a formed on the inner periphery of one opening and a screwing portion 11b formed on the inner periphery of the other opening.

  On the outer periphery of the head member 12, a screwing portion 12b that is screwed with the screwing portion 11a is formed. A seal member 14a is provided between the inner periphery of the cylindrical portion 11 and the outer periphery of the head member 12, and the magnetorheological fluid in the cylinder 10 is sealed. The head member 12 is formed with a hole 12a through which the piston rod 22 is inserted.

  Similarly, on the outer periphery of the bottom member 13, a screwing portion 13b that is screwed with the screwing portion 11b is formed. A seal member 14b is provided between the inner periphery of the cylindrical portion 11 and the outer periphery of the bottom member 13, and the magnetorheological fluid in the cylinder 10 is sealed. The bottom member 13 is formed with a hole 13a through which the piston rod 22 is inserted.

  The cylinder 10 is formed of a nonmagnetic material. As a result, the cylinder 10 is prevented from becoming a magnetic path, and a magnetic field can be efficiently applied to the magnetorheological fluid sealed in the cylinder 10.

  The cylinder 10 has a tapered flat surface portion 15 that is provided on the outer peripheral surface of the cylindrical portion 11 and is formed in a tapered shape in the axial direction so as to gradually change the thickness of the cylindrical portion 11. In the magnetorheological fluid shock absorber 100, the tapered flat surface portion 15 corresponds to the tapered portion.

  The tapered flat surface portion 15 is formed in a concave shape on the outer peripheral surface of the cylindrical portion 11 in the cylinder 10. The taper plane part 15 is formed in two places at intervals of 180 degrees. The pair of tapered flat portions 15 are formed in a rectangular shape and are provided so as to face each other. The taper plane part 15 is formed in the tangential direction of the cylinder 10 formed in a cylindrical shape.

  The tapered flat portion 15 is formed on the outer peripheral surface of the cylinder 10 corresponding to a position corresponding to the position of the piston 21 when the piston rod 22 enters the cylinder 10 most. The tapered flat portion 15 is formed so that the thickness of the cylindrical portion 11 in the cylinder 10 becomes thinner in the direction in which the piston rod 22 enters the cylinder 10.

  Instead of forming the tapered flat portion 15, a tapered portion formed in a concave shape along the curved surface of the outer peripheral surface of the cylinder 10 may be provided, and the magnet 30 may be formed in an arc shape along the curved surface of the tapered portion. .

  The piston 21 is formed in a columnar shape whose outer diameter is smaller than the inner diameter of the cylindrical portion 11 in the cylinder 10. That is, the piston 21 is formed between the inner periphery of the cylindrical portion 11 in the cylinder 10 with an annular interval through which the magnetorheological fluid can pass.

  When the piston 21 slides in the cylinder 10 in the axial direction, the magnetorheological fluid passes through the space between the piston 21 and the cylinder 10. The magnetorheological fluid shock absorber 100 generates a damping force by the annular space between the piston 21 and the cylinder 10 acting as a throttle.

  The piston 21 is formed of a nonmagnetic material. Thereby, the magnetic field of the magnet 30 does not act directly on the piston 21, and it is possible to prevent the piston 21 from being brought to one side and increasing the friction.

  The piston rod 22 is formed to be coaxial with the piston 21 and is inserted through the center of the piston 21. The piston rod 22 is formed integrally with the piston 21. The piston rod 22 may be formed separately from the piston 21 and joined by screws or the like.

  One end 22 a of the piston rod 22 is inserted through the hole 12 a of the head member 12, is slidably supported by the head member 12, and extends to the outside of the cylinder 10. The other end 22 b of the piston rod 22 is inserted into the hole 13 a of the bottom member 13 and is slidably supported by the bottom member 13.

  As described above, the piston rod 22 is slidably supported by the head member 12 and the bottom member 13, so that an annular interval is provided between the outer peripheral surface of the piston 21 and the inner periphery of the cylinder 10. The cylinder 10 can slide in the axial direction without being displaced in the radial direction.

  The magnet 30 is a permanent magnet whose end surface 31 is formed in a shape corresponding to the tapered flat portion 15 of the cylinder 10. The magnets 30 are respectively attached to the pair of tapered flat portions 15. Since the tapered flat surface portion 15 is formed in a concave shape on the outer peripheral surface of the cylinder 10, it is thinner than other portions of the cylinder 10. Therefore, it does not prevent the magnetic field of the magnet 30 from acting on the magnetorheological fluid sealed in the cylinder 10.

  The magnet 30 is formed in a rectangular parallelepiped shape so that the end surface 31 thereof is rectangular corresponding to the tapered flat portion 15 formed in a rectangle. In addition to this, the tapered flat portion 15 may be formed in a circular shape, and the magnet 30 may be formed in a cylindrical shape whose end surface 31 is circular.

  Thus, by forming the tapered flat surface portion 15 on the outer peripheral surface of the cylinder 10, it is not necessary to form the magnet 30 to be attached in an arc shape corresponding to the outer peripheral surface of the cylinder 10, and the end surface 31 of the magnet 30. Can be formed in a planar shape. Therefore, the machining cost of the magnet 30 can be reduced, and the attachment of the magnet 30 to the cylinder 10 can be improved.

  A pair of magnets 30 are provided so as to face each other. One of the magnets 30 has an N pole at an end surface 31 in contact with the tapered flat portion 15 of the cylinder 10, and the other magnet 30 has an S pole at an end surface 31 in contact with the tapered flat portion 15 of the cylinder 10. Thereby, a linear magnetic field is generated between a pair of opposing magnets 30, and the magnetic field can be applied to the magnetorheological fluid in the cylinder 10.

  The magnet 30 may be formed in a flat plate shape having a thickness that fits in the outer diameter of the cylinder 10 when attached to the tapered flat portion 15. In this case, since the magnet 30 does not protrude from the cylinder 10 to the outer periphery, it can be used in the same manner as a normal shock absorber in which the magnet 30 is not provided. For example, a coil spring can be attached to the outer periphery of the magnetorheological fluid shock absorber 100 and used as a spring damper.

  The magnet 30 is disposed corresponding to the position of the piston 21 when the piston rod 22 enters the cylinder 10 most. That is, in FIG. 1, the magnet 30 is disposed so as to face the outer periphery of the piston 21 when the piston 21 is lowered most.

  As a result, the magnetorheological fluid in the cylinder 10 has a low viscosity at a position away from the magnet 30 because the influence of the magnetic field is small. The closer the magnet 30 is, the greater the influence of the magnetic field is and the collection of ferromagnetic particles. Viscosity increases.

  Moreover, since the magnet 30 is attached to the taper plane part 15, the distance between the magnet 30 and the magnetorheological fluid in the cylinder 10 differs depending on the position in the axial direction. Therefore, even between the pair of magnets 30, the viscosity of the magnetorheological fluid in the cylinder 10 differs depending on the position in the axial direction.

  Specifically, between the pair of magnets 30, the tapered flat surface portion 15 is formed, so that the thickness of the cylindrical portion 11 gradually decreases in the direction in which the piston rod 22 enters the cylinder 10. For this reason, the distance between the magnet 30 attached to the tapered flat portion 15 and the magnetorheological fluid in the cylinder 10 continuously changes in a small manner following the taper of the tapered flat portion 15. Therefore, the viscosity of the magnetorheological fluid gradually increases in the direction in which the piston rod 22 enters the cylinder 10.

  As described above, when the piston rod 22 strokes in the direction of entering the cylinder 10, the influence of the magnetic field by the magnet 30 on the magnetorheological fluid passing through the interval between the piston 21 and the cylinder 10 gradually increases. Thereby, the apparent viscosity of the magnetorheological fluid is proportionally increased in accordance with the stroke amount of the piston rod 22 in the direction of entering the cylinder 10. Therefore, the damping coefficient of the magnetorheological fluid shock absorber 100 increases as the piston rod 22 enters the cylinder 10.

  Here, with reference to FIG. 4, the change of the damping coefficient in the magnetorheological fluid shock absorber 100 will be described. In FIG. 4, the horizontal axis represents the stroke amount [m], which is the amount of the piston rod 22 entering the cylinder 10, and the vertical axis represents the damping coefficient [N · s / m] of the magnetorheological fluid buffer 100.

  The damping coefficient of the magnetorheological fluid shock absorber 100 increases proportionally as indicated by a straight line A in FIG.

Specifically, when the piston rod 22 enters the cylinder 10 from a state where the stroke amount is S _min , the damping coefficient increases proportionally, and when the stroke amount is S _max , the damping coefficient becomes maximum. . This is because the viscosity of the magnetorheological fluid gradually increases at the annular interval between the piston 21 and the cylinder 10.

  Thus, by forming the tapered flat portion 15 in the cylinder 10, the distance between the magnetorheological fluid sealed in the cylinder 10 and the magnet 30 continuously changes following the taper of the tapered flat portion 15. It will be. Therefore, since the strength of the magnetic field acting on the magnetorheological fluid continuously changes with respect to the stroke amount of the piston 21, the attenuation coefficient can be changed continuously.

  It is possible to adjust the rate of change of the attenuation coefficient with respect to the stroke amount by adjusting the taper angle in the taper plane portion 15.

  According to the above 1st Embodiment, there exists the effect shown below.

  A tapered flat portion 15 whose thickness changes in a taper shape toward the axial direction of the cylinder 10 is formed in the cylindrical portion 11, and a magnet 30 is attached to a position where the tapered flat portion 15 is formed, so that the inside of the cylinder 10 is formed. The distance between the magnetorheological fluid to be sealed and the magnet 30 changes continuously following the taper of the taper flat portion 15. Therefore, since the strength of the magnetic field acting on the magnetorheological fluid continuously changes with respect to the stroke amount of the piston 21, the attenuation coefficient can be changed continuously.

(Second Embodiment)
Hereinafter, with reference to FIG. 2, a magnetorheological fluid shock absorber 200 according to a second embodiment of the present invention will be described. In each embodiment described below, the same reference numerals are given to the same components as those in the above-described embodiment, and a duplicate description will be omitted as appropriate.

  The second embodiment is different from the above-described embodiment in that a flat surface portion 215 is formed on the outer peripheral surface of the cylinder 210 and a tapered inner peripheral portion 216 is formed on the inner periphery of the cylinder 210.

  The cylinder 210 has a pair of flat portions 215 formed thinner on the outer peripheral surface of the cylindrical portion 11 than the other portions of the cylinder 210, and is provided on the inner periphery of the cylindrical portion 11 and is tapered in the axial direction. And a tapered inner peripheral portion 216 that is formed and gradually changes the thickness of the cylindrical portion 11. In the magnetorheological fluid shock absorber 200, the tapered inner peripheral portion 216 corresponds to the tapered portion.

  The flat portion 215 is formed in a concave shape on the outer peripheral surface of the cylindrical portion 11 in the cylinder 210. The flat portions 215 are formed at two locations at intervals of 180 degrees. The pair of flat portions 215 are provided to face each other in parallel. The plane portion 215 is formed in a rectangular shape as a plane parallel to the tangential direction of the cylinder 10 formed in a cylindrical shape. The magnets 30 are respectively attached to the pair of flat portions 215.

  Thus, by forming the flat portion 215 on the outer peripheral surface of the cylinder 210, it is not necessary to form the magnet 30 to be attached in an arc shape corresponding to the outer peripheral surface of the cylinder 210, and the end surface 31 of the magnet 30 is formed. It can be formed in a planar shape. Therefore, the machining cost of the magnet 30 can be reduced, and the attachment of the magnet 30 to the cylinder 210 can be improved.

  The tapered inner peripheral portion 216 is formed on the inner periphery of the cylinder 210 corresponding to the position where the flat portion 215 is formed on the outer peripheral surface. The tapered inner peripheral portion 216 is formed on the inner periphery of the cylinder 210 corresponding to a position corresponding to the position of the piston 21 when the piston rod 22 enters the cylinder 210 most. The tapered inner peripheral portion 216 is formed so that the thickness of the cylindrical portion 11 in the cylinder 210 becomes thinner in the direction in which the piston rod 22 enters the cylinder 210.

  The magnet 30 is attached to a flat portion 215 formed on the outer peripheral surface of the cylinder 210 corresponding to the position where the tapered inner peripheral portion 216 is formed. Therefore, the thickness of the cylindrical portion 11 gradually decreases between the pair of magnets 30 in the direction in which the piston rod 22 enters the cylinder 10. In other words, the distance between the magnet 30 and the magnetorheological fluid in the cylinder 10 changes continuously and decreases along the taper of the taper inner peripheral portion 216. Therefore, since the magnetic field acting on the magnetorheological fluid from the magnet 30 gradually increases in the direction in which the piston rod 22 enters the cylinder 210, the viscosity of the magnetorheological fluid gradually increases.

  As described above, when the piston rod 22 strokes in the direction of entering the cylinder 210, the influence of the magnetic field by the magnet 30 on the magnetorheological fluid passing through the interval between the piston 21 and the cylinder 210 gradually increases. Thereby, according to the stroke amount of the piston rod 22 in the direction of entering the cylinder 210, the apparent viscosity of the magnetorheological fluid is proportionally increased. Therefore, the damping coefficient of the magnetorheological fluid shock absorber 100 increases as the piston rod 22 enters the cylinder 10.

  The damping coefficient of the magnetorheological fluid shock absorber 200 increases proportionally as indicated by a straight line B in FIG. The damping coefficient of the magnetorheological fluid shock absorber 200 has a small increase rate with respect to the stroke amount as compared with the damping coefficient of the magnetorheological fluid shock absorber 100 in the first embodiment. This is because the distance between the magnet 30 and the magnetorheological fluid gradually approaches, and at the same time, the annular interval between the piston 21 acting as a throttle and the cylinder 10 gradually increases.

  In the magnetorheological fluid shock absorber 200, compared to the effect due to the increase in the annular interval between the piston 21 and the cylinder 10, the effect due to the viscosity of the magnetorheological fluid becoming higher as the magnet 30 approaches. Is big. Thereby, the damping coefficient of the magnetorheological fluid shock absorber 200 increases in proportion to the stroke amount.

  According to the second embodiment described above, since the tapered inner peripheral portion 216 is formed in the cylinder 210, the distance between the magnetorheological fluid sealed in the cylinder 210 and the magnet 30 is the same as that of the tapered inner peripheral portion 216. It changes continuously following the taper. Therefore, since the strength of the magnetic field acting on the magnetorheological fluid continuously changes with respect to the stroke amount of the piston 21, the attenuation coefficient can be changed continuously.

(Third embodiment)
Hereinafter, with reference to FIG. 3, a magnetorheological fluid shock absorber 300 according to a third embodiment of the present invention will be described.

  The third embodiment is different from the above-described embodiment in that the tapered flat surface portion 15 is formed on the outer peripheral surface of the cylinder 310 and the tapered inner peripheral portion 216 is formed on the inner periphery of the cylinder 310. To do.

  The cylinder 310 is provided on the outer peripheral surface of the cylindrical portion 11, is formed in a tapered shape in the axial direction, and is provided on the inner periphery of the cylindrical portion 11. The tapered flat portion 15 gradually changes the thickness of the cylindrical portion 11. And a tapered inner peripheral portion 216 that is tapered toward the axial direction and gradually changes the thickness of the cylindrical portion 11. In the magnetorheological fluid shock absorber 300, the tapered flat portion 15 and the tapered inner peripheral portion 216 correspond to the tapered portion.

  The damping coefficient of the magnetorheological fluid shock absorber 300 increases proportionally as shown by the straight line C in FIG. The damping coefficient of the magnetorheological fluid shock absorber 300 has a smaller increase rate with respect to the stroke amount than the damping coefficient of the magnetorheological fluid shock absorber 100 in the first embodiment, and the magnetorheological fluid buffer in the second embodiment. Larger than the vessel 200.

  This is because when the tapered inner peripheral portion 216 is formed, the distance between the magnet 30 and the magnetorheological fluid gradually approaches, and the annular interval between the piston 21 acting as a throttle and the cylinder 10 gradually increases. This is because the distance between the magnet 30 and the magnetorheological fluid becomes closer due to the formation of the tapered flat portion 15.

  According to the third embodiment described above, since the tapered flat portion 15 and the tapered inner peripheral portion 216 are formed in the cylinder 310, the distance between the magnetorheological fluid sealed in the cylinder 210 and the magnet 30 is It changes continuously following the taper of the taper flat portion 15 and the taper inner peripheral portion 216. Therefore, since the strength of the magnetic field acting on the magnetorheological fluid continuously changes with respect to the stroke amount of the piston 21, the attenuation coefficient can be changed continuously.

  As described above, in the first embodiment, the tapered flat portion 15 is formed on the outer peripheral surface of the cylinder 10 as the tapered portion. In the second embodiment, a tapered inner peripheral portion 216 is formed on the inner periphery of the cylinder 10 as the tapered portion. In the third embodiment, the tapered flat surface portion 15 and the tapered inner peripheral portion 216 are formed on both the outer peripheral surface and the inner periphery of the cylinder 10 as the tapered portion.

  As described above, if a tapered portion is formed on at least one of the outer peripheral surface and the inner peripheral surface of the cylinder, the thickness of the cylinder changes in a tapered shape in the axial direction, and the stroke amount of the piston 21 is reduced. Since the strength of the magnetic field acting on the magnetorheological fluid changes continuously, the attenuation coefficient can be changed continuously.

  The present invention is not limited to the above-described embodiment, and it is obvious that various modifications can be made within the scope of the technical idea.

  The magnetorheological fluid shock absorber according to the present invention can be used as a shock absorber mounted on a vehicle or the like.

100 Magnetorheological fluid shock absorber 10 Cylinder 11 Cylindrical part 15 Tapered flat part (tapered part)
21 Piston 22 Piston rod 30 Magnet 31 End face 200 Magnetorheological fluid shock absorber 210 Cylinder 215 Flat portion 216 Tapered inner peripheral portion (tapered portion)
300 Magnetorheological fluid shock absorber 310 Cylinder

Claims (6)

A cylinder formed of a non-magnetic material in a cylindrical shape and enclosing a magnetorheological fluid whose viscosity changes by the action of a magnetic field;
A piston that is formed of a non-magnetic material and is slidably disposed in the cylinder with an interval through which the magnetorheological fluid can pass between the cylinder and the inner periphery of the cylinder;
A piston rod to which the piston is coupled;
A magnetorheological fluid shock absorber comprising a magnet for applying a magnetic field in the cylinder,
The cylinder has a tapered portion that is formed on at least one of an outer peripheral surface and an inner peripheral surface thereof and has a thickness that changes in a tapered shape toward the axial direction.
A magnetorheological fluid shock absorber, wherein the magnet is attached to an outer periphery of the cylinder corresponding to a position where the tapered portion is formed.   2. The magnetorheological fluid shock absorber according to claim 1, wherein the tapered portion is formed such that a thickness of the cylinder becomes thinner toward a direction in which the piston rod enters the cylinder.   3. The magnetorheological fluid shock absorber according to claim 1, wherein the tapered portion is formed to correspond to a position of the piston when the piston rod enters the cylinder most.   4. The magnetorheological fluid shock absorber according to claim 1, wherein the tapered portion is a tapered flat portion that is formed in a concave shape on an outer periphery of the cylinder and to which the magnet is attached. 5. The cylinder has a flat portion formed in a concave shape on the outer periphery thereof, to which the magnet is attached,
4. The magnetorheological fluid shock absorber according to claim 1, wherein the tapered portion is a tapered inner peripheral portion formed on an inner periphery of the cylinder. 5.   The taper portion includes a tapered flat surface portion that is formed in a concave shape on the outer periphery of the cylinder and to which the magnet is attached, and a tapered inner peripheral portion that is formed on the inner periphery of the cylinder. The magnetorheological fluid shock absorber according to any one of the above.

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