JP2007239982A - Magnetorheological fluid damper - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To simplify construction and simultaneously to enhance reliability by automatically making damping force vary in response to displacement of a piston and thus autonomously operating without providing a sensor sensing the displacement of the piston and a control device controlling a supply of electric power in a magnetorheological fluid damper. <P>SOLUTION: The magnetorheological fluid damper is configured so as to include magnetorheological fluid 8, a piston 2 made of a ferromagnet, a cylinder part 3 which encloses the magnetorheological fluid 8 and simultaneously houses the piston 2, a piston rod 4 which supports the piston 2 by penetrating the cylinder part 3, a magnetic field generator 6 which is provided outside the cylinder part 3, a first yoke material 5 which is disposed around the circumference of the cylinder part 3 and a second yoke material 7 which is disposed around the circumference of the piston rod 4 outside the cylinder part 3. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a magnetorheological fluid damper. More specifically, the present invention relates to a magnetorheological fluid damper suitable for use as, for example, a seismic isolation damper for a structure.

  As shown in FIG. 8, a conventional magnetorheological fluid damper includes a cylinder body 101 having a substantially cylindrical shape and closed at both ends, and a cylinder chamber of the cylinder body 101 that is fitted to the axis of the cylinder body 101. A piston head 102 that linearly reciprocates along, a first fluid chamber 103 and a second fluid chamber 104 defined in the cylinder body 101 by the piston head 102, and a first fluid chamber 103 and a second fluid. A magnetorheological fluid 105 containing magnetic particles filled in the chamber 104, an electromagnet 108 formed of a coil in which an electric wire is wound around a groove 102 a recessed in the outer periphery of the piston head 102, and an electromagnet 108 via a wiring 109. And an external power supply control device 110 that supplies electric power. To form a magnetic field, to increase the viscous resistance of the apparent magnetic viscous fluid 105 passing through the fluid passageway 107 there is known to adjust the damper damping force by the action of the magnetic field (Patent Document 1).

JP 2004-316797 A

  However, in the magnetorheological fluid damper 100 of Patent Document 1, in order to control and adjust the damping force of the damper, the displacement of the piston is determined based on a sensor that senses the displacement of the piston, such as the power supply control device 110, and the signal of the sensor. In addition, a control device that controls the power supplied to the electromagnet 108 in real time is required. For this reason, the structure of the damper becomes complicated and the control becomes complicated. In addition, it takes time to manufacture, and an external device is required in addition to the damper, leading to an increase in cost.

  Further, the magnetorheological fluid damper 100 of Patent Document 1 requires the transmission of a control command from the outside and the supply of electric power, and cannot operate independently while adjusting the damping force by the damper alone. Therefore, it is necessary to keep the control device in an always operating state (power-on state) regardless of whether or not it is operated, which is uneconomical when the standby state continues for a long time or operates continuously for a long time. . In addition, if the control command from the outside is cut off due to a failure or the power supply from the outside is cut off, the damping force cannot be adjusted, so that the predetermined performance cannot be exhibited, and the It cannot be said that the nature is high. For this reason, for example, a damping that is required to operate reliably against an unexpected earthquake and exhibit a predetermined performance while the standby state continues for a long period of time, such as a seismic isolation damper of a structure. It is difficult to say that it is suitable for application to a device or a damping device that requires continuous operation while exhibiting a predetermined performance, such as a suspension of an automobile.

  Therefore, the present invention does not require a sensor for detecting the displacement of the piston or a control device for controlling the supply of electric power, and can operate independently by automatically changing the damping force in accordance with the displacement of the piston. An object of the present invention is to provide a magnetorheological fluid damper that can be used.

  In order to achieve this object, a magnetorheological fluid damper according to a first aspect of the present invention includes a magnetorheological fluid, a ferromagnetic piston, a cylinder part that seals the magnetorheological fluid and accommodates the piston, and penetrates the cylinder part. A piston rod that supports the piston, a magnetic field generator provided outside the cylinder part, a first yoke material arranged around the cylinder part, and arranged around the piston rod outside the cylinder part The piston rod has a first yoke material together with the piston, the first yoke material, the magnetic field generator, and the second yoke material when the piston is displaced in one axial direction beyond the neutral region. When the ferromagnetic part and the piston that form the magnetic circuit of the piston move beyond the neutral region to the other of the axial direction, the second magnet together with the piston, the first yoke material, the magnetic field generator, and the second yoke material. A ferromagnetic part that forms a circuit, and a non-magnetic part that shuts off the first magnetic circuit and shuts off the second magnetic circuit when the piston is in the neutral region, between the piston and the cylinder. The magnetic flux density of the magnetic circuit passing through the gap changes in accordance with the axial displacement of the piston.

  Therefore, according to the magnetorheological fluid damper, when the magnetic field is generated by the magnetic field generator and the piston rod is displaced in the axial direction due to the excitation force applied to the piston rod, the second yoke material and the ferromagnetic portion of the piston rod The magnetic flux density of the magnetic circuit passing between the piston and the cylinder changes due to the change of the magnetic flux passing between the piston and the cylinder, and the magnitude of the magnetic field applied to the magnetorheological fluid in the gap portion between the piston and the cylinder Changes the apparent viscosity of the magnetorheological fluid.

  Specifically, when the displacement of the piston is in the neutral region, the non-magnetic portion of the piston rod faces the second yoke material, and a magnetic circuit is formed that passes between the piston and the first yoke material. Or the magnetic flux density is low, and the magnetic viscosity is hardly applied to the magnetorheological fluid in the vicinity of the piston peripheral surface, specifically, the gap between the piston outer peripheral surface and the cylinder chamber outer peripheral surface. Almost no change. Therefore, the damping effect is exhibited as a fluid damper having a damping force close to the damping force due to the original viscous resistance of the magnetorheological fluid in the same manner as a normal fluid damper. On the other hand, when the displacement of the piston is large and exceeds the neutral region, the second yoke material and the ferromagnetic portion of the piston rod approach or face each other, so that the magnetism passing between the piston and the first yoke material The magnetic flux density of the circuit increases and the magnetic field applied to the magnetorheological fluid near the piston peripheral surface increases. As a result, the apparent viscosity of the magnetorheological fluid in the vicinity of the piston peripheral surface increases and the damping force of the magnetorheological fluid damper increases, and the magnetorheological fluid damper exhibits a strong damping effect.

  Here, the neutral region includes a neutral position (a normal position when the piston is in a standby state without being displaced in the initial setting state), and when the magnetorheological fluid damper of the present invention is displaced. This is the range where the damping force close to the damping force due to the original viscous resistance of the magnetorheological fluid is exhibited as in the case of a normal fluid damper. This range is arbitrarily determined depending on the arrangement relationship between the second yoke material and the ferromagnetic portion of the piston rod.

  The magnetorheological fluid generally means a high-concentration suspension composed of ferromagnetic metal particles having a particle diameter of about 1 to 10 μm. However, in the present specification, the magnetorheological fluid is used to mean a fluid whose apparent viscosity varies depending on the magnitude of a magnetic field in which a ferromagnetic material is dispersed in a solution regardless of the particle diameter. Accordingly, a fluid in which a ferromagnetic material having a particle diameter of less than 1 μm is dispersed may be used, or a fluid in which a ferromagnetic material having a particle diameter of more than 10 μm is dispersed.

  According to a second aspect of the present invention, in the magnetorheological fluid damper according to the first aspect, a permanent magnet is used as the magnetic field generator. In this case, by using a permanent magnet, a magnetic field can be generated without receiving an external power supply.

  According to a third aspect of the present invention, in the magnetorheological fluid damper according to the first aspect, a solenoid is used as the magnetic field generator. In this case, a strong magnetic field can be generated with a small device by using a solenoid.

  According to the magnetorheological fluid damper according to claim 1, the magnetic flux density of the magnetic circuit formed in the fluid damper changes according to the displacement of the piston, and the gap portion between the piston outer peripheral surface and the cylinder chamber outer peripheral surface The apparent viscosity of the magnetorheological fluid can be changed automatically by changing the magnitude of the magnetic field applied to the magnetorheological fluid. Without using a control device that controls electric power, the damping force can be automatically changed according to the displacement of the piston to operate independently, and the structure, control and manufacturing of the fluid damper can be simplified. And cost reduction.

  According to this magnetorheological fluid damper, when the displacement of the piston is in the neutral region, a damping force close to the damping force due to the original viscous resistance of the magnetorheological fluid is exerted in the same manner as a normal fluid damper. When the displacement exceeds the neutral region, the apparent viscosity of the magnetorheological fluid in the vicinity of the piston peripheral surface increases and a large damping force is exhibited. Thus, this magnetorheological fluid damper exhibits a damping effect as a damper having a damping force as a mere fluid damper when the displacement amount of the piston is in the neutral region, and is large when the displacement amount of the piston exceeds the neutral region. Demonstrates strong damping effect as a damper with damping force. That is, it has a combination of two different types of damping forces and functions as a damper that exhibits two vibration damping effects.

  Further, although it is a damping force control type damper, a control device for controlling the electric power supplied to the magnetic field generator is not required, and therefore no electric power is required for controlling the damper damping force, so that economic efficiency can be improved.

  Furthermore, since it is a damping force control type damper, it can automatically operate by changing the damping force according to the displacement of the piston without receiving an external control command. Reliability can be improved.

  According to the magnetorheological fluid damper of claim 2, by using a permanent magnet as the magnetic field generating device, it is possible to generate a magnetic field without receiving external power supply. It can operate and can improve reliability. Further, since no electric power is required for controlling the damping force and generating the magnetic field, the economy can be improved.

  According to the magnetorheological fluid damper according to claim 3, by using a solenoid as the magnetic field generating device, it is possible to generate a strong magnetic field with a small device. Can generate strong damping force.

  Hereinafter, the configuration of the present invention will be described in detail based on the best mode shown in the drawings.

  1 to 4 show an example of the first embodiment of the magnetorheological fluid damper of the present invention. The magnetorheological fluid damper 1 includes a magnetorheological fluid 8, a ferromagnetic piston 2, a cylinder part 3 that seals the magnetorheological fluid 8 and accommodates the piston 2, and penetrates the cylinder part 3 to connect the piston 2. The piston rod 4 to be supported, the magnetic field generator 6 provided outside the cylinder portion 3, the first yoke material 5 disposed around the cylinder portion 3, and the periphery of the piston rod 4 outside the cylinder portion 3 And a second yoke material 7 disposed on the surface.

  The cylinder part 3 is formed in a hollow cylindrical shape having a hollow part (that is, a cylinder chamber) and having both end faces in the axial direction. A through hole for penetrating the piston rod 4 is provided at the center of both end faces of the cylinder part 3 in the axial direction. A sealing member 13 for supporting the piston rod 4 so as to be slidable and preventing leakage of the magnetorheological fluid 8 filled in the cylinder chamber of the cylinder portion 3 is provided on the periphery of the through hole.

  In addition, the shape of the cylinder part 3 is not restricted to a hollow cylindrical shape, For example, the shape of the axial cross section of the cylinder chamber of the cylinder part 3 may be an ellipse or a polygon. Moreover, the outer shape of the cylinder part 3 may be any shape.

  The cylinder portion 3 has a strength and durability usually required as a cylinder of a fluid damper, and has a sufficiently small permeability compared to a high permeability material such as a yoke material (hereinafter referred to as a low permeability material). For example, lead, copper, aluminum, or the like.

  The piston 2 only needs to be formed of a high magnetic permeability material having strength and durability normally required as a piston of a fluid damper. Specifically, the piston 2 is formed using, for example, iron or magnetic ceramic.

  The shape of the piston 2 is a shape matched to the axial section of the cylinder chamber of the cylinder portion 3, and is similar to that of a normal fluid damper between the outer peripheral surface of the piston 2 and the peripheral surface of the cylinder chamber of the cylinder portion 3. Any shape may be used as long as it forms a gap. In the present embodiment, the piston 2 is formed to have a circular axial cross section in accordance with the axial cross sectional shape of the cylinder chamber of the cylinder portion 3.

  The cylinder chamber of the cylinder portion 3 is divided by the piston 2 into a cylinder chamber 3 a and a cylinder chamber 3 b on both sides in the axial direction of the piston 2. The cylinder chamber 3 a and the cylinder chamber 3 b are connected by a fluid flow path 3 c that is a gap between the outer peripheral surface of the piston 2 and the peripheral surface of the cylinder chamber of the cylinder portion 3. The cross section of the fluid flow path 3c is smaller than the cross sections of the cylinder chamber 3a and the cylinder chamber 3b.

The piston rod 4 has a first magnetic circuit 9a together with the piston 2, the first yoke material 5, the magnetic field generator 6, and the second yoke material 7 when the piston 2 is displaced to the cylinder chamber 3a side beyond the neutral region. the with ferromagnetic portion 4a _1, and the piston 2 is a piston 2 and the first yoke member 5 and the magnetic field generator 6 when displaced to the cylinder chamber 3b side beyond the neutral region second yoke member 7 forming a A ferromagnetic part 4a ₂ forming the second magnetic circuit 9b, and a non-magnetic part 4b that shuts off the first magnetic circuit 9a and shuts off the second magnetic circuit 9b when the piston 2 is in the neutral region. having axially outwardly of the piston rod ferromagnetic portion 4a ₁ and 4a _2.

The piston rod ferromagnetic portions 4a ₁ and 4a ₂ only need to have a high magnetic permeability region. For example, the surface may be covered with a high magnetic permeability material (FIG. 4A). ) Or the whole may be made of a high permeability material (FIG. 4C). The piston rod nonmagnetic portion 4b only needs to have a region having a lower magnetic permeability than the piston rod ferromagnetic portions 4a ₁ and 4a ₂ , and preferably a nonmagnetic material is used. For example, the surface may be covered with a low magnetic permeability material (FIG. 4B), or the entire surface may be formed of a low magnetic permeability material (FIG. 4C). ). In the present embodiment, the piston 2 and the piston rod ferromagnetic portions 4a ₁ and 4a ₂ are integrally formed.

When the configuration of the piston rod ferromagnetic portions 4a ₁ and 4a ₂ is such that the surface is covered with a high magnetic permeability material (FIG. 4A), for example, the piston rod ferromagnetic portions 4a ₁ and 4a ₂ A female screw is formed inside the piston rod, and a male screw extending from the end surface is formed in the piston rod nonmagnetic portion 4b. Then, on both sides of the piston rod of the piston 2 which are integrally formed with the piston 2 ferromagnetic portions 4a ₁ and 4a ₂ is fitted the piston rod non-magnetic portion 4b is contemplated that integrally of the piston rod 4 is formed.

In the case where the entire piston rod ferromagnetic portions 4a ₁ and 4a ₂ are formed of a high permeability material and the entire piston rod nonmagnetic portion 4b is formed of a low permeability material (FIG. 4 ( C)) For example, a male screw protruding from the end face is formed in the piston rod ferromagnetic portions 4a ₁ and 4a ₂ and a female screw is formed in the end portion of the piston rod nonmagnetic portion 4b. Then, on both sides of the piston rod of the piston 2 which are integrally formed with the piston 2 ferromagnetic portions 4a ₁ and 4a ₂ is fitted the piston rod non-magnetic portion 4b is contemplated that integrally of the piston rod 4 is formed.

Furthermore, when the configuration of the piston rod nonmagnetic portion 4b is a configuration in which the surface is covered with a low magnetic permeability material (FIG. 4B), for example, the end surfaces on the piston rod ferromagnetic portions 4a ₁ and 4a ₂ A male screw extending from the inner side of the piston rod nonmagnetic portion 4b is formed. Then, on both sides of the piston rod of the piston 2 which are integrally formed with the piston 2 ferromagnetic portions 4a ₁ and 4a ₂ is fitted the piston rod non-magnetic portion 4b is contemplated that integrally of the piston rod 4 is formed.

The high magnetic permeability material forming the piston rod ferromagnetic portions 4a ₁ and 4a ₂ may be a high magnetic permeability material having the strength and durability normally required for a piston rod of a damper. Or magnetic ceramic is used. Furthermore, the low magnetic permeability material forming the piston rod nonmagnetic portion 4b may be a low magnetic permeability material having strength and durability normally required for a piston rod of a damper. Specifically, for example, lead, copper Aluminum or the like is used.

  In the present embodiment, the first yoke material 5 is formed in a hollow cylindrical shape having a hollow portion 5a and having both end faces in the axial direction. A through hole is provided in the central portion of both end faces in the axial direction of the first yoke material 5 for supporting and penetrating the piston rod 4 slidably. The first yoke material 5 may be formed in a hollow cylindrical shape as a whole by combining, for example, a cylindrical portion covering the outer periphery of the cylinder portion 3 and cap portions on both sides thereof. Thereby, the assembly of the fluid damper can be simplified.

  The first yoke material hollow portion 5a is formed so that the outer peripheral surface of the cylinder portion 3 and the peripheral surface of the first yoke material hollow portion 5a are in contact with each other. Furthermore, it is formed so as to have spaces for accommodating the magnetic field generator 6 and the second yoke material 7 on both axial sides of the cylinder portion 3.

  The second yoke material 7 is formed in an annular shape having a through hole in the central portion through which the piston rod 4 is slidably penetrated. The second yoke material 7 is disposed on both sides of the cylinder portion 3 in the axial direction.

  The magnetic field generator 6 is formed in an annular shape having a through-hole through which the piston rod 4 penetrates at the center so that the magnetic field generator 6 and the piston rod 4 do not contact each other. And the magnetic field generator 6 is arrange | positioned at the axial direction both sides of the cylinder part 3, and is provided in contact with the end surface of the 2nd yoke material 7 and the axial direction of the 1st yoke material hollow part 5a in this embodiment. It is done.

The radius of the axial cross section of the magnetic field generator 6 and the second yoke material 7 is set smaller than the radius of the axial cross section of the first yoke material hollow portion 5a. As a result, the piston 2, the first yoke material 5, the magnetic field generator 6, and the first yoke material hollow portion 5a are disposed between the peripheral surface of the first yoke material hollow portion 5a and the outer peripheral surfaces of the magnetic field generator 6 and the second yoke material 7. A gap 10 is formed for forming magnetic circuits 9a and 9b in which the second yoke member 7 and the piston rod ferromagnetic portions 4a ₁ and 4a ₂ are connected.

  The magnetic field generator 6 may be formed of a material that generates a magnetic field or any device that generates a magnetic field. In the present embodiment, a permanent magnet is used as the magnetic field generator 6. The second yoke material 7 may be any material having a high magnetic permeability. Specifically, for example, iron or magnetic ceramic is used.

The total axial length of the piston 2 and the piston rod ferromagnetic portion 4a ₁ and 4a ₂ is that the piston 2 is in contact with the piston rod ferromagnetic portion 4a _1, 4a ₂ second yoke member 7 when in the neutral region If the displacement amount of the piston 2 exceeds the neutral region, the length of the piston rod ferromagnetic portions 4a ₁ and 4a ₂ contacting the second yoke material 7 is set. It should be noted that by adjusting the total axial length of the piston 2 and the piston rod ferromagnetic portions 4a ₁ and 4a ₂ with respect to the interval between the second yoke members 7 arranged on both sides in the axial direction of the cylinder portion 3, the magnetorheological fluid damper The range in which 1 exhibits a damping force close to the damping force due to the original viscous resistance of the magnetorheological fluid, that is, the width of the neutral region can be adjusted. Specifically, when the total length is increased, a strong damping force is exerted even when the displacement amount of the piston 2 is small. Conversely, when the total length is shortened, the piston 2 is strong only when the displacement amount of the piston 2 is large. Demonstrates damping force.

  When the piston 2 and the piston rod 4 are accommodated, the cylinder chambers 3a and 3b and the fluid flow path 3c formed in the cylinder portion 3 are filled with the magnetorheological fluid 8. The magnetorheological fluid 8 includes microscale ferromagnetic particles, and the viscosity changes in response to the strength of the magnetic field. That is, when the magnetic field is applied, the apparent viscosity increases, and when the magnetic field is removed, the apparent viscosity returns. In general, the larger the particle size of the ferromagnetic material dispersed in the fluid, the smaller the change in shearing stress, so the change in damping force due to the application of a magnetic field is relatively small. By changing the particle size of the ferromagnetic material to be dispersed in the magnetorheological fluid 8 by the above, it is possible to provide an appropriate fluid damper according to the expected damping force.

  The operation of the magnetorheological fluid damper 1 of the first embodiment described above will be described below.

As shown in FIG. 2A, when the piston 2 is in the neutral position, the second yoke member 7 and the piston rod ferromagnetic portions 4a ₁ and 4a ₂ are separated from each other, and the piston rod nonmagnetic portion 4b is in the second position. It becomes a gap of a path for magnetic flux between the yoke material 7 and the piston rod ferromagnetic portions 4a ₁ and 4a ₂ . Therefore, the magnetic circuit 9a, whether or flux density not 9b is formed with the magnetic field generation device 6 second yoke member 7 and the piston rod ferromagnetic portion 4a _1, 4a ₂ and the piston 2 and the first yoke member 5 is contiguous Is low. Accordingly, as shown in FIG. 3A, since the magnetic field is hardly applied to the magnetorheological fluid 8 in the fluid flow path 3c, the apparent viscosity of the magnetorheological fluid 8 hardly changes. At this time, a magnetic circuit that does not pass through the piston rod 4 and the piston 2, that is, a magnetic circuit in which the magnetic field generator 6, the first yoke material 5, and the second yoke material 7 are connected is formed. In this state, the magnetorheological fluid damper 1 functions as a fluid damper having a damping force close to the damping force due to the original viscous resistance of the magnetorheological fluid 8. In FIG. 3, the direction of the arrow 11 in the drawing represents the direction of the magnetic field at the starting point of the arrow, and the length of the arrow 11 represents the strength of the magnetic field.

  In this state, when the excitation force in the direction of the arrow 20 is applied to the piston rod 4, the piston rod 4 and the piston 2 are displaced in the direction of the arrow 20. At this time, in accordance with the displacement of the piston 2, the magnetorheological fluid 8 flows from the cylinder chamber 3a through the fluid flow path 3c to the cylinder chamber 3b. At this time, when the piston 2 is in the neutral position, no magnetic field is applied to the magnetorheological fluid 8 in the fluid flow path 3c and the apparent viscosity hardly changes. Therefore, in the initial stage of displacement of the piston 2, the magnetorheological fluid The damper 1 exhibits a damping effect as a fluid damper having a damping force close to the damping force due to the original viscous resistance of the magnetorheological fluid 8.

When the piston rod 4 and the piston 2 are further displaced in the direction i.e. the cylinder chamber 3a side of the arrow 20, as shown in FIG. 2 (B), the piston rod ferromagnetic portion 4a ₁ from the cylinder portion 3 protrudes second yoke The magnetic flux easily passes between the second yoke material 7 and the piston rod ferromagnetic portion 4a ₁ by entering the through hole at the center of the material 7. For this reason, the magnetic flux density of the magnetic circuit 9a becomes high. As a result, a strong magnetic field is applied to the magnetorheological fluid 8 in the fluid flow path 3c portion (FIG. 3B), the apparent viscosity of the magnetorheological fluid 8 increases, and the damping force of the magnetorheological fluid damper 1 increases. The magnetorheological fluid damper 1 exhibits a strong vibration damping effect.

Further, when the piston rod 4 and the piston 2 are largely displaced in the direction of the arrow 20 ′, that is, toward the cylinder chamber 3b, the piston rod ferromagnetic portion 4a ₂ protrudes from the cylinder portion 3 as shown in FIG. easily passes the magnetic flux between the second yoke member 7 and the piston rod ferromagnetic portion 4a ₂ enters the through hole in the central portion of the yoke member 7. For this reason, the magnetic flux density of the magnetic circuit 9b becomes high. As a result, a strong magnetic field is applied to the magnetorheological fluid 8 in the fluid flow path 3c, the apparent viscosity of the magnetorheological fluid 8 increases, the damping force of the magnetorheological fluid damper 1 increases, and the magnetorheological fluid damper 1 Demonstrates strong vibration control effect.

As described above, the magnetorheological fluid damper 1 of the present invention exhibits a damping force close to the damping force due to the original viscous resistance of the magnetorheological fluid 8 when the displacement of the piston is small at the time of a slight vibration. Therefore, it works as a fluid damper that efficiently reduces the acceleration response. As the vibration amplitude increases, the displacement of the piston 2 gradually increases, and the piston rod ferromagnetic portions 4a ₁ and 4a ₂ come closer to the second yoke member 7, and accordingly the fluid flow path 3c portion. The magnetic viscosity applied to the magnetorheological fluid 8 gradually becomes stronger, and it acts as a fluid damper in which the damping force gradually increases as the apparent viscosity of the magnetorheological fluid 8 increases. Further, when the displacement of the piston is large at the time of vibration with a large amplitude, the piston rod ferromagnetic portions 4a ₁ and 4a ₂ enter the second yoke member 7 in a large amount, and the magnetorheological fluid in the fluid flow path 3c portion. A strong magnetic field is applied to 8, and the apparent viscosity of the magnetorheological fluid 8 is increased to exert a strong damping force to act as a fluid damper that suppresses large deformation. As a result, the magnetorheological fluid damper 1 of the present invention exhibits a strong damping force suddenly even when a large excitation force is applied to the piston rod 4, and gradually reduces the damping force rather than performing a large impact control. In addition to exerting a smooth vibration damping effect, a strong damping force is exerted by exhibiting a strong damping force when the excitation force applied to the piston rod 4 is large and the displacement of the piston 2 is large.

  In addition, although the above-mentioned form is an example of the suitable form of this invention, it is not limited to this, A various deformation | transformation implementation is possible in the range which does not deviate from the summary of this invention. For example, in the present embodiment, since the magnetorheological fluid 8 is sealed by the cylinder portion 3, the first yoke material 5 does not need to seal the magnetorheological fluid 8. Therefore, the first yoke material 5 may have any shape as long as it forms part of the magnetic circuits 9a and 9b between the piston 2 and the magnetic field generator 6. Specifically, for example, a streaky yoke material may be attached around the cylinder portion 3 in the axial direction. In this case, the damping force of the fluid damper can be adjusted by changing the arrangement interval and number of yoke members, the size of the cross section, and the like, thereby adjusting the degree of formation of the magnetic circuit.

In the present embodiment, the piston rod 4 is composed of only the ferromagnetic portions 4a ₁ and 4a ₂ having high magnetic permeability and the nonmagnetic portion 4b having low magnetic permeability, but the ferromagnetic portions 4a ₁ , 4a ₂ and may be provided with a portion with a permeability between the magnetic permeability of the magnetic permeability and the non-magnetic portion 4b of the ferromagnetic portion 4a _1, 4a ₂ between the non-magnetic portion 4b. Further, the magnetic permeability of the piston rod 4 may be gradually lowered from the side closer to the piston 2 toward the far side. It is possible to adjust the damping force of the magnetorheological fluid damper 1 by adjusting the change in the magnetic permeability of the piston rod 4.

  In the present embodiment, a permanent magnet is used as the magnetic field generator 6, but a solenoid (a DC coil or an AC coil) can be used instead of the permanent magnet. In this case, there is an advantage that the magnetorheological fluid damper 1 can be downsized and a strong magnetic field can be generated to exert a stronger damping force compared to the case where a permanent magnet is used.

  Next, FIG. 5 shows an example of the second embodiment of the magnetorheological fluid damper of the present invention. In the first embodiment, the constituent member of the cylinder portion 3 and the first yoke material 5 disposed around the cylinder portion 3 are configured as separate members. On the other hand, in the second embodiment, the constituent member of the cylinder portion 3 and the first yoke material 5 are made of the same member. Specifically, the cylinder portion 3 is formed by the first yoke member 5 formed in a hollow cylindrical shape having the hollow portion 5a and having both end faces in the axial direction, and the two partition walls 12 in the hollow portion 5a. .

  When the constituent members of the cylinder portion 3 and the first yoke material 5 are formed of the same member as in the present embodiment, the cylinder portion 3 itself is part of the magnetic circuit as the first yoke material 5. And the first yoke member 5 serves to seal the magnetorheological fluid 8 as a part of the cylinder portion 3.

  The partition wall 12 may be formed of a low magnetic permeability material having strength and durability normally required as a component of the fluid damper, and specifically, for example, formed of lead, copper, aluminum, or the like. . A through hole for penetrating the piston rod 4 is provided in the center of the partition wall 12. The piston rod 4 is slidably supported on the periphery of the through-hole, and the cylinder chamber of the cylinder portion 3 (specifically, in this embodiment, both the partition walls 12 of the first yoke material hollow portion 5a). A sealing member 13 is provided to prevent leakage of the magnetorheological fluid 8 in the space between the two.

  FIG. 6 shows an example of the third embodiment of the magnetorheological fluid damper of the present invention. Also in this embodiment, the constituent member of the cylinder portion 3 and the first yoke material 5 are constituted by the same member. In this embodiment, the sealing member 13 provided at the periphery of the through-hole for penetrating the piston rod 4 at the center of both axial end faces of the cylinder portion 3 has a low permeability to prevent formation of a magnetic circuit that does not pass through the piston 2. Made of magnetic material.

  In this embodiment, the magnetic field generator 6 is disposed on both sides in the axial direction of the cylinder part 3 and is provided in contact with the end face of the cylinder part 3 in the axial direction.

  Further, a gap 10 ′ between the inner peripheral surface of the central through hole of the magnetic field generator 6 and the outer peripheral surface of the piston rod 4 is a space for forming a magnetic circuit together with the sealing member 13 and the cylinder chambers 3 a and 3 b. Become.

  FIG. 7 shows an example of the fourth embodiment of the magnetorheological fluid damper of the present invention. Also in this embodiment, the constituent member of the cylinder portion 3 and the first yoke material 5 are constituted by the same member. In this embodiment, a single rod 4 ′ that passes through the end face on one axial side of the cylinder portion 3 and supports the piston 2 from one side is used. Note that the end surface of the cylinder portion 3 opposite to the end surface through which the single rod 4 'passes is closed. In addition, the magnetorheological fluid damper 1 using the single rod 4 'corresponds to a change in the volume of the single rod 4' entering the cylinder portion 3 in the same manner as a normal cantilever cylinder. An accumulator 14 partitioned by a free piston 14a is provided in the room.

In this embodiment, as shown in FIG. 7 (B), the single rod 4 ′ has the first rod 2 'when the piston 2 is displaced in the direction of the arrow 20 beyond the neutral region, that is, toward the cylinder chamber 3a. The piston rod ferromagnetic portions 4a ₁ , 4a ₂ and 4a ₃ forming the first magnetic circuit 9a together with the yoke material 5, the magnetic field generator 6 and the second yoke material 7 as shown in FIG. When the piston 2 moves beyond the neutral region in the direction of the arrow 20 ′, that is, toward the cylinder chamber 3 b, the second magnet together with the piston 2, the first yoke material 5, the magnetic field generator 6, and the second yoke material 7. and a piston rod ferromagnetic portion 4a ₃ forming the circuit 9b.

Further, the single rod 4 'becomes a magnetic flux passage gap between the second yoke member 7 and the piston rod ferromagnetic portions 4a ₁ , 4a ₂ and 4a ₃ when the piston 2 is in the neutral region. as such, having a piston rod non-magnetic portion 4b between the piston rod ferromagnetic portion 4a ₁ and the piston rod ferromagnetic portion 4a _3.

Furthermore, the piston rod ferromagnetic portions 4a ₁ and 4a ₃ and the piston rod nonmagnetic portion 4b are arranged such that when the piston 2 is in the neutral region, the piston rod ferromagnetic portions 4a ₁ , 4a ₃ are used as the second yoke material 7. The piston rod ferromagnetic portions 4a ₁ and 4a ₃ are set so as to be in contact with the second yoke member 7 when the displacement amount of the piston 2 exceeds the neutral region.

  By configuring the single rod 4 ′ as described above, the magnetic circuit 9a is disposed in the fluid damper except for the neutral region, regardless of which direction the piston 2 is displaced from the neutral position, even though it is a single rod damper. 9b and the magnetic flux density of the magnetic circuits 9a, 9b can be changed, so that the strength of the magnetic field applied to the magnetorheological fluid 8 in the fluid flow path 3c portion according to the magnitude of the displacement of the piston 2 can be changed. The damping force of the magnetorheological fluid damper 1 can be changed by changing the apparent viscosity of the magnetorheological fluid 8 and changing the apparent viscosity of the magnetorheological fluid 8.

It is sectional drawing which shows an example of 1st embodiment of the magnetorheological fluid damper of this invention. It is sectional drawing explaining operation | movement of the magnetorheological fluid damper of 1st embodiment. (A) is sectional drawing which shows the state which the piston has not displaced. (B) is sectional drawing which shows the state which the piston displaced to one side exceeding the neutral region. (C) is sectional drawing which shows the state which the piston displaced to the other beyond a neutral area | region. It is sectional drawing which shows magnetic field distribution of the magnetorheological fluid damper of 1st embodiment. (A) is sectional drawing which shows magnetic field distribution when a piston is not displaced. (B) is a sectional view showing the magnetic field distribution when the piston is displaced beyond the neutral region. It is sectional drawing explaining the structure of a piston rod. (A) is sectional drawing in the case of the structure where the surface of a piston rod ferromagnetic part is covered with the high magnetic permeability material. (B) is sectional drawing in the case of the structure where the surface of the piston rod nonmagnetic part is covered with the low magnetic permeability material. (C) is a cross-sectional view in the case of a structure in which the entire piston rod ferromagnetic portion is formed of a high permeability material and the entire piston rod nonmagnetic portion is formed of a low permeability material. It is sectional drawing which shows an example of 2nd embodiment of the magnetorheological fluid damper of this invention. It is sectional drawing which shows an example of 3rd embodiment of the magnetorheological fluid damper of this invention. It is sectional drawing which shows an example of 4th embodiment of the magnetorheological fluid damper of this invention. (A) is sectional drawing which shows the state which the piston has not displaced. (B) is sectional drawing which shows the state which the piston displaced to one side exceeding the neutral region. (C) is sectional drawing which shows the state which the piston displaced to the other beyond a neutral area | region. It is sectional drawing which shows the conventional magnetorheological fluid damper.

Explanation of symbols

1 magneto-rheological fluid damper 2, 2a, 2b the piston 3 cylinder 4 piston rod 4 'single rod _{4a 1,} 4a 2, 4a ₃ piston rod ferromagnetic portion 4b the piston rod non-magnetic portion 5 first yoke member 6 magnetic field generator 7 Second yoke material 8 Magnetorheological fluid 9a First magnetic circuit 9b Second magnetic circuit

Claims (3)

  A magnetorheological fluid; a ferromagnetic piston; a cylinder that seals the magnetorheological fluid and accommodates the piston; a piston rod that passes through the cylinder and supports the piston; and an outside of the cylinder The first yoke material disposed around the cylinder portion, and the second yoke material disposed around the piston rod outside the cylinder portion, The piston rod has a first magnetic circuit together with the piston, the first yoke material, the magnetic field generator, and the second yoke material when the piston is displaced in one axial direction beyond the neutral region. When the ferromagnetic part to be formed and the piston are displaced in the axial direction beyond the neutral region, the piston, the first yoke material, the magnetic field generator, and the second yaw A ferromagnetic part that forms a second magnetic circuit with the material, and a non-magnetic part that shuts off the first magnetic circuit and shuts off the second magnetic circuit when the piston is in the neutral region. A magnetorheological fluid damper, wherein a magnetic flux density of a magnetic circuit passing through a gap between the piston and the cylinder changes according to an axial displacement of the piston.   The magnetorheological fluid damper according to claim 1, wherein a permanent magnet is used as the magnetic field generator. The magnetorheological fluid damper according to claim 1, wherein a solenoid is used as the magnetic field generator.

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