JP5969943B2 - Magnetorheological fluid shock absorber and front fork - Google Patents

Description

  The present invention relates to improvements in a magnetorheological fluid damper and a front fork.

  In general, the shock absorber attenuates vibrations of a vehicle, equipment, structure, or the like. Among such shock absorbers, there are magnetic viscous fluid shock absorbers that use a magnetorheological fluid whose viscosity is changed by the action of a magnetic field as a working fluid (for example, Patent Documents 1 and 2).

  For example, as shown in FIG. 2, the magnetorheological fluid shock absorber D2 disclosed in Patent Document 1 is set to a single cylinder type, and includes a cylindrical cylinder 100 and a piston rod 200 that enters and exits the cylinder 100. The piston 300 that is held at the tip of the piston rod 200 and that defines the rod side chamber r1 and the piston side chamber r2 formed in the cylinder 100 and the rod 300 that is formed in the piston 300 and communicates with the piston side chamber r2. A piston passage L1, an air chamber r3 that is formed in the cylinder 100 and compensates for a change in the internal volume of the piston rod that enters and exits the cylinder 100, and a piston side chamber r2 and an air chamber that are in sliding contact with the inner peripheral surface of the cylinder 100 free piston 500 that divides r3, and the rod side chamber r1 and the piston side chamber r2 are used as working fluids. Air viscous fluid is filled, gas compressed in the air chamber r3 is filled.

  Further, the magnetorheological fluid buffer D2 includes a viscosity adjusting unit 400 that adjusts the viscosity of the magnetorheological fluid passing through the piston passage L1, and the viscosity adjusting unit 400 includes a coil provided in the piston 300, and the coil. And an energizing means for energizing the. When a current is passed through the coil by the energizing means, a magnetic field is generated in the piston passage L1, and the viscosity of the magnetorheological fluid flowing through the piston passage L1 can be adjusted. The damping force generated when the magnetorheological fluid shock absorber D2 expands and contracts is caused by the resistance when the magnetorheological fluid in the chamber pressurized by the piston 300 passes through the piston passage L1 and moves to the other chamber. Since the resistance varies depending on the viscosity of the magnetorheological fluid, the damping force of the magnetorheological fluid buffer D2 can be adjusted by the viscosity adjusting unit 400.

JP 2008-12959 A JP 2008-175369 A

  Hereinafter, assuming that the damping force generated when the shock absorber extends is the expansion side damping force, and the damping force generated when the shock absorber is compressed is the compression side damping force, for example, the magnetorheological fluid shock absorber D2 is applied to a straddle-type vehicle such as a two-wheeled vehicle. In the case of use, it is preferable that the compression side damping force is lowered and push-up input is performed and a high elongation side damping force is exhibited in the subsequent extension step. By adopting such damping characteristics (change in damping force with respect to piston speed), the thrust input is absorbed by the suspension spring arranged in parallel with the shock absorber, and the expansion and contraction motion of the suspension spring accompanying the absorption of this thrust input is absorbed by the shock absorber. Can quickly converge.

  However, according to the configuration of the conventional magnetorheological fluid shock absorber D2, when the amount of current flowing through the coil is the same, the extension side damping force and the compression side damping force are substantially the same. The amount of current flowing through the coil is smaller when the compression side damping force is generated than when the expansion side damping force is generated. For this reason, if an attempt is made to manage the extension side damping force and the compression side damping force with the same degree of accuracy (for example, ± 5%, etc.), the error in the current value when the compression side damping force is generated compared to when the extension side damping force is generated. Is narrowed, and the current control accuracy in one shock absorber is different between expansion and compression. In addition, when a constant current flows through the coil during a failure such as a failure, the extension side damping force and the compression side damping force may be the same, and the ride quality of the vehicle may be greatly impaired.

  Accordingly, an object of the present invention is to increase the extension side damping force and lower the compression side damping force even when the amount of current flowing through the coil is the same, and further, a constant current is applied to the coil during a failure such as a failure. It is an object of the present invention to provide a magnetorheological fluid shock absorber that does not significantly impair the riding comfort of a vehicle even if it flows.

  Means for solving the above-described problems are a cylindrical cylinder, a piston rod that enters and exits the cylinder, and a rod-side chamber and a piston-side chamber that are held at the tip of the piston rod and formed in the cylinder. A piston, a magnet-viscous fluid whose viscosity is changed by the action of a magnetic field and filled in the rod-side chamber and the piston-side chamber, a piston passage formed in the piston and communicating the rod-side chamber and the piston-side chamber, and the piston Viscosity adjusting means for adjusting the viscosity of the magnetorheological fluid passing through the passage, and a free piston that divides the air chamber for compensating for the change in the cylinder volume corresponding to the volume of the piston rod entering and exiting the cylinder into the cylinder, The viscosity adjusting means includes a magnetic viscous flow including a coil that generates a magnetic field in the piston passage when energized. In the shock absorber, a cylindrical case disposed on the outer periphery of the cylinder and forming an outer peripheral passage with the cylinder, a base rod standing on the side opposite to the piston rod of the cylinder, and the rod formed on the cylinder A through hole communicating with the side chamber and the outer peripheral passage, a base passage formed in the base rod and communicating with the piston side chamber and the outer peripheral passage, and the piston side chamber of the magnetorheological fluid passing through the base passage. A valve that allows only flow to the outer peripheral passage, and the free piston is formed in an annular shape and slidably contacts the inner peripheral surface of the cylinder and the outer peripheral surface of the base rod, and the piston side chamber and the air That the room is separated.

  According to the magnetorheological fluid shock absorber of the present invention, it is possible to increase the extension side damping force and reduce the compression side damping force even when the amount of current flowing through the coil is the same. Furthermore, even if a constant current flows through the coil during a failure such as a failure, the riding comfort of the vehicle is not significantly impaired.

It is the front view which notched and showed the magnetorheological fluid buffer which concerns on one embodiment of this invention partially. It is a schematic sectional drawing of the conventional magnetorheological fluid shock absorber.

  Hereinafter, a magnetorheological fluid shock absorber according to an embodiment of the present invention will be described with reference to the drawings. The same reference numerals given throughout the several drawings indicate the same or corresponding parts.

  As shown in FIG. 1, a magnetorheological fluid shock absorber D1 according to the present embodiment includes a cylindrical cylinder 1, a piston rod 2 that enters and exits the cylinder 1, and a piston rod 2 that is held at the tip of the piston rod 2. A piston 3 that defines a rod-side chamber r1 and a piston-side chamber r2 formed in the cylinder 1; a magnetorheological fluid that is filled in the rod-side chamber r1 and the piston-side chamber r2 and whose viscosity changes due to the action of a magnetic field; and the piston 3, a piston passage L1 communicating with the rod side chamber r1 and the piston side chamber r2, a viscosity adjusting means 4 for adjusting the viscosity of the magnetorheological fluid passing through the piston passage L1, and the cylinder 1 A free piston 5 that divides the inside of the cylinder 1 into an air chamber r3 that compensates for the change in the cylinder volume corresponding to the piston rod volume The viscosity control unit 4 is provided with a coil 40 for generating a magnetic field to said piston passage L2 when energized.

  Further, the magnetorheological fluid shock absorber D1 stands on the cylindrical case 6 which is disposed on the outer periphery of the cylinder 1 and forms an outer peripheral passage L2 between the cylinder 1 and the anti-piston rod side of the cylinder 1. A base rod 7, a through hole L3 formed in the cylinder 1 for communicating the rod side chamber r1 and the outer peripheral passage L2, and a piston rod chamber r2 formed in the base rod 7 for communicating the outer peripheral passage L2. And a check valve (valve) V that allows only the flow of the magnetorheological fluid passing through the base passage L4 from the piston side chamber r2 to the outer peripheral passage L2. The free piston 5 is formed in an annular shape, is in sliding contact with the inner peripheral surface of the cylinder 1 and the outer peripheral surface of the base rod 7, and partitions the piston-side chamber r2 and the air chamber r3.

  The magnetorheological fluid shock absorber D1 is used for a front fork that suspends a front wheel in a straddle-type vehicle such as a two-wheeled vehicle or a three-wheeled vehicle. Since the structure of this front fork is well-known, it is not shown in detail, but a pair of shock absorbers standing on both sides of the front wheel (only the magnetorheological fluid shock absorber D1 which is one shock absorber is illustrated, and the other shock absorber is illustrated. (Not shown). Each of the pair of shock absorbers includes a telescopic shock absorber body T composed of an outer tube t1 and an inner tube t2, and can extend and contract as the inner tube t2 enters and leaves the outer tube t1. In the present embodiment, the outer tubes t1 of both shock absorbers are connected via a vehicle body side bracket (not shown), connected to a vehicle body frame serving as a skeleton of the vehicle body via the vehicle body side bracket, and the inner of each shock absorber. The tube t2 is connected to the axle of the front wheel via a wheel side bracket 8 attached to the lower end portion thereof. That is, in the present embodiment, the front fork is set upside down, but the inner tube t2 is connected to the vehicle body side and the outer tube t1 is connected to the wheel side and is set upright. Also good.

  In the present embodiment, one of the pair of shock absorbers is the magnetorheological fluid shock absorber D1 according to the present invention shown in FIG. 1, and the other shock absorber is a conventional single-cylinder magnetorheological fluid. The shock absorber D2 is accommodated in the shock absorber body T. For this reason, although detailed explanation about the other shock absorber is omitted, the extension side damping force and the compression side damping force generated by the other shock absorber are substantially the same as in the conventional magnetorheological fluid shock absorber D2. . The configuration of the other shock absorber is not limited to the above, and the configuration can be appropriately selected.

  Hereinafter, the magnetorheological fluid shock absorber D1 according to the embodiment of the present invention which is one shock absorber constituting the front fork will be described in detail. As described above, the magnetorheological fluid buffer D1 includes the cylindrical cylinder 1, the piston rod 2 that enters and exits the cylinder 1, the piston 3 that is held at the tip of the piston rod 2, and the outer periphery of the cylinder 1. A cylindrical case 6 disposed on the cylinder 1, a base rod 7 standing on the side opposite to the piston rod of the cylinder 1, and a free piston 5 provided on the outer periphery of the base rod 7 to divide the air chamber r 3 into the cylinder 1. These are accommodated in the shock absorber main body T.

  As described above, the shock absorber main body T is a telescopic type including the outer tube t1 and the inner tube t2 that enters and exits the outer tube t1, and the upper opening in FIG. The lower opening in FIG. 1 is closed by the wheel side bracket 8, and the lower opening in FIG. 1 of the cylindrical gap formed between the overlapping portions of the outer tube t1 and the inner tube t2 is closed by the seal member C1. Therefore, the inside of the shock absorber main body T is partitioned from the outside air side, so that the liquid or gas stored in the shock absorber main body T does not leak to the outside air side. The cylindrical gap is provided with a pair of annular bushes B1 and B2 that pivotally support the inner tube t2 that goes in and out of the outer tube t1. Further, between the shock absorber main body T and the case 6, lubricating oil for lubricating the sliding surfaces of the bushes B1 and B2 is stored, and the magnetorheological fluid shock absorber D1 is attached in the extending direction. A suspension spring S that elastically supports the vehicle body is accommodated.

  The cylinder 1 and the case 6 are fixed to the wheel side bracket 8 so as to be coaxial with the axial center of the inner tube t2, and the wheel side portion of the magnetorheological fluid shock absorber D1 has a triple tube structure. Specifically, the wheel-side bracket 8 is formed in a bottomed cylindrical shape, and the lower portion of the inner tube t2 is screwed to the inner periphery of the upper opening portion 8a of the wheel-side bracket 8, and the inner tube t2 The wheel side bracket 8 is sealed with an annular O-ring (not shown). A base rod 7 is fixed to the bottom 8b of the wheel side bracket 8 with a bolt 80, and the cylinder 1 and the case 6 are screwed into the base rod 7 and between the cylinder 1 and the base rod 7 and The case 6 and the base rod 7 are sealed with an annular O-ring (not shown).

  An annular rod guide 10 is fixed to the upper opening portion 1 a of the cylinder 1, and an annular sealing member 60 stacked on the rod guide 10 is fixed to the upper opening portion 6 a of the case 6. In addition, the piston rod 2 passes through the axial center portion of the rod guide 10 and the sealing member 60. The cylinder 1 and the rod guide 10 and the case 6 and the sealing member 60 are sealed with annular O-rings (not shown), respectively, and between the rod guide 10 and the piston rod 2 and the seal. The gap between the stop member 60 and the piston rod 2 is sealed with seal members C2, C3 and C4, respectively.

  That is, since the upper and lower openings of the cylinder 1 and the case 6 are closed by the above configuration, the magnetorheological fluid accommodated in the cylinder 1 and the case 6 does not leak to the outside, and the magnetorheological fluid is absorbed by the shock absorber body T and the case. 6 so as not to be mixed with lubricating oil accommodated between the two. The configuration for enclosing the magnetorheological fluid in the cylinder 1 or the case 6 is not limited to the above, and can be changed as appropriate.

  The piston rod 2 penetrating the rod guide 10 and the sealing member 60 is held in a state of being suspended from the cap member 9, and stands on the axial center portion of the outer tube t1. Further, the lower side of the piston rod 2 in FIG. 1 is pivotally supported by an annular bush B 3 fitted to the inner periphery of the rod guide 10 so as to be movable in the axial direction, and goes into and out of the cylinder 1. The piston rod 2 is formed in a cylindrical shape, and a wiring 41 for passing a current through a coil 40 (described later) constituting the viscosity adjusting means 4 passes through the piston rod 2. The piston 3 is held at the tip of the piston rod 2, and a rebound cushion 20 made of an elastic body is provided between the piston 3 and the rod guide 10 on the outer periphery of the piston rod 2. The rebound cushion 20 can absorb the shock when the magnetorheological fluid shock absorber D1 is extended most. The rebound cushion 20 of the present embodiment is made of rubber, but may be made of other members such as a coil spring having elasticity and an impact absorbing function.

  The piston 3 includes a piston assembly 30 that is screwed onto the outer periphery of the tip of the piston rod 2, an annular ring 31 that is disposed on the outer periphery of the piston assembly 30 and forms a piston passage L <b> 1 between the piston assembly 30, and the ring 31. Are provided with an annular plate 32 and a nut 33 for connecting the piston assembly 30 to the piston assembly 30. The piston assembly 30 and the ring 31 are both formed of a magnetic material, and the piston passage L1 is formed of an annular gap formed between the piston assembly 30 and the ring 31. Further, a hole (not shown) penetrating vertically is formed in the plate 32 so that the plate 32 does not hinder communication between the rod side chamber r1 and the piston side chamber r3 in the piston passage L1.

  The viscosity of the magnetorheological fluid passing through the piston passage L1 can be adjusted by the viscosity adjusting means 4. The viscosity adjusting means 4 includes a coil 40 wound around the outer periphery of the piston assembly 30 and an energizing means for energizing the coil 40. The energizing means is not shown in the figure, which can adjust the amount of current flowing through the coil 40. A controller and a wiring 41 that connects the controller and the coil 40 are provided, and a magnetic field can be generated in the piston passage L1 by energizing the coil 40. Since the controller is provided outside the shock absorber main body T, a part 41 a of the wiring 41 extends outside the shock absorber main body T through the inside of the piston rod 2. The amount of current flowing through the coil 40 can be adjusted in multiple steps or steplessly by the controller.

  A magnetorheological fluid is a liquid in which fine particles having ferromagnetism are dispersed in a liquid such as oil, and the viscosity is increased by the action of a magnetic field. The viscosity of the magnetorheological fluid changes according to the strength of the magnetic field and returns to the original state when the magnetic field is removed. The magnetorheological fluid includes a rod side chamber r1 formed in the cylinder 1 on the upper side in FIG. 1 of the piston 3, a piston side chamber r2 formed in the cylinder 1 on the lower side in FIG. The outer peripheral passage L2 formed between the casing 6 and the case 6 is filled. Since a through hole L3 penetrating the thickness of the cylinder 1 is formed in the upper part of the cylinder 1 in FIG. 1, the magnetorheological fluid passes between the rod side chamber r1 and the outer peripheral passage L2 through the through hole L3. Can move freely.

  Returning, the base rod 7 fixed to the bottom portion 8b of the wheel side bracket 8 with a bolt 80 includes a shaft portion 7a that stands on the shaft center portion of the cylinder 1 on the side opposite to the piston rod, and a lower portion of the shaft portion 7a in FIG. A cylinder support portion 7b that is coaxially connected to the side and supports the cylinder 1, and a case that is formed with a larger diameter than the cylinder support portion 7b and that is coaxially connected to the lower side of the cylinder support portion 7b in FIG. And a support portion 7c. The cylinder support portion 7b and the case support portion 7c are stepped surfaces between a screw portion (not shown) in which the cylinder 1 or the case 6 is screwed to the outer periphery and a screw portion having a larger diameter than the screw portion. Each of which is provided with a pedestal portion (not shown), and the lower end of the cylinder 1 is abutted against the step surface of the cylinder support portion 7b, and the lower end of the case 6 is abutted against the step surface of the case support portion 7c. doing. The free piston 5 is in sliding contact with the outer peripheral surface of the shaft portion 7 a of the base rod 7 and the inner peripheral surface of the cylinder 1.

  The free piston 5 partitions the piston side chamber r2 and the air chamber r3 formed in the cylinder 1 as described above. The gas chamber r3 is filled with gas while being compressed, and pressurizes the magnetorheological fluid. When the piston rod 2 retreats from the cylinder 1, the free piston 5 moves upward in FIG. 1 and the air chamber r3 expands. When the piston rod 2 enters the cylinder 1, the free piston 5 moves downward in the figure. Therefore, the air chamber r3 contracts, and therefore the change in the cylinder volume corresponding to the volume of the piston rod entering and exiting the cylinder 1 can be compensated by the air chamber r3.

  Further, the base rod 7 is opened to the piston-side chamber r2, and is a base passage L4 opened to the outer circumferential passage L2 formed between the cylinder 1 and the case 6, and a gas for injecting gas into the air chamber r3. An injection path L <b> 5 is formed, and the air chamber side opening of the gas injection path L <b> 5 is closed with a rubber plug 70. Therefore, a gas injection needle can be inserted into the rubber plug 70 to supply gas to the air chamber r3. When the needle is removed, the rubber plug 70 is elastically deformed and the needle hole can be closed. However, the method for injecting gas into the air chamber r3 is not limited to the above, and can be changed as appropriate. A check valve V is provided in the middle of the base passage L4 to allow the flow of the magnetorheological fluid moving from the piston side chamber r2 to the outer peripheral passage L2, but to block the flow in the opposite direction. In FIG. 1, the check valve V has a spherical valve body, but the configuration of the check valve V can be changed as appropriate, and may have an annular plate-like valve body.

  Next, the operation of the magnetorheological fluid shock absorber D1 according to the present embodiment which is one shock absorber constituting the front fork will be described.

  When the magnetorheological fluid shock absorber D1 is extended so that the piston rod 2 retreats from the cylinder 1, the check valve V is not opened, the piston 3 pressurizes the rod side chamber r1, and the outer peripheral passage L2 is added via the through hole L3. Since the magnetorheological fluid in the rod side chamber r1 passes through the piston passage L1 and moves to the piston side chamber r2, the magnetorheological fluid buffer D1 is caused by resistance when the magnetorheological fluid passes through the piston passage L1. Generates extensional damping force. When the coil 40 is energized, a magnetic field is generated in the piston passage L1, and the viscosity of the magnetorheological fluid can be adjusted by the action of the magnetic field, and the resistance when the magnetorheological fluid passes through the piston passage L1 by the viscosity of the magnetorheological fluid. Therefore, the extension side damping force can be adjusted by the viscosity adjusting means 4. Further, the piston rod volume and the cylinder internal volume that have retreated from the cylinder 1 increase, but the free piston 5 moves upward in FIG. 1 and the air chamber r3 expands. Can compensate.

  On the contrary, when compressing the magnetorheological fluid buffer D1 in which the piston rod 2 enters the cylinder 1, the check valve V is opened, and the magnetorheological fluid in the piston side chamber r2 pressurized by the piston 3 is transferred to the base passage L4, the outer periphery. Since it passes through the passage L2 and the through hole L3 and moves to the rod side chamber r1, the magnetorheological fluid shock absorber D1 generates a compression side damping force due to resistance when the magnetorheological fluid passes through them. In the present embodiment, the valve opening pressure of the check valve V is set low, and no magnetic field acts on the base passage L4, the outer peripheral passage L2, and the through hole L3 through which the magnetic viscous fluid passes. The resistance when passing through these is small, and the compression side damping force generated by the magnetorheological fluid shock absorber D1 is set to be small. Further, the piston rod volume and the cylinder internal volume that have entered the cylinder 1 are reduced, but the free piston 5 is moved downward in FIG. 1 and the air chamber r3 is contracted. It can be compensated with r3.

  That is, in the magnetorheological fluid shock absorber D1 of the present embodiment, which is one of the pair of shock absorbers constituting the front fork, only the piston passage L1 can pass the magnetorheological fluid when it is extended, but at the time of compression. Since the piston passage L1 can be bypassed, even if the resistance when the magnetorheological fluid passes through the piston passage L1 is increased and the extension side damping force is set high, only the compression side damping force can be lowered. In the magnetorheological fluid shock absorber D1, the compression side damping force can be kept low even if the coil 40 is energized to change the resistance when the magnetorheological fluid passes through the piston passage L1.

  Subsequently, the extension side damping force generated by the front fork is determined by the two dampers constituting the front fork (only the magnetorheological fluid damper D1 as one of the dampers is shown, and the other damper is not shown. ) And the compression side damping force generated by the front fork is the combined compression side damping force of both shock absorbers. For this reason, when the extension side damping force generated by the front fork is set high and the compression side damping force is set low, even if the extension side damping force and the compression side damping force generated by the other shock absorber are substantially the same, The expansion side damping force of the shock absorber (magneto-viscous fluid shock absorber D1) is higher than the expansion side damping force of the other shock absorber, and the other shock absorber is higher than the compression side damping force of one shock absorber (magnetic viscous fluid shock absorber D1). By setting the compression side damping force of the first shock absorber high, the other side shock absorber compensates for the expansion side damping force that is insufficient, and the one shock absorber compensates for the compression side damping force that is insufficient for the other shock absorber. The damping force of the fork as a whole can be a desired damping force. Further, the extension side damping force of the front fork can be adjusted by one of the shock absorbers (magneto-viscous fluid buffer D1), and the other side of the compression side damping force of the front fork is a conventional magnetorheological fluid buffer. Since it has the same configuration as D2, it can be adjusted by the viscosity adjusting means.

  Hereinafter, the operational effects of the magnetorheological fluid shock absorber D1 according to the present embodiment will be described in detail.

  The magnetorheological fluid shock absorber D1 according to the present embodiment is used for a front fork that supports the front wheels of a saddle-ride type vehicle, and is one of a pair of shock absorbers constituting the front fork.

  Particularly in straddle-type vehicles, it is required to increase the extension side damping force and reduce the compression side damping force. For this reason, by adopting the configuration of one shock absorber of the present invention, even if the expansion side damping force and the compression side damping force of the other shock absorber are substantially the same, the damping force of the entire front fork is reduced to the desired value. A damping force can be easily obtained. Further, according to the above configuration, the valve provided in the base passage L4 of the magnetorheological fluid buffer D1 that is one of the bufferers is the check valve V, and the resistance by the check valve V is small and the magnetorheological fluid buffer is small. Even if the compression side damping force of D1 is insufficient, the compression side damping force can be supplemented by the other shock absorber, so that the setting of the valve provided in the base passage L4 is easy. However, the magnetorheological fluid shock absorber D1 according to the present invention may be both a pair of shock absorbers constituting the front fork, and the magnetorheological fluid shock absorber D1 supports the rear wheel of the saddle type vehicle. It may be used for a cushion, a vehicle other than a straddle-type vehicle, a device, a structure, or the like, or may be used alone. Further, the valve (in the present embodiment, the check valve V) provided in the base passage L4 is increased so as to be a pressure-side damping valve, and the magnetorheological fluid buffer D1 is desired due to the resistance of the pressure-side damping valve. The compression side damping force may be generated.

  In the present embodiment, the magnetorheological fluid shock absorber D1 includes a shock absorber body T including an outer tube t1 and an inner tube t2 that enters and exits the outer tube t1, and the case 6 is provided in the shock absorber body T. The piston rod 2 is accommodated.

  According to the above configuration, the cylinder 1 accommodated in the case 6 and the piston 3, the free piston 5 and the base rod 7 disposed in the cylinder 1 are also accommodated in the shock absorber body T. An outer shell of the magnetorheological fluid shock absorber D1 is formed. For this reason, it is easy to use the magnetorheological fluid shock absorber D1 for the front fork. Furthermore, by accommodating lubricating oil between the shock absorber body T and the case 6, the sliding surfaces of the bushes B1 and B2 that pivotally support the inner tube t2 can be lubricated with the oil. However, the magnetorheological fluid shock absorber D1 according to the present invention may not necessarily include the shock absorber body T.

  Further, in the present embodiment, the base rod 7 closes the anti-piston rod side opening on the wheel side of the cylinder 1 and the case 6 and injects gas into the air chamber r3 into the base rod 7. A gas injection path L5 is formed, and the gas chamber side opening of the gas injection path L5 is closed by a rubber plug 70.

  Therefore, even if a gas injection needle is inserted into the rubber plug 70 and gas is injected into the air chamber r3, the needle hole that can be formed in the rubber plug 70 at this time can be closed by elastic deformation of the rubber plug 70 itself. According to the above configuration, it is possible to reduce the mounting space as compared with the case where the air valve is provided and the gas is injected into the air chamber r3 through the air valve. Further, when the base rod 7 is fixed to the bottom portion 8b of the wheel side bracket 8 with the bolts 80 as in the present embodiment, since the mounting space is limited, the above configuration is effective. It is. However, an air valve may be provided to inject gas into the air chamber r3, and the method of injecting gas into the air chamber r3 can be selected as appropriate.

  In the present embodiment, the magnetorheological fluid shock absorber D1 is formed in the cylinder 1 by being held by the cylindrical cylinder 1, the piston rod 2 that enters and exits the cylinder 1, and the tip of the piston rod 2. Formed in the piston 3, a piston 3 that partitions the rod-side chamber r 1 and the piston-side chamber r 2, a magneto-viscous fluid that is filled in the rod-side chamber r 1 and the piston-side chamber r 2 and changes its viscosity by the action of a magnetic field, and A piston passage L1 communicating with the rod side chamber r1 and the piston side chamber r2, a viscosity adjusting means 4 for adjusting the viscosity of the magnetorheological fluid passing through the piston passage L1, and a piston rod volume integral in and out of the cylinder 1 A free piston 5 that divides the air chamber r3 that compensates for a change in the volume of the cylinder in the cylinder 1, Adjusting means 4 is provided with a coil 40 for generating a magnetic field to said piston passage L1 when energized.

  Further, the magnetorheological fluid shock absorber D1 stands on the cylindrical case 6 which is disposed on the outer periphery of the cylinder 1 and forms an outer peripheral passage L2 between the cylinder 1 and the anti-piston rod side of the cylinder 1. A base rod 7, a through hole L3 that is formed in the cylinder 6 and communicates the rod side chamber r1 and the outer peripheral passage L2, and a piston rod chamber r2 that is formed in the base rod 7 and communicates the outer peripheral passage L2. And a check valve (valve) V that allows only the flow of the magnetorheological fluid passing through the base passage L4 from the piston-side chamber r2 to the outer peripheral passage L2. 5 is formed in an annular shape, is in sliding contact with the inner peripheral surface of the cylinder 1 and the outer peripheral surface of the base rod 7, and divides the piston-side chamber r2 and the air chamber r3.

  According to the above configuration, since the check valve V opens when the magnetorheological fluid shock absorber D1 is compressed, the magnetorheological fluid in the piston side chamber r2 pressurized by the piston 3 bypasses the piston passage L1 where the magnetic field acts. It can move to the rod side chamber r1. For this reason, even if the amount of current flowing through the coil 40 is the same, it is possible to increase the extension side damping force of the magnetorheological fluid buffer D1 and to reduce the compression side damping force. Furthermore, even if a constant current flows through the coil 40 during a failure such as a failure, the extension damping force of the magnetorheological fluid shock absorber D1 can be increased and the compression damping force can be decreased, so that the ride comfort of the vehicle is greatly impaired. Absent.

  Further, according to the above configuration, even if the base passage L4 is provided so that the magnetorheological fluid can bypass the piston passage L1 when the magnetorheological fluid buffer D1 is compressed, the air chamber r3 that compensates for the cylinder volume is provided. It becomes possible to partition into the cylinder 1 easily.

  Further, according to the above configuration, the base rod 7 is erected on the side opposite to the piston rod of the cylinder 1 and the base passage L4 is formed in the base rod 7, so that the check valve V is provided in the base passage L4. Easy.

  Although preferred embodiments of the present invention have been described in detail above, it should be understood that modifications, variations and changes may be made without departing from the scope of the claims.

D1 Magnetorheological fluid buffer L1 Piston passage L2 Outer peripheral passage L3 Through hole L4 Base passage L5 Gas injection passage r1 Rod side chamber r2 Piston side chamber r3 Air chamber T Buffer body t1 Outer tube t2 Inner tube t Check valve (valve)
1 Cylinder 2 Piston rod 3 Piston 4 Viscosity adjusting means 5 Free piston 6 Case 7 Base rod 40 Coil 70 Rubber stopper

Claims (4)

A cylindrical cylinder, a piston rod that enters and exits the cylinder, a piston that is held at the tip of the piston rod and that defines a rod-side chamber and a piston-side chamber formed in the cylinder, the rod-side chamber, and the piston-side chamber And the viscosity of the magnetorheological fluid passing through the piston passage, the piston passage being formed in the piston and communicating with the rod side chamber and the piston side chamber, and the viscosity of the magnetorheological fluid passing through the piston passage. Viscosity adjusting means for adjusting the pressure, and a free piston that divides an air chamber that compensates for a change in the volume of the piston rod in and out of the cylinder into the cylinder.
In the magnetorheological fluid shock absorber provided with a coil that generates a magnetic field in the piston passage when energized,
A cylindrical case that is disposed on the outer periphery of the cylinder and forms an outer peripheral passage with the cylinder, a base rod that stands on the anti-piston rod side of the cylinder, and the rod-side chamber and the outer periphery that are formed on the cylinder A through hole communicating with the passage, a base passage formed in the base rod and communicating the piston side chamber and the outer peripheral passage, and the magnetoviscous fluid passing through the base passage from the piston side chamber to the outer peripheral passage. And a valve that allows only the flow of
The free piston is formed in an annular shape, is in sliding contact with the inner peripheral surface of the cylinder and the outer peripheral surface of the base rod, and partitions the piston side chamber and the air chamber. .   2. The magnetic viscosity according to claim 1, further comprising a shock absorber body including an outer tube and an inner tube that enters and exits the outer tube, wherein the case and the piston rod are accommodated in the shock absorber body. Fluid shock absorber.   The base rod closes the opening on the side opposite to the piston rod of the cylinder and the case, and the base rod is formed with a gas injection path for injecting gas into the air chamber. 3. The magnetorheological fluid shock absorber according to claim 1, wherein the air chamber side opening is closed with a rubber plug.   4. A front fork including a pair of shock absorbers for supporting front wheels of a saddle-ride type vehicle, wherein one of the shock absorbers is the magneto-rheological fluid shock absorber according to claim 1. A front fork characterized by that.

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