JP2006077788A - Variable damping force damper - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To minimize functional deterioration of a variable damping force damper due to sedimentation of magnetic substance particles in a magnetic viscous fluid. <P>SOLUTION: Even if the stop state of a vehicle continues for predetermined time or more so that the magnetic particulates in the magnetic viscous fluid settle to the bottom of a cylinder 21 due to gravity, an electric current of a predetermined value or more is supplied to a coil 28 regardless of the operating condition of the traveling vehicle in later traveling the vehicle, whereby much more magnetic particulates particles are accumulated in a fluid passage 22a in a piston 22 by a magnetic field generated by the coil 28 to reduce the substantial sectional area of the fluid passage 22a more than that in the ordinary control of damping force. Thus, with the movement of the piston 22, the flow velocity of the magnetic viscous fluid passing through the fluid passage 22a is increased to stir and whirl up the magnetic particulates deposited at the bottom of a cylinder 21 to be uniformly diffused, thereby minimizing the functional deterioration of the variable damping force damper 14 due to sedimentation of magnetic particulates. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  In the present invention, the inside of a cylinder filled with a magnetorheological fluid containing magnetic particles is partitioned by a piston into a first fluid chamber and a second fluid chamber, and the first fluid chamber is formed by a fluid passage formed so as to penetrate the piston. Further, the present invention relates to a variable damping force damper that controls a damping force by causing a second fluid chamber to communicate with each other and energizing a coil provided in a piston to change the viscosity of a magnetorheological fluid in a fluid passage.

As the viscous fluid of the variable damping force damper for the suspension device, a magnetic viscous fluid (MRF: Magneto-Rheological Fluids) whose viscosity is changed by the action of a magnetic field is adopted. Patent Document 1 below discloses a coil provided with a coil for applying a magnetic field to a magnetorheological fluid in a passage. According to this variable damping force damper, the damping force of the damper can be arbitrarily controlled by changing the viscosity of the magnetorheological fluid in the fluid passage by a magnetic field generated by energizing the coil.
JP-A-60-113711

  By the way, the magnetic viscous fluid is obtained by dispersing magnetic fine particles such as iron powder in a viscous fluid such as oil. If the vehicle is stopped for a long time, the magnetic material in the magnetic viscous fluid There is a tendency that the fine particles settle by gravity and accumulate on the bottom of the cylinder, and the concentration of the magnetic fine particles in the magnetorheological fluid becomes low. When the vehicle is driven in such a state, even if an appropriate current is supplied to the coil until the magnetorheological fluid is sufficiently stirred by the operation of the damper and the magnetic fine particles are uniformly diffused, the damping force of the damper May not increase to the target value, which may impair the ride comfort of the vehicle.

  The present invention has been made in view of the above-described circumstances, and an object thereof is to minimize the functional deterioration of the variable damping force damper due to the sedimentation of magnetic fine particles in the magnetorheological fluid.

  In order to achieve the above object, according to the first aspect of the present invention, the inside of a cylinder filled with a magnetorheological fluid containing magnetic particles is partitioned into a first fluid chamber and a second fluid chamber by a piston, The first fluid chamber and the second fluid chamber are communicated with each other by a fluid passage formed so as to penetrate the piston, and a coil provided in the piston is energized to change the viscosity of the magnetorheological fluid in the fluid passage to be attenuated. In the variable damping force damper that controls the force, when the vehicle is driven after the vehicle has been stopped for a predetermined time or longer, a current greater than a predetermined value is supplied to the coil regardless of the moving state of the running vehicle. A variable damping force damper is proposed.

  According to a second aspect of the invention, in addition to the configuration of the first aspect, the variable current is supplied to the coil when the piston is raised in the cylinder. A damping force damper is proposed.

  According to the configuration of the first aspect, even if the magnetic particles in the magnetorheological fluid settle on the bottom of the cylinder due to gravity because the vehicle has been stopped for a predetermined time or longer, the vehicle is running when the vehicle is subsequently run. Since a current exceeding a predetermined value is supplied to the coil regardless of the vehicle's motion state, more magnetic particles are accumulated in the fluid passage in the piston by the magnetic field generated by the coil, and the normal damping force is controlled. The substantial passage cross-sectional area of the fluid passage can be made narrower. This increases the flow velocity of the magnetorheological fluid that passes through the fluid passage as the piston moves, stirs and rolls up the magnetic particles deposited on the bottom of the cylinder, and uniformly spreads them, making it variable by the sedimentation of the magnetic particles Degradation of the damping force damper can be minimized.

  According to the configuration of the second aspect, the magnetic particles are agitated when the piston moves up in the cylinder, that is, when the magnetorheological fluid that has passed through the fluid passage flows toward the magnetic particles deposited on the bottom of the cylinder. Since the energization of the coil is performed, the influence on the riding comfort of the vehicle can be reduced as compared with the case where the energization is performed both when the piston is raised and lowered in the cylinder.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below based on examples of the present invention shown in the accompanying drawings.

  1 and 2 show an embodiment of the present invention. FIG. 1 is a front view of a vehicle suspension device, and FIG. 2 is an enlarged sectional view of a variable damping force damper.

  As shown in FIG. 1, a suspension device S that suspends a wheel W of a four-wheeled vehicle has a suspension arm 13 that supports a knuckle 12 in a vertically movable manner on a vehicle body 11, and a variable damping that connects the suspension arm 13 and the vehicle body 11. A force damper 14 and a coil spring 15 connecting the suspension arm 13 and the vehicle body 11 are provided. The electronic control unit U that controls the damping force of the damper 14 includes a signal from the sprung acceleration sensor Sb that detects the sprung acceleration, a signal from the damper displacement sensor Sc that detects the displacement (stroke) of the damper 14, and A signal from the lateral acceleration sensor Sd that detects the lateral acceleration of the vehicle and a signal from the longitudinal acceleration sensor Se that detects the longitudinal acceleration of the vehicle are input.

  As shown in FIG. 2, the damper 14 includes a cylinder 21 whose lower end is connected to the suspension arm 13, a piston 22 that is slidably fitted into the cylinder 21, and an upper wall of the cylinder 21 that extends upward from the piston 22. And a free piston 24 that is slidably fitted to the lower part of the cylinder, and is partitioned by the piston 22 inside the cylinder 21. An upper first fluid chamber 25 and a lower second fluid chamber 26 are partitioned, and a gas chamber 27 in which a compressed gas is sealed in a lower portion of the free piston 24 is partitioned.

  A plurality of fluid passages 22a are formed in the piston 22 so that the upper and lower surfaces thereof communicate with each other, and the first and second fluid chambers 25 and 26 communicate with each other through these fluid passages 22a. The magnetorheological fluid sealed in the first and second fluid chambers 25 and 26 and the fluid passages 22a is a dispersion of magnetic fine particles such as iron powder in a viscous fluid such as oil. By aligning the magnetic fine particles along the magnetic field lines, it is difficult for the viscous fluid to flow, and the apparent viscosity increases. A coil 28 is provided inside the piston 22, and energization of the coil 28 is controlled by the electronic control unit U. When the coil 28 is energized, a magnetic flux is generated as indicated by an arrow, and the viscosity of the magnetorheological fluid changes due to the magnetic flux passing through the fluid passages 22a.

  When the damper 14 contracts and the piston 22 moves downward with respect to the cylinder 21, the volume of the first fluid chamber 25 increases and the volume of the second fluid chamber 26 decreases. Passes through the fluid passage 22a of the piston 22 and flows into the first fluid chamber 25. Conversely, when the damper 14 extends and the piston 22 moves upward relative to the cylinder 21, the volume of the second fluid chamber 26 increases. Since the volume of the first fluid chamber 25 decreases, the magnetorheological fluid in the first fluid chamber 25 passes through the fluid passage 22a ... of the piston 22 and flows into the second fluid chamber 26, and at that time, the fluid passage 22a The damper 14 generates a damping force due to the viscous resistance of the magnetorheological fluid passing through.

  At this time, if the coil 28 is energized to generate a magnetic field, the apparent viscosity of the magnetorheological fluid existing in the fluid passage 22a of the piston 22 increases and it becomes difficult to pass through the fluid passage 22a. Damping force increases. The amount of increase in the damping force can be arbitrarily controlled by the magnitude of the current supplied to the coil 28.

  When a shocking compressive load is applied to the damper 14 to reduce the volume of the second fluid chamber 26, the free piston 24 descends while the gas chamber 27 is contracted to absorb the impact. Further, when a shocking tensile load is applied to the damper 14 to increase the volume of the second fluid chamber 26, the impact is absorbed by the free piston 24 rising while the gas chamber 27 is expanded. Further, when the piston 22 descends and the volume of the piston rod 23 accommodated in the cylinder 21 increases, the free piston 24 descends so as to absorb the increase in the volume.

  Thus, the electronic control unit U detects the sprung acceleration detected by the sprung acceleration sensor Sb, the damper displacement detected by the damper displacement sensor Sc, the lateral acceleration detected by the lateral acceleration sensor Sd, and the longitudinal acceleration detected by the longitudinal acceleration sensor Se. Based on the above, the damping force of each of the four dampers 14 of each wheel W is individually controlled, so that the vehicle can be prevented from being shaken when overcoming road irregularities, thereby improving the ride comfort, or when the vehicle is turning The rolling performance of the vehicle can be suppressed to improve the steering performance, and the steering performance can be improved by suppressing the pitching during sudden acceleration or deceleration of the vehicle.

  By the way, when the vehicle is stopped for a long time, the magnetic particles in the magnetorheological fluid of the damper 14 gradually settle down by gravity and accumulate on the bottom of the second liquid chamber 26 at the bottom of the cylinder 21. Tend. As a result, the concentration of the magnetic fine particles in the magnetorheological fluid becomes low, and the damper 14 generates the target damping force even if an appropriate current is supplied to the coil 28 when the vehicle is next driven. May not be possible. Such a state continues until the vehicle travels a predetermined distance and the magnetic viscous fluid is sufficiently stirred by the operation of the damper 14 during that time, and the magnetic fine particles are uniformly diffused.

  In this embodiment, in order to minimize the temporary deterioration of the function of the damper 14 described above and to exhibit the normal function as soon as possible, in the present embodiment, when the vehicle is driven after the vehicle has been stopped for a predetermined time or more. Regardless of the state of motion of the running vehicle, a current of a predetermined value or more is supplied to the coil 28. That is, while the vehicle 28 is running, a current is supplied to the coil 28 of the damper 14 for ride comfort control and steering control, and the current is corrected in an increasing direction so that the minimum value of the current becomes a predetermined value or more. In addition, a current exceeding the predetermined value is continuously supplied for a predetermined time.

  As a result, the magnetic field generated by the coils 28 accumulates more magnetic particles in the fluid passages 22a, and the substantial passage cross-sectional area of the fluid passages 22a becomes narrower. The flow velocity of the magnetorheological fluid passing through the fluid passages 22a can be increased. This effectively stirs and rolls up the magnetic particles deposited on the bottom of the second fluid chamber 26 and uniformly diffuses them into the cylinder 21, thereby minimizing the deterioration of the function of the damper 14 due to the sedimentation of the magnetic fine particles. Can be suppressed. When the magnetic particles are uniformly diffused in the magnetorheological fluid after a predetermined time has elapsed, the current supplied to the coil 28 is returned to a normal current for ride comfort control and steering control.

  In this way, when the vehicle that has been in a stopped state for a long time is run, the current supplied to the coil 28 of the damper 14 is temporarily increased, so that the magnetic particles that have settled are removed from the magnetorheological fluid. The function of the damper 14 can be promptly restored by diffusing it early. Note that the time during which the vehicle has been stopped can be easily calculated by storing a history of turning on the ignition switch and a history of when the vehicle speed has exceeded a predetermined value.

  Although the embodiments of the present invention have been described above, various design changes can be made without departing from the scope of the present invention.

  For example, in the above-described embodiment, when the vehicle that has been stopped for a long time is traveled, the current of the coil 28 is continuously increased for a predetermined time. Only when 22 rises can the current in coil 28 be increased. When the piston 22 moves up, the magnetorheological fluid flows downward from the upper first fluid chamber 25 toward the lower lower second fluid chamber 26, so that it accumulates at the bottom of the lower second fluid chamber 26. As compared with the case where the coil 28 is energized both when the piston 22 is raised and lowered, the influence on the ride comfort control and the steering control of the vehicle is reduced. be able to.

Front view of vehicle suspension system Expanded sectional view of variable damping force damper

Explanation of symbols

21 Cylinder 22 Piston 22a Fluid passage 25 First fluid chamber 26 Second fluid chamber 28 Coil

Claims (2)

A cylinder (21) filled with a magnetorheological fluid containing magnetic particles is partitioned by a piston (22) into a first fluid chamber (25) and a second fluid chamber (26) so as to penetrate the piston (22). The first fluid chamber (25) and the second fluid chamber (26) are communicated with each other through the fluid passage (22a) formed in the fluid passage (22a), and the coil (28) provided in the piston (22) is energized to supply the fluid passage (22a ) In the variable damping force damper that controls the damping force by changing the viscosity of the magnetorheological fluid in the
A variable damping force characterized by supplying a current of a predetermined value or more to the coil (28) irrespective of the motion state of the running vehicle when the vehicle is driven after the vehicle has been stopped for a predetermined time or longer. Damper. 2. The variable damping force damper according to claim 1, wherein the current of the predetermined value or more of the coil is supplied to the coil when the piston rises in the cylinder.

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