JP2006307982A - Variable damping force damper - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a variable damping force damper using magnetic viscous fluid and capable of preventing a sealing member on an outer peripheral face of a piston rod from being worn by contact with the magnetic viscous fluid. <P>SOLUTION: This variable damping force damper is constituted in such a way that a third fluid chamber 31 is partitioned between an inner cylinder 22 for partitioning a first fluid chamber 29 and a second fluid chamber 30 and an outer tube 21 fitted into its outer periphery in the inside, a coil 37 is provided in the inside of a piston 25, and permanent magnets 35, 36 are provided at both ends in the direction of travel of the piston 25. When the piston 25 reciprocates and moves in the inner cylinder 22 to excite the coil 37, magnetic substance particulates of the magnetic viscous fluid in the third fluid chamber 31 are attracted around the coil 37 and move in the third fluid chamber 31 together with the piston 25 to give resistance to travel of the piston 25 and control damping force of the damper 14 arbitrarily. Since magnetic substance particulates are attracted and collected in the vicinity of the permanent magnets 35, 36 always, response property can be increased. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a variable damping force damper capable of arbitrarily controlling a damping force using a magnetorheological fluid whose viscosity is changed by the action of a magnetic field.

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 58-221034 A

  By the way, in the conventional variable damping force damper, the seal member that seals the outer peripheral surface of the piston rod that penetrates the end wall of the cylinder directly contacts the magnetorheological fluid filled in the cylinder. There is a possibility that the seal member may be worn by the body fine particles, and it is necessary to set a large allowance for the seal member in order to prevent the magnetic viscous fluid from leaking from the worn seal member. Therefore, there is a problem that the frictional resistance between the piston rod and the seal member increases, and it becomes difficult to accurately control the magnitude of the damping force generated by the damper due to the frictional force.

  The present invention has been made in view of the above circumstances, and in a variable damping force damper using a magnetorheological fluid, the seal member that seals the outer peripheral surface of the piston rod is prevented from being worn by contact with the magnetorheological fluid. For the purpose.

  In order to achieve the above object, according to the first aspect of the present invention, a cylinder filled with a viscous fluid and a cylinder slidably fitted into the cylinder and the cylinders are slid into the first and second fluid chambers. A partitioning piston, a piston rod connected to the piston and penetrating a seal member provided on the end wall of the cylinder, an orifice penetrating the piston and communicating the first and second fluid chambers, and preventing movement of the piston A variable damping force damper having a damping force control mechanism that controls the magnitude of damping force by changing a resistance force, wherein the damping force control mechanism is a third fluid chamber isolated from the first and second fluid chambers. And a variable damping force damper characterized by comprising: a magnetorheological fluid that fills the third fluid chamber and flows as the piston moves; and a magnetic field generating means that changes the flow characteristics of the magnetorheological fluid. Is done.

  According to the invention described in claim 2, in addition to the configuration of claim 1, the third fluid chamber is partitioned between a cylinder and an outer tube fitted to the outer periphery of the cylinder, and the magnetic field A variable damping force damper is proposed in which the generating means includes a coil provided inside the piston and permanent magnets provided at both ends of the piston in the moving direction.

  According to the invention described in claim 3, in addition to the structure of claim 1, the second fluid located on the opposite side of the piston rod with the piston sandwiched by the free piston slidably fitted into the cylinder. The damping force control mechanism that divides the chamber and the third fluid chamber and is disposed in the middle portion of the third fluid chamber includes the orifice through which the magnetorheological fluid passes and the coil that generates a magnetic field that passes through the orifice. A variable damping force damper characterized by comprising a magnetic field generating means is proposed.

  According to the invention described in claim 4, in addition to the configuration of claim 3, the third fluid chamber is an inner third fluid chamber defined in a cylinder below the free piston, a cylinder, The outer third fluid chamber is defined between the outer tube and the outer tube fitted to the outer periphery of the cylinder, and a gas chamber filled with high-pressure gas is formed on the upper portion of the outer third fluid chamber. A variable damping force damper is proposed.

  According to a fifth aspect of the present invention, in addition to the configuration of the third or fourth aspect, an orifice block including the orifice and the coil is fixed to the inner wall of the cylinder. A force damper is proposed.

  The inner cylinder 22 of the embodiment corresponds to the cylinder of the present invention, and the permanent magnets 35 and 36 and the coils 37 and 44 of the embodiment correspond to the magnetic field generating means of the present invention.

  According to the configuration of claim 1, when the piston slidably fitted in the cylinder filled with the viscous fluid is reciprocated, the volumes of the first and second fluid chambers partitioned on both sides of the piston are increased. In order to reduce the size, the viscous fluid filled in the first and second fluid chambers passes through the orifice provided in the piston to generate a damping force. At this time, the magnetorheological fluid filled in the third fluid chamber isolated from the first and second fluid chambers flows along with the movement of the piston, and the flow characteristics of the magnetorheological fluid are changed by the magnetic field generating means. Thus, the damping force accompanying the movement of the piston can be arbitrarily controlled. In this way, the first and second fluid chambers filled with the magnetorheological fluid in the third fluid chamber and facing the seal member through which the piston rod slidably pass are filled with the viscous fluid instead of the magnetorheological fluid. The seal member is not worn by the magnetic fine particles contained in the magnetorheological fluid. Therefore, the interference between the piston rod and the seal member can be set small, the frictional resistance received by the piston rod from the seal member can be reduced, and the magnitude of the damping force generated by the damper can be accurately controlled.

  According to the configuration of claim 2, the third fluid chamber is defined between the cylinder and the outer tube fitted to the outer periphery thereof, the coil is provided inside the piston, and the permanent magnet is provided at both ends of the piston in the moving direction. Therefore, when the coil is excited when the piston reciprocates in the cylinder, the magnetic particles of the magnetorheological fluid in the third fluid chamber are attracted around the coil and moved together with the piston in the third fluid chamber, so that the piston The damping force of the damper can be arbitrarily controlled by giving resistance to the movement. Further, even when the coil is demagnetized, the magnetic fine particles are attracted and gathered in the vicinity of the permanent magnet. Therefore, when the coil is excited, the magnetic fine particles can be promptly attracted to the coil to improve the response.

  According to the configuration of claim 3, the second fluid chamber and the third fluid chamber are partitioned by the free piston that is slidably fitted into the cylinder, and the damping force control mechanism disposed in the middle portion of the third fluid chamber is provided. Since the orifice and coil through which the magnetorheological fluid passes are provided, when the piston reciprocates in the cylinder, the free piston reciprocates in the cylinder accordingly and the orifice of the damping force control mechanism provided in the third fluid chamber The magnetorheological fluid passes through. Therefore, by exciting the coil to generate a magnetic field, the damping force of the damper can be arbitrarily controlled by changing the resistance of the magnetorheological fluid passing through the orifice.

  According to the configuration of claim 4, the outer third fluid chamber defined between the inner third fluid chamber defined in the cylinder below the free piston and the outer tube fitted to the outer periphery of the cylinder. And the third fluid chamber is formed, and a gas chamber filled with high-pressure gas is formed in the upper portion of the outer third fluid chamber, so that another free piston for partitioning between the magnetorheological fluid and the high-pressure gas in the outer third fluid chamber Can be eliminated and the number of parts can be reduced.

  According to the fifth aspect of the present invention, since the orifice block including the orifice and the coil is fixed to the inner wall of the cylinder, there is no possibility that the orifice block disposed in the third fluid chamber filled with the magnetorheological fluid is worn.

  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 to 4 show a first embodiment of the present invention. FIG. 1 is a front view of a vehicle suspension device, FIG. 2 is an enlarged sectional view of a variable damping force damper, and FIG. FIG. 4 and FIG. 4 are diagrams for explaining the operation corresponding to FIG.

  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 Sa that detects the sprung acceleration, a signal from the damper displacement sensor Sb that detects the displacement (stroke) of the damper 14, and A signal from the steering angle sensor Sc that detects the steering angle of the vehicle and a signal from the lateral acceleration sensor Sd that detects the lateral acceleration of the vehicle are input.

  As shown in FIG. 2, the damper 14 includes an outer tube 21 having a lower end connected to the suspension arm 13, an inner cylinder 22 disposed coaxially within the outer tube 21, and upper ends of the outer tube 21 and the inner cylinder 22. An upper end plate 23 and a lower end plate 24 that respectively close the lower end, a piston 25 that is slidably fitted to the inner cylinder 22, and a seal member 26 that extends upward from the piston 25 and is provided on the upper end plate 23. A piston rod 27 penetrating liquid-tightly and having an upper end connected to the vehicle body 11 and a free piston 28 slidably fitted to the lower portion of the inner cylinder 22 are provided.

  An upper first fluid chamber 29 and a lower second fluid chamber 30 partitioned by a piston 25 are defined inside the inner cylinder 22, and oil is contained in these first and second fluid chambers 29, 30. Such viscous fluid is filled. A cylindrical third fluid chamber 31 surrounded by the outer tube 21 and the inner cylinder 22 is filled with a magnetic viscous fluid in which magnetic fine particles such as iron powder are dispersed in a viscous fluid such as oil. The magnetorheological fluid has the property that when the magnetic field is applied, the magnetic particles are aligned along the magnetic field lines so that the viscous fluid is difficult to flow and the apparent viscosity increases. A gas chamber 32 filled with high-pressure gas is defined at the lower portion of the free piston 28.

  As shown in FIG. 3, the piston 25 has a piston main body 34 fixed to the piston rod 27 with a nut 33, and a cylindrical shape that is fixed to the upper and lower surfaces of the piston main body 34 along the inner peripheral surface of the inner cylinder 22. Permanent magnets 35, 36, an annular coil 37 housed in the piston body 34, a plurality of orifices 38 disposed on the radially inner side of the coil 37 to communicate the first and second fluid chambers 29, 30. With. The electronic control unit U controls the damping force of the damper 14 by controlling energization to the coil 37 as follows.

  If the damper 14 contracts and the piston 25 moves downward relative to the inner cylinder 22 when the coil 37 is not excited (see arrow A), the volume of the first fluid chamber 29 increases and the second fluid chamber 30 Since the volume is reduced, the viscous fluid in the second fluid chamber 30 passes through the orifices 38 of the piston 25 and flows into the first fluid chamber 29 (see arrow a). Conversely, the damper 14 extends and the inner cylinder 22 extends. When the piston 25 moves upward (see arrow B), the volume of the second fluid chamber 30 increases and the volume of the first fluid chamber 29 decreases. The damper 14 passes through the orifices 38 and flows into the second fluid chamber 30 (see arrow b), and the damper 14 generates a damping force due to the resistance of the viscous fluid passing through the orifices 38.

  At this time, since the magnetic force of the permanent magnets 35 and 36 acts on the magnetorheological fluid in the third fluid chamber 31 through the inner cylinder 22, some of the magnetic fine particles contained in the magnetorheological fluid are in the vicinity of the permanent magnets 35 and 36. The density of the magnetic fine particles increases in the vicinity of the permanent magnets 35 and 36. When the piston 25 moves inside the inner cylinder 22, it is dragged by the permanent magnets 35, 36 integrated with the piston 25, and the portion of the magnetic fluid in the third fluid chamber 31 where the density of magnetic fine particles is high also moves. Since the magnetic force of the magnets 35 and 36 is relatively weak, the density of the magnetic fine particles is not so high, and no great resistance is given to the movement of the piston 25.

  When a shocking compressive load is applied to the damper 14 to reduce the volume of the second fluid chamber 30, the free piston 28 descends while the gas chamber 32 is contracted to absorb the impact. When a shocking tensile load is applied to the damper 14 to increase the volume of the second fluid chamber 30, the impact is absorbed by the free piston 28 rising while the gas chamber 32 is expanded. Furthermore, when the piston 25 descends and the volume of the piston rod 27 accommodated in the inner cylinder 22 increases, the free piston 28 descends so as to absorb the increased volume.

  Therefore, the electronic control unit U detects the sprung acceleration detected by the sprung acceleration sensor Sa, the damper displacement detected by the damper displacement sensor Sb, the steering angle detected by the steering angle sensor Sc, and the lateral acceleration detected by the lateral acceleration sensor Sd. Based on the above, by controlling the damping force of each of the four dampers 14 of each wheel W individually, such as skyhook control that increases the ride comfort by suppressing the vehicle swaying when overcoming the road surface unevenness Ride comfort control and steering stability control that suppresses rolling during turning of the vehicle and pitching during sudden acceleration and deceleration of the vehicle are selectively executed according to the driving state of the vehicle.

  In this way, when the coil 37 of the piston 25 is excited by a command from the electronic control unit U to control the damping force of the damper 14, the magnet attracted by the permanent magnets 35 and 36 as shown in FIG. Since the body fine particles are attracted to the coil 37 that generates a stronger magnetic force than the permanent magnets 35 and 36, a portion where the density of the magnetic fine particles is very high is formed in the third fluid chamber 31 facing the coil 37. Thus, the magnetic fine particles gathered in the vicinity of the permanent magnets 35 and 36 when the coil 37 is excited by previously attracting the magnetic fine particles to the permanent magnets 35 and 36 located near the coil 37. Can be quickly attracted to the coil 37 to enhance the responsiveness.

  Thus, following the movement of the piston 25, if a portion having a very high density of magnetic fine particles moves inside the magnetorheological fluid in the third fluid chamber 31, a large resistance is generated and the damping force of the damper 14 is reduced. Enhanced. At this time, the magnitude of the damping force generated by the damper 14 can be arbitrarily controlled by changing the current supplied to the coil 37.

  According to the damper 14 of the present embodiment, the first fluid chamber 29 facing the seal member 26 through which the piston rod 27 passes is filled with not only a viscous fluid but a viscous fluid, so that it is included in the viscous fluid. The seal member 26 is not worn by the magnetic fine particles. Therefore, the interference between the piston rod 27 and the seal member 26 can be set small, the frictional resistance received by the piston rod 27 from the seal member 26 is reduced, and the magnitude of the damping force generated by the damper 14 is accurately controlled. can do.

  5 to 7 show a second embodiment of the present invention. FIG. 5 is a diagram corresponding to FIG. 2, FIG. 6 is an enlarged view of a portion 6 of FIG. 5, and FIG. FIG.

  As shown in FIGS. 5 and 6, the damper 14 of the second embodiment includes an inner third fluid chamber 31 </ b> A below a free piston 28 slidably fitted to the inner cylinder 22, and the inner cylinder 22 and An outer third fluid chamber 31B is provided between the outer tubes 21 (a portion corresponding to the third fluid chamber 31 of the first embodiment), and communicates with each other through a communication hole 22a formed at the lower end of the inner cylinder 22. The inner third fluid chamber 31A and the outer third fluid chamber 31B constitute the third fluid chamber 31 of the second embodiment. The upper end portion of the outer third fluid chamber 31B is a gas chamber 41 filled with a high-pressure gas that allows the free piston 28 to move.

  The piston 25 of the second embodiment has a simple structure, and includes only orifices 38... For communicating the first and second fluid chambers 29 and 30. Instead, an orifice block 42 fixed to the lower portion of the inner third fluid chamber 31A is connected to an orifice 43 that communicates the inner third fluid chamber 31A and the outer third fluid chamber 31B, and the radially inner side of the orifice 43. And a coil 44 disposed on the surface. Energization of the coil 44 is controlled by the electronic control unit U as in the first embodiment.

  Accordingly, when the damper 14 contracts and the piston 25 moves downward relative to the inner cylinder 22, the volume of the first fluid chamber 29 increases and the volume of the second fluid chamber 30 decreases. When the viscous fluid passes through the orifices 38 of the piston 25 and flows into the first fluid chamber 29, and the damper 14 extends and the piston 25 moves upward relative to the inner cylinder 22, the volume of the second fluid chamber 30 is increased. Increases and the volume of the first fluid chamber 29 decreases, so that the viscous fluid in the first fluid chamber 29 passes through the orifices 38 of the piston 25 and flows into the second fluid chamber 30. The damper 14 generates a damping force due to the resistance of the viscous fluid passing through.

  When the piston 25 moves up and down in this manner, the volume of the piston rod 27 located in the first fluid chamber 29 increases and decreases, so that the free piston is increased and decreased while the volume of the gas chamber 41 is increased and decreased to absorb the increase and decrease of the volume. 28 moves up and down, and accordingly, the magnetorheological fluid in the inner third fluid chamber 31A and the outer third fluid chamber 31B passes through the orifices 43 of the orifice block 42 in both directions. When the coil 44 is energized at that time, as shown in FIG. 7, the density of the magnetic fine particles of the magnetorheological fluid in the orifice 43... Existing in the magnetic flux passage increases, so that the magnetorheological fluid passing through the orifice 43. This increases the damping force of the damper 14. At this time, the magnitude of the damping force generated by the damper 14 can be arbitrarily controlled by changing the current supplied to the coil 44.

  Also with the damper 14 of the second embodiment, since the first fluid chamber 29 facing the seal member 26 through which the piston rod 27 passes is not filled with the magnetic viscous fluid, the seal member is made of magnetic fine particles contained in the magnetic viscous fluid. 26 is not worn. Accordingly, it is possible to accurately control the magnitude of the damping force generated by the damper 14 by setting the tightening allowance between the piston rod 27 and the seal member 26 small, reducing the frictional resistance received by the piston rod 27 from the seal member 26. it can.

  Moreover, since the gas chamber 41 is formed in the upper part of the outer third fluid chamber 31B, the light high-pressure gas is located on the upper side and the heavy magnetorheological fluid is located on the lower side. The number of parts is reduced because it is not necessary to arrange a piston. Further, since the orifice block 42 including the orifices 43... And the coil 44 is fixed to the inner wall of the inner cylinder 22, there is no need to dispose a movable member in the third fluid chamber 31 filled with the magnetorheological fluid. There is no possibility that the movable member is worn by the magnetic fine particles contained therein.

  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 embodiment, the damper 14 for the suspension device is illustrated, but the variable damping force damper of the present invention can be applied to any other application.

Front view of vehicle suspension system Expanded sectional view of variable damping force damper Part 3 enlarged view of FIG. Action explanatory diagram corresponding to FIG. The figure corresponding to the said FIG. 2 based on 2nd Example of this invention. 6 is an enlarged view of FIG. Action explanatory diagram corresponding to FIG.

Explanation of symbols

21 Outer tube 22 Inner cylinder (cylinder)
25 piston 26 sealing member 27 piston rod 28 free piston 29 first fluid chamber 30 second fluid chamber 31 third fluid chamber 31A inner third fluid chamber 31B outer third fluid chamber 35 permanent magnet (magnetic field generating means)
36 Permanent magnet (magnetic field generating means)
37 Coil (magnetic field generating means)
38 Orifice 41 Gas chamber 42 Orifice block 43 Orifice 44 Coil (magnetic field generating means)

Claims (5)

A cylinder (22) filled with a viscous fluid;
A piston (25) that slidably fits into the cylinder (22) and divides the cylinder (22) into first and second fluid chambers (29, 30);
A piston rod (27) connected to the piston (25) and penetrating a seal member (26) provided on an end wall of the cylinder (22);
An orifice (38) passing through the piston (25) and communicating the first and second fluid chambers (29, 30);
A damping force control mechanism for controlling the magnitude of the damping force by changing the resistance force for preventing the movement of the piston (25);
In the variable damping force damper with
The damping force control mechanism is
A third fluid chamber (31) isolated from the first and second fluid chambers (29, 30);
A magnetorheological fluid filled in the third fluid chamber (31) and flowing as the piston (25) moves;
Magnetic field generating means (35, 36, 37, 44) for changing the flow characteristics of the magnetorheological fluid;
A variable damping force damper characterized by comprising The third fluid chamber (31) is partitioned between a cylinder (22) and an outer tube (21) fitted to the outer periphery of the cylinder (22);
The magnetic field generating means includes a coil (37) provided inside the piston (25) and permanent magnets (35, 36) provided at both ends in the moving direction of the piston (25). The variable damping force damper according to claim 1.   The second fluid chamber (30) and the third fluid chamber (on the opposite side of the piston rod (27) across the piston (25) by the free piston (28) slidably fitted to the cylinder (22). 31) and the damping force control mechanism arranged in the middle part of the third fluid chamber (31) generates an orifice (43) through which the magnetorheological fluid passes and a magnetic field through this orifice (43). The variable damping force damper according to claim 1, further comprising: the magnetic field generating unit including a coil (44) that performs the above operation.   An inner third fluid chamber (31A) in which the third fluid chamber (31) is defined in a cylinder (22) below the free piston (28), a cylinder (22), and an outer periphery of the cylinder (22) The outer third fluid chamber (31B) partitioned between the outer tube (21) and the outer third fluid chamber (31B), and the upper portion of the outer third fluid chamber (31B) filled with high-pressure gas (41) The variable damping force damper according to claim 3, wherein: The variable damping force damper according to claim 3 or 4, wherein an orifice block (42) including the orifice (43) and the coil (44) is fixed to an inner wall of the cylinder (22).

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