JP2008223814A - Variable damping force damper - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a variable damping force damper that realizes facilitation of manufacture and reduction of manufacturing cost while using a magnetic fluid or a magnetorheological fluid as a working fluid.
A damper 6 includes a cylindrical cylinder 12, a piston rod 13, a piston 16 attached to the tip of the piston rod 13, and a guide disk 17 interposed between the piston rod 13 and the piston 16. And. The piston 16 includes a piston main body 31 having a substantially cylindrical shape and four MLV coils 32 fixed to the outer periphery of the piston main body 31. The piston main body 31 is a laminated product of silicon steel plates or a molded product of a composite soft magnetic material, and rectangular magnetic pole portions 31a project from the outer periphery at equal angular intervals. The outer diameter of the piston 16 is set smaller than the inner diameter of the cylinder 12 by a predetermined amount so that the outer peripheral surface of the piston 16 faces the inner peripheral surface of the cylinder 12 with a predetermined gap.
[Selection] Figure 3

Description

  The present invention relates to a magnetic fluid type or magnetorheological fluid type damping force variable damper that constitutes a suspension for an automobile, and more particularly to a technology that realizes facilitation of manufacturing, reduction of manufacturing cost, and the like.

  Suspension is an important factor that affects the driving stability and ride comfort of an automobile. Links (arms and rods) that support the wheels to move up and down with respect to the vehicle body and the impact from the road surface due to the bending of the links. The main components are a spring that absorbs vibrations and the like, and a damper that attenuates vertical vibrations of the vehicle body. The suspension damper includes a cylindrical cylinder tube filled with hydraulic oil and a piston rod mounted at the tip of a piston that slides within the cylinder tube. As the piston (piston rod) moves, A cylindrical shape that employs a structure for moving hydraulic oil between a plurality of oil chambers is widely adopted.

2. Description of the Related Art In recent years, various damping force variable dampers that variably control the damping force according to the motion state of an automobile have been developed as an improvement in the characteristics of a cylindrical damper. As the damping force variable damper, a mechanical type that controls the damping force by providing a rotary valve on the piston that changes the orifice area and rotating this rotary valve with an actuator has been the mainstream, but the structure has been simplified. In order to improve the response and responsiveness etc., there is a type that uses a magnetorheological fluid as the hydraulic oil and controls the damping force by changing the viscosity of the magnetorheological fluid by the magnetorheological valve provided on the piston. (See Patent Document 1).
US Pat. No. 6,260,675

  In the damping force variable damper of Patent Document 1, the following problem has occurred due to the piston moving in the axial direction while sliding on the cylinder. In other words, magnetic fluid and magnetorheological fluid are those in which ferromagnetic fine particles such as magnetite and ferrite are dispersed in the base oil, so that the ferromagnetic fine particles that have entered the sliding surface between the cylinder and the piston during the operation of the damper are crushed. In other words, the sliding surfaces of the cylinder and the piston gradually wear due to the presence of ferromagnetic fine particles, resulting in a decrease in damping performance and durability. Therefore, when manufacturing this type of damping force variable damper, it is necessary to manage the dimensions and surface roughness of pistons and cylinders at a very high level, which makes it difficult to manufacture and avoids an increase in manufacturing cost. There wasn't.

  The present invention has been made in view of such a background, and provides a damping force variable damper that achieves easy manufacturing, reduced manufacturing cost, etc. while using a magnetic fluid or a magnetorheological fluid as a working fluid. Objective.

  The invention according to claim 1 is a cylinder filled with a magnetic fluid or a magnetorheological fluid and connected to one of the vehicle body side member and the wheel side member, and the cylinder is connected to one side liquid chamber and the other side liquid chamber. A piston divided into a piston, a piston rod connecting one of the vehicle body side member and the wheel side member to the piston, and the magnetic fluid or magnetorheological fluid between the one side liquid chamber and the other side liquid chamber And applying a magnetic field generated by the magnetic field forming means to the magnetic fluid or the magnetorheological fluid passing through the hydraulic fluid flow path. The damping force variable damper for controlling the damping force is characterized in that the outer peripheral surface of the piston faces the inner peripheral surface of the cylinder with a predetermined gap.

  According to a second aspect of the present invention, in the damping force variable damper according to the first aspect, the cylinder is formed of a nonmagnetic material or a low magnetic permeability material.

  According to a third aspect of the present invention, in the damping force variable damper according to the first aspect, the repulsive magnetic field forming means for forming a repelling magnetic field that repels the magnetic field generated by the magnetic field forming means is provided outside the cylinder. Features.

  According to a fourth aspect of the present invention, in the damping force variable damper according to any one of the first to third aspects, the magnetic field forming means forms a magnetic field substantially orthogonal to the axial direction of the piston. It is characterized by.

  Further, the invention of claim 5 is the damping force variable damper according to any one of claims 1 to 4, further comprising guide means for restricting radial relative movement between the piston and the cylinder. It is characterized by.

  According to the damping force variable damper of the first aspect, the ferromagnetic fine particles are not crushed and the cylinder and the piston are not worn due to the sliding contact between the piston and the cylinder, and a decrease in the damping performance and durability due to these is suppressed. The According to the damping force variable damper of claim 2, even if the exciting current is supplied to the magnetic field forming means, the piston is not magnetically attracted to the wall surface of the cylinder, and the gap between the piston and the cylinder is easily maintained. According to the damping force variable damper of claim 3, for example, the permanent magnet and the electromagnet constituting the repulsive magnetic field forming means are installed at equal angular intervals on the outer peripheral side of the cylinder, so that the piston is positioned at the center position in the radial direction of the cylinder. It becomes easy to be held. According to the damping force variable damper of claim 4, the magnetic field formed by the magnetic field forming means effectively acts on the magnetic fluid or the magnetorheological fluid, and it becomes difficult to generate power loss and at the same time, it becomes easy to obtain a high damping force. . According to the variable damping force damper of the fifth aspect, the gap between the piston and the cylinder is easily maintained even when an external force such as vibration is applied.

  Hereinafter, several embodiments in which the present invention is applied to a rear suspension of a four-wheel vehicle will be described in detail with reference to the drawings.

[First Embodiment]
1 is a perspective view of a rear suspension according to the embodiment, FIG. 2 is a longitudinal sectional view of a damper according to the first embodiment, FIG. 3 is an enlarged view of a portion III in FIG. 2, and FIG. FIG. 5 is a bottom view of the piston according to the first embodiment, and FIG. 5 is a developed perspective view of the piston according to the first embodiment.

<< Configuration of First Embodiment >>
As shown in FIG. 1, the rear suspension 1 of the first embodiment is a so-called H-type torsion beam type suspension, and a torsion beam that connects the left and right trailing arms 2 and 3 and the intermediate part of both trailing arms 2 and 3. 4. It consists of a pair of left and right coil springs 5, which are suspension springs, a pair of left and right dampers 6 and the like, and the left and right rear wheels 7, 8 are suspended. The damper 6 is a variable damping force damper using MRF (Magneto-Rheological Fluid) as a working fluid, and the damping force is variably controlled by an ECU 9 installed in a trunk room or the like.

<Damper>
As shown in FIG. 2, the damper 6 of the first embodiment is a monotube type (de carvone type), and has a cylindrical cylinder 12 filled with MRF, and an axial slide with respect to the cylinder 12. A piston rod 13 that moves, a piston 16 that is attached to the tip of the piston rod 13 and divides the inside of the cylinder 12 into an upper liquid chamber (one side liquid chamber) 14 and a lower liquid chamber (other side liquid chamber) 15; Dust adheres to the guide disk (guide means) 17 interposed between the rod 13 and the piston 16, the free piston 19 that defines the high-pressure gas chamber 18 in the lower part of the cylinder 12, and the piston rod 13 and the like. The cover 20 for preventing and the bump stop 21 for buffering at the time of full bound are the main components.

<Cylinder>
The cylinder 12 of the first embodiment is made of non-magnetic austenitic stainless steel, and is connected to the upper surface of the trailing arm 2 that is a wheel side member via a bolt 22 that is inserted into the lower eyepiece 12a. Has been. In addition, the piston rod 13 mentioned above is connected to the damper base (wheel house upper part) 25 which is the vehicle body side member via the upper and lower bushes 23 and the nut 24.

<Piston>
The piston 16 is integrated with an MLV (Magnetizable Liquid Valve), and is fixed to the outer periphery of the piston main body 31 having a substantially cylindrical shape as shown in FIGS. 3 to 5. It consists of four MLV coils 32. The piston body 31 is a laminated product of silicon steel plates or a molded product of a composite soft magnetic material, and rectangular magnetic pole portions 31a are provided on the outer periphery thereof at regular angular intervals (90 ° intervals), and at the bottom of the piston rod 13 A screw hole 31b into which a screw portion of the screw shaft 13b is screwed is formed in the shaft center. The MLV coil 32 is formed by winding a conducting wire in a rectangular frame shape and resin molding, and is bonded / integrated to the magnetic pole portion 31a of the piston body 31. The outer diameter of the piston 16 is set to be smaller than the inner diameter of the cylinder 12 by a predetermined amount so that the outer peripheral surface of the piston 16 faces the inner peripheral surface of the cylinder 12 with a predetermined gap (for example, about 1 mm to 2 mm). As shown in FIG. 4, in this embodiment, four hydraulic fluid channels 35 are defined at equal angular intervals (90 ° intervals) by the adjacent MLV coils 32 and the inner wall surface of the cylinder 12.

<Guide disc>
The guide disk 17 is formed by molding a resin having a low friction coefficient (tetrafluoroethylene resin or the like). The guide disk 17 has a disk shape in which boss portions 17a project from both end faces, and the screw shaft 13a of the piston rod 13 is formed. It has a shaft hole 17b to be inserted and four arc holes 17c through which the MRF passes. The outer diameter of the guide disk 17 is set slightly smaller than the inner diameter of the cylinder 12 so as not to bite the ferromagnetic fine particles in the MRF.

<< Operation of First Embodiment >>
When the vehicle starts traveling, the ECU 9 rotates the vehicle body acceleration obtained from the longitudinal G sensor, the lateral G sensor, and the vertical G sensor, the vehicle body speed inputted from the vehicle speed sensor, and the rotation of each wheel obtained from the wheel speed sensor. After setting the target damping force of the damper 6 for each wheel based on the speed or the like, an exciting current is supplied to the MLV coil 32. Then, as shown in FIGS. 6 and 7, a horizontal magnetic field is formed around the MLV coil 32, and the viscosity of the MRF flowing through the gap between the hydraulic fluid passage 35 and the piston 16 and the cylinder 12 changes. The damping force of the damper 6 increases or decreases.

  When an exciting current flows through the MLV coil 32, the piston main body 31 (the magnetic pole portion 31a) becomes magnetic, but in the first embodiment, the cylinder 12 is made of austenitic stainless steel, so the piston 16 is attracted to the cylinder 12 by magnetic force. There is nothing to do. Further, even if vibration or the like occurs in the piston 16 during the operation of the damper 6, the guide disk 17 is brought into sliding contact with the inner peripheral surface of the cylinder 12, so that contact between the outer peripheral surface of the piston 16 and the inner peripheral surface of the cylinder 12 occurs. Is prevented. As a result, the collapse of the ferromagnetic fine particles and the wear of the sliding surfaces of the cylinder and piston, which are problems in the conventional apparatus, do not occur, and the reduction in the damping performance and durability of the damper 6 is effectively suppressed. It was.

[Second Embodiment]
8 is a longitudinal sectional view of the damper according to the second embodiment, FIG. 9 is an enlarged view of the IX portion in FIG. 8, and FIG. 10 is a bottom view of the piston according to the second embodiment.

<< Configuration of Second Embodiment >>
As shown in FIGS. 8 to 10, the damper 6 of the second embodiment has an overall configuration substantially the same as that of the first embodiment described above, but the material and configuration of the cylinder 12 are different. . That is, the cylinder 12 of the present embodiment is made of a ferromagnetic ferritic steel pipe, and four magnet plates (permanent magnets: repulsive magnetic field forming means) 41 are bonded to the outer periphery thereof. In the cylinder 12 to which the magnet plate 41 is bonded, a magnetic field (vertical magnetic field) perpendicular to the magnetic field formed by the MLV coil 32 described above is formed.

<< Operation of Second Embodiment >>
In the case of the second embodiment, as shown in FIG. 11, when an excitation current flows through the MLV coil 32 and the piston main body 31 becomes magnetic, the piston main body 31 and the cylinder 12 are perpendicular to each other in the direction of magnetic flux. To repel each other. As a result, even if vibration or the like occurs in the piston 16 when the damper 6 is operated, the piston 16 is easily held on the axis of the cylinder 12. In this embodiment as well, the guide disk 17 is provided in the same manner as in the first embodiment. Therefore, when a large vibration force acts on the piston 16, the guide disk 17 comes into sliding contact with the inner peripheral surface of the cylinder 12, and the piston Contact between the outer peripheral surface 16 and the cylinder 12 is prevented.

[Third Embodiment]
FIG. 12 is an enlarged vertical cross-sectional view of the main part of the damper according to the third embodiment, and FIG. 13 is a cross-sectional view along XIII-XIII in FIG.

<< Configuration of Third Embodiment >>
The damper 6 of the third embodiment has the same overall configuration as that of the first embodiment described above, but the configuration of the piston 16 is different. That is, as shown in FIGS. 12 and 13, the piston 16 of the present embodiment includes a substantially cylindrical yoke 51, three MLV coils 32 a to 32 c wound / integrated with the yoke 51, and the yoke 51. It is comprised from the cylindrical case 52 to accommodate. Moreover, in 3rd Embodiment, the guide means which regulates the radial direction relative movement of piston 16 and cylinder 12 is not provided.

  The yoke 51 of this embodiment is formed by laminating silicon steel plates, and each of the MLV coils 32a to 32c is wound around three pairs of slits 51a to 51c formed along the axial direction thereof. The slits 51 a to 51 c also serve as the hydraulic fluid flow path 35 through which the MRF flows, and the width thereof is narrowed toward the outer peripheral side of the yoke 51. The case 52 is a die-cast molded product made of an aluminum alloy. The outer peripheral surface of the case 52 faces the inner peripheral surface of the cylinder 12 with a predetermined gap, and the screw portion of the lower screw shaft 13b of the piston rod 13 is screwed. And a plurality of through holes 52b through which the MRF flows. Although the case 52 is depicted as an integrated product in FIG. 12, in reality, the case 52 is divided into a case main body and a cover, and is integrated by laser welding, bolt fastening, or the like with the yoke 51 accommodated. Yes.

<< Operation of Third Embodiment >>
In the case of the third embodiment, as shown in FIG. 14, when an excitation current flows through the MLV coils 32a to 32c, a horizontal magnetic field is formed around the MLV coils 32a to 32c. Since the cylinder 12 is made of austenitic stainless steel as in the first embodiment, the piston 16 is not attracted by the magnetic force to the cylinder 12. In the present embodiment, since the widths of the slits 51a to 51c are narrowed toward the outer peripheral side of the yoke 51, the magnetic flux on the outer peripheral side of the yoke 51 and the magnetic flux on the inner peripheral side are made uniform.

[Fourth Embodiment]
FIG. 15 is an enlarged vertical cross-sectional view of a main part of a damper according to the third embodiment, and FIG. 16 is a cross-sectional view along XVI-XVI in FIG.

<< Configuration of Fourth Embodiment >>
The damper 6 of the fourth embodiment has the same overall configuration as that of the third embodiment described above, but the shape of the yoke 51 is different. That is, the yoke 51 of this embodiment is made of a composite soft magnetic material, and as shown in FIGS. 15 and 16, the base ends of the pair of spirally formed slits 51a and 51b (of the yoke 51). An MLV coil 32 is wound around the central portion.

<< Operation of Fourth Embodiment >>
Also in the case of the fourth embodiment, as shown in FIG. 17, when an excitation current flows through the MLV coil 32, a horizontal magnetic field is formed around the MLV coil 32. Since the cylinder 12 is made of austenitic stainless steel as in the first embodiment, the piston 16 is not attracted by the magnetic force to the cylinder 12.

  Although the description of the specific embodiment is finished as described above, the present invention is not limited to the above embodiment and can be widely modified. For example, in each of the above embodiments, the present invention is applied to a magnetorheological fluid variable damping force damper that constitutes a rear suspension of a four-wheel vehicle. Naturally, the present invention can also be applied to a damping force variable damper for a suspension, a damping force variable damper for a two-wheeled vehicle and the like. In the first and second embodiments, the radial relative movement between the piston and the cylinder is regulated by the guide disk mounted on the piston rod. However, the guide means may be provided on the cylinder side. You may make it abolish a guide means by setting it as the structure where the contact of a piston and a cylinder does not arise. In the third and fourth embodiments, the yoke is accommodated in the case. However, the case may not be used, and a guide disk and a repulsive magnetic field forming means may be provided as in the second embodiment. It may be. In addition, the specific shape of the piston, the specific structure of the damper, and the like can be changed as appropriate without departing from the spirit of the present invention.

1 is a perspective view of a rear suspension according to a first embodiment. It is a longitudinal section of the damper concerning a 1st embodiment. It is the III section enlarged view in FIG. It is a bottom view of the piston concerning a 1st embodiment. It is an expansion perspective view of the piston concerning a 1st embodiment. It is a principal part longitudinal cross-sectional view of the damper which shows the effect | action of 1st Embodiment. It is a cross-sectional view of a damper showing the operation of the first embodiment. It is a principal part longitudinal cross-sectional view of the damper which concerns on 2nd Embodiment. It is the IX section enlarged view in FIG. It is a bottom view of the piston which concerns on 2nd Embodiment. It is a cross-sectional view of a damper showing the operation of the second embodiment. It is a principal part expanded longitudinal cross-sectional view of the damper which concerns on 3rd Embodiment. It is XIII-XIII sectional drawing in FIG. It is a cross-sectional view of a damper showing the operation of the third embodiment. It is a principal part expanded longitudinal cross-sectional view of the damper which concerns on 4th Embodiment. It is XVI-XVI sectional drawing in FIG. It is a cross-sectional view of a damper showing the operation of the fourth embodiment.

Explanation of symbols

2 Trailing arm (wheel side member)
6 Damper 12 Cylinder 13 Piston rod 14 Upper liquid chamber (one side liquid chamber)
15 Lower liquid chamber (other side liquid chamber)
16 Piston 22 Damper base (vehicle body side member)
17 Guide disc (guide means)
31 piston body 31a magnetic pole part 31b hole 32 MLV coil (magnetic field forming means)
35 Hydraulic fluid flow path 41 Magnet plate (repulsive magnetic field forming means)
51 York

Claims (5)

A cylinder filled with a magnetic fluid or a magnetorheological fluid and connected to one of the vehicle body side member and the wheel side member, a piston partitioning the cylinder into one side liquid chamber and another side liquid chamber; A piston rod that connects the other of the vehicle body side member and the wheel side member to the piston, and a working fluid flow path for allowing the magnetic fluid or magnetorheological fluid to flow between the one side liquid chamber and the other side liquid chamber And a magnetic field forming means provided on the piston, and the damping force is controlled by applying a magnetic field by the magnetic field forming means to the magnetic fluid or the magnetorheological fluid passing through the hydraulic fluid flow path. A variable force damper,
A damping force variable damper, wherein the outer peripheral surface of the piston faces the inner peripheral surface of the cylinder with a predetermined gap.   The damping force variable damper according to claim 1, wherein the cylinder is made of a non-magnetic material or a low permeability material.   2. The damping force variable damper according to claim 1, wherein a repulsive magnetic field forming means for forming a repulsive magnetic field that repels a magnetic field generated by the magnetic field forming means is installed outside the cylinder.   The damping force variable damper according to any one of claims 1 to 3, wherein the magnetic field forming means forms a magnetic field substantially orthogonal to the axial direction of the piston.   The damping force variable damper according to any one of claims 1 to 4, further comprising guide means for restricting radial relative movement between the piston and the cylinder.

Images