JP2009150411A - Variable damping force damper - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a variable damping force damper capable of expanding a variable damping force range, improving durability, and so forth. <P>SOLUTION: A piston 16 includes a cylindrical piston cover 30 of which the outer circumference surface slides on an inner wall surface of a cylinder 12, a thin wall cylindrical outer yoke 31 retained inside the piston cover 30, a cylindrical inner yoke 32 disposed inside the outer yoke 31, and an upper and lower pair of disk shaped end plates 33, 34 gripping the outer yoke 31 and the inner yoke 32 in an axial direction. The piston cover 30 is formed of austenitic stainless steel (SUS304 or SUS316) which is a non-magnetic material. The outer yoke 31 is formed of Permendur (high magnetic permeability alloy containing roughly 50% of iron and cobalt) which is a soft magnetic material. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a damping force variable damper using a magnetic fluid or a magnetorheological fluid as a working fluid, and more particularly to a technique for realizing an increase in a damping force variable range, an improvement in durability, and the like.

  2. Description of the Related Art In recent years, various types of damping force variable dampers capable of variable damping force control have been developed for cylindrical dampers used in automobile suspensions in order to improve riding comfort and steering stability. As the damping force variable damper, a mechanical type in which a rotary valve that changes the orifice area is provided on the piston and this rotary valve is driven to rotate by an actuator has been the mainstream, but simplification of the configuration and improvement of responsiveness etc. In order to achieve this, there has been a technology that uses a magnetorheological fluid as a working fluid and variably controls the viscosity (ie, damping force) of the magnetorheological fluid by means of a magnetic field generating means (coil) formed integrally with the piston (patent) Reference 1).

In the damping force variable damper of Patent Document 1, the piston is a cylindrical inner yoke having a coil wound around its outer periphery, a pair of end plates disposed at both ends of the inner yoke, and a cylindrical shape that houses the inner yoke and both end plates. The outer yoke is mainly composed of. Both the inner yoke and the outer yoke are made of a magnetic material, and a hydraulic fluid passage is formed between them by being held by the end plate. The end plate is a disc-shaped material made of a non-magnetic material, and includes a plurality of arc-shaped holes communicating with the hydraulic oil flow path, an annular recess that engages with the protrusion at the inner yoke end, and a piston rod fixing And an annular groove with which the ring is engaged. Further, the inner yoke and the end plate are fixed by caulking the outer edges of both ends of the outer yoke. The damping force control device variably controls the flow resistance (that is, damping force) of the magnetorheological fluid by changing the drive current supplied to the coil to increase or decrease the viscosity of the magnetorheological fluid flowing through the hydraulic oil flow path.
US Pat. No. 6,260,675

  Normally, the damping force variable damper uses an outer yoke made of carbon steel for machine structures, but the saturation flux density of the material is not so high, so it was difficult to increase the damping force variable range. . Therefore, the present inventors tried to use a soft magnetic material such as an iron-cobalt alloy (permendur) having a high saturation magnetic flux density as a material of the outer yoke. However, as is well known, permendur is low in hardness and inferior in elongation characteristics and drawing characteristics, and therefore has the following problems when employed in an outer yoke.

  That is, when the outer yoke described in Patent Document 1 or the like is used in a damping force variable damper that constitutes the outer shell of the piston, when the outer peripheral surface of the outer yoke slides relative to the inner peripheral surface of the cylinder during operation of the damper, the outer yoke Wears in a relatively short period of time, resulting in abnormal noise caused by rattling of the piston in the cylinder, a decrease in damping force caused by an increase in the gap between the cylinders, and the like. Further, in the damping force variable damper disclosed in Patent Document 1, the outer yoke, the inner yoke, and the end plate are coupled and integrated by crimping the end portion of the outer yoke. It was also difficult to adopt the method.

  The present invention has been made in view of such a background, and an object thereof is to provide a damping force variable damper that realizes an increase in a damping force variable range, an improvement in durability, and the like.

  According to a first aspect of the present invention, there is provided a cylinder filled with a magnetic fluid or a magnetorheological fluid and connected to one of a vehicle body side member and a wheel side member, and the cylinder into one side liquid chamber and another side liquid chamber. A piston having a hydraulic oil flow path for partitioning and flowing the magnetic fluid or magnetorheological fluid between the one-side liquid chamber and the other-side liquid chamber, and either the vehicle body side member or the wheel side member The damper is a variable damping force type damper having a piston rod connected to the piston on the other side, the damping force being controlled by applying a magnetic field to the magnetic fluid or the magnetorheological fluid passing through the hydraulic fluid passage. The piston is disposed on the inner side of the cylinder with a predetermined gap on the inner circumferential surface of the cylinder, and on the inner side of the outer yoke, and the operation is performed between the outer yoke and the outer yoke. And inner yoke to define a flow path, characterized in that a sliding contact sliding member with the inner peripheral surface of the cylinder.

  According to a second invention, in the damping force variable damper according to the first invention, the outer yoke has a saturation magnetic flux density set larger than a saturation magnetic flux density of the sliding contact member.

  According to a third invention, in the damping force variable damper according to the first or second invention, the sliding contact member is made of a non-magnetic material and covers an outer periphery of the outer yoke.

  According to a fourth invention, in the damping force variable damper according to the first to third inventions, the sliding contact member is fixed directly or indirectly to the outer yoke by being crimped. To do.

  According to a fifth aspect of the present invention, in the damping force variable damper according to the first to fourth aspects of the present invention, end plates made of a non-magnetic material are disposed at both axial ends of the outer yoke and the inner yoke, respectively. It is characterized by that.

  According to a sixth invention, in the damping force variable damper according to the fifth invention, the sliding contact member is crimped to the both end plates.

  According to 1st invention, durability of a damping-force variable damper can be improved by manufacturing a sliding contact member with a raw material with high abrasion resistance, for example. According to the second aspect of the invention, the damping force variable range of the damping force variable damper can be increased by manufacturing the outer yoke with permendur or the like. Further, according to the third aspect, leakage of magnetic flux from the outer yoke to the outside is suppressed, and the generated damping force with respect to the drive current of the damping force variable damper can be increased. Further, according to the fourth invention, it is possible to reduce the number of manufacturing steps of the damping force variable damper. According to the fifth aspect, leakage of magnetic flux from the axial end of the piston to the outside is suppressed, and the generated damping force with respect to the drive current of the damping force variable damper can be increased. Further, according to the sixth aspect of the invention, it becomes possible to easily combine and integrate the constituent members of the piston, and it is possible to reduce the number of manufacturing steps of the damping force variable damper.

  Hereinafter, an embodiment in which the present invention is applied to a rear suspension of a four-wheel vehicle and a partial modification thereof will be described in detail with reference to the drawings.

[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 embodiment, FIG. 3 is an enlarged view of a portion III in FIG. 2, and FIG. It is an exploded perspective view of the piston concerned.

<< Configuration of Embodiment >>
As shown in FIG. 1, the rear suspension 1 of the present embodiment is a so-called H-type torsion beam suspension, and the torsion beam 4 that connects the left and right trailing arms 2 and 3 and the intermediate portion between the trailing arms 2 and 3. The left and right rear wheels 7 and 8 are suspended from a pair of left and right coil springs 5 and a pair of left and right dampers 6 as suspension springs. The damper 6 is a damping force variable 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 present embodiment is a monotube type (de carvone type), and has a cylindrical cylinder 12 filled with MRF, and slides in the axial direction with respect to the cylinder 12. A piston rod 13 that is attached to the tip of the piston rod 13, a piston 16 that 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, and the cylinder 12 The main components are a free piston 18 that defines a high-pressure gas chamber 17 in the lower portion of the cylinder, a cover 19 that prevents dust from adhering to the piston rod 13 and the like, and a bump stop 20 that performs buffering during full bouncing.

  The cylinder 12 is connected to the upper surface of the trailing arm 2 that is a wheel side member via a bolt 21 that is fitted into the eyepiece 12a at the lower end. The piston rod 13 is connected to a damper base (wheel house upper part) 24 which is a vehicle body side member through an upper and lower pair of bushes 22 and a nut 23.

<Piston>
The piston 16 is integrated with an MLV (Magnetizable Liquid Valve), and a cylindrical piston cover (sliding surface) whose outer peripheral surface is in sliding contact with the inner wall surface of the cylinder 12 as shown in FIGS. Contact member) 30, a thin cylindrical outer yoke 31 held inside the piston cover 30, a columnar inner yoke 32 disposed inside the outer yoke 31, and an upper and lower side sandwiching the outer yoke 31 and the inner yoke 32 in the axial direction. A pair of disc-shaped end plates 33, 34, an MLV coil (magnetic field applying means) 35 resin-molded at the axially central portion of the inner yoke 32, and a locking ring 36 for fixing the piston 16 to the piston rod 13 Is the main component.

  The outer yoke 31, the inner yoke 32, and the end plates 33 and 34 are combined and integrated by crimping both ends of the piston cover 30. The outer yoke 31 has annular step portions 31a and 31b at both ends into which outer edge flanges 33a and 34a formed on the end plates 33 and 34 are fitted. The locking ring 36 is formed by forming a wire rod made of spring steel into a C-shape, and is fitted around the ring holding groove 13b formed in the piston rod 13, and the inner yoke 32, the end plate 33, and the like. Are engaged / held with a predetermined spring force. In FIG. 3, a member denoted by reference numeral 37 is a plug fitted into the axial center of the inner yoke 32, and a member denoted by reference numeral 38 is an O-ring for hydraulic pressure sealing.

  The piston cover 30 of the present embodiment is made of austenitic stainless steel (SUS304 or SUS316), which is a non-magnetic material. In addition, the outer yoke 31 is made of permendur (a high permeability alloy containing approximately 50% of iron and cobalt) which is a soft magnetic material. The outer yoke 31 has an outer peripheral surface disposed on the inner peripheral surface of the cylinder 12 with a predetermined gap (a gap substantially equal to the thickness of the piston cover 30).

  The inner yoke 32 is an integrally molded product made of carbon steel for mechanical structure (S25C or the like), which is a magnetic material, and is fitted with disk-shaped convex portions 33b and 34b protruding from the end surfaces of the end plates 33 and 34. Annular flanges 32a and 32b are provided at both ends. The inner peripheral surface of the outer yoke 31 and the outer peripheral surface of the inner yoke 32 are opposed to each other with a predetermined gap, whereby a hydraulic oil flow path 39 is defined between the outer yoke 31 and the inner yoke 32.

  Both end plates 33 and 34 are made of a non-magnetic aluminum alloy (duralumin), and have four arc-shaped holes 33 c that allow the upper liquid chamber 14 and the lower liquid chamber 15 to communicate with each other via the hydraulic oil flow path 39. , 34c. The end plate 33 has a rod hole 33d in which the piston rod 13 is fitted.

<< Operation of Embodiment >>
When the automobile 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. Based on the speed and the like, a target damping force of the damper 6 is set for each wheel, and a drive current (excitation current) is supplied to the MLV coil 35. As a result, a magnetic field is formed in the piston 16, and the viscosity of the MRF flowing through the hydraulic oil passage 39 is changed to increase or decrease the damping force of the damper 6.

  At this time, in this embodiment, since the outer yoke 31 is made of permendur having a high magnetic permeability, a strong magnetic field due to a high magnetic flux density is formed in the piston 16 even though the thickness is relatively thin. For this reason, the piston cover 30 made of a non-magnetic material suppresses leakage of magnetic flux, so that it is possible to realize an increase in the damping force variable range (that is, high damping force characteristics).

  FIG. 5 is a graph showing the relationship between the damping force and the stroke speed when a drive current is applied to the MLV coil 35. If the dimensions of each part of the piston 16 are set to be the same between the embodiment and the conventional device (the material of the outer yoke 31 is S25C), if the drive current is not applied to the MLV coil 35 (0A), the attenuation will occur. The force values are the same. However, as can be seen from the figure, when the maximum drive current (5 A in this embodiment) is applied to the MLV coil 35, the damping force (shown by a solid line in the figure) of the embodiment is the damping force of the conventional device. Significantly larger than (indicated by a broken line in the figure).

  On the other hand, since the piston cover 30 of the present embodiment is made of stainless steel having excellent wear resistance, the wear of the damper cover 6 is very small even when used over a long period of time (automotive operation). High durability can be realized. In addition, since austenitic stainless steel is excellent in extensibility and drawability, the caulking work at the time of manufacture becomes easy and productivity is also improved.

<Some variations>
FIG. 6 is an enlarged vertical cross-sectional view of a main part of a damper according to a partial modification of the above embodiment.
In some modified examples, the overall configuration is the same as that of the embodiment, but the structure of the piston 16 is different. That is, the piston 16 of the partial modification does not include the piston cover 30, and the outer yoke 31, the inner yoke 32, and the end plates 33, 34 are a plurality of pieces that penetrate the inner yoke 32 and the end plates 33, 34 in the axial direction. The bolt 40 is fastened and integrated. The outer yoke 31 is made of permendur like the embodiment, and the outer peripheral surface of the outer yoke 31 faces the inner peripheral surface of the cylinder 12 with a predetermined gap. In the case of this embodiment, both the end plates 33 and 34 also serve as a sliding contact member, and the outer peripheral surface thereof is in sliding contact with the inner peripheral surface of the cylinder 12. Both end plates 33 and 34 may be plated on the surface in order to suppress wear due to relative sliding with the cylinder 12. Some modified examples have substantially the same functions and effects as those of the embodiment.

  In the above embodiment and some modified examples, by adopting such a configuration, it is possible to achieve high durability while adopting a permendur having a high saturation magnetic flux density as a material of the outer yoke 31.

  This is the end of the description of the specific embodiments and some modified examples, but the present invention can be widely modified without being limited to these embodiments. For example, in the above embodiment, the present invention is applied to a damping force variable damper that constitutes a rear suspension of a four-wheeled vehicle. However, the present invention can also be applied to a damping force variable damper for a front suspension. It can also be applied to a damping force variable damper for a two-wheeled vehicle or the like. Moreover, in the said embodiment, although the austenitic stainless steel which is a nonmagnetic body was used as a raw material of a piston cover, you may employ | adopt carbon steel for machine structures etc. which are magnetic bodies. In addition, the specific shape of the outer yoke, the inner yoke, the end plate, etc., the specific structure of the damper, and the like can be changed as appropriate without departing from the spirit of the present invention.

It is a perspective view of the rear suspension concerning an embodiment. It is a longitudinal cross-sectional view of the damper which concerns on embodiment. It is the III section enlarged view in FIG. It is a disassembled perspective view of the piston which concerns on embodiment. It is a graph which shows the relationship between the damping force which concerns on embodiment, and stroke speed. It is a principal part expanded longitudinal cross-sectional view of the damper which concerns on the partial modification of 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)
30 Piston cover (sliding contact member)
31 Outer yoke 32 Inner yoke 33 End plate (sliding contact member)
34 End plate (sliding contact member)
35 MLV coil 39 Hydraulic oil flow path

Claims (6)

A cylinder filled with a magnetic fluid or a magnetorheological fluid and connected to one of a vehicle body side member and a wheel side member; and the cylinder is divided into a one side liquid chamber and another side liquid chamber and the magnetic fluid Alternatively, a piston formed with a hydraulic fluid passage for allowing the magnetorheological fluid to flow between the one-side liquid chamber and the other-side liquid chamber and the other of the vehicle body side member and the wheel side member are connected to the piston. A damping force variable damper in which a damping force is controlled by applying a magnetic field to the magnetic fluid or the magnetorheological fluid passing through the hydraulic fluid passage,
The piston is
An outer yoke disposed inside the cylinder with a predetermined gap on the inner peripheral surface of the cylinder;
An inner yoke that is disposed inside the outer yoke and that defines the hydraulic oil flow path between the outer yoke and the outer yoke;
A damping force variable damper comprising a sliding contact member that is in sliding contact with an inner peripheral surface of the cylinder.   2. The damping force variable damper according to claim 1, wherein the outer yoke has a saturation magnetic flux density set larger than a saturation magnetic flux density of the sliding contact member.   The damping force variable damper according to claim 1, wherein the sliding contact member is made of a nonmagnetic material and covers an outer periphery of the outer yoke.   The damping force variable damper according to any one of claims 1 to 3, wherein the sliding contact member is directly or indirectly fixed to the outer yoke by crimping.   The attenuation according to any one of claims 1 to 4, wherein end plates made of a non-magnetic material are disposed at both axial ends of the outer yoke and the inner yoke, respectively. Variable force damper.   The damping force variable damper according to claim 5, wherein the sliding contact member is crimped to the both end plates.

Images