Piston valve assembly of continuous damping control damper

The present invention relates to a piston valve assembly which is used in a continuous damping control damper using magneto-rheological fluid. The piston valve assembly is coupled with an end of the piston rod, and a stopper having a flat upper surface which is surface-contacted with an upper plate is disposed between a core assembly and the upper plate, thereby properly dispersing a force applied to the piston rod.According to the present invention, the reliability and stability in the coupling between the piston rod and the piston valve assembly can be increased, thereby stably controlling the damping force of the damper. Further, the slot is formed in the core of the piston valve assembly so as to reduce the damping force in the lower speed range, thereby considerably improving the driving comport of a vehicle.

BACKGROUND OF THE INVENTION

This application claims the benefit of Korean Patent Application No. 10-2007-0094296, filed on Sep. 17, 2007, in Korea, which is hereby incorporated by reference for all purposes as if fully set forth herein.

FIELD OF THE INVENTION

The present invention relates to a piston valve assembly and more particularly, to a piston valve assembly which is used in a continuous damping control damper using magneto-rheological fluid.

DISCUSSION OF THE RELATED ART

In general, a suspension is provided between a car body and a wheel so as to improve driving comports. The suspension includes a chassis spring for absorbing vibration and shock from a road surface, and a damper for damping free vibration of the chassis spring.

The damper functions to absorb the free vibration of the chassis spring by converting vertical kinetic energy into heat energy, thereby rapidly damping the free vibration of the chassis spring.

Recently, in a high-class motorcar, there is widely used an active controlled suspension system which detects a body status of the car and then feeds back the detecting results so as to electronically control a damping force of the damper.

As one of various methods of electronically controlling the damping force of the damper, there is generally used a method in which a fluid passing hole is formed in a piston valve reciprocating in a cylinder and the movement of fluid through the fluid passing hole is adjusted.

The method of adjusting the movement of fluid through the fluid passing hole is classified into a way of adjusting a sectional area of the fluid passing hole using a spring and a way that fills electro-rheological fluid or magneto-rheological fluid in the cylinder and then adjusts a flowing resistance of the fluid using an electronic or magnetic property of the fluid.

As shown inFIG. 1, a damper10using the magneto-rheological fluid (MR fluid) includes a cylinder20of which one end is opened and which is formed with a hollow portion therein; a piston rod40which is inserted through an upper portion of the cylinder20; a piston valve assembly which is connected with a lower end of the piston rod40so as to reciprocate in the cylinder20.

Further, at a lower side of the piston valve assembly30, there is provided a floating piston15for compensating a volume change due to the movement of the piston rod40. And high pressure nitrogen gas is filled in a space at a lower side of the floating piston50.

A rod guide60is coupled to an upper end of the cylinder20so as to close an entrance of the cylinder20and also to guide the up/down movement of the piston rod40.

An internal portion of the cylinder20is divided into a lower compressive chamber and an upper tensile chamber, on the basis of the piston valve assembly30, and the MR fluid is filled in the compressive chamber and the tensile chamber.

The MR fluid contains metallic particles of about 3˜10 μm and has a property that an apparent viscosity thereof is changed by magnetic field generated around it. Using the property, a damping force (compression force and tensile force) of the damper10can be controlled by applying the magnetic field to the MR fluid which is flowed into the compressive chamber and the tensile chamber through the piston valve assembly30and thus changing the apparent viscosity.

As shown inFIGS. 2 and 3, the piston valve assembly30includes a core assembly31which is fixed to a lower end of the piston rod40and provided with a solenoid coil, an upper plate32which is disposed at an upper side of the core assembly31, a lower plate33which is disposed at a lower side of the core assembly31, and a flux ring34which wraps the core assembly31.

The flux ring34provides a path for the magnetic field generated from the solenoid coil of the core assembly31, and the upper and lower plates32and33function to prevent the magnetic field from exerting an influence on the compressive chamber and the tensile chamber.

The flux ring34also wraps side and upper surfaces of each of the upper and lower plates32and33as well as the core assembly31, so that the upper plate32is closely contacted with an upper surface of the core assembly31and the lower plate33is closely contacted with a lower surface of the core assembly31.

Further, a gap is formed between the fluxing ring34and the core assembly31so that the MR fluid can be passed through the gap, and the upper and lower plates32and33are respectively formed with a fluid passing hole35,36which is communicated with the gap.

Meanwhile, in order to couple a lower end of the piston rod40to the piston valve assembly30, there is formed a coupling groove42along an outer circumference of the piston rod40. A ring-shaped key37having a circular section is coupled to the coupling groove42.

And by placing the key37between the upper plate32and the core assembly31, the upper plate32and the piston rod40are coupled to each other. And the core assembly31and the upper and lower plates32and33are integrally coupled by the flux ring34, thereby coupling the piston valve assembly30and the piston rod40.

A connecting cable70is installed in the piston rod40, and the connecting cable70is extended through the lower end of the piston rod40and then connected to the solenoid coil of the core assembly31.

A lower surface of the upper plate32has to be closely contacted to the core assembly31and the key37upon the coupling process. To this end, on a lower portion of an internal circumference of a penetrated portion of the upper plate32, in which the piston rod40is inserted, there is formed a groove portion38in which a part of the key37is inserted.

However, in the structure, since the tensile force of the piston rod40, which is generated upon a tensile stroke, is concentrated on the key37and the groove portion38of upper plate32, there is problem that the key37and the groove portion38are worn away each other while they are used for a long time, thereby deteriorating the reliability in coupling between them. In the worst case, the key37or the groove portion38of upper plate32is damaged, and thus the piston rod40may be separated from the piston valve assembly30(concretely, from the upper plate32).

Furthermore, if there is formed a clearance between the key37and the groove portion38by the wear and tear, there is another problem that the controlling of the damping force of the damper10becomes unstable.

Meanwhile, the damping force of the damper10is generally controlled by changing the intensity of current applied to the solenoid coil of the piston valve assembly30according to a relative distance between a vehicle body and an axle.

Therefore, if the relative distance between the vehicle body and the axle is always constant, the damping force is also maintained constantly.

However, in order to improve the driving comports of a vehicle, it is necessary to change the damping force of the damper10according to a speed of the vehicle. Particularly, if the damping force of the damper10is so large in a lower speed range, the driving comport is lowered.

Accordingly, there is a necessity for a design component which can control a damping property of the damper10in the lower speed range.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a piston valve assembly of a continuous damping control damper in which the reliability in coupling between the piston rod and the piston valve assembly is increased, thereby stably controlling the damping force of the damper.

It is an object of the present invention to provide a piston valve assembly having a damping property which is capable of improving the driving comports of a vehicle in the lower speed range.

To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, the present invention provides a piston valve assembly which is coupled to an end of a piston rod inserted into a cylinder of a continuous damping control damper, comprising a core assembly which has a solenoid coil therein; a stopper which is fixed to the piston rod at an upper side of the core assembly, and provided with a body which is formed with a through-hole in which the piston rod is inserted, and a supporting portion which is protruded from an upper end of the body to an outside so as to have a larger diameter than the body and also have a flat upper surface; an upper plate which is coupled with the piston rod at an upper side of the stopper and also formed with a stopper receiving portion at a lower surface thereof, which is surface-contacted with the supporting portion of the stopper; a lower plate which is placed at a lower side of the core assembly; and a flux ring which receives the core assembly, the upper plate and the lower plate therein, and of which an upper end supports a peripheral portion of an upper surface of the upper plate, and of which a lower end supports a peripheral portion of a lower surface of the lower plate.

Preferably, a lower end of the body of the stopper is plastic-deformed and then inserted into a coupling groove formed at an outer surface of the piston rod so that the stopper is fixed to the piston rod.

Preferably, the core assembly comprises a core comprising a winding portion, upper and lower protruded portions which are respectively formed at upper and lower ends of the winding portion to have a larger diameter than the winding portion, and a slot which is longitudinally formed at each of the upper and lower protruded portions; and a solenoid coil which is wound on the winding portion of the core.

Preferably, the plurality of slots are formed at each of the upper and lower protruded portions, and each slot of the upper protruded portion and each slot of the lower protruded portion are arranged to be correspondent to each other.

Further, the present invention provides a piston valve assembly which is coupled to an end of a piston rod inserted into a cylinder of a continuous damping control damper, comprising a core assembly which comprises a core having a winding portion, upper and lower protruded portions which are respectively formed at upper and lower ends of the winding portion to have a larger diameter than the winding portion, and a slot which is longitudinally formed at each of the upper and lower protruded portions and a solenoid coil which is wound on the winding portion of the core; an upper plate which is placed at an upper side of the core assembly; a lower plate which is placed at a lower side of the core assembly; and a flux ring which receives the core assembly, the upper plate and the lower plate therein, and of which an upper end supports a peripheral portion of an upper surface of the upper plate, and of which a lower end supports a peripheral portion of a lower surface of the lower plate.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

Reference will now be made in detail to the illustrated embodiment of the present invention, which is illustrated in the accompanying drawings.

As shown inFIGS. 4 and 5, a piston valve assembly100according to the present invention includes a core assembly110which is fixed to a lower end of the piston rod40and provided with a solenoid coil, an upper plate120which is placed at an upper side of the core assembly110, a lower plate130which is placed at a lower side of the core assembly110, and a flux ring140which receives the core assembly110, the upper plate120and the lower plate130therein.

On an upper surface of the core assembly110, there is formed a rod coupling groove114in which the lower end of the piston rod40and a connecting cable70are inserted. The upper and lower plates120and130are respectively formed with a fluid passing hole122,132.

Particularly, the embodiment of the present invention is characterized by using a stopper150in order to more stably couple the piston rod40and the core assembly110.

The stopper150is disposed between the upper plate120and the core assembly110, and a lower end of the stopper150is fixedly inserted into a coupling groove42which is formed along an outer surface of the piston rod40.

As shown inFIG. 6, the stopper150includes a body154which is formed with a through-hole152in which the piston rod40is inserted, and a supporting portion156which is protruded from an upper end of the body154to the outside so as to have a larger diameter than the body154and also have a flat upper surface.

Comparing with the conventional key, since the stopper150has a large contact surface with the upper plate120, it is possible to properly disperse a pressure which is applied to the upper plate120by an up/down movement of the piston rod40, thereby improving the reliability in coupling between the piston rod40and the piston valve assembly100.

FIG. 7is a cross-sectional view showing a coupling status between the upper plate120and the stopper150in the piston valve assembly100according to the embodiment of the present invention.

Herein, a stopper receiving portion124is formed at a lower surface of the upper plate120so as to have a concave shape, and a ceiling portion of the stopper receiving portion124is formed to be flat.

Therefore, when assembling the piston valve assembly100, the supporting portion156of the stopper150is inserted into the stopper receiving portion124of the upper plate120, and the flat upper surface of the supporting portion156is surface-contacted with the flat ceiling portion of the stopper receiving portion124, thereby increasing the strength and reliability in the coupling between them.

The stopper150is fixed to the piston rod40. In the embodiment of the present invention, a lower end158of the body154of the stopper150is plastic-deformed and then fixedly inserted into the coupling groove42of the piston rod40.

Meanwhile, the piston valve assembly100according to the embodiment of the present invention is characterized by using a new type core assembly110in order to improve the driving comports in a lower speed range.

The core assembly110is provided with a core on which a solenoid coil is wound and fabricated as follows:

First of all, as shown inFIG. 8A, the core111is fabricated by mechanically treating a metallic material.

The core111includes a winding portion117on which the solenoid coil is wound, and upper and lower protruded portions112and113which are respectively formed at upper and lower ends of the winding portion117to have a larger diameter than the winding portion117.

In a center portion of the upper protruded portion112, there is formed the rod coupling groove114in which the lower end of the piston rod40and the connecting cable70are inserted.

A plurality of slots116are longitudinally formed at a side surface of each of the upper and lower protruded portions112and113, and each slot116of the upper protruded portion112and each slot116of the lower protruded portion113are arranged to be correspondent to each other. That is, one slot116of the upper protruded portion112and one slot116of the lower protruded portion113are disposed in the same longitudinal line.

Then, as shown inFIG. 8B, a plastic coating layer is formed on a surface of the core111through a first injection process, and each slot116is filled with a plastic material. Further, in the first injection process, an arrangement groove is formed on an outer surface of the winding portion117so that the solenoid coil to be wound can be positioned in place.

Then, as shown inFIG. 8C, the solenoid coil118is wound on the winding portion117, and another plastic coating layer is formed on the outside of the wound solenoid coil118through a second injection process.

Meanwhile, due to the plurality of slots116formed around the core111, the intensity of magnetic field generated by the current applied through the connecting cable70is weakened around the slots116. Therefore, the damping force by the MR fluid passing through the clearance between the core assembly110and the flux ring140is reduced compared with the case that the slots116are not formed.

Particularly, the reduction phenomenon of the damping force is conspicuously generated in the lower speed range. That is, as shown inFIG. 9which shows a comparison between the case that the slots116are formed in the core111and the case that the slots116are not formed in the core111, if the slots116are formed, the intensity and increasing rate of the damping force is remarkably reduced in the lower speed range.

As described above, if the damping force in the lower speed range is lowered, it is possible to improve the driving comports.

Meanwhile, the number of the slots and a width of each slot are not limited specially. However, it is preferable that the slots are symmetrically formed with respect to center of the core111. Also, the shape of each slot116is not limited specially. For example, the slot116may have various shapes such as a triangle, a circular arc, a quadrangle and the like, as shown inFIGS. 10A to 10D.

According to the present invention, the reliability and stability in the coupling between the piston rod and the piston valve assembly can be increased, thereby stably controlling the damping force of the damper.

Further, the slot is formed in the core of the piston valve assembly so as to reduce the damping force in the lower speed range, thereby considerably improving the driving comport of a vehicle.