GB2044882A - Hydraulic shock absorber with vortex valve - Google Patents

Abstract

The piston of a hydraulic shock absorber is provided with a vortex value for controlling flow from one side of the piston to the other, the vortex valve comprising a space 56 inside the piston into which part helical passages 64 lead. There may also be a vortex chamber in the base valve. <IMAGE>

Description

SPECIFICATION A shock absorber 1. Field of the Invention The present invention relates generally to a shock absorber employed for the front and rear vehicle suspension systems and/or engine support of an automotive vehicle. More particularly, the present invention relates to a hydraulic shock absorbing means of a shock absorber, when absorbs a fluid pressure put on a hydraulic fluid and the like which the pressure is generated in response to a shock exerted onto the shock absorber, to thus absorb a shock.

2. Description of the Prior Art As is well known those skilled in the art, a direct-acting, or telescopic shock absorber is one of the most widely used shock absorbers.

Such a shock absorber is used in an automotive vehicle, particularly on the front and rear vehicle suspension system for absorbing road shock exerted on the vehicle and/or on the engine support for preventing the engine from vibration. The shock absorber has a hollow cylindrical tube which is filled with hydraulic fluid. A thrusting piston is movably disposed within the tube and divides the internal space of the tube into two fluid chambers; namely, upper and lower chambers. The piston or the cylindrical tube is provided with a plurality of fluid passages through which the fluid chambers communicate with one another. Through the fluid passages, the hydraulic fluid flows between the chambers in response to changes of fluid pressure in the chambers or differences arising thereby.

When the shock absorber is used in a vehicle suspension system, when a wheel of the vehicle is moved up with respect to the vehicle body, the shock absorber is compressed. Then, the thrusting piston moves down to put pressure on the fluid in the lower chamber and to create a vacuum in the upper chamber. The fluid in the lower chamber is thus forced through the fluid passages formed in the piston and pass into the upper chamber. Meanwhile, when the wheel is moved down, the shock absorber is expanded. At this time, the piston is moved up to put pressure on the fluid in the upper chamber and to create a vacuum in the lower chamber.

Thereby, the fluid in the upper chamber flows out from the upper chamber into the lower chamber through the passages of the piston.

During the above-mentioned motion of the shock absorber, if the fluid flows freely through the fluid passage, the shock absorber will be merely compressed and expanded repeatedly and will not have any effect of absorbing the road shock. This may cause a roght ride of the vehicle. For absorbing the road shock, it is necessary to absorb the fluid pressure while the fluid flows through the fluid passages. In practice, shock absorbing functions have been provided by the controlled flow of fluid through valve means provided in fluid passage. Generally, the valve means resistively limit movement of the fluid when the piston moves and thus when the fluid is forced to pass through the passages.

Since such a shock absorber is usually employed in a vehicle suspension system together with a coil spring wound therearound, the above function of limiting of the fluid flow will restrain the spring motion thus to absorb the road shock. In another method of absorbing the road shock, there are provided various means for making the velocity of fluid flow in one direction to different from that in the other for limiting the speed of transmitting the fluid pressure from one chamber to the other.

This may cause a delay in response of the up and down movement of the system with respect to the shock exerted and shorten somewhat the distance between the lowermost and uppermost positions of the piston.

In a conventional shock absorber, the valve means generally comprise thin leaf-springs arranged to limit the fluid passing through the fluid passages in the piston combined with some valve element to limit the amount of fluid passing therethrough. The conventional means for limiting the fluid passing have relatively complicated construction which leads to high cost. Further, such limiting means have a plurality of movable elements which may be worn out by using for a long period. This results in shortening of the period of use of such a shock absorber; for example, if the leaf-valve closing a fluid passage connecting the upper and lower chambers is worn out, it can no longer limit the fluid flowing therethrough.Furthermore, since conventional shock absorbers have, as mentioned above, a valve means which responds evenly to any shock, such conventional shock absorbers respond even to relatively weak shocks or slight high frequency vertical movement which it may not be necessary to absorb. This may also cause a rough ride. Meanwhile, if used as an engine support, such a conventional shock absorber is apt to transmit vibrations of the engine to the vehicle body by responding excessively to high frequent vibration. As the result, noise will be caused in the vehicle. The present invention is directed to improvements in and relating to the valve means, particularly when provided in the piston, for effectively absorbing shocks.Further, in accordance with the present invention, there is sought a way of simplification of the construction of the valve means so that production cost may be reduced and durability increased.

SUMMARY OF THE INVENTION Therefore it is an object of the present invention to provide a shock absorber having a valve means capable of absorbing shocks exerted thereon and allosing for simplified construction.

Another object of the present invention is to provide a shock absorber having a valve means for absorbing shocks, in which the valve means comprises a vortex valve.

A further object of the present invention is to provide a shock absorber having a valve means which includes a reliefing means which acts as a bypass passage for compressed fluid when an abnormally hard shock is encountered which would otherwise result a rough ride.

Other objects, advantages and improvements will become apparent from the several preferred embodiments of the invention described below.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention will become more fully understood from the detailed description given below, and the accompanying descriptions of the preferred embodiments of the invention, which, however, are not to be taken as limitative of the present invention in anyway, but are for the purpose of illustration and explanation only.

In the drawings: Figure 1 is a longitudinally sectional view of a direct-acting shock absorber including a first embodiment of the valve means in accordance with a first embodiment of the the present invention; Figure 2 is an enlarged fragmentary sectional view of the shock absorber of Fig. 1, showing the valve means of the first embodiment formed in a thrusting piston; Figure 3 is a sectional view of the valve means taken along line Ill-Ill of Fig. 2; Figure 4 is a sectional view being substantially the same as Fig. 3, showing a fluid flow when the shock absorber is compressed; Figure 5 is a sectional view substantially the same as Fig. 3 showing a fluid flow when the shock absorber is expanded;; Figure 6 is a schematic illustration showing the theory of shock absorption in the valve means applied to the shock absorber according to the present invention; Figure 7 is a fragmentary sectional view of a modification of the first embodiment of a valve means in accordance with the present invention; Figure 8 is a sectional view of the valve means of Fig. 7 taken along line VII-VII; Figure 9 is a transverse sectional view of another modification of the first embodiment valve means in accordance with the present invention; Figure 10 is a transverse sectional view of a further modification of the first embodiment of the valve means in accordance with the present invention; Figure 11 is a fragmentary sectional view of the second embodiment of a valve means in accordance with the present invention;; Figure 12 is a longitudinally sectional view of a shock absorber including a third embodiment of the valve means in accordance with the present invention; Figure 13 is an enlarged fragmentary sectional view of a second embodiment of the valve means formed in a thrusting piston according to the present invention; Figure 14 is a sectional view of the valve means formed on an end fitting which is fitted at the lower end of a inner tube, taken along line XIV-XIV of Fig.12; Figure 15 is a transverse sectional view of a modification of the second embodiment of the valve means in accordance with; Figure 16 is a transverse sectional view of a valve means formed on the end fitting as a modification of the embodiment shown in Fig.

14; Figure 17 is a fragmentary sectional view of a fourth embodiment of a valve means in accordance with the present invention; Figure 18 is a sectional view of the valve means of Fig. 1 7 taken along line XIX-XIX; Figure 19 is a graph showing the bumpting force of the valve means according to the present invention; Figure 20 is a fragmentary sectional view of a modification of the fourth embodiment of the valve means; Figure 21 is a fragmentary sectional view partly cut away of the valve means; and Figure 22 is a fragmentary sectional view of a fifth embodiment of the valve means in accordance with the present invention.

DESCRIPTION OF THE PREFERRED EMBODI MENT Referring now to the drawings, particularly to Figs. 1 to 5, there is illustrated the first embodiment of a shock absorber in accordance with the present invention. Fig. 1 shows a direct-acting shock absorber 10 comprising a cylindrical tube 12, a reservoir tube 14 and a piston 16. The piston 16 is slidably disposed in the interior of the cylindrical tube 1 2 and divides the internal space of the cylindrical tube 1 2 into upper and lower chambers 1 5 and 1 7 respectively. The cylindrical tube 1 2 is disposed within the reservoir tube 14 apart from the vertical periphery 1 8 of the tube 14 so as to define therebetween a fluid reservoir chamber 20. At the top of the tube 12, is disposed a rod guide 22 having a central opening 24. The lower end of a piston rod 26 extends through the central opening 24 into the interior of the tube 1 2. The piston rod 26 has formed at the lower end a threaded portion 28 which passes through a central opening 30 formed in the piston 1 6. A locking nut 32 is threaded on the portion 28 to fix the piston 16 to the lower end of the piston rod 26. The upper end of the piston rod 26 extends outside the tube 1 2 through the rod guide 22 and a piston-rod seal 34 which is mounted on the top of the fluid reservoir tube 14, spaced apart from the rod guide 20. A dust shield 36 and a ring 38 for connecting the shock absorber to the vehicle chassis, for example, are provided at the top of the piston rod 26.Between the rod guide 20 and piston-rod seal 34, is disposed a helical expansion spring 40 to urge the seal 34 upword. The rod guide 20, the seal 34 and the spring 40 form a guide-and-seal assembly for fluid proofing purposes.

On the lower end of the tube 12, is secured an end fitting 42 incorporating a valve means.

As will be understood from Fig. 1, the end fitting 42 is provided with a valve means of substantially the same construction as that of the piston described below with respect to construction and function. The valve means of end fitting 42 comprises a generally diskshaped hollow body 44 with fluid passages 46 and 48 for communication between the fluid reservoir chamber 20 and the lower chamber 1 7 of the cylindrical tube 1 2. A ringand-cap assembly 50 is fitted at the lower end of the reservoir tube 14 to close it. The ring of the assembly 50 is used for securing the lower end of the shock absorber to a suspension member of the vehicle, for example.

Although the first embodiment of a valve means according to the present invention is described as applied to this general construction of a direct-acting shock absorber tube, the valve means can be applied to various designs and constructions of hydraulic shock absorber. Therefore, the above description should not be considered as limiting the present invention.

Now we refer to Figs. 2 to 5, where is illustrated in detail the first embodiment of a valve means in accordance with the present invention provided in the piston 1 6 of absorbing shocks. Particularly as shown in Figs. 2 and 3, the piston 1 6 is formed with a central opening 30 through which the threaded portion 28 of the piston rod 26 passes and extends downwardly therefrom. Below the piston 16, the threaded portion 28 is engaged with the locking nut 32. It will be appreciated that the threaded portion 28 is stepped at the portion 29 so that it has a diameter smaller than that of the rod 26 above the portion 29 to define a shoulder. The central opening 30 of the piston has a diameter adapted to receive the threaded portion 28 of the piston rod 26 but being smaller than that of the rod 26 above the portion 29.By engagement of the thread portion 28 and the locking nut 32, the piston 1 6 is held against the shoulder 29 of the piston rod 26 so that it may be secured to the rod 26. The piston is further provided with an annular groove 52 around its periphery. An annular sealing member 54 is received within the groove 52 and projects outwardly therefrom. The outer surface of the sealing member 54 tightly but slidingly contacts the inner surface of the cylindrical tube 1 2 so as to separate the upper and lower chambers 1 5 and 1 7 in a fluid proof manner.

A disk-shaped chamber 56 is defined with the piston 1 6 by the top 58, the circular periphery 60 and the bottom 62 of the piston 1 6. A plurality of first fluid passages 64 are provided in the piston 1 6 for communication between the upper chamber 1 5 and the chamber 56. As shown in Figs. 2 and 3, the passages 64 are formed in a helical fashion, and one end 66 of each passage is opened to the upper chamber 1 5 at the top 58 of the piston and the other end 68 is opened to the chamber 56 at the peripheral portion 60. The passages 64 are formed to discharge a compressed fluid flow the chamber 56 in the direction of a tangent to the circular periphery of the chamber 56.In fact there is a small angle between the tangent to the circular periphery of the chamber 56 and the direction of the passage 64 at the end 68, but thin angle is so small that it can be disregarded.

The passages 64 are spaced apart from one another at regular intervals. A plurality of second fluid passages 70 are formed in the bottom 62 of the piston 1 6 for communication between the chamber 56 and the lower chamber 1 7. The passages 70 are spaced at regular angles and each opens at one end 72 to the chamber 56 and at the other end 74 to the lower chamber 1 7. As will be seen particularly in Fig. 2, the end 72 of each passage 70 is provided adjacent to the central opening 30 and the end 72 is apart from the central opening 30 to open to the lower chamber without interference with a washer 76.The first and second passages 64 and 70 and the chamber 56 form in combination a vortex valve in which the fluid flowing from the upper chamber 1 5 to the lower chamber 1 7 therethrough will flow vortically. In practice, the second passage 70 can be formed to extend straight through the bottom, but for effectively absorbing shocks by absorbing the pressure exerted on the fluid by the vortex valve, it is desirable to increase the distance betwen the fluid inlet and the outlet, as hereafter described. Therefore, in the preferred construction, the second passage 70 is formed in a curved fashion so that the end 68 is located as close as possible to the radical center of the chamber 56.

When the shock absorber 10 is compressed, the piston 1 6 is forced downward to increase the put pressure of the fluid in the lower chamber 1 7 and decrease the pressure in the upper chamber 1 5. The fluid in the lower chamber 1 7 is thus forced through the second passages 70 into the chamber 56 of the piston 1 6 and passes into the upper chamber 1 5 through the first passages 64, as shown in Fig. 4. At this time, as shown by the arrow in Fig. 4, the fluid flowing into the chamber 56 flows directly out to the upper chamber 1 5. At this time, the vertex valve does not absorb the fluid pressure of the fluid flowing therethrough.Meanwhile, when the shock absorber is expanded or rebounds from the former compressed position, the piston 1 6 is moved upwardly to increase the pressure of the fluid in the upper chamber 1 5 and to decrease the pressure in the lower chamber 17. Thereby, the fluid in the upper chamber 15 flows into the chamber 56 of the piston 1 6 through the first passages 64 and flows out to the lower chamber 1 7 through the second passages 70, as shown in Fig. 5.At this time, since the first passage 64 is formed in the piston 1 6 in a helical fashion and the fluid flows through the helical passage to the opened end 68 which is substantially in alignment with the tangent to the circular periphery of the chamber 56, as the fluid in the chamber 56 flows vertically through the chamber 56, the pressure applied to the fluid is absorbed. Although it will be known to those skilled in the art, the following is the theory of operation of the valve as described hereabove, with reference to Fig. 6. When a pressure Pa is applied to the fluid in the upper chamber, the fluid pressure P in the circumferential direction at the point R a distance r from the circle center can be calculated by the following formulas.

First, considering the relationship of fluid flow velocity and distance from the circle center of the chamber 56, it will be obvious that: pO,. V, . r is generally constant (Formula I) where p: specific gravity of the fluid; Q: Unit volume of the fluid; and Vr: current velocity of the fluid at the point R.

As seen from the above Formula I, since the unit volume of the fluid Q and the specific gravity of the fluid p is constant, the velocity of the fluid flowing at the point R is in the following relationship with that flowing into the chamber 56 through the passage 64: Vr. r=Vc . ra (Formula II) where Vc: current velocity of the fluid flowing into the chamber 57; and ra: internal diameter of the tube 1 2.

From the above Formula II, it will be seen that the fluid will flow faster near the center of the circle. Therefore, it is apparent that the considering the flow of a unit volume of the fluid therethrough, the following formula according to Bernoulli theorem, may be derived:

Since Formula II can be changed to:

and Formula Ill can be changed to:

the relationship between the fluid pressure P at the point R and the initial fluid pressure Pa of the fluid flowing into the chamber 56 can be calculated by the following formula::

It will be appreciated that the fluid pressure P is smaller than the pressure

Therefore, if the point R is positioned closer to the circle center of the chamber 56 and thus the distance r becomes shorter, the pressure difference between P and Pa is increased. In other words, the fluid pressure P can be reduced by an amount of

from Pa. In the embodiment of the invention, the end 72 of the second passage 70 is located adjacent to the central opening 30 and the distance rto the circle center is reduced as much as possible, and thus the fluid pressure P flowing to the lower chamber 1 7 through the second passage 70 is considerably reduced. The pressure difference between Pa and P determines the shock absorption capacity of the valve means of the piston 16.

It will be appreciated that the above-mentioned embodiment can be modified in various features and constructions which act or function substantially the same as mentioned above. For example, as shown in Figs. 7 and 8, the piston 1 6 is fixedly provided with a screw 51 directed upward from the central portion of the upper surface of the top 58 thereof. The screw 51 engages in a threaded hole 53 formed in the lower end of the piston rod 26 to secure the piston16 to the rod 26.

The piston 1 6 is formed with a plurality of vertical recesses 64 spaced apart at regular intervals at the periphery 60 thereof. Each recess 64 communicates with the chamber 56 through a helical passage 65. The piston 16 is further provided with an opening 70 having a tapered periphery 71 at the lower portion thereof.

In this modification, the vortex valve may act to absorb shocks acting on the shock absorber in substantially the same way as the foregoing embodiment.

In Figs. 9 and 10 are illustrated modifications of the first embodiment of the valve means. It should be noted that in these modifications, elements and features with substantially the same construction and/or function will be represented by the same reference numerals as the forgoing first embodiment.

Further, some features and elements identical to the former embodiment will be omitted in the description herewith but shown in the drawings. In Fig. 9, there is illustrated a modification of the valve means of the first embodiment, in which the valve means includes a plurality of partitions 80 disposed in the chamber 56 to define circular fluid passages 82. In the example, the partitions 80 for segments of three circles, spaced apart from each other and from the internal peripheral surface 84 of the tube 1 2 so as to define the circular passages 82 therebetween.

The circumferential gaps between the ends of the partitions 80 define radial passages 88 through which the fluid flows when the shock absorber is compressed. The radial passages 88 extend between the ends 68 and 72 of the fluid passages 64 and 70 so as not to interfere with the flow of the fluid from the end 72 to the end 68.

When the shock absorber rebounds or is extended, the fluid flows into the chamber 56 from the upper chamber 1 5 and flows along the circular passages 82 to approach the end 72 of the passages 70 gradually. In this case, the pressure applied to the fluid can be absorbed, as described above.

In Fig. 10 is illustrated another modification of the valve means of the first embodiment.

The valve means is provided with a plurality of partitions 90 which are arranged to define a helical pasage 92 in the chamber 56. The partitions 90 are spaced apart to define also radial passages 94 for direct communication between the end 68 of the fluid passage 64 and the end 72 of the passage 70.

When the shock absorber is compressed, the fluid flows into the chamber 56 from the lower chamber through the passage 70 and directly flows to the end 68 of the passage 64 through the radial passage 94. In turn, when the shock absorber rebounds, the fluid flows into the chamber 56 from the upper chamber through the passage 64. At this time, as mentioned in the first embodiment, the fluid is forced in the circumferential directions to flow round the helical passage 92 so that the pressure applied thereto can be absorbed.

Referring to Fig. 11, there is illustrated a second embodiment of the valve means in accordance with the present invention. A piston 116 is disposed within a hollow cylindrical tube 11 2 which may be inserted in a hollow cylindrical fluid reservoir tube (not shown in Fig. 11) as illustrated in Fig. 1, for example, to form a shock absorber. The piston 11 6 is provided with a central opening 1 30 to receive the lower end of a piston rod 1 26.

The piston rod 1 26 is formed with a stepped down threaded portion 1 28 at the lower end.

The threaded portion 1 28 extends through the opening 1 30 and protrudes downward from the piston 11 6. A locking nut 1 32 is threaded on the lower end of the portion 1 28 to hold the upper surface of the piston 11 6 against a shoulder 1 29 so as to secure the piston the rod 1 26. On the outer surface of the peripheral portion 1 60 of the piston 1 30 is formed an annular groove 1 52 in which is recieved an annular sealing member 1 54 protruding outwardly from the groove 1 52 to contact sealingly and slidingly with the inner surface of the periphery of the tube 11 2. The piston 11 6 thereby, divides the internal chamber of the tube 11 2 into upper and lower chambers 11 5 and 11 7 respectively in a fluid proof manner.

The piston 11 6 is further provided with a disk-shaped chamber 1 56 therein. The chamber 1 56 is divided into upper and lower cavities 1 55 and 1 57 respectively by a substantially horizontal intermediate partition 1 59. The partition 1 59 has a central opening 161, the diameter of which is larger than that of the threaded portion 1 28 of the piston rod 126, so as to define a passage 163, around the portion 1 28 of the rod 126, which communicates between the upper and lower cavities 1 55 and 1 57. A plurality of helical passages 1 64 are formed in the piston 116, each of which has one end 1 66 opened toward the upper chamber 11 5 at the top 1 58 of the piston 11 6 and the other end 1 68 opened toward the upper cavity 1 55 at the periphery 1 60 of the piston. The passages 1 64 are spaced apart at regular intervals.Each passage 1 64 thus connects the upper chamber 11 5 and the upper cavity 1 55. The piston 11 6 is further provided with a plurality of helical passages 165, each of which has one end 1 67 opened toward the lower chamber 11 7 at the bottom 11 2 of the piston and the other end 1 69 opened toward the lower cavity 1 57 at the periphery 1 60 of the piston.

The passages 1 65 are spaced apart from one another at regular angles on the piston 11 6.

Each passage 165 thus connects the lower chamber 11 7 and the lower cavity 1 57. As mentioned in the description of the first em bodiment, at the ends 1 68 and 169, the passages 1 64 and 1 65 are directed substantially in alignment with the tangents to the circular periphery of the cavities 1 55 and 1 57 which have substantially the symmetrical construction with respect to the partition 1 69.

When the shock absorber is compressed and thus the piston is moved downward, the pressure of the fluid in the lower chamber 11 7 is increased and a decrease of pressure is created in the upper chamber 11 5. Thereby, the fluid in the lower chamber 11 7 is forced through the helical passages 165 into the lower cavity 1 57 of the piston 11 6. At this time, since the fluid flows through the helical passages 1 65 and is discharged from the ends 1 69 of the passages 1 65 in the circumferential direction toward the lower cavity 157, the fluid flows vortically in the chamber and thus, as mentioned above, the pressure applied thereto is absorbed.The fluid then flows into the upper cavity 1 55 through the passage 1 63 in the partition 1 59 and directly passes through the cavity 1 55 to the upper chamber 11 5 through the passage 1 64.

Meanwhile, when the shock absorber rebounds or is extended and thus the piston is moved upward, the pressure on the fluid in the upper chamber 11 5 increases and a decrease of pressure is created in the lower chamber 11 7. Thus, the fluid in the upper chamber 11 5 is forced through the helical passage 1 64 into the upper cavity 1 55 of the piston 11 6. At this time, since fluid flows through the helical passages 1 64 and is discharged from the ends 1 68 of the passages 1 64 in the circumferential direction toward the upper cavity 155, the fluid flows vartically in the cavity 1 55 and thus is absorbed the pressure applied thereto.Then the fluid flows into the lower room 157 and pass into the lower chamber 11 7 through the passage 1 65.

In the above second embodiment, a shock applied to the shock absorber can be absorbed during both compression and extension of the shock absorber. Thereby, it can absorb the shock more effectively and substantially twice as well as the shock absorber according to the first embodiment.

Referring now to Fig. 12, there is illustrated a shock absorber 210 of direct-acting type.

The shock absorber 210 generally comprises a inner cylindrical tube 212, an outer fluid reservoir tube 214. The cylindrical tube 212 is disposed within the fluid reservoir tube 214 and spaced from the internal periphery 218 of the tube 214 so as to define therebetween a fluid reservoir chamber 220. A piston 216 is movably disposed in the tube 212 to divide the internal space in the tube 212 into upper and lower chambers 215 and 217 respectively. The piston 21 6 is provided with a screw 251 directed upward on the upper surface of the top 258. The screw 251 screws into a threaded hole 253 formed on the lower end of a piston rod 226 to which is secured a dust-shield assembly 236 and a ring member 238.

At the upper ends of the tubes 212 and 214 are provided a rod guide 222, a pistonrod seal 234 and a helical spring 240 disposed between the rod guide 222 and the piston rod seal 234. At the upper end of the tube 21 2 and betwen the upper portion of the fluid reservoir tube 214, are further provided annular sealing members 235 on the outer periphery thereof. An end fitting 242 is fitted on the lower end of the tube 212. A ring-and cup assembly 250 is fitted on the lower end of the tube 214.

Referring to Fig. 13, there is shown in detail a third embodiment of a vortex valve formed on the piston 216 in accordance with the present invention, illustrating the piston 216 employed on the shock absorber shown in Fig. 12. The piston 216 is provided with a disk-shaped chamber 256 which communicates with the upper chamber 21 5 through a plurality of vertical recesses 264 and helical passages 265 and with the lower chamber 21 7 through a central opening 270 with a tapered periphery 271 on the lower portion thereof, formed the bottom 262 of the piston.

In the top 258 are provided a plurality of openings 280 located inward of the vertical recesses 264. A annular disk-shaped closer ring 282 in mounted on the top 258 of the piston 216. The closer ring 282 is formed with a central opening 284 through which the lower portion 228 of the piston rod 226 extends; the lower portion 228 then engages with the screw 251. The ring 282 is movable axially along the portion 228 as far as the shoulder 286 which forms a stopper for the closer ring 282 so as to limit upward movement of the ring 282. The ring 282 has an outer diameter sufficient to close the openings 280.

When the shock absorber 210 is compressed and thus the piston 216 is moved downward, the pressure on the fluid in the lower chamber 217 is increased and a decrease of pressure is created in the upper chamber 215. Thereby, the fluid is forced through the opening 270 into the chamber 256. Then, the closer ring 282 is subject to an upward fluid pressure and so moves upward to open the openings 280. The fluid can the flow into the upper chamber 21 5 through the openings 280 without the pressure thereof being absorbed. At this time, the shoulder 286 of the piston rod 226 acts as a stopper for limiting upward movement of the closer ring 282.Then, since the fluid flows merely upwardly within the chamber and to the upper chamber 21 5 through the opening 280, resistance against the fluid flow will be smaller than that flowing through the passages 265 and the vertical recesses 264.

Thereby, when the shock absorber is subject to a shock and is rapidly compressed, the fluid in the lower chamber 257 can flow into the upper chamber 215 through the piston 21 6 without being subject to considerable resistance of passage which might cause an excessive absorbing effect. Meanwhile, when the shock absorber 210 rebounds and is extended and thus the piston 216 is moved upward, the pressure on the fluid in the upper chamber 215 is increased and a decrease of pressure is created in the lower chamber 217.

At this time, the pressure applied to the fluid in the upper chamber 21 5 is exerted onto the closer ring 282 to urge the same downward toward the upper surface of the top 258 of the piston 216. Thereby, the opening 280 is closed by the closer ring 282 so as not to allow the fluid to flow therethrough. Therefore, the compressed fluid in the upper chamber 215 is forced through the vertical recesses 264 and the helical passages 265 into the chamber 256 and flows vortically therewithin. This may decrease the pressure of the fluid. The fluid then flows into the lower chamber 217.

In Fig. 1 4 is shown in detail the end fitting 242 employed in the shock absorber 210 of Fig. 1 2. The end fitting 242 comprises a generally disk-shaped body 290 having a chamber 292 therein. The body 290 is provided with openings 294 and 296 in the central portions of the top ceiling 298 and the bottom 300. The body 290 is further provided with a plurality of vertical recesses 302 on the periphery 304 thereof spaced apart from one another at regular intervals. The vertical recesses 302 communicate with the chamber 292 through a plurality of helical passages 306. Thus, the lower chamber 217 communicates with the fluid reservoir chamber 220 through the end fitting 242. A dishshaped member 308 is secured to the body 290 at a flange portion 310 by means of, for example, a plurarity of rivets 312.The member 308 is opposed to the opening 294 and has formed in it a plurality of passages 314 at regular intervals round the periphery thereof.

A closer disk 316 is disposed within the member 308 so as to face and close the opening 294. In Fig. 14, reference numeral 291 denotes a stepped upper portion of the body 290 to be engaged with the lower end of the tube 21 2 so that the external surfaces thereof form a planar cylindrical surface.

When the shock absorber is compressed and thus the piston 21 6 is moved downwardly, the fluid in the lower chamber 21 7 is put under pressure and thus the fluid pressure becomes larger than that of the fluid in the chamber 220. Therefore, the fluid is forced through the vertical recesses 302 and the helical passages 304 into the chamber 292, and passes vortically therethrough to the opening 296 and to the fluid reservoir chamber 220. At this time, the closer disk 316 is subject to fluid pressure urging it downward on to the top 298 of the body 290 to close the opening 294. Meanwhile, when the shock absorber rebounds and is extended and thus the piston is moved upward, a decrease of pressure is created in the lower chamber 21 7.

This forces, the fluid in the fluid reservoir 220 through the opening 296 into the chamber 292. Then, the closer-disk 316 is pushed up to open the opening 294 so as to allow the fluid to flow therethrough, by the fluid pressure. Therefore, the fluid in the fluid reservoir 220 can flow through the end fitting 242 without causing decreasing of pressure.

In the above embodiment, the vortex valve provided on the piston 21 6 and the vortex valve formed in the construction as above on the end fitting 242 which is fitted on the lower end of the tube 212 co-operate to absorb effectively shocks exerted on the shock absorber 210.

Figs. 1 5 and 1 6 show modifications of the piston 21 6 and the vortex valve of the end fitting 242 respectively. For simplification of explanation and for avoiding complication of reference numerals, features and elements having substantially the same construction or function will be represented by the same reference numerals as illustrated in the aboveexplained embodiment. In Fig. 15, there is illustrated a modification of the third embodiment of the vortex valve provided on the piston 21 6. In this modification, the construction of the piston 21 6 is substantially the same as that of the above-explained third embodiment. A piston rod 226 is provided with a spring seat 227 extending in the circumferential direction from the outer periphery thereof.The spring seat 227 is provided with a plurality of cutouts 229 at the peripheral portions thereof so as to allow the fluid to flowing therethrough. A helical spring 283 is disposed between the spring seat 227 and a closer ring 282 so that it may urge the closer ring 282 onto the upper surface of the top 258 of the piston 216 so as normally to close the openings 280. Meanwhile, in Fig.

16, there is illustrated a modification of the end fitting 242 in accordance with the preferred embodiment of the present invention. In this modification, the construction of the body 290 is substantially the same as that of the foregoing embodiment. A dish-shaped member 307 having a greater depth than that in the foregoing embodiment is secured to the upper surface of the ceiling 298 of the body 290 at the flange portions 309 by means of welding, for example. On the peripheral portion of the member 307, are formed a plurality of apertures 311 for communication between the space inside the member 307 and the lower chamber 217. A helical spring 313 is disposed within the member 307 and between the top 315 of the member 307 and a closer-disk 31 6 so as to urge the latter onto the upper surface of the top 298 to close the opening 294.

According to these modifications, since the closers are urged toward the tops of respectively the piston 21 6 and the valve body by the springs 283 and 313, they can prevent fluid leakage through the openings 280 and 294 when they close the openings. Further, when the shock absorber is subject to relatively weak shock and the piston is moved up and down slightly, the valve means, at least one of the vortex valve, may not response to flow the fluid in respective chambers.

Thereby, response which otherwise may caused on the shock absorber will not be taken place or will not so effect to vehicle as to move the same up and down.

In Figs. 1 7 and 18 is illustrated in detail a fourth embodiment of a valve means provided on a piston 41 6 movably disposed within a cylindrical tube 41 2. The piston 41 6 is provided with an annular groove 452 in the outer periphery 460. The groove 452 receives an annular sealing member 454 which sealingly and slidably abuts the internal surface of the periphery of the tube 41 2 to divide the internal space of the tube into upper and lower chambers 41 5 and 41 7 respectively.As shown in Fig. 17, the piston 41 6 comprises an upper member 41 9 and a lower member 421 fitted on the lower end of the peripheral portion 460 of the upper member 41 9 at a circumferential flange portion 423 thereof.

The upper and lower members 419 and 421 define, a chamber 456 within the piston 416.

In the upper member 41 9 are formed a plurality of openings 464 extending vertically through the periphery 460 of the upper member 41 9. The openings 464 communicate with the chamber 456 through helical passages 465, as shown in Fig. 18 and are closed at the lower ends by the lower member 421, as shown in Fig. 17. In the upper member is further formed an opening 466 extending through the top 458 of the member 419. A leaf-spring 468 is secured on the inner surface of the ceiling 458 by means of a screw 469 so as to releasably close the lower end of the opening 466 at the end 467 thereof. The spring 468 acts as valve as mentioned below. The lower member 421 is formed with a central opening 470 with a tapered periphery at the lower portion thereof.

In the above-explained fourth embodiment, when the shock absorber is subject to a shock and thus is compressed or rebounds, and the piston 41 6 is moved up and down, the vortex valve formed on the piston 41 6 acts to absorb the shock, as mentioned in the former embodiments. However, when the shock absorber is subject to a substantially hard shock and thus the distance between the topmost and bottommost positions of the piston becomes excessively large, the shock will be absorbed on the vortex valve means of the piston excessively so that it may cause the vehicle body to move up and down to provide rough ride thereon. Fig. 1 9 shows relationships between the absorbing function of the vortex valve of the piston and speed of thrusting of the piston.In Fig. 19, curve A shows the effect of the vertical openings 464 and the helical passages 465 for absorbing the shock; curve B shows the absorbing effect of the vortex valve of the piston 416 in response to a relatively small shock; and a curve Cshows absorbing effect in response to a substantially hard shock. As will be understood from Fig.

19, particularly by the curve C, when a substantially hard shock is exerted on the shock absorber, the pressure difference applied to the vortex valve is increased excessively.

Thereby, the shock absorber may be unable to absorb the shock. Thus if such a shock absorber is applied in a vehicle suspension, when the vehicle is submitted to a substantially hard shock, the shock absorber is apt to transmit an excessive shock shock and thus be too stiff, and cause a rough ride.

For preventing the vortex valve of the piston from effecting too much resistance to the shock, the vortex valve formed on the piston 41 6 according to the fourth embodiment, is provided with a the relief valve means comprising the leaf-spring 468. When the shock absorber is expanded too much and thus the piston is moved up to put the fluid in the upper chamber 41 5 at substantially high pressure, the leaf-spring 468 is subject to the high pressure which overcomes the spring force acting thereagainst to open the lower end of the opening 466. Thereby, the fluid in the upper chamber 41 5 flows into the chamber 456 of the piston 41 6 through the opening 466 as well as through vertical opening 464 and the helical passages 465.The absorbing effect at this time can be seen in the curve C' in Fig. 1 9. As mentioned above, in accordance with the fourth embodiment, the shock absorber can effectively absorb a shock exerted thereon.

Figs. 20 and 21 show modifications of the above-explained fourth embodiment. It should be noted that in the descriptions below, features and elements having substantially the same construction or function will be represented by the same reference numerals for simplification of explanation and for avoiding complication of reference numerals.

In Fig. 20, there is illustrated one of the modifications of the fourth embodiment. A piston 416 comprises an upper member 419 and a lower member 421. In the peripheral portion 460 of the upper member 419, a plurality of vertical openings 464 are formed.

The openings 464 communicate with an internal chamber 456 defined by the upper and lower members 419 and 421, through helical passages 465. Meanwhile, on the central portion of the lower member 421, there is formed an opening 470 with a tapered pe riphery 471 formed on the lower portion thereof. In the lower member 421 is also formed an aperture 472 vertically extending therethrough adjacent to the periphery of the member 421. The aperture 472 is located so that it may be aligned to one of the vertical openings 464 of the upper member 41 9 to directly connect an upper chamber 41 5 with a lower chamber 41 7. A thin resilient plate 468 is secured to the lower surface of the lower member 41 9 by means of a screw 469.The plate 468 is formed with a central opening 473 to be aligned with the opening 470 of the lower member 421 for defining a fluid passage. The plate 468 extends, laterally and is resiliently urged so as to releasably close the lower end 474 of the aperture 472.

In this modification, the resilient plate 468 will be pressed downwardly to open the lower end 474 of the aperture, when a substantially hard shock is exerted on the shock absorber and the piston 41 6 is moved upward to put a substantially high pressure on the fluid in the upper chamber 41 5. At this time, the upper chamber 41 5 thus communicates directly with the lower chamber 417 so that the fluid flows through the vertical openings 464 and the aperture 472 until the fluid pressure is thereby decreased to be overcome by the resilient force of the plate 472, when the plate is again urged on to the lower surface of the lower member.

By the above-mentioned function of the plate 472, the shock absorber is prevented from responding with too much resistance to a substantially hard shock.

In Fig. 21 is illustrated another modification of the fourth embodiment. In this modification, the piston 41 6 comprises an upper member 419 and a lower member 421. The construction of the lower member 421 is substantially the same as that of the fourth embodiment. The upper member 41 9 is formed with a plurality of vertical openings 464, each extending through the periphery 460 of the member 41 9. The opening 464 communicate with a chamber 456 formed within the piston and defined by the upper and lower members 419 and 421, through a plurality of helical passages 465. In the upper member 41 9 is further formed a vertical recess 472 with a bypass passage 473 for communication between the upper chamber 41 5 and the chamber 456 therethrough.The bypass passage 473 extends through the top 458 of the upper member 41 9 so as to open at a vertically intermediate point in the recess 472 at one end and to open to the chamber 456 at the other end. A disk-shaped plate 474 is movably and sealingly disposed within the recess 472. Within the recess, there is also provided a coil spring 476 seated on the bottom of the recess 472 at one end and on the lower surface of the plate 474 at the other end. The spring 476 urges the plate 474 upwardly to position the later normally above the end of the bypass passage 473 so as to cut the communication between the upper chamber 41 5 and the chamber 456. A stop per plate 478 as secured on the upper surface of the upper member 41 9 to limit upward movement of the plate 474.Apertures 480 and 482 are formed in the stopper plate 478 aligned with the recess 472 and the vertical opening 464 respectively. The opening 480 aligned with the recess 472 has a diameter smaller than that of the plate 474 so as to pass retain the plate 474. In Fig. 21, the stopper plate 478 is extended in the lateral direction to position its outer end adjacent to the outer periphery of the member 41 9 and may be secured by means of sandwiching between the lower end of the piston rod 426 and the upper member 41 9. However, it will be appreciated that since the stopper plate 478 merely acts to limit the motion of the plate 474 in the upward direction, the plate 478 can be made smaller and fitted on the upper upper surface of the member 41 9 in any way to surround the recess 472.

In this modification, when the shock absorber is subject to a substantially hard shock and thus the piston is moved upwardly to relatively high position to put on the fluid in the upper chamber a considerable valve of pressure, the plate 474 is subject to fluid pressure to be pressed down against the force of spring to position below the end of the bypass passage 473. Thereby, the bypas passage 473 is opened to the upper chamber 415 to connect the chamber 415 and 416.

Then, the fluid in the upper chamber 41 5 flows into the chamber through the bypass passage 473 and pass through the lower chamber 41 7. By the function of the plate 474 and the bypass passage 473, the shock absorber can be prevented from excessibly responsing even to substantially hard shock and can prevent the behicle from rough ride.

Referring to Fig. 22, there is illustrated a fifth embodiment of a valve means formed on a piston, a acordance with the present invention. A piston 516 is slidably disposed within a cylindrical tube which maybe inserted in a cylindrical fluid reservoir tube (not shown) to define therebetween a fluid reservoir chamber.

The interior of the tube 51 2 is divided into an upper and a lower chambers 515 and 517 by the piston 516. The piston 516 comprises an upper and lower members 519 and 521, which the lower member 521 has an annular vartial extension 523 for surrounding the lower portion of the upper member 519. The upper member 519 is secured on the lower end of a piston rod 526 by way of welding, for example. At the lower end, the piston rod 526 is formed with a lateral opening 527 which extends in the lateral direction with respect to the vertical axis of the rod 526 and has both ends opened on the outer periphery of the rod 526. The opening 527 is communicated with a vertical opening 528 which extends downwardly along the vertical axis of the rod 526 and exposed at the lower end therefrom.The upper member 51 9 is formed with an opening 529 at the central portion of the ceiling 558 thereof, which the vertical axis of the opening 529 is aligned to the vertical axis of the vertical opening 528 of the piston rod. The upper member 529 is further formed with a plurality of downwardly opened vertical recesses 564, each of which is closed at the upper end by the ceiling 528 and is exposed at the lower end. At the vertically intermediate portion of the upper member 519, there is provided a horizontal partition 524 dividing the internal space in the piston 516 defined by the upper and lower member 51 9 and 521 into upper and lower rooms 555 and 557.The rooms 555 and 557 are respectively communicated with the vertical recesses 564 through a plurality of helical passages 565 and 567 extending from the recess 564 to the rooms 555 and 557 in helical fashion.

Meanwhile, the partition 524 is provided with two openings 566 and 568, each extending vertically therethrough. At the upper surface adjacent the opening 566 and the lower surface adjacent the opening 568, the partition 524 is formed with stepped down portions 570 and 572 which are extended outwardly over the openings 566 and 568. On both of the upper and lower surface of the partition 524, there are secured thin resilient plates 574 and 576 which are secured on the central portion of the partition 524 by means of a rivet 578. The lower member 521 is formed with a central opening 580 for communication between the lower room 557 and the lower chamber 517.

When a shock is exerted on the shock absorber to compress the same and thus the piston 516 is moved downwardly, a pressure is put on the fluid in the lower chamber 517 and a vacuum is created in the upper chamber 515. Thereby, the fluid in the lower chamber 517 is forced into the lower room 557 of the piston 516 through the opening 580. In this time, since the fluid pressure in the lower room 557 is increased, the thin resilient plate 576 is urged onto the lower surface of the partition 524 to close the lower end of the opening 566, while, between the plate 576 and the stepped down portion 572 of the partition, there is defined a passage 582 through which the fluid in the lower room may flow into the opening 568.However, since the upper end of the opening 568 is resiliently closed by the thin resilient plate 574 urged thereonto, the fluid can not pass therethrough to the upper room 555 until its own pressure conquiring the resilient force of the plate 574. Therefore, the fluid in the lower room 557 normally flows to the upper room 555 through the helical passage 567, the vertical recess 564 and the helical passage 565. Then, the fluid is discharged from the helical passage 565 to the upper room 555 as whirlpool so as to be decreased the pressure and flows out from the upper room 555 to the upper chamber 515 through the openings 529, 528 and 527. If the shock exerted onto the shock absorber is substantially hard and thus the piston is moved downwardly to put a substantially high pressure on the fluid in the lower chamber 517.

The fluid pressure may exert on the resilient plate 574 and pushs up the same to open the upper end of the opening 568. Thereby, in this time, the fluid in the lower room 557 can flow into the upper chamber through the opening 568 as well as through the helical passages 567, the vertical recesses 564 and the helical passages 565. It will be understood that the plate 574 will be kept in pushed up position until the fluid pressure becoming weaker than that of the resilient force of the plate 574. Meanshile, the shock absorber rebounds or is expanded and thereby the piston is moved upwardly, a pressure is put on the fluid in the upper chamber 51 5 and a vacuum is created in the lower chamber 517. Thereby, the fluid in the upper chamber 515 is forced into the upper room 555 of the piston 516 through the openings 527, 528 and 529.In this time, since the fluid pressure in the upper room 557 is increased, the thin resilient plate 574 is urged onto the lower surface of the partition 524 to close the upper end of the opening 564, while, between the plate 574 and the stepped down portion 570 of the partition 524, there is defined a passage 584 through which the fluid in the upper room may flow into the opening 566.

however, since the lower end of the opeing 566 is resiliently closed by the thin resilient plate 574 urged thereonto, the fluid can not pass therethrough to the lower room 557 until its own pressure conquiring the resilient force of the plate 576. Therefore, the fluid in the upper room 555 normally flows to the lower room 557 through the helical passage 565, the vertical recess 564 and the helical passage 567. Then, the fluid is discharged from the helical passage 567 to the lower room 557 as whirlpool so as to be decreased the pressure and flows out from the lower room 557 to the lower chamber 517 through the opening 580. If the shock exerted onto the shock absorber is substantially hard and thus the piston is moved upwardly to put a substantially high pressure on the fluid in the upper chamber 515. The fluid pressure may exerts on the resilient plate 576 and pushs up the same to open the lower end of the opening 566. Thereby, in this time, the fluid in the upper room 555 can flow into the lower room 557 through the opening 568 as well as through the helical passages 565, the vertical recesses 564 and the helical passages 567.

While the present invention has been shown and described in detail in terms of preferred embodiments, it should not be considered as limited to these, however, or mere and simple generalizations thereof, or other detailed modifications. Further variations to any particular embodiments may be made without departing from the scope of the present invention, which it is therefore desired should be delimited and defined not by any of the perhaps purely fortuitous details of the shown embodiments, or of the drawings, but solely by the accompanying claims.

Claims (25)

1. A hydraulic shock absorber having a cylindrical hollow tube filled a hydraulic fluid and the like and a piston slidably disposed within the internal space of said tube to divide the space into an upper first chamber and a lower second chamber, the piston being secured on one end of a piston rod so as to be moved to a first lowered position when the shock absorber is compressed and to a second position when the shock absorber is expanded, wherein the improvement comprising in combination:: at least one room formed within said piston; a plurality of first passages formed on said piston for communication between one of said chambers of the tube with said room and to allow the fluid flowing in a first direction, said first passage being formed at least partly in helical fashion so that may discharge a fluid in said one of chamber to said room therethrough to generate vortex in said room for decreasing a pressure of the fluid in the room and thus for absorbing a shock; at least one second passage formed on said piston for communication between said room with the other chamber of the tube and to allow the fluid flowing in a second direction.

2. A shock absorber, as recited in claim 1, wherein said second passage is formed on substantially central portion of the piston so as to aid decreasing of the pressure during fluid flowing in the room in vortex.

3. A shock absorber, as recited in claim 1, wherein each of said first passages is opened to said one of chamber at one end thereof on the substantially horizontal outer surface of said piston adjacent the outer periphery thereof and is opened to said room at the other end thereof on substantially vertical inner periphery of the piston.

4. A shock absorber, as recited in claim 3, wherein each of said first passage is formed on the piston so that it may allow the fluid flowing in said first direction and said end opened at the inner periphery of the piston being directed so as to discharge the fluid along circular periphery of the piston for generating the vortex on the fluid in the room.

5. A shock absorber, as recited in claim 1, wherein said room of said piston is provided with a round-shaped passage substantially along the inner periphery of said piston and a radial passage radially extending from said second passage to said first passage.

6. A shock absorber, as recited in claim 5, wherein said round-shape passage is defined by coaxially provided partitions.

7. A shock absorber, as recited in claim 5, wherein said round-shaped passage is defined by helically arranged partions.

8. A shock absorber, as recited in claim 6 or 7, wherein each of said radial passage is defined between each adjacent pieces of partitions.

9. A shock absorber, as recited in claim 1, wherein said piston is further formed with at least one third passage with a closing member therefor, said closing member being movable to release from the closing position for communication between said room and said one of the chamber when the fluid flows in said second direction.

10. A shock absorber, as recited in claim 9, wherein said closing member is resiliently urged onto one end of said third opening.

11. A shock absorber, as recited in claim 1, wherein said piston is further provided with a releaf-valve means which acts to bypass the pressure fluid for limiting absorbing effect within the room of said piston when a substantially hard shock is exerted onto the shock absorber and thus said piston is moved to said first position or said section position and rebound thereagainst excessively.

1 2. A shock absorber, as recited in claim 11, wherein said releaf-valve means comprises at least a bypass passage and a resilient member releasably closing said bypass passage.

1 3. A shock absorber, as recited in claim 4, wherein said piston is provided with a horizontal partition having at least one passage thereon, said partition dividing said room into an upper portion and a lower portion which are communicated through said passage, said first passages connecting one of said portions of the room to said one of the chambers and said second passage connecting the other portion of said room to the other chamber and said second passage being at least partly in helical fashion so that may discharge a fluid in said the other portion of the room therethrough to generate vortex in the portion for decreasing a pressure of the fluid in the room and thus for absorbing a shock during flowing the fluid in said direction.

1 4. A direct-acting shock absorber having an inner hollow cylindrical tube, an outer hollower cylindrical tube spaced apart from the outer periphery of the inner tube for defining therebetween a fluid reservoir chamber, a thrusting piston sealingly and slidably disposed within the internal space of the inner tube to divide the space into an upper first chamber and a lower second chamber, a piston rod one end of which is secured to said piston and the other end is secured on a dust shield including ring member which said rod extends into the first chamber of the inner tube through guide-and-seal assembly mounted at the top of said inner tube, and an end fitting fitted to the lower end of said inner tube, said piston is formed with a valve means for communication between said first and second chambers and for flowing the fluid in a first direction which directs from the first chamber to second chamber and in a second direction which directs from the second chamber to the first chamber, wherein each of said valve means formed in the piston being vortex valves, each of said vortex valve comprising:: at least one room formed within said piston; a plurality of first passages formed on said piston for communication between one of said chambers of the tube with said room and to allow the fluid flowing in a first direction, said first passage being formed at least partly in helical fashion so that may discharge a fluid in said one of chamber to said room therethrough to generate vortex in said room for decreasing a pressure of the fluid in the room and thus for absorbing a shock; at least one second passage formed on said piston for communication between said room with the other chamber of the tube and to allow the fluid flowing in a second direction.

1 5. A shock absorber, as recited in claim 14, wherein said second passage is formed on substantially central portion of the piston so as to aid decreasing of the pressure during fluid flowing in the room in vortex.

16. A shock absorber, as recited in claim 14, wherein said room of said piston is provided with a round-shape passage substantially along the inner periphery of said piston and a radial passage radially extending from said second passage to said first passage.

1 7. A shock absorber, as recited in claim 16, wherein said round-shaped passage is defined by coaxially provided partitions.

1 8. A shock absorber, as recited in claim 16, wherein said round-shaped passage is defined by helically arranged partions.

1 9. A shock absorber, as recited in claim 1 7 or 18, wherein each of said radial passage is defined between each adjacent pieces of partitions.

20. A shock absorber, as recited in claim 14, wherein each of said first passages is opened to said one of chamber at one end thereof on the substantially horizontal outer surface of said piston adjacent the outer periphery thereof and is opened to said room at the other end thereof on substantially vertical inner periphery of the piston so that it may allow the fluid flowing in said first direction and said end opened at the inner periphery of the piston being directed so as to discharge the fluid along circular periphery of the piston for generating the vortex on the fluid in the room.

21. A shock absorber, as recited in anyone of claims 14 to 1 7 inclusive, wherein said piston is further formed with at least one third passage with a closing member therefor, said closing member being movable to release from the closing position for communication between said room and said one of the chamber when the fluid flows in said second direction.

22. A shock absorber, as recited in claim 21, wherein said closing member is urged onto one end of said third opening by resilient member.

23. A shock absorber, as recited in claim 14, wherein said piston is further provided with a releaf-valve means which acts to bypass the pressure fluid for limiting absorbing effect within the room of said piston when a substantially hard shock is exerted onto the shock absorber and thus said piston is moved too first position or second position and rebound thereagainst excessively.

24. A shock absorber, as recited in claim 23, wherein said relief-valve means comprises at least a bypass passage and a resilient member releasably closing said bypass passage.

25. A shock absorber, as recited in anyone of claims 14 to 1 7 inclusive, wherein said piston is provided with a horizontal partition having at least one passage thereon, said partition dividing said room into an upper portion and a lower portion which are communicated through said passage, said first passags connecting one of said portions of the room to said one of the chambers and said second passage connecting the other portion of said room to the other chamber and said second passage being at least partly in helical fashion so that may discharge a fluid in said the other portion of the room therethrough the generate whirlpool in the portion for decreasing a pessure of the fluid in the room and thus for absorbing a shock during flowing the fluid in said second direction.