GB1599833A

GB1599833A - Shock absorbers

Info

Publication number: GB1599833A
Application number: GB552978A
Authority: GB
Original assignee: Honda Motor Co Ltd
Current assignee: Honda Motor Co Ltd
Priority date: 1977-02-23
Filing date: 1978-02-10
Publication date: 1981-10-07
Also published as: DE2807868A1; DE7805513U1

Description

(54) SHOCK ABSORBERS (71) We, HONDA GIKEN KOGYO KABUSHIKI KAISHA, a corporation of Japan, of 27-8, 6-chome, Jingumae, Shibuya-ku, Tokyo, Japan, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to shock absorbers for vehicle use.

In general, it is desirable that a shock absorber usable in the suspension system of a vehicle has damping characteristics that can be adjusted as desired according to various service conditions such as the driver's taste in ride, the load condition of the vehicle and the road surface conditions.

This requirement is particularly strong for small-sized vehicles of limited springing weight such as motorcycles but in practice it has previously been difficult to make adjustable the damping characteristics of a shock absorber as this tends to cause substantial increase in structural complexity and manufacturing cost.

In this connection, it is generally desirable to increase the magnitude of the damping force of a shock absorber when compressed in order to prevent the shock absorber from being fully compressed as when the vehicle travels over irregular ground surfaces but, for travelling over paved roads, the damping force during compression of a shock absorber should rather be limited as any excessively large damping force during compression impairs the riding comfort. Therefore, it is desired that the damping force of a shock absorber when compressed be freely variable in accordance with the ground or road conditions, that is, according to whether the vehicle travels over irregular surfaces or paved roads.

Also, unless the compression damping force and the expansion damping force of a shock absorber are properly adjusted relative to each other, an undesirable phenomenon is likely to occur in which the body of the vehicle gradually goes down or floats up, particularly when the vehicle travels over a rough road at relatively high speeds. Further, the effect upon the rider's feeling of the adjustment of the compression damping force is larger than that of the adjustment of the expansion damping force made at the same rate. Accordingly, it is desirable for a shock absorber to be arranged and constructed so that both the expansion and compression damping forces of the shock absorber are adjustable and that the range of adjustment of the compression damping characteristic and that of the expansion damping characteristic are made different from each other as required.

In addition, in view of the fact that such adjustment of the damping characteristics is to be effected frequently in accordance with the load, road and other driving conditions, the shock absorber should be of such a design as to require only a minimum of time or labour for adjustment of the damping characteristics.

Moreover, since in the suspension system any increase in upsprung weight should be avoided as far as possible, it is desirable to minimize any weight increase of a shock absorber as may be required to make variable its damping characteristics.

According to the present invention there is provided a shock absorber, for vehicle use, comprising: a hydraulic cylinder that is for mounting between members of the suspension system of a vehicle respectively associated with the body of the vehicle and a wheel assembly of the vehicle for moderating the force of impact due to relative movement between these members; a first and a second oil chamber defined in the cylinder by a partition; oil passage means formed in the partition and extending therethrough to intercommunicate the first and second oil chambers; a valve mechanism provided to control flow of oil through the oil passage means; and an adjusting mechanism for adjusting the operating characteristic of the valve mechanism from outside the cylinder; tho valve mechanism including: a resilient plate-like annular valve element arranged co-axiallv with the partition in a pOsition adjacent one of the end openings of the oil passage means and deflexible in accordance with the oil pressure differential between the first and second oil chambers; a valve element seat means having a movable portion movable with deflection of the valve element such that the valve element is in valve-closed position as long as the amount of deflection of the valve element is not larger than a preset value, and adapted to be held against further movement. when the amount of deflection of the valve element exceeds said preset value, to permit the valve element to assume a valve-open state with a clearance defined between the movable portion of the valve element seat means and at least part of the peripheral region of the valve element in correspondence with the amount of deflection of the valve element; an orifice means for allowing a preset flow of oil through the oil passage means even when the valve element is in valve-closed position; and control means adapted to selectively limit the extent of movement of the movable portion of the valve element seat means by operation of the adjusting mechanism; the valve element seat means comprising: a first annular valve seat member having a first annular valve seat for supporting the outer peripheral edge portion of the valve element on one face thereof; and a second annular valve seat member having a second annular valve seat for supporting the inner peripheral edge portion of the valve element on the other face thereof; one of the valve seat members having one or more controlling surface(s) arranged thereon along a circle concentric with and different in radius from the annular valve seat thereof, the controlling surface(s) varying in height in a circumferential direction of the valve seat member, and the other valve seat member having feet formed thereon along a circle concentric with and different in radius from the annular valve seat thereof in positions corresponding to the controlling surface(s) the feet extending one and the same distance from said other valve seat member toward the controlling surface(s); said other valve seat member being arranged for rotation about the axis of the valve element seat means and for axial sliding movement relative to said one valve seat member whereby when the two valve seat members are disposed in axially fixed spaced apart positions the axial distance of the feet from the controlling surface(s) is varied when said other valve seat member is rotated relative to said one valve seat member by the adjusting mechanism.

For a better understanding of the invention and to show how the same may be carried out into effect, reference will now be made, by way of example, to the accompanying drawings, in which: Figure 1 is a side view, partly in cross section, of the whole structure of a shock absorber for vehicle use; Figure 2 is an exploded perspective view of part of the shock absorber shown in Figure 1; Figure 3 is a fragmentary longitudinal cross-sectional view of another part of the shock absorber shown in Figure 1, taken along the line III-III in Figure 6; Figure 4 is a transverse cross-sectional view taken along the line IV-IV in Figure 3; Figure 5 is a fragmentary side view of that portion of Figure 3 which is indicated by the arrow V; Figure 6 is a transverse cross-sectional view taken along the line VI-VI in Figure 3; Figure 7 is a perspective view of a torque-transmitting spring of the shock absorber shown in Figure 1; Figures 8 to 10 are views similar to Figure 3, showing the shock absorber of Figure 1 in different stages of operation; Figure 11 is a damping characteristic curve diagram of the shock absorber shown in Figure 1; Figure 12 is a view similar to Figure 3 of another form of shock absorber for vehicle use; Figure 13 is a perspective view of a valve-seat member and associated tubular member shown in Figure 12; Figure 14 is a perspective view of an anti-turn washer used in the shock absorber of Figure 12; Figure 15 is a damping characteristic curve diagram of the shock absorber of Figure 12; Figure 16 is a view similar to Figures 3 and 12, showing a further form of shock absorber; Figure 17 is an exploded perspective view of a piston and valve assembly shown in Figure 16; Figure 18 is a transverse cross-sectional view taken along the line XVIII-XVllI in Figure 16; Figure 19 is a plan view of an anti-turn washer shown in Figure 16; Figure 20 is a damping characteristic curve diagram of the shock absorber shown in Figure 16; Figure 21 is a side view, partly in cross section, showing the whole structure of another form of shock absorber; Figure 22 is an enlarged fragmentary cross-sectional view, taken along the lines XXII-XXII in Figures 23 and 24, showing in upper half a piston valve assembly and in lower half a bottom valve assembly of the shock absorber shown in Figure 21; Figure 23 is a transverse cross-sectional view taken along the line XXIII-XXIII in Figure 22; Figure 24 is a view similar to Figure 23, taken along the line XXIV-XXIV in Figure 22; Figure 25 is an exploded perspective view, showing components of the shock absorber of Figure 21 in their assembling order; Figure 26 is a damping characteristic curve diagram of the shock absorber shown in Figure 21; and Figure 27 is a view similar to Figure 21, showing a modification of the shock absorber of Figure 21.

Referring to the drawings and first to Figure 1. there is illustrated a preferred form of shock absorber, as generally indicated by reference numeral 1. The shock absorber 1 includes an upper mounting member 2 adapted to be secured to a vehicle frame portion of the suspension system and a lower mounting portion 3 adapted to be secured to the associated wheel assembly.

The upper mounting member 2 is screw threadably fitted over the upper extreme end portion of a piston rod 4 of a piston and piston rod assembly, and is integrally secured thereto. A piston 6 of the assembly, and a valve mechanism 5 provided thereon are carried on the lower end portion of the piston rod 4. Secured as by welding to the lower mounting member 3 is a sealing cap 8 which hermetically seals a cylinder 7 at its bottom.

The piston 6, being slidably fitted in the cylinder 7. divides the interior space thereof into oil chambers 10 and 11, which are in fluid communication with each other through oil passages formed in the piston 6.

as will be described later in detail. The flow of oil through the oil passages is controlled by the valve mechanism 5 and the operating characteristic of the latter is adjustable by means of an adjusting mechanism 9.

The lower oil chamber 11 is in communication with an accumulator 13 through an oil line connected to the sealing cap 8. The accumulator 13 is connected to a source of oil supply, not shown, and serves the purpose of maintaining the cylinder 7 in a state at all times filled with an appropriate amount of hydraulic oil.

A spring-force adjuster means 14 is fixedly secured around the outer peripheral surface of the cylinder 7 by well-known means in a manner such as to be held against axial movement relative thereto during use of the shock absorber 1. The spring-force adjuster 14 and the upper mounting member 2 are both formed with a flange portion and a coiled suspension spring 15 is arranged between the flange portions in encircling relation to the cylinder 7 and piston rod 4. A cushion block 16 is fitted around the periphery of the piston rod 4 at a location close to its junction with the upper mounting member 2 to prevent direct abutting engagement of the top of the cylinder 7 with the mounting member 2 as when the shock absorber 1 is fully compressed.

Referring to Figures 1 and 2, an adjusting nut 18 is fitted in the cylinder 7 at the top end thereof, with use of a snap ring 17. The adjusting nut 18 is formed with a through hole centrally thereof to freely receive the piston rod 4 and also formed on the top side with a hexagonal head 19 to be readily engageable with an appropriate tool. Further, the adjusting nut 18 is formed in its outer peripheral edge portion with a pair of radially extending slots 20 and 20' in positions diametrally opposite to each other.

Arranged on the inside of the adjusting nut 18 is a spring washer 26 having a central aperture through which the piston rod 4 freely extends. The spring washer 26 has an outer diameter substantially the same as that of the adjusting nut 18 and is formed around the outer periphery thereof with a large number of springy fins 27 which are flexed alternately in opposite directions, as shown. Reference numerals 28, 28' indicate a pair of diametrally opposite notches formed in the outer periphery of the spring washer 26.

Fitted in the cylinder 7 on the inside of the spring washer 26 is a rod guide 21 which is held in liquid-sealing contact with the inner peripheral wall surface of cylinder 7 by way of an O-ring 24 and has a central bore through which the piston rod 4 is guided in its sliding movement. The rod guide 21 is held against axial movement relative to the cylinder 7 by means of a snap ring 29. The rod guide 21 has an upper tubular portion which defines therein an annular space in cooperation with the piston rod 4. A pair of lugs 22 and 22" are formed on the tubular portion in positions diametrally opposite to each other, extending upwardly from the top edge thereof. The lugs 22 and 22' are held engaged in respective notches 28, 28' formed in the spring washer 26 and in respective slots 20, 20' formed in the adjusting nut 18 so that the spring washer 26 and rod guide 21 are rotatable simultaneously around the piston rod 4 when the adjusting nut 18 is driven to rotate around the piston rod 4 by appropriate tool means. The spring washer 26 with its fin formation serves to urge the adjusting nut 18 and the rod guide 21 in directions opposite to each other thereby to prevent any play of the adjusting nut 18 and rod guide 21 relative to respective snap rings 17 and 29.

A sealing element 25 is fitted in the annular space in the upper tubular portion of rod guide 21 for sealing engagement with the piston rod 4 so that any axial leakage of hydraulic oil from the upper oil chamber 10 otherwise occurring along the peripheral surface of piston rod 4 is effectively prevented. Also, the rod guide 21 is formed on its bottom end face at a location adjacent the outer peripheral edge thereof with a downwardly projecting driver arm 23 which is held in engagement with engaging portions 58 of a torque-transmitting member of the valve mechanism 5, as will be described later.

Referring next to Figure 3 to 7, the piston rod 4 has a reduced-diameter bottom end portion 30 on which the valve mechanism 5 and piston 6 are mounted. Specifically, a washer 31 is fitted to the reduced-diameter portion 30 at the upper, base end thereof and the piston 6 is fitted thereto directly adjacent to the washer 31. The piston 6 has a tubular portion 36 extending upwardly into abutting engagement with the washer 31. Further, on the underside of piston 6, the reduced-diameter portion 30 of piston rod 4 is fitted with a washer 33 and a nut 34.

The nut 34 is screen threaded on the reduced-diameter portion 30 tightly against the washer 33 and piston 6 and held in place by appropriate lock means. A cushion spring 35 is arranged between the washer 31 and the bottom end face of rod guide 21 to serve the purpose of alleviating the shock arising upon expansion of the shock absorber 1.

Referring particularly to Figures 3 and 4, the piston 6 is formed on the inner wall surface of its central bore with a chordal flat rib 37 at a location adjacent the bottom end face of the piston and the flat surface of the rib 37 is held in close contact with a flat side 38 of the reduced-diameter piston-rod portion 30 so that the piston 6 is restrained against any rotation relative to the piston rod 4.

Formed on the top side of the piston 6 around the outer periphery thereof is an annular ridge 39 which defines at its top three sets of controlling flat surfaces, each including three such surfaces X. Y and Z arranged at regular intervals within a 1200 range and raised to successively higher levels, as seen in Figures 4 and 5.

Inside the annular ridge 39. the piston 6 is formed on its top side with an annular valve seat 45 and a plurality of oil passage bores 40 are formed vertically through the piston at equi-circumferential distances, opening at one end in the annular top surface defined between the valve seat 45 and the base of tubular portion 36 of the piston 6. Limiting projections 41 are formed on the annular top surface of the piston, each in a position between two adjacent oil passage bores 40, to serve the purpose of limiting the amount of deflection of a valve element 59, which will be described later in detail.

Referring now to Figures 4, 6 and 8, the tubular portion 36 of the piston 6 is formed at the top in the outer peripheral surface thereof with three pairs of diametrally opposite recesses 42, 42'; 43, 43'; 44, 44'. An annular valve seat member 46 is fitted over the tubular portion 36 for rotation and axial sliding movement relative thereto.

Referring to Figures 3 and 6, the valve seat member 46 is chamfered to form three equi-circumferentially spaced flats 47, 48 and 49 on the outer periphery thereof.

Formed in the top side of the valve seat member 46 is a cavity 50 which extends radially from the central region of the member 46 to the periphery thereof and has a fixed substantial width. An arcuate projection 51 is formed on the bottom of the cavity 50 and an adjusting-torque transmitting wire spring member 55 is fitted in the cavity 50 which is shaped to resiliently embrace the arcuate projection 51 and the tubular portion 36 of piston 6, as shown in Figure 6.

As clearly shown in Figure 7, the torquetransmitting wire spring 55 is generally of bifurcated form. including a looped portion 56, a pair of opposite flexed portions 57 and 57' bent convexly toward each other. and a pair of parallel upstanding portions 58 and 58'. It will be appreciated that if the legs of the spring 55 are forced away from each other, each leg including flexed and upstanding portions 57-58 or 57'-58'. this will be against the action of the resiliency of the wire spring per se. As mounted in the cavity 50, the torque-transmitting spring 55 has its flexed portions 57, 57' resiliently fitted in one pair of recesses 42,42 43.43'; or 44, 44', formed in the tubular portion 36 of the piston 6 in positions diametrally opposite each other. At the same time. those leg portions extending between the flexed (57, 57') and upstanding (58. 58') portions are resiliently held on the arcuate projection 51 at the opposite ends thereof. Similarly, the upstanding portions 58. 58' are resiliently held against the tip portion of the driver arm 23 on the opposite sides thereof. With this arrangement, when the driver arm 23 is driven to rotate around the piston rod 4, the torque is transmitted through the adjustingtorque transmitting spring 55 to the valve seat member 46, causing the member 46 to rotate relatively to the piston 6 around the tubular portion 36 thereof.

Formed on the underside of valve seat member 46 are three downwardly extending feet 52, 53 and 54 which are arranged at equal intervals along a circle of the same radius as the annular ridge on the piston 6 so as to be placed vertically opposite, respectively, three controlling flat surfaces X, Y or Z of the same height, one in each of the three sets of such surfaces formed on the piston. Specifically, these feet 52, 53 and 54 are placed opposite the respective controlling flat surfaces X when the flexed portions 57, 57' of the torque-transmitting spring 55 snap into the impaired recesses 42, 42' in the tubular piston portion 36, are placed opposite the respective controlling flats Y when the flexed spring portions 57, 57' snap into the recesses 43, 43', and are placed opposite the respective controlling flats Z when the flexed spring portions 57, 57' snap into the recesses 44, 44'.

An annular valve seat 61 is also formed on the underside of the valve seat member 46 radially inside feet 52. 53 and 54 and an annular valve element 59 formed of resilient sheet material is arranged under the valve seat member 46. The top and bottom faces of the valve element 59 are resiliently held in pressure contact with the valve seat 61 of the valve seat member 46 and the seat 45 of the piston 6, respectively, around the inner and outer peripheries of the valve element.

In this manner, the valve seat member 46 is normally biased in a direction away from the piston 6 under the action of the valve element 59 with the feet 52, 53 and 54 held spaced from the respective controlling flat surfaces of the piston 6.

The valve element 59 is made of a plurality of annular resilient sheets overlying each other and one of the resilient sheets which is closest to the piston 6 is formed wih a plurality of radially extending notches around the outer periphery thereof.

These notches define orifices 60 in cooperation with the valve seat on the piston 6.

In the shock absorber 1 constructed as described above, the oil pressure in the upper oil chamber 10 is raised, when the shock absorber is forced to expand, to exceed that in the lower oil chamber 11 so that the valve seat member 46 and the valve element 59 are pushed toward the piston 6, as shown in Figure 8. On this occasion, the inner peripheral region of valve element 59 is deflected downwardly toward the piston 6 while the valve seat 61 of the valve seat member 46 is held in contact with the valve element 59 so that there arises a flow of hydraulic oil from the upper oil chamber 10 into the lower chamber 11 through orifices 60 and oil passages 40. The damping characteristic of the shock absorber in this instance is illustrated by a curve a in Figure 11, in which the abscissa represents the piston speed and the ordinate in the upper region represents the expansion damping force, that in the lower region representing the compression damping force.

As the expanding force acting on the stock absorber 1 is increased, the valve seat member 46 is further displaced toward the piston 6 until the feet 52, 53 and 54 come into abutting engagement with the respective controlling flats X, Y or Z of the piston 6. Subsequently, as the expanding force on the shock absorber 1 is further increased to raise the speed of the piston 6 relative to the cylinder 7, the valve element 59 is moved apart from the valve seat 61 of the valve seat member 46, allowing an additional flow of hydraulic oil from the upper oil chamber 10 into the lower chamber 11 through the annular clearance now defined between the valve element 59 and valve seat 61. The damping characteristic of the shock absorber 1 at this instance is shown by a solid line b, in Figure 11.

The clearance between the valve element 59 and valve seat 61 is increased with rise of the piston speed but, once the inner peripheral edge portion of the valve element 59 is placed in abutting engagement with the limiting projections 41 formed on the top of the piston 6, such clearance cannot be increased any further and the damping characteristic subsequently follows a quadratic curve, as indicated by the right-hand end portion of solid line b2 in Figure 11.

In the diagram of Figure 11, the position of the point at which curve a is joined with solid line b2 depends upon the distance of travel allowed for the valve seat member 46 relative to the piston 6, which distance in turn depends upon the spacing between the feet 52, 53 and 54, on the one hand, and the respective controlling flat surfaces X, Y or Z of the piston 6, on the other hand. Now assuming that the adjusting nut 18 is turned by an appropriate tool, the turning torque is transmitted to the valve seat member 46 through the rod guide 21 and the adjustingtorque transmitting spring 55, which is held in engagement with the driver arm 58 of the rod guide 21 so that the valve seat member 46 is rotated stepwise relative to the piston 6 by way of selective engagement of the flexed portions 57 and 57' of the adjusting-torque transmitting spring 55 with the recesses 42, 42'; 43, 43'; 44, 44'. Simultaneously with this, the feet 52, 53 and 54 of the valve seat member 46 are selectively placed in positions opposite the respective controlling flats X, Y or Z of the piston 6 and in this manner the allowable distance of travel of the valve seat member 46 relative to the piston 6 is set in a stepwise fashion. In this embodiment, in which the height of the controlling flat surfaces X is the largest and that of the controlling flat surfaces Z is the smallest, the damping characteristic curve of the shock absorber 1 is represented by the broken line b, in Figure 11 when the feet 52, 53 and 54 are in positions opposite the respective controlling flats X; by the solid line b2 when the feet 52, 53 and 54 are opposite the controlling flats Y; and by the chain-dotted line b3 when the feet 52, 53 and 54 are opposite the controlling flats Z.

Now suppose that the shock absorber 1 is subjected to a compressive force so that the oil pressure in the lower oil chamber 11 becomes higher than that in the upper oil chamber 10. This time, there arises a flow of hydraulic oil from the lower oil chamber 11 into the upper chamber 10 through the oil passages 40 and the orifices 60 and the damping characteristic at this instance is represented by the curve a' in Figure 11.

Subsequently, when the compressive force acting on the shock absorber 1 is increased and the speed of the piston 6 is raised accordingly. the valve element 59 is deflected in the manner illustrated in Figure 10 to form an annular clearance between the valve element 59 and the valve seat 45. The damping characteristic at this instance is represented by the line c in Figure 11. In this connection, where the valve seat member 46 is provided with appropriate controlling projections (not shown) for limiting the amount of deflection of the valve element 59, the damping characteristic curve will be quadratic in the higher range of piston speed, as indicated at c' in Figure 11.

Another embodiment is illustrated in Figures 12 to 15, in which the same references have been retained, with primes affixed as required, for similar parts which have the same functions as in Figures 1 to 10.

In this embodiment, there is provided in place of the tubular portion 36 of the piston 6 in the previous embodiment a separate tubular member 36' which is fitted over the reduced-diameter bottom end portion 30 of the piston rod 4 and held against rotation relative thereto by a flat rib 37' formed on the inner wall surface of the member 36' so as to be held in contacting engagement with the flat side 38 of the reduced-diameter portion 30 of the piston rod 4. Reference numeral 6' indicates a piston fitted over the tubular member 36'.

The piston 6' has formed on its top an annular ridge 39' on top of which controlling flat surfaces quite similar to those X. Y and Z shown in Figures 4 and 5 are formed. The piston 6' is formed on its top radially inside the annular ridge 39' with an annular valve seat 45' which is normally held in spring contact with the outer peripheral portion of the bottom face of an annular valve element 59' formed of resilient sheet material.

Further, inside the annular valve seat 45', the piston 6' is formed with a plurality of circumferentially spaced oil passage bores 40' which extend axially through the annular thin-walled section thereof. Limiting projections 41' are formed on the top of the piston 6' between the oil passage bores 40' to serve the purpose of limiting the amount of deflection of the valve element 59'. Interposed between the tubular member 36' and nut 34 is an anti-burn washer 69 which is formed on its inner periphery with a chordal rib 70 for engagement with the side flat 38 on the reduced-diameter portion 30 of the piston rod 4. On the outer periphery of the washer 69 is formed a pawl or upturned lug 71 which is fitted in an engaging slot 72 formed in the wall of one of the oil passage bores 40' in piston 6'. In this manner, the piston 6' is held together with the tubular member 36' against rotation around the piston rod 4 but is axially movable relative to the tubular member 36'.

Referring to Figure 13, three pairs of diametrally opposite recesses 62, 62'; 63.

63'; 64, 64' are formed in the outer peripheral surface of the tubular member 36' at the top edge thereof. The recesses 62, 62'; 64, 64' are formed of an axial length just enough to receive the flexed portions of adjusting-torque transmitting spring 55 while the remaining recesses 63. 63' each have an axial length much larger than that of the recesses 62, 62'; 64, 64'.

Fitted over the tubular member 36' is a valve seat member 46' which is formed on its underside with an annular valve seat 61' which is normally held in contact with the top face of the valve element 59' along the inner periphery thereof. The valve seat member 46' is formed therein with a cavity like the cavity 50 in the valve seat member 46 shown in Figure 6, and is formed on the bottom of this cavity with an arcuate projection 51' which is clamped by the adjustingtorque open at one end in the bottom end face thereof inside the valve seat 61' and at the other end in the upper portion of the inner wall surface of the axial bore, formed in the valve seat member 46'.to receive the tubular member 36'. For simplicity's sake, one of the through apertures 65, 66 or 67 in each pair which is arranged diametrally opposite the other one shown is omitted in Figure 13.

It is to be noted that the paired through apertures 65, 66 and 67 have different diameters varying in the order named and, as the valve seat member 46' is rotated around the piston rod 4 by means of the adjusting mechanism 9, are selectively placed in fluid communication with the recesses 63, 63' in the tubular member 36' thereby to intercommunicate the upper and lower oil chambers 10 and 11. It will thus be noted that, in this embodiment, the through apertures 65, 66 and 67 serve as orifice means providing for stepwise control of the rate of oil passage between the oil chambers by selective communication with the recesses 63 and 63'.

In Figure 15 are illustrated the damping characteristic curves of the shock absorber 1 shown in Figures 12 to 14. In Figure 15, the chain-dotted line represents the damping characteristic obtainable when one of the pairs of through apertures 65, 66 and 67 having the least diameter are in fluid communication with the recesses 63 and 63'; the broken line represents the damping characteristic obtainable when the paired through apertures of the largest diameter are in fluid communication with the recesses 63 and 63'; and the solid line represents the damping characteristic obtainable when the paired through apertures of the medium diameter are in communication with the recesses 63, 63'. It is to be recognized, therefore, that in this embodiment of Figures 12 to 15 the damping characteristic of the shock absorber can be adjusted more finely than in the case of the previous embodiment because of the orifice means in effect adjustable in diameter.

Another embodiment is illustrated in Figures 16 to 20, in which the same references have been retained for similar parts which have the same functions as in the previous embodiment shown in Figures 1 to 10.

Referring first to Figures 16 and 17, a tubular member 73 is fitted over the reduced-diameter bottom end portion 30 of the piston rod 4 and is formed on the wall of the axial bore with a flat rib 73' which is held in engagement with the side flat 38 on the reduced-diameter end portion 30. Again, three pairs of recesses 74, 74'; 75, 75'; 76, 76' are formed in the outer peripheral surface of the tubular member 73 at the top thereof, such recesses in each pair being positioned diametrally opposite each other.

Recesses 74, 74 in one of the three pairs of recesses are formed in an axial length sufficient to receive the paired flexed portions 57 and 57' of an adjusting-torque transmitting spring 55 shown in Figure 18 while the other paired recesses 75, 75'; 76, 76' have an axial length substantially larger than that of the recesses 74, 74', as clearly seen in Figure 17.

A piston 93 is fitted over the tubular member 73 adjacent the bottom thereof and is formed on the top along the outer peripheral edge thereof with an annular ridge 94 and an annular valve seat 95 which extends inside the annular ridge 94 for contacting engagement with the outer peripheral edge portion of the bottom face of an annular valve element 104, which is formed of resilient sheet material. The valve seat 95 is formed therein with a plurality of circumferentially spaced radially recessed grooves 96, which in cooperation with the valve element 104 share the function of orifice means when the valve element 104 is is contact with the valve seat 95, formed on the piston 93.

The piston 93 has a plurality of oil passage bores 97 arranged radially inside the valve seat 95 at appropriate circumferential spacings and extending through the piston axially thereof. Limiting projectins 98 are formed on the top face of the piston 93 each between two adjacent oil passage bores 97 to serve the purpose of limiting the amount of deflection of the valve element 104.

Radially further inside the oil passage bores 97 are formed three sets of controlling flat surfaces X', Y' and Z' which serve the same function as the surfaces X, Y and Z formed on the piston 6 shown in Figure 4.

Fitted over the reduced-diameter portion 30 of the piston rod 4 between the tubular member 73 and nut 34 is an anti-turn washer 101 which is formed on the inner periphery thereof with a chordal rib 102 for engagement with the side flat 38 on the reduceddiameter portion 30 of the piston rod 4, as seen in Figure 19. A lug 103 is also formed on the washer 101 which extends radially outwardly from the outer periphery of the washer so as to be held engaged between a pair of lugs 100 and 100', which extend downwardly from the underside of the piston 93. With this arrangement, it will be noted that the piston 93 is restrained together with the tubular member 73 against rotation relative to the piston rod 4 but is axially movable relative to the tubular member 73.

An annular control element 77 is fitted over the tubular member 73 in a position adjacent the top thereof for rotation and axial sliding movement relative to the tubular member 73. A pair of notches 78 and 78' are formed in the annular control element 77 at the top thereof in positions diametrally opposite each other. Also, two pairs of radially extending diametrally opposite small apertures 79, 79'; 80, 80' are formed in the wall of the control element 77 in positions adjacent and below the notches 78, 78'. It is to be noted that the distance between each two adjacent small apertures 79-80 and 79'-80' is equal to the centre distance between each two adjacent recesses 75-76 and 75'-76' formed in the tubular member 73. Provided on the annular control element 77 are three equally spaced feet 81, 82 and 83 which extend downwardly from the bottom end of the element 77 and are faced opposite that region of the top face of the piston 93 which is the radially inner portion of the controlling surfaces or flats X', Y' and Z'.

A valve seat member 84 is fitted over the outer periphery of the annular control element 77 for free sliding movement relative thereto. The valve-seat member 84 has formed therein a cavity 85 similar to the cavity 50 formed in the valve seat member 46 shown in Figure 6. Provided in the bottom of the cavity 85 is an arcuate projection 86 which is clamped between the legs of an adjusting-torque transmitting spring 55, which is mounted in the cavity 85.

The flexed portions 57, 57' of the spring 55 as mounted extend radially inwardly through the respective notches 78 and 78', formed in the annular control element 77, and are snappingly engageable with any one of the three pairs of recesses 74, 74'; 75, 75'; 76, 76' formed in the tubular member 73 upon stepwise rotational operation of the adjusting mechanism 9. Also, a pair of recesses 87, only one of which is shown in Figure 17 for simplicity's sake, are formed in the inner peripheral surface of the valveseat member 84 and adjacent the bottom thereof in positions diametrally opposite each other. In the state of the valve seat member 84 assembled with the annular control element 77, the top portions of recesses 87 are held in fluid communication with the respective sets of closely spaced small apertures 79-80 and 79'-80' formed in the annular control element 77 while the recesses 87 are held downwardly open at the bottom of the valve seat member 84.

Formed on the underside of the valve seat member 84 are an annular valve seat 89 which engages the top face of valve element 104 around the inner periphery thereof and a plurality of limiting projections 88 which are arranged radially outside the valve seat 89 at appropriate circumferential spacings to serve the purpose of limiting the amount of deflection of the valve element 104. Also, formed on the underside of the valve seat member 84 in positions radially inside of the valve seat 89 are three downwardly projecting feet 90, 91 and 92 which are circumferentially equally spaced from each other, facing downwardly toward that annular region of the top of the piston 93 which is the radially outer portion of the controlling surfaces or flats X', Y' and Z' of the piston 93. These feet 90, 91 and 92 are all equal in height of projection like the feet 81, 82 and 83 formed on the annular control element 77. In the state of the valve seat member 84 assembled with the annular control element 77, the feet 90, 91 and 92 of the valve seat member 84 are held in phase with the respective feet 81, 82 and 83 of the annular control element 77 in overlying relation with the feet 81, 82 and 83. In this connection, it is to be noted that the length or height of projection of the feet 90, 91 and 92 of the valve member 84 is smaller than that of the feet 81, 82 and 83 of the annular control element 77. Because of this, regardless of which one of the three sets of flats X'. Y' and Z' the feet 81-83 and 90-92 are placed opposite, the distance over which the valve seat member 84 travels, upon expansion of the shock absorber 1, toward the piston 93, following the valve element 104 being deflected is at all times greater than the distance over which the piston 93 travels, upon compression of the shock absorber 1, toward the valve seat member 84, following the deflection of the valve element 104.

With such arrangement, it will be readily appreciated that the expansion and compression damping characteristics of the shock absorber 1 are effectively differentiated and thus the phenomenon of vehicle floating or sinking, which impairs the riding comfort, can be appropriately alleviated.

In this embodiment, when the valve seat member 84 and annular control element 77 are turned around the tubular member 73 by operation of the adjusting mechanism 9, the two sets of small apertures 79, 80 and 79', 80', in the annular control element 77 are positioned stepwise so as to be both closed completely by the outer peripheral surface of the tubular member 73 or to place either one or both of the two pairs of recesses 75.

75'; 76, 76', formed in the tubular member 73, selectively in fluid communication with the recesses 87 in the valve seat member 84.

In other words, with this arrangement, the upper oil chamber 10 can be placed in fluid communication with the lower oil chamber 11, as desired, through either one or both of the two pairs of recesses 75, 75'; 76, 76', either one or both of the two pairs of small apertures 79, 79'; 80, 80', and the paired recesses 87 and, in this manner. the two pairs of small apertures 79, 79': 80, 8()' in cooperation with the recessed grooves 96 formed in the valve seat of the piston 93 function as orifice means. In addition, the two pairs of small apertures 79, 79'; 80, 80' jointly operate as a variable orifice since either one or both of the pairs of such small apertures are selected, as desired, upon rotation of the valve seat member 84 and annular control element 77 relative to the tubular member 73, as described above, and, simultaneously with this, the allowable distance of axial movement of the valve seat member 84 and annular control element 77 relative to the piston 93 is adjusted stepwise.

It will thus be readily recognized that the damping characteristics of the shock absorber 1 can be adjusted expediently in a fine manner.

Figure 20 illustrates the damping characteristic curves of the shock absorber shown in Figures 16 to 19. In this figure, the chain-dotted lines represent the damping characteristics obtainable when the two pairs of small apertures 79, 79'; 80, 80' are completely closed by that portion of the outer peripheral surface of the tubular member 73 which lies immediately below the recesses 74, 74' and the valve-seat member 84 and annular control element 77 are angularly positioned relative to the tubular member 73 so that the feet 90, 91 and 92 of the valve seat member 84 and the feet 81, 82 and 83 of the annular control element 77 are held in positions opposite the controlling surfaces or flats X' on the piston 93, which are the highest in level of all the sets of controlling surfaces formed on the pistion 93; the solid lines represent the damping characteristics obtainable when only one of the two pairs of small apertures 79, 79'; 80, 80' are in fluid communication with either one of the two pairs of recesses 75, 75'; 76, 76' in the annular control element 77 and the valve seat member 84 and annular control element 77 are angularly positioned relative to the tubular member so that the feet 90-92 of the valve-seat member 84 and the feet 81-83 of the annular control element 77 are held in positions opposite the controlling flats Y' of the piston 93. which are of the medium height.

and the broken lines represent the damping characteristics obtainable when the two pairs of small apertures 79, 79'; 80, 80' are in communication with the respective pairs of recesses 75, 75'; 76, 76' and the valve seat member 84 and annular control element 77 are angularly positioned relative to the tubular member 73 so that the feet 90-92 of the valve seat member 84 and the feet 81-83 of the control element 77 are held in positions opposite the controlling flats Z' of the piston 93, which are of the least height.

In each of the embodiments described hereinbefore, it will be readily understood that the piston 6, 6' or 93 and the valve seat member 46, 46' or 84 together constitute valve supporting means, and that the piston 6, 6' or 93 also serves as a first annular valve-seat member for the valve element 59 or 104, the valve-seat member 46, 46' or 84 serving as a second valve-seat member therefor.

In any of the previous embodiments, the shock absorber for vehicle use is provided with an adjusting mechanism for conveniently adjusting the operating characteristics of the valve mechanism from outside and, owing to this, the damping characteristics of the shock absorber can be readily adjusted as desired by extremely simple operation in accordance with the driving conditions of the vehicle. Moreover, the shock absorber is provided with a valveelement seat means operative to hold the valve element in its closed state unless the amount of deflection of the latter exceeds a preset value and to place the valve element in an open state when the amount of deflection thereof exceeds the preset value and is also provided with orifice means arranged between the upper and lower oil chambers to allow only a preset flow of oil therebetween when the valve element is in closed position and the valve element itself is so constructed and arranged as to be resiliently deformed in a manner such that its opening extent varies in accordance with the oil pressure differential between the oil chambers on the opposite sides of the piston. The shock absorber, therefore, can exhibit damping characteristics at all times suited to the magnitude and quality of the shock load as applied to the shock absorber.

Furthermore, the damping characteristics of the shock absorber can be freely changed as required owing to the provision of control means making it possible to selectively limit the amount of displacement of the valveelement seat means by operation of the adjusting mechanism.

A further embodiment is illustrated in Figures 21 to 25. Referring first to Figure 21, a damper is mounted, on the one hand, on the wheel side of the suspension system of a vehicle, for example, on the rear-wheel swing arm of a motorcycle as by bolt means by way of a lower yoke 111 and, on the other hand, on the frame of the vehicle as by bolt means by way of an upper bracket 112.

The damper includes a tubular outer casing 113 secured to the yoke 111 and a piston rod 114 secured to the bracket 112 and slidably received in the tubular casing 113. This damper developes a damping force against axial movement of the piston rod 114 relative to the tubular casing 113 as occurring when the assembly is compressed and expanded between the vehicle frame and the wheel. A coiled suspension spring 115 is arranged in a conventional manner between the upper bracket 112 and the tubular casing 113, on which a spring adjuster 116 is securely mounted by any known means to support the suspension spring 115 at the bottom thereof and is operable to adjust the vehicle height according to the load condition of the vehicle. In order to absorb the shock occurring if the suspension assembly be compressed to a full extent as when the vehicle travels over rough roads. a rubber bumper 117 is mounted on the piston rod 114 adjacent its top in concentric relation thereto.

Incorporated in the top end portion of tubular casing 113 is a rod guide 118 with an oil seal 119 fitted therein. Reference numeral 120 indicates a damper adjuster which is incorporated above the rod guide 118 and plays an additional role of holding the oil seal 119 in place. The rod guide 118 is formed around the outer periphery thereof with an annular groove to receive an O-ring 121, which prevents oil leakage between the tubular casing 113 and the rod guide 118. As shown, the rod guide 118 is reduced in outer diameter adjacent its bottom end and a cylinder 122 is fitted at its top end over the reduced-diameter bottom end portion of rod guide 118 with a driver element 123 disposed therebetween.

Fitted in the tubular casing 113 at the bottom end thereof is a bottom cap 124 through the intermediary of which the tubular casing 113 and yoke 111 are integrally welded together. Incorporated in the hollow inside of the bottom cap 124 is a bottom valve 125 which is so designed as to produce a damping force of selectable intensity upon compression of the damper 110 while allowing free passage of hydraulic oil during the expansion stroke of the damper. The structure of the bottom valve 125 will be described later in detail. The cylinder 122 is fitted at its bottom end in the bottom valve 125 by means of an "inro" formation so as to define an annular space between the tubular casing 113 and the cylinder 122.

Secured to the bottom end of piston rod 114 is a piston valve assembly 126 which is slidably received in the cylinder 122 to divide the interior space therein into an upper and a lower oil chamber 127 and 128 and includes a valve mechanism the construction of which is described below.

Reference will next be had to the upper half of Figure 22 and Figure 23. in which the structure of the piston valve assembly 126 is shown in detail.

The piston rod 114 has a reduceddiameter bottom end portion formed to define an annular shoulder 130 at the top thereof and on which end portion are fittingly assembled a number of components, including a rebound stop 131, a waved spring washer 132, a control plate 133, a piston 134, a collar 140, a valve plate 135, a spring retainer 136, a valve spring 137 and a washer plate 138 in the order named.

These components are all secured together by means of a nut 139 which is screw threaded over the reduced-diameter portion of piston rod 114 at its bottom. In this assembly, the valve plate 135 and spring retainer 136 are arranged in concentric relation to the collar 140 for free sliding movement relative to the outer peripheral surface thereof. The nut 139 once screw threaded over the bottom end of the piston rod 114 under a prescribed magnitude of torque is additionally tightened in order to prevent it from working loose.

The piston 134 is provided around the outer periphery thereof with a seal means 141 which serves as a hydraulic seal between the upper and lower oil chambers 127 and 128 defined in the cylinder 122 by the piston 134. The piston 134 is formed in the bottom face inside a depending skirt portion thereof as well as in the top face thereof with two concentric annular grooves 153-154 or 153'154'. Of these annular grooves, four in all, the inner annular grooves 153, 153' are connected with each other by two axially extending oil passages 142 formed through the piston 134 and similarly the outer annular recesses 154, 154' are interconnected through two axially extending oil passages 143 formed in the piston 134. The two annular grooves 153-154 in the top face, when the control plate 133 is positioned as illustrated, are covered by the control plate while, of the annular grooves 153'-154' in the bottom face, only the inner one 153' is covered by the valve plate 135. That outer peripheral portion of the piston 134 which extends over the piston seal 141 is arcuately recessed in a wavering fashion with a series of diametrically opposite depressions 144. in which a pair of anti-turn lugs or pawls 149 formed on the control plate 133 are resiliently fitted, as will be described later in further detail. A recess 145 is formed in the bottom end face of the downwardly extending skirt portion of piston 134 to serve as a positioning mark, as will be described hereinafter.

As clearly shown in Figure 23, the control plate 133 is formed with two pairs of orifices 146 and 147 arranged on respective circles of the same diameters as those of the two annular grooves 153 and 154 formed in the top face of the piston 134. The orifices 146 or 147 in each pair of such orifices are arranged in positions diametrally opposite each other. As will be described later in detail, these orifices 146 and 147 are designed to control the damping force of the piston valve assembly 126 when the damper 110 is extended. Also, as shown in Figure 25, the control plate 133 is formed along the outer periphery thereof with a pair of upturned lugs or pawls 149 and a pair of downturned lugs or pawls 149 in positions spaced 90 degrees from each other. The downturned pawls 149 are sprung into the depressions 144 formed in the top periphery of the piston 134 to control the angular phase relation of the control plate 133 to the piston 134. On the other hand, the upturned pawls 148 are placed in engagement with respective slits 150A formed in a pair of downwardly extending fork-like pawls 150, which are formed on the driver element 123.

The damper adjuster 120. rod guide 118 and driver element 123 are engaged with each other to form an integrated structure rotatable about the axis of the assembly. Therefore, when the damper adjuster 120 is turned from outside by an appropriate tool, its rotation is transmitted to the control plate 133 so that the latter is rotated relatively to the piston 134 about the axis thereof.

Referring next to Figures 21 and 22, a coiled rebound spring 152 is arranged between the rebound stop 131 and rod guide 118 in encircling relation to the piston rod 114 in order to alleviate the shock in rebounding.

In assembling the bracket 112 and piston 134 on the piston rod 114. they are accurately positioned relative to each other so that the recess 145 in the bottom end of the skirt portion of the piston 134 is held in predetermined phase relation to a given line of radius of the bracket 112.

Referring to the lower half of Figure 22 and Figures 24 and 25. the bottom valve 125 is constituted of an adjuster cap 160, a one-way spring 161, an annular control element 162, a stack of control discs 163, an orifice plate 164 and a bottom piece 165, as will be described below in detail.

The adjuster cap 160 has a pair of slitted groove-like depressions 160A formed in the top periphery thereof in positions spaced 180 degrees from each other and fitted in respective positioning recesses 162A formed in the periphery of the control element 162.

The adjuster cap 160 is also formed with another pair of similar depressions 160B in positions spaced 90 degrees from the depressions 160A to serve the purpose of axially guiding the control element 162. In this manner, the control element 162 is held against rotation relative to the adjuster cap 160 but is axially freely slidable relative thereto.

The lower portion of the adjuster cap 160 extending below the depressions 160A and 160B is circular in cross section and carries along the bottom edge thereof a pair of radially inwardly bent pawls 160C which are vertically aligned with respective depressions 160A and a pair of radially outwardly bent pawls 160D which are vertically aligned with respective depressions 160B. The lower portion of adjuster cap 160, which is of circular cross section, is fitted in the cylinder 122 at the bottom thereof in hydraulically sealed relation thereto. The inturned pawls 160C are slidably fitted in a peripheral groove 166 formed around the outer periphery of the bottom piece 165. In order to facilitate the assembling of the adjuster cap 160 on the bottom piece 165, the latter has a pair of axially extending grooves 167 formed in the outer peripheral surface thereof in positions circumferentially spaced 180 degrees from each other and opening at the bottom end to the peripheral groove 166. The axial grooves 167 are both of a width sufficient to allow passage of the inturned pawls 160C of the adjuster cap 160 through such grooves into the annular groove 166. The outturned pawls 160D at the bottom of the adjuster cap 160 are loosely fitted in respective slits 122A formed in the bottom edge of the cylinder 122 so that the adjuster cap 160 and cylinder 122 are rotatable as an integrated unit. The top wall of the adjuster cap 160 is generally flat and is formed therein with a set of four oil holes 160E.

The annular control element 162 is formed on the bottom face thereof with a central projection 162B, which is held tightly in contact with the inner peripheral edge of the topmost of control discs 163, and three feet 162C, which are arranged at equal spacings along the outer periphery of the control element 162 and extend downwardly to one and the same horizontal plane. The element 162 is also formed therein with a set of four oil holes 162D, which extend vertically through the element 162.

The control discs 163 are formed of spring steel or the like resilient sheet material and stacked together. In cases of such stack formation, the number of discs used therein is determined according to the characteristics required thereof. Arranged directly beneath the control discs 163 in superimposed relation thereto, the orifice plate 164 is substantially the same as the control discs 163 in diameter as well as in thickness of any one of its discs and is formed around the outer periphery thereof with a plurality of slits 164A. The orifice plate 164 is held around the periphery thereof in pressure contact with a seat face 168 defined on the bottom piece 165 under the bias of the one-way spring 161. The bottom piece 165 is formed centrally thereof with an axial oil bore 171 which is conically enlarged at the top and connected at the bottom with a pair of diametral grooves 169, formed in the bottom face of the bottom piece 165 and extending at right angles to each other. In this manner, the oil bore 171 is in fluid communication with the annular space around the cylinder 122 through the diamet ral grooves 169 crossing each other on the axis of the bottom piece 165. The bottom cap 124 is partly press-worked to form a rib 124A inside thereof and which rib is received in one of the bottom grooves 169 in the bottom piece 165 to hold the latter against rotation relative to the bottom cap 124.

As best shown in Figure 25, the bottom piece 165 is formed at its top with three sets of flat surfaces 165A, 165B and 165C of successively different heights, which are arranged at regular intervals on a circle of substantially the same radius as the circle on which the feet 162C of control element 162 are arranged. The one-way spring 161 is so designed as to exert a spring force on the control element 162 which is smaller than the restoring force of the resilient discs 163 and orifice plate 164, which acts against the spring force. With this arrangement, the control discs 163 are not deflected, remaining flat as shown in Figure 22, as long as the oil pressure differential across the bottom valve 125 remains below a preset value. In the meantime, the feet 162C of the control element 162 are held spaced a definite distance from the respective flat surfaces formed on top of the bottom piece 165 with the central projection 162B on the bottom of its control element 162 remaining in contact with the stack of discs 163 and orifice plate 164 to close the through bore extending axially thereof. It is to be noted that the three feet 162C, arranged circumferentially at equal intervals and having the same axial length, are at all times held opposite respective flat surfaces 165A, 165B or 165C of the bottom piece 165, which are of the same height, irrespective of the angular position of the control element 162 relative to the bottom piece 165.

When the damper adjuster 120 is driven to rotate by an appropriate tool, the cylinder 122, fitted at the top over the rod guide 118, is rotated about its own axis through the medium of the rod guide 118. As a consequence, the control element 162, which is held engaged with the adjuster cap 160 held in engageme expansion damping force, that in the lower region representing the compression damping force. As observed in this diagram, the damping characteristic of the damper when expanded is shifted successively upward from the bottom line ("weak") to the top line ("strong") through the intermediate line ("medium") as the flow resistance of annular grooves 153 and 154 is increased.

Referring again to Figure 22, when the piston 34 rises in the expansion stroke, the control element 162 in the bottom valve assembly 125 is raised against the bias of the one-way spring 161. which is comparatively small, to allow free flow of hydraulic oil from the annular space defined around the cylinder 122 into the lower oil chamber 128 therein so that there is no occurrence of any substantial damping force.

On the other hand, when the piston 134 is lowered in the compression stroke, the control disc 163 and orifice plate 164 are held in close contact with the respective seat surfaces, as shown in Figure 22 so that there occurs a damping force as determined bv the orifices in the form of slits 164A in the orifice plate 164. The damping characteristic curve in this instance, therefore, generally takes a quadratic form, as indicated in Figure 26 at a.

If the speed of descent of the piston 134 is increased to such an extent that the oil pressure differential across the bottom valve 125 exceeds a first preset value, the oil flow through the orifices or slits 164A in the orifice plate 164 is accordingly increased so that the control discs 163 begin to deflect into dish form and finallv the feet 162C of the control element 162 come into contact with the top end face of the bottom piece 165. The control element 162 can now no longer descend despite the downward urge of the one-way spring 161. In this connection. the distance between the feet 162C of the control element 162 and the top end face of the bottom piece 165 and hence the amount of initial deflection of the control discs 163 are variable in accordance with the angular setting given to the bottom piece 165 by turning the damper adjuster 120, in a stepwise fashion owing to the stepped top end formation (165A, 165B, 165C) of the bottom piece 165 or, if desired, in a continuous fashion with an appropriate continuous top end formation thereof.

Subsequently. as the speed of descent of the piston 134 is further increased, the control discs 163 are further deflected and separate from the seat surface of the central projection 162B on the control element 162 when the oil pressure differential across the bottom valve 125 exceeds a second preset value. At this time, the damping characteristic curve is flexed from its quadratic portion a in Figure 26 to rise at a reduced rate. The position of the flex point of the damping characteristic curve depends upon the lower limit position of the seat surface of the central projection 162B on the control element 162. This means that the damping characteristic can be changed by varying the lower limit position of the control element 162 with the aid of the stepped top end formation of the bottom piece 165.

In cases where the speed of descent of the piston 134 is increased still further, the damping characteristic may be readily adjusted, if desired, so that the damping force is increased in such a manner as indicated in Figure 26 by the broken lines by providing appropriate means (not shown) for restricting the axial oil bore 171 formed in the bottom piece 171.

A modification of the embodiment illustrated in Figures 21 to 25 is shown in Figure 27. In this modification, a circlip 180 is interposed between the damper adjuster 120 and tubular casing 113 of the damper to hold the adjuster 120 and associated parts in place thereby to make it possible to obtain a desired definite level of friction between the damper adjuster 120 and the tubular casing 113 while enabling disassembling of the damper adjuster 120 and associated parts.

Further, in order to ensure contacting engagement between the circlip 180 and associated parts, a conical spring washer 181 of substantial stiffness is inserted between the bottom piece 165 and bottom cap 124 thereby to apply a substantial upward thrust to the calked top edge portion of tubular casing 113. The remaining components of this modified form of damper are the same in structure as those used in the embodiment shown in Figures 21 to 25.

In the embodiment of Figures 21 to 25 and its modification of Figure 27, the damper constitutes a shock absorber: and the rod guide 118, damper adjuster 120 and driver element 123 together form a rotating means of the shock absorber: the piston valve 126 and bottom valve 125 respectively forming a first and a second damping mechanism of the shock absorber. The depressions 144 in the piston 134 and the pawls 149 on the control plate 133 jointly constitute rotation-restraining means of the shock absorber; the control element 163 forms a valve-element presser member of the shock absorber: the stack of control discs 163 and orifice plate 164, cooperating with each other, form a valve element of the shock absorber: the bottom piece 165 forms a valve seat member for the valve element; and the sets of flat surfaces 165A, 165B and 165C on top of the bottom piece 165 together serve as means for controlling the amount of axial displacement of the valveelement presser member and hence of the valve element in the shock absorber.

According to these embodiments, the shock absorber is provided with a first damping mechanism for damping expanding movement and a second damping mechanism for damping compression movement of the shock absorber, each of such mechanisms being capable of exhibiting various damping characteristics for movement in the direction concerned despite of its simple structure. Because of this, the shock absorber is not only simple in structure and easy to assemble, allowing ready renewal of parts as required, but is also reliable in operation and can readily put into practical application. In addition, the first and second damping mechanisms are designed individually to serve their own functions and their damping characteristics are readily adjustable by simple operation.

In particular, the second damping mechanism, including a valve-seat member, a valve element, a valve element presser member and a displacement control means, each obtainable in simple form, is itself reliable in operation and easy to assemble, allowing ready replacement of parts when required, and enables the weight of the whole assembly to be reduced to an extreme extent.

Further, it is to be noted that, among others, the valve element is deflexible in cooperation with the valve-element presser member and the displacement controlling means in a precise and reliable fashion according to the magnitude of oil pressure differential across the second damping mechanism, that is, according to whether the oil pressure differential remains below a first preset value, exceeds the first preset value while remaining below a second preset value, or exceed the second preset value.

Owing to this, the flow of hydraulic oil through the valve unit can be closely controlled in an effective manner so as to enable the damper to have its damping characteristics efficiently controlled as required.

In addition, since the displacement controlling means is designed to variably control the amount of axial displacement of the valve-element presser member toward the valve seat member, the damping characteristics of the shock absorber can be freely varied as desired according to the driving conditions such as the load condition of the vehicle and the road surface conditions.

Whilst the provision of sets of controlling surfaces and co-operating feet has been described, only one set of controlling surfaces and co-operating feet could be provided.

WHAT WE CLAIM IS: 1. A shock absorber. for vehicle use, comprising: a hydraulic cylinder that is for mounting between members of the suspension system of a vehicle respectively associated with the body of the vehicle and a wheel assembly of the vehicle for moderating the force of impact due to relative movement between these members; a first and a second oil chamber defined in the cylinder by a partition; oil passage means formed in the partition and extending therethrough to intercommunicate the first and second oil chambers; a valve mechanism provided to control flow of oil through the oil passage means; and an adjusting mechanism for adjusting the operating characteristic of the valve mechanism from outside the cylinder; the valve mechanism including: a resilient plate-like annular valve element arranged co-axially with the partition in a position adjacent one of the end openings of the oil passage means and deflexible in accordance with the oil pressure differential between the first and second oil chambers: a valve element seat means having a movable portion movable with deflection of the valve element such that the valve element is in valve-closed position as long as the amount of deflection of the valve element is not larger than a preset value, and adapted to be held against further movement, when the amount of deflection of the valve element exceeds said preset value, to permit the valve element to assume a valve-open state with a clearance defined between the movable portion of the valve element seat means and at least part of the peripheral region of the valve element in correspondence with the amount of deflection of the valve element; an orifice means for allowing a preset flow of oil through the oil passage means even when the valve element is in valve-closed position: and control means adapted to selectively limit the extent of movement of the movable portion of the valve element seat means by operation of the adjusting mechanism; the valve element seat means comprising; a first annular valve seat member having a first annular valve seat for supporting the outer peripheral edge portion of the valve element on one face thereof; and a second annular valve seat member having a second annular valve seat for supporting the inner peripheral edge portion of the valve element on the other face thereof; one of the valve seat members having one or more controlling surface(s) arranged thereon along a circle concentric with and different in radius from the annular valve seat thereof, the controlling surface(s) varying in height in a circumferential direc

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. According to these embodiments, the shock absorber is provided with a first damping mechanism for damping expanding movement and a second damping mechanism for damping compression movement of the shock absorber, each of such mechanisms being capable of exhibiting various damping characteristics for movement in the direction concerned despite of its simple structure. Because of this, the shock absorber is not only simple in structure and easy to assemble, allowing ready renewal of parts as required, but is also reliable in operation and can readily put into practical application. In addition, the first and second damping mechanisms are designed individually to serve their own functions and their damping characteristics are readily adjustable by simple operation. In particular, the second damping mechanism, including a valve-seat member, a valve element, a valve element presser member and a displacement control means, each obtainable in simple form, is itself reliable in operation and easy to assemble, allowing ready replacement of parts when required, and enables the weight of the whole assembly to be reduced to an extreme extent. Further, it is to be noted that, among others, the valve element is deflexible in cooperation with the valve-element presser member and the displacement controlling means in a precise and reliable fashion according to the magnitude of oil pressure differential across the second damping mechanism, that is, according to whether the oil pressure differential remains below a first preset value, exceeds the first preset value while remaining below a second preset value, or exceed the second preset value. Owing to this, the flow of hydraulic oil through the valve unit can be closely controlled in an effective manner so as to enable the damper to have its damping characteristics efficiently controlled as required. In addition, since the displacement controlling means is designed to variably control the amount of axial displacement of the valve-element presser member toward the valve seat member, the damping characteristics of the shock absorber can be freely varied as desired according to the driving conditions such as the load condition of the vehicle and the road surface conditions. Whilst the provision of sets of controlling surfaces and co-operating feet has been described, only one set of controlling surfaces and co-operating feet could be provided. WHAT WE CLAIM IS:

1. A shock absorber. for vehicle use, comprising: a hydraulic cylinder that is for mounting between members of the suspension system of a vehicle respectively associated with the body of the vehicle and a wheel assembly of the vehicle for moderating the force of impact due to relative movement between these members; a first and a second oil chamber defined in the cylinder by a partition; oil passage means formed in the partition and extending therethrough to intercommunicate the first and second oil chambers; a valve mechanism provided to control flow of oil through the oil passage means; and an adjusting mechanism for adjusting the operating characteristic of the valve mechanism from outside the cylinder; the valve mechanism including: a resilient plate-like annular valve element arranged co-axially with the partition in a position adjacent one of the end openings of the oil passage means and deflexible in accordance with the oil pressure differential between the first and second oil chambers: a valve element seat means having a movable portion movable with deflection of the valve element such that the valve element is in valve-closed position as long as the amount of deflection of the valve element is not larger than a preset value, and adapted to be held against further movement, when the amount of deflection of the valve element exceeds said preset value, to permit the valve element to assume a valve-open state with a clearance defined between the movable portion of the valve element seat means and at least part of the peripheral region of the valve element in correspondence with the amount of deflection of the valve element; an orifice means for allowing a preset flow of oil through the oil passage means even when the valve element is in valve-closed position: and control means adapted to selectively limit the extent of movement of the movable portion of the valve element seat means by operation of the adjusting mechanism; the valve element seat means comprising; a first annular valve seat member having a first annular valve seat for supporting the outer peripheral edge portion of the valve element on one face thereof; and a second annular valve seat member having a second annular valve seat for supporting the inner peripheral edge portion of the valve element on the other face thereof; one of the valve seat members having one or more controlling surface(s) arranged thereon along a circle concentric with and different in radius from the annular valve seat thereof, the controlling surface(s) varying in height in a circumferential direc

tion of the valve seat member, and the other valve seat member having feet formed thereon along a circle concentric with and different in radius from the annular valve seat thereof in positions corresponding to the controlling surfaces(s) the feet extending one and the same distance from said other valve seat member towards the controlling surface(s); said other valve seat member being arranged for rotation about the axis of the valve element seat means and for axial sliding movement relative to said one valve seat member whereby when the two valve seat members are disposed in axially fixed spaced apart positions the axial distance of the feet from the controlling surface(s) is varied when said other valve seat member is rotated relative to said one valve seat member by the adjusting mechanism.

2. A shock absorber as claimed in claim 1, wherein said controlling surface(s) of said one valve seat member comprise(s) a set or sets of surfaces, the or each set of which comprises a plurality of surfaces increasing in height successivelv at a fixed rate in a circumferential direction of the valve seat member within their respective set or sets.

3. A shock absorber as claimed in claim 1, wherein said controlling surface(s) of said one valve seat member comprise(s) a single surface which increases continuously in height in a circumferential direction of the valve seat member.

4. A shock absorber as claimed in claim 2 wherein said feet of said other valve member are disposed one in each set of the controlling surfaces.

5. A shock absorber as claimed in any one of the preceding claims, wherein said partition is a piston connected to a piston rod; wherein said one annular valve seat member is formed on this piston; and wherein said other annular valve seat member is mounted on this piston rod.

6. A shock absorber as claimed in any one of the preceding claims wherein the valve element is formed of a plurality of annular resilient sheets which overly each other and one of which is radially notched to constitute at least part of the orifice means in cooperation with the valve seat region of said first or said second valve seat member.

7. A shock absorber as claimed in claim 5, or claims 5 and 6. in which there is provided an adjusting-torque transmitting spring which is held in engagement with said other annular valve seat member and which includes at least one projecting portion and one engaging portion engageable with a driver element of the adjusting mechanism, the projecting portion being formed so as to resiliently fall, as said other valve seat member is rotated relative to said one valve seat member by operation of the adjusting mechanism, into a selected one of a plurality of recesses formed, in an outer peripheral surface of a tubular member fixedly mounted on the piston rod, in positions circumferentially adjacent each other.

8. A shock absorber as claimed in claim 7. wherein said tubular member is integrally formed with said piston.

9. A shock absorber as claimed in any one of the preceding claims, wherein at least one of the first and second annular valve seat members is formed thereon with controlling projection means for defining a maximum amount of deflection of the valve element.

10. A shock absorber as claimed in claim 7, wherein at least one of said recesses is formed so as to extend over a certain axial length, and wherein said other valve seat member is formed therein with a plurality of small apertures of different cross-sectional areas for intercommunicating oil spaces on the opposite sides of the valve element irrespective of the operating condition of the valve element so that, when said other valve seat member is rotated relative to said one valve seat member, one of said small apertures is selectively placed in fluid communication with the, or one of the recess(es) having a certain axial length, thereby to complete the orifice means.

11. A shock absorber as claimed in claim 7 and further comprising a tubular control element fitted around the outer peripheral surface of the piston rod and operatively associated with the valve seat members such that said one valve seat member is axially movable relative to the piston rod over a preset distance and said other valve seat member is axially movable relative to the piston rod over a preset distance different from that preset for said one valve seat member.

12. A shock absorber as claimed in claim 11, wherein one or more of said recesses is/are formed so as to extend over a certain axial length, and wherein the control element has one or more small apertures formed therein for intercommunicating oil spaces on the opposite sides of the valve element irrespective of the operating condition thereof, the control element being arranged to rotate together with said other valve seat member, when this valve seat member is rotated relative to said one valve seat member, so that said small apertures, constituting said orifice means, are all closed completely or one (or more) thereof is (are) selectively placed in fluid communication with the (or with one or more of the) recess(es) having a certain axial length.

13. A shock absorber substantially as hereinbefore described with reference to Figures 1 to 11, or Figures 12 to 15, or Figures 16 to 20, or Figures 21 to 26 or Figure 27 of the accompanying drawings.