GB1582586A

GB1582586A - Shock absorber piston assembly

Info

Publication number: GB1582586A
Application number: GB4651877A
Authority: GB
Original assignee: Monroe Auto Equipment Co
Current assignee: Tenneco Automotive Inc
Priority date: 1977-06-13
Filing date: 1977-11-08
Publication date: 1981-01-14
Also published as: ES464262A1; IT1087987B; JPS547073A; SE433769B; FR2394717B1; AU3058477A; DE2751046C2; FR2394717A1; SE7713025L; AR216775A1; DE2751046A1; BR7708450A; JPS568217B2; CA1096410A; AU513256B2

Description

(54) SHOCK ABSORBER PISTON ASSEMBLY (71) We, MONROE AUTO EQUIP MENT COMPANY, a corporation organised and existing under the laws of the State of Delaware, of one International Drive Monroe, Michigan 48161 United States of America, 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 a piston assembly for use in hydraulic shock absorbers.

It has heretofore been the practice in the construction of piston assemblies for vehicle shock absorbers to utilize valving arrangements of the single valve disc type and also of the multiple valve disc type. A typical single valve disc piston arrangement is shown in the Specification of French Patent No. 2,146,611, while a typical multiple valve disc arrangement is shown in the Specification of United States Letters Patent No. 3,134,460. Each of these valving arrangements has been subject to certain objections from shock absorber manufacturers and it is a general object of the present invention to provide an improved piston assembly which reduces or overcomes certain problems which have arisen in prior single-disc and multiple-disc piston valving designs. The use of single-disc valving requires that both the rebound and compression loading on the valves be matched. Consequently, it is very difficult to provide accurate adjustment of the rebound loading of such a shock absorber design without changing the compression loading thereof. A related problem relates to the fatiguing of the valve parts which in turn results in certain performance limitations in order to ensure against premature valve failure.

Insofar as the multiple-disc valve arrangements mentioned above, the pistons associated therewith have been found to be relatively expensive to manufacture and although permitting independent changes of the compression and rebound control, such multipledisc piston valving, such as shown in the aforementioned United States Patent Specification No. 3,134,460, has been found to be objectionable from the standpoint that the bleed control on rebound and compression cannot be changed independently of one another. Because low speed control has become significantly more important in modern automotive vehicles, such independent control of the rebound and compression loading on low, as well as high, velocity piston movements has become almost mandatory.

According to the present invention there is provided a shock absorber piston assembly comprising: first and second coaxially arranged piston members each having radially inwardly and outwardly sets of axially extending flow ports, a compression valve assembly disposed adjacent one side of one of said piston members, a rebound valve assembly disposed adjacent one side of the other of said piston members, each of said compression and rebound valve assemblies comprising at least one disc-like valve member movable toward and away from an associated valve seat, and an intake valve assembly disposed between said piston members for selectively controlling fluid flow between certain of said flow ports of one of said members and certain of said flow ports of the other of said members, said intake valve assembly comprising first and second disc-like intake valve members, one of said members being cooperable with a valve seat on one of said piston members and the other of said valve members being co-operable with a valve seat on the other of said piston members, and a common spring element interposed between and arranged coaxially of said first and second valve members for resiliently biasing the same toward engagement with the associated valve seats, said compression, rebound and intake valve assemblies comprising the entire valve means for controlling fluid flow within the shock absorber whereby to permit changing the rebound and compression characteristics of said shock absorber solely by changing an appropriate one or ones of said valve members.

The rebound valve assembly disposed adjacent one side of one of the piston members consists of one or more valve discs and an associated orifice disc. In a similar manner, the preferred compression valve assembly disposed adjacent the opposite side of the other of the piston members likewise includes one or more valve discs and an associated orifice disc. With this arrangement, it is possible to use rebound and compression orifice discs which are completely different and hence may be adjusted independent of one another for modifying low speed control during both rebound and compression.

Another feature of the aforementioned preferred construction resides in the fact that the valve discs of the compression and rebound valve assemblies may comprise different size and thickness valve discs (or valve discs of the same size and different thickness or the same thickness and different sizes), whereby the blow-off control of the piston may be controlled independently of one another during both rebound and compression operation of the piston.

By disposing a spacer member directly adjacent the rebound and compression valve discs, the thickness of the spacer member may be controlled so as to provide for further blow-off control.

High speed control may be effected by controlling the size of the selected of the flow ports in one of the piston members and similarly controlling the size of selected of the flow ports in the other of the piston members.

A related earlier construction is shown in the Specification of United States Letters Patent No. 3,134,460; wherein multiple piston bodies are depicted, however, one critical difference between this prior design and the present invention resides in the fact that in the prior piston, each piston body gives part of the rebound control and part of the compression control, and it is not possible to have an independent bleed control as is the case with the present invention wherein one piston member gives rebound control and the other piston member gives compression control.

The present invention will become further apparent from the following detail description given by way of example of a preferred embodiment taken in conjunction with the accompanying drawing, in which: Figure 1 is a longitudinal cross-sectional view of a typical automotive vehicle shock absorber embodying the present invention; Figure 2 is an enlarged fragmentary crosssectional view of the piston assembly of the shock absorber of Figure 1; and Figure 3 is an exploded assembly view of the piston assembly shown in Figure 2.

Referring now to Figure 1 of the drawing, a shock absorber unit ]0, in accordance with one preferred embodiment of the present invention, is shown generally as comprising a pressure cylinder 12 having a reciprocable piston assembly 14 disposed therein. The assembly 14 is mounted on one end of a reciprocable piston rod 16 which has the opposite end thereof projecting axially outwardly from the cylinder 12 and provided with an end fitting 18. The opposite end of the cylinder 12 is provided with another end fitting 20, whereby the unit 10 may be operatively mounted between the sprung and unsprung portions of the associated vehicle for damping relative movement therebetween, as is well known in the art. The shock absorber unit 10 is provided with a dirt shield assembly 22 which includes a cylindrical section 24 arranged coaxially of the piston rod 16 and spaced radially outwardly from the outer periphery of the cylinder 12, as illustrated. The section 24 is connected to the piston rod 16 by means of a generally cup-shaped end member 26.

The interior of the cylinder 12 is provided with a fluid chamber 28 within which a quantity of hydraulic damping fluid is located, and also with a pressurized gas chamber 30, the chambers 28 and 30 being separated by a floating piston member 32 in a manner well known in the art.

Referring now in detail to the construction and operation of the piston assembly 14 as best seen in Figure 2, the piston rod 16 is provided with a reduced diameter end section 34 which is defined by a generally radially disposed shoulder 36 and includes an externally threaded terminal end portion 38 upon which a suitable nut 40 is threadably received for retaining the assembly 14 in its operative position upon the piston rod 1 6. The piston assembly 14 comprises a pair of identical piston bodies or members, one of which is identified by the numeral 42 and the other of which is identified by like numerals with a prime (') suffix, with the following description of the piston body 42 being applicable to both bodies 42 and 42'. As best seen in Figure 2, the piston body 42 is provided with a first plurality of circumferentially spaced axially extending flow ports 44 and with a second plurality of circumferentially spaced axially extending flow ports 46 that are located radially inwardly from the flow ports 44. The upper side of the piston body 42 defines an upper surface 48 which is formed with an annular valve seat 50 that is located radially between the flow ports 44 and 46 and extends concentrically around the upper side of the body 42. The lower side of the piston body 42 is defined by a bottom surface 52 which is in tum formed with a pair of coaxially arranged radially inner and outer valve seats 54 and 56.

As illustrated, the valve seat 54 is arranged generally axially below the valve seat 50, while the valve seat 56 is arranged radially outwardly from the outer plurality of flow ports 44. It is to be noted that in the assembly 14, the piston body 42' is inverted relative to the piston body 42, with the result that the valve seats 54' and 56' extend upwardly from the piston body 42', as opposed to extending downwardly as is the case with the piston body 42. The piston body 42 is formed with a central annular opening 57 which is adapted to receive the reduced diameter end section 34 of the piston rod 16, with the body 42' being formed with an identical central opening 57' and being adapted to likewise receive the end section 34, with the result that the piston bodies 42, 42' will be coaxially arranged with respect to one another on a manner best seen in Figure 2.

Disposed between the piston bodies 42, 42' is a pair of intake valve discs 58 and 60 that are fabricated of a suitable spring steel material or the like and which are formed with central openings 62, 64, respectively, through which the piston rod end section 34 extends. The valve discs 58, 60 are adapted for engagement with the valve seats 54, 56 and 54', 56', respectively and disposed between the discs 58, 60 is a valve spring disc 66 which is also formed with a central opening 68 and comprises a plurality of circumferentially spaced radially extending undulations 70 (see Figure 3) which function to yieldably maintain the valve discs 58, 60, operatively engaged with the associated valve seats of the piston bodies 40, 42.

Disposed centrally of the valve discs 58, 60 and the spring discs 56 is a central positioning spacer or spider, generally designated by the numeral 72. The spider 72 is formed with a central opening 74 through which the piston rod end section 34 extends, and the spider 72 includes a plurality (preferably three) of circumferentially spaced radially outwardly extending anns 76, the radially outermost portions of which terminate adjacent the inner periphery of the members 58, 60 and 66, whereby to limit movement of these members in a radial plane. If desired, an optional piston ring, representatively designated by the numeral 78, may be arranged radially outwardly from the valve discs 58, 60 and spring discs 66 and adapted for sealing engagement with the inner periphery of the cylinder 12 in a manner well known in the art.

Disposed adjacent the upper side of the piston body 42 is a compression valve assembly 80 which comprises a pair of spring steel or the like valve discs 82 and 84 which are formed with central openings 86, 88, respectively, through which the piston rod end section 34 extends. Interposed between the underside of the valve disc 84 and the valve seat 50 is an orifice disc 90 that is formed with a central opening 92 and with a plurality of radially inwardly extending notches 94 around the outer periphery thereof. As illustrated, the outer diameter of the valve discs 82, 84 and the orifice disc 90 are approximately equal and are all slightly larger in diameter and therefore project slightly radially outwardly beyond the valve seat 50, with the notches 94 being generally axially aligned with the valve seat 50, whereby to permit limited fluid flow (bleed) between the disc 90 and the valve seat 50.

Arranged directly axially above the valve disc 82 is a spacer ring 96 which is formed with a central opening 90 through which the piston rod end section 34 extends and arranged directly above the spacer ring 96 is a support washer 100 which is formed with a central opening 102 and is positioned directly against the underside of the shoulder 36, as illustrated.

As will hereinafter be described in detail, the compression valve assembly 80 functions to control the flow of fluid passing upwardly through the plurality of ports 46 of the piston body 42 as the piston assembly 14 moves downwardly (during a compression stroke) within the fluid chamber 28.

A rebound valve assembly 104, which is similar in construction to the aforementioned compression valve assembly 80, is disposed adjacent the underside of the piston body 42'.

The assembly 104 comprises a pair of spring steel or the like valve discs 106 and 108 that are formed with central openings 110 and 112, respectively, through which the piston rod end section 34 projects. Disposed interjacent the upper side of the valve disc 108 and the valve seat 50' is an orifice disc 114 which is also formed with a central opening 116 and a plurality of radially inwardly extending, circumferentially spaced notches 118. A spacer ring 120 having a central opening 122 is located directly axially below the valve disc 106 and a support washer 124 having a central opening 126 is located between the spacer ring 120 and the nut 40 which is threaded on the end portion 38 of the piston rod 16 in a manner so as to maintain the support washers 124, 100, spacer rings 120, 96, valve discs 106, 108, 82, 84, orifice discs 114, 90, piston bodies 42, 42' and spider 72 in a state of compression between the nut 40 and the shoulder 36.

In operation of the shock absorber 10, during a compression stroke, i.e. downward movement of the piston assembly 14 within the cylinder 12, oil flows upwardly through the plurality of ports 44' in the piston body 42' and opens the valve disc 60, i.e. biases the valve disc 60 upwardly off from the valve seats 54', 56' against the resistance of the spring disc 66.

The oil then flows radially inwardly between the outwardly projecting arms 76 of the spider 72 and thereafter axially upwardly through the plurality of flow ports 46 of the piston body 42 Thereafter, the fluid flows radially outwardly between the upper side of the valve seat 50 and the notches 94 of the orifice disc 90 into the upper end of the fluid chamber 28. At such time as the pressure acting on the valve discs 82, 84 reaches a predetermined magnitude, the discs 82, 84 will be biased upwardly away from the valve seat 50 to permit it a greater magnitude of fluid flow, i.e. during high speed movement of the piston assembly 14.

During a rebound stroke, i.e. upward movement of the piston assembly 14 within the cylinder 12, fluid flows axially downwardly through the plurality of flow ports 44 of the piston 42 and biases the valve disc 58 away from the valve seats 54, 56, against the resistance of the spring disc 66. This fluid then flows axially and radially between the outwardly projecting arms 76 of the spider 72 and there after axially downwardly through the plurality of flow ports 46' of the piston body 42'. This fluid then flows between the valve seat 50' of the piston body 42' and the plurality of notches 118 of the orifice disc 114 into the lower end of the fluid chamber 28. At such time as the pressure acting against the valve discs 106,108 reaches a predetennined mag nitude, the discs 106,108 will move away from tile valve seat 50', i.e. during high speed piston movement, to permit a predetennined greater magnitude of fluid flow.

One particularly important feature resides in the fact that the orifice discs 90, 114, may be independently changed or modified so as to control the low speed operation of the shock absorber 10 and more particularly, so that the rebound and compression characteristics may be changed independently of one another.

Another feature resides in the fact that the valve discs 82, 84 and 106, 108 may be varied to control the operational or performance characteristics of the piston assembly 14. For example, the discs 82, 84 and 106, 108 may be changed by varying the material, thickness, diameter and/or the number thereof in order to achieve the desired performance. Additionally, the diameter and/or thickness of the spacer rings 96 and 120 may be varied so as to control the degree of blow-off of the valve discs 82, 84 and 106, 108. Yet another feature resides in the fact that the cross-sectional size and/or number of the flow ports 44, 46 and 44', 46' may be conveniently changed for varying the operational charactelistics ofthe piston assembly 14. For example, the flow ports 46' may be changed to control the high speed rebound characteristics of the assembly 14, while the flow ports 46 may be varied for controlling the high speed compression characteristics of the assembly 14. Yet another feature resides in the fact that a large number of the components of the assembly 14 are interchangeable and thus may be manufactured at significantly reduced tooling expenses. For example, the piston bodies 42 and 42' can be interchangeable, as can the compression and rebound discs an(l/o1 the intake valve discs 58. 60. A further feature resides in the fact that the valve discs incorporated therein are subjected to significantly less fatigue than analagous prior art designs, with the result that the operational life of the piston assembly 14 will be improved over such prior art designs. It is to be noted that while the piston assembly 14 has been shown in the attached drawings and described above as being incorporated in the pressurized-type shock absorber, the principles of the present invention are not intended to be so limited, since the present invention should find very satisfactory application in multiple or two-tube type shock absorbers.

WHAT WE CLAIM IS: 1. A shock absorber piston assembly comprising: first and second coaxially arranged piston members each having radially inwardly and outwardly sets of axially extending flow ports, a compression valve assembly disposed adjacent one side of one of said piston members, a rebound valve assembly disposed adjacent one side of the other of said piston members, each of said compression and rebound valve assemblies comprising at least one disc-like valve member movable toward and away from an associated valve seat, and an intake valve assembly disposed between said piston members for selectively controlling fluid flow between certain of said flow ports of one of said members and certain of said flow ports of the other of said members, said intake valve assembly comprising first and second disc-like intake valve members, one of said members being co-operable with a valve seat on one of said piston members and the other of said valve members being co-operable with a valve seat on the other of said piston members, and a common spring element interposed between and arranged coaxially of said first and second valve members for resiliently biasing the same toward engagement with the associated valve seats, said compression, rebound and intake valve assemblies comprising the entire valve means for controlling fluid flow within the shock absorber whereby to permit changing the rebound and compression characteristics of said shock absorber solely by changing an appropriate one or ones of said valve members.

2. A piston assembly as claimed in Claim 1 which includes a piston ring extending coaxially of the piston assembly and located radially outwardly from said first and second intake valve members.

3. A piston assembly as claimed in Claim 1 or 2, wherein one of the compression and rebound valve assemblies comprises at least one valve disc and an orifice disc interposed between such one valve disc and an associated valve seat on the adjacent piston member.

4. A piston assembly as claimed in Claim 3, wherein each of the compression and rebound valve assemblies comprises at least one valve disc and one orifice disc, the orifice disc being interposed between the associated valve disc and adjacent valve seat for controlling low speed fluid flow between the associated valve

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. the discs 82, 84 will be biased upwardly away from the valve seat 50 to permit it a greater magnitude of fluid flow, i.e. during high speed movement of the piston assembly 14. During a rebound stroke, i.e. upward movement of the piston assembly 14 within the cylinder 12, fluid flows axially downwardly through the plurality of flow ports 44 of the piston 42 and biases the valve disc 58 away from the valve seats 54, 56, against the resistance of the spring disc 66. This fluid then flows axially and radially between the outwardly projecting arms 76 of the spider 72 and there after axially downwardly through the plurality of flow ports 46' of the piston body 42'. This fluid then flows between the valve seat 50' of the piston body 42' and the plurality of notches 118 of the orifice disc 114 into the lower end of the fluid chamber 28. At such time as the pressure acting against the valve discs 106,108 reaches a predetennined mag nitude, the discs 106,108 will move away from tile valve seat 50', i.e. during high speed piston movement, to permit a predetennined greater magnitude of fluid flow. One particularly important feature resides in the fact that the orifice discs 90, 114, may be independently changed or modified so as to control the low speed operation of the shock absorber 10 and more particularly, so that the rebound and compression characteristics may be changed independently of one another. Another feature resides in the fact that the valve discs 82, 84 and 106, 108 may be varied to control the operational or performance characteristics of the piston assembly 14. For example, the discs 82, 84 and 106, 108 may be changed by varying the material, thickness, diameter and/or the number thereof in order to achieve the desired performance. Additionally, the diameter and/or thickness of the spacer rings 96 and 120 may be varied so as to control the degree of blow-off of the valve discs 82, 84 and 106, 108. Yet another feature resides in the fact that the cross-sectional size and/or number of the flow ports 44, 46 and 44', 46' may be conveniently changed for varying the operational charactelistics ofthe piston assembly 14. For example, the flow ports 46' may be changed to control the high speed rebound characteristics of the assembly 14, while the flow ports 46 may be varied for controlling the high speed compression characteristics of the assembly 14. Yet another feature resides in the fact that a large number of the components of the assembly 14 are interchangeable and thus may be manufactured at significantly reduced tooling expenses. For example, the piston bodies 42 and 42' can be interchangeable, as can the compression and rebound discs an(l/o1 the intake valve discs 58. 60. A further feature resides in the fact that the valve discs incorporated therein are subjected to significantly less fatigue than analagous prior art designs, with the result that the operational life of the piston assembly 14 will be improved over such prior art designs. It is to be noted that while the piston assembly 14 has been shown in the attached drawings and described above as being incorporated in the pressurized-type shock absorber, the principles of the present invention are not intended to be so limited, since the present invention should find very satisfactory application in multiple or two-tube type shock absorbers. WHAT WE CLAIM IS:

1. A shock absorber piston assembly comprising: first and second coaxially arranged piston members each having radially inwardly and outwardly sets of axially extending flow ports, a compression valve assembly disposed adjacent one side of one of said piston members, a rebound valve assembly disposed adjacent one side of the other of said piston members, each of said compression and rebound valve assemblies comprising at least one disc-like valve member movable toward and away from an associated valve seat, and an intake valve assembly disposed between said piston members for selectively controlling fluid flow between certain of said flow ports of one of said members and certain of said flow ports of the other of said members, said intake valve assembly comprising first and second disc-like intake valve members, one of said members being co-operable with a valve seat on one of said piston members and the other of said valve members being co-operable with a valve seat on the other of said piston members, and a common spring element interposed between and arranged coaxially of said first and second valve members for resiliently biasing the same toward engagement with the associated valve seats, said compression, rebound and intake valve assemblies comprising the entire valve means for controlling fluid flow within the shock absorber whereby to permit changing the rebound and compression characteristics of said shock absorber solely by changing an appropriate one or ones of said valve members.

seat and valve disc.

5. A piston assembly as claimed in any preceding claim, wherein each of the piston members has a first valve seat on one side thereof and a pair of valve seats on the opposite side thereof co-operable with said intake valve assembly.

6. A piston assembly as claimed in Claim 5 which includes locating means disposed centrally of said intake valve members and said associated spring means for coaxially orienting the intake valve members so that they are axially aligned with said pairs of valve seats of the first and second piston members.

7. A piston assembly as claimed in any preceding claim, wherein said first and second piston members are substantially identical in size and construction.

8. A shock absorber piston assembly constructed and arranged to operate substantially as herein described with reference to and as illustrated in the accompanying drawing.

9. A vehicular shock absorber including a piston assembly as claimed in any preceding claim.