Shock absorber with improved piston architecture

A shock absorber includes a cylinder and a piston dividing the cylinder in first and second cylinder chambers. The piston includes a first main channel and a first main non-return valve allowing a first main fluid flow from the second to the first chamber; and a second main channel and a second main non-return valve allowing a second main fluid flow from the first to the second chamber. The piston includes a connecting member; a first central member received into the connecting member such that the parts of the first main channel in the connecting member and the first central member are in line; and a second central member including another part of the second main channel and received into the connecting member such that the parts of the second main channel in the connecting member and the second central member are in line.

FIELD OF THE INVENTION

The invention relates to a shock absorber comprising a cylinder having a cylinder wall, and a piston sealing against the cylinder wall and dividing the cylinder in first and second cylinder chambers, the piston being movable within the cylinder along the cylinder wall in inward and outward directions upon inward and outward movement, respectively, of the piston inside the cylinder. A first side of the piston is associated with the first cylinder chamber and a second side of the piston is associated with the second cylinder chamber, being associated meaning that the first side points in the direction of the first cylinder chamber and that the second side points in the direction of the second cylinder chamber. The piston comprises a first main channel and a first main non-return valve associated with the first main channel such that the first main channel and first main non-return valve allow a first main fluid flow from the second side to the first side of the piston; and a second main channel and a second main non-return valve associated with the second main channel such that the second main channel and second main non-return valve allow a second main fluid flow from the first side to the second side of the piston.

BACKGROUND OF THE INVENTION

Dampers, or shock absorbers, are well known and widely applied in, for instance, a variety of vehicles like cars, truck, buses and trains. The dampers are designed to provide a desired damping behavior between parts moving with respect to one another. Damping can be chosen to be stiff or soft by the specific design of the damper. More complex dampers have been proposed, which are, for instance, stiff dampers but soft at the start of a motion to be damped or provide a frequency selective damping behavior. Each such damper will have its own damper architecture dedicated to the functioning of the damper. Each architecture requires its own specific parts. Any required changes in the damping requirements may require a redesign of the damper and amendments of quite a few if not all parts of the damper. Each damper design and damper characteristics will requires their own dedicated parts.

The damper characteristics are generally implemented in the design of the piston. The various requirements will yield complex piston designs with a considerable building height. The larger building height of the piston will result in a reduced working stroke of the damper at a same height of the damper or to a longer damper at a same working stroke. Preferably one would like to have a piston with a small building height to have to longest possible working stroke at a given height of the damper. Present piston designs of complex dampers generally require longer damper heights or provide a shorter working stroke.

Currently, various different design concepts are required to obtain dampers or pistons with a linear damping behavior, blow-off type dampers or pistons, dampers or pistons requiring only rebound forces, etcetera, whereas it would be very advantageous to have a piston architecture concept that allows incorporating various, including even the most difficult damping characteristics, which is not feasible at all with known piston architectures.

EP 2 108 858 A2 discloses a shock absorber with a piston having a two-member housing. A first member of the housing is intended to move along a cylinder wall of the cylinder of the shock absorber with a seal in between. The first housing member is hollow with an open bottom end that is closed by a second member, or cover.

US 2015/0152936 A1 discloses a shock absorber with a piston having a piston body consisting of three members that are mounted on top of each other. The top and bottom members are mounted against opposing ends of an intermediate member.

SUMMARY OF THE INVENTION

It is an objective of the invention to provide a damper (shock absorber) having a simple design architecture.

It is another or alternative objective of the invention to provide a damper having a design architecture using standard parts that can be used in other designs as well.

It is yet another or alternative objective of the invention to provide a damper having a flexible design architecture allowing implementation of complex damping characteristics.

It is yet another or alternative objective of the invention to provide a damper having a design architecture providing a short building height.

At least one of the above objectives is achieved by a shock absorber comprising a cylinder having a cylinder wall, and a piston sealing against the cylinder wall and dividing the cylinder in first and second cylinder chambers, the piston being movable within the cylinder along the cylinder wall and along a longitudinal direction of the piston and the cylinder in inward and outward directions upon inward and outward movement, respectively, of the piston inside the cylinder, a first side of the piston being associated with the first cylinder chamber and a second side of the piston being associated with the second cylinder chamber, the piston comprisinga first main channel and a first main non-return valve associated with the first main channel such that the first main channel and first main non-return valve allow and damp a first main fluid flow from the second side to the first side of the piston;a second main channel and a second main non-return valve associated with the second main channel such that the second main channel and second main non-return valve allow and damp a second main fluid flow from the first side to the second side of the piston;a ring-shaped connecting member comprising a part of the first main channel and a part of the second main channel;a first central member comprising another part of the first main channel and received into the connecting member at a first side of the connecting member, which is transverse to the longitudinal direction of the piston and associated with the first side of the piston such that the parts of the first main channel in the connecting member and the first central member are in line; anda second central member comprising another part of the second main channel and received into the connecting member at a second side of the connecting member, which is transverse to the longitudinal direction of the piston and associated with the second side of the piston such that the parts of the second main channel in the connecting member and the second central member are in line.
A side of the piston being associated with one of the cylinder chambers is intended to mean that said side of the piston is in contact with said cylinder chamber. A valve being associated with a channel is intended to mean that said valve will influence a fluid flow in said channel. A side of one member being associated with a side of another member is intended to mean that said side of said one member and said side of said other member are corresponding sides substantially directed in a same direction, for instance, both being top sides that are directed upwards or both being bottom sides that are directed downwards. The connecting member, and first and second central members are to be understood as being separate items.

The piston design architecture with the connecting and first and second central members is very flexible in implementing various damping characteristics, even complex damping characteristics, at a very short building height of the piston. Various parts of the design can be used in different designs having different damping characteristics

In an embodiment the connecting member is configured for movement along and sealing against the cylinder wall.

In an embodiment the first main non-return valve is provided on the first central member.

In an embodiment the second main non-return valve is provided on the second central member.

In an embodiment the part of the first main channel in the connecting member has two ends, one end being in line with the part of the first main channel in the first central member and the other end being in direct fluid connection with the second side of the piston. A direct fluid connection is intended to be understood as a fluid connection in which fluid can freely flow without obstruction by a valve.

In an embodiment the part of the second main channel in the connecting member has two ends, one end being in line with the part of the second main channel in the second central member and the other end being in direct fluid connection with the first side of the piston.

In an embodiment of the shock absorbera first central member channel is provided on a side of the first central member, which is transverse to the longitudinal direction of the piston and associated with the second side of the piston, the first central member channel being in fluid communication with the second side of the piston,a second central member channel is provided in a side of the second central member, which is transverse to the longitudinal direction of the piston and associated with the first side of the piston, the second central member channel being in fluid communication with the first side of the piston, andan auxiliary valve is configured and arranged between the first and second central member channels to influence a fluid flow between the first and second sides of the piston.

The auxiliary valve provides an additional damping characteristic to the shock absorber. An additional soft damping characteristic can be provided at the onset of a damping stroke to provide a more comfortable damping character. The additional damping may also be made frequency-dependent. The shock absorber and especially the piston architecture allows to integrate such additional damping behaviour.

The central member channels allow for an auxiliary flow to provide additional damping characteristics to the damper.

In an embodiment the auxiliary valve is configured and arranged such that the auxiliary valve provides for an open connection for the auxiliary fluid flow through the first and second central member channels in a rest position of the auxiliary valve and gradually closes off the auxiliary fluid flow at increasing pressure difference across the auxiliary valve at either inward or outward movement.

In an embodiment the first central member channel comprises a first central member groove provided at the side of the first central member, which is transverse to the longitudinal direction of the piston and associated with the second side of the piston.

In an embodiment the second central member channel comprises a second central member groove provided at the side of the second central member, which is transverse to the longitudinal direction of the piston and associated with the first side of the piston.

In an embodiment the first central member groove comprises an annular groove, the second central member groove comprises an annular groove, and the auxiliary valve comprises a stack of at least one annular plate valve.

In an embodiment the first central member channel is in direct fluid connection with the part of the first main channel in the first central member, optionally a first auxiliary channel being provided in the first central member, which extends from the first central member channel to a side of the first central member opposing the side comprising the first central member channel, to provide for a direct fluid connection between the first central member channel and the part of the first main channel in the first central member.

In an embodiment the second central member channel is in direct fluid connection with the part of the second main channel in the second central member, optionally a second auxiliary channel being provided in the second central member, which extends from the second central member channel to a side of the second central member opposing the side comprising the second central member channel, to provide for a direct fluid connection between the second central member channel and the part of the second main channel in the second central member.

In an embodiment the auxiliary valve comprisesa controlled flow channel arranged to provide a fluid connection between a first auxiliary valve side and a second auxiliary valve side, the controlled flow channel comprising the first and second central member channels;a controlled valve assembly provided in the controlled flow channel to allow, in operation, influencing a controlled fluid flow in the controlled flow channel in a controlled flow direction from the first auxiliary valve side to the second auxiliary valve side;a movable valve body being movable with respect to a wall of the controlled flow channel and acting on the controlled valve assembly so as to allow changing a flow resistance for the controlled fluid flow by the controlled valve assembly; anda variable volume chamber, the movable valve body interacting with the variable volume chamber such that movement of the movable valve body and a change in volume of the variable volume chamber are interrelated, wherein the variable volume chamber comprises an outlet opening, in operation, downstream of the controlled valve assembly and does not comprise an opening upstream of the controlled valve assembly with respect to the controlled fluid flow in the controlled flow channel, the outlet opening providing a flow resistance, and a fluid pressure upstream of the controlled valve assembly with respect to the controlled fluid flow acting on the movable valve body to induce a force on the movable valve member in a direction to increase a fluid pressure in the variable volume chamber and to decrease a volume of the variable volume chamber by fluid flow from the variable volume chamber through the outlet opening, which allows an interrelated movement of the movable valve body.

In an embodiment the controlled valve assembly is configured such that at least one of an effective opening and a closing force of the controlled valve assembly is changed upon movement of the movable valve body to change the flow resistance for the controlled fluid flow by the controlled valve assembly.

In an embodiment the controlled valve assembly is configured such that the flow resistance for the controlled fluid flow by the controlled valve assembly increases with decreasing volume of the variable volume chamber.

In an embodiment the controlled valve assembly is configured to have spring-like behaviour and to exert a force on the movable valve body in a direction to move the movable valve body back to a neutral position when the movable valve body has moved from the neutral position.

In an embodiment the controlled valve assembly comprises a controlled valve plate, optionally a ring-shaped controlled valve plate.

In an embodiment the controlled valve plate comprises opposing edges, optionally opposing internal and external perimeters of a ring-shaped controlled valve plate, one or both opposing edges being restricted in movement with respect to one or both of a wall of the controlled flow channel and the movable valve body, optionally one or both opposing edges being clamped by one or both of a wall of the controlled flow channel and the movable valve body.

In an embodiment the controlled valve assembly comprises a controlled valve plate interacting with at least one curved surface upon movement of the movable valve body with decreasing volume of the variable volume chamber to gradually decrease an effective surface area of the controlled valve plate in the controlled flow channel.

In an embodiment the controlled valve plate comprises at least one opening.

In an embodiment the controlled valve plate comprises at least one opening positioned and configured to gradually close against the at least one curved surface upon movement of the movable valve body with decreasing volume of the variable volume chamber.

In an embodiment the movable valve body comprises a curved surface interacting with the controlled valve plate.

In an embodiment the movable valve body comprises first and second movable valve body members, and the controlled valve plate is clamped between the first and second movable valve body members, optionally at least one of the first and second movable valve members comprising a curved surface interacting with the controlled valve plate.

In an embodiment the wall of the controlled flow channel comprises a curved surface interacting with the first valve plate.

In an embodiment the controlled valve assembly comprises a controlled valve plate closing against a valve seat and of which a closing force against the valve seat is changed upon movement of the movable valve body, optionally the valve seat being provided on the movable valve body and the controlled valve plate being fixed with respect to the wall of the controlled flow channel.

In an embodiment the controlled valve assembly is bidirectional acting for first and second flows in opposite directions in the controlled flow channel, and comprises first and second controlled valve plates associated with the first and second flows, respectively, each of the first and second controlled valve plates closing against a respective valve seat and of which a closing force against the respective valve seat changes upon movement of the movable valve body, optionally the respective valve seats being provided on the movable valve body and the first and second controlled valve plates being fixed with respect to the wall of the controlled flow channel.

In an embodiment the controlled valve assembly comprises a third controlled valve plate configured to have spring-like behaviour and to exert a force on the movable valve body in a direction to move the movable valve body back to a neutral position when the movable valve body has moved from the neutral position, optionally the third controlled valve plate being arranged in between the first and second controlled valve plates

In an embodiment the variable volume chamber comprises a non-return valve associated with an opening of the variable volume chamber downstream of the controlled valve assembly, the non-return valve being closed upon the controlled fluid flow and opening for a fluid flow in a direction opposite to the controlled fluid flow.

In an embodiment the connecting member comprises one of a slot and projection at its internal perimeter, and at least one of the first and second central members comprises the other one of the projection and the slot at its external perimeter, the slot and projection being configured to cooperate to align the connecting member and the at least one of the first and second central members with respect to one another.

In an embodiment the connecting member and at least one of the first and second central members are fitted, optionally press-fitted, into one another such as to provide a sealing fit.

In an embodiment the piston comprises more than one first main channel, the connecting member comprising a part of each first main channel in line with another part of each first main channel comprised in the first central member.

In an embodiment the piston comprises more than one second main channel, the connecting member comprising a part of each second main channel in line with another part of each second main channel comprised in the second central member.

In an embodiment the parts of the first and second main channels in the connecting member are provided alternately in the connecting member.

In yet another aspect the invention provides a piston for use in a shock absorber according to any one of the preceding claims, the piston comprisinga first main channel and a first main non-return valve associated with the first main channel such that the first main channel and first main non-return valve allow and damp a first main fluid flow from the second side to the first side of the piston;a second main channel and a second main non-return valve associated with the second main channel such that the second main channel and second main non-return valve allow and damp a second main fluid flow from the first side to the second side of the piston;a ring-shaped connecting member comprising a part of the first main channel and a part of the second main channel;a first central member comprising another part of the first main channel and received in the connecting member at a first side of the connecting member, which is transverse to the longitudinal direction of the piston and associated with the first side of the piston such that the parts of the first main channel in the connecting member and the first central member are in line; anda second central member comprising another part of the second main channel and received in the connecting member at a second side of the connecting member, which is transverse to the longitudinal direction of the piston and associated with the second side of the piston such that the parts of the second main channel in the connecting member and the second central member are in line.

DETAILED DESCRIPTION OF EMBODIMENTS

FIG. 1schematically shows a shock absorber or damper10according to the invention. The damper comprises a cylinder12and a piston11that can move within the cylinder in inward and outward directions with respect to the cylinder. The direction of movement of the inward and outward strokes of the piston are indicated by the arrows labeled Mi and Mo, respectively. The piston seals against the cylindrical wall12.1of the cylinder and divides the cylinder in a first or upper cylinder chamber10.1and a second or lower cylinder chamber10.2. A piston rod13attached to the piston11is in a sealing fashion guided through a top wall of the cylinder12. The damper can be attached by its piston and cylinder attachment arrangements14,15to, for instance, parts of a car to damp relative movements. Damping is achieved by influencing a fluid flow in between first and second cylinder chambers by an arrangement in the piston11.

The piston according to a first embodiment is shown in more detail and in cross-section inFIG. 2. A top or first side11.1of the piston is directed towards and associated with the first cylinder chamber10.1, and a bottom or second side11.2of the piston is directed towards and associated with the second cylinder chamber10.2.

A first main channel301,101passes through the piston11to allow for a first main fluid flow F10from the second side11.2to the first side11.1of the piston and therefore from the second cylinder chamber10.2to the first cylinder chamber10.1. A first main non-return valve111is arranged at the piston first side11.1and is associated with the first main channel301,101so as to open for fluid flow from the second cylinder chamber10.2through the first main channel towards the first cylinder chamber10.1and piston first side11.1. The first main non-return valve111is closed for fluid flow in the opposite direction, although may allow for a small constant fluid flow in either direction by providing a relatively small constant opening. The first main fluid flow F10flows through the first main channel301,101upon inward movement Mi of the piston11within the cylinder12. The first main fluid flow and associated inward movement of the piston is damped by the first main channel and the first main non-return valve.

In the same manner a second main channel302,202passes through the piston11to allow for a second main fluid flow F20from the piston first side11.1and first cylinder chamber10.1to the piston second side11.2and second cylinder chamber10.2. A second main non-return valve212is arranged at the piston second side11.2and is associated with the second main channel302,202so as to open for fluid flow from the first cylinder chamber10.1through the second main channel towards the second cylinder chamber10.2and piston second side11.2. The second main non-return valve is closed for fluid flow in the opposite direction, but may also allow for a relatively small constant fluid flow in either direction by providing a constant opening. The second main fluid flow F20flows through the second main channel302,202upon outward movement Mo of the piston11within the cylinder12. The second main fluid flow and associated outward movement of the piston is damped by the second main channel and the second main non-return valve.

The piston body comprises first and second central members100,200and a ring-shaped connecting member300. The first (or top) central member100is received into the connecting member300at a top or first side of the connecting member, which is associated with the piston first side11.1. The second (or bottom) central member200is received into the connecting member at a bottom or second side of the connecting member, which is associated with the piston second side11.2. The first and second central members100,200and the connecting member300are shown in more detail inFIGS. 3, 4 and 5, respectively. The connecting member300seals against the cylinder wall12.1and is shaped to move along the cylinder wall. Both central members100,200leave a clearance between them and the cylinder wall.

The ring-shaped connecting member300comprises parts301,302of both the first main channel and the second main channel, respectively. First main channel part301is in fluid connection with first main channel part101of the top (first) central member100to form the first main channel in between first and second sides11.1,11.2of the piston. The part301of the first main channel in the connecting member has opposing ends. One end is in line with the part101of the first main channel in the top central member100and the other end is in fluid connection with the piston second side11.2. Second main channel part302is in fluid connection with second main channel part202of the bottom (second) central member200to form the second main channel in between first and second sides11.1,11.2of the piston. The part302of the second main channel in the connecting member300also has opposing ends. One end is in line with the part202of the second main channel in the bottom central member200and the other end is in fluid connection with the piston first side11.1. The clearances between the central members and the cylinder wall allow fluid to flow into the first and second main channel. The respective clearances may also be regarded as a part of the first and second main channels.

Actually, the piston comprises more than one first main channel301,101and more than one second main channel302,202in the embodiment shown. This shows especially inFIGS. 3, 4 and 5. The ring-shaped connecting member300comprises parts301for each first main channel and parts302for each second main channel. Each part301of each first main channel is in line with another part101of each first main channel comprised in the first central member100. Correspondingly, each part302of each second main channel is in line with another part202of each second main channel comprised in the second central member200.FIG. 4shows that the parts301and302are arranged alternately in the connecting member300. The connecting member, and the first and second central members are fitted, especially press-fitted into one another so as to provide a sealing fit.

The first main non-return valve111is provided on the top central member100and closes off the first main channel301,101. Likewise, the second main non-return valve212is provided on the bottom central member and closes of the second main channel302,202. As indicated above, one or both of the main non-return valves111,212may provide for a constant opening to allow for a constant fluid flow across the respective valve in either direction. Such constant opening may, for instance, be provided in the valve or in the valve seat. One or both of the main non-return valves comprise one or more plates in the embodiment shown.

FIGS. 6, 7, 8aand8bshows a second embodiment of a piston11of a shock absorber10according to the invention. The second piston embodiment is largely identical to the first embodiment ofFIGS. 2-5, and additionally comprises central member channels105,205in the first and second central members100,200, respectively, and an auxiliary valve400provided in between the first and second central member channels105,205.

The first central member channel105is provided in the bottom side of the first central member100inFIGS. 6 and 7. The bottom side of the first central member is associated with the second side11.2of the piston, meaning that both the bottom side of the first central member and the second side11.2of the piston are at corresponding sides. The second piston side11.2is also the bottom side of the piston inFIG. 6. The first central member channel105is in fluid communication with first main channel part101in the first central member100and is visible on the right-hand side inFIGS. 6 and 7. Therefore, the first central member channel105is via the first main channel in fluid communication with the second side11.2of the piston and thus with the second cylinder chamber10.2, which is visible at the right-hand side ofFIG. 6as well. The first central member channel is shaped as a groove, especially an annular groove, arranged at the side of the first central member associated with the second side11.2of the piston.

Correspondingly, the second central member channel205is provided in the top side of the second central member200inFIGS. 6, 8aand8b. The top side of the second central member is associated with the first side11.1of the piston, meaning that both the top side of the second central member and the first side11.1of the piston are at a corresponding sides. The first piston side11.1is also the top side of the piston inFIG. 6. The second central member channel205is in fluid communication with the second main channel part202in the second central member200and is visible on the left-hand side inFIGS. 6, 8aand8b. Therefore, the second central member channel205is via the second main channel in fluid communication with the first side11.1of the piston and thus with the first cylinder chamber10.1, which is also visible at the left-hand side inFIG. 6. The second central member channel is also shaped as a groove, especially an annular groove, arranged at the side of the second central member associated with the first side11.1of the piston.

FIGS. 9, 10 and 11show a variant of the second embodiment. The variant ofFIGS. 9, 10 and 11is largely identical to the second embodiment inFIGS. 6, 7, 8aand8b. However, the first central member channel in the form of annular first central member groove105is in a different manner in fluid connection with the second piston side11.2. The first central member groove105is via first auxiliary channel106in fluid connection with first main valve chamber101.1between first central member100and main non-return valve111. First main valve chamber101.1is in fluid connection with the second piston side11.2via first main channel101,301so that first central member channel105is in fluid connection with the second piston side11.2. In a corresponding fashion second central member channel in the form of annular second central member groove205is via second auxiliary channel206in fluid connection with second main valve chamber202.1between second central member200and the second main non-return valve212. The second main valve chamber202.1is via second main channel202,302in fluid connection with the first piston side11.1.

An auxiliary valve400in the form of an annular plate valve is provided in between the first and second central members100,200in the second embodiment and its variant, such that fluid may flow past auxiliary valve400in a neutral or rest position thereof. The auxiliary valve400in this embodiment functions provides the shock absorber with a more comfortable damping behaviour and may also be referred to as a comfort valve400. The neutral position of the comfort valve is shown inFIGS. 6 and 9. The annular plate valve400is clamped at its internal perimeter between first and second central members100,200. The external perimeter of auxiliary annular plate valve400is left free to move between the first and second central members. The auxiliary annular plate valve400is further provided with openings401to allow passage of fluid from first annular central member groove105to second annular central member groove205, or vice versa.FIGS. 12aand 12bshow top views on two embodiments of an annular plate valve400. The embodiment ofFIG. 12ahas multiple round openings401, while the embodiment ofFIG. 12bhas elongated openings. Various other embodiments may be conceived as well. One may vary in various parameters such as number, shape and locations of the openings401and thickness, shape and material of the plate valve400. The auxiliary valve may also comprise more than one plate valve.

Upon pressure build-up across auxiliary valve400upon fluid flow in either direction past the auxiliary/comfort valve, the auxiliary valve will move in the direction of the fluid flow and gradually deform against either the first or second central member100,200. Both the first and second central members100,200have a rounded edge110,210against which the auxiliary annular plate valve400deforms such as to gradually close off the openings401in the auxiliary valve.FIGS. 13a, 13b, 14aand 14bshow a detail of the annular plate valve400clamped in between first and second central members100,200. A neutral or rest position of the plate valve400is shown inFIGS. 13aand 14a, in which further a fluid flow F11is depicted as an example fluid flow.FIGS. 13band 14bshow the plate valve400in a deformed state closing off the openings401against rounded edge210. TheFIGS. 14aand 14bvariant shows an additional stepped surface of the first and second central members100,200at the position where the plate valve is clamped. The stepped surfaces allow for some additional fluid volume around the openings401and provide another parameter that can be varied to tune the damping characteristics. The auxiliary/comfort valve at its external perimeter will also close against either the first or second central member to close of fluid flow past the external perimeter. The auxiliary valve thus gradually closes of fluid flow upon pressure build up across the auxiliary valve400.

Upon inward movement Mi of the piston11inside the cylinder12a first main fluid flow F10will pass through first main channel301,101from the second cylinder chamber10.2. A first auxiliary fluid flow F11branches of from the first main fluid flow F10to the first auxiliary annular groove105and flows past the auxiliary valve400into the second auxiliary annular groove205through second main channel202,302towards the first cylinder chamber10.1with reference toFIG. 6. With reference toFIG. 9, the first auxiliary fluid flow F11branches of from the first main fluid flow F10within the first main valve chamber101.1and passes through first auxiliary channel106into first central member groove105towards and past the auxiliary valve400into second central member groove205and subsequently into second auxiliary channel206, second main valve chamber202.1and second main channel202,302into first cylinder chamber10.1. The first auxiliary fluid flow F11is only present when the auxiliary valve is still close to its neutral position at the initial phase of the inward movement Mi. A pressure difference will build up across the auxiliary valve400such that it gradually closes off the first auxiliary fluid flow F11, which will cause a further pressure build up inside first main valve chamber101.1. At sufficient pressure difference across first main non-return valve111, the first main non-return valve opens to allow first main fluid flow F10into the first cylinder chamber10.1.

Correspondingly, upon outward movement Mo of the piston11within the cylinder12a second main fluid flow F20will pass through the second main channel302,202from the first cylinder chamber. A second auxiliary fluid flow F21branches of from the second main fluid flow F20to the second auxiliary annular groove205and flows past the auxiliary/comfort valve400into the first auxiliary annular groove105through first main channel101,301towards the second cylinder chamber10.2with reference toFIG. 6. With reference toFIG. 9, the second auxiliary fluid flow F21branches of from the second main fluid flow F20within the second main valve chamber202.1and passes through second auxiliary channel206into second central member groove205towards and past the auxiliary valve400into first central member groove105and subsequently into first auxiliary channel106, first main valve chamber101.1and first main channel101,301into second cylinder chamber10.2. The second auxiliary fluid flow F21is also only present when the auxiliary valve400is still close to its neutral position at the initial phase of the outward movement Mo. A pressure difference will build up across the auxiliary valve400such that it gradually closes off the second auxiliary fluid flow F21, which will cause a further pressure build up inside second main valve chamber202.1. At sufficient pressure difference across second main non-return valve212, the second main non-return valve opens to allow second main fluid flow F20into the second cylinder chamber10.2.

The gradual closing off of fluid flows F11, F21by auxiliary/comfort valve400upon inward or outward piston movement Mi, Mo before opening of first or second main non-return valve111,212, respectively, provides comfort to persons travelling in a vehicle in which the damper having such piston is employed.

FIG. 8bshows a view on the top side of second central member200. A projection250at the circumference of the second central member is configured to cooperate with a slot350.1at the bottom side of the connecting member300, as visible inFIG. 4. The slot350.1is actually a part of first main channel part301in the connecting member. Correspondingly, the first central member100may also have projections shaped for cooperation with mating slots in the connecting member300, such as slots350.1that are part of the second main channel part302. Multiple projections may be arranged around the circumference of first and/or second central members100,200for cooperation with corresponding slots in the connecting member300. The cooperating projections and slots on first and/or second central members and the connecting member can also be employed on the first embodiment ofFIGS. 2, 3, 4 and 5, and any other embodiment. In other embodiment the projection can be provided on the connecting member and the slot on the first and/or second central member.

The piston according to an embodiment with an auxiliary valve embodied as a frequency-selective damper valve is shown in detail and in cross-section inFIG. 15. Further details are shown inFIGS. 16 to 18. A top or first side11.1of the piston is directed towards and associated with the first cylinder chamber10.1, and a bottom or second side11.2of the piston is directed towards and associated with the second cylinder chamber10.2.

A bi-directional frequency-selective damper valve is provided between the first and second central members100,200and centrally in the connecting member300. The frequency-selective damper valve comprises a controlled valve assembly500, a movable valve body600and two variable volume chambers701,702, and acts in a controlled valve channel in between the first and second cylinder chambers10.1,10.2. The controlled valve channel comprises first and second central member annular grooves105,205in sides of the first and second central members100,200associated with the second and first sides11.2,11.1of the piston, respectively. The annular groove105in the first central member100is in fluid connection with the first main channel301,101end therefore with the second cylinder chamber10.2. The annular groove205of the second central member200is in fluid communication with the second main channel302,202and therefore with the first cylinder chamber10.1.

The controlled valve assembly500is provided in the controlled flow channel and comprises a controlled valve plate550clamped in between first and second movable valve body members610,620of the movable valve body600. The controlled valve plate550is ring shaped, and also the first and second movable valve body members610,620are ring-shaped. A sleeve650keeps the first and second movable valve body members610,620and the controlled valve plate550clamped together. The ring-shaped controlled valve plate550has a central opening and is at its inner circumference clamped between the first and second movable valve body members610,620. The inner circumference of controlled valve plate550can move up and down together with the movable valve body600. The first and second movable valve body members comprise curved edges611,621facing towards the controlled valve plate550, the curved edges each having a curved surface. The outer circumference of the connecting controlled valve plate550is provided in between protrusion members510,520on the wall of the controlled flow channel. The protrusion members have curved surfaces511,521facing towards the controlled valve plate550. They are clamped between the first/upper and second/lower central members100,200and fitted within the connecting member so as to form a wall part of the controlled flow channel. The protrusion members510,520have a ring-shaped configuration. In the embodiment ofFIGS. 15 and 16the curved surfaces511,512are provided on protrusions of the protrusion members, the protrusion projecting into the controlled flow channel. In alternative embodiments the curved surfaces can be provided in another manner.

The movable valve body600of first and second movable valve body members610,620and sleeve650is movable up and down in an annular space provided between first and second central members100,200, connecting member300and intermediate member350. Intermediate member350is clamped in between first and second central members100,200together with non-return valve plates712,722(that are clamped in between first central member100and intermediate member350, and intermediate member and second central member200, respectively). An upper variable volume chamber710is defined between first central member100, intermediate member350and movable valve body600, especially first movable valve body member610. An outlet opening711of the upper variable volume chamber710is defined by a clearance between first movable valve member610and first central member100. The outlet opening711has an annular slit shape that provides for a flow restriction for a fluid flow F31from the variable volume chamber710through the outlet opening711to the controlled flow channel. A variable volume chamber non-return valve712with opening713is provided at the top of the upper variable volume chamber. The non-return valve712allows for a fluid flow F11from the space101.1between the first main non-return valve111and the first central member100into the upper variable volume chamber710, but prevents a fluid flow from the upper variable volume chamber into that space101.1.

Correspondingly, a lower variable volume chamber720is defined between second central member200, intermediate member350and movable valve body600, especially second movable valve body member620. An outlet opening721of the lower variable volume chamber720is defined by a clearance between second movable valve member620and second central member200. The outlet opening721has an annular slit shape that provides for a flow restriction for a fluid flow F32from the variable volume chamber720through the outlet opening721to the controlled flow channel. A variable volume chamber non-return valve722with opening723is provided at the bottom of the lower variable volume chamber. The non-return valve722allows for a fluid flow F21from the space202.1between the second main non-return valve212and the second central member200into the lower variable volume chamber720, but prevents a fluid flow from the lower variable volume chamber into that space202.1.

The controlled valve plate550is at its inner circumference clamped in between the first and second movable valve body members610,612having the curved surfaces611,621facing towards the controlled valve plate550. At its outer circumference the controlled valve plate is provided, but not clamped, in between the protrusions of the protrusion members510,520, which have curved surfaces511,521facing the controlled valve plate. The controlled valve plate has a large central opening505.1, as shown inFIG. 18, to fit around the intermediate member650and allow clamping in between first and second movable valve body members. A detail showing the controlled valve plate clamped between the first and second movable valve members is shown inFIG. 17. The controlled valve plate further has openings506.1provided near its inner circumference, cut-out openings506.2at its inner circumference, and openings506.3near its outer circumference. The openings506.1and506.2cooperate with the curved surfaces611,621of the movable valve body. Upon deformation of the controlled valve plate550when the movable valve body600moves up or down the openings506.1and506.2will be gradually closed off by the curved surfaces621and611, respectively. The openings506.3cooperate with the curved surfaces511,521of the protrusion members510,520. Upon deformation of the controlled valve plate550when the movable valve body600moves up or down the openings506.3will be gradually closed off by the curved surfaces511and521, respectively. The gradual closing off of the openings506.1,506.2,506.3upon deformation of the controlled valve plate gradually shuts of a fluid flow F15, F25past the controlled valve plate550.

Upon outward movement Mo the piston11moves upwards within the cylinder12and fluid flows F20, F21and F25enter from the first/upper cylinder chamber10.1into the second main channel302,202. The main fluid flow F20passes to the second/lower cylinder chamber10.2when the second main non-return valve212opens. A fill flow F21passes from the space in between second central member200and second main non-return valve into channels220. The fill flow F21will open the non-return valve722so that fill flow F21passes through opening723in the non-return valve712into lower variable volume chamber720to fill the lower variable volume chamber with fluid. Non-return valve712is configured such that opening713is normally closed, so closed in the absence of any fluid pressure on non-return valve712. A controlled fluid flow F25flows from first cylinder chamber10.1and second main channel302,202into a space205aat the first cylinder chamber side (second main channel side) of the controlled flow channel with respect to the controlled valve plate550. The controlled fluid flow F25may pass through the openings in the controlled valve plate towards the first cylinder chamber10.1. The fluid pressures in lower variable volume chamber720, in second main channel302,202, in the space205aand in first cylinder chamber10.1are (about) equal. This fluid pressure acts in lower variable volume chamber720on a surface area A2of the second movable valve body member620. In space205athis fluid pressure acts on a surface area A2-Ax of the second movable valve body member620. The surface area Ax varies with movement of the movable valve member600and is dependent on the contact area of controlled valve plate550with second movable valve body member620, especially with the curved surface621thereof. As the movable valve body moves upwards from the neutral middle position this surface area Ax becomes larger. The fluid pressure in lower variable volume chamber720therefore effectively acts on surface area Ax of the movable valve body600and the resulting force increases as the movable valve body moves upwards since the surface area Ax increases, which is a functional force transfer increase on the movable valve body with movement from the neutral position.

At the same time the controlled valve plate550rolls over curved surface511of protrusion member510and curved surface621of the second movable valve body member620with movement away of the movable valve body600from the neutral position, which decreases a functional surface area of the controlled valve plate550for force transfer but at the same time increases its stiffness. Both characteristics can be tuned together with other parameters, such as increase of functional force on the movable valve body600, to achieve a desired time and therefore frequency dependent behaviour of the damping valve. The controlled valve plate further acts like a spring exerting a force onto the movable valve body600to move it back to its neutral position.

Space105aof the controlled flow channel at the other side of the controlled valve plate550is in fluid connection with the first main channel101,301and second cylinder chamber10.2and at (about) equal fluid pressure. Since the piston moves upwards the fluid pressure in second cylinder chamber10.2is considerably lower than the fluid pressure in first cylinder chamber10.1. The fluid pressure in space105ais thus considerably lower than the fluid pressure in space205awith outward piston movement Mo.

At the start of the outward piston movement Mo the upper variable volume chamber710is filled with fluid. The fluid pressure (damping pressure) in the upper variable volume chamber acts on a surface area A1of the first movable valve body member610of the movable valve body600. Generally, the surface area A1will be equal to the surface area A2when the movable valve body600is symmetrical with respect to the controlled valve plate550, as is the case in the embodiment shown inFIGS. 15 and 16. The resulting force by the fluid pressure in upper variable volume chamber710is directed downwards and counteracts the upward force on the movable valve body by the fluid pressure in the lower variable volume chamber720. A fluid flow F31can escape from the upper variable volume chamber through the outlet opening711of the upper variable volume chamber. The outlet opening711is formed by a slit in between first/upper movable valve body member610and first/upper central member100. The slit also presents a flow restriction to the fluid flow F31from the upper variable volume chamber710. Fluid can only escape from the upper variable volume chamber through outlet opening711that is in fluid connection with the controlled flow channel downstream of the controlled valve assembly with controlled valve plate550with respect to the controlled fluid flow F25from upper/first cylinder chamber10.1to lower/second cylinder chamber10.2. The non-return valve712with its opening713is closed for fluid flow from the upper variable volume chamber. The fluid pressure within upper variable volume chamber acts to close the non-return valve712. The fluid pressure within upper variable volume chamber710and the fluid flow F31act to damp the upward movement of the movable valve member600. Fluid flow F31can therefore be referred to as a damping fluid flow.

The controlled fluid flow F25is in parallel to the flow path of the second main fluid flow F20upon outward movement Mo. The speed and therefore the time required for closure of the openings of the controlled valve plate550and therefore of the controlled valve assembly500determine the frequency-dependency of the damper valve. The frequency-selective gradual closing of the controlled valve assembly provides a frequency-selective damping of the controlled fluid flow and therefore of the piston movement with respect to the cylinder. One may like to have a proportional relationship between pressure increase in the upper variable volume chamber710and displacement of the movable valve body600. The fluid pressure increase in the upper variable volume chamber is non-linear. This can be largely compensated by the change in effective surface area Ax on which the fluid pressure upstream of the controlled valve assembly500(in the lower variable volume chamber720) acts. The curvatures and radiuses of the curved surfaces511,621can be designed for obtaining a proportional relationship. One may further design the number, position, shape and size of the openings in the controlled valve plate550for that purpose. A number of variables is therefore available to obtain a desired damping behaviour. The openings506.1,506.2and506.3shown inFIG. 18are only one example. The openings506.1allow for a fluid flow F25.1that will be reduced as opening506.1will be gradually closed off upon displacement of the movable valve body. Cut-out openings506.2cooperate with annular chambers in the first and second movable valve body members610,620as shown inFIG. 17allow for a fluid flow F25.2at a high frequent pressure increase.

The frequency-selective damper valve shown inFIGS. 15, 16, 17 and 18acts bi-directional, so also at inward movement Mi of the piston11. At inward movement a first main fluid flow F10passes from the second cylinder chamber10.2to the first cylinder chamber through the first main channel when the first main non-return valve111opens. A fill fluid flow F11will fill the upper variable volume chamber by passing opening713in non-return valve712and a controlled fluid flow F15passes through the controlled flow channel from the second cylinder chamber to the first cylinder chamber when the controlled valve assembly500is not (yet) closed. A damping fluid flow F32passes from the lower variable volume chamber720to what now is the downstream side of the controlled valve assembly with respect to the controlled fluid flow F15.

FIG. 19shows another embodiment of a piston having a frequency-selective damper valve. The frequency selective damper valve of theFIG. 19embodiment only acts in one direction, being the outward direction Mo. The various elements, parts and flows are largely identical as has been described with reference to theFIGS. 15, 16, 17 and 18for the outward movement of the bi-directional frequency-selective damper. However, the one-directional embodiment ofFIG. 19does not have a lower variable volume chamber. Instead a space750is provided below the movable valve body600, which space750is in open fluid connection with the second main channel302,202, the space202.1between second central member200and second main non-return valve212, and first/upper cylinder chamber10.1via passage751. The passage751is provided in between second main channel part202and space750and between annular groove205and space750in the embodiment shown. The clearance between second/lower movable valve body member620is such that it does not present a flow restriction to fluid flow between channel751and space750. Upon inward movement the fill flow F11acts to reset upper/first variable volume chamber710to allow frequency-selective damping at a next outward movement of the piston.

Yet another embodiment is shown inFIG. 20.FIG. 20also depicts a bidirectional frequency-selective valve inside piston1. Parts and elements having the same reference signs as parts and elements disclosed with reference toFIGS. 15-19have the same function as already disclosed. The controlled valve assembly shown inFIG. 20comprises second and third valve plates560,570acting on the one hand as non-return valve closing on valve seats612,622of first and second movable valve body members610,620, respectively. The first and second controlled valve plates560,570have inner slits561,571at their inner circumference and outer slits562,572at their outer circumference, respectively. The inner slits561,571allow a fluid flow to pass the valve plates when lifted from their respective valve seat and further allow centering the valve plates on the movable valve body600. At their outer circumference the first and second controlled valve plates560,570rest against curved surfaces531,531, respectively, of protrusion member530that is part of the wall of the controlled flow channel302,202,205,205a,105a,105,101,301. Upon outward movement Mo of the piston controlled fluid flow F25can pass the controlled valve assembly in two sub flows F25.7, F25.8. Sub flow F25.7passes through slits572of third valve plate570and subsequently through slits562of second valve plate560. The slits572are gradually closed off against curved surface532of protrusion member530as movable valve body600moves upwards. Second valve plate560then moves away from curved surface531so that slits562remain open to allow passing of any sub flow of controlled fluid flow F25. Another sub flow F25.8may lift the third valve plate570from its valve seat622and pass the third vale plate across valve seat622and through outer valve plate slits571. Subsequently, sub flow F25.8passes through outer slits562of the second/upper valve plate560into space105aand annular groove105and further towards lower/second cylinder chamber10.2. The pretension on third valve plate increases as movable valve body600moves upwards, as has been described earlier with reference toFIGS. 15-18. The characteristics of the damping behaviour of the valve plates is determined by the thickness and material of the valve plates, the curvature of the curved surfaces531,532, a pretension on the valve plates in the neutral position, etc. A desired behaviour can be obtained by careful design of the controlled valve assembly500. Upon inward movement Mi of the piston the fluid flows and function of the second and third valve plates is inverted. The effective surfaces of the movable valve body600on which the fluid flow upstream of the controlled valve assembly acts are static in theFIG. 20embodiment, meaning that they remain constant with movement of the movable valve body.

FIG. 21shows yet another embodiment of a frequency-selective damping valve in a piston11. The embodiment ofFIG. 21combines the embodiments ofFIGS. 15 and 20, providing an increased number of design parameters to tune the frequency-selective damping behaviour of the valve. The embodiment comprises first and second controlled valve plates560,570embodied as non-return valves and a third controlled valve plate550. The third controlled valve plate550comprises openings and cooperates with curved surfaces as described earlier. The internal and external perimeters of the ring-shaped controlled valve plate550are restricted in their movement by the movable valve body600and the wall of the controlled flow channel, respectively. The internal perimeter is clamped between first and second members610,620of the movable valve body. The third controlled valve plate comprises a chosen stiffness and acts like a spring exerting a force onto the movable valve body600to move it back to its neutral position.

The first and second movable valve body members610,620in this embodiment additionally comprise reset slits615,625extending from the corresponding variable volume chambers710,720towards the controlled valve assembly500. The reset slits615,625do not extend over the full available height of the members610,620so as to still provide a flow resistance for fluid flow from the corresponding variable volume chambers710,720, respectively. The reset slits allow a fast movement back towards the neutral position of the controlled valve assembly when the piston reverses its movement from inwards to outwards or vice versa. Fluid can easily escape from a variable volume chamber through the reset slits after having been filled by a respective fill flow F11, F21.

The embodiment ofFIG. 21further comprises various stepped and curved surfaces cooperating with the three valve plates550,560,570and their openings to achieve a desired frequency-dependent damping behaviour. The controlled flow channel comprises channel parts106,206connecting to the spaces101.1,202.1in between first/upper central member100and first main non-return valve111, and second/lower central member200and second main non-return valve212, respectively, which spaces are in fluid connection with the first main channel301,101and second main channel302,202, respectively.

A very important parameter to maintain a desired frequency-dependency is the preload generated on the first and second controlled valves560,570. The functional surface areas of these valves in relation to the pressure upstream of the controlled valve assembly results in a displacement of the first and second controlled valves560,570at their circumference associated with the respective valve seats612,622. The fluid pressure upstream of the controlled valve assembly results in a displacement of the movable valve body600and its valve seats612,622, which is further governed by the stiffness of a respective controlled valve plate560,570and the damping pressure in a variable volume chamber. The displacement of the movable valve body in an equilibrium position is predominantly given by the fluid pressure upstream of the controlled valve assembly and the stiffness of the respective controlled valve plate, which displacement should be equal or even larger than the displacement of the respective controlled valve plate to result in closure of that valve plate on its associated valve seat. In such equilibrium position there should be a positive preload on the respective controlled valve plate560,570in the order of, for instance, 0 to 50 N. At a next pressure pulse upstream of the controlled valve assembly the respective controlled valve plate560,570will open from its valve seat. A corresponding displacement of the movable valve body is damped by a damping pressure in the respective variable volume chamber and will therefore lag behind a displacement of the controlled valve plate, during which fluid passes the controlled valve assembly through the controlled valve channel. In an next equilibrium position the respective controlled valve plate560,570will close again on its associated valve seat612,622. The embodiment ofFIG. 21has element providing a degressive behaviour to the damping valve and elements providing progressive behaviour to the damping valve. By careful tuning of the various parameters available in the design one can obtain a desired damping behaviour of the damping valve.

The bidirectional frequency-selective valve in the embodiments shown is configured symmetric for the inward and outward directions, but may generally also be configured asymmetrically. The valve plates of the controlled valve assembly may further be clamped or not, as would be desirable in a specific configuration to reach a required damping behaviour.