WO2008073023A1

WO2008073023A1 - Valve/valves to be used in a shock absorber and a shock absorber including such a valve

Info

Publication number: WO2008073023A1
Application number: PCT/SE2007/050822
Authority: WO
Inventors: Atsushi Ishii; Johan Söderdahl
Original assignee: öHLINS RACING AB
Priority date: 2006-11-09
Filing date: 2007-11-07
Publication date: 2008-06-19
Also published as: SE0602378L; SE531812C2

Abstract

The invention relates to a valve (7a, 7b) intended to adjust a hydraulic flow in a shock absorber (1), or to a shock absorber including such a valve (7a, 7b). The valve (7a, 7b) includes a valve core (11) having ports (lie, lid) extending through the core (11). The ports (lie, lid) are delimited by first and second leaf valves (16, 17) disposed on each side of the valve core (11). The first leaf valves (16) disposed on one side (lla) of the valve core are flexible and are elastically deformed when exposed to a certain damping force. The second leaf valve (17) is rigid, disposed on the other side (lib) of the valve core, and has a centred hollow (20a) having an inner diameter (20b) and guide surfaces in the form of radially protruding projections (21a) having an outer diameter (21b). The rigid second leaf valve (17) is intended to slide in a cylindrical volume (13a) against a substantially smooth surface on or in the valve housing (12). Between the projections, cavities (21c) having a specific area are created, through which damping medium can flow such that, when the rigid second leaf valve (17) lifts from the valve core (11), it lets through damping medium both through the centred hollow (20a) and through the cavities (21c). In the shock absorber (1) according to the invention, two valves (7a, 7b) realized according to the invention are placed in a first valve chamber (10) in a valve housing (12). The first valve chamber (10) communicates hydraulically, via ports (9a, 9b, 9c), with one or both of the damping chambers (3a, 3b) disposed in the shock absorber (1) and delimited by a main piston (2).

Description

Valve/valves to be used in a shock absorber and a shock absorber including such a valve

Technical field The invention relates to a valve for regulating the damping medium flow between the first and second chamber of a shock absorber, in which the flow is adjustably regulated in one direction and totally prevented in the other.

Background to the invention

It has proved to be a problem to produce a simple, easily adjustable and functionally optimal valve for adjusting a one-way flow, i.e. a non-return valve, of damping medium between the damping chambers of a shock absorber. Included in the prior art, for example, is US 5441133. In this patent, a shock absorber is described which has a valve disposed in the main piston separating the two chambers of the absorber. The valve comprises a main valve, which damps the damping medium flow between the damping chambers at high speeds, and a valve which already opens at low speeds. The main valve has the form of a leaf valve with cut-out projections, which floats in a volume inside the piston, in which the outer circumference of the leaf valve heads towards an inner surface in the piston. A valve retainer and a spring hold the main valve in the closed position as long as a small force is acting upon the valve area. The leaf valve in the main valve is intended to increase the area acted upon by the damping medium and is not intended for use as a non-return valve, since the cutouts allow damping medium to flow from both directions over the piston. Moreover, the valve is difficult to adjust owing to its placement inside the main piston. By virtue of the Applicant's own products, a valve is known in which a non-return valve in the form of a circular leaf valve operates. The leaf valve operates in and slides against a part which is disposed on a piston and the inner surface of which comprises _ p _

milled grooves. The grooves are intended to centre the valve in the cup without bringing too much weight to the construction. At the same time, the grooves are used to limit the stroke of the leaf valve. This solution involves, however, an extra machining step for the cup, which therefore entails a high production cost. Another problem with this solution is that the valve opens and closes with a time delay, owing to the limited flow area.

Summary of the invention

The device according to the invention is a valve intended to adjust a hydraulic flow between the damping chambers of a shock absorber, and a shock absorber including such a valve.

The valve contains a valve core, through which damping medium flows. The damping medium flow in the principal direction of the valve, that is to say the flow from the high-pressure to the low-pressure chamber of the shock absorber, is determined by a plurality of thin, flexible first leaf valves disposed directly adjacent to one of the sides of the piston. The leaf valves are elastically deformed at a certain flow and thereby let through a certain quantity of damping medium.

The damping medium flow over the valve core counter- directional to the main flow is controlled by a rigid plate in the form of a second leaf valve, which is pressed against the valve core by a spring and which, in its closed position, totally prevents the damping flow through the core. The term rigid should be taken to mean that the second leaf valve does not yield in any direction when it is exposed to the normal pressure and temperature conditions prevailing in the shock absorber. The whole of the second leaf valve therefore lifts from the surface of the valve core when a force greater than the counterbracing spring force acts upon the valve. The second rigid leaf valve has a centred hollow having an inner diameter and guide surfaces in the form of radially protruding projections disposed on the outer diameter. When the second leaf valve is open, damping medium flows both through the centred hollow and through the open area formed between the projections. When the valve is closed, the second leaf valve covers the ports extending through the valve core.

Since even a small displacement of the second leaf valve in the radial direction can lead to unwanted leakage, the projections are also intended to centre the second leaf valve in the cup without the part creating too much friction. The fact that the damping medium also flows through the open area between the projections means that the total flow area over the valve increases, which helps to create a situation in which the valve does not need to open as high for the same flow volume. A smaller opening also means a faster closing, with the result that a device using this plate as a non-return valve has a faster response time than previously known valves.

The cavities also create a reduced contact area against the valve core and, with a reduced contact area, the back pressure which can arise when the core valve is opened is also minimized.

The valve core is fixed in the valve housing between a cup and a valve body. The coupling between valve core and valve body can either be inflexible or adjustable. The cup has a cylindrical, smooth inner surface, against which the second leaf valve slides.

In one embodiment of the valve, the possible stroke length of the second rigid leaf valve is limited. The characteristics and working of the valve can be altered and optimized by limiting this stroke length, i.e. the distance between valve core and leaf valve. The limitation can either be arranged by integrating within the cup a part in the form of a cylindrical unit separated from or integrated in the cup, or by one or more of the projections being bent down prior to assembly, so that the outer end of the projection, at maximum valve stroke, rests on the bottom of the cup.

The invention also relates to a shock absorber in which two valves of the above configuration are fitted. The shock absorber comprises a damping cylinder filled with damping medium, in which a main piston fixed to a piston rod is arranged to move axially. The main piston divides the inner volume of the damping cylinder into a first and a second damping chamber. At one end of the damping cylinder there is disposed a cylinder head, which comprises a valve housing having a first valve chamber pressurized by a pressurizing member. In this pressurized valve chamber, the two valves are disposed. The damping medium is arranged to flow mainly from the damping chamber having the highest pressure, via the valve communicating with the damping chamber having the highest pressure, out into the pressurized common first valve chamber, and then into the chamber having the lowest pressure via the second rigid leaf valve of the second valve. A shock absorber of this configuration, having the valves according to the invention as flow adjusters, acquires a consistent damping character which is easy to adapt to external conditions, as well as a fast response upon the transitions from a return stroke to a compression stroke.

In one embodiment of the shock absorber, the main piston is solid and the valves also contain an extra port, limited by a leak-flow-limiting valve. Since the main piston is solid, all the damping medium passes through the two valves, which increases the possibility of finely adjusting the damping character of the shock absorber simply by adjusting the characteristics of the valves .

The invention is described in greater detail below with references to accompanying drawings.

List of figures

Fig. 1 shows a perspective view of a shock absorber including two sets of the valve according to the invention.

Fig. 2 shows a section through the upper part of the shock absorber and one of the valves.

Fig. 3 shows a sectional view through the valve housing and one of the valves. Fig. 4 shows a detailed view of the leaf valve according to the invention and its fitting to the valve core and cup,

Fig. 5 shows a second embodiment of the invention.

Fig. 6 shows a third embodiment of the invention. Fig. 7 shows a different view of the third embodiment.

Detailed description of the invention

Figures 1 and 2 show a shock absorber device 1 of previously known type, in which a main piston 2 operates in a damping cylinder 3 and divides the interior of the cylinder into a first 3a and a second 3b damping chamber. Extending from the first end of the damping cylinder is a piston rod 4, to which the main piston 2 is fixed, and at the other end of the damping cylinder 3 there is disposed a cylinder head 5. Communicating with the cylinder head 5 is a container 6, which pressurizes the absorber and absorbs the volume changes of the damping medium, caused, inter alia, by temperature changes. Figure 1 also shows a valve housing 12 integrated with the cylinder head 5, in which a first 7a and a second 7b valve are disposed in the valve housing 12. In Figure 2 is shown a section through the cylinder head 5 and the first valve 7a. In the container 6 there is disposed a solid container piston 8, which delimits a pressurizing medium 6a, preferably in the form of a gas, from the damping medium filling the damping chambers 3a, 3b and the upper part 6b of the container 6. The pressurizing medium 6a acts upon the container piston 8, compresses the damping medium and thereby creates a system pressure in the absorber. The damping medium present in the upper part 6b of the container 6 communicates via a port 9 with an inner first valve chamber 10 common to the valves 7a, 7b. This common first valve chamber 10 can be seen more clearly in Figure 3.

In Figure 3, the first valve 7a is shown in cross section. The first valve 7a and the second valve 7b are constructed in the same way, so that reference is here made to only one of the valves. The valve 7a contains a valve core 11, through which damping medium flows. The valve core 11 is fixed in the valve housing 12 between a cup 13 and a valve body 14. A plurality of thin first leaf valves 16 are arranged directly adjacent to the first side 11a of the valve core and on the other side lib of the valve core there is disposed, in a second valve chamber 13a, a rigid second leaf valve 17. The rigid second leaf valve 17 is pressed by a spring 18 against the second side lib of the valve core lib. In the valve body 14 there is also introduced a conical leak-flow-determining valve 19 disposed in a port 22, the position of which within the valve body 14 is adjustable from the absorber via an adjusting knob 15.

Fig. 4 shows the second leaf valve 17, which comprises a centred hollow 20a having a diameter 20b and guide surfaces in the form of radially protruding projections 21a disposed on the outer diameter 21b. The projections 21a are intended to slide in the second valve chamber 13a against the inner, smooth cylindrical surface 13b of the cup 13 in order to centre the second leaf valve 17 in the interior of the cup 13. Between the projections 21a there is therefore created a cavity 21c, which cavities have a flow area. The flow area corresponds to an area extending between the projections 21a over a section of between 0.5 and 2 mm, preferably 1 mm, inside the outer diameter 21b. This section is dependent on the configuration, flow area and placement of the ports lie, Hd in the valve core 11, with due regard to the need for the cavities 21c never to be allowed to overlap the ports Hc, Hd. In this embodiment, six projections are provided, so that a sufficiently large centring slide surface is generated, at the same time as the oil flow over the valve is maximized. Of course, the number of projections and the configuration of the projections can be adapted to prevailing damping conditions and the size of the absorber and can be anything from three to 12 in number. Preferably, the second rigid leaf valve 17 is produced with its projections 21a from a metal plate by means of punching, etching or some similar production method.

In a second and third embodiment, shown in Figures 5, 6 and 7, the stroke length xl x2 for the second leaf valve 17 is limited by the fact that a substantially radially extending surface 23 is provided in the cup 13 or a corresponding part which encloses the second valve chamber 13a. The radially extending surface 23 on which the second leaf valve 17 rests at maximum stroke, i.e. in the fully opened state, is arranged such that a certain distance xl x2 is created between the lower face of the core 11 and the radially extending surface

17a of the second leaf valve 17. The distance xl x2 determines the stroke length of the valve and is a parameter which can be adapted to optimize the working of the valve. In Figure 5, the maximum stroke length is determined by the introduction of an additional part 24 into the inner volume 13a in the cup 13. The surface 23 can also be provided directly in the cup 13, for example they can be produced from one piece.

In Figures 6 and 7, a third embodiment is shown, in which the stroke length of the valve is limited by one or more of the projections 21a, 21a' disposed in the leaf valve 17. These stroke-length-limiting projections 21a' are arranged such that they are bent down essentially on the lines 25, so that an approximate right angle is created between the projections 21a' and the radially extending surface 17a of the second leaf valve 17. The outer end of the bent-down projections 21a' acts therefore as the stroke-length-limiting, radially extending surface 23 and, at maximum stroke, the surface rests on a horizontal surface 24 in the second valve chamber 13a. By varying the length of the bent-down part 21a' of the projections 21a or the placement of the bending line 25, it is possible to adjust the stroke length of the leaf valve in the second valve chamber 13a. The length y of the folded down part 21a' of the projections 21a therefore limits the stroke, i.e. the distance between the lower surface of the valve core 11 and the radially extending surface 17a of the second leaf valve 17, to a section x2. The bending line 25 is placed preferably a certain distance inside the outer diameter 21b of the sliding projections 21a to prevent the bent-down projection part 21a' from impairing the sliding characteristics between the second leaf valve 17 and the inner surface 13b of the cup 13. In Figure 6, the second leaf valve is shown with six lengthy projections intended to be bent down, but the length can thus be varied and be both longer and shorter than the sliding projections and the number of projections can range between one and twelve . When the absorber device 1 is in operation, the main piston 2 moves within the damping body 3 and thereby creates a pressure difference in the damping chambers 3a, 3b.

The damping chambers 3a, 3b are interconnected via the first valve chamber 10 common to the valves 7a, 7b. The pressure differences create a damping medium flow which is conducted from one damping chamber to the other via the ports 9b, 9c, the valves 7a, 7b and the common first valve chamber 10. The return flow is illustrated in Figure 2 by a solid line and flows therefore from the return chamber 3b of the shock absorber via the port 9b, through the first valve 7a, into the inner first valve chamber 10 and out into the compression chamber 3a via the second valve 7b and the port 9c. In the event of compression movements, the damping medium flows in the opposite direction.

The principal flow direction of damping medium through the valves is from the chamber currently acting as the high-pressure chamber to the low-pressure chamber. In Figure 3, solid arrows are used to illustrate a main flow, in this case the return flow, which is conducted from one damping chamber into the common first valve chamber 10 through the ports lie in the first valve 7a and out into the second damping chamber via the ports Hd in the second valve 7b. The main flow in the opposite direction is illustrated with dashed arrows. The ports Hc are delimited against the common first valve chamber 10 with a stack of the thin first leaf valves 16. The first leaf valves 16 are flexible and are elastically deformed in the event of a certain flow and thereby let a certain quantity of damping medium through the valve core 11. The valve body 14 fixes the first leaf valves 16 against the valve core 11.

In the event of small and slow absorber motions, the valve stack comprising the thin first leaf valves 16 does not get to be opened. Damping medium flows in this case through the ports 22 delimited by the leak-flow- determining valve 19. Owing to the conical shape of the valve 19, different positions of the valve in relation to the valve body 14 produce different magnitudes of the leak flow.

The flow through the ports lie in the common first valve chamber 10 creates a pressure increase in the volume. The increased pressure also in the ports Hd, in isolation or in combination with the pressure reduction in the low-pressure chamber, causes an opening force, counter-directional to the force created by the spring 18, to act upon the rigid second leaf valve 17. The second leaf valve 17 is opened at a pressure which produces a force greater than the spring force and a flow can then pass through the valve. When the second leaf valve 17 is opened, it lifts parallel with the lower surface Hb of the piston. The spring force of the spring 18 is chosen such that the second leaf valve 17 ensures that the pressure in the low- pressure chamber maintains at least the system pressure with which the absorber is pressurized. The spring force is therefore adapted to the system pressure, and the second leaf valve 17 opens if the force which the system pressure creates upon the valve exceeds the spring force. When the valve opens, the configuration of the second leaf valve 17 allows damping medium to flow over the valve both in the centred hollow 20a and in the space 21c formed between the projections 21a.

The second rigid leaf valve 17 is also intended to prevent damping medium from flowing in the opposite flow direction in the ports Hc, i.e. the second leaf valve 17 operates as a non-return valve. The valve is therefore closed when the pressure in the pressurized first valve chamber 10 is less than the pressure prevailing in the damping chambers, or when the pressure in the first valve chamber 10 produces a force - li on the leaf valve which is less than the spring force acting upon the non-return valve.

The invention is not limited to the embodiment shown by way of example above, but can be modified within the scope of the following patent claims and the inventive concept. For example, the invention can also be used to adjust the damping medium flow between the damping chambers in a front fork or similar devices. The valve according to the invention can also be used separately or in pairs.

Claims

Patent claims

1. Valve (7a, 7b) intended to adjust a hydraulic flow between the damping chambers (3a, 3b) of a shock absorber (1), in which the valve (7a, 7b) includes a valve core (11) having continuous first and second ports (lie, lid) which are delimited by first (16) and second (17) leaf valves disposed on either side (Ha, lib) of the valve core (11) , and in which the first leaf valves (16) disposed on one side (Ha) of the valve core are flexible and are elastically deformed when exposed to a certain damping force, and in which the second leaf valve (17) is pressed against the second side (lib) of the valve core by a spring (18), characterized in that the second leaf valve (17) is rigid and has a centred hollow (20a) having an inner diameter (20b) and guide surfaces in the form of radially protruding projections (21a) having an outer diameter (21b) , which are intended to slide in a cylindrical second valve chamber (13a) against a substantially smooth surface (13b) on or in the valve housing (12), in which between the projections cavities (21c) having a specific area are created, through which damping medium flows when the second leaf valve (17) is open.

2. Valve according to Claim 1, characterized in that when the second leaf valve (17) opens and lifts from the valve core (11), it lets through damping medium both through the centred hollow (20a) and through the cavities (21c) .

3. Valve according to Claim 1 or 2, characterized in that when the second leaf valve (17) is in the closed position, i.e. when the second leaf valve (17) is pressed against the valve core (11), the flow in the second port (Hd) delimited by the second leaf valve (17) is totally prevented, with the result that the second leaf valve (17) operates as a non-return valve.

4. Valve according to any one of the above claims, characterized in that the configuration of the cavities (21c) is determined by the placement of the ports (lie, lid) in the valve core (11), so that the cavities (21c) never coincide with the ports (lie, lid) .

5. Valve according to any one of the above claims, characterized in that the stroke length of the second leaf valve (17) is limited by the fact that a substantially radially extending surface (23), on which the second leaf valve (17) is arranged to rest at a predetermined maximum stroke, is placed in the second valve chamber (13a) such that the radially extending surface (17a) of the second leaf valve (17) maintains a certain distance (xl, x2) from the lower surface of the valve core (11) once the maximum stroke is reached.

6. Valve according to Claim 5, characterized in that the stroke length is limited by the fact that a cylindrical part (23) is introduced into the cylindrical volume (13a).

7. Valve according to Claim 6, characterized in that the stroke length of the valve is limited by the fact that one or more of the radially protruding projections (21a) are arranged bent down by a certain angle in relation to the radially extending surface

(17a) of the second leaf valve (17), so that the outer end of the bent-down part (2Ia') of the projections

(21a) acts as the stroke-length-limiting, radially extending surface (23) .

8. Valve according to Claim 7, characterized in that the downward bending essentially takes place on bending lines (24) disposed a certain distance inside the outer diameter (21b) of the radially protruding projections (21a), and in that an approximate right angle is created between the bent-down projection part (2Ia' ) and the radially extending surface of the second leaf valve (17) .

9. Valve according to Claim 8, characterized in that the stroke length of the second leaf valve (17) in the volume (13a) can be varied by adjusting the length of the bent-down projection part (2Ia') or the placement of the bending line (25) .

10. Valve according to any one of the above claims, characterized in that the second leaf valve (17) is arranged to slide in a cup-shaped part (13) resting between an inner surface in the valve housing (12) and the valve core (11) .

11. Shock absorber (1) comprising a damping cylinder (3) filled with damping medium, in which a main piston (2) fixed to a piston rod (4) is arranged to move axially, at the same time as it divides the inner volume of the damping cylinder (3) into a first (3a) and a second (3b) damping chamber, in which at one end of the damping cylinder (3) there is disposed a cylinder head (5) comprising a valve housing (12) having a first valve chamber (10) pressurized by a pressurizing member (6) and containing two adjustable first and second valves (7a, 7b) , characterized in that the first and the second valve (7a, 7b) are configured according to any one of Claims 1-10.

12. Shock absorber (1) according to Claim 11, characterized in that the damping medium is arranged to flow mainly from the damping chamber having the highest pressure (3a/3b), via the valve (7a, 7b) communicating with the damping chamber having the highest pressure (3a/3b) , out into the pressurized common first valve chamber (10), and then into the chamber having the lowest pressure (3a/3b) via the second rigid leaf valve (17) of the second valve (7a/7b) .

13. Shock absorber (1) according to any one of Claims 11-12, characterized in that the main piston (2) is solid, and in that the valves (7a, 7b) also contain an extra port (21), limited by a leak-flow-limiting valve (19) .