The invention relates to a device for admitting liquid into a liquid reservoir for a hydraulic shock absorber for a vehicle.

A shock absorber is applied in a vehicle in combination with a spring in order to damp the movement of the mass which presses on the spring when for instance the vehicle passes through a bend or brakes sharply.

A hydraulic shock absorber is known wherein a piston provided with valves is received for movement with a piston rod in an oil-filled cylinder. When the associated spring is compressed or extended, the piston rod is pressed in or pulled out, and oil is displaced via suitable valves from the one part of the cylinder separated by the piston to the other, and to or from an oil reservoir. The volume of the quantity of oil displaced to or from the reservoir corresponds to the volume of the part of the piston rod displaced into or out of the cylinder. The extent to which the piston of a known shock absorber is displaced depends on the external forces on the shock absorber. This has the consequence that when a vehicle takes a sharp bend or takes a bend at high speed, wherein a relatively great force is exerted on the shock absorbers of the outer wheels, it is pressed relatively far downward. The result hereof is that the vehicle tends to roll, which is undesirable. The same problem occurs when a vehicle performing a linear movement brakes sharply. In this case the shock absorbers of the front wheels are pressed in too quickly, as a result of which the vehicle pitches too strongly in forward direction.

In order to prevent the problem of pitch and roll in bends and during braking, measuring and control systems have been developed to measure the forces exerted on a vehicle when it negotiates a bend and during braking, the so-called G-forces, and to derive from these forces correction signals for actuator systems, using which the damping properties of a shock absorber can be modified to the measured G-forces. Such measuring and control systems generally comprise electronic components in combination with one or more electric motors, and thus result in an increase in the costs of purchasing and operating a vehicle.

It is an object of the invention to provide a device for admitting liquid into a liquid reservoir for a hydraulic shock absorber for a vehicle, using which it is possible to control the pressure of the liquid in the damper subject to occurring G-forces.

It is a further object to assemble this device solely from mechanical components, without making use of electronic circuits or electrical actuators.

These objectives are achieved, and other advantages gained, with a device of the type stated in the preamble, which is provided with control means for admitting liquid subject to G-forces exerted on the vehicle.

In an embodiment of a device according to the invention the control means comprise at least one first valve and at least one second valve which are provided in respectively a first conduit part and a second conduit part parallel thereto of a liquid conduit debouching in the liquid reservoir, wherein the first valve is accommodated in opened state and can be closed through the action of a G-force acting in a determined direction, and the second valve is accommodated in closed state counter to a pre-pressure, and wherein a first valve and a second valve are connected in each

case on their respective inlet sides and outlet sides by a conduit part.

In a shock absorber provided with a liquid reservoir in which two conduit parts debouch which are provided with such valves, as a result of a load on the shock absorber, liquid will, above a determined first pressure and in the absence of the active G-force, flow in through the first conduit part via the opened first valve. The load on the shock absorber can for instance be caused if the vehicle in question drives over an uneven part of a road surface in an otherwise linear direction of movement. If the vehicle drives through a bend a G-force becomes active, perceived by a passenger as centrifugal force. If the first conduit part is closable by the action of this G-force, as a result of a load on the shock absorber, liquid will, above a determined second, higher pressure, flow in through the second conduit part via the opened second valve. The second, higher liquid pressure is 'developed under said load until it has reached a value sufficient to overcome the pre-pressure under which the second valve is confined, wherein the valve is opened under the pressure of the liquid. Thus is achieved that through the action of a G-force in,a predetermined direction the liquid can escape from the shock absorber at a higher pressure than in the absence of this G-force, and the shock absorber imparts a suspension behaviour to the vehicle that is designated as "firm".

An embodiment of a device according to the invention, wherein a plurality of first valves are present in series in the first conduit part, each of which valves can be closed by the action of a differently oriented G-force, achieves that due to the action of each of these differently oriented G-forces the liquid can escape from the shock absorber at a higher pressure than in the absence of each of these G- forces. In this manner it is possible to provide a shock

absorber with which the resulting suspension behaviour of the vehicle is optionally "firm" when the vehicle travels through a bend (in which case the relevant first valve is closable through the action of a G-force directed transversely of the vehicle) , brakes sharply (in which case the relevant first valve is closable through the action of a G-force directed in longitudinal direction and counter to the direction of movement of the vehicle) , or drives over a speed bump (in which case the relevant first valve is closable by the action of a G-force directed vertically downward) .

In an embodiment the first valve comprises a closing valve displaceable under a pre-pressure in the direction of the active G-force and transversely of the first conduit part, which closing valve is displaceable between a first position, wherein the first conduit part is open in the absence of the G-force, and a second position wherein the first conduit part is closed by the action of the G-force. In a practical embodiment, the displaceable closing valve is formed by an at least two-part cylindrical body which is accommodated against a pressure spring in a cylindrical housing and a first part of which has a first diameter corresponding to the diameter of the housing, and a second part of which has a second diameter smaller than the first diameter.

In a simple embodiment the second valve is confined under a pre-pressure produced by a pressure spring.

In a device according to the invention the liquid reservoir comprises for instance a cylindrical container with a first chamber for containing a quantity of gas confined under a determined pressure and a second chamber separated therefrom by a movable separating piston for the purpose of receiving liquid. The invention further relates to a hydraulic shock absorber provided with a device as described above for

admitting liquid into the liquid reservoir of this shock absorber.

In a preferred embodiment of a hydraulic shock absorber according to the invention, the device for admitting liquid is accommodated in a housing integrated with the shock absorber.

The invention will be elucidated hereinbelow on the basis of exemplary embodiments and with reference to the drawings. In the drawings

Fig. 1 shows a highly simplified view of a diagram of a shock absorber provided with a liquid reservoir with a first embodiment of a liquid inlet control according to the invention in a first situation, Fig. 2 is a highly simplified view of a part of the control shown in fig. 1 in a second situation,

Fig. 3 shows a diagram of a vehicle with four wheels and the G-forces possibly acting on this vehicle, and Fig. 4a-4d show a highly simplified view of a diagram of a shock absorber provided with a liquid reservoir with a second embodiment of a liquid inlet control according to the invention, successively in a first, second, third and fourth situation. Corresponding components are designated in the figures with the same reference numerals.

Fig. 1 and fig. 2 show a hydraulic shock absorber 1 with an operating cylinder 2 which is filled with a liquid (in particular oil) and in which a piston 3 with piston rod 4 is movable, provided with fixing eyes 5, 6 for mounting of shock absorber 1 in a vehicle. Present in piston 3 are passage openings 7, 8 which are closed by respective valves 9, 10 which are confined against a pressure spring (not shown) . Piston 3 divides cylinder 2 into an upper 11 and a lower operating space 12, this latter being in open connection via a passage opening 13 with a conduit 14 which branches into a first conduit

part 15 and a second conduit part 16. The first 15 and the second conduit part 16 debouch respectively via a first valve 17 and a second valve 18 into the liquid space 23 of a liquid reservoir 19, which further also comprises a gas space 21, which is separated from liquid space 23 by a separating piston 22. In this embodiment the liquid space 23 also forms the conduit part connecting the outlet side of first valve 17 and second valve 18. For discharge of liquid in the case of overpressure in liquid space 23 relative to second conduit part 16, a non-return valve 38 is present which in practical cases is integrated into second valve 18. The first valve is a three-part cylindrical body 17 which is accommodated in a cylindrical housing for displacement counter to pressure spring 28 and a first part 25 of which has a diameter corresponding to the diameter of housing 24, a second central part 26 of which has a smaller diameter and a third part 27 of which again has a diameter corresponding to the diameter of housing 24. Cylindrical body 17 is displaceable in housing 24 between a rest position (shown in fig. 1) , wherein the central part 26 is situated just in second conduit part 15 as a result of which conduit 14 is in open connection with liquid space 23, and an operating position (shown in fig. 2) , wherein the part 25 of larger diameter is situated just in the second conduit part 15 which is thereby closed, as a result of which conduit 14 is in connection with liquid space 23 only via second conduit part 16 and second valve 18. Cylindrical body 17 is provided with an axial bore 32 to allow displacement of liquid in cylindrical housing 24 when body 17 is displaced.

Closing valve 17 and second valve 18 together form a control 20, the operation of which can be seen as follows.

If piston rod 4 of shock absorber 1 in a vehicle is pressed in by the action of a force F, represented by

arrow F in fig. 1, a part of the oil flows out of the lower operating space 12 via valve 9 to the first operating space 11, and another part flows via passage opening 13 into conduit 14. In the absence of G-forces having a component in the axial direction of cylindrical housing 24, closing valve 17 in the first conduit part 15 is opened, valve 18 in the second conduit part 16 is closed and the oil, represented by arrow 29, flows out of the lower operating space 12 via the first conduit part 15 into liquid space 23 of liquid reservoir 19.

If a G-force is present which does have a component in the axial direction of cylindrical housing 24, for instance if the relevant vehicle is travelling in a bend, closing valve 17 in the first conduit part 15 is closed by this G-force counter to the spring force produced by pressure spring 28, as a result of which the pressure on the oil increases due to the action of the force F on piston 3, as a result of which valve 18 in second conduit part 16 is opened counter to the force produced by the spring on this valve 18, and the oil, as represented by arrow 31, flows out of the lower operating space 12 via second conduit part 15 into liquid space 23 of liquid reservoir 19.

The damping characteristics of shock absorber 1 depending on occurring G-forces can thus be chosen subject to, among other factors, the orientation of cylindrical housing 24, the mass and the dimensions of closing valve 17 and valve 18, and the values of the spring constants of pressure spring 28 on closing valve 17 and the pressure spring (not shown) on valve 18.

Fig. 3 shows schematically a vehicle 40 with wheels 41-44 shown in the XY plane of a cartesian coordinate system 50, wherein the direction of forward movement, represented by arrow V, is in X direction. Indicated are the apparent forces (G-forces) which can be exerted with a change of speed at the position of the four wheels 41- 44. With sharp braking there occurs for instance an

apparent force G _x+ in forward direction, when a bend to the right is negotiated there occurs an apparent force G _γ _ in a direction to the left transversely of the vehicle, when a bend to the left is negotiated there occurs an apparent force G _γ+ in a direction to the right transversely of the vehicle, with strong acceleration there occurs an apparent force G _x _ in rearward direction, and during travel over a raised part in the road surface there occurs an apparent force G _z _ in downward direction. The figure indicates which of these forces is most strongly manifest at which wheel 41-44 in the form of pitch and roll of the vehicle when a change of speed occurs. During sharp braking the forward apparent force G _x+ is for instance most strongly manifest at front wheels 41, 42 of the vehicle in the form of pitching in forward direction, and when a bend to the right is negotiated the apparent force G _y+ to the left manifests itself most strongly at the left-hand wheels 42, 44 in the form of rolling of the vehicle. By making a suitable combination of valves which can each be closed in a control according to the invention under a determined G- force, a shock absorber can be assembled for each of the four wheels which provides a firm suspension behaviour specifically for each of these wheels. Fig. 4a shows a diagram for a control device 60 for a shock absorber for the right front wheel 41 of vehicle 40 of fig. 3, with closing valves 17, 17' and 17" for controlling the liquid flow subject to the occurrence of G-forces G _x+ , G _γ _ and G ₂ - in respectively forward direction, a direction laterally to the right and vertically downward direction. Closing valves 17, 17' and 17" are placed in a first branch 15, 15', 15" of liquid conduit 14, wherein valves 18, 18', 18" are placed in a parallel second branch 16, 16', 16". Closing valves 17, 17' and 17" and valves 18, 18', 18" are connected in each case on their respective inlet sides and outlet sides by a conduit part 15/16, 51, 51', 51".

The axial directions of housings 24, 24' 24" of the respective second valves 17, 17' and 17" in control device 60 are parallel to the direction of the relevant respective G-forces G _x+ , G _γ _ and G _z _. The figure shows the control 60 in a first situation, wherein vehicle 40 moves forward at uniform speed, i.e. in the absence of G-forces. If in this situation the piston rod 4 of shock absorber 1 in a vehicle is pressed in by the action of a force F, represented by arrow F, a part of the oil flows out of the lower operating space 12 via passage opening 13 into conduit 14 and flows, as indicated by arrows 29, via the first conduit part 15, 15', 15" into liquid space 23 of liquid reservoir 19.

Fig. 4b shows the diagram for the control device 60 as shown in fig. 4a in a second situation, wherein vehicle 40 brakes sharply, wherein an apparent force G _x+ occurs, due to the action of which the closing valve 17 in housing 24 is displaced and the first conduit part 15 is closed. If in this situation the piston rod 4 of shock absorber 1 in a vehicle is pressed in by the action of a force F, represented by arrow F, a part of the oil flows out of the lower operating space 12 via passage opening 13 into conduit 14 and, as indicated by arrows 29 and 31, flows via the second conduit part 16, the second valve 18 confined under spring pressure, the second conduit part 16', the connecting conduit 51, the first conduit parts 15', 15" and connecting conduit 51" into liquid space 23 of liquid reservoir 19.

Fig. 4c shows the diagram for the control device 60 as shown in fig. 4a in a third situation, wherein vehicle 40 takes a bend to the left, wherein an apparent force G _γ _ occurs, due to the action of which the closing valve 17' in housing 24' is displaced and the first conduit part 15' is closed. If in this situation the piston rod 4 of shock absorber 1 in a vehicle is pressed in by the action of a force F, represented by arrow F, a part of the oil flows out of the lower operating space

12 via passage opening 13 into conduit 14 and, as indicated by arrows 29 and 31, flows via the first conduit parts 15, 15', connecting conduit 51, the second valve 18' confined under spring pressure, connecting conduit 51', the first conduit part 15" and connecting conduit 51" into liquid space 23 of liquid reservoir 19. Fig. 4d shows the diagram for the control device 60 as shown in fig. 4a in a fourth situation, wherein vehicle 40 drives over an irregularity in the road surface, for instance a speed bump, wherein an apparent force G _z _ occurs, due to the action of which the closing valve 17" in housing 24" is displaced and the first conduit part 15" is closed. If in this situation the piston rod 4 of shock absorber 1 in a vehicle is pressed in by the action of a force F, represented by arrow F, a part of the oil flows out of the lower operating space 12 via passage opening 13 into conduit 14 and, as indicated by arrows 29 and 31, flows via the first conduit parts 15, 15', 15", connecting conduit 51', second conduit part 16", the third valve 18" confined under spring pressure, and connecting conduit 51" into liquid space 23 of liquid reservoir 19.

In a vehicle in which the wheel suspension of the right front wheel is provided with a shock absorber with a liquid control as according to the diagram of figures 4a-4d, forward pitching of the vehicle during sharp braking, rolling of the right-hand side when a bend is taken to the left and the forward pitching when driving over a speed bump are considerably damped. It will be apparent to the skilled person that a control for a shock absorber for the left front wheel and both rear wheels can be assembled in similar manner.