FR2617928A1 - Shock absorber including materials with shape memory - Google Patents

Abstract

Damper of the type including a piston provided with channels fitted with elements made from a material with shape memory which act on their flow rate, characterised in that the channels are each provided with a planar stopper 50 which can move rotationally at the surface of the piston, brought to face the opening of the channel counter to a conventional helical antagonistic spring 51 by a helical spring 52 made from a material with single-effect memory whose action becomes predominant when the temperature rises.

Description

SHOCK ABSORBER HAVING MEMORY MATERIALS
OF SHAPE
The present invention relates to the application of shape memory materials in shock absorbers, in particular those used in suspensions for motor vehicles.

It is known that the damping effect is achieved in an oil damper by the pressure drop resulting from the circulation of the damping fluid through orifices of calibrated sections located in the piston.

However, difficulties arise from the variation in fluidity resulting from variations in oil temperature: - when its temperature increases, following the operation of
I 'shock absorber or depending on weather conditions, I' effect
fluid damping may become insufficient, - on the other hand, for low temperatures, the high viscosity of the oil
can make 1T damper too hard.

 The object of the present invention aims to overcome the above drawbacks by using the properties of shape memory materials.

Such materials are known, generally alloys consisting of copper, zinc and aluminum or titanium and nickel, or else of copper, zinc, aluminum, tin and silicon which deformed, regain their initial shape when their temperature is raised. ; in this case it is a phenomenon called "simple memory effect".

In certain cases, when the sample has undergone a special preliminary treatment called "education", a change in shape can be observed both on cooling and on heating; this reversible effect is also called "double memory effect".

Furthermore, it is known to adjust the shape change temperatures by acting on the composition of the alloys and their manufacturing process.

The present invention will be described by way of nonlimiting example with regard to Figures 1 to 8 attached, which relate respectively - Figure 1, to a longitudinal section of a damper according to 1 state of
the prior art, FIG. 2, to a similar section of a detail of the piston of the shock absorber
according to a first embodiment of the invention, - Figure 3, a plan view of the upper face of the piston according to the
embodiment of FIG. 2, - FIG. 4, in a section of a first variant of the invention, - FIGS. 5 to 7, in plan views of three other variants of the
piston according to the invention, - Figure 8, a cross section of the piston of the last variant.

With reference to FIG. 1, the damper comprises, in a manner known per se, a closed cylinder 1 secured by a fastener 2 to the body of the vehicle, inside which moves a piston 3 and its rod 4, of which
I 'other end 5 is fixed to the wheel arm which we want to reduce movement.

The piston 3, visible in detail in FIGS. 2 and 3, is pierced with the usual channels 6 for the pressure drop of the fluid passing through it, and with channels 7 specific to the invention; the latter open out into a cavity 8 inside which a shutter 9 can be discussed, shown in the low position of occlusion in FIG. 2; it has a T shape and is provided with holes 10 - 11 ensuring the internal circulation of one oil from its upper part to its lower part. It can be seen that in the high position, the shutter 9 lets the oil pass through the piston 3 via the channel 7.

In addition, on the upper and lower faces of the shutter 9 and on the edges of the cavity 8 which face it, a helical spring 12 made of a memory material known per se and a conventional helical spring 13 plus are respectively disposed. powerful than the previous one at low temperatures.

According to this arrangement, as long as the damping oil is at low temperature, the pressure exerted by the spring 13 keeps the shutter 9 in the high position in the cavity 8.

The oil coming from the upper or lower parts of the piston 3 passes through the openings 10 - 11 and flows through the lower or upper parts of the conduit 7.

When the oil heats up above the temperature from which the spring 12 returns to its initial shape, of greater length, the shutter 9 assumes the position of FIG. 2, according to which the flow is interrupted in the conduit 7 As a result, only the usual channels 6 are active, thereby reducing the total flow through the piston 3 and thus compensating for the decrease in viscosity of the oil.

A similar operation is obtained using the variant illustrated in FIG. 4; elements 40 - 41 of double-effect shape memory material are arranged inside the piston 3 which they pass through; they consist of a body pierced with a channel 42, provided with at least two distant extensions 43-44 and closing the channel 42 by resuming their initial shape at high oil temperature, while they are separated each other for low temperatures.

The variants of FIGS. 5 and 6, in which only the channel or channels 7 provided with the devices of the invention are shown, obtain the same result of locking these channels by the rotation about a plane shutter 50 around an axis 0, controlled by one or two springs of memory material.

In the case of FIG. 5, a conventional spring 51 maintains the shutter 50 in the open position for low oil temperatures, at
I 'against a spring 52 calibrated weaker in single effect memory material. When the temperature rises, the memory spring 52 becomes predominant and brings the shutter 50 to the closed position illustrated in FIG. 5.

According to the arrangement in FIG. 6, the two preceding springs 51 - 52 are replaced by a spring 53 made of double-effect memory material, the deformation of which for low temperatures displaces 1 <shutter 50 in the open position and returns it to the position for high oil temperatures.

In the case of the variants of the invention illustrated in FIGS. 7 and 8, use is made as previously of planar shutters but these consist of petals 70 made of double-effect memory materials fixed at 71 on the piston 3, s' moving away from the surface (Figure 8) for low temperatures but squeezing it (Figure 7) for high temperatures of the damping fluid.

In all cases, the increase in the shape change temperature of the elements according to the invention is effected by modulating the composition of the alloys, as is generally known to those skilled in the art, in particular by praising the content. in nickel of the titanium nickel alloys mentioned above.

Note that we can use materials operating at different temperatures to form the shutter elements of the same piston 3, which allows to modulate according to the oil temperature the number of open and closed shutter elements and therefore to optimize the liquid flow.

Claims (2)

1 / Damper of the type comprising a piston (3) provided with channels (7)  provided with elements of shape memory materials which act on  their flow rate, characterized in that the channels (7) are each provided  a plane shutter (50) movable in rotation on the surface of the piston (3),  brought opposite the opening of the channel (7) against a spring  classic helical antagonist (51) by a helical spring (52) in  single effect memory material whose action becomes predominant  when the temperature rises. 2 / shock absorber according to claim 1, characterized in that the two  springs (51 - 52) are replaced by a coil spring made of material  double acting, bringing the plane shutter (5û) facing the opening of the  channel (7) for high oil temperatures but releasing this  opening for low temperatures of this fluid.