Spring devices – Vehicle – Compound
Reexamination Certificate
1999-06-11
2001-05-29
Butler, Douglas C. (Department: 3613)
Spring devices
Vehicle
Compound
C267S286000, C267S292000, C267S166000
Reexamination Certificate
active
06237901
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a new type of suspension with dynamically variable flexibility or stiffness and whose flexibility is increased in the region of rising of the wheels to the shock abutment position, and whose stiffness is increased in the normal working region to the suspended wheel position.
DESCRIPTION OF THE RELATED ART
Until the present, most suspensions have linear flexibility and use stiffnesses which are the result of a compromise between vertical comfort and supporting the chassis of the vehicle. Thus, the vertical comfort and shock absorbing require high flexibility which permit less transmission of the forces generated in the chassis, as well as low frequencies of oscillation favorable to the comfort of the occupants, whilst supporting the chassis of the vehicles requires, by contrast, high stiffness adapted to counter with low amplitude the movement of the mass.
So as to optimize this compromise, there has been provided anti-deflection bars, which, upon lateral shifting of the mass, stiffen the suspensions when turning, so as to decrease the amplitudes of clearance. The drawback of these elements is that they connect the wheels of a same train, rendering them less independent, and that this connection associated with supplemental friction decreases the performance of the vehicle, both as to vertical comfort and as to ease of steering.
Moreover, consecutive mass transfers during longitudinal accelerations are controlled only by the vertical stiffness of the suspensions.
The suspensions with variable flexibility tend to overcome these drawbacks by providing progressively greater stiffnesses in the course of compression. The drawback of these systems resides in the fact that the bearing wheel, which takes the greatest part of the lateral thrust, is hindered by a great stiffness which is harmful to absorption. On the other hand, the interior wheel is excessively relieved because it suffers from a low stiffness.
Another result of this configuration is that the path of compression being decreased, and the path of expansion increased, the center of gravity of the vehicle rises, which is prejudicial to the behavior of the vehicle.
There also exist controlled suspensions.
The principal drawback of suspension center controlled as to shock absorption, as to the roadbed, and/or as to stiffness, resides of course in the complexity of these systems which raises the cost and renders their reliability and their maintenance more critical.
Finally, there exist other suspensions called “CONTRACTIVE” (trademark) which are the object of numerous patents by the applicant.
Such a suspension is disclosed in EP-B-0 446 338 of the applicant, which has for its object a vehicle wheel suspension using several resilient elements mounted in opposition or not, one relative to the other, or a single resilient element with at least one abutment limiting the operation over at least one portion of said element, said suspension using two separate stiffnesses over the full range of clearance of the vehicle wheel on opposite sides of the working position of the suspension, the inflection point between these two stiffnesses being located adjacent the working position of the suspension, said utilization of different stiffnesses taking place dynamically, characterized in that in the case of a single resilient element, there is used an abutment/pan at a particular position of said spring, so as to obtain a stiffness curve with a double slope, the abutment or abutments are placed in contact for a seat corresponding to the vehicle in working condition, this being done such that, from this position, the abutments are separated and all of the coil spring is stressed upon total collapse of the suspension, whilst in the course of expansion, the presence of an abutment limits the operation over a reduced portion of said helical spring.
This type of suspension functions on three different principles.
First, there are two separate stiffnesses about the static position of the vehicle.
Secondly, the point of change between these two stiffnesses is located precisely at the static position of the vehicle and is called the self-stabilizing reference point.
Thirdly, this reference point, which causes the suspension to swing from one stiffness to the other, is physically constituted by an abutment, provided with an asymptotic stiffness curve, which permits using the contractive element.
It is imperative that this abutment comprise a resilient element which permits facilitating the passage from one stiffness to the other. On a stiffness curve, this translates by a connecting arc between the two straight lines of flexibility of compression and of expansion.
The CONTRACTIVE suspension is thus an asymmetric suspension whose stiffness and expansion is greater to the stiffness and compression, the change of stiffness taking place about the static position of the vehicle by means of a connection abutment.
Nevertheless, this technique requires, to be adapted to a conventional vehicle, the replacement of the suspension assembly.
SUMMARY OF THE INVENTION
The present invention deals with suspensions comprising one or several helical springs; said springs are used for all of their flexibility in the course of a shock whilst only a portion of these springs decompresses during the expansion phase.
These two phases of shock and expansion have as their origin the “working” position of the vehicle suspension.
According to the invention, the CONTRACTIVE operation is ensured integrally by the spring which has been implanted in lieu and in place of the conventional spring without requiring modification of the basic suspension mechanism.
The cost of conversion is greatly decreased and one can say that the omission of anti-deflection bars and the saving that thus arises will largely compensate the increase in cost of the provision of such springs.
To this end, the present invention relates to a vehicle wheel suspension using at least one helicoidal spring, and at least one flexible retaining and connecting armoring, which in working position, stress a portion of the spring and hold it compressed, to obtain two different stiffness curve whose inflection point is in the region of the working position; relative to this position, upon compression, the assembly of the helicoidal spring is compressed whilst, during expansion, only the unstressed portion of said spring is decompressed, the suspension being therefore asymmetric with the stiffness in expansion which is greater than the stiffness in compression, characterized by the fact that each armoring is constituted, on the one hand, of two securement and retaining elements, one co-acting with all or a portion of a winding of the helicoidal spring, the other co-acting either with all or a portion of another winding of said spring, or with the body of the shock absorber, and on the other hand, of a longitudinal element, deformable in compression and indeformable in expansion, secured to the two securement and retaining elements, the armoring enclosing and constraining at least two windings of said helicoidal spring.
In the case in which the suspension uses a single helicoidal spring and at least one flexible retaining and connecting armoring, in which the two securement elements of each armoring co-act with all or a portion of two windings of the helicoidal spring, each armature is constituted by an elastic band which circumscribes all or a portion of at least two windings of said spring, the securement elements being constituted by loops of the elastic band and the two free ends being secured one to the other.
In the case in which the suspension utilizes a single helicoidal spring and at least one flexible retaining and connecting armature in which the two securement and retaining elements of each armature co-act respectively with all or a portion of one of the spires of the helicoidal spring and with the body of the shock absorber, each armature is constituted by an elastic band which circumscribes all or a portion of at least two windings of said spring,
Butler Douglas C.
Mauro Bianchi S.A.
Young & Thompson
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