Protector shield for a sidewall of a motor vehicle tire, and a wheel assembly for such a vehicle incorporating it

1. A wheel assembly for a motor vehicle comprising a multi-piece wheel rim comprising two pieces a tire having beads mounted respectively against axially inner and outer flanges of said rim, and at least one protector shield in a form of a curved ring which is mounted on said rim to protect at least one sidewall of the tire and which extends along at least a part of the radial height of said at least one sidewall,

wherein said shield includes a fire protection part which defines an outer convex face of said shield and which comprises a cross-linked rubber composition which exhibits flame retardant and heat resistance properties for imparting to said tire a fire protection against flames and flammable substances, said shield being integrally formed of said fire protection part which consists of said cross-linked rubber composition and optionally of at least one reinforcing layer made of fabric, fiberglass or metal, and

wherein said shield is fixed to a radially outer end of a circumferential support which is attached to said pieces of said wheel rim in a junction zone of said pieces, said radially outer end of the support extending axially outside said rim so that said shield is not in contact with the rim.

2. A wheel assembly according to claim 1 , wherein said at least one shield comprises:

an inner substrate part defining an inner concave face of said shield and exhibiting tensile strength and flexural properties, and

an outer fire protection part comprising a cross-linked rubber composition exhibiting flame retardant and heat resistance properties,

said substrate part having a radially inner end portion extending radially below that of said protection part, said shield being clamped between said bead and the corresponding rim flange by said end portion.

3. A wheel assembly according to claim 1 , wherein the radius of curvature of said at least one shield is smaller than that of the corresponding sidewall, said shield being designed so as not to be in contact with this sidewall radially above said corresponding flange.

4. A wheel assembly according to claim 1 , wherein said at least one shield is fixed to the corresponding flange of said wheel rim by means of an annular insert which is attached to said flange, so that a radially inner end of the shield is located between and in contact with said flange and said insert.

5. A wheel assembly according to claim 1 , wherein said pieces are fixed together in said junction zone by circumferentially spaced rim bolts, and wherein said shield is fixed by supporting bolts to said radially outer end of said support.

6. A wheel assembly according to claim 1 , wherein said rubber composition exhibits a Shore A hardness greater than 50.

7. A wheel assembly according to claim 1 , wherein said rubber composition comprises reinforcing short fibers, which are dispersed in this composition.

8. A wheel assembly according to claim 1 , wherein said rubber composition is based on at least one elastomer and further comprises: (phr: parts by weight per hundred parts of elastomer(s)) from 1 to 50 phr of a foaming agent,

from 1 to 50 phr of a charring agent,

from 1 to 55 phr of a blowing agent,

from 1 to 100 phr of a fire retardant additive, and

from 5 to 15 phr of a smoke suppressant additive, and

from 7 to 50 phr of a fire barrier additive.

9. A wheel assembly according to claim 1 , wherein said elastomer is selected from the group consisting of polychloroprenes, natural rubber, polyisoprenes, ethylene-propylene-diene terpolymers, ethylene-propylene copolymers, ethylene-vinyl acetate, chlorinated polyethylene, chorosulfonated polyethylene, and mixtures thereof.