Patent Application
20050244605
The present invention relates to the use of an adhesive for assembling a member and a wheel, to a member-and-wheel assembly, to a member, and to a wheel.
Car manufacturers are equipping the wheels of vehicles more and more frequently with members having the function of providing information about the tires to a vehicle computer.
Amongst possible members, there are to be found, for example, pressure sensors, temperature sensors, and devices for identifying tires.
Long-term fixing of a member to a wheel is a problem that is difficult to solve, given the stresses to which the member is subjected. In particular, the member is subjected to very high accelerations, due in particular to centrifugal force, and it is also subjected to temperature variations of very large amplitude.
In the state of the art, various methods are known for assembling a pressure sensor to a wheel.
A first known technique consists in integrating the pressure sensor with a tire inflation valve placed on the wheel. Nevertheless, the extra weight due to the pressure sensor can weaken the valve, and as a result, the value runs the risk, little by little, of ceasing to be airtight.
A second known technique consists in placing the pressure sensor in an assembly groove of the wheel and in fixing it by means of a clamping collar that surrounds the assembly groove of the wheel circumferentially. However, the clamping force exerted by the collar decreases over time, and slack tends to appear between the pressure sensor and the wheel.
An object of the invention is to propose a simpler and more effective alternative to those fixing methods, by assembling a member and a wheel by means of an adhesive which withstands those various above-mentioned stresses.
To this end, the invention provides the use of an adhesive for assembling together a member and a wheel, the adhesive presenting the following properties:
the breaking stress in traction of the adhesive is greater than 0.5 megapascals (MPa) at 80° C.; and
the adhesive comprises at least one polymeric component of vitreous transition temperature below −50° C.
The invention thus makes it possible to assemble a member to a wheel in a manner that is simple, fast, and effective. Because of the properties of the adhesive, cohesion of the assembly is ensured under all normal conditions of use of a wheel.
The inventors have found that using an adhesive of the invention enables a pressure sensor weighing 75 grams (g) to be fixed to a wheel up to speeds of 300 kilometers per hour (km/h) for periods of 2 hours (h) and for temperatures lying in the range −30° C. to 120° C.
Because of its viscous nature, the adhesive also presents the advantage of filling in any interstices that might exist between the member and the wheel, thus making it possible in particular to fix members of identical shape on wheels of different diameters, thereby reducing the costs involved in designing, manufacturing, and managing a plurality of members of different dimensions.
The use of an adhesive of the invention may additionally comprise one or more of the following characteristics:
the polymeric component belongs to the group of styrene butadiene rubbers (SBRs) and polybutadienes;
the adhesive comprises at least one other polymeric component of vitreous transition temperature above 100° C.;
the other polymeric component is obtained by condensing an epoxy resin;
the member is assembled on the radially-outer surface of an assembly groove of the wheel;
the member is selected from at least one of the elements in the set comprising: a transmitter, a receiver, a sensor, a pressure sensor, a temperature sensor, and a support for any of the preceding elements;
the member is a support for any of the above-specified elements, the element being secured to the support by snap-fastening; and
the member is a support for any of the above-specified elements, the support including a housing for receiving the element by insertion in an insertion direction that is substantially orthoradial when the support is bonded to the wheel, i.e. a direction substantially perpendicular to a radius of the wheel and passing through the center of the support.
The invention also provides an assembly of a member and a wheel assembled together by means of an adhesive, wherein the adhesive presents the following properties:
the breaking stress in traction of the adhesive is greater than 0.5 MPa at 80° C.; and
the adhesive comprises at least one polymeric component of vitreous transition temperature below −50° C.
An assembly of the invention may further comprise one or more of the following characteristics:
the polymeric component belongs to the group of SBRs and polybutadienes;
the adhesive comprises at least one other polymeric component of vitreous transition temperature above 100° C.;
the other polymeric component is obtained by condensing an epoxy resin;
the member is assembled on the radially-outer surface of an assembly groove of the wheel;
the member is selected from at least one of the elements in the set comprising: a transmitter, a receiver, a sensor, a pressure sensor, a temperature sensor, and a support for any of the preceding elements;
the member is a support for any of the above-specified elements, the element being secured to the support by snap-fastening; and
the member is a support for any of the above-specified elements, the support including a housing for receiving the element by insertion in an insertion direction that is substantially orthoradial when the support is bonded to the wheel.
The invention also provides a member for securing to a wheel, the member including a precoated layer of an adhesive presenting the following properties:
the breaking stress in traction of the adhesive is greater than 0.5 MPa at 80° C.; and
the adhesive comprises at least one polymeric component of vitreous transition temperature below −50° C.
The member of the invention may further comprise one or more of the following characteristics:
the polymeric component belongs to the group of SBRs and polybutadienes;
the adhesive comprises at least one other polymeric component of vitreous transition temperature above 100° C.;
the other polymeric component is obtained by condensing an epoxy resin;
the member is selected from at least one of the elements in the set comprising: a transmitter, a receiver, a sensor, a pressure sensor, a temperature sensor, and a support for any of the preceding elements;
the member is a support for any of the above-specified elements, the element being secured to the support by snap-fastening;
the member is a support for any of the above-specified elements, the support including a housing for receiving the element by insertion in an insertion direction that is substantially orthoradial when the support is secured to the wheel; and
the member weighs 15 g to 90 g.
The invention also provides a wheel for receiving a member, the wheel including a precoated layer of adhesive presenting the following properties:
the breaking stress in traction of the adhesive is greater than 0.5 MPa at 80° C.; and
the adhesive comprises at least one polymeric component of vitreous transition temperature below −50° C.
A wheel of the invention may further comprise one or more of the following characteristics:
the polymeric component belongs to the group of SBRs and polybutadienes;
the adhesive comprises at least one other polymeric component of vitreous transition temperature above 100° C.;
the other polymeric component is obtained by condensing an epoxy resin; and
the precoated layer of adhesive is carried by the radially-outer surface of an assembly groove of the wheel.
The invention also provides a method of assembling an assembly comprising a wheel, a member, and a tire, the method comprising the following steps:
a first step of using an adhesive to assemble the member and the wheel in accordance with the above-defined invention; and
a second step of assembling the tire on the wheel carrying the member;
wherein the two steps are separated by a duration that is predetermined in such a manner that the adhesive bond is sufficiently strong during the second step.
An assembly method of the invention may include one or more of the following characteristics:
the predetermined duration lies in the range 45 seconds to 55 seconds; and
the wheel fitted with the member is stored temporarily between the two steps.
The invention will be better understood on reading the following description given purely by way of example and made with reference to the accompanying drawing, in which:
By way of example, the wheel is made of cast aluminum alloy with a covering of epoxy or polyester.
A member 16 is fixed to the periphery of the wheel 12. In the example shown in FIGS. 1 to 3, the member 16 is a pressure sensor 16 for sensing the pressure in the tire 14, however the invention can apply to any type of member, and in particular the member may serve to support a sensor.
The pressure sensor 16 is positioned on the radially-outer surface of an assembly groove 18 in the wheel 12, as shown in
The pressure sensor is assembled to the wheel by means of a layer 20 of adhesive presenting the following properties:
the breaking stress in traction of the adhesive is greater than 0.5 MPa at 80° C., preferably greater than 1 MPa; and
the adhesive includes at least one polymeric component of vitreous transition temperature below −50° C., and preferably below −60° C.
The polymeric component may be a polymer belonging to the group of SBRs and polybutadienes.
The vitreous transition temperature (“Tg”) of a polymer is the temperature at which the mechanical behavior of the polymer changes from rigid and brittle vitreous behavior to rubbery behavior.
In its vitreous state, a polymer has very good traction strength but poor ability to withstand impacts and vibration.
A polymer in its rubbery state is good at withstanding impacts and vibration.
At a normal temperature of use, i.e. in the range −30° C. to 120° C., the polymeric component of Tg below −50° C. in the adhesive of the invention is in its rubbery state. The adhesive can thus damp vibration and impacts that occur while the wheel is in rotation.
The traction strength of the adhesive is obtained by means of another polymeric component of vitreous transition temperature above 100° C., and preferably above 120° C., e.g. obtained by condensing an epoxy resin.
This other polymeric component, which is in its vitreous state at normal temperatures of use provides the adhesive with its traction strength.
In order to ensure that the properties of both components are conserved in the adhesive, it is important to ensure that the two components are not thoroughly mixed together, i.e. the component should present two-phase behavior. To achieve such a two-phase mixture, the polymeric phase of vitreous transition temperature below −50° C. can be constituted by nodules of diameter greater than 150 micrometers (μm).
The epoxy elastomer adhesive 7240 from the supplier 3M satisfies the above characteristics. The inventors of the present invention have performed centrifuge tests on an assembly comprising a wheel and a pressure sensor assembled together by means of that adhesive and they have found that the adhesive at an initial temperature of 20° C. withstands 2 h centrifuging at 250 km/h, followed by 2 h at 300 km/h, followed by 2 h at 250 km/h. The wheel and sensor assemblies have also withstood temperature cycling between −30° C. and 120° C. under stress from the centrifuge.
The pressure sensor used during testing weighed about 75 g, while the sensors in common use generally weigh 15 g to 90 g.
In a variant shown in
In a first embodiment of the support, as shown in
In a second embodiment of the support, as shown in
By way of example, the sensor 24 is inserted into the housing by being caused to slide with the help of guide means shaped on the support and on the sensor.
The adhesive may be applied between the member and the wheel at the time of assembly or it may be precoated on one or other of the two parts to be stuck together. It is thus possible, for example, to coat adhesive initially on the member, while protecting the coating of adhesive with a peel-off plastics film.
The assembly comprising the wheel, the sensor, and the tire is assembled in a first step by bonding the sensor to the wheel with adhesive, in a second step by mounting the tire on the wheel carrying the sensor, and in a third step by inflating the tire and balancing the wheel-and-tire assembly.
The adhesive takes about 50 seconds to cure, so it is advantageous for the first two steps to be spaced apart by a duration that is substantially equal to 50 seconds so as to ensure that the adhesive withstands mounting of the tire and the rotation that is needed in order to balance the wheel-and-tire assembly.
Since assembling the tire onto the wheel takes about 7 seconds, wheels carrying their respective sensors are stored temporarily between the first two steps. This temporary storage can be implemented, for example, by means of a conveyor transporting the wheels carrying their sensors from the adhesive bonding station to the station for assembling the tire, and by ensuring that this conveyor operation takes about 50 seconds.
| Number | Date | Country | Kind |
|---|---|---|---|
| 0402045 | Feb 2004 | FR | national |
