Viscoelastic seal for reducing structure-borne noise in a vehicle

Abstract

The present invention relates to a viscoelastic seal for a glazed element of a vehicle, the seal having an equivalent loss factor tanδeq between 0.35 and 0.85, and having an equivalent real stiffness K' eq between 500 MPa and 12 GPa, the equivalent loss factor tanδeq and the equivalent real linear stiffness K' eq being measured at 20 °C and at a frequency of 100 Hz.

Description

Title of the invention: Viscoelastic joint for reducing solid-borne noise in a vehicle Field of invention

[0001] The present invention relates to a viscoelastic seal suitable for fixedly mounting a glazed element to a vehicle body and allowing a reduction in solid-borne noise emitted in a vehicle passenger compartment by the glazed element. State of the art

[0002] It is known to use a seal, for example in the form of a profile, to securely mount a glazed element to a vehicle body. However, the seal allows mechanical vibrations to be transmitted from the body to the glazed element, for example to a windshield. The vibrations can cause movement of the glazed element in the same way as a loudspeaker membrane, which results in sound emission into the vehicle interior and thus reduces user comfort. This type of sound emission is known as structure-borne noise.

[0003] For this purpose, it is known to reinforce the structure of the bodywork to limit the vibrations transmitted to it. However, this solution can lead to an increase in the mass of the vehicle.

[0004] It is also known to use a glazed element formed by a laminate, the laminate comprising two sheets of glass separated by a damping viscoelastic layer. However, this solution has a high manufacturing cost and an efficiency limited to very low frequencies, that is to say for frequencies below 200 Hz.

[0005] Finally, document No. EP1815099 describes other solutions for reducing solid-borne noise. One of the solutions described consists of fixedly mounting the glazed element on the bodywork using a discontinuous seal, so as to leave certain parts of the glazed element free. Another solution described consists of using a seal formed by a material having both a high loss factor, in this case greater than or equal to 0.7, and a low elastic shear modulus, in this case less than or equal to 3 MPa measured in a temperature range of 10°C to 40°C and for frequencies between 20 Hz and 500 Hz. However, despite the reduction in solid-borne noise brought about by these solutions, it remains desirable to reduce solid-borne noise excessively. Statement of the invention

[0006] An aim of the invention is to propose a solution making it possible to reduce the solid-borne noise in the passenger compartment of a vehicle with regard to the solid-borne noise emitted during the implementation of the solutions proposed in the prior art.

[0007] This object is achieved within the framework of the present invention by means of a viscoelastic seal for a glazed element of a vehicle, the seal having an equivalent loss factor tanôeq of between 0.35 and 0.85, and having an equivalent linear real stiffness K'eq of between 500 MPa and 12 GPa, the equivalent loss factor tanôeq and the equivalent linear real stiffness K'eq being measured at 20°C and at a frequency of 100 Hz.

[0008] The present invention is advantageously supplemented by the following characteristics, taken individually or in any of their technically possible combinations:

[0009] - the seal has an equivalent loss factor tanôeq of between 0.60 and 0.70, and has an equivalent linear real stiffness K'eq of between 700 MPa and 1.2 GPa, the equivalent loss factor tanôeq and the equivalent real stiffness K'eq being measured at 20 °C and at a frequency of 100 Hz,

[0010] - the seal is formed by a material comprising a polyurethane,

[0011] - the polyurethane comprises at least two components,

[0012] - the seal is formed by a material, the material comprising a plasticizer, the fraction mass of plasticizer in the material being between 0.1% and 10% and in particular between 0.5% and 5%,

[0013] - the plasticizer comprises a di-isononyl isonyl phthalate,

[0014] - the seal is formed by a material comprising at least one element chosen from a polyvinyl chloride, a polyepoxide, a silane-modified polymer, a polysulfide, an ethylene-propylene-diene, a butyl, a nitrile, a styrene-butadiene and a polyacrylate,

[0015] - the seal is formed by a material having a glass transition temperature between 10°C and 50°C,

[0016] - the joint comprises at least two adjacent parts, the two parts being formed by different materials,

[0017] Another aspect of the invention is a vehicle comprising a bodywork, a glazed element and a seal according to an embodiment of the invention, the seal having a first face fixedly mounted on the bodywork and a second face fixedly mounted on the glazed element.

[0018] The vehicle advantageously comprises an electric motor. Description of figures

[0019] Other characteristics, aims and advantages of the invention will emerge from the following description, which is purely illustrative and non-limiting, and which must be read in conjunction with the appended drawings in which:

[0020] [Fig.l] - [Fig.l] schematically illustrates a section of a joint according to an embodiment of the invention formed by a single solid material,

[0021] [Fig.2] - [Fig.2] schematically illustrates a section of a joint according to an embodiment of the invention formed by two parts, each of the parts being formed by a different material, the two parts being superimposed,

[0022] [Fig.3] - [Fig.3] schematically illustrates a section of a joint according to an embodiment formed by two parts, each of the parts being formed by a different material, the two parts being juxtaposed,

[0023] [Fig.4] - [Fig.4] illustrates vibration transfers between a rebate of a bodywork and a central point of a glazed element of a vehicle,

[0024] [Fig.5] - [Fig.5] illustrates vibration transfers between a rebate of a bodywork and a lateral upper point of a glazed element of a vehicle.

[0025] Throughout the figures, similar elements bear identical references. Definitions

[0026] The term “stiffness” of an element is understood to mean the tension-compression stiffness of the element. The shear modulus of the element will not be taken into account. In a known manner, the equivalent linear stiffness K*eq of the element is a complex number defined by K*eq = K'eq+ jK”eq, where K'eq is the equivalent real linear stiffness and K' eq is the equivalent complex linear stiffness, also called the equivalent linear dissipation power. The loss factor tanôeq of the element is defined by tanôeq lk eq / lk eq*

[0027] In the present application, the terms “equivalent linear stiffness” will be used to cover both the linear stiffness of a part formed from a single material and the equivalent linear stiffness of a part formed from several materials.

[0028] It is known that the equivalent linear stiffness K*eq of a part comprising several materials can be defined by the following formula: ^ 29 ] [^] a =E«r (i)

[0030] in which K*; is the complex linear stiffness of each material i forming the part, a = -1 for a stack of several materials i between the bodywork and the glazed element, and a = 1 for a juxtaposition of several materials i between the bodywork and the glazed element.

[0031] The equivalent real linear stiffness K'eq and the loss factor tanôeq are measured using a viscoanalyzer. The viscoanalyzer measures an equivalent real stiffness k' eq and an equivalent dissipation power k”eq of an element, more particularly of a part of a joint, the part extending along a length L. The equivalent real linear stiffness K'eq is calculated according to the following formula: K'eq = k'eq / L. The equivalent loss factor tanôeq of the profile is calculated according to the following formula: tanô eq eq' eq*

[0032] The equivalent linear stiffness K*eq of a part formed by a material with a complex Young's modulus E* is defined by the following formula: K*eq = E*.(l / h) where l is a width of a section of the part and h is a height of the section of the part. In a decomposed manner, it follows that K*eq = K'eq+jK”eq = E'.(Z / / z) + j. E”.(l / h), where E' is the real part of the complex Young's modulus and E” is the imaginary part of the complex Young's modulus.

[0033] The stiffness(ies) of the joint can be measured as defined by ISO 18437. Detailed description of the invention

[0034] General description of the joint 1

[0035] With reference to [Fig. 1], a viscoelastic seal 1 is suitable for a glazed element 2 of a vehicle 3 and more particularly for fixedly mounting a glazed element 2 to a body 5 of the vehicle 3. The viscoelastic seal 1 may be solid. The seal 1 extends along a length L and has a section extending along a width l and a height h. The seal 1 may have a first face 6 suitable for being fixedly mounted on the body 5. The seal 1 may have a second face 7 suitable for being fixedly mounted on the glazed element 2.

[0036] The seal 1 has an equivalent loss factor tanôeq of between 0.35 and 0.85, the equivalent loss factor tanôeq being measured at 20°C and at a frequency of 100 Hz. The seal 1 has an equivalent real linear stiffness K'eq of between 500 MPa and 12 GPa, the equivalent real linear stiffness K'eq being measured at 20°C and at a frequency of 100 Hz. Thus, when the seal 1 is mounted fixed to the bodywork 5 and to the glazed element 2, the coupling of the glazed element 2 to the bodywork is increased, which has the result of reducing the emissions of solid-borne noise, in particular for frequencies below 100 Hz, compared to known seals. This result goes against known technical teachings, in particular the teaching of document no. EP1815099, in which it is described that to reduce solid-borne noise, a joint can have a high loss factor and a small stiffness compared to known joints.

[0037] In particular, the seal 1 may have an equivalent loss factor tanôeq of between 0.60 and 0.70 and have an equivalent real linear stiffness K'eq of between 700 MPa and 1.2 GPa, the equivalent loss factor tanôeq and the equivalent real stiffness K'eq being measured at 20°C and at a frequency of 100 Hz.

[0038] Material(s) forming the seal 1

[0039] The seal 1 may be formed by a material comprising at least one element chosen from a polyurethane, a polyvinyl chloride, a polyepoxide, a polymer modified silane, a polysulfide, an ethylene-propylene-diene, a butyl, a nitrile, a styrene-butadiene and a polyacrylate. The material preferably comprises a polyurethane. For example, the polyurethane adhesive "Araldite 2018", of the registered trademark "Araldite" can be used to form the joint 1. The material can be a polyurethane comprising at least two components. Thus, the durability of the joint can be increased.

[0040] The material may comprise a plasticizer. A mass fraction of the plasticizer in the material may be between 0.1% and 10%, and in particular between 0.5% and 5%. The plasticizer may comprise a di-isononyl di-isonyl-phthalate (DINP). Thus, it is possible to increase the value of the equivalent loss factor of the seal 1 in the range previously defined, for an equivalent real stiffness of the seal substantially equal to that of a seal formed by the same material without plasticizer.

[0041] The material may have a glass transition temperature of between 10°C and 50°C.

[0042] Joint 1 formed by a plurality of materials

[0043] With reference to [Fig. 2] and [Fig. 3], the seal 1 may comprise at least two adjacent parts 4, the two parts 4 being formed by different materials. With reference to [Fig. 2], each part 4 may form a layer, the two layers being superimposed. One of the two layers may have the first face 6, and the other of the two layers may have the second face 7. Thus, the first face 6 may have maximized adhesion with the material forming the bodywork 5 and the second face 7 may have maximized adhesion with the material forming the glazed element 2. In addition, the seal 1 comprising two superimposed layers may have a pair of values ​​of the equivalent loss factor tanôeq and the equivalent real stiffness K'eq impossible to obtain using a single material. With reference to [Fig.3], each part 4 can be juxtaposed with the other part 4, so that each of the parts 4 is adapted to be in contact both with the bodywork 5 and with the glazed element 2.

[0044] [Fig.4] and [Fig.5] illustrate vibration transfers between a rebate of the body 5 of a vehicle and between a glazed element 2, the rebate and the glazed element 2 being those of a vehicle of the Volkswagen ID4 type (registered trademark). Curve (a) of [Fig.4] and curve (c) of [Fig.5] each illustrate the vibration transfer implemented by a known seal, in this case the seal sold with the vehicle. Curve (b) of [Fig.4] and curve (d) of [Fig.5] each illustrate the vibration transfer implemented by a seal 1 according to an embodiment of the invention. The seal 1 is mounted fixed in a continuous manner over the entire edge of the glazed element 2. The seal 1 has a section extending over a width l equal to 12 mm and extending over a height h equal to 5 mm. The equivalent loss factor tanôeq of the joint, measured at 20 °C and at a frequency of 100 Hz, is equal to 0.6. The equivalent linear stiffness K'eq, measured at 20 °C and at a frequency of 100 Hz, is equal to 900 MPa. Curve (a) and curve (b) illustrate vibration transfers measured at a central point of the glazed element 2. Curve (c) and curve (d) illustrate vibration transfers measured at an upper lateral point of the glazed element 2.

Claims

Claims

1. Viscoelastic seal (1) for a glazed element (2) of a vehicle (3), the seal (1) having an equivalent loss factor tanôeq of between 0.35 and 0.85, and having an equivalent linear real stiffness K'eq of between 500 MPa and 12 GPa, the equivalent loss factor tanôeq and the equivalent linear real stiffness K'eq being measured at 20°C and at a frequency of 100 Hz.

2. Joint (1) according to claim 1, having an equivalent loss factor tanôeq of between 0.60 and 0.70, and having an equivalent linear real stiffness K'eq of between 700 MPa and 1.2 GPa, the equivalent loss factor tanôeq and the equivalent real stiffness K'eq being measured at 20°C and at a frequency of 100 Hz.

3. A seal (1) according to claim 1 or 2, formed by a material comprising a polyurethane.

4. A seal (1) according to claim 3, wherein the polyurethane comprises at least two components.

5. Joint (1) according to one of claims 1 to 4, formed by a material, the material comprising a plasticizer, a mass fraction of plasticizer in the material being between 0.1% and 10% and in particular between 0.5% and 5%.

6. A seal (1) according to claim 5, wherein the plasticizer comprises a di-isononyl isonyl phthalate.

7. A seal (1) according to one of claims 1 to 6, formed by a material comprising at least one element chosen from a polyvinyl chloride, a polyepoxide, a silane-modified polymer, a polysulfide, an ethylene-propylene-diene, a butyl, a nitrile, a styrene-butadiene and a polyacrylate.

8. Seal (1) according to one of claims 1 to 7, formed by a material having a glass transition temperature between 10°C and 50°C.

9. Joint (1) according to one of claims 1 to 8, comprising at least two adjacent parts (4), the two parts (4) being formed by different materials.

10. Vehicle (3) comprising a body (5), a glazed element (2) and a seal (1) according to one of claims 1 to 9, the seal (1) having a first face (6) fixedly mounted on the body (5) and a second face (7) fixedly mounted on the glazed element (2).

11. Vehicle (3) according to claim 10, comprising an electric motor.

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