WO2018001752A1 - Material for a vibration filtering device, vibration filtering device, and wiper system comprising such a device - Google Patents

Abstract

The invention relates to a material (M) adapted to active structure-borne sources of the small electric motor type for a motor vehicle, for which sources vibration excitation is of the acceleration source type in a frequency band of between 40 and 2000Hz, characterised in that the hardness of the material is less than or equal to 40 Shore A and its tensile strength is greater than 10MPa.

Description

 VIBRATION FILTRATION DEVICE MATERIAL, VIBRATION FILTRATION DEVICE, AND WIPING SYSTEM

 INCLUDING SUCH A DEVICE

The field of the present invention is that of filtering vibrations generated by the operation of small electric motors. By small electric motor of small size is meant in the context of the present invention a stepping motor, an actuator, a DC motor or an asynchronous motor, whose mass is less than 10 kg, in particular used for o operating equipment for vehicles, and more particularly equipment for wiping the windows of a vehicle.

 The type of motor concerned by the invention thus constitutes an active solid source and has the main characteristic that the levels of vibrational acceleration that we will seek to filter are of the same order of magnitude.

15 magnitude regardless of the frequency, for a frequency band between 40 and 2000Hz. This type of source can be qualified as a source of acceleration, compared to sources, rather larger size and mass, whose displacement levels would be of the same order of magnitude regardless of the frequency, for a band useful frequency

Between 10 and 300 Hz, typically.

 There is thus a need to define a specific material for a filtration device adapted to an active solid source for which the vibratory excitation is of the acceleration source type in a frequency band of between 40 and 2000 Hz.

 An example of such an active, non-limiting solid source of the invention is a windshield wiper system motor. Motor vehicles are commonly equipped with a windshield wiper system to sweep and wash the windshield or rear window and prevent the driver's vision from being disturbed. The wiper motor is

Associated with either a mechanical system, conventionally a crank system or an electronic function, so as to provide an angular back and forth movement of one or more output axes. On these output axes, are positioned elongated arms, themselves carrying scraper blades. These The blades rub against the windshield and drain the water away from the driver's field of vision.

 The wiper system is generally mounted on the vehicle or more particularly on the chassis, in at least three attachment points provided for this purpose, by means of interface parts called damping pads.

 The damping pads have the function of filtering the vibrations generated by the active ground substrate before their transmission via the points of fixation towards the interior of the vehicle where they are perceived by the vibratory sensory cues. and / or acoustic passengers. The function of filtering damping studs for an acceleration source such as a wiping system depends on the order of magnitude of the dynamic transfer rate values of the stud. damping, in compression com ment ment. The dynamic transfer stiffness (ISO-10846) is defined for a given filtration device, a level

Of given frequency, under a given pre-charge, at a given temperature, and a solicitation level given by a binomial in shear (modulus and phase shift or real and imaginary part) and in compression (module and phase shift or real and imaginary part) ). Its value, in N / m, is measured using a device for measuring direct or indirect stiffness according to the ISO-

10846. The modulus of elasticity of a given material is a transfer stiffness related to the form factor of the test piece.

The wiping noises perceived in the passenger compartment originate in particular from the vibrations created by the electric motor by vibrating through the attachment points 25 towards the chassis to finally radiate inside the passenger compartment.

 The rubber damping pads located at the interface between the wiper system and the fixing points have the function of filtering these vibrations, in other words to limit the transmission effect.

However, the current pads do not meet the expectations. Indeed, the perceived noise inside the cabin can have troublesome components up to 2000Hz and to fulfill the function of filtration, it is advisable to design rubber pads able to filter the vibrations on the widest possible range from 40-2000Hz. The dynamic stiffness of transfer of the damping pad varies as a function of the frequency, the temperature, the level of precharge and the level of stress: for frequencies close to 1000 Hz the pads used in the prior art have values of dynamic stiffness of transfer too important for satisfactory filtration.

 There is a need to provide rubber pads with characteristics having a dynamic transfer stiffness curve that is low dependent on the frequency at ambient temperature, under given load condition and for an acceleration source.

 In addition, developing a material of very low hardness has the disadvantage of degrading the mechanical properties of the material, and in particular, the characteristic of resistance to rupture, is found at a low level of the order of 6 to 8 MPa . There is a need to design a material of very low hardness while having satisfactory mechanical properties.

 The object of the present invention is therefore to meet at least in part the needs described above.

 According to a first aspect, the subject of the invention is a material adapted to active solid-state sources of the small electric motor vehicle type for which the vibratory excitation is of the "acceleration source" type in a frequency band of between 40.degree. and 2000Hz, characterized in that in that its hardness is less than 40 Shore A and its level of resistance to fracture is greater than 10MPa, its hardness is preferably less than or equal to 38 Shore A.

 The level of resistance to rupture is, for example, greater than 12 MPa, or even greater than or equal to 14 MPa.

The material according to the invention has, in particular, viscoelastic characteristics such as the complex modulus of elasticity | E ^* | , measured for a frequency of 1000 Hz under excitation of 0.1 m peak / peak, under 8% pre-charge, and at room temperature, less than 8.5 MPa. The modulus of elasticity complex | E ^* | corresponds substantially to the real part of the modulus of elasticity E '.

The modulus of elasticity complex | E ^* | , measured for a frequency of 200 Hz under excitation of 2.5 μιτι peak / peak for an example of a cylindrical stud of height 14 mm and section 6 mm 2 made of a material according to the invention is example less than 4.5 MPa. According to another example, the complex modulus of elasticity | E ^* | , measured for a frequency of 50Hz under 40 μιτι peak / peak, under 8% precharge, and at room temperature is less than 3.8 MPa.

5

 Material

 The hardness of the material is, for example, between 20 and 40 Shore A, in particular between 30 and 40 Shore A, in particular between 35 and 40 Shore A, and even between 35 and 38 Shore A.

In a manner known to those skilled in the art, the hardness is measured at ambient temperature using a standard durometer.

 According to other features of the invention, independently or in combination:

 - The material includes several rubbers.

 The material comprises at least one rubber of grades extended with oils, especially extended to 100 phr ("phr" in English). By rubber of grades extended to oils is meant a rubber containing a pre-integrated plasticizing oil during the polymerization phase. These elastomers of very high molecular weight are capable by their internal structure, of

Remember the plasticizing oil.

 The material comprises a mineral oil of petroleum origin composed of units with a paraffinic, naphthenic and aromatic structure, the content of paraffinic structure units is in particular greater than 60% and the content of units with an aromatic structure of less than 10%.

 The material comprises SBR (styrene-butadiene) rubber and / or EPDM (ethylene-propylene-diene monomer) rubber

 The material comprises at least one EPDM rubber with an ethylene content of greater than 60%, in particular an EPDM rubber extended with oils.

 The material comprises at least one EPDM rubber with an ethylene content of between 45% and 50%,

the material comprises at least one EPDM rubber with a diene content greater than 5%, or even greater than 8%, - The material has a Mooney viscosity of less than 40 Mooney points, especially between 34 and 40 points Mooney ML (1 +4) 100 ° C according to the current standard NFT43005.

 The invention makes it possible to achieve a very low level of hardness of less than 40 Shore A or even of the order of 30 to 40 Shore A without resorting to a material having a high plasticizer content, which would prevent - during making the mixture - to generate sufficient friction between the elastomer and the other additives needed for formulation.

 The choice of EPDM rubber of extended oil grades allows for better oxidation resistance, especially ozone resistance which is compatible with standards. The material used in the invention thus has an ability not to generate cracking after exposure to 200 ppm of ozone concentration at 40 ° C for 72 hours under a deformation of 15%.

 The diene content is especially chosen to allow a better vulcanization efficiency.

 An ethylene content greater than 60% allows the EPDM grade thus selected to have a semicrystalline character which gives it a better mechanical strength than the conventional EPDM grades, amorphous at ethylene levels of the order of 50 to 50%. 60%.

20 Filtration device

 According to another of its aspects, the subject of the invention is a filtration device for a small electric motor, in particular a vehicle, made of a material as described above.

 Thanks to the invention, by virtue of the viscoelastic characteristics of the material chosen, the device provides better decoupling between the engine attachment means, in particular a wheelhouse, and the passenger compartment.

The device has in particular a dynamic transfer stiffness at ambient temperature between 0.1 N / m and 10 N / m in the frequency band between 40 and 2000 Hz, in particular between 50 and 1000 Hz. The dynamic stiffness, expressed in N / m, is measured at room temperature using a DMA (Dynamic Mechanical Analysis).

The device comprises for example a pad or damper block. The filtration device is used in particular for mounting a support of a wiper mechanism.

 The stud comprises in particular a bore which is for example through. The bore is located in particular at the longitudinal axis of the stud.

 The damping device is for example as disclosed in the patent application EP 2 767 768.

 According to yet another of its aspects the subject of the invention is a wiper system of a window of a vehicle comprising at least one filtration device as described above,

The system comprises, for example, three filtration devices. The filtration devices are of identical shape or not.

Other characteristics, details and advantages of the invention will emerge more clearly on reading the description given below as an indication in relation to drawings in which:

 FIG. 1 shows in perspective a wiper system of a window of a vehicle according to the invention,

 FIGS. 2 to 6 illustrate exemplary embodiments of filtration devices according to the invention, and

- Figures 7 to 12 illustrate in axial section other embodiments of filtration devices.

 FIG. 1 shows a wiper system 20 for a window 150 of a vehicle which comprises a motor-driver 22, two drive shafts 24 for the wiping brushes 25 rotating about a 25 vertical axis, and a wheelhouse 26 which converts the continuous rotational movement u of the output of the motoréducteu r 22 in an alternating rotational movement of each drive shaft 24.

The wiper system 20 is mounted on a body structure element of the vehicle 100 at three points defined by mounting means 32 of the wiper system arranged to cooperate with complementary means 36 of the wiper system. structural element of ca isse 1 00. The wiper / wiper system 20 is an element which generates vibrations which are transmitted to the users of the vehicle when the wiper system 20 is specifically connected to the wiper system. the body structure element.

 For the purpose of filtering the vibrations produced by the windshield wiper mechanism 20, and to prevent them from being transmitted to the body structure element of the vehicle. , the mounting means 32 each comprise a filter device 10 which is interposed between the wheelhouse 26, in particular a support 1 4 of the wheelhouse lustred on the examples of Fig ures 7 to 1 1, and the structure checkout 1 00.

 The filtration devices 10 of the wiper system 20 comprise a damping block 1 made of a material M having a hardness of less than 40 Shore A and a level of tensile strength greater than 10 MPa.

In the example illustrated, the hardness of the material M is in particular between 20 and 40 Shore A.

 In particular, the material has a Mooney viscosity of less than 40 Mooney points, in particular between 34 and 40 Mooney points ML (1 +4) 100 ° C.

 In the illustrated example, the constituent material of the damping devices 1 comprises several rubbers M1, M2. It comprises in particular at least one rubber of extended grades with oils, especially extended to 100pcc.

 The material comprises in particular a first EPDM rubber with an ethylene content of greater than 60% and a second EPDM rubber, the latter having an ethylene content of between 45% and 50%.

 The first and second EPDM rubber have a diene content greater than 5%, in particular greater than 8%. The damping blocks 1 of the devices 10 illustrated in FIGS. 2 to 6 comprise, for example, a groove 30 between two flanges 12. They may have, according to the embodiments, a symmetry of revolution along their longitudinal axis X.

The damping devices 10 include in particular a through bore 16. Example of realization:

From the point of view of the mixing process, this formula is balanced according to a filler ratio of (carbon black + chalk) / plasticizer of 74/30 phr making it possible to produce a homogeneous mixture according to a process of industrial type, of rapid incorporation. (of the order of five minutes) and causing no phenomenon of sticking to the walls of the mixer.

The amount of oil already contained in the polymer makes it possible to give the mixture its flexibility.

The Mooney viscosity level of material equal to 33 pts Mooney is

 low enough and allows to consider a compression molding process, or tranfert compression, or even by injection molding.

The mixture thus made and then vulcanized for 10 minutes at 190 ° C. by compression molding.

 It has the following mechanical properties:

 hardness (Shore A) (pts) 38

 Module 100% (MPa) 0.9

 Module 300% (MPa) 2.4

 breaking strength (MPa) 14

 elongation at break (%) 980

hardness (Shore A) (pts) 38 During the tests carried out, for a frequency range between 40 and 1000 Hz, the modulus of the dynamic transfer stiffness measured varies between 0.1 N / m and 10 N / m.

 The invention is not limited to the illustrated examples. The above material examples include an EPDM rubber. The invention also covers materials comprising an SBR rubber.

Claims

 1. Material (M) adapted to active solid-state sources of small electric motor type for a motor vehicle for which the vibratory excitation is of the acceleration source type in a frequency band of between 40 and 2000 Hz, characterized in that its hardness is less than 40 Shore A and its level of tensile strength is greater than 10 MPa. 2. Material according to claim 1, wherein the hardness is between 20 and 40 Shore A, or even between 30 and 38 Shore A. 3. Material according to any one of the preceding claims, comprising several rubbers (M1, M2). 4. Material according to any one of the preceding claims, comprising at least one rubber of extended grades with oils, in particular extended to 100pcc 5. Material according to any one of the preceding claims, comprising a mineral oil of petroleum origin composed of units with paraffinic, naphthenic and aromatic structure, the paraffinic structure and aromatic structure units being in particular respectively greater than 60%. and less than 10%. The material of any of the preceding claims comprising an EPDM rubber. 7. Material according to any one of the preceding claims, comprising at least one EPDM rubber having an ethylene content of greater than 60%, in particular an EPDM rubber extended with oils. 8. Material according to any one of the preceding claims, comprising at least one EPDM rubber with an ethylene content of between 45% and 50%. 9. Material according to any one of the preceding claims, comprising at least one EPDM rubber with a diene content greater than 5%, or even greater than 8%. 10. Material according to any one of the preceding claims, having a Mooney viscosity of less than 40 Mooney points, especially between 34 and 40 Mooney points. 11. A vibration filtering device (10) for a small electric motor, particularly a vehicle, comprising a damping block (1) made of a material (M) according to any one of the preceding claims. 12. System for wiping (20) a window of a vehicle comprising at least one filtration device (10) according to the preceding claim. 15