WO2003064908A1

WO2003064908A1 - Pipe for pressurized automobile fluids

Info

Publication number: WO2003064908A1
Application number: PCT/FR2003/000206
Authority: WO
Inventors: Patrick Bremard
Original assignee: Nobel Plastiques
Priority date: 2002-01-29
Filing date: 2003-01-22
Publication date: 2003-08-07
Also published as: FR2835305B1; FR2835305A1

Abstract

A pipe for pressurized automobile fluids, comprising an inner coat and an outer coat based on polyamide.

Description

Pipe for pressurized automotive fluids.

The present invention relates to a fluid transport pipe. This pipe can for example be installed in a clutch control circuit, a braking circuit, a power steering circuit, or a hydraulic transmission circuit of a motor vehicle. BACKGROUND] I INVENTION

Schematically, a hydraulic clutch control system generally comprises an actuating pedal, a transmitter of a control liquid connected to the actuation pedal, a receiver of the control liquid connected to the clutch itself. and a connecting line connected to the transmitter and the receiver for transporting the control liquid between them. An action on the pedal controls the displacement of a piston of the transmitter which pushes the liquid towards the receiver and causes the displacement of a piston of the receiver controlling the clutch.

The connecting line must meet a number of requirements to ensure proper operation of the clutch control. Thus, the pipe must keep a constant internal volume for temperatures between -40 ° C and 150 ° C and pressures between 10 bars and £ 40 bars so that a determined displacement of the pedal causes a corresponding displacement of the piston of the receiver substantially constant whatever these temperature and pressure conditions. Driving _. must also have a burst strength up to a pressure of the order of 200 bars at room temperature and retain flexibility up to a temperature of about -50 ° C. Among the other conditions that must be met by driving, waterproofing (to prevent water does not mix with the control liquid and lowers the boiling temperature), keeping it in occasional contact with fluids such as battery acid in the form of steam, oil, saline snow-clearing solutions ( such as zinc chloride), resistance to thermo-mechanical aging (caused by sudden pressure variations at different temperatures) are particularly important.

Currently, the pipes generally used are formed of a metal hose associated with a braided rubber hose. These pipes are, however, relatively expensive (in particular because of the assembly of the two elements constituting them, which also complicates the quality control operations of the pipe). In addition, the hose is permeable to water, which may lead to corrosion of the metal pipe. Finally, these pipes are relatively heavy, which goes against the trend currently taking place in the automotive sector aimed at reducing the weight of vehicles as much as possible.

Similar problems are encountered in the transmission oil cooling system. In vehicles fitted with an automatic gearbox, a transmission oil cooling circuit is provided in order to prevent frequent starting and / or changing of gears causing an increase in the temperature of the transmission oil which could cause damage to the gearbox. The cooling circuit includes an exchanger / - cooler device connected to the gearbox by conduits whose characteristics must enable them to withstand pressures above 20 bar at a temperature of the order of 140 ° C, maintain flexibility up to approx. - 40 ° C, withstand mechanical stresses such as vibrations, be impermeable to water and withstand occasional contact with fluids of the type mentioned above.

OBJECT OF THE INVENTION An object of the invention is to provide conduct which satisfies the aforementioned conditions and overcomes the above-mentioned drawbacks.

BRIEF DESCRIPTION OF THE INVENTION To this end there is provided according to the invention, a pipe for a motor fluid under pressure, the pipe comprising an inner layer and an outer layer, which are based on polyamide inner layer having ^a thickness between approximately 80% and 90% of the total thickness of the pipe.

Thus, the internal polyamide layer prevents deformation of the pipe under the effect of pressure and / or temperature and resists the transported fluid. This internal layer has a limited intake of water from the transported liquid and also gives the pipe good resistance to other mechanical stresses. Such a proportion of thickness gives the pipe optimum characteristics (mechanical resistance and chemical resistance, flexibility, impermeability, resistance to aging, etc.) for the applications envisaged. DETAILED DESCRIPTION

TWO EMBODIMENTS OF THE INVENTION According to a first embodiment, the pipe is of the bilayer type and comprises an inner layer based on polyamide covered with an outer layer also based on polyamide

According to a second embodiment, the pipe comprises an internal layer and an external layer based on polyamide, and an intermediate bonding layer. The intermediate bonding layer may be based on a polyethylene-maleic anhydride copolymer such as that of the company ATOFINA bearing the reference OREVAC.

In these two embodiments, the polyamide used for the production of the internal layer is advantageously a polyamide 6-6. This polyamide has relatively high mechanical properties, in particular at high temperature.

The function of the outer layer is to form a barrier layer, in particular to zinc chloride, and to protect the inner layer from contact with the fluids present in the external environment of the pipe.

(battery acid vapors, oil and other hydrocarbons, saline snow removal solutions ...).

The polyamide used for the outer layer is preferably a polyamide 12. The pipe is for example produced by coextrusion of the materials constituting the inner layer and the outer layer.

The driving carried out in accordance with the invention constitutes a satisfactory compromise between all the requirements mentioned above.

It also has good flexibility, facilitating its installation in the engine compartment and allowing freedom of travel during operation. For example, for an internal diameter between 3.5 mm and 4 mm, the pipe will have an external diameter between 7 and 8 mm.

Of course, the invention is not limited to the embodiments described and variants can be made without departing from the scope of the invention as defined by the claims.

In particular, other applications than those mentioned above ^• can be envisaged for driving the invention and in particular in the assistance circuit of the steering of a motor vehicle or in a hydraulic transmission circuit.

In addition, the numerical values mentioned are given for information only and the pipe can be sized differently for. meet specific conditions of use (for example depending on the quantity of fluid to be received, operating pressures, temperatures of use, etc.).

Claims

1. Pipe for pressurized automotive fluid, the pipe comprising an internal layer and an external layer which are based on polyamide, characterized in that the internal layer has a thickness comprised substantially between 80% and 90% of the total thickness of the driving .

2. Pipe according to claim 1, characterized in that it comprises an intermediate bonding layer.

3. Pipe according to claim .2, characterized in that the intermediate layer is based on a polyethylene maleic anhydride copolymer.

4. pipe according to any one of claims 1 to 3, characterized in that the outer layer is made of polyamide 12.

5. pipe according to any one of claims 1 to 4, characterized in that the inner layer is made of polyamide 6-6.