Fluid circulation pipe for motor vehicle, method for manufacturing same and use thereof as motor vehicle engine coolant hose

Abstract

A motor vehicle cooling fluid flow pipe, such as an engine cooling fluid pipe, characterized in that the wall of the pipe is constituted by a single layer made of a polymer material comprising a mixture of at least two polymer materials of different natures, one of which, referred to as a first material, being a polyolefin, and the other of which, referred to as a second material, being a thermoplastic polymer elastomer (TPE). The method of manufacturing this pipe comprises an operation of mixing at least the polyolefin and the thermoplastic polymer elastomer (TPE), a step of extruding said mixture in a screw extruder followed by a step of forming the pipe, the operation of mixing the polyolefin and the thermoplastic polymer elastomer (TPE) being performed upstream from the extruder or at its inlet.

Claims

1. A motor vehicle cooling fluid flow pipe, wherein the wall of the pipe is constituted by a single layer made of a polymer material comprising a mixture of at least two polymer materials of different natures, one of which, referred to as a first material, being a polyolefin, and the other of which, referred to as a second material, being a vulcanized polyolefin-based thermoplastic polymer elastomer (TPV), and in that the polymer material has a polyolefin content lying in the range 30% to 70% by weight.

2. The motor vehicle cooling fluid flow pipe according to claim 1, wherein the polymer material has a polyolefin content lying in the range 40% to 60% by weight.

3. The motor vehicle cooling fluid flow pipe according to claim 1, wherein the vulcanized polyolefin-based thermoplastic polymer elastomer (TPV) presents hardness on the Shore A scale lying in the range 30 to 70.

4. The motor vehicle cooling fluid flow pipe according to claim 1, wherein the vulcanized polyolefin-based thermoplastic polymer elastomer (TPV) presents hardness on the Shore A scale lying in the range 35 to 65.

5. The motor vehicle cooling fluid flow pipe according to claim 1, wherein the vulcanized polyolefin-based thermoplastic polymer elastomer (TPV) presents hardness on the Shore A scale lying in the range 40 to 65.

6. The motor vehicle cooling fluid flow pipe according to claim 1, wherein said first material is a polyolefin selected from polypropylene (PP), polyethylene (PE), high density polyethylene (HDPE), a cross-linked polyethylene (PEX), or a mixture thereof.

7. A method of manufacturing the motor vehicle cooling fluid flow pipe according to claim 1, comprising the steps of: an operation of mixing at least the polyolefin and the vulcanized polyolefin-based thermoplastic polymer elastomer (TPV), a step of extruding said mixture in a screw extruder followed by a step of forming the pipe, the operation of mixing the polyolefin and the vulcanized polyolefin-based thermoplastic polymer elastomer (TPV) being performed upstream from the extruder or at its inlet.

8. The method according to claim 7, wherein said mixture comprising the polyolefin and the vulcanized polyolefin-based thermoplastic polymer elastomer (TPV) is extruded at a temperature lying in the range 180° C. to 240° C.

9. The method according to claim 7, wherein said mixture comprising the polyolefin and the vulcanized polyolefin-based thermoplastic polymer elastomer (TPV) is extruded at a temperature lying in the range 200° C. to 220° C.

10. A cooling fluid pipe for a fuel-burning engine, an electric motor, an electrical converter, or a vehicle battery, wherein said cooling fluid pipe includes a fluid flow pipe according to claim 1.

11. The motor vehicle cooling fluid flow pipe according to claim 1, wherein said pipe is an engine cooling fluid pipe.

12. The motor vehicle cooling fluid flow pipe according to claim 6, wherein the polyolefin is a high density polyethylene (HDPE).

Description

BRIEF DESCRIPTION OF THE DRAWINGS:

(1) The sole FIGURE shows a motor vehicle cooling pipe in accordance with one embodiment.

DESCRIPTION OF THE INVENTION

(2) To this end, the present invention provides a motor vehicle cooling fluid flow pipe, such as an engine cooling fluid pipe, characterized in that the wall of the pipe is constituted by a single layer made of a polymer material comprising a mixture of at least two polymer materials of different natures, one of which, referred to as a first material, being a polyolefin, and the other of which, referred to as a second material, being a thermoplastic polymer elastomer (TPE). Advantageously, the wall of the pipe is constituted by a single layer made of a polymer material constituted exclusively of the mixture of said first material and of said second material.

(3) The term “pipe” is used below throughout the present text to designate any tube, tubing, hose, piping, and thus in particular engine cooling fluid pipes.

(4) Surprisingly, the inventors have been able to make a pipe having a single-layer wall that satisfies the criteria set out in the introduction by means of a mixture of polyolefin and of a thermoplastic polymer elastomer, whereas those two types of polymer are used in Document FR 2 797 673 to form outer layers of engine cooling fluid pipes, in association with other inner and/or intermediate layers. In that document, the layer made of polyolefin and of a thermoplastic polymer elastomer therefore does not come into contact with the glycol-based cooling fluid.

(5) Such a pipe having a single-layer wall is much easier to manufacture than are pipes having a multi-layer wall.

(6) Furthermore, the thickness of the single-layer wall is small, thereby making it easier to install the pipe in restricted spaces, such as battery packs or the engine compartments of present-day motor vehicles.

(7) In addition, such a pipe with a single-layer wall is easier to recycle.

(8) Advantageously, the polymer material of said pipe has a polyolefin content of at least 30% by weight, preferably at least 40% by weight.

(9) More particularly, the polymer material may have a polyolefin content lying in the range 30% to 70% by weight, preferably in the range 40% to 60% by weight. The proportions by weight within those ranges are selected in particular as a function of the mechanical strength desired for the pipe and its purpose.

(10) Outside those ranges, the properties of the pipe may be degraded: with less than 30% by weight, the performance, in particular in terms of the ability to withstand pressure, is degraded, and above 70% by weight, the material becomes too stiff, and thus more difficult to install in a vehicle, and the pipe transmits too much force to its interfaces.

(11) The thermoplastic polymer elastomer, which serves in particular to impart a degree of flexibility to said pipe, is preferably a polyolefin-based polymer elastomer, e.g. a vulcanized elastomer.

(12) Said polyolefin-based thermoplastic polymer elastomer advantageously presents hardness on the Shore A scale lying in the range 30 to 70, preferably in the range 35 to 65, more preferably in the range 40 to 65.

(13) Said first material is a polyolefin selected from polypropylene (PP), polyethylene (PE), preferably high density polyethylene (HDPE), a cross-linked polyethylene (PEX), or a mixture thereof.

(14) The present invention also provides a method of manufacturing a fluid flow pipe as described above. The method comprises an operation of mixing at least the polyolefin and the thermoplastic polymer elastomer (TPE), a step of extruding said mixture in a screw extruder followed by a step of forming the pipe, the operation of mixing the polyolefin and the thermoplastic polymer elastomer being performed upstream from the extruder or at its inlet.

(15) This is indeed a step of extruding the mixture of the two polymers, polyolefin and thermoplastic polymer elastomer, leading to a single-layer structure, and this is not co-extrusion of two polymers leading to a two-layer structure.

(16) The installation for performing this method thus comprises a feed hopper for each of the polymers, with a mixing zone upstream from the screw extruder or its inlet, or else a single feed hopper receiving the two polymers in the desired proportions (in the form of a premix).

(17) Said mixture comprising the polyolefin and the thermoplastic polymer elastomer is advantageously extruded at a temperature lying in the range 180° C. to 240° C., and preferably in the range 200° C. to 220° C. Such a temperature enables the two different materials to be made thoroughly homogenous in the cylinder of the extruder during the extrusion step.

(18) The forming is performed in a heating enclosure.

(19) The present invention also provides the use of said fluid flow pipe as described above, as a cooling fluid pipe, such as for a fuel-burning engine, an electric motor, an electrical converter, or a vehicle battery.

(20) Other features and advantages appear from the following description of a non-limiting embodiment of the invention.

EMBODIMENT OF METHOD OF MANUFACTURE

(21) An embodiment of a method of manufacture of a cooling fluid pipe for cooling an engine comprises: mixing, in proportions by weight 40/60, polypropylene (PP) and a vulcanized polyolefin-based thermoplastic polymer elastomer (thermoplastic vulcanizate (TPV)), e.g. having the trademark Santoprene® (marketed by the supplier ExxonMobile); using a screw to introduce said polymer mixture into an extruder; extruding said polymer mixture at a temperature lying in the range 200° C. to 220° C., leading to a tubular shape; thermoforming the extruded material in a hot air oven to give it its final shape, i.e. a tubular pipe 1 as shown in the sole FIGURE; then cooling; and optionally assembling connector elements.

(22) The tubular pipe 1 presents a single layer wall of thickness that may lie in the range 2 millimeters (mm) to 4 mm. This small thickness and its specific gravity close to 0.95 makes it possible, for equivalent mechanical properties, to reduce the weight of the pipe by about 40% compared with a pipe having the same mechanical performance and made of vulcanized rubber (having specific gravity that generally lies in the range 1.15 to 1.20) together with textile reinforcement, and having a thickness in the range 3 mm to 5 mm.

(23) The pipe 1 of the invention can withstand temperatures in the range −40° C. to 125° C., and simultaneously it can withstand pressures of about 1 bar to 4 bars relative.

(24) The presence of the thermoplastic polymer elastomer in the polymer material forming the wall of the pipe presents several advantages, including: damping vibration, while the engine is in operation and the vehicle is running; and greater flexibility: thus enabling ends of said pipe 1 to be fastened to connector endpieces, regardless of whether they are smooth or serrated, without requiring the use of an assembly system such as clamping collars. This simplifies assembly of the cooling pipe and makes assembly quicker, both during initial assembly and during replacement, if any.

(25) Furthermore, the single layer wall made of polypropylene (PP) and of vulcanized polyolefin-based thermoplastic polymer elastomer (TPV) is suitable for withstanding chemical attacks from the cooling fluid being transported, in particular when it contains glycol, and for withstanding high pressures and temperatures, in particular while the engine is in operation.