WO2021148989A1

WO2021148989A1 - Heat-resistant, multilayer fluid line

Info

Publication number: WO2021148989A1
Application number: PCT/IB2021/050476
Authority: WO
Inventors: Andre Häckel; Frank Fahrenholz; Martin SCHRAMOWSKI; Siegfried Arnold; Werner Zimmer
Original assignee: TI Automotive (Fuldabrück) GmbH
Priority date: 2020-01-22
Filing date: 2021-01-22
Publication date: 2021-07-29
Also published as: DE202020100325U1

Abstract

A fluid line, a system comprising the fluid line, and use of the fluid line provide a long-lasting fluid line that reduces production costs. The fluid line comprises a tube and at least one line connector at one end of the tube. An inner layer of the tube comprises a polyolefin, and an outer layer of the tube comprises a thermoplastic elastomer. The line connector comprises a plastic, wherein the line connector and the tube are welded to one another via at least one weld seam. The tube may also comprise a third layer, wherein the third layer is enclosed by the inner layer and comprises a thermoplastic elastomer.

Description

HEAT-RESISTANT. MULTILAYER FLUID LINE

RELATED APPLICATIONS

[0001] The present patent document claims the benefit of and priority to German Patent Application 202020100325.9, filed January 22, 2020, and entitled “Flame Retardant Cooling System” the entire contents of which are incorporated herein by reference.

FIELD

[0002] The disclosure relates to a fluid line comprising a tube and at least one line connector at one end of the tube, wherein an inner layer of the tube comprises a polyolefin, wherein an outer layer of the tube comprises a thermoplastic elastomer. The fluid line is particularly preferably used as a coolant line.

BACKGROUND

[0003] Such plastic tubes for coolants for internal combustion engines of motor vehicles are known from FR 2797673 B1. The fluid line disclosed there comprises an innermost layer made of a crosslinked polyethylene, a middle layer made of a polypropylene and an outermost layer made of a thermoplastic vulcanizate.

[0004] According to US 2009/0098325 A1, CN 206973135 U1 orCN 1062 87028 A, these coolant tubes are connected to a line connector which has a push-on mandrel for the tube. A fluid-tight press fit is created by plugging the slightly elastic plastic tube onto the mandrel of the line connector. It is also known to fasten the plastic tube to the line connector in a fluid-tight manner by means of a clamp that produces a press fit, which is described in US 2007/0035 123 A1 and in DE 102010 049 015 A1. [0005] The previously known connections between tube and line connector, however, weaken over the years, so that a not insignificant number of motor vehicles has to be serviced due to decreasing leak-tightness of the coolant lines.

SUMMARY

[0006] The present disclosure provides a longer-lasting fluid line. It is preferably an object of the disclosure to provide a long-lasting fluid line which reduces production costs, in particular the unit costs in production.

[0007] T o achieve the aforementioned object, the disclosure teaches a fluid line comprising a tube and at least one line connector at one end of the tube, wherein an inner layer of the tube comprises a polyolefin, wherein an outer layer of the tube comprises a thermoplastic elastomer, wherein the line connector comprises a plastic; and wherein the line connector and the tube are welded to one another via at least one weld seam.

[0008] In one form the inner layer and the outer layer contact each other. It is possible for a further layer to be arranged between the inner layer and the outer layer. The term “welding” preferably means that only energy has to be supplied in order to achieve a material bond. The expression “welding” preferably does not mean that additional mass, for example an adhesive and in particular a hotmelt adhesive, is or has been or has to be added in order to achieve a material bond.

[0009] The disclosure is based on the knowledge that the multi-year operation of a motor vehicle places very high demands on the connection between a line connector and a tube. The connections are often exposed to extreme weather conditions, as a result of which the plastic materials age and the original press fit increasingly loses its frictional connection. This is exacerbated by innumerable engine vibrations, which is why, as the motor vehicle ages, leaks and, as a result, undesirable maintenance measures can occur. The welding of the plastics of the line connector and tube, on the other hand, leads to a permanently fluid-tight connection, which achieves the task. [0010] According to a particularly exemplary embodiment, the plastic of the line connector comprises a polyolefin. It is possible that the plastic of the line connector comprises a polyamide. The polyolefin of the line connector is preferably a polypropylene and particularly preferably an isotactic polypropylene. The line connector advantageously has a reinforcing material, wherein the reinforcing material preferably consists of fibers and in particular of glass fibers.

[0011] In another form the tube has a third layer, wherein the third layer is enclosed by the inner layer and comprises a thermoplastic elastomer. The third layer is expediently also the innermost layer of the tube. The inner layer and the third layer advantageously touch one another. It is preferred that the innermost layer comprises an olefin. The olefin is advantageously part of the thermoplastic elastomer of the third layer. It is very preferred that the thermoplastic elastomer of the third layer is a thermoplastic elastomer based on olefin (thermoplastic polyolefin, TPO). According to a particularly exemplary embodiment, the thermoplastic elastomer of the third layer comprises an ethylene-propylene-diene monomer (EPDM). Particularly advantageously, the thermoplastic elastomer of the third layer comprises a polyolefin and preferably a polypropylene and particularly preferably an isotactic polypropylene. It is very particularly preferred that the thermoplastic elastomer of the third layer is a thermoplastic vulcanizate. It is very preferred that the thermoplastic vulcanizate of the third layer be Santoprene.

[0012] It can be advantageous if the outer layer comprises a polyolefin. The polyolefin of the outer layer is preferably a component of the thermoplastic elastomer of the outer layer. It is possible that the thermoplastic elastomer of the outer layer is a thermoplastic polyolefin (TPO). The thermoplastic elastomer of the outer layer preferably has an EPDM. Advantageously, the thermoplastic elastomer of the outer layer comprises a polyolefin and preferably a polypropylene and particularly preferably an isotactic polypropylene. According to a very particularly preferred embodiment, the thermoplastic elastomer of the outer layer is a thermoplastic vulcanizate which comprises the polyolefin of the outer layer. It is very preferred that the thermoplastic elastomer of the outer layer be Santoprene.

[0013] Preferably the polyolefin of the inner layer be a polypropylene. It is preferred that the polypropylene of the inner layer be an isotactic polypropylene. The polyolefin of the inner layer and the polyolefin of the outer layer are particularly preferably of the same type of polyolefin. The same type of polyolefin is, for example, when the inner layer comprises a first polypropylene and the outer layer comprises a second polypropylene. The same type of polyolefin is also present, for example, when the polyolefin of the inner layer is a first polyethylene and the polyolefin of the outer layer is a second polyethylene.

[0014] It can be advantageous if the inner layer and/or the line connector comprises a thermoplastic elastomer. The thermoplastic elastomer of the inner layer and/or the thermoplastic elastomer of the line connector is preferably an EPDM. The inner layer and/or the line connector very particularly preferably comprises a blend of a polyolefin or polypropylene and a thermoplastic elastomer or an EPDM. It is expedient that the proportion of the thermoplastic elastomer in the inner layer is at least 5 wt.-% or at least 10 or 15 or 20 or 30 or 40 or 50 wt.-%. The proportion of polyolefin or polypropylene in the inner layer or in the line connector is advantageously at least 20 or 30 or 40 or 50 or 60 or at least 70 or 80 wt.-%. [0015] Preferably the thermoplastic elastomer of the inner layer and the thermoplastic elastomer of the outer layer are of the same type of elastomer, for example the type of thermoplastic polyolefins (TPO) or the type of thermoplastic vulcanizates (TPV). The thermoplastic elastomer of the third layer or the thermoplastic elastomer of the line connector preferably is of the same type of elastomer as the thermoplastic elastomer of the first layer. [0016] According to an exemplary embodiment, the polyolefin of the inner layer and the polyolefin of the line connector are of the same polyolefin type, for example the polyolefin type polypropylene or the polyolefin type polyethylene. Preferably the polyolefin of the outer layer and/or the polyolefin of the third layer is of the same type of polyolefin as the polyolefin of the inner layer or the polyolefin of the line connector.

[0017] Preferably the at least one weld seam has been produced by rotational friction welding. The line connector expediently comprises a tube receptacle, which is preferably designed to be rotationally symmetrical. The tube is preferably connected to the tube receptacle via a plug connection. It is advantageous if the tube is inserted into the tube receptacle of the line connector. It is possible that the tube is slipped onto the tube receptacle of the line connector. It is particularly preferred that the tube is inserted into the tube holder and pushed onto the tube holder at the same time. The tube receptacle advantageously comprises an inner collar and/or an outer collar, wherein the tube is furthermore preferably slipped onto the inner collar and/or is inserted into the outer collar.

[0018] Preferably the tube receptacle has a contact surface for contacting the tube, which contact surface is conical. The term “conical” can be understood to mean a slightly curved surface which tapers or widens in a longitudinal section of the tube receptacle. The inner collar expediently comprises an outer, widening conical contact surface. It is possible for the outer collar to comprise a tapering conical contact surface on its inside.

[0019] The tube receptacle advantageously comprises a stop for the axial positioning of the tube. The conical contact surface of the inner collar and the conical contact surface of the outer collar preferably form a stop when the tube and the line connector are brought together. In the case of only an inner collar, the line connector in a foot section of the line connector has a preferably circumferential stop on the outside of the line connector. In the case of only one outer collar, the line connector in a foot section of the line connector has a preferably circumferential stop on the inside of the line connector. In the case of a tube receptacle with an inner collar and an outer collar, the tube and the line connector are preferably connected to one another via an inner weld seam and an outer weld seam.

[0020] According to one embodiment, the at least one weld seam is produced by laser welding. It is preferred that the tube is inserted into the line connector. The line connector advantageously contains a special color which makes the line connector appear black in the visible light spectrum, while the line connector is transparent in the near-infrared region of the light spectrum. The weld seam produced by laser welding has an extension in the axial direction of at most 5 mm, preferably of at most 4 mm, and particularly preferably of at most 3 mm.

[0021] It Preferably the tube or the outer layer or the inner layer or the third layer and/or the line connector has a flame retardant, so that there is flame protection that is qualified according to a standard. The qualification is preferably based on the UL94HB and/or UL94V standard. Qualification according to the UL94V standard is preferred. The tube or the outer layer or the inner layer or the third layer and/or the line connector preferably has a flame protection qualification of at least V-2, preferably of at least V-1 , and particularly preferably of V-0. The expression “qualified” means in particular the certification of a certain flame protection class or an experiment to be carried out according to a standard, within which a qualification can be determined. The flame retardant preferably comprises a copper stabilizer and is more preferably halogen-free.

[0022] The line connector is advantageously designed to be latched in order to be able to establish a reversibly releasable connection with a counterpart. The counterpart preferably comprises a plug shaft which can be plugged into the line connector. The counterpart may, for example, be connected to another tube or an assembly (tank, pump, etc.). It is particularly preferred that the line connector comprises a retainer, wherein the retainer is designed to latch the counterpart in the line connector. The retainer preferably comprises at least one latching element. The counterpart preferably comprises a latching means in order to latch in the line connector with the aid of the retainer. The latching means may be, for example, a circumferential collar or a circumferential groove. The retainer may, for example, be annular or U-shaped. It is preferred that the retainer is movably arranged on the line connector.

[0023] It is possible that the tube is designed as a smooth tube or a corrugated tube. The outside diameter of the tube is preferably at least 10/15/20/25 mm. The outer diameter of the tube is expediently at most 50/45/40 mm. The thickness of a wall of the tube is advantageously at least 0.5/0.75/1.0 mm. A thickness of the wall of the tube is preferably at most 4/3/2 mm. It is preferred that a thickness of the inner layer or the outer layer or the third layer is at least 0.1/0.2/0.3/0.4 mm. Expediently, a thickness of the inner layer or the outer layer or the third layer is at most 3/2/1.5/1.0 mm.

[0024] The present disclosure also teaches a system comprising a fluid line according to the disclosure, wherein the system comprises a cooler. It is preferred that the system comprises a pump and/or a thermostat and/or an expansion tank and/or a fan and/or a heater and/or a heat source. The heat source is preferably an internal combustion engine and/or a battery and/or a computer or an electronic system that requires cooling.

[0025] A first fluid line, the cooler, a second fluid line, and the heat source preferably form a cooling circuit. The cooler expediently comprises an inlet for warm coolant and an outlet for cold coolant. The heat source advantageously comprises an inlet for cold coolant and an outlet for warm coolant. It is preferred that the first fluid line is arranged between the outlet for warm coolant of the heat source and the inlet for warm coolant of the cooler. The second fluid line is advantageously connected between the outlet for cold coolant of the cooler and the inlet for cold coolant of the heat source.

[0026] According to one embodiment, the first fluid line comprises a third layer, wherein the third layer is enclosed by the inner layer and comprises a thermoplastic elastomer. The inner layer of the second fluid line is expediently the innermost layer. It is preferred that the system has a plurality of fluid lines, wherein a first group of fluid lines is assigned to a warm section of the cooling circuit and a second group of fluid lines is assigned to a cold section of the fluid circuit. It is preferred that the fluid lines of the warm section of the cooling circuit each have a third layer, wherein the third layer is enclosed by the inner layer and comprises a thermoplastic elastomer.

[0027] The present disclosure also teaches the use of the fluid line according to the disclosure as a coolant line, in particular as a coolant line for a water-glycol mixture.

[0028] We have discovered that welded connections are more stable or permanent, the more similar the plastics are that are welded to one another. Polyolefins and, in particular, polypropylene are preferably used as tube materials for the coolant lines to be resistant or hydrolysis-resistant and, moreover, comparatively cheap compared to the water-containing coolants (especially water-glycol mixtures).

[0029] Thermoplastic elastomers used as the outer layer offer good mechanical protection against vibration shocks in the engine compartment. In particular, thermoplastic elastomers containing an olefin are advantageous because they adhere particularly well to the polyolefin or polypropylene inner layer and are also relatively inexpensive. Thermoplastic vulcanizates which have polypropylene and EPDM and which, due to the polypropylene content, adhere very well to the polyolefin or polypropylene inner layer, are particularly preferred.

[0030] In addition, thermoplastic vulcanizates such as Santoprene have a very high level of heat resistance and, thanks to their good thermal insulation, also protect the inner layer. Thermoplastic elastomers based on olefin and also thermoplastic vulcanizates have, like polyolefins or polypropylene, good resistance to water and can therefore be used both as the third or innermost and also as the outermost layer. The polyolefin or polypropylene layer (inner layer) has in particular the function of the carrier layer and also of pressure resistance.

[0031] A third (innermost) layer, which comprises a thermoplastic elastomer/thermoplastic elastomer with an olefin/thermoplastic vulcanizate, is advantageous because this layer has to carry the coolant on the way to the cooler, which coolant is therefore hot. Thus, in particular the tubes or fluid lines of the return of the coolant circuit are also exposed to an input of heat from the inside. Due to the olefin or polyolefin content, the third layer adheres well to the inner layer, which means that delamination of the layers is practically impossible.

[0032] We have found it can also be advantageous if the inner layer or the line connector has a thermoplastic elastomer, we believe because this makes the inner layer or the line connector, which is quite brittle mainly because of the polyolefins or polypropylene, tougher and therefore less prone to breakage. If the line connector comprises a polyolefin or a polypropylene, this can be particularly well welded to the third layer or inner layer or outer layer in the case of an attached tube. In the case of an inserted tube, the line connector can be welded particularly well to the outer layer if this is a TPO or a TPV.

[0033] We have found that rotary friction welding provides an advantageous welding process because with this welded connection only the line connector has to be rotated around its own axis until the frictional heat leads to the weld. Laser welding is to be regarded as somewhat more complex, because for this purpose at least one of the two joining partners must be transparent for laser beams. At the same time, however, there is a requirement from the automobile manufacturers to design the fluid line in black, so that the joining partner receiving the other joining partner must contain an expensive special color that appears black in the visible spectrum and is transparent in the near-infrared spectrum. In addition, a laser welding device is more expensive, particularly because of the effort involved in positioning the laser beam.

[0034] It is particularly advantageous if a flame retardant is added to the tube or the outer/inner/third layer and/or the line connector. This advantage is particularly evident in electric vehicles which, compared to vehicles with internal combustion engines, do not tend to catch fire as often, but whose fires are often much more difficult to extinguish. In addition, the coolant lines in electric vehicles are attached directly to the batteries and thus to the sources of fire in order to cool them down, so that the flame retardant is particularly useful in coolant lines. This is because an ignited battery cell can ignite other battery cells more easily, the more the other battery cells are heated. For this reason, it is all the more helpful for the coolant line to withstand a particularly long period of time because it reduces the rate at which the fire can spread. [0035] The result is a permanently fluid-tight and permanently laminated coolant line which is inexpensive to manufacture and which in particular withstands the temperatures occurring in the engine compartment and of the coolant itself and which is ultimately particularly fire-resistant.

BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The present disclosure is explained in detail below on the basis of four embodiments. In a schematic representation,

[0037] Fig. 1 shows a cross section of a tube of the fluid line according to the present disclosure,

[0038] Fig. 2 shows a longitudinal section of the tube from Fig. 1, which is connected to a line connector,

[0039] Fig. 3 shows a front view of a retainer of the line connector from Fig.

2,

[0040] Fig. 4A shows a second embodiment of the connection between tube and line connector,

[0041] Fig. 4B shows a third embodiment of the connection between tube and line connector,

[0042] Fig. 4C shows a fourth embodiment of the connection between tube and line connector, and

[0043] Fig. 5 shows a system according to the disclosure comprising the fluid line according to Fig. 1 , 2 and 3 and further comprising further, essential components of a cooling circuit of a vehicle. DETAILED DESCRIPTION

[0044] In Fig. 1, 2 and 3, a first embodiment of a fluid line 1 according to the disclosure is shown, which comprises a tube 2 and a line connector 3 at both ends of the tube 2. According to the disclosure, the tube 2 has an inner layer 4 and an outer layer 5, wherein the inner layer 4 lies directly against the outer layer 5, see Fig. 1. The inner layer 4 has an isotactic polypropylene and an EPDM. The proportion of EPDM may be 20%, for example, while the proportion of polypropylene may be at least 70%. Furthermore, the inner layer 4 may also comprise at least one additive. The at least one additive of this embodiment is a halogen-free flame retardant comprising a copper stabilizer. The outer layer 5 comprises a thermoplastic elastomer in the form of the thermoplastic vulcanizate Santoprene. In addition, the outer layer 5 in this embodiment also has a flame retardant which comprises a halogen-free copper stabilizer. The tube 2 preferably complies with flame protection class V-0 of the UL 94 V standard.

[0045] According to a preferred embodiment, the tube 2 according to Fig.

I furthermore comprises a third layer 8 which is enclosed by the inner layer 4 and has a thermoplastic elastomer. The third layer 8 is preferably in direct contact with the inner layer 4. The thermoplastic elastomer of the third layer 8 is preferably Santoprene, wherein the inner layer 8 likewise has a flame retardant in the form of a halogen-free copper stabilizer.

[0046] With a view to Fig. 2, the line connector 3 comprises a coupling body

I I which is preferably integrally formed and which has a head section 14 and a foot section 15 axially opposite the head section 14. A tube receptacle 17 in which the tube 2 is received is assigned in particular to the foot section 15. For the sake of simplicity, the multi-layer tube 2 is only shown in one layer in Fig. 2. The tube receptacle 17 of this embodiment comprises an outer collar 20 and an inner collar 21, which run coaxially to the axis of the tube 2. The outer collar 20 and the inner collar 21 form a groove, the bottom of which represents a stop 13 for the tube 2.

[0047] The outer collar 20 of this embodiment is projected beyond the inner collar 21 in the axial direction towards the tube 2, which can be seen in Fig. 2. The inner collar 21 has a contact surface which is in contact with an inner surface of the tube 2. The contact surface of the inner collar 21 is essentially conical and widens in the axial direction towards the head part 14. The outer collar 20 has a contact surface which is in contact with an outer surface of the tube 2. The contact surface of the outer collar 20 is preferably conical and tapers in the axial direction towards the head part 14. Advantageously, the groove formed by the outer collar 20 and the inner collar 21 is slightly V- shaped, so that radially acting clamping forces which act on the inner surface and the outer surface of the end of the tube 2 increase in the axial direction towards the head part 14.

[0048] After the tube 2 has been pushed onto the inner collar 21 at least in sections for the purpose of positioning it relative to the line connector 3, the line connector 3 and the tube 2 are aligned essentially coaxially with one another. The line connector is then set in rotation via a rotary friction welding device (not shown) and at the same time an axially directed pressure is exerted on the tube 2 so that it strikes the stop 13 at the latest during the rotary movement of the line connector 3. The speed of rotation of the line connector 3 is expediently selected so that the contact surfaces of the outer collar 20 and the inner collar 21 as well as the associated sections of the inner surface and the outer surface of the tube 2 melt, so that the tube 2 and the line connector 3 are welded together after the friction surfaces have cooled down. Due to the presence of the inner collar 21 and outer collar 20, an outer weld seam 7 and an inner weld seam 18 are present after the friction welding process has been completed. [0049] The line connector 3 from Fig. 2 is used to quickly and reversibly connect the tube 2 either to another tube, not shown, or to an assembly (pump, tank, etc.), also not shown. For this purpose, the tube, etc., not shown, is connected to a counterpart 9 shown in Fig. 2, for example likewise by friction welding. According to Fig. 2, the counterpart 9 of this embodiment comprises a plug shaft 22 and a circumferential collar 23. For sealing against the counterpart 9, the line connector 3 comprises a sealing package 12 which is arranged in the coupling body 11 and in this embodiment has two sealing rings and a spacer arranged between them. The sealing package 12 is held captively in the coupling body 11 by a seal holder 19, in that the seal holder 19 latches into the coupling body 11 shortly before reaching the sealing package 12. In this exemplary embodiment, the seal holder 19 also serves as a stop for the circumferential collar 23 within the coupling body 11.

[0050] In Fig. 3, a retainer 16 is shown, which is still to be pushed into the head section 14 of the coupling body 11 from Fig. 2, coming from above. The retainer 16 of this embodiment is approximately U-shaped and has an actuating section 24 on the U-base and two legs 25. When the counterpart 9 is pushed into the coupling body 11 and the retainer 16 has already been introduced into the coupling body 11 (which is not shown in Fig. 2), the two legs 25 spread radially outward and then are restored to their original position after passing the circumferential collar 23 due to the restoring forces. The circumferential collar 23 is then located in the axial direction between the legs 25 and the seal holder 19 and is thus in a latched state. The retainer 16 preferably also comprises a release mechanism in order to release the locked state again. For this purpose, for example, the actuating section 24 can be pressed radially inward in order to spread the legs 25 apart. Alternatively, the legs 25 can be spread open manually. [0051] In Fig. 4A, a second embodiment of the connection between tube 2 and line connector 3 is shown. Accordingly, the tube receptacle 17 only comprises an outer collar 20 and a stop 13. The contact surface of the outer collar 20 is expediently designed conically and tapers in the axial direction towards the head section 14, not shown in Fig. 4A. In this way, only one weld seam 6 is produced.

[0052] A third embodiment of the connection between tube 2 and line connector 3 is shown in Fig. 4B. In this case, the tube receptacle 17 only has an inner collar 21 and a stop 13. The inner collar 21 has a contact surface which is in contact with an inner surface of the tube 2. The contact surface of this embodiment is slightly conical and widens in the axial direction towards the head section 14, not shown in Fig. 4B. Because of the only one contact surface of the connection in this embodiment, there is only one weld seam 6 which extends along the contact surface.

[0053] In the fourth embodiment according to Fig. 4C, the connection between the tube 2 and the line connector 3 was produced by means of laser welding. For this purpose, the tube receptacle 17 only comprises an outer collar 20 and a stop 13. The outer collar 20 has a contact surface which is in contact with an outer surface of the tube 2. The contact surface is essentially cylindrical. The inner edge of the outer collar 20 may be chamfered for the purpose of facilitating the introduction of the tube 2. In order to connect the tube 2 and the line connector 3 to one another, the tube 2 is inserted completely into the tube receptacle 17, which creates a press fit. A laser beam is then guided around the foot section 15 along a complete revolution, whereby a weld seam 6 is produced. The tube 2 is opaque to light rays in the near-infrared range, so that the laser beam is absorbed on the outside of the tube 2 and the plastic material there is melted by the tube 2 and the line connector 3. The line connector 3 of this embodiment is also kept black, although the black color is produced by a special dye. This is at least partially transparent in the near-infrared spectrum, so that the laser beam penetrates the outer collar 20 to the outside of the tube 2 without major heat losses. [0054] In Fig. 5, a system according to the disclosure with fluid lines 1a and 1b according to the disclosure is shown in simplified form as a block diagram. This system is a cooling circuit of a vehicle, wherein the system has a cooler 10 and a heat source 26. In the case of the cooler 10, it may be a cooler which can be additionally cooled by a fan 28. The heat source 26 can be both an internal combustion engine and a battery. The system also includes a heater 27 and an expansion tank 29. In addition, two pure Y-connectors 32 and a thermostat 30 and a pump 31 , each with three connections, are shown in Fig. 5. The connections may each be designed as counterparts 9, whereas the fluid lines 1a and 1b can each have a line connector 3 according to Fig. 2 on both sides.

[0055] The coolant of this system is first cooled in Fig. 5 in a downward direction by the cooler 10 and then conveyed along the fluid line 1b to the pump 31 and from there to the heat source 26. The coolant thus heats up on the way upward through or along the heat source 26 in Fig. 5 and exits there as warm or hot coolant. Part of the heated coolant can be used to operate the heater 27, while the remainder of the coolant flows in the direction of the thermostat 30. If the pressure within the system is too high, the thermostat 30 directs part of the hot coolant to the expansion tank 29. The arrow shown on the left-hand side in Fig. 5 and pointing upwards symbolizes that the temperature of the coolant or the corresponding components rises towards the top.

[0056] The fluid lines 1a and 1b can be divided into a first group of fluid lines 1a and a second group of fluid lines 1b. While the first group of fluid lines 1a is in particular also exposed to hot coolant, this does not apply to the fluid lines 1b, or to a significantly lesser extent. It is very preferred that the fluid lines 1a have the third layer 8, which contains Santoprene. In contrast, the fluid lines 1b do not have a third layer 8, so that the inner layer 4 in the case of the fluid line 1 b also forms the innermost layer.

Claims

Claims:

1. A fluid line comprising a tube and at least one line connector at one end of the tube wherein an inner layer of the tube comprises a polyolefin, wherein an outer layer of the tube comprises a thermoplastic elastomer, and wherein the line connector comprises a plastic, the line connector and the tube being welded to one another via at least one weld seam.

2. The fluid line according to claim 1 , wherein the plastic of the line connector comprises a polyolefin.

3. The fluid line according to claim 1, wherein the tube comprises a third layer, and wherein the third layer is enclosed by the inner layer and comprises a thermoplastic elastomer.

4. The fluid line according to claim 1, wherein the outer layer comprises a polyolefin.

5. The fluid line according to claim 1 , wherein the polyolefin of the inner layer and/or the outer layer is a polypropylene.

6. The fluid line according to claim 1, wherein the inner layer and/or the line connector comprises a thermoplastic elastomer.

7. The fluid line according to claim 6, wherein the thermoplastic elastomer of the inner layer and the thermoplastic elastomer of the outer layer are of the same type of elastomer.

8. The fluid line according to claim 7, wherein the thermoplastic elastomer of the inner layer and the outer layer are thermoplastic polyolefins (TPO) or thermoplastic vulcanizates (TPV). 2

9. The fluid line according to claim 1 , wherein the polyolefin of the inner layer and the polyolefin of the line connector belong to the same polyolefin type, the polyolefin type being polypropylene or polyethylene.

10. The fluid line according to claim 1, wherein the at least one weld seam is produced by rotational friction welding.

11. The fluid line according to claim 1 , wherein the at least one weld seam is produced by laser welding.

12. The fluid line according to claim 1, wherein the tube and/or the line connector has a flame retardant configured such that there is qualified flame protection according to a standard.

13. The fluid line according to claim 1 , wherein the line connector is configured to be latched and form a reversibly releasable connection with a counterpart

14. The fluid line according to claim 1, wherein the tube is designed as a smooth tube or as a corrugated tube.

15. A system comprising a fluid line according to claim 1, wherein the system further comprises a cooler.

16. Use of the fluid line according to claim 1 as a coolant line transmitting a water-glycol mixture.