WO2009003858A1 - Plastic pipeline - Google Patents

Abstract

The present invention relates to a plastic pipeline (1) for media at risk of freezing, in particular for an aqueous urea solution for exhaust treatment in motor vehicles with internal combustion engines, comprising a pipeline wall (2) enclosing a flow channel (4). The pipeline wall (2) is shaped and formed, at least in at least one partial region of its length, in such a way that, in a pressureless state or under a predetermined operating pressure (p1) of the medium, the flow channel (4) has a first cross section (A1), deviating from the form of a circle, with a first circumference (U1), and under an increased pressure (p2), occurring due to a phase change when the respective medium freezes, the flow channel (4) has a second, increased cross section (A2), with a second circumference (U2), due to a reversible change in the cross-sectional shape, essentially without the material of the pipeline wall (2) expanding. In this case, the ratio (A1/A2) between the first cross section (A1) and the second cross section (A2) is less than one and the ratio (U1/U2) between the first circumference and the second circumference is at least approximately equal to one.

Description

 VOSS Automotive GmbH, Leiersmühle 2-6, 51688 Wipperfuerth

"Plastic pipe"

The present invention relates to a pipeline made of a relatively dimensionally stable plastic for gefriergefährdete media, in particular for a urea-water solution for exhaust aftertreatment, especially in diesel vehicles, with a at least one flow channel enclosing the pipe wall.

Due to the used, relatively strong and dimensionally stable plastic material of the conduit wall, this conduit is a conduit that is significantly more rigid and solid compared to flexible elastic hoses.

In motor vehicle technology, so-called SCR catalysts are used in some cases, especially in diesel engines (SCR = selective catalytic reduction), wherein an aqueous, z. B. 32.5% urea solution is used as NO _x reduction additive. It is a known problem that a urea-water solution due to a relatively high freezing point (about -11 ⁰ C) already tends to freezing at such ambient temperatures, which are not uncommon depending on the weather and geographic location. The same applies to water pipes for the windscreen washer system, unless sufficient antifreeze additive is used. Now it is well known that in the case of the freezing of liquids occurring phase change (change of state of matter from liquid to solid) usually comes to a volume expansion. In practice, damage and leaks often occur in the area of such pipelines.

EP 1 553 270 A1 also deals with the problem that, especially in SCR systems, difficulties have to be overcome because the volume increase occurring during freezing can lead to damage to components of the SCR device. For this purpose, in this known exhaust aftertreatment device at least one storage space in the form of an expansion space is provided, which is intended to allow a storage of volume upon reaching a freezing pressure of the medium, in particular by deforming an elastic expansion part. That elastic deformable stretch can be formed by a membrane that is to provide sufficient flexibility even with repeated freezing and thawing. However, the expansion space within the system is located only at a certain point. Therefore, it can still come in the line area for freezing with the corresponding consequences.

DE 10 2005 047 806 A1 describes a flexible hose line made of elastomeric material, which in particular should also be suitable for use in SCR systems. This known hose should have in its interior a displacement element. This displacement element should thus occupy the space which is otherwise flowed through by a core flow of the respective medium. As a result, the specific volume of the hose is reduced, even with lines that already have a technically minimal inside diameter. This is particularly advantageous for SCR systems because it seeks to minimize the unproductive passive volume in the line so that the increase in pressure throughout the system during freezing should have less impact on the other system components. Nevertheless, in spite of the reduced volume, volume increases of the medium and resulting expansion of the tube wall with the disadvantageous consequences already described above naturally occur, albeit relatively less.

The document FR 2 761 386 A1 describes a line for aqueous liquids, which should contain for freeze protection in combination electrical heating elements and elements of elastically compressible material.

GB 2 265 959 A describes a fuel line in which therefore - because of the very low freezing point of conventional fuels - the problem of anti-freeze does not actually. Thus, the document also deals with another problem, namely to avoid adverse effects, in particular acoustic noise, occurring in high-frequency pressure pulsations in the fuel line system. For this purpose, the known fuel line consists of an inner flexible plastic tube with non-circular cross-section and an outer envelope made of rubber or a rubber-like material. As a result, the fuel line has the ability to expand its internal volume to absorb pressure surges. The outer rubber layer is compressed, which absorbs energy and prevents the formation of noise. The document WO 00/16023 A1 describes a Gefherschutzeinhechtung for liquid lines, the line should contain an integrated compressible elastic material. The actual fluid channel is separated by a membrane of the compressible material. The pipe is enclosed on the outside by a rigid steel jacket. In a freeze-related volume expansion of the respective liquid in the fluid channel is compressed via the membrane, the integrated compressible material within the rigid shell.

GB 2 310 701 A describes a pipeline which has an expansion area for protection against freezing-induced bursting. At one or more points of the cable length an outer protective cover is provided, which consists of rubber or plastic and is elastically extensible. In this area, the line may have a perforated inner tube section, so that the liquid passes through the tube wall between the latter and the elastic protective sheath and the latter elastically expands during freezing.

Finally, DE 41 22 388 A1 relates to a pipe (hose or pipe) for fumigation or ventilation purposes, so that this document is not relevant in relation to the underlying problem here.

The present invention is based on the object to provide an improved pipeline, which is particularly suitable for gefriergefährdete media, while ensuring a high level of security against damage even after frequent freezing cycles.

This is achieved by the features of independent claim 1 according to the invention. Advantageous design features of the invention are the subject of the dependent claims.

According to the invention, it is accordingly provided that the conduit wall is shaped at least in one (at least one) subregion of its length and designed above all with respect to its material properties such that the flow conduit first deviates from the circular shape in a depressurized state or at a predetermined operating pressure of the medium Cross-section A1 with a first inner circumference U1 and at a by a phase change during freezing of the respective medium occurring, increased pressure of the medium by a in the Substantially without Matehaidehnung the line wall occurring, reversible change in cross-sectional shape has a second, enlarged cross-section A2 with a second inner circumference U2. Since according to the invention substantially no material expansion occurs (apart from a possible slight elastic - and therefore also reversible - elongation), the second circumference U2 of the enlarged cross-sectional shape (cross section A2) corresponds at least approximately to the first circumference U1 of the original, smaller cross-sectional shape (cross section A1 ). Therefore, the ratio between the first and the second extent is approximately equal to one (U1 / U2 «1). In any case, the ratio between the first and second cross section is less than one (A1 / A2 <1) due to the cross-sectional enlargement achieved in this case. Preferably, this ratio is in the range of 0.88 to 0.93. This means that when the transition between the first and the second cross-section within the flow channel a change in the cross-sectional size by up to 14% occurs. The design of this cross-sectional shape change preferably leads to a change in cross-section in the range of 7% to 12%, in particular 8% to 10%, so that the pipeline according to the invention is advantageously adapted to the volume change of an aqueous urea solution during freezing.

The invention is based on the recognition that it can be quite an order of 150 bar or more, depending on the nature of the components containing the medium when using conventional piping due to frequent freezing cycles due to a build-up in the system freezing pressure, and by resulting pressure-related Overstretching to successively increasing plastic (permanent) strain deformation of the pipe wall and thus thinning occurs, which leads to the destruction of the pipeline as a result.

In contrast, it is achieved by the inventive design that the pipe reversible cross-sectional and volume changes allowed, without causing irreversible, ie plastic material expansions occurs. With volume expansions of the medium, only the conduit wall is reshaped to increase the cross section. It also effectively plastic strains and thus thinning phenomena are effectively avoided. At most, it may - in addition to the cross-sectional change by changing the cross-sectional shape - to a slight elastic - and therefore also reversible - elongation of the pipe wall come. Advantageously, the Pipeline according to the invention this capability for cross-sectional and volume change over their entire or at least predominant length, so that in the installed state, the location of intensified within a vehicle gefriergefährdeten areas (eg., Siphon or Fahrtwindbereiche) is largely irrelevant.

The invention thus leads to the advantage that it is due to the ability of the pipeline to be able to increase their cross-section reversible, the Gefher phase change not only a steep increase in pressure on the otherwise very high freezing pressure, but rather follows the increase in pressure by the flexibility of Piping of a much flatter characteristic. This will be explained in more detail below with reference to a diagram.

On the basis of some illustrated in the drawings, preferred embodiments, the invention will now be explained in more detail. Showing:

1 shows a cross section of a first embodiment of a pipeline according to the invention in its initial or normal operating state,

2 shows a cross-section of the pipeline according to FIG. 1 in its state after a freeze-shaped cross-sectional enlargement, FIG.

Fig. 3 is a view similar to Fig. 1 in an embodiment with additional outer

Form elements,

Fig. 4 is a perspective view of a possible embodiment of

Mold elements according to FIG. 3,

Fig. 5 is a perspective view of a portion of an inventive

Piping with an alternative embodiment of external form elements,

Fig. 6 shows another embodiment of a pipe according to the invention in a cross section similar to Fig. 1 and Fig. 3 with an additional integrated electrical heating conductor and with additional dashed representation of the cross-sectional enlargement,

7 to 9 further embodiments of the pipe according to the invention again in cross-section or in axial end view, wherein in Fig. 7 also the enlarged in cross-section state is indicated by dashed lines,

10 is a diagram for further explanation of the operation of the pipeline according to the invention in contrast to known pipelines,

11 is a partially cutaway perspective view of a portion of a pipe according to the invention in an expedient embodiment and

Fig. 12 is a pipe according to FIG. 11 with an associated

Line connectors.

In the various figures of the drawing, like parts are always provided with the same reference numerals.

A pipe 1 according to the invention consists of a relatively stable, almost inelastic plastic, in particular of polyamide (PA), optionally with a certain proportion of fiber reinforcement. In the case of production of the pipe 1 by extrusion but is usually dispensed with a fiber reinforcement. In addition, an at least one side, preferably outside coating of polyurethane (PUR) may be provided (not shown). The pipeline 1 has a conduit wall 2, which encloses a flow channel 4 for a particular hydraulic flow medium, ie for a liquid. A preferred application of the pipeline 1 is the use in SCR catalyst systems to ammonia (NH ₃ ) or an aqueous urea solution (usually a 32.5% urea-water solution, also known under the registered trademark "AdBlue") , the composition is regulated in DIN 70070) to pass from a tank to the catalyst. 1 and 2, the conduit wall 2 according to the invention - at least in one (at least one) portion of the line length - shaped so that the flow channel 4 in a pressureless state or at a predetermined, relatively low operating pressure p1 of the medium a deviating from the circular shape first cross section A1 with an inner channel circumference U1 (see Fig. 1) and at an increased pressure p2 of the medium by a reversible, occurring substantially without material expansion of the conduit wall 2 change in cross-sectional shape a second, enlarged cross-section A2 having a circumference U2 (see Fig. 2). Here, the pipe 1 is designed with respect to the cross-sectional shapes so that the transition between the first cross section A1 shown in FIG. 1 and the second cross section A2 shown in FIG. 2 within the flow channel 4, a cross-sectional change up to 14% occurs. The same applies to the internal volume of the pipeline 1, because the volume of the product cross section times length results (V = AI). Preferably, the cross-sectional or volume change is in the range of 7% to 12%, and more preferably in the range of 8% to 10%. This preferred design is to adapt to the volume change upon freezing a common aqueous urea solution, such as "AdBlue".

The first cross section A1 is present at one or up to an operating pressure p1 in the range of 3 to 11 bar, in particular 4 to 6 bar. This corresponds to the operating pressure that occurs in normal operation in a urea line of an SCR system. Furthermore, the design is such that the second cross-section A2 is present at an elevated pressure p2, which is preferably significantly smaller than the otherwise, that is to say, lower than that otherwise present. H. without the invention, resulting freezing pressure of z. B. 150 bar.

The second, enlarged cross section A2 is substantially circular or at least approximated to the circular shape, because at a given circumferential length U1 or U2 of the conduit wall 2, the circular shape leads to the largest possible cross section and consequently the largest possible internal volume of the flow channel 4. Each deviating from the circular shape cross-sectional shape therefore has a smaller cross-sectional area. For this purpose, the first cross-section A1, for example, as shown in FIG. 1 and 3 oval or as shown in FIG. 6 is approximately polygonal, z. B. rectangular or square, be formed. As further illustrated by way of example in Fig. 7, the first cross section A1 may also have a crescent-shaped cross-sectional shape, which consists of an approximately circular inner surface of the conduit wall 2 and an approximately Ω-shaped inside protruding portion 2a of the conduit wall 2 results. The section 2a of the conduit wall 2 encloses a cavity 8 which is open towards the outside via a slot opening 6 and which is correspondingly reduced in size as the flow channel 4 enlarges from the first section A1 to the second section A2, namely only by a corresponding deformation of the wall section 2a without stretching (see the arrow 7 in Fig. 7). In this case, the slot opening 6 can widen with respect to its width (arrows 9).

In the further exemplary embodiment according to FIG. 8, the first cross section A1 is kidney-shaped. It is obvious how this is a deformation to increase the cross section of the second cross section A2.

In the embodiments according to FIGS. 1 and 2 and FIGS. 6 to 9, the conduit wall 2 (2 a) is preformed essentially with the first cross section A 1 of the flow channel 4, so that the pipeline 1 automatically assumes its shape in the unpressurised state or at the operating pressure p 1 assumes the first cross-section A1.

As is illustrated with reference to FIGS. 3 to 5, the conduit wall 2 can also be preformed substantially with the second cross-section A2 of the flow channel 4 and thereby be equipped with additional elastic molded elements (shaped springs) 10, for the unpressurized state or for the operating pressure p1 Forcibly deform the conduit wall 2 into the first cross section A1, so that the transfer from the first cross section A1 to the second cross section A2 with elastic deformation of the form elements 10 and the return transfer from the second cross section A2 into the first cross section A1 is effected by the spring elasticity of the form elements 10. According to FIG. 3, the shaped elements 10 may be individual, approximately U-shaped spring clips 12, which press the conduit wall 2 into a flat-oval shape. The spring clips 12 can be distributed over the length of the pipe 1. According to FIG. 4, the spring clips 12 can also be connected via connecting webs 14. In the further embodiment according to FIG. 5, a shaped element 10 is provided in the manner of a flat helical spring, which encloses the conduit wall 2 helically.

In an advantageous embodiment of the invention, the pipeline 1 may comprise at least one electrical heating conductor 16 for heating the respective medium located within the flow channel 4. According to Fig. 6, the heating conductor 16 - possibly with an additional electrical insulation 18 - extend within the flow channel 4. According to FIG. 8, the heating conductor 16 is arranged directly outside the pipeline 2 on the conduit wall 2, specifically in a correspondingly shaped receiving region which at the same time also forms the kidney shape of the flow channel 4.

In the embodiment of FIG. 7, an unillustrated heating element can be accommodated within the cavity 8.

In the embodiment according to FIG. 9, the conduit wall 2 is surrounded on the outside by additional chambers 17. In the example shown, a cylindrical, circular in cross-section outer jacket 18 is connected via connecting webs 20 with the conduit wall 2. In addition, can be formed by integrally formed webs 22 chambers 24, which can be used to hold heating conductors. The chambers 17, 24 formed between the conduit wall 2 and the outer jacket 18 cause a good thermal insulation.

At this point, the operation of the invention will be explained in more detail with reference to the diagram in Fig. 10, namely on the basis of a pipe according to the invention 1 (profile 1) over a conventional pipe I (profile I). The profile I of the conventional pipeline is already at operating pressure pl circular with an inner diameter dl, a circumference UI and a cross section AI. In this example, the profile 1 of the pipeline 1 according to the invention is oval at the operating pressure p1 = pl so that there is no true diameter but a "mean diameter dm1." The profile 1 has a circumference U1 and a cross section A1 at operating pressure p1 For comparison reasons, it is assumed that the cross-sections of both profiles in this state are approximately equal (AI «A1) .From this it follows that in this initial state the circumference U1 of the profile 1 according to the invention is greater than the circumference UI.

The diagram now shows a characteristic for both profiles in the event that a contained medium freezes and thereby expands its volume, which causes a corresponding increase in the respective cross-section A. The profile I is stretched immediately, so that the characteristic increases quite steeply up to an elevated pressure (freezing pressure) pH. The volume increase of the medium then has a Elongation of the line I to the diameter dll, the circumference Uli and the cross section All effected, where Uli> UI.

In contrast, the pipeline 1 according to the invention initially undergoes no expansion in the freeze-related increase in volume of the medium, but only a change in the shape of the profile. This results in a good compliance and consequently a much flatter characteristic. The required for the same increase in volume cross-section A2 = All is therefore already achieved at a much lower pressure p1, d. H. The freezing pressure in the system is significantly lower than when using the conventional pipeline (profile I).

In addition, the pipe 1 according to the invention allows even a further increase of the cross section to A3 and more, up to a point in which the cross section reaches the circular shape (maximum cross section at a given circumference). From this point, which is marked with X in the diagram, the line wall would have to stretch for a wider cross-sectional enlargement as well as in the conventional pipeline, so that the curves would then run approximately parallel with substantially the same slope, as in the upper part of the curves is indicated.

According to the invention, however, a design can also be provided such that the pipeline 1 has a profile deviating from the circular shape at operating pressure p1, but initially a deformation to a circular shape occurs due to the pressure rise on p2 and then a slight expansion is tolerated. It is thus practically a "mixed form" of the profiles of FIG. 10, but in any case a significantly reduced elongation compared to the profile I is achieved.

As far as the embodiment illustrated in FIGS. 11 and 12 is concerned, the pipeline 1 has a circular cross-section in the region of at least one end section to form a connection section 30. This connecting section 30, which is circular in cross-section, passes over a transition section 32, in particular continuously, avoiding steps, into a line section 34 with the cross section deviating from the circular shape according to the invention. As can be seen from FIG. 11, the cross-section of the line section 34 deviating from the circular shape can be, for example, an oval cross-sectional shape. According to FIG. 12, the pipeline 1 is preferably in the region of both end sections similar connection portions 30 with a circular cross-section of the conduit wall 2 present. This embodiment simplifies the connection of the pipeline 1 to a line connector 36. FIG. 12 shows, by way of example, the line connector 36 in the form of an angle connector. This line connector 36 has a connection section 38 for the pipeline 1, wherein the connection section 38 has a receptacle 40 with a circular inner cross section, which is adapted to the circular outer cross section of the connection section 30. Appropriately, the connection portion 30 in the receptacle 40 cohesively, in particular by laser welding, are attached.

The invention is not limited to the illustrated and described embodiments, but also includes all the same in the context of the invention embodiments. Furthermore, the invention has hitherto not been limited to the combination of features defined in the respective independent claim, but may also be defined by any other combination of specific features of all individually disclosed individual features. This means that in principle virtually every individual feature of the respective independent claim can be omitted or replaced by at least one individual feature disclosed elsewhere in the application. In this respect, the claims are to be understood merely as a first formulation attempt for an invention.

Claims

claims 1. Piping (1) made of plastic for gefriergefährdete media, in particular for an aqueous urea solution for exhaust gas aftertreatment in motor vehicles with internal combustion engines, with a flow channel (4) enclosing the conduit wall (2), dad u rch ge ken nze I n et in that the conduit wall (2) is shaped and formed at least in at least part of its length in such a way that the flow channel (4) has a first cross-section (A1) deviating from the circular shape in a pressureless state or at a predetermined operating pressure (p1) of the medium ) with a first circumference (U1) and with a by a phase change during freezing of the respective medium occurring, increased pressure (p2) by a reversible change in the cross-sectional shape substantially without material expansion of the conduit wall (2) has a second, enlarged cross-section (A2) a second circumference (U2), wherein the ratio (A1 / A2) between the first and the second Q section (A1, A2) is less than one and the ratio (U1 / U2) between the first and the second circumference is at least approximately equal to one. 2. Pipe according to claim 1, characterized by a design such that at the transition between the first cross section (A1) and the second cross section (A2) a cross-sectional change of up to 14% and in particular in the range of 7% to 10% occurs, correspondingly an aspect ratio (A1 / A2) in the range of 0.88 to 0.93. 3. Pipe according to claim 1 or 2, characterized in that the first cross section (A1) at or to an operating pressure (p1) in the range of 3 to 11 bar, in particular 4 to 6 bar, is present. 4. Pipe according to one of claims 1 to 3, ad d e r e c e c e n e c e s n e, s e s the second, enlarged cross-section (A2) is substantially circular or approximated to the circular shape. 5. Pipe according to one of claims 1 to 4, dadu rch I gekennze I n et that the conduit wall (2) is preformed substantially with the first cross section (A1) of the flow channel (4). 6. Pipe according to one of claims 1 to 5, dadu rch I gekennze I n et that the conduit wall (2) substantially preformed with the second cross section (A2) of the flow channel (4) and with additional elastic form elements (10) in the first Cross section (A1) is forcibly deformed. 7. Pipe according to one of claims 1 to 6, characterized in that the first cross section (A1) is oval, partially circular, approximately polygonal, kidney-shaped or sickle-shaped. 8. Pipe according to one of claims 1 to 7, I ge nze at least one electric heating conductor (16) for heating the respective, within the flow channel (4) located medium. 9. Pipe according to claim 8, dadu rch I gekennze n et et that the heating conductor (16) within the flow channel (4). 10. Pipe according to claim 8, dadu rch in that the heating conductor (16) outside of the flow channel (4) in particular in an integrally formed chamber (24) on the conduit wall (2) is arranged. 11. Pipe according to one of claims 1 to 10, characterized in that the conduit wall (2) outside of additional chambers (17) is enclosed. 12. Pipe according to one of claims 1 to 9, characterized in that the conduit wall (2) consists of PA and possibly - in particular on the outside - is coated with PUR. 13. Pipe according to one of claims 1 to 12, dadu rch I gekennze I n et that the conduit wall (2) in the region of at least one end portion to form a connecting portion (30) is formed with a circular cross-section, wherein the connecting portion (30) via a transition section (32) in particular continuously in a line section (34) merges with deviating from the circular cross-section. 14. Pipe according to claim 13, wherein, in the region of both end sections, connecting sections (30) with a circular cross section are present.