plastic pipe body

Abstract

Plastic pipe body (10) used for a cooling line of an electric vehicle and comprising a bellows section (12) on which a raised section (20) and a recessed section (22) are alternately provided in a longitudinal direction of the pipe, each extending circumferentially, wherein a radius of curvature Ra in the outer center of the depression section (22) is larger than a radius of curvature Rb in the inner center of the depression section (22) and a pipe thickness of the depression section (22) is greater compared to a pipe thickness of a boundary section (34) between the elevation section (20) and the depression section (22).

Description

Technical field

[0001] The present invention relates to a plastic tube body used in a cooling line of an electric vehicle and relates to a plastic tube body with a bellows section on which a raised section and a recessed section are alternately provided in a tube length direction. General state of the art

[0002] As specified, for example, in patent document 1 (JP 2022-135796 A), an electrically non-conductive plastic pipe is used as the tubular body in an electric vehicle, forming a flow channel for a cooling medium in the cooling system of a heat generator such as a battery or the like. In this document, the term "electric vehicle" refers to a self-driving vehicle with an electric motor as its drive system and includes, in addition to battery electric vehicles (BEVs), plug-in hybrid electric vehicles (PHEVs), hybrid electric vehicles (HEVs), and fuel cell electric vehicles (FCEVs).

[0003] However, in an electric vehicle, numerous devices such as the electric motor and the battery are arranged in confined spaces, and cooling lines must be installed in such a way that they run in the spaces between these devices.

[0004] To increase the degree of freedom during installation and simplify the work, it is conceivable to use a plastic pipe body with a bellows section as a cooling line. This section would have alternating raised and recessed sections along its length, each extending circumferentially. Since such a plastic pipe body can be curved by utilizing the expansion and contraction of the bellows section, its use as a cooling line allows for easy installation in confined spaces. State-of-the-art documents, patent documents

[0005] Patent Document 1: JP 2022-135796 A Brief description: Task of the invention

[0006] However, upon detailed examination of a plastic pipe body with a bellows section, including stress analysis and similar procedures using finite element methods, the inventor discovered that stress concentration at certain points can make it difficult to guarantee durability and reliability. For example, if the pressure of the cooling medium flowing through the pipe is increased to further enhance cooling capacity, the problem of local stress concentration is likely to be exacerbated.

[0007] Of course, it is possible to ensure durability and reliability with regard to this problem by increasing the thickness of the plastic pipe body, but solving the problem by thickening the plastic pipe body not only inevitably leads to an increase in costs and weight, but also increases the bending resistance at the bellows section, so that an impairment of the laying and installation work of the cooling line can hardly be avoided.

[0008] The present invention is therefore based on the objective of providing a plastic tube body with a bellows section which has novel shape-related features with which the pressure resistance performance can be increased while avoiding thickening of the tube body by reducing or eliminating local stress concentration on the bellows section. Means of solving the task

[0009] The following are some aspects of the present invention that achieve this objective. Design elements applied in the aspects listed below can, where possible, be used in any combination. It is understood that the aspects and technical features of the present invention are not limited to those listed below, but rather emerge from the inventive concept presented in the overall description and in the figures, or which is apparent to a person skilled in the art based on this information.

[0010] One aspect of the present invention is as follows. A plastic tube body used for a cooling line of an electric vehicle comprises a bellows section on which, in a longitudinal direction of the tube, a raised section and a recessed section are alternately provided, each extending circumferentially, wherein a radius of curvature Ra at the outer center of the recessed section is greater than a radius of curvature Rb at the inner center of the recessed section, and a tube thickness of the recessed section is greater compared to a tube thickness of a boundary section between the raised section and the recessed section.

[0011] The inventor's investigations have shown that, in a typical plastic pipe body, the pipe thickness of the recessed section is generally essentially constant throughout, with the radius of curvature of the inner surface of the recessed section being larger than the radius of curvature of the outer surface. It was found that, in a plastic pipe body with this typical structure, the stress occurring in the pipe wall, caused, among other things, by the internal pressure from the cooling medium, tends to concentrate approximately in the central part of the recessed section, which is the bottom of the bellows section.

[0012] However, because, according to the present aspect, the radius of curvature Ra of the outer surface of the plastic pipe body is greater than the radius of curvature Rb of the inner surface at the bottom of the recess, a greater pipe thickness is achieved in the middle of the recessed section than at the two side sections. It was found that in this way the stress arising at the bottom of the recess (middle of the recessed section) is distributed to both sides, resulting in an effective reduction of the stress.

[0013] Furthermore, in the plastic pipe body, according to the present aspect, the pipe thickness of the depression section is relatively larger across its entire length compared to the pipe thickness of the boundary section between the uplift section and the depression section. This makes it possible to extend the stress distribution at the bottom of the depression, which, as discussed above, is achieved by Ra > Rb, to a wider area of ​​the depression section, extending almost to the boundary between the uplift and depression sections.

[0014] According to the present invention, which provides a plastic pipe body with a bellows section having a novel shape-related feature of the recessed section, pressure resistance and durability can be improved by reducing the local stress concentration at the recessed section, while avoiding thickening of the pipe body. Therefore, a plastic pipe body for cooling an electric vehicle can be achieved that, for example, without a significant increase in cost or weight, ensures good deformation properties at the bellows section and ease of installation of the pipe, while also easily meeting the requirement for improved pressure resistance.

[0015] Advantageously, both the inner and outer surfaces of the bellows section of the plastic pipe body are formed along the pipe's length with a surface shape that has no corner sections and is either a continuous curved surface or extends smoothly by connecting a curved surface and a straight line. This also prevents deformation at the corner sections and abrupt changes or concentrations of stress.

[0016] A second aspect of the present invention is the plastic tube body of the first aspect, wherein the radius of curvature Ra in the outer surface center of the recessed section is infinite.

[0017] Since, in the present aspect, the radius of curvature Ra at the center of the outer surface of the depression section is infinite, a straight depression section surface is provided that extends by a fixed length lv (≠0) in the longitudinal direction of the pipe. In contrast, the radius of curvature Rb at the center of the inner surface of the depression section is not a straight curvature surface due to the condition Ra>Rb.

[0018] A third aspect of the present invention is the plastic tube body of the second aspect, wherein the straight recessed section surface, which extends by a length lv in the tube length direction since the radius of curvature Ra in the outer surface middle part of the recessed section is infinite, extends on the outer surface over a length of at least 10% of a distance La between inflection points on both sides, which lie at the boundary to raised sections adjacent to it on both sides in the tube length direction.

[0019] A fourth aspect of the present invention is the plastic pipe body of one of the aspects of the first to third, wherein, on a pipe thickness centerline connecting the center of the pipe thickness, with respect to a dimension between boundary sections, which is a distance in the pipe length direction between boundary sections, the inflection points corresponding to the boundary between adjacent in the pipe length direction of the raised sections and the recessed sections, a dimension Lv between boundary sections between which a recessed section lies is larger compared to a dimension Lm between boundary sections between which a raised section lies.

[0020] In the present aspect, the respective dimension between the boundary sections (Lm, Lv) from elevation section to elevation section and depression section to depression section on the pipe thickness centerline connecting element thickness centers is Lm. <Lv.

[0021] A fifth aspect of the present invention is the plastic tube body of one of the first to fourth aspects, wherein the tube thickness of the recessed section is at its maximum at the center of the outer surface and gradually decreases on both sides in the longitudinal direction of the tube.

[0022] A sixth aspect of the present invention is the plastic tube body of one of the first to fifth aspects, wherein a radius of curvature Rc in the outer surface center of the raised section is infinite.

[0023] By ensuring that the radius of curvature Rc in the outer surface center of the raised section is infinite in the plastic pipe body of the present aspect, a straight raised section surface is provided which extends by a fixed length lm (≠0) in the longitudinal direction of the pipe.

[0024] A seventh aspect of the present invention is the plastic tube body of the sixth aspect, wherein a radius of curvature Rd in the center of the inner surface of the raised section is a finite size.

[0025] An eighth aspect of the present invention is the plastic tube body of the sixth or seventh aspect, wherein the radius of curvature Ra at the outer center of the recessed section is infinite, providing a straight recessed section surface extending by the length lv in the longitudinal direction of the tube, wherein the length lv of the straight recessed section surface is defined in relation to the length lm of the straight raised section surface, which extends in the longitudinal direction of the tube since the radius of curvature Rc at the outer center of the raised section is infinite, such that it lies within a range of 100 to 140%.

[0026] A ninth aspect of the present invention is the plastic tube body of one of the first to eighth aspects, which has a straight tube section at a position in the longitudinal direction of the tube away from the bellows section, the straight tube section extending with a constant inner and outer diameter, wherein a minimum tube inner diameter at the recessed section is smaller than the tube inner diameter of the straight tube section.

[0027] A tenth aspect of the present invention is the plastic tube body of one of the first to ninth aspects, which has on both sides in the longitudinal direction of the bellows section a straight tube part extending with a constant inner and outer diameter, wherein the raised section is provided at connecting end sections to the straight tube parts on both sides in the longitudinal direction of the bellows section.

[0028] An eleventh aspect of the present invention is the plastic tube body of one of the first to tenth aspects, which has a straight tube section at a position in the longitudinal direction of the tube away from the bellows section, the straight tube section extending with a constant inner and outer diameter, wherein a tube thickness Tc of the bellows section with respect to a tube thickness Ts of the straight tube section over the entire bellows section satisfies 50 % ≤ Tc < 100 %.

[0029] In the case of the plastic pipe body of the present aspect, the pipe thickness Tc of the bellows section is therefore 0.5 Ts ≤ Tc <1.0 Ts in relation to the pipe thickness Ts of the straight pipe part.

[0030] A twelfth aspect of the present invention is the plastic tube body of one of the first to eleventh aspects, wherein at the tube thickness centerline connecting the center of the tube thickness, a minimum value of a radius of curvature rv on the depression section is greater than a minimum value of a radius of curvature rm on the elevation section. Effect of the invention

[0031] According to the present invention, it is possible to distribute the stress to both sides at the bottom of the depression, where it has been found that stress concentrations easily occur, and thus to achieve a reduction in the stress occurring, so that a plastic tube body for cooling an electric vehicle can be obtained which ensures good deformation properties and the like at the bellows section and at the same time also meets the requirement for an improvement in pressure resistance performance in a simple way. Brief description of the characters

[0032] They show: Fig. 1 an overview of an overall view of a plastic pipe body as an embodiment of the present invention; Fig. 2 a sectional view of the plastic pipe body enlarged at II-II Fig. 1; Fig. 3 an enlarged explanatory view of Section III from Fig. 2; Fig. 4 a stress distribution view when internal pressure acts on the plastic pipe body Fig. 3; and Fig. 5 A stress distribution view when internal pressure is applied, using a comparative example of the plastic pipe body. embodiment of the invention

[0033] In the following, an embodiment of the present invention is described with reference to the figures.

[0034] First, in Fig. Figure 1 shows a plastic pipe body 10 in a side view as an embodiment of the present invention. This plastic pipe body 10 is used as a conduit for a cooling device of an electric vehicle, for example as an element for forming a flow channel for a cooling medium in a battery cooling mechanism or the like.

[0035] The plastic tube body 10 has a bellows section 12 located at a longitudinally central point, with straight tube sections 14 and 14 integrally formed on both sides longitudinally of the bellows section 12, each extending with a constant inner and outer diameter. The diameter and length dimensions of the bellows section 12 and the straight tube sections 14 are not limited and can be suitably determined according to the performance required for the vehicle in the respective application, the flow channel shape, and the like. The bellows section 12, with the straight tube sections 14 between it, can be provided at several points longitudinally spaced from the plastic tube body 10.

[0036] The material of the plastic pipe body 10 is not restricted, and various plastic materials can be used, taking into account environmental conditions such as the cooling medium used, the temperature under operating conditions, and the like. For example, universal plastics such as polypropylene, polyamide, or the like can be used, or a vinyl alcohol plastic or the like such as EVOH, etc., can be used, with no restriction to a single-layer structure, but a structure with multiple laminated layers is also possible.

[0037] The structure of the bellows section 12 is such that raised sections 20 and recessed sections 22 with a constant cut surface shape in the circumferential direction are alternately and continuously provided along the longitudinal direction of the tube. The raised section 20 thus has a cut surface shape that is convex towards the side of the outer circumferential surface, and the recessed section 22 has a cut surface shape that is indented towards the side of the outer circumferential surface.

[0038] The raised section 20 and the recessed section 22 both lack any kink points on either an inner pipe surface 26 or an outer pipe surface 28 in the longitudinal pipe direction (left-right direction in the view). They therefore have a shape with curved surfaces that are connected by a single common tangent even at points with different angles of inclination and are smoothly continuous. In particular, in the present embodiment, they have a surface shape in which curves and straight lines are smoothly connected. Similarly, a pipe thickness centerline 30, which connects the center of the pipe thickness, has a smoothly continuous curvature without kink points along the entire length of the pipe, connecting the raised sections 20 and the recessed sections 22. In particular, in the present embodiment, it has a shape in which curves and straight lines are smoothly connected.

[0039] Furthermore, survey section 20 and in-depth section 22 have the following specific form.

[0040] (1) A radius of curvature Ra at the center of the outer surface of the depression section 22 is larger than a radius of curvature Rb at the center of the inner surface of the depression section 22. Therefore, Ra > Rb.

[0041] It is also provided that Ra and Rb, since they are the radii of curvature of the recessed section 22, have their center of curvature on the outside of the plastic tube body 10 (the side opposite a central axis 32) with respect to the recessed section 22, and in the direction that is curved towards the inside of the tube body, where the central axis 32 of the plastic tube body 10 is located (see Fig. 2) have a positive value and no negative value.

[0042] (2) The pipe thickness of the depression section 22 is greater than the pipe thickness of a boundary section 34 between the raised section 20 and the depression section 22. The pipe thickness of the depression section 22, which has a shape that curves towards the interior of the pipe body, is smallest at the two end sections of the depression section 22, which are the boundary sections 34, and is formed as a pipe thickness that is equal to or greater than that of the two end sections over the entire depression section 22.

[0043] The boundary section 34 can be objectively determined as an inflection point located between the raised section 20, which curves towards the outside of the pipe body, and the recessed section 22, which also curves towards the outside of the pipe body. The pipe thickness of the boundary section 34 is therefore the pipe thickness passing through the inflection point Bc on the pipe thickness centerline 30. The inflection point Bc can generally be understood as the midpoint on a straight line connecting an inflection point Ba on the outer surface 28 of the pipe and an inflection point Bb on the inner surface 26 of the pipe.

[0044] By combining the shape features of (1) and (2), strong stress, which easily arises at the bottom of the depression (middle part of the depression section 22), is distributed over a wide area on both sides, thereby reducing the stress that occurs, and by reducing the local stress concentration at the depression section 22, pressure resistance performance and durability performance can be improved while avoiding thickening of the plastic pipe body 10.

[0045] (3) The radius of curvature Ra at the center of the outer surface of the depression section 22 is infinite (∞). In this respect, a straight depression section surface 40 is provided at the center of the outer surface of the depression section 22, which extends with a fixed length lv (≠0) in the longitudinal direction of the tube (left-right direction). Fig. 3) extends. The radius of curvature Rb in the center of the inner surface of the depression section 22, in turn, is a non-straight curvature surface due to the condition Ra>Rb from (1) above.

[0046] By applying the shape feature of (3) to the outer center of the recess section 22, the straight recess section surface 40 can be provided, effectively increasing the pressure resistance of the recess section, and the design of the degree of change of the thickness of the middle part of the bottom section of the recess section 22 in the longitudinal direction of the pipe can be easily carried out by means of the radius of curvature Rb of the inner surface of the pipe 26.

[0047] (4) The straight depression section area with the length lv specified in (3) above extends on the outer surface of the pipe 28 over a length of at least 10% of a straight line La between the turning points Ba, Ba on both sides, which are located at the boundary to elevation sections 20, 20 adjacent to it on both sides in the longitudinal direction of the pipe.

[0048] The inflection point is a point where the center of curvature lies on the opposite side, i.e., a point where the sign of the second derivative changes in a function that describes the shape of the pipe's outer surface 28 in the pipe's longitudinal direction. If the boundary section between the raised section 20 and the recessed section 22 extends along a straight line formed by a linear function inclined with respect to the pipe's central axis 32, the midpoint of this line in the longitudinal direction is the inflection point.

[0049] By applying the shape feature of (4) the length of the straight surface of the depression section can be ensured, thereby achieving a further improvement of the increase effect for the pressure resistance of the depression section as per (3) above.

[0050] (5) With respect to a dimension between boundary sections of the uplift section 20 and the downlift section 22 at the pipe thickness centerline 30, a dimension Lv between boundary sections between which a downlift section 22 lies is larger than a dimension Lm between boundary sections between which an uplift section 20 lies. Therefore, Lm <Lv.

[0051] By applying the shape feature of (5), the dimensions between boundary sections (Lm, Lv) from raised section to raised section and from recessed section to recessed section at the pipe thickness centerline are 30 Lm. <Lv, wodurch auf vorteilhafte Weise die Abmessung des Vertiefungsabschnitts 22 in Rohrlängsrichtung gewährleistet werden kann. Die auftretende Spannung am Vertiefungsabschnitt 22, an dem es im Vergleich zum Erhebungsabschnitt 20 leicht zu einer starken Spannung kommt, kann daher auf einen breiteren Bereich in Rohrlängenrichtung verteilt werden, wodurch eine weitere Erhöhung der Haltbarkeit und dergleichen erzielt werden kann. Auch am Vertiefungsabschnitt 22, dessen Verformungssteifigkeit aufgrund seines geringen Durchmessers tendenziell hoch ist, können durch Vergrößern der Länge in Rohrlängenrichtung die Biegeeigenschaften und damit auch die Leichtigkeit der krümmenden Verformung verbessert werden.For the dimension between the boundary sections Ba, Ba on the outer surface 28 of the plastic pipe body 10, a dimension between boundary sections that lie on both sides of a raised section 20 with this in between, and a dimension between boundary sections that lie on both sides of a recessed section 22 with this in between, can be approximately equal.

[0052] (6) The pipe thickness Tv of the recessed section 22 is at its maximum at an outer surface center point Ps in the pipe axis direction and gradually decreases from the outer surface center point Ps to both sides in the longitudinal pipe direction. The pipe thickness Tv of the recessed section 22 is a pipe wall thickness dimension orthogonal to the pipe wall of the recessed section 22 and is generally a pipe wall thickness dimension orthogonal to the inner pipe surface 26 or the outer pipe surface 28.

[0053] By applying the shape feature of (6), a large tube thickness at the outer surface center point Ps can be ensured, where the stress is most easily concentrated at the recessed section 22, thus ensuring pressure resistance and durability performance in a more efficient manner. Gradually reducing the tube thickness of the recessed section 22 by continuously changing it from the outer surface center point Ps to both sides in the longitudinal direction of the tube prevents an excessive increase in the deformation stiffness of the recessed section 22 and also facilitates ensuring the curvature deformation performance at the bellows section 12.

[0054] (7) A radius of curvature Rc at the center of the outer surface 28 of the raised section 20 is infinite (∞). In this respect, a straight raised section surface 42 is provided at the center of the outer surface of the raised section 20, which extends with a fixed length lm (≠0) in the longitudinal direction of the pipe (left-right direction). Fig. 3) extends.

[0055] By applying the shape feature of (7), for example, by preventing local thinning of the middle part of the raised section 20, a stress concentration at the raised section can be avoided, and at the same time a further improvement of the curvature deformation properties at the raised section is also made possible.

[0056] (8) A radius of curvature Rd at the center of the inner surface of the raised section 20 is a finite quantity.

[0057] By applying the shape feature of (8), the thickness dimension of the raised section 20 can also be adjusted by the shape of the inner circumferential surface, thereby preventing, for example, excessive stiffening at the raised section 20 and thus enabling a further improvement in the curvature-deformation properties of the bellows section 12. In particular, by forming the inner surface of the raised section 20, which corresponds to the flat surface 42 on the outer surface, as a curved surface in the outer direction of the tube body, in combination with the aspect of (7) above, the tube thickness Tm of the raised section 20 is minimal at the center of the outer surface, at least in the part where the flat surface 42 is formed, and increases towards both sides in the longitudinal direction of the tube. This allows deformation and stress distribution to be achieved even in the middle part of the raised section 20.

[0058] It is also provided that Rc and Rd, since they are the radii of curvature of the raised section 20, have the center of curvature on the inside of the plastic pipe body 10 (the side on which the central axis 32 is located) with respect to the raised section 20, and have a positive value and no negative value in the direction that is curved towards the outside of the pipe body, opposite the side on which the central axis 32 of the plastic pipe body 10 is located.

[0059] (9) On the outer surface of the pipe of the raised section 20, the straight raised section surface 42 specified in (7) above is provided to a length lm, and at the outer surface center Ps of the depression section 22 the radius of curvature Ra is infinite, thereby providing the straight depression section surface 40 which extends by the length lv in the longitudinal direction of the pipe, wherein the length lv of the straight depression section surface 40 is specified in relation to the length lm of the straight raised section surface such that it lies within a range of 100 to 140%.

[0060] By applying the shape feature of (9), the length lm of the straight raised section surface 42 and the length lv of the straight recessed section surface 40 are formed such that they are relatively close to each other. As a result, the improvements in compressive strength and durability performance are jointly enhanced by the distribution of stress on the raised section 20 and the recessed section 22 and can unfold effectively, and at the same time an improvement in favorable curvature deformation properties and the like can be achieved.

[0061] (10) The internal diameter Ds of the straight pipe sections 14, whose positions extending in the pipe length direction away from the bellows section 12 have constant internal and external diameters, is small compared with the minimum value of the internal diameter Dc of the pipe at the bellows section 12, i.e. the minimum internal diameter of the pipe of the central part of the recess section 22.

[0062] By applying the shape feature of (10), it is also possible, for example, in the case where a straight tube with constant inner and outer diameters is used, which has been pre-formed by a known forming process such as extrusion or the like, and the bellows section 12 is formed by deforming a point of a fixed length in the tube's longitudinal direction by heat or the like, by making the smallest inner diameter of the recessed section 22 on the bellows section 12 smaller than the inner diameter Ds of the straight tube sections 14, to ensure a large tube thickness Tc of the recessed section 22. Since, as a result, the tube thickness of the recessed section 22, where stress concentrations easily occur, is ensured, a further improvement in pressure resistance and durability can also be achieved.

[0063] However, the forming process of the plastic pipe body 10 of the present invention is not limited. If, for example, a previously obtained straight pipe is formed by extrusion as described above, it is possible, immediately after extrusion forming of the straight pipe in a thermoplastic state, to make the outer forming tool, which surrounds the outer circumferential surface, ring-shaped and thereby continuously overlap it, to draw the outer circumferential surface of the straight pipe to the forming surface of this outer forming tool by means of a vacuum, and thereby transfer the bellows shape formed on the forming surface of the outer forming tool onto it in order to continuously form the desired bellows section 12 in the longitudinal direction of the pipe.

[0064] Advantageously, a straight tube is used which was extrusion-molded with the inner and outer diameter dimensions of the straight tube sections 14 of the plastic tube body 10, wherein an inner tube diameter Dc of the bellows section 12 is reduced at the recessed section 22 with respect to an inner tube diameter Ds of the straight tube sections 14 (Ds>Dc), while it is increased at the raised section 20 (Dc <Ds). Auch bezüglich der Rohrdicke der Umfangswand des Kunststoffrohrkörpers 10 wird die Rohrdicke Tc des Faltenbalgabschnitts 12 in Bezug auf die Rohrdicke Ts der geraden Rohrteile 14 an einem von dem Vertiefungsabschnitt 22 und dem Erhebungsabschnitt 20 gleich oder kleiner als Ts gestaltet (Tc≤Ts), und mehr bevorzugt wird die Rohrdicke Tc des Faltenbalgabschnitts 12 über die gesamte Länge mit Ausnahme der Verbindungspunkte zu den geraden Rohrteilen 14 an beiden Enden in Rohrlängsrichtung kleiner als die Rohrdicke Ts der geraden Rohrteile 14 gestaltet (Tc<Ts).

[0065] (11) The straight pipe sections 14, 14 are provided, each extending in the longitudinal direction on both sides of the bellows section 12 with a constant inner and outer diameter, wherein the raising section 20 is provided at connecting end sections to the straight pipe sections 14 on both sides in the longitudinal direction of the bellows section 12.

[0066] By applying the shape feature of (11), the stress concentration at the recessed section during the curving deformation of the bellows section 12, in adaptation to the pipe routing method in a vehicle, can be reduced more effectively. Specifically, when the bellows section 12 is curved according to the pipe routing space, a stress concentration easily occurs at the two end parts of the bellows section 12 in the longitudinal direction of the pipe, since the force opposing the deformation from the straight pipe sections 14, which have high deformation stiffness, acts upon them.By arranging the raised section 20 on these parts (the two end parts of the bellows section 12 in the longitudinal direction of the tube), which deforms more readily than the recessed section 22 and can more easily suppress the occurrence of stress, it is possible to improve the curvature performance of the bellows section 12 while reducing the stress occurring on the bellows section 12. By arranging the recessed section 22 in this way, avoiding the connecting end sections of the bellows section 12 to the straight tube parts 14, the stress occurring on the recessed section 22 due to the curvature can be reduced even more effectively, in conjunction with the stress distribution effect of the recessed section 22, due to the shape-related effect of the present invention described above.

[0067] (12) At a position in the longitudinal direction of the tube away from the bellows section 12, the straight tube sections 14 are located, which extend with a constant inner and outer diameter, wherein the tube thickness Tc of the bellows section 12, with respect to the tube thickness Ts of the straight tube sections 14, satisfies 50 % ≤ Tc < 100 % over the entire bellows section.

[0068] For the plastic tube body 10, to which the shape feature of (12) is applied, the following applies to the tube thickness Tc of the bellows section 12 with respect to the tube thickness Ts of the straight tube parts 14: 0.5 ≤ Tc < 1.0 Ts, so that, in conjunction with the stress distribution effect of the recessed section 22, the above-described shape-related effect of the present invention avoids thickening of the bellows section 12 and achieves good deformation properties, while at the same time the pressure resistance and durability of the bellows section 12 can be achieved even more effectively.

[0069] The position on the bellows section 12 where the pipe thickness Tc is smallest is preferably located in the central part of the raised section 20. The position on the bellows section 12 where the pipe thickness Tc is greatest is preferably located in the central part of the recessed section 22. In this way, it is even easier to achieve a balanced improvement in pressure resistance and durability performance in the recessed section 22, where stress concentration is more likely to occur, and to ensure the bending deformation properties of the raised section 20, where the problem of stress concentration is more easily avoided compared to the recessed section 22.

[0070] (13) At the pipe thickness centerline 30, which connects the center of the pipe thickness, a minimum value of a radius of curvature rv at the depression section 22 is greater than a minimum value of a radius of curvature rm at the elevation section 20.

[0071] In the case of the plastic pipe body 10 to which the shape feature of (13) is applied, the stress can be distributed more efficiently over a wide area at the depression section 22, where the problem of stress concentration is more likely to occur, and it is possible to prevent buckling deformation, while enabling a further improvement of the bending deformation properties at the elevation section 20.

[0072] A simulation result for the plastic pipe body 10, which has the shape features from (1) to (13) above and those in Fig. 1, Fig. 2 to Fig. The structure specified in section 3 according to the present embodiment, in order to determine the stress distribution that occurs due to the pressure action inside the pipe body, is shown as an exemplary embodiment in Fig. 4. A simulation result of the stress distribution under the same conditions for a plastic pipe body with a conventional structure without the shape features according to the present invention, as listed in (1) etc. above, is shown as a comparative example in Fig. 5. In both the exemplary embodiment and the comparative example, the material of the plastic pipe body is a single-layer structure made of polypropylene, and the simulation was carried out under atmospheric pressure and conditions of an internal pipe pressure of 120 kPa.

[0073] The simulation results from Fig. 4 and Fig. The 5 are difficult to discern because the originally colored view was converted into a binary black and white representation, but the areas with differences in shading, which are shown in the comparison example of Fig. 5 can be seen in the indentation sections, in the exemplary embodiment of Fig. 4 practically not detectable. According to specific calculation results, the maximum stress value occurring at the deepening section could not be determined compared to the reference example of Fig. 5 in the embodiment of Fig. 4 to 70% or less. This confirms that a stress distribution was achieved in the depression sections where stress concentration is particularly likely.

[0074] The foregoing discussion, based on the embodiment, has focused on specific preferred aspects of the present invention. However, the present invention is not to be interpreted as being limited to the specific details and aspects mentioned above. In particular, the shape features listed above in paragraphs (3) to (13) are advantageous for the present invention, but are not essential aspects; they can be applied optionally.

[0075] The specific lengths and thicknesses of the individual parts, including the distances between the raised sections 20 and recessed sections 22, and dimensions such as the radii of curvature on the bellows section 12, for example, can be designed appropriately, taking into account desired properties such as the pressure resistance performance and the curvature performance required of the plastic tube body 10, and also sizes such as inner and outer diameters, and are not restricted.

[0076] In the embodiment above, a raised section 20 is arranged at each of the end sections of the bellows section 12 in the direction of the pipe length, which are the connecting sections to the straight pipe parts 14, but a recessed section 22 can also be arranged at one or both end sections.

[0077] With regard to the pipe thickness Tc of the bellows section 12, the maximum thickness in relation to the minimum thickness is preferably in a range of at most 200%, and in general it is preferred if for a maximum value Tmmax of the pipe thickness Tm of the raised section 20 in relation to a minimum value Tvmin of the pipe thickness Tv of the recessed section 22 Tmmax ≤ 200 · Tvmin.

[0078] The straight survey section surface 42, which is defined at survey section 20, is not mandatory, and the pipe outer surface 28 of survey section 20 may have a curved shape over its entirety.

[0079] Although not listed in detail, the present invention can be implemented in embodiments in which the person skilled in the art makes various changes, corrections, improvements and the like by means of his or her knowledge, these embodiments of course also fall within the scope of the present invention, as long as they do not deviate from the essence of the present invention. Explanation of reference symbols 10 plastic pipe bodies 12 Bellows section 14 straight pipe section 20 Survey Section 22 In-depth section 26 pipe inner surface 28 pipe outer surface 30 Pipe thickness center line 32 Pipe center axis 34 Border section 40 straight depression section area 42 straight survey section area Ra radius of curvature of the outer surface center of the depression section Rb radius of curvature of the center of the inner surface of the elevation section Ba Inflection point of the pipe's outer surface Bb Inflection point of the pipe's inner surface BC Inflection point on the pipe thickness centerline La distance between adjacent Ba, Ba with the depression section in between Ps Outer surface center of the depression section TV pipe thickness of the depression section Tm pipe thickness of the survey section Ts pipe thickness of the straight pipe section (constant) Tc pipe thickness of the bellows section (Tv and Tm) lv Length of the straight depression section area in length of the straight survey section area The inner diameter of the straight pipe section DC inner diameter of the bellows section QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] JP 2022-135796 A [0002, 0005]

Claims

[1] Plastic pipe body (10) used for a cooling line of an electric vehicle and comprising a bellows section (12) on which a raised section (20) and a recessed section (22) are alternately provided in a longitudinal direction of the pipe, each extending circumferentially, wherein a radius of curvature Ra in the outer center of the depression section (22) is larger than a radius of curvature Rb in the inner center of the depression section (22) and a pipe thickness of the depression section (22) is greater compared to a pipe thickness of a boundary section (34) between the elevation section (20) and the depression section (22). [2] Plastic tube body (10) according to claim 1, wherein the radius of curvature Ra in the outer surface center of the recessed section (22) is infinite. [3] Plastic pipe body (10) according to claim 2, wherein a straight recessed section surface (40), which extends by a length lv in the longitudinal direction of the pipe, since the radius of curvature Ra in the outer surface central part of the recessed section (22) is infinite, extends on the outer surface over a length of at least 10% of a distance between turning points on both sides, which are located at the boundary to raised sections (20) adjacent to it on both sides in the longitudinal direction of the pipe. [4] Plastic pipe body according to one of claims 1 to 3, wherein on a pipe thickness centerline (30) connecting the center of the pipe thickness, with respect to a dimension between boundary sections, which is a distance in the longitudinal direction of the pipe between boundary sections, the inflection points which form a boundary between the raised sections (20) and the recessed sections (22) adjacent in the longitudinal direction of the pipe, a dimension Lv between boundary sections between which a recessed section (22) is located is larger compared to a dimension Lm between boundary sections between which a raised section (20) is located. [5] Plastic tube body (10) according to one of claims 1 to 4, wherein the tube thickness of the recessed section (22) is at its maximum at the center of the outer surface and gradually decreases on both sides in the longitudinal direction of the tube. [6] Plastic tube body (10) according to one of claims 1 to 5, wherein a radius of curvature Rc in the outer surface center of the raised section (20) is infinite. [7] Plastic tube body (10) according to claim 6, wherein a radius of curvature Rd in the inner surface center of the raised section (20) is a finite size. [8] Plastic pipe body (10) according to claim 6 or 7, wherein the radius of curvature Ra in the outer center of the recessed section (22) is infinite, providing a straight recessed section surface (40) extending by a length lv in the longitudinal direction of the pipe, wherein the length lv of the straight recessed section surface (40) is defined in relation to a length lm of a straight raised section surface (42), which extends in the longitudinal direction of the pipe since the radius of curvature Rc in the outer center of the raised section is infinite, such that it lies within a range of 100 to 140%. [9] Plastic tube body (10) according to one of claims 1 to 8, which has a straight tube section (14) at a position remote in the tube length direction from the bellows section (12), the straight tube section having a constant inner and outer diameter, wherein a minimum tube inner diameter at the recessed section (22) is smaller than the tube inner diameter of the straight tube section (14). [10] Plastic tube body (10) according to one of claims 1 to 9, which has on both sides in the longitudinal direction of the bellows section (12) a straight tube part (14) which extends with a constant inner and outer diameter, wherein the raised section (20) is provided at connecting end sections to the straight tube parts (14) on both sides in the longitudinal direction of the bellows section (12). [11] Plastic tube body (10) according to one of claims 1 to 10, which has a straight tube section (14) at a position remote in the tube length direction from the bellows section (12) and which extends with a constant inner and outer diameter, wherein a tube thickness Tc of the bellows section (12) with respect to a tube thickness Ts of the straight tube section (14) over the entire bellows section (12) satisfies 50 % ≤ Tc < 100 %. [12] Plastic pipe body (10) according to one of claims 1 to 11, wherein at the pipe thickness centerline (30) connecting the center of the pipe thickness, a minimum value of a radius of curvature rv at the depression section (22) is greater than a minimum value of a radius of curvature rm at the elevation section (20).

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