Abstract:
To provide an assembly, comprising an exhaust gas turbocharger and an intercooler for an internal combustion engine and a hot-side charge-air line connecting the exhaust gas turbocharger to a charge-air inlet of the intercooler, which assembly allows the movements to be equalised between the exhaust gas turbocharger and the intercooler and is simple to produce and assemble, it is proposed that the hot-side charge-air line comprises a one-piece plastics material tube which is formed from a material containing polytetrafluoroethylene and/or modified polytetrafluoroethylene and has at least one flexible zone.

Description:
RELATED APPLICATION 
     This application is a continuation application of PCT/EP2007/009870 filed Nov. 15, 2007, the entire specification of which is incorporated herein by reference. 
    
    
     FIELD OF THE DISCLOSURE 
     The present invention relates to an assembly comprising an exhaust gas turbocharger and an intercooler for an internal combustion engine and a hot-side charge-air line connecting the exhaust gas turbocharger to a charge-air inlet of the intercooler. 
     Since the exhaust gas turbocharger, on the one hand, and the charge-air inlet of the intercooler on the other hand move relative to one another during operation of the internal combustion engine, the hot-side charge-air line must be flexible enough to be able to equalise the relative movements of its end on the turbocharger side and its end on the intercooler side. 
     BACKGROUND 
     Known assemblies of the aforementioned type are thus formed from metal tubes and flexible hoses of resilient material. However, charge-air lines composed in this way are complex to produce and assemble. 
     Plastics material tubes, as used for the cold-side charge-air line between a charge-air outlet of the intercooler and a charge-air inlet of the internal combustion engine do not withstand the high charge-air temperatures and charge-air pressures in the hot-side charge-air line. 
     SUMMARY OF THE INVENTION 
     The object of the present invention is to provide an assembly of the type mentioned at the outset which allows the movement to be equalised between the exhaust gas turbocharger and the intercooler and which is simple to produce and assemble. 
     This object is achieved according to the invention with an assembly having the features of the preamble of claim  1 , in that the hot-side charge-air line comprises a one-piece plastics material tube which is formed from a material containing polytetrafluoroethylene or a modified polytetrafluoroethylene and which has at least one flexible zone. 
     In this respect, the term a “modified polytetrafluoroethylene” is understood as meaning a polytetrafluoroethylene-like substance in which the molecular structure of the polytetrafluoroethylene (PTFE) has been chemically modified in that, in addition to tetrafluoroethylene, another likewise perfluorinated monomer is incorporated into the molecular chain so that some of the fluorine atoms of the PTFE have been replaced by substituents. 
     The chemical composition and preparation of “modified PTFE” is described, for example in EP 0 041 687 A1, EP 0 931 798 A1 or in U.S. Pat. No. 6,013,700. 
     The charge-air line formed as a one-piece plastics material tube from a material containing PTFE or modified PTFE is simple to produce, handle and assemble and has a high thermal resistance as well as a high dynamic mechanical strength, such that surprisingly, a charge-air line of this type is also able to cope with the high operating temperatures and operating pressures in a hot-side charge-air line. 
     The ends of the plastics material tube may be deformed plastically and/or elastically in order to connect said tube directly and in a fluid-tight manner to the adjoining units, i.e. to the exhaust gas turbocharger and the intercooler. 
     The material containing PTFE or modified PTFE of the one-piece plastics material tube is suitable for temperatures as low as −50° C. and for temperatures as high as approximately 300° C. and may be subjected to a high dynamic load. The resulting charge-air line has very good fatigue strength under reversed bending stresses and a high acoustic internal damping as well as a universal chemical resistance to blow-by gases and typical engine media, for example oils, greases, brake fluid and road salt. 
     Since the charge-air line according to the invention is formed from a one-piece plastics material tube, it may be produced simply, in a process-safe and cost-effective manner and may be handled easily during assembly. 
     To provide the desirable moulding flexibility of the flexible zone of the plastics material tube, it may be provided in particular that the flexible zone comprises a corrugated region, preferably a bellows arrangement. 
     The flexible zone is preferably arranged closer to the end on the intercooler side of the plastics material tube than to the end on the turbocharger side of the plastics material tube where the thermal stress on the charge-air line is greatest. The entire length of the plastics material tube of the assembly according to the invention may be flexible. 
     Alternatively, it may also be provided that the plastics material tube has at least one rigid zone, in addition to the at least one flexible zone. 
     The rigid, dimensionally stable zone of the plastics material tube may have at least one curved portion. 
     The plastics material tube used according to the invention as a charge-air line may basically be produced in any manner, for example in an injection moulding process. 
     However, the plastics material tube is preferably blow moulded. 
     The higher the selected forming temperature, the lower the memory effect of the moulded plastics material tube, i.e. the reforming tendency of the moulded plastics material tube when heated. 
     It is therefore particularly favourable if the plastics material tube is moulded at a temperature above the crystallite melting temperature of the starting material. 
     The plastics material tube may be formed, for example from pure polytetrafluoroethylene and/or modified polytetrafluoroethylene. 
     Alternatively, it may also be provided that the plastics material tube is formed from a polytetrafluoroethylene compound and/or a modified polytetrafluoroethylene compound, i.e. from a mixture of polytetrafluoroethylene or modified polytetrafluoroethylene and at least one organic or inorganic filler. 
     To render the plastics material tube black, it may be provided in particular that the polytetrafluoroethylene compound or the modified polytetrafluoroethylene compound contains a black pigment, preferably carbon black. 
     In order to form the hot-side charge-air line, the plastics material tube could basically be combined with another element conveying charge-air, for example with a metal tube. 
     However, in order to keep the number of components required for the inventive assembly as low as possible and thus to keep the production and assembly costs as low as possible, it is advantageous if the hot-side charge-air line does not comprise any other charge-air-conveying element, apart from the one-piece plastics material tube. 
     To increase the compressive strength and the mechanical stability of the charge-air line, provision may be made for at least one reinforcement ring to be arranged on the plastics material tube. 
     It is preferably provided that at least one reinforcement ring is arranged on the outside of the plastics material tube to prevent an undesirable expansion of the plastics material tube under the charge-air pressure to which the inside of the plastics material tube is subjected. 
     It is particularly effective if at least one reinforcement ring is arranged in the flexible zone of the plastics material tube. 
     In order to be able to easily handle the plastics material tube with the reinforcement ring arranged thereon as a unit, it is favourable for at least one reinforcement ring to be held in positive manner on the plastics material tube. 
     At least one reinforcement ring may be configured in one piece. 
     A one-piece reinforcement ring of this type is preferably joined with the plastics material tube as said tube is being moulded. 
     As an alternative, or additionally, it may also be provided that at least one reinforcement ring is configured in multiple parts. 
     Multipart reinforcement rings may be provided with, for example snap fits and applied subsequently to the ready moulded plastics material tube. 
     At least one reinforcement ring may comprise a metallic material, in particular a steel material and may preferably be completely formed of the metallic material. 
     Alternatively, it may also be provided that at least one reinforcement ring comprises a plastics material and is preferably formed completely of the plastics material. 
     Alternatively or additionally, it may also be provided that at least one reinforcement ring is formed of a fibrous material. 
     This fibrous material may comprise in particular organic, mineral and/or metallic fibres. 
     The at least one reinforcement ring is preferably braided, woven and/or spun from the fibrous material. 
     To be able to fix the charge-air line in a desired position, it is advantageous if at least one reinforcement ring is provided with an attachment element to secure the plastics material tube to an attachment point located outside the charge-air line. 
     An attachment point of this type may be arranged, for example, on a part of the bodywork or on a part of the internal combustion engine of a vehicle in which the assembly according to the invention is arranged. 
     The attachment element may comprise in particular a snap-fit element, a clamping element, a locking element, a threaded pin and/or a nut. 
     In order to be able to arrange at least one reinforcement ring on a portion of the plastics material tube having a non-rotationally symmetrical cross section, in particular having an oval cross section, it may be provided that at least one reinforcement ring has a non-rotationally symmetrical basic body, in particular an oval basic body. 
     The plastics material tube of the assembly according to the invention is preferably thermally stable at an operating temperature of at least 200° C., in particular at least 250° C. 
     Furthermore, it is advantageous if the plastics material tube of the assembly according to the invention is mechanically stable at an internal operating pressure of at least 2 bar, preferably at least 2.5 bar. 
     Further features and advantages of the invention are the subject of the following description and drawings of embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a schematic block diagram of an internal combustion engine with exhaust gas turbocharger and intercooler; 
         FIG. 2  shows a schematic longitudinal section through a plastics material tube which forms a hot-side charge-air line connecting the exhaust gas turbocharger to a charge-air inlet of the intercooler; 
         FIG. 3  shows a schematic cross section through the plastics material tube of  FIG. 2  along line  3 - 3  in  FIG. 2 ; 
         FIG. 4  shows a schematic longitudinal section through a two-part blow mould and a plastics material hose, inserted into the blow mould, prior to a blow moulding process, the blow mould being open; 
         FIG. 5  shows a schematic longitudinal section through the blow mould of  FIG. 4  with the inserted plastics material hose prior to a blow moulding process, the blow mould being closed; 
         FIG. 6  shows a schematic longitudinal section through the blow mould of  FIGS. 4 and 5  with the moulded plastics material tube after completion of the blow moulding process; 
         FIG. 7  shows a schematic longitudinal section through a second embodiment of a plastics material tube which forms the hot-side charge-air line and is provided with reinforcement rings; 
         FIG. 8  shows a schematic cross section through the plastics material tube of  FIG. 7  along line  8 - 8  in  FIG. 7 ; 
         FIG. 9  shows a schematic longitudinal section through a two-part blow mould with an inserted plastics material tube and inserted reinforcement rings prior to a blow moulding process, the blow mould being open; 
         FIG. 10  shows a schematic longitudinal section through the blow mould of  FIG. 9  with the inserted plastics material tube and the inserted reinforcement rings prior to the blow moulding process, the blow mould being closed; 
         FIG. 11  shows a schematic longitudinal section through the blow mould of  FIGS. 9 and 10  with the moulded plastics material tube and the reinforcement rings arranged thereon after completion of the blow moulding process; 
         FIG. 12  is a schematic perspective illustration of a reinforcement ring with a rotationally symmetrical basic body which is provided with an attachment element; and 
         FIG. 13  is a schematic perspective illustration of a reinforcement ring with an oval basic body which is provided with an attachment element. 
     
    
    
     Identical or functionally equivalent elements are designated by the same reference numerals in all the figures. 
     DETAILED DESCRIPTION OF THE INVENTION 
     An internal combustion engine designated overall by  100  in  FIG. 1  comprises a plurality of cylinders, for example four cylinders  102 , each of which is connected by an exhaust valve  104  to an exhaust gas duct  106  which leads to an exhaust gas inlet  108  of an exhaust gas turbocharger  110 . The exhaust gas coming from the internal combustion engine  100  drives a thrust wheel  112  on the exhaust gas side and then leaves the exhaust gas turbocharger  110  by way of an exhaust gas outlet  114  to which an exhaust gas line  116  is connected. 
     The thrust wheel  112  on the exhaust gas side drives a thrust wheel  118  on the charge-air side which compresses and accelerates air entering by way of an air inlet  120  from an intake air line  122  into the charge-air side of the exhaust gas turbocharger  110 . 
     The compressed charge-air passes through an air outlet duct  124  to a charge-air outlet  126 , provided with a rapid coupling connection, of the exhaust gas turbocharger  110 . 
     The charge-air outlet  126  is connected to a charge-air inlet  134 , provided with a rapid coupling connection, of an intercooler  136  by a hot-side charge-air line  132  provided at both ends in each case with a rapid coupling connection  128 ,  130 . 
     In the hot-side charge-air line  132 , the charge-air has a pressure in the region of, for example, approximately 2.5 bar to approximately 3 bar and a temperature in the region of approximately 200° C. to approximately 250° C. 
     The intercooler  136  is a heat exchanger in which the charge-air is cooled by cooling air coming from a radiator of the vehicle. 
     This cooling air enters the cooling air side of the intercooler  136  through a cooling air inlet  138 , absorbs heat from the charge-air and issues out of the intercooler  136  again through a cooling air outlet  140 . 
     The charge-air which has been cooled to a temperature of, for example, approximately 145° C. and has a pressure of, for example, approximately 1.5 bar leaves the charge-air side of the intercooler  136  through a charge-air outlet  142  which is provided with a rapid coupling connection and to which a cold-side charge-air line  148  is connected which is provided at both ends in each case with a rapid coupling connection  144 ,  146  and which connects the intercooler  136  to a charge-air inlet  150  of the internal combustion engine  100 , which charge-air inlet  150  is likewise connected to a rapid coupling connection. 
     Leading from the charge-air inlet  150  of the internal combustion engine  100  is a branching air feed duct  152  to intake valves  154  of the cylinders  102  of the internal combustion engine  100 . 
     The intercooler  136  is connected to the bodywork of the motor vehicle, whereas the internal combustion engine  100  and the exhaust gas turbocharger  110  arranged thereon are mounted in a manner uncoupled in terms of vibration from the bodywork. 
     The charge-air outlet  126  of the exhaust gas turbocharger  110 , on the one hand, and the charge-air inlet  134  of the intercooler  136 , on the other hand, therefore move relative to one another during operation of the internal combustion engine  100 , which is why the hot-side charge-air line  132  must be flexible enough to be able to equalise the relative movements of its end on the turbocharger side and its end on the intercooler side. 
     The exhaust gas turbocharger  110 , the intercooler  136  and the hot-side charge-air line  132  connecting the exhaust gas turbocharger  110  to the charge-air inlet  134  of the intercooler  136  thus form an assembly  156  which is able to vibrate. 
     The hot-side charge-air line  132  is formed by a one-piece plastics material tube  158  which is shown in detail in  FIGS. 2 and 3 . 
     The plastics material tube  158  has a rigid zone  160  facing the exhaust gas turbocharger  110  and a flexible zone  162  facing the intercooler  136 . 
     The flexible zone  162  comprises a bellows arrangement  164  with a plurality of annular folds, for example three annular folds  166 , which allow the flexible zone  162  to extend or compress along the longitudinal axis  168  of the tube and also allow said longitudinal axis  168  of the tube to tilt in the region of the flexible zone  162 . 
     The rigid zone  160  of the plastics material tube  158  is, on the other hand, substantially dimensionally stable. 
     The rigid zone  160  may have a curved portion  170 . 
     Furthermore, the rigid zone  160  may have a portion  172  arranged, for example, between the curved portion  170  and the flexible zone  162 , with an oval cross section (see  FIG. 3 ). 
     The plastics material tube  158  is substantially rotationally symmetrical with respect to the longitudinal axis  168  of the tube outside the portion  172  with an oval cross section and the curved portion  170 . 
     The plastics material tube  158  is formed in one piece from a material which contains PTFE or modified PTFE and is mechanically stable under the operating pressures prevailing in the hot-side charge-air line  132  of, for example, approximately 2.5 bar to approximately 3 bar and is thermally stable at the operating temperatures prevailing in the hot-side charge-air line  132  of approximately 200° C. to approximately 250° C. 
     The plastics material tube  158  is preferably formed from a PTFE compound or from a modified PTFE compound. 
     This PTFE compound or modified PTFE compound may contain a black pigment, preferably carbon black, in a quantity of up to 10% by weight to render the plastics material tube  158  black. 
     Both ends of the plastics material tube  158  are provided with a rapid coupling connection (not shown). 
     The plastics material tube  158  is preferably produced by a blow moulding process which is described in the following with reference to  FIGS. 4 to 6 . 
     For the blow moulding process, a multipart blow mould  174  is used which comprises an upper part  176  and a lower part  178 , the mutually facing insides  180 ,  182  of which are configured corresponding to the desired outer contour of the plastics material tube  158 , and also comprises two end-face connection pieces  184   a ,  184   b.    
     Upon opening the blow mould  174  (see  FIG. 4 ), a hose  186  consisting of the starting material containing PTFE or modified PTFE is introduced between the upper part  176  and the lower part  178  of the blow mould  174 . 
     The blow mould  174  is then closed (see  FIG. 5 ), the two ends of the hose  186  being pulled over a respective connection piece  184   a ,  184   b  and being clamped between the outside  188  of a respective connection piece  184   a ,  184   b  on the one hand and the inside  180  and  182  respectively of the upper part  176  and the lower part  178  respectively of the blow mould  174  on the other hand. 
     The blow mould  174  is then heated to a blowing temperature in the region of approximately 250° C. to approximately 400° C. by a heating device (not shown). 
     The higher the selected blowing temperature, the lower the memory effect of the moulded plastics material tube  158 , i.e. the reforming tendency of the moulded plastics material tube  158  when heated. 
     It is particularly favourable if the blow moulding is carried out at a temperature above the crystallite melting temperature of the starting material of the hose  186 . 
     When pure PTFE is used as the starting material, the crystallite melting temperature is approximately 327° C. 
     After reaching the desired blowing temperature, air or an inert gas is fed into the interior  192  of the hose  186  under a blowing pressure of, for example approximately 6 bar to approximately 50 bar through access ducts  190  in the connection pieces  184   a ,  184   b.    
     This charging of the interior  192  of the hose  186  with the elevated blowing pressure inflates the wall of the hose  186  and it is applied against the insides  180 ,  182  of the upper part  176  and the lower part  178  respectively of the blow mould  174  (see  FIG. 6 ), so that the desired contour of the plastics material tube  158  is produced. 
     The elevated blowing pressure in the interior  192  of the hose  186  or of the moulded plastics material tube  158  is maintained for a blowing period ranging from a few seconds to a few minutes. 
     The blow mould  174  is then cooled down to a temperature for removal from the mould in the region of approximately 100° C. to approximately 250° C. by disconnecting the heating device and optionally by an additional cooling operation. 
     After reaching the desired temperature for removal from the mould, the multipart blow mould  174  is opened and the moulded plastics material tube  158  is removed. 
     When the rapid coupling connections have been formed on the ends of the plastics material tube  158 , said tube  158  may be used as a hot-side charge-air line  132  in the assembly  156 . 
     A second embodiment, shown in  FIGS. 7 and 8 , of a one-piece plastics material tube  158  serving as a hot-side charge-air line  132  differs from the first embodiment shown in  FIGS. 2 and 3  in that, to increase the compressive strength and the mechanical stability, the plastics material tube  158  is provided with a plurality of reinforcement rings, for example four reinforcement rings  194 , in the region of the flexible zone  162 , which reinforcement rings  194  rest against the outside  196  of the plastics material tube  158  from the outside, in particular in the region between two folds  166  in each case. 
     These reinforcement rings  194  may be formed from a metallic material, for example a steel material, or from a plastics material which is sufficiently thermally and mechanically resistant. 
     Alternatively or additionally, it may also be provided in this respect that at least one reinforcement ring  194  is formed as a textile reinforcement ring, produced from a fibrous material. 
     This fibrous material may comprise organic, mineral and/or metallic fibres. The at least one reinforcement ring  194  may be braided, woven or spun from a fibrous material of this type. 
     The reinforcement rings  194  may be configured as a single piece or with multiple parts. 
     Multiple-part reinforcement rings  194  may be provided with, for example snap fits and applied subsequently to the ready moulded plastics material tube  158 . 
     One-piece reinforcement rings  194  may be joined to the plastics material tube  158  while the plastics material tube  158  is being moulded, as shown in  FIGS. 9 to 11 . 
     For this purpose, as may be seen from  FIG. 9 , when the multiple-part blow mould  174  is open, the reinforcement rings  194  are introduced together with the hose  186  of the starting material in the desired axial position between the upper part  176  and the lower part  178  of the blow mould  174 , the hose  186  of the starting material extending through the reinforcement rings  194 . 
     The blow mould  174  is then closed (see  FIG. 10 ), the reinforcement rings  194  being accommodated in annular grooves  198  provided for this purpose in the insides  180 ,  182  of the upper part  176  and respectively the lower part  178  of the blow mould  174 , such that during the blow moulding process, the reinforcement rings  194  retain their desired orientation relative to the longitudinal axis  168  of the tube and do not tilt. 
     After the blow mould  174  has been closed and heated to the blowing temperature, the blow moulding process is carried out, as in the first embodiment, by charging the interior  192  of the hose  186  with air under the blowing pressure or inert gas, as a result of which the plastics material tube  158  is formed into the desired contour (see  FIG. 11 ). 
     The reinforcement rings  194  are now joined in a positive manner with the plastics material tube  158 , such that the plastics material tube  158  may be handled and assembled with the reinforcement rings  194  as a unit. 
     When the blow mould  174  has cooled to the temperature for removal from the mould, it is opened and the plastics material tube  158  is removed with the reinforcement rings  194  arranged thereon. 
     Otherwise, the second embodiment shown in  FIGS. 7 to 11  of a plastics material tube  158  serving as a hot-side charge-air line  132  coincides with the first embodiment shown in  FIGS. 1 to 6  in respect of construction, function and method of production, reference being made to the above description of the first embodiment in this regard. 
     A third embodiment of a one-piece plastics material tube which serves as a hot-side charge-air line and of which one reinforcement ring  194  is shown in  FIG. 12 , differs from the second embodiment shown in  FIGS. 7 and 8  in that at least one of the reinforcement rings  194  is provided with at least one attachment element  200  used for attaching the plastics material tube  158  to an attachment point located outside the charge-air line  132 , for example to a part of the bodywork or to a part of the internal combustion engine  100 . 
     The attachment element  200  comprises a base  202  which is, for example substantially cylindrical and has a receiving groove for receiving part of an annular basic body  204  of the reinforcement ring  194 . 
     The base  202  is used for fixing the attachment element  200  to the basic body  204 . 
     In particular, it may be provided that the base  202  is fixed on the basic body  204  by welding, in particular by spot welding. 
     Furthermore, the attachment element  200  comprises a snap-fit part  206  which has a substantially U-shaped cross section and comprises two snap-fit tongues  208  and a web  210  joining the two snap-fit tongues  208  together. 
     The resilient snap-fit tongues  208  are provided to engage behind a respective projection on the attachment point located outside the charge-air line  132  and, by snapping in behind these projections, to fix in a detachable manner the reinforcement ring  194  and thus the plastics material tube  158 , on which the reinforcement ring  194  is arranged, on the attachment point. 
     As an alternative to the configuration as a snap-fit element, the attachment element  200  may also be configured as a clamping element, a locking element, a threaded pin or a nut. 
     Otherwise, the third embodiment shown in  FIG. 12  of a plastics material tube serving as a hot-side charge-air line coincides with the second embodiment shown in  FIGS. 7 to 11  in respect of construction, function and method of production, reference being made to the above description of the second embodiment in this regard. 
     A fourth embodiment of a plastics material tube which serves as a hot-side charge-air line and of which one reinforcement ring  194  is shown in  FIG. 13  differs from the third embodiment shown in  FIG. 12  in that the at least one reinforcement ring  194  provided with the attachment element  200  has a basic body  204  which is not substantially rotationally symmetrical, as is the case in the third embodiment, but instead has a non-rotationally symmetrical shape, in particular an oval shape. 
     Consequently, it is possible for this reinforcement ring  194  to be arranged on a portion of the plastics material tube  158  which has a non-rotationally symmetrical cross section, in particular an oval cross section. 
     Otherwise, the fourth embodiment shown in  FIG. 13  of a plastics material tube serving as a hot-side charge-air line coincides with the third embodiment shown in  FIG. 12  in respect of construction, function and method of production, reference being made to the above description of the third embodiment in this regard.