MOUNTING NUT AND INTERNAL COMBUSTION ENGINE WITH MOUNTING NUT

Description

[0001] The invention relates to a fastening arrangement according to claim 1 for securing an exhaust manifold to a cylinder head of an internal combustion engine by screwing in an axial fixing direction (by rotating the fastening nut in a circumferential direction) with an externally threaded bolt (stud bolt) held on the cylinder head and passing through a through opening in the exhaust manifold, wherein the fastening nut comprises an internally threaded section for screwing to the externally threaded bolt and preferably braking torque means for increasing the release torque, further comprising a support surface for preferably indirect or alternatively direct axial support on the exhaust manifold, wherein the support surface is formed on a radially projecting spring section of the fastening nut which can be elastically prestressed in the axial direction.

[0002] In known internal combustion engines, the exhaust manifold is fixed to the cylinder head by means of several threaded bolt / fastening nut combinations, with the threaded bolts each penetrating a through-hole in the exhaust manifold, and the nuts screwed to the threaded bolts clamping the exhaust manifold between a lower end face of the nut and the cylinder head. In practice, the problem arises that the exhaust manifold tends to slide due to the temperature fluctuations that occur during operation, particularly during the start-up phase of an internal combustion engine. This means that the exhaust manifold moves parallel to the cylinder head surface, with a bending moment being exerted on the threaded bolt via the manifold plate and / or the nuts that rest exclusively on the exhaust manifold.It's also possible that the nuts on the threaded bolts may partially loosen due to the numerous load cycles, causing the bolt force to drop below a specified minimum value of, for example, 3 kN. This can lead to leaks, allowing hot exhaust gas to escape into the engine compartment and / or external air to be drawn into the exhaust system.

[0003] DE 199 20 822 A1 discloses an internal combustion engine in which the manifold is fixed to the cylinder head by means of a nut that is axially supported on a spacer sleeve that passes through a through-hole in the exhaust manifold and is axially supported directly on the exhaust manifold. According to a first exemplary embodiment of the document, the spacer sleeve can also be formed integrally with the nut, in which case the nut is supported directly on the cylinder head via the spacer sleeve section. At the same time, the nut rests firmly on the outside of the exhaust manifold with a rigid flange. Even with the known arrangement, the bending moment occurring during operation can lead to plastic deformation of the threaded bolt and the nut breaking off. There is also a risk of the nut becoming loose, resulting in a loss of screw force and the risk of leaks.

[0004] Further prior art includes JP 2004-339947 A, DE 198 23 475 A1, DE 100 49 117 A1, DE 82 19 329 A, DE 41 26 744 A1, DE 198 07 312 A1, DE 199 60 619 A1, FR 2 902 457 A3 and JP 8-246868 A.

[0005] The above problem is alleviated by a fastening nut which is improved compared to the previously known fastening nuts and is described in EP 2 729 680 B1. The fastening nut described therein is of one-piece construction and, in addition to braking torque means for increasing the loosening torque, comprises a first support surface formed on a support section of a nut body in the form of an axial end face for support on the cylinder head, as well as an axially elastically prestressable spring section on which a (second) support surface is formed, with which the aforementioned spring section is supported directly on the exhaust manifold (exhaust manifold plate). The provision of the spring section enables the exhaust manifold to move relative to the second support surface, whereby the entire displacement force does not have to be absorbed by the nut.This then leads to less stress on the externally threaded bolt, reliably preventing its deformation or even tearing. However, the conventional fastening nut is difficult to manufacture using the cold extrusion process due to its complex shape. Furthermore, the spring force of the spring section is not scalable. The conventional fastening nut also necessarily rests on the cylinder head with its support section, which requires appropriately large through-holes in the exhaust manifold and a corresponding contact surface on the cylinder head.

[0006] WO 89 / 09344 discloses a locking screw comprising spring means that are driven into a blocking action with a fastening object, thereby increasing the loosening torque of the locking screw. A resilient or elastic support of the fastening object by means of the spring means is neither provided nor feasible, as otherwise the locking effect of the locking screw cannot be achieved. A corresponding teaching is also known from DE 203 01 402 U1.

[0007] DE 10 2009 023 721 A1 also teaches a lock nut in which spring means or spring elements are provided to achieve a securing effect. Thus, the spring elements form braking torque means within the meaning of the present disclosure. A resilient or elastic fastening of an exhaust manifold with simultaneous securing of the fastening nut, in particular by means of corresponding braking torque means, is not disclosed, which is why a secure and simultaneously resilient fastening of the exhaust manifold cannot be achieved with a lock nut according to this disclosure.

[0008] DE 298 17 010 U1 also discloses a screw connection in which a spring element is set back relative to the end face of a shaft section of a nut. The screw connection is intended for securing materials that cannot withstand high compression forces. Therefore, the screw connection is not suitable as a fastening nut for securing an exhaust manifold to a cylinder head.

[0009] The subject of DE 195 32 709 A1 is a screw nut produced by massive forming with a captively attached pressure plate, comprising an intentional thread defect as a braking torque means.

[0010] Furthermore, DE 199 56 287 A1 describes a nut with a thrust ring. DE 196 50 453 A1 discloses a method for producing an assembly nut and an assembly nut produced according to the method. Furthermore, GB 341 333 A discloses a fastening nut with elastic washers that prevent overtightening.

[0011] Based on the aforementioned prior art, the invention is therefore based on the object of specifying an improved, easily fixable fastening arrangement for securing an exhaust manifold to a cylinder head of an internal combustion engine, which, due to its nature, also opens up the possibility of scaling the spring force of the spring section of a fastening nut through simple measures. Furthermore, the fastening arrangement is intended to ensure that a minimum screw or clamping force is maintained on the exhaust manifold to guarantee tightness even after numerous load changes caused by heat / cold cycles, and to do so without the need to provide the large-area openings in the exhaust manifold that are indispensable for the solution described in EP 2 729 680 B1. Furthermore, the object is to specify an internal combustion engine with a correspondingly improved fastening arrangement.

[0012] This object is achieved by a fastening arrangement comprising at least one fastening nut, an exhaust manifold, which comprises an externally threaded bolt, and a cylinder head of an internal combustion engine, wherein the fastening nut is designed to fix the exhaust manifold to the cylinder head by screwing in an axial fixing direction with an externally threaded bolt held on the cylinder head and passing through a through-opening in the exhaust manifold, wherein the fastening nut comprises an internally threaded portion for screwing with the externally threaded bolt and braking torque means for increasing the release torque, further comprising a support surface for indirect or direct axial support on the exhaust manifold, wherein the support surface is designed on a radially projecting spring portion that can be elastically prestressed in the axial direction,wherein the fastening nut is formed in several parts and comprises a nut body extending axially from a rear end to a front axial end in the fixing direction, with a shaft portion having the axial end, and at least one first spring part separate from the nut body and captively secured to the nut body by means of securing means, in particular designed as a clamping washer, and in that the internal thread portion is formed on the nut body and in that the first spring part forms the spring portion with the support surface, which forms a frontmost axial end of the fastening nut in the axial fixing direction, relative to which the end of the shaft portion is set back and axially spaced with respect to the axial fixing direction.

[0013] According to the invention, the fastening nut secures the exhaust manifold to the cylinder head directly or indirectly with a predetermined screw force or preload force via the at least one externally threaded bolt, wherein the at least one spring part of the fastening nut is designed, in particular dimensioned, in such a way that, in a secured state of the fastening arrangement, a resilient and / or elastic indirect or direct contact of the support surface of the spring part with the exhaust manifold is achieved, wherein the braking torque means of the fastening nut serve to increase the loosening torque of the fastening arrangement and that the fastening nut, in the mounted state, with its support surface is not tightened to a block with the exhaust manifold or sliding plate.

[0014] With regard to the internal combustion engine, the object is achieved with the features of claim 11, i.e. by an internal combustion engine with a cylinder head to which an exhaust manifold is fixed by means of at least one fastening arrangement designed according to the concept of the invention, wherein the fastening nut is screwed onto an externally threaded bolt held on the cylinder head and passing through a through-opening in the exhaust manifold with its internally threaded section, in particular with the interaction of braking torque means with the externally threaded bolt (stud bolt), and applies force to the exhaust manifold in the direction of the cylinder head by means of the at least one spring part, which is elastically deflected away from the exhaust manifold (i.e.opposite to the axial fixing direction) and is supported in the axial direction with its support surface, preferably indirectly, in particular via a sliding plate (sliding plate) arranged between the support surface and the exhaust manifold (exhaust manifold plate). In the internal combustion engine according to the invention, the fastening nut according to the invention does not protrude into or pass through an exhaust manifold opening (through opening), but is located completely in the fixing direction above or outside the exhaust manifold and optionally, if provided, a sliding plate provided between the exhaust manifold and the fastening nut. Therefore, the through openings in the exhaust manifold for the externally threaded bolts can have a smaller cross-sectional area than in the prior art.

[0015] Advantageous developments of the invention are specified in the subclaims. The scope of the invention includes all combinations of at least two of the features disclosed in the description, the claims, and / or the figures.

[0016] The invention is based on the idea of ​​not designing the spring section as one piece with the nut section or nut body forming the internal thread section, in contrast to the prior art, but rather providing at least one separate component (spring part), in particular in the form of a disc spring (tension washer), as the spring section and captively holding or securing this to a nut body forming the internal thread section, on which the optional fastening means are preferably also provided, very particularly preferably monolithically (in one piece with the nut body). Very particularly preferably, the at least one spring part is arranged radially adjacent to a shaft section of the nut body or is penetrated by it, particularly preferably centrally.The detachable arrangement of the at least one spring part opens up the possibility of separate production of the spring section and the nut body, in particular by cold forming (preferably the nut body is produced by cold extrusion and / or the at least one spring part by stamping), without resulting in disadvantages during assembly of the exhaust manifold, in particular the exhaust manifold plate, on the cylinder head, since the spring part is already captively secured to the nut body via corresponding securing means, preferably designed for positively fixing the spring part to the nut body. Furthermore, the spring force of the spring section of the fastening nut is easily scalable by using spring parts of different dimensions, in particular having different spring constants, with one nut body or with identical nut bodies.It is also possible to arrange at least one additional (axially elastically tensionable or deformable) spring part captively on the nut body in addition to the spring part forming the support surface (front in the fixing direction), particularly on the side of this spring part facing away from the support surface, thereby increasing the spring stiffness. The spring parts can be of the same design or have different spring constants.

[0017] According to the invention, the spring parts, in particular the spring constants of the spring parts, are scaled such that, in the installed state of the fastening nut, a residual elastic deformability of the spring parts remains, at least in a cold state of the exhaust manifold. Conversely, this means that the spring parts are dimensioned and / or scaled such that, in the installed state, the spring parts do not move with their support surface into contact with the exhaust manifold or sliding plate. The spring parts are therefore dimensioned such that, when a predefined screw force or preload force is reached during the connection, in particular with an externally threaded bolt, resilient support of the spring parts and / or the fastening nut on a substrate, in particular an exhaust manifold or sliding plate, is achieved.

[0018] Accordingly, the present fastening arrangement serves, in particular by means of the spring parts of the fastening nut, for resiliently and / or elastically securing and, in particular by means of the braking torque means, for securing an exhaust manifold to a cylinder head of an internal combustion engine. Thus, the spring part of the fastening nut, in particular in the assembled state, exerts a spring effect.

[0019] Accordingly, the invention leads to a fastening arrangement comprising at least one fastening nut according to the invention which, via at least one externally threaded bolt, directly or indirectly secures an exhaust manifold to a cylinder head with a predetermined screw force or preload force, wherein the spring parts of the fastening nut are designed, in particular dimensioned, such that, in a secured state of the fastening arrangement, a resilient and / or elastic indirect or direct contact of the support surface of the spring parts with the fastening object is achieved, wherein the braking torque means of the fastening nut cause an increase in the loosening torque of the fastening arrangement. The spring part enables flexible support of the fastening nut in the fastening arrangement.

[0020] The at least one spring part is preferably, as mentioned, designed as a disc spring and has a, more preferably central, through-opening through which the nut body, in particular its shaft section, axially penetrates. In addition to the aforementioned advantages of simplified manufacture and simple scalability of the spring force and stiffness, the fastening nut according to the invention also ensures that the exhaust manifold, in particular an exhaust manifold plate, on which the fastening nut with the spring part is supported, in particular via a sliding plate arranged between the fastening nut and the exhaust manifold with the support surface of the spring part, can slide, i.e. can move relative to the fastening nut or its spring part, so that the risk of tearing off is reduced.Furthermore, by directly or indirectly supporting the exhaust manifold, the at least one spring component ensures the maintenance of a minimum preload or screw force, even during a multitude of load cycles caused by heat / cold cycles. This reliably prevents leaks in the area between the exhaust manifold and the cylinder head, and thus the discharge of hot exhaust gases into the engine compartment and / or the intake of external air into the exhaust system. The at least one spring component, designed in particular as a disc spring, primarily performs the task of applying spring force to the exhaust manifold, in particular via the aforementioned sliding plate. This axial preload maintains a minimum clamping force on the exhaust manifold.The spring element also takes on the function of a sliding washer (washer) which, despite the spring force applied to the exhaust manifold due to the elastic preload (deflection), enables the exhaust manifold to be displaced in the event of temperature fluctuations, either directly relative to the spring part and / or to the aforementioned sliding plate.

[0021] The fastening nut according to the invention, or its nut body, is designed without a support section for support on the cylinder head. On the contrary, the end face of the nut body is set back in the fixing direction relative to the support surface, so that an axial nut end, which is the foremost end in the fixing direction, is formed by the support surface of the (front) spring part. The axial distance between the front end face, which is set back in the fixing direction relative to the support surface, and the support surface is preferably at least 0.1 mm and is very particularly preferably selected from a value range between 0.1 mm and 5 mm, very particularly preferably between 0.1 mm and 3 mm, even more preferably between 0.2 mm and 1.5 mm, and very particularly preferably between 0.2 mm and 0.5 mm.

[0022] According to the invention, an embodiment is provided in which, when the fastening nut is tightened, a slight distance remains between the end face of the nut body and the component of the internal combustion engine against which the spring part rests with its support surface. Preferably, the axial distance between the end face of the nut body, which is set back in the fixing direction relative to the support surface, and the support surface of the first spring part is greater than a maximum spring travel of the at least one spring part, in particular of the plurality of spring parts.

[0023] There are various options regarding the specific design of the securing means. In principle, it is possible to design these as a separate component from the spring part and / or the nut body. However, a particularly preferred embodiment is one in which the securing means are monolithic, i.e., formed integrally with the nut body, in particular in the form of at least one radial projection, particularly preferably in the form of two axially spaced radial projections (abutments), between which the at least one spring part is received, at least in sections, in order to thus secure the spring part to the nut body in the axial direction.

[0024] As mentioned, the fastening nut designed according to the concept of the invention comprises braking torque means that are implemented monolithically on the nut body. According to the invention, these prevent spontaneous loosening of the nut, in particular by ensuring that the friction between the nut and the threaded bolt is increased. In other words, the loosening torque that must be applied to the nut is increased so that the nut is axially adjusted by rotating it in the circumferential direction against the fixing direction. The braking torque means can, as will be explained later, preferably be designed as disclosed in WO 2007 / 076968 A1 or EP 2 729 680 B1. The braking torque means ensure that the nut does not loosen despite possible sliding of the exhaust manifold. In addition to braking torque means on the fastening nut, braking torque means can be provided on the externally threaded bolt of the internal combustion engine.Instead of the above-described embodiment of braking torque means, other embodiments can be realized, for example, deformed threads and / or flanks, etc. Accordingly, it is clear that the spring parts serve for resilient fastening, in particular of the exhaust manifold, whereas the braking torque means secure the fastening nut.

[0025] As already explained, the spring force of the fastening nut, particularly when using identical nut bodies, is easily scalable by, in addition to the spring part having the support surface, in particular axially adjacent to the spring part, very particularly preferably on an axial side of the spring part facing away from the support surface, at least one, preferably exclusively one, further second spring part (also separate from the nut body) is captively secured to the nut body via securing means. The multiple spring parts are preferably arranged in series. The more spring parts used, the greater the flexibility of the spring assembly and thus the greater the spring travel.In the case of providing a second spring part, it is preferable that the first spring part is not supported with an axial side facing away from the support surface on a radially projecting, rear abutment section of the nut body, but rather the second spring part, while the first spring part is supported directly or indirectly on the second spring part.

[0026] If at least two, preferably only two, axially adjacent spring parts are provided, there are different options with regard to their concrete design and orientation. For example, it is preferred to design both spring parts as disc springs, in particular with a through-opening, which is particularly preferably central. Both spring parts can be inclined or curved in the same direction, in particular in the fixing direction. Alternatively, it is also conceivable to incline and / or curve the two spring parts in opposite directions, in particular away from each other, such that the radially outer edge regions of the spring parts point in opposite axial directions, in which case the second spring part is preferably, but not necessarily, supported with a radially outer edge region on the radially projecting abutment section of the nut body. For the case of the same orientation orCurvature / inclination of the spring parts, it is preferred if the second spring part is supported axially on the abutment section of the nut body with a radially inner or centric edge region.

[0027] It is particularly expedient if the fastening nut has drive means, for example in the form of at least one pair of wrench flats or a polygonal or multi-round recess on the front side, in particular in the form of an Allen or Torx drive. Such drive means are preferably formed monolithically with the nut body.

[0028] A particularly advantageous embodiment of the fastening nut is one in which both the nut body and the spring part separate from it are formed from metal, in particular as cold-formed parts. A particularly preferred embodiment of the fastening nut is one in which it does not comprise any additional components besides the nut body and the at least one spring part.

[0029] With regard to the specific design of the securing means, there are various options. It is particularly expedient for the spring part not to be supported axially in the fixing direction on a front, axial abutment section (projecting outward in the radial direction, preferably designed to positively secure the spring part to the nut body), which is most preferably designed as an annular bead on the nut body and furthermore implemented monolithically with it. Such an axial front abutment section can be realized, for example, by caulking and the resulting reshaping of the nut body, in particular after sliding the spring part onto the separate nut body.

[0030] It has proven particularly expedient if a recess, preferably in the form of an inner conical surface or a preferably concavely rounded surface, is formed on the spring part, in particular an annular one, which tapers the through-opening in the spring part in a radial direction opposite to the fixing direction. The spring part can be supported on the front axial abutment section via such a beveled or rounded surface.

[0031] It is particularly preferred if the at least one spring part, in particular a second spring part, is supported axially with its (axial) side facing away from the support surface on a rear, axial abutment section formed monolithically on the nut body, which is particularly preferably designed as a circumferential collar on the nut body. This rear abutment section, in particular the circumferential collar, is particularly preferably designed and arranged such that it limits a maximum preload of the at least one spring part, in that the spring part bears further or increasingly against the axial rear abutment section with increasing preload.An embodiment is particularly preferred in which, in addition to the rear abutment section just explained, the previously mentioned front abutment section is provided, in particular in the form of an annular bead, so that the at least one spring part is sandwiched between the abutment sections.

[0032] There are various possibilities with regard to the arrangement of the internal thread section. For example, contrary to the teaching of EP 2 729 680 B1, the internal thread section can also be formed only on the inner circumference of the axial shaft section provided in an axially front end region of the nut body and can extend there preferably to the axially front end of the nut body adjacent to the end face. Preferably, the internal thread section is also or exclusively provided in the axial extension of the shaft section of the nut body to the rear. An embodiment of the fastening nut is very particularly preferred in which the internal thread section, optionally interrupted by an inner circumferential groove for implementing the braking torque means, is formed axially continuously on the inner circumference of a through-opening passing through the fastening nut.In an alternative embodiment, the shaft section is at least partially free of internal threads on its inner circumference.

[0033] As mentioned, it is particularly preferred if the braking torque means are formed directly on the nut body, wherein it is further preferred if the braking torque means increase the release or holding torque, preferably exclusively, due to elastic deformation or a resulting increase in friction. For example, this can be achieved by interrupting the internal thread section with an annular groove, resulting in two axially spaced internal thread regions that are elastically adjustable relative to one another, and the internal threads of the internal thread regions are arranged offset axially and / or circumferentially in order to realize a pitch jump from which the braking torque results when screwing with the externally threaded bolt. The braking torque effect is most preferably achieved as disclosed in WO 2007 / 076968 A1.In addition to the braking torque means on the nut, as already explained, braking torque means can be provided on the externally threaded bolt, for example by deforming the external thread of the externally threaded bolt. As an alternative to the design of the braking torque means described in the aforementioned publications, a thread deformation can also be provided, for example, preferably on the internal thread of the braking torque nut or alternatively on the stud bolt, for example in the form of a preferably axial line or line embossing.

[0034] Within the scope of the internal combustion engine according to the invention, which comprises the fastening arrangement designed according to the concept of the invention, it is preferred if the nut body does not protrude with its end face into a through-opening provided in the exhaust manifold and / or into a through-opening provided on an optional sliding plate arranged on the exhaust manifold. In principle, it is possible for the fastening nut, with appropriate dimensioning, to be supported with its front end face together with the then elastically prestressed spring part on the same component, in particular an optional sliding plate, or alternatively directly on the exhaust manifold. It is according to the invention if the fastening nut is not tightened to a block, i.e. in such a way that even when the fastening nut is tightened, the end face is arranged set back relative to the support surface of the spring part with respect to the fixing direction.

[0035] Further advantages, features and individual parts of the invention will become apparent from the following description of a preferred embodiment and from the drawings.

[0036] These show in: Fig. 1: a longitudinal sectional view through a fastening nut designed according to the concept of the invention along the section line AA according to Fig. 2 , Fig. 2: a top view of the fastening nut according to Fig. 1 in an axial fixing direction and Fig. 3: an enlarged detail of Fig. 1 , whereby to clarify the arrangement of the fastening screw on the combustion engine, the latter is shown in detail below the fastening nut.

[0037] In the figures, identical elements and elements with the same function are identified by the same reference numerals.

[0038] In Fig. 3 a section of an internal combustion engine 1 is shown. The internal combustion engine 1 comprises an exhaust manifold 2, which is fastened to a cylinder head 4 of the internal combustion engine 1 by means of a fastening nut 3, shown here in section and designed according to the concept of the invention, and is subjected to axial force against the cylinder head 4. For this purpose, the nut 3 is screwed to an externally threaded bolt (stud bolt) (not shown) having an external thread, which is anchored in the cylinder head 4 and passes through a through-opening 5 in the exhaust manifold 2 and a sliding plate 6 arranged thereon. The diameter of this through-opening 5 is small and corresponds essentially to the diameter of the externally threaded bolt plus a clearance. Not shown is an optional flat gasket, preferably arranged between the exhaust manifold 2 and the cylinder head 4.

[0039] The externally threaded bolt passes through the aforementioned through-opening 5 in the exhaust manifold 2 and in the sliding plate 6 and projects beyond the exhaust manifold 2 counter to an axial fixing direction F of the fastening nut 3. The fastening nut 3 is designed as a lock nut and comprises, in a region facing away from the cylinder head 4, braking torque means (not shown), which in the exemplary embodiment shown can be realized, for example, as in WO 2007 / 076968 A1 or in another way, for example by deformation of an internal thread 7 of the fastening nut 3 and / or on the externally threaded bolt corresponding to the internal thread 7.In any case, the braking torque means are designed such that they increase the loosening torque for loosening the fastening nut 3 compared to a design without braking torque means and thus secure the fastening nut 3 against loosening, for example due to vibration or twisting of the fastening nut 3 by pushing the exhaust manifold 2 when heated.

[0040] As can be seen from Fig. 3 The fastening nut 3 is designed in several parts and comprises a nut body 8 designed as a cold-formed part with an internal thread opening 9, on the inner circumference of which the internal thread 7 is formed axially continuous. Two spring parts 10, 11, each designed as a tension spring or disc spring, are captively fastened to the nut body 8, wherein hereinafter the spring part designated by the reference numeral 10 is referred to as the front, first spring part 10 and the spring part designated by the reference numeral 11 is referred to as the second spring part. The two spring parts 10, 11 are supported axially directly on one another and are received in a sandwich-like manner between a radially projecting rear abutment 12 designed as a circumferential collar and a radially shortened circumferential bead which is axially spaced therefrom in the fixing direction F and forms a front abutment 13.The abutments 12, 13 (abutment sections of the nut body) are formed monolithically with the nut body 8 and serve as securing means for captively holding the spring parts 10, 11. It can be seen that the spring parts 10, 11 are curved in opposite directions, with the first spring part 10 being curved in the fixing direction F. The two spring parts 10, 11 abut one another with a radially inner edge region, with the axial distance increasing with increasing radial extension of the spring parts 10, 11 and thus forming a . Fig. 3 marked maximum spring travel s. The second spring part 11, which is at the rear in the fixing direction F, is supported axially on the rear abutment 12 with a radially outer edge region, while the first spring part 10 is supported on the front abutment 13 with a radially inner edge region.

[0041] It can be seen that the spring parts 10, 11 are located on a shaft section 14 of the nut body, which is axially spaced from a drive 15 of the nut body 8, which in the present case is formed by a number of key surfaces, as can be seen in particular from the illustration according to Fig. 2 results.

[0042] The nut body 8 has a front axial end face 16 (end face) in the fixing direction, which is axially set back opposite to the fixing direction F with respect to a support surface 17 formed by the first spring part 10, i.e. is spaced apart from this, so that a front end of the fastening nut 3 in the fixing direction F is formed by the support surface 17 of the first spring part.

[0043] A key width S of the key surface pairs is in Fig. 2 marked.

[0044] As from Fig. 2As can be seen, the axial distance between the end face 16 of the nut body 8 and the support surface 17 is greater than the maximum spring travel s, so that in the screwed state or when fastened to the stud bolt (externally threaded bolt), contact between the end face 16 and the support surface 17 is avoided - alternatively, with the nut body 8 extended accordingly in the fixing direction F, it is conceivable that the fastening nut is supported with both the end face 16 and the support surface 17 on the same part, in the present case, for example, on the sliding plate 6 or alternatively, in an embodiment without a sliding plate 6, directly on the exhaust manifold 2 - however, the variant shown with the remaining axial distance is preferred.

[0045] When screwing the fastening nut 3 with the aforementioned external thread bolt by turning the fastening nut 3 in a circumferential direction, the fastening nut 3 is adjusted in the direction of the exhaust manifold in the fixing direction F, whereby the first spring part 10 comes into contact with the combustion engine and as a result, upon further turning of the fastening nut and a resulting further adjustment of the fastening nut in the fixing direction F, the spring parts 10, 11 are pre-tensioned and thus increase the elasticity of the clamped assembly and build up a reserve against settling. List of reference symbols

[0046] 1 Combustion engine 2 Exhaust manifold 3 Fastening nut 4 Cylinder head 5 Through hole 6 Sliding plate 7 Internal thread 8 Nut body 9 Internal thread opening 10 First spring part 11 Second spring part 12 Rear abutment (rear abutment section) 13 Front abutment (front abutment section) 14 Shaft section 15 Drive (drive means) 16 Front end 17 Support surface Faxial fixing direction smaximum spring travel Swrench flat dimension

Claims

1. A fastening assembly, comprising at least one fastening nut (3), an exhaust manifold (2), which comprises an external-thread bolt, and a cylinder head (4) of a combustion engine (1), the fastening nut (3) being configured for fixing the exhaust manifold (2) on the cylinder head (4) by being screwed in an axial fixation direction (F) with the external-thread bolt held on the cylinder head (4) and forming a passage opening (5) in the exhaust manifold (2), the fastening nut (3) comprising an internal-thread section for being screwed on the external-thread bolt and braking-torque means for increasing the loosening torque, the fastening assembly further comprising a support surface (17) for direct or indirect axial support at the exhaust manifold (2), the support surface (17) being formed on a radially protruding spring section which is elastically pre-tensioned in the axial direction, the fastening nut (3) being designed in several pieces and comprising a nut body (8), which extends from a rear end to an axial front face (16) in the front in relation to the fixation direction (F) and has a shaft section (14) having the axial front face (16), and at least a first spring part (10), which is separate from the nut body (8), is captively fixed to the nut body (8) via securing means, is in particular formed as a spring washer and is formed on the nut body (8) of the internal-thread section, and the first spring part (10) forming the spring section having the support surface (17), which forms an axial end of the fastening nut, which is the front-most end in relation to the axial fixation direction (F), the front face (16) of the shaft section (14) being recessed in relation to the front-most axial end and to the axial fixation direction (F) and being axially spaced apart, characterized in that the fastening nut (3) directly or indirectly secures the exhaust manifold (2) on the cylinder head (4) via the at least one external-thread bolt using a pre-specified screwing force or pre-tensioning force, the at least one spring part (10) of the fastening nut (3) being designed, in particular dimensioned, such that the support surface (17) of the spring part (10) resiliently and / or elastically abuts directly or indirectly against the exhaust manifold (2) in a secured condition, the braking-torque means of the fastening nut (3) serving to increase the loosening torque of the fastening assembly and in that the support surface (17) of the fastening nut (3) is not pulled to block thickness with the exhaust manifold (2) or sliding plate in the mounted state.

2. The fastening assembly according to claim 1, characterized in that in addition to the first spring part (10) and axially adjacent to the first spring part (10), at least, preferably only, one second spring part (11) separate from the nut body (8) and preferably designed as a spring collar is captively fixed to the nut body (8) via the securing means on the axial side (16) facing away from the support surface (17).

3. The fastening assembly according to claim 1 or 2, characterized in that the at least one spring part, preferably designed as an inclined and / or curved, preferably circumferentially closed, spring collar, is beveled or curved with respect to a radial plane extending perpendicular to the axial extensions of the nut body (8).

4. The fastening assembly according to claim 3, characterized in that the first and the second spring part (11) is inclined and / or curved in the same or in opposite axial directions.

5. The fastening assembly according to any one of the preceding claims, characterized in that the nut body (8) and the at least one spring part (10, 11) is made of metal, in particular as cold extruded parts.

6. The fastening assembly according to any one of the preceding claims, characterized in that the securing means comprise an axial front thrust-bearing section (13), in particular formed by caulking and in particular a toroidal expansion joint, on the nut body (8).

7. The fastening assembly according to any one of the preceding claims, characterized in that the first spring part (10) or the second spring part (11) is axially supported on a rear thrust-bearing section (12) with its side (16) facing away from the support surface (17), the thrust-bearing section (12) being formed monolithically on the nut body (8), in particular realized as a circumferential collar, and being formed and disposed preferably a maximum pre-tension of the at least one spring part (10, 11) in a limiting manner.

8. The fastening assembly according to claim 7, characterized in that an axial front face of the first and / or second spring part (10, 11) facing the rear axial thrust-bearing section (12) encloses an angle, which becomes reduced in size as the elastic pre-tension of the spring becomes increases, in conjunction with a side of the rear thrust-bearing section (12) facing the axial front face.

9. The fastening assembly according to any one of the preceding claims, characterized in that at least sections of the internal-thread section are formed on the inner circumference of the shaft section (14) of the nut body (8).

10. The fastening assembly according to any one of the preceding claims, characterized in that the braking-torque means are formed to increase the friction between the nut and thread bolt owing to elastic deformation of a deflecting section carrying an internal-thread section.

11. A combustion engine having a cylinder head (4), on which an exhaust manifold (2) is fastened with the aid of at least one fastening assembly (3) according to any one of the preceding claims, the fastening nut (3) being screwed on by its internal-thread section using an external-thread bolt, which is held on the cylinder head (4) and forms a passage opening (5) in the exhaust manifold (2), in particular with the braking-torque means in interaction with the external-thread bolt, and applying force on the exhaust manifold (2) in the direction of the cylinder head (4) by means of the at least one spring part (10, 11), which is elastically deflected away from the exhaust manifold (2) and is supported by its support surface (17) preferably directly, in particular via a sliding plate (6), or alternatively indirectly, on the exhaust manifold (2) in the axial direction.

12. The combustion engine according to claim 11, characterized in that the front face (16) of the shaft section (14) is axially spaced apart and recessed from the exhaust manifold (2) and / or a facultative sliding plate (6), which is disposed on the exhaust manifold (2), against the fixation direction (F).