Fluid coupling, especially for fluid-carrying lines in motor vehicles, combination of the fluid coupling with a corresponding counterpart and method for making a connection between two fluid lines

Abstract

Fluid coupling, especially for fluid-carrying lines in motor vehicles, with: a housing (20) which has a receptacle (43) for a counterpart (50), a locking element (44) which is arranged in or on the receptacle (43) and which can engage a locking rib (52) of the counterpart (50) in such a way that the counterpart (50) is fixed in the axial direction in the receptacle (43), and a detection sleeve (60) which is arranged to be axially displaceable in the receptacle (43) and which has at least a first engagement section (61) which, when the counterpart (50) is inserted, can engage with the locking rib (52) in such a way that the detection sleeve (60) is axially displaced from an initial position in the insertion direction of the counterpart (50) towards a detection position, and which has at least a second engagement section (62) which is arranged behind the first engagement section (61) in the insertion direction and, when the counterpart (50) is withdrawn, can engage with the locking rib (52) in such a way that the detection sleeve (60) is axially displaced from the detection position opposite to the insertion direction of the counterpart (50) towards the initial position, wherein the detection sleeve (60) has at least one detection section (64) which in the initial position is received within the receptacle (43) such that the detection section (64) is not radially visible from the outside, and in the detection position protrudes from the receptacle (43) such that the detection section (64) is visible from the outside, and wherein the detection section (64) is designed as a guide rail to guide the detection sleeve (60) axially displaceably in guide grooves (48) of the housing (20), so that the detection sleeve (60) is displaceable within the receptacle (43) of the housing (20) in the axial direction of the fluid coupling.

Description

[0001] The present invention relates to a fluid coupling, in particular for fuel lines in motor vehicles, and to a combination of the fluid coupling with a corresponding counterpart. However, the fluid coupling can also be used for other fluid lines in motor vehicles. Examples include coolant lines, windshield washer fluid lines, hydrogen lines, air lines, and crankcase ventilation systems. Furthermore, the invention relates to a method for connecting two fluid lines.

[0002] Fuel lines in motor vehicles typically have fluid couplings for the detachable connection of two fuel lines, for example, at submersible pumps in fuel tanks, to replace a defective submersible pump. These fluid couplings should be quick and easy to connect and disconnect for this purpose.

[0003] As in Fig. As shown in Figure 7, DE 10 2016 001 610 A1 discloses such a fluid coupling. This plug-in coupling, designed for the detachable connection of the ends of two fluid lines, consists of a plug-in part (in Fig. 7 not shown) and a socket part composed of a first socket section 3 and a second socket section 5. In the insertion state, the insertion part is axially locked in the second socket section 5 and rotatably received about its axis, wherein the second socket section 5 can in turn be inserted into the first socket section 3 at different angles of rotation about the common axis and is axially locked.

[0004] The second sleeve section 5 carries an actuating element 7, which is movable between a locking position, in which an axial pull-out protection of the insert part is shown; and an unlocking position, in which this pull-out protection is released. For this purpose, a locking element 12, which can engage with a locking rib of the insert part, is arranged at the elastically deformable end of a tab 11.

[0005] In the rest state of the tab 11, the locking element 12 engages with the (not shown) locking rib of the insert part. To release the engagement, the actuating element 7 is moved in the direction of arrow 14 against the elastic restoring force of the tab 11 in order to move the locking element 12 radially outwards and thus out of engagement with the locking rib.

[0006] This design allows the rotational position of the second sleeve section 5, which carries the actuating element 7, relative to the insertion part and the first sleeve section 3, and thus the actuating position of the insertion coupling, to be adjusted, taking into account the respective installation conditions, with the proviso that the actuating element 7 is unobstructedly accessible. Furthermore, a window 15 is arranged in the second sleeve section 5, which allows visual verification of a correct locking state.

[0007] However, visual inspection of the locking status is sometimes difficult – depending on the installation and space constraints in a vehicle – and may only be possible with appropriate aids such as a flashlight and mirror. Therefore, there is a need for a fluid coupling where the locking status can be detected easily and without aids.

[0008] US 5 226 679 A discloses a quick-connect insertion indicator in which circumferentially spaced axially extending legs are visible before the quick-connect is engaged and are concealed when fully engaged.

[0009] DE 10 2016 001 610 A1 discloses a plug-in coupling for the detachable connection of the ends of two media lines.

[0010] US 5 829 792 A describes a hose coupling with an indicator for visual inspection of the appropriate sealing and locking position.

[0011] The object of the invention is therefore to provide a detachable fluid coupling in which the correct locking state can be detected easily and reliably.

[0012] This task is solved by the characteristics of the independent claims. Advantageous further developments are defined in the dependent claims.

[0013] One aspect of the invention relates to a fluid coupling, in particular for fluid-carrying lines such as fuel lines in motor vehicles, comprising: a housing which has a (essentially cylindrical) receptacle for a counterpart or a pipe section, a locking element or a bolt or a locking device that is arranged in or on the receptacle and can engage behind or with a locking rib of the counterpart in such a way that the counterpart is fixed in the receptacle in the axial direction, and a detection sleeve which is axially displaceable in the receptacle and has at least a first engagement section which, when the counterpart is inserted, can engage with the locking rib of the counterpart in such a way that the detection sleeve is axially displaced from an initial or origin position in the insertion direction of the counterpart into a detection position, and has at least a second engagement section which is arranged behind the first engagement section in the insertion direction and, when the counterpart is withdrawn, can engage with the locking rib in such a way that the detection sleeve is axially displaced from the detection position opposite to the insertion direction of the counterpart into the initial position, and wherein the detection sleeve has at least one detection section which in the initial position is received within the receptacle in such a way that the detection section (radial or perpendicular to the tube axis) is not visible from the outside, and in the detection position protrudes or extends out of the receptacle in such a way that the detection section is visible from the outside.

[0014] Because the detection section is only visible when the fluid coupling is fully locked, a technician can easily determine whether the fluid coupling is properly engaged. This allows for visual detection of the locking status without the need for tools such as a flashlight or mirror.

[0015] Preferably, the second engagement section is elastically deformable and is in its undeformed state in the initial position of the detection sleeve and in its elastically deformed state in the detection position, whereby the second engagement section can only engage with the locking rib in its elastically deformed state. In other words, the radial distance of the second engagement section to an axial center of the fluid coupling changes due to elastic deformation such that the radial distance is reduced. In the state of the reduced radial distance, the locking rib abuts the second engagement section of the detection sleeve, while in the state of no elastic deformation of the second engagement section, there is a clearance between the second engagement section and the locking rib.

[0016] According to the invention, the detection section is designed as a guide rail to guide the detection sleeve axially displaceably within the housing or in a complementary guide groove of the housing. Thus, the detection section fulfills a dual function: axial guidance and visual detection, thereby reducing the number of parts and enabling the fluid coupling to have a smaller overall size.

[0017] Preferably the first engagement section has the shape of a partial circle or arc or a complete circle, and / or the second engagement section can be formed at a rear end of the detection section in the insertion direction.

[0018] Preferably, the locking element is movable essentially orthogonal to the insertion direction and elastically prestressed, and has an inclined surface on its proximal side, such that the locking element is elastically deflected when the mating part is inserted by contact between a distal surface of the mating part's locking rib and the inclined surface of the locking element. In this way, the locking element is displaced or elastically deflected so that the locking rib can pass over or bypass the locking element, thus establishing the locked state by contact between a distal surface of the locking element and a proximal surface of the locking rib.

[0019] Furthermore, the elastic restoring force of the locking element preferably moves the mating part across the inclined surface against the insertion direction if the locking element is incompletely inserted into the receptacle. Thus, the mating part is pushed out of the fluid coupling when incompletely inserted, making it easy for a technician to see that a proper connection has not been established.

[0020] Preferably, the detection sleeve has at least one elastically restoring hook that engages with the housing or a distal end face of the housing's guide groove when the detection sleeve is inserted, thus securing the detection sleeve axially within the housing. This condition corresponds to the fluid coupling's delivery state; that is, the detection sleeve is already secured within the housing so that it cannot fall out and therefore does not need to be installed at the assembly site. Preferably, the at least one hook is arranged at its leading end (in the insertion direction) on at least one detection section.

[0021] The hook(s) can, however, be located at a different point on the detection sleeve than on the detection section. Alternatively, the housing can incorporate locking devices, such as elastically rebounding hooks, that can engage with the detection sleeve.

[0022] Preferably, the housing is designed in two parts, with a second housing part comprising the receptacle, the locking element, and the detection sleeve. A first housing part can be connected to the second housing part at different angles of rotation and has an angled connection spigot. Thus, depending on the available space, the angle of rotation between the two housing parts can be selected to allow for unobstructed installation.

[0023] Preferably, the housing and / or the locking element and / or the detection sleeve are made of a thermoplastic, such as PA6, PA6.6, or PA12. The detection section is preferably made of a thermoplastic of a different color than the housing to facilitate detection.

[0024] Furthermore, the invention relates to a combination of a fluid coupling as described above and a counterpart, wherein the counterpart is tubular and the locking rib is formed as a radially projecting collar.

[0025] According to another aspect, a method for creating a connection between two fluid lines, in particular fuel lines in motor vehicles, is provided with the following steps: Providing a housing designed with a receptacle for a mating part, Providing the counterpart with a locking rib, Providing a locking element that is arranged in or on the receptacle and can engage behind the locking rib of the counterpart in such a way that the counterpart is fixed in the receptacle in the axial direction, and Providing a detection sleeve that is arranged to be axially displaceable in the receptacle and has at least a first engagement section which, when the counterpart is inserted, engages with the locking rib in such a way that the detection sleeve is axially displaced from an initial position in the insertion direction of the counterpart into a detection position, and has at least a second engagement section which is arranged behind the first engagement section in the insertion direction and, when the counterpart is withdrawn, engages with the locking rib in such a way that the detection sleeve is axially displaced from the detection position opposite to the insertion direction of the counterpart into the initial position. wherein the detection sleeve is designed with at least one detection section which, in the initial position, is received within the receptacle in such a way that the detection section is not visible from the outside, and in the detection position, protrudes or extends out of the receptacle in such a way that the detection section is visible from the outside, wherein the detection section is designed as a guide rail to guide the detection sleeve axially displaceably in guide grooves of the housing, so that the detection sleeve is displaceable within the housing receptacle in the axial direction of the fluid coupling, Inserting the counterpart into the housing, and Detect whether the detection section is visible (viewed in a radial direction or perpendicular to the tube axis).

[0026] By detecting or verifying the visibility of the detection section after inserting the counterpart, a proper connection status can be determined in a simple, quick and reliable manner.

[0027] The invention is explained in more detail below with reference to the accompanying drawings. Fig. Figure 1 shows a top view of the fluid coupling with the mating part inserted. Fig. Figure 2 shows an exploded view of the fluid coupling of Fig. 1. Fig. Figure 3 shows a modification of the fluid coupling from Fig. 2. Fig. Figure 4 shows the modification of the fluid coupling from Fig. 3 rotated by 90 degrees. Fig. Figure 5 shows a sectional view of the fluid coupling of Fig. 1 with an incompletely inserted counterpart. Fig. Figure 6 shows a sectional view of the fluid coupling with the mating part fully inserted. Fig. Figure 7 shows a state-of-the-art fluid coupling.

[0028] In the following, the side facing in the direction of insertion of the fluid coupling is referred to as the distal side and the side opposite the direction of insertion as the proximal side.

[0029] As in Fig. 1 and Fig. As shown in Figure 2, a fluid coupling according to the invention comprises a housing 20 and a counterpart 50 that is inserted or can be inserted into it. The housing 20 is preferably composed of a first housing part 30 and a second housing part 40. Both the housing 20 and the counterpart 50 each have a hose connection 32, 54 at an end opposite the insertion point. The hose connection 32, 54 has a plurality of circumferential ribs or projections to seal against an attached hose.

[0030] Both the housing 20 and the counterpart 50 are essentially cylindrical. The housing 20 has an essentially cylindrical receptacle 43 into which the counterpart 50 can be inserted to connect the housing 20 and counterpart 50 in a fluid-tight manner. The counterpart 50 is essentially tubular and has an internal fluid passage 55.

[0031] The counterpart 50 has a locking rib 52 on its outer circumference to allow for (in Fig. 1 and Fig. 2 (not shown) locking element 44 to engage. The locking element 44, which will be referred to later with reference to Fig. 5 and Fig. As explained in more detail in section 6, the locking element 44 is located at the end of an elastically deformable tab 45. The tab 45 is arc-shaped and extends over a partial circle of the circumference of the second housing part 40. Furthermore, a handle 46 is located at the end of the elastic tab 45 to elastically deform the tab 45 from the inside of the tube outwards, thus disengaging the locking element 44 and the locking rib 52.

[0032] Although the locking element 44 is brought into engagement with the locking rib 52 in an elastic manner essentially radially by the tab 45, the locking element 44 can also be radially pre-tensioned in another way, for example by a spring.

[0033] Furthermore, an O-ring is arranged as a seal 35 to seal between the first housing part 30 and the counterpart 50. However, the invention is not limited to this. Instead of an O-ring, any other seal, such as a molded seal, can also be used.

[0034] The second housing part 40 has the essentially cylindrical receptacle 43 for receiving the essentially tubular counterpart 50. Furthermore, a plurality of guide grooves 48 are arranged around the circumference of the housing part 40, as in the example of Fig. 2 three guide grooves 48. However, the invention is not limited to the arrangement of three guide grooves 48, but it can also be arranged with only one guide groove 48 or two or more than three guide grooves 48.

[0035] A detection sleeve 60 can be inserted into the receptacle 43 of the second housing part 40. This detection sleeve 60 is essentially circular or semicircular around the center of the pipe axis and has a plurality of detection sections 64. The detection sections 64 are elongated and extend axially around the circumference of the circular or semicircular shape of the detection sleeve 60, and thus along the longitudinal axis of the pipe. Furthermore, the detection sections 64 are designed as guide rails to be guided in the guide grooves 48 of the second housing part 40. In this way, the detection sleeve 60 is displaceable axially within the receptacle 43 of the second housing part 40 along the fluid coupling.

[0036] The detection section 64 or the guide rail preferably has a substantially rectangular or arcuate cross-section for guidance within the guide groove 48. However, the invention is not limited to this. The cross-section of the detection section 64 and the guide groove 48 can also, for example, have a convex cross-section, a circular cross-section, a triangular or pentagonal cross-section, or an elliptical cross-section.

[0037] Furthermore, at least one of the detection sections 64 has at least one hook 66 at its distal end, preferably a pair of hooks 66 on each lateral side. When the detection sleeve 60 is inserted, the hook(s) 66 engage with a distal end face 48a of the guide groove 48 of the second housing part 40, so that the detection sleeve 60 is secured within the receptacle 43 of the second housing part 40 and cannot fall out. Movement of the detection sleeve 60 is only possible in the axial direction of the fluid coupling. To remove the detection sleeve 60, the hooks 66 must be elastically deformed to release the engagement between the hook(s) 66 and the distal end face 48a of the guide groove 48. However, the hook(s) 66 can also be arranged at a different location on the detection sleeve 60 than on the detection section 64.Alternatively, the housing can have 20 securing devices, such as elastically retractable hooks, which can engage with the detection sleeve 60.

[0038] As later, particularly with reference to Fig. 5 and Fig. As explained in section 6, the detection sleeve 60 is thus movable between an initial or origin position and a detection position within the receptacle 43 in the axial direction of the second housing part 40. In the origin position, the hooks 66 are in contact with the distal end 48a. In the detection position, however, the detection sections 64 project from the guide groove 48 in the axial or distal direction such that the detection sections 64 protrude from the receptacle 43 and are visible from the outside, whereas in the origin position they are concealed by the guide groove 48 and are not visible.

[0039] The detection sleeve 60 is now referred to Fig. 3 explained in more detail. As already described, the detection sleeve 60 has a plurality of detection sections 64, in the exemplary embodiment of Fig. 3 three elongated detection sections 64, which are distributed around the circumference of the detection sleeve 64. One of the detection sections 64, in the example of Fig. 3 the middle detection section 64, has the pair of hooks 66.

[0040] Furthermore, the detection sleeve 60 has a first engagement section 61 which is radially offset inwards relative to the detection sections 64 and has the shape of a partial circle. However, the invention is not limited to this. The first engagement section 61 can also be designed as a complete circle. The circumference of the partial circle or the complete circle of the first engagement section 61 is matched to the circumference of the locking rib 52 of the counterpart 50 such that, when the counterpart 50 is inserted, the locking rib 52 abuts the first engagement section 61 and thus displaces the detection sleeve 60.

[0041] A second engagement section 62 is formed at a proximal end of the detection sleeve 60, i.e., at an axial end of the detection sleeve 60 opposite the hooks 66. This second engagement section 62 is designed as an extension of the detection sections 64 in the proximal direction. In the case of the exemplary embodiment of Fig. Thus, three second engagement sections 62 are formed. An inner circumference of the radially inwardly projecting tips 62a of the second engagement sections 62 is matched to the circumference of the locking rib 52 of the counterpart 50 in such a way that the locking rib 52 is not hindered in its axial movement by the tips 62a of the second engagement sections 62 of the fluid coupling.

[0042] However, the tips 62a of the second engagement sections 62 can be displaced or deformed radially inwards in an elastic manner in order to engage with the locking rib 52 of the counterpart 50, as will be explained later with reference to Fig. 5 and Fig. Section 6 is explained.

[0043] Furthermore, in Fig. Figure 3 shows that in this embodiment two seals 35, preferably O-rings, are arranged and a disk 36 is arranged between these seals. The arrangement of two seals 35, as opposed to only one seal 35 as in the embodiment of Fig. As shown in Figure 2, this has the advantage of better sealing and, in particular, greater safety in the event of the failure of one seal 35, because in this case the second seal 35 can take over the complete sealing of the fluid coupling.

[0044] Fig. Figure 4 shows an exemplary embodiment of Fig. 3 with the two seals 35, wherein the housing 20 of the fluid coupling is rotated by about 90 degrees.

[0045] The functions of the fluid coupling are now described with reference to Fig. 5 and Fig. 6 explained in more detail. Fig. 5, the counterpart 50 is incompletely inserted into the housing 20 of the fluid coupling. In this position, the detection sleeve 60 is in its initial or original position. Fig. 6, however, the counterpart 50 is fully inserted into the housing 20 of the fluid coupling and in this position the counterpart 50 is locked to the housing 20 and the detection sleeve 60 is in the detection position.

[0046] As in Fig. As shown in Figure 5, when the counterpart 50 is inserted into the receptacle 43 of the second housing part 40, the locking rib 52 of the counterpart 50 passes the second engagement section 62 without engaging with it. However, the locking rib 52 abuts the first engagement section 61, and as the counterpart 50 is further moved or inserted into the receptacle 43, the detection sleeve 60 is axially displaced in the insertion direction by the engagement of the locking rib 52 with the first engagement section 61.

[0047] Furthermore, the locking element 44 has an inclined surface 44a, which is arranged on the proximal side of the locking element 44 and thus faces the locking rib 52. When the counterpart 50 is inserted, a distal surface 52a of the locking rib 52 abuts the inclined surface 44a of the locking element 44, causing the locking element 44 to deform elastically radially outwards, so that the locking rib 52 of the counterpart 50 passes through the locking element 44 and a proximal surface 52b of the locking rib 52 can engage with a distal side or surface 44b of the locking element 44, as shown in Fig. Figure 6 shows that the locking element 44 locks the counterpart 50 via engagement with the locking rib 52.

[0048] As above with reference to Fig. 1 and Fig. As already described in section 2, the tab 45 extends over a partial circle of the circumference of the second housing part 40 and has the locking element 44 at its free end. Thus, the locking element 44 is radially movable and elastically pre-tensioned so that, when the counterpart 50 is inserted into the receptacle 43, its inclined surface 44a abuts the locking rib 52. Although the locking element 44 is brought into engagement with the locking rib 52 essentially radially by the tab 45 in an elastic manner, the locking element 44 can also be radially pre-tensioned in another way, for example by a spring.

[0049] As further explained in Fig. As shown in Figure 5, the detection sleeve 60 is in the not fully inserted state of the counterpart 50 in the original position, in which the detection section 64 is substantially completely received in the guide groove 48, so that the detection section 64 is not visible from the outside.

[0050] The term "not visible from the outside" means that the lateral surface of the detection section 64 is not visible when the fluid coupling is viewed radially, i.e., perpendicular to the pipe axis R, although a distal tip of the detection section 64 is visible when the fluid coupling is viewed axially from the distal side. However, the visibility of this small distal tip should be disregarded here because, in confined installation spaces in a motor vehicle, it could only be detected with a mirror and flashlight, which is precisely what should be avoided.

[0051] When the counterpart 50 is fully inserted into the receptacle 43 of the second housing part 40, the counterpart 50 is locked in the second housing part 40 by the engagement of the proximal surface 52b of the locking rib 52 with the distal surface 44b of the locking element 44. Furthermore, the detection sleeve 60 is displaced in the insertion direction by the engagement between the locking rib 52 and the first engagement section 61, so that the detection section(s) 64 protrude distally from the guide groove 48 in the insertion direction and become visible from the outside. In this way, a technician can easily visually detect the fully locked state of the fluid coupling.

[0052] As further explained in Fig. As shown in Figure 6, the second engagement section 62 is deformed radially inwards by the engagement with the guide groove 48 in order to engage with the proximal side or surface 52b of the locking rib 52. In this way, the fluid coupling can be unlocked via the handle 46 (see Figure 6). Fig. 1), which disengages the locking element 44 from the locking rib 52, the detection sleeve 60 is moved into its original position against the insertion direction by the second engagement section 62 bearing against the locking rib 52 when the counterpart 50 is pulled out of the receptacle 43.

[0053] In its original position, the second engagement section 62 is elastically deformed radially outwards to clear the path for the removal of the counterpart 50 with the locking rib 52. In other words, as in Fig.As shown in Figure 5, the second engagement section 62 deforms radially outwards so as not to obstruct the locking rib 52 when the counterpart 50 is pulled out of the receptacle 43.

[0054] Preferably, both the housing 20 and the detection sleeve 60 are made of a thermoplastic, such as PA 6, PA 6.6 or PA 12. The housing 20 and the detection sleeve 60 preferably have different colors to facilitate the visual detection of the detection section 64.

[0055] For example, the housing 20 may be made of a light-colored plastic, while the detection sleeve 60 may be made of a dark-colored plastic, or vice versa.

[0056] Although the detection sleeve 60 described here is designed in the semicircular shape with the detection sections 64 arranged around the circumference, the detection sleeve can also be designed as a tubular sleeve, with a front or distal section in the insertion direction serving as the detection section.

[0057] Although the embodiments shown here have a two-part housing 20 of the fluid coupling, a one-piece or three- or four-part housing can also be used.

[0058] Although the locking element 44 described here is formed at the end of the elastically deformable tab 45 with the handle 46, another locking element, such as a spring-loaded locking element, can also be used.

[0059] Although the housing 20 and the counterpart 50 described here have the hose connection 32, 54 for connection with a rubber hose, they can also be designed as connection fittings for a fuel pump or fuel filter or have another type of hose or pipe connection.

[0060] Although the fluid coupling described here is primarily designed for fuel lines, its use is not limited to this, but can also be used for other fluid lines, such as coolant lines, windshield washer fluid lines, hydrogen lines, air lines and crankcase ventilation systems. Reference symbol list 1 socket part 3 first socket section 5 second sleeve section 7 Actuating element 8 Bridge 9 Bridge 10 Exclusion 11 tab 12 Locking element 14 Arrow 15 windows 20 cases 30 first housing part 31 angled connection fitting 32 Hose connection 34th recording 35 Seal 36 discs 40 second housing part 43rd entry 44 Locking element 44a inclined surface 44b distal surface 45 tab 46 handle 48 Guide groove 48a distal end 50 counterparts 52 locking rib 52a distal surface 52b proximal area 54 Hose connection 55 Fluid flow 60 Detection sleeve 61 first intervention phase 62 second intervention phase 62a Top or lead 64 Detection section 66 hooks R pipe axis

Claims

[1] Fluid coupling, especially for fluid-carrying lines in motor vehicles, comprising: a housing (20) which has a receptacle (43) for a counterpart (50), a locking element (44) which is arranged in or on the receptacle (43) and which can engage a locking rib (52) of the counterpart (50) in such a way that the counterpart (50) is fixed in the axial direction in the receptacle (43), and a detection sleeve (60) which is arranged to be axially displaceable in the receptacle (43) and which has at least a first engagement section (61) which, when the counterpart (50) is inserted, can engage with the locking rib (52) in such a way that the detection sleeve (60) is axially displaced from an initial position in the insertion direction of the counterpart (50) towards a detection position, and which has at least a second engagement section (62) which is arranged behind the first engagement section (61) in the insertion direction and, when the counterpart (50) is withdrawn, can engage with the locking rib (52) in such a way that the detection sleeve (60) is axially displaced from the detection position opposite to the insertion direction of the counterpart (50) towards the initial position, wherein the detection sleeve (60) has at least one detection section (64) which in the initial position is received within the receptacle (43) such that the detection section (64) is not radially visible from the outside, and in the detection position protrudes from the receptacle (43) such that the detection section (64) is visible from the outside, and wherein the detection section (64) is designed as a guide rail to guide the detection sleeve (60) axially displaceably in guide grooves (48) of the housing (20), so that the detection sleeve (60) is displaceable within the receptacle (43) of the housing (20) in the axial direction of the fluid coupling. [2] Fluid coupling according to claim 1, wherein the second engagement section (62) is elastically deformable and is in the initial position of the detection sleeve (60) in the undeformed state and in the detection position in the elastically deformed state, wherein the second engagement section (62) can only engage with the locking rib (52) in the deformed state. [3] Fluid coupling according to one of the preceding claims, wherein the first engagement section (61) has the shape of a partial circle or a complete circular shape, and / or the second engagement section (62) is formed at a rear end of the detection section (64) in the insertion direction. [4] Fluid coupling according to one of the preceding claims, wherein the locking element (44) is movable and elastically prestressed substantially orthogonal to the insertion direction and has an inclined surface (44a) such that the locking element (44) is elastically deflected when the counterpart (50) is inserted by the contact between the locking rib (52) of the counterpart (50) and the inclined surface (44a). [5] Fluid coupling according to claim 4, wherein the elastic restoring force of the locking element (44) moves the counterpart (50) over the inclined surface (44a) in the opposite direction of insertion when the locking element (44) is incompletely inserted into the receptacle (43). [6] Fluid coupling according to one of the preceding claims, wherein the detection sleeve (60) has at least one elastically restorable hook (66) which can engage with the housing (20) when the detection sleeve (60) is inserted, or the housing (20) has locking means, such as elastically restorable hooks, which can engage with the detection sleeve (60) so that the detection sleeve (60) is axially displaceably secured in the housing (20). [7] Fluid coupling according to claim 6, wherein the at least one hook (66) is arranged on at least one detection section (64) at its forward end in the insertion direction. [8] Fluid coupling according to one of the preceding claims, wherein the housing (20) is formed in two parts, wherein a second housing part (40) has the receptacle (43), the locking element (44) and the detection sleeve (60), and a first housing part (30) can be connected to the second housing part (40) at different angles of rotation and has an angled connecting nozzle (31). [9] Fluid coupling according to the previous claim, wherein at least the detection section (64) of the detection sleeve (60) has a different color than the second housing part (40). [10] Fluid coupling according to one of the preceding claims, wherein the housing (20) and / or the locking element (44) and / or the detection sleeve (60) are made of a thermoplastic, such as PA6, PA6.6, PA12. [11] Combination of a fluid coupling according to one of the preceding claims and a counterpart (50), wherein the counterpart (50) is tubular and the locking rib (52) is formed as a radially projecting collar. [12] Method for connecting two fluid lines, in particular fluid-carrying lines in motor vehicles, comprising the steps: Providing a housing (20) which is designed with a receptacle (43) for a counterpart (50), Providing a counterpart (50) with a locking rib (52), Providing a locking element (44) which is arranged in or on the receptacle (43) and which can engage behind the locking rib (52) of the counterpart (50) in such a way that the counterpart (50) is fixed in the axial direction in the receptacle (43), and Providing a detection sleeve (60) which is arranged to be axially displaceable in the receptacle (43) and which has at least a first engagement section (61) which, when the counterpart (50) is inserted, engages with the locking rib (52) such that the detection sleeve (60) is axially displaced from an initial position in the insertion direction of the counterpart (50) into a detection position, and which has at least a second engagement section (62) which is arranged behind the first engagement section (61) in the insertion direction and, when the counterpart (50) is withdrawn, engages with the locking rib (52) such that the detection sleeve (60) is axially displaced from the detection position opposite to the insertion direction of the counterpart (50) into the initial position. wherein the detection sleeve (60) is formed with at least one detection section (64) which in the initial position is received within the receptacle (43) in such a way that the detection section (64) is not visible radially from the outside, and in the detection position protrudes from the receptacle (43) in such a way that the detection section (64) is visible from the outside, wherein the detection section (64) is designed as a guide rail to guide the detection sleeve (60) axially displaceably in guide grooves (48) of the housing (20), so that the detection sleeve (60) is displaceable within the receptacle (43) of the housing (20) in the axial direction of the fluid coupling, Inserting the counterpart (50) into the housing (20), and Detect whether the detection section (64) is visible.

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