CN220353971U

CN220353971U - Fuel return device for fuel injection system

Info

Publication number: CN220353971U
Application number: CN202321181592.2U
Authority: CN
Inventors: M·博施卡
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2022-05-16
Filing date: 2023-05-16
Publication date: 2024-01-16
Anticipated expiration: 2033-05-16
Also published as: DE202022102687U1

Abstract

A fuel return device for a fuel injection system has a return hose with a cylindrical wall, which has an inner layer, an intermediate layer, a textile layer and an outer layer, viewed from the inside outwards, and a plug, which can be connected to a fuel-conducting component of the fuel injection system and on which a connecting sleeve is formed, onto which the return hose is plugged. The connecting sleeve is oriented perpendicularly to the longitudinal direction, and the connecting sleeve is configured to be inserted into the receiving opening of the fuel-conducting component in the longitudinal direction until the connecting sleeve is pressed with the abutment surface against the shoulder of the fuel-conducting component. The distance between the contact surface and the connecting sleeve is greater than or equal to the wall thickness of the return hose.

Description

Fuel return device for fuel injection system

Technical Field

The utility model relates to a fuel return device for a fuel injection system, wherein the fuel injection system is designed to introduce fuel directly or indirectly into a combustion chamber of an internal combustion engine.

Background

A fuel injection system for introducing fuel directly into the combustion chamber of an internal combustion engine operates according to the following principles: the highly compressed fuel is introduced directly into the combustion chamber through the injection openings of the injectors. In this case, the fuel is atomized by the high injection pressure and forms a combustible air-fuel mixture which self-ignites in the combustion chamber by a high compression ratio in a diesel engine. The opening and closing of the injection opening takes place by means of a movable nozzle needle which is operated in a servo-hydraulic manner, i.e. the fuel pressure in the control chamber is lowered and raised by means of a control valve and the nozzle needle is moved in the longitudinal direction by means of a varying hydraulic pressure. For this purpose, a small fuel quantity, the so-called control quantity, must flow out of the control chamber when the pressure drops, said control quantity being relieved in this case and being fed back into the fuel tank via the fuel return device. Furthermore, depending on the type of injector, fuel produced by leakage may also occur, which is likewise conducted back into the fuel tank via the fuel return line.

In order to guide the fuel back into the fuel tank or into the region of the fuel injection system where there is a low pressure, the injectors of most fuel injection systems are connected to a common fuel return line. For this purpose, each injector has a receptacle for a plug, which plugs are connected to one another by a flexible return hose. The end of the return line ends up in a further low-pressure region of the fuel tank or of the fuel injection system, wherein a check valve is also provided in the return line for the most part, which check valve keeps the pressure in the fuel return device at a defined level, for example at 5 or 10 bar. There is a much lower pressure in the return line than in the high-pressure region of the fuel injection system, but the pressure is significantly higher than the ambient pressure. By changing the operating state of the engine and switching on and off, pressure fluctuations and pulsations also occur in the fuel return system, which require corresponding robustness and pressure resistance.

DE 103 60 a1 discloses a fuel return device for a fuel injection system in which each injector is connected to a plug and the plugs are connected to one another by flexible hoses. The hose has the necessary flexibility on the one hand and the necessary tightness and fuel resistance on the other hand. The hose end is pushed onto a line connection which is formed on the plug in order to establish a tight connection.

Disclosure of Invention

The fuel return apparatus for a fuel injection system according to the present utility model has the following advantages: the 4-layer return hose is connected to the associated plug, so that a flexible and fuel-resistant return hose can be used between the individual plugs and the functionality is ensured during the service life of the fuel injection system. For this purpose, the fuel return device has a return hose with a cylindrical wall, through which fuel can be introduced into the fuel tank. The wall has an inner layer, an intermediate layer, a fabric layer and an outer layer, seen from the inside outwards. Furthermore, the fuel return device comprises a plug which can be connected to the fuel-conducting component of the fuel injection system and on which a connecting sleeve is formed, onto which the return hose is plugged. A line connection is also formed on the plug, which line connection can be inserted into the receiving opening of the fuel-conducting component in the longitudinal direction until the plug rests against a shoulder of the fuel-conducting component, wherein the connecting sleeve is oriented perpendicularly to the longitudinal direction. The distance between the contact surface and the connecting sleeve is greater than or equal to the wall thickness of the return hose.

The spacing between the contact surface and the connecting sleeve according to the utility model allows the use of a return hose which has four layers and which shows the advantages associated therewith, such as sufficient flexibility and resistance to fuels, such as diesel fuel or gasoline fuel. In this case, a problem-free assembly of the hose to the plug is possible despite the relatively thick wall, without blocking the plug in the receiving opening of the fuel-conducting component.

In an advantageous embodiment of the utility model, a plug finger is formed on the plug, which plug finger is oriented parallel to the connection sleeve, wherein a distance exists between the plug finger and the connection sleeve, which distance is greater than or equal to the wall thickness of the return hose. In this case, a plug is understood to mean the protection of the connection sleeve and the return hose from mechanical influences.

In a further advantageous embodiment of the utility model, the fuel return device comprises a return hose having a plurality of line sections which connect a plurality of plugs to one another in pairs, so that a communicating return line is formed. Correspondingly, the plug connected to the two further plugs has two connection bushings, whereas only one connection bushing is present on the plug at the end of the fuel return line.

In a further advantageous embodiment, the inner layer of the return hose is formed from an elastic material, in particular rubber, particularly preferably fluororubber. Fluororubbers have, in addition to good elastic properties, also high temperature resistance and good resistance to mineral oil, so that the durability of the return hose is ensured.

In a further advantageous configuration, the intermediate layer is formed from a rubber product, in particular an acrylate-ethylene-rubber (AEM). The rubber product serves for stabilization of the inner layer and ensures the necessary flexibility of the return hose.

Preferably, the following fabric layers are formed from interwoven threads which tangentially surround the middle layer of the wall. The lines may also run obliquely or be arranged crosswise. Preferably, the wire is formed of an aramid having a very high tensile strength and imparting the necessary compressive strength to the hose so as to withstand the fuel pressure permanently even in the event of stronger pressure fluctuations.

The outer layer surrounding the fabric layer is preferably made of a firm elastomeric material. The material serves on the one hand to stabilize the textile layer and on the other hand to protect the textile layer from external influences, in order to prevent damage to the threads and thus to prevent impairment of stability.

In a further advantageous embodiment, the connecting sleeve is configured cylindrically and has a conical surface at the outer end of the connecting sleeve. The conical surface simplifies the displacement of the return tube, prevents damage during assembly and increases the withdrawal force of the return tube, so that the return tube is fixed in its assembled position.

In a further advantageous embodiment, at least one circumferential sealing bead, preferably two sealing beads spaced apart from one another, is formed on the connecting sleeve. The sealing flange serves to provide an improved sealing of the return hose on the connecting sleeve and to promote the press fit of the return hose, without additional fastening elements, such as a hose clamp, being required for this purpose.

Drawings

In the drawings, an embodiment of a fuel return arrangement according to the utility model is shown. In the drawings of which there are shown,

figure 1 shows in a schematic view a fuel injection system with a fuel return,

figure 2 shows the return hose in a partly cut-away view,

fig. 3 shows a plug with two connection bushings, showing how the plug is connected with one of the fuel-supplying parts,

figure 4 shows the same plug as in figure 3 in a perspective view,

fig. 5 shows a plug with only one connecting sleeve, which forms the end of the fuel return line, and

fig. 6 shows a further embodiment of a plug with two connection bushings and with plug fingers.

Detailed Description

In fig. 1 a fuel injection system 1 is schematically shown. The fuel injection system 1 for metering fuel into a combustion chamber or combustion chambers of an internal combustion engine comprises a fuel tank 2 in which the fuel to be injected is maintained at ambient pressure. The fuel is supplied from the fuel tank 2 via the front feed pump 3, the fuel line 5, the filter 6 and the high-pressure pump 7 to a high-pressure rail 8, at which the fuel compressed by the high-pressure pump 7 is maintained at a predetermined injection pressure, for example 2000 bar (200 MPa). In order to redirect (absteuern) the excessively supplied fuel back into the fuel tank and to limit the pressure in the fuel line 5, a return line (Absteuerleitung) 17 is provided with a return valve 4, which connects the fuel line 5 to the fuel tank 2. For the injection of fuel, three injectors 10 are present in the fuel injection system 1, which form the fuel-conducting component, for example. From the high-pressure rail 8, a connecting line 9 leads to an injector 10, through which compressed fuel is supplied. The compressed fuel is introduced into the respective combustion chamber of the internal combustion engine at the correct point in time by the opening and closing of the injector 10 through the injection opening 110 in the injector 10 and is combusted there. Here, the control of the injector 10 takes place in a servo-hydraulic manner, i.e. the longitudinal movement of the nozzle needle opening the injection opening 110 is controlled by the hydraulic pressure in the control chamber, wherein the nozzle needle is not shown in the drawing of fig. 1. This control principle is well known from the prior art.

In order to reduce the pressure in the control chamber, fuel is returned from the control chamber, the fuel is discharged here and the control quantity is discharged via the return connection 20. The injectors are connected to plugs 12, 13 of the fuel return 11 via return connection 20. For this purpose, receiving openings 29 for the plugs 12, 13 are formed on the return connection 20. The plug 12 at the outermost injector 10 is embodied as an L-shaped plug 12 with one connecting sleeve 30, while the remaining plug 13 is embodied in a T-shaped manner with two connecting sleeves 30. The plugs 12, 13 are connected to one another by a return hose 15 or by a line section 16 of the return hose 15 and thus form a communicating fuel return line. The fuel in the return line 15 is finally led back into the fuel line 5 between the front feed pump 3 and the high-pressure pump 7 via a pressure regulating valve 21, which is maintained at a defined pressure level in the return line 15.

A connecting sleeve 30 is formed on the L-shaped plug 12, and two connecting sleeves 30 opposite each other are formed on the T-shaped plug 13, to which the respective return hoses 15 or line sections 16 are pushed. In this exemplary embodiment, in order to protect the connection sleeve 30 and the hose 15, a so-called plug finger (Steckerfinger) 14 is formed on the plugs 12, 13. The plug fingers are oriented parallel to the connection sleeve 30 and protect the return tube 15 and the respective connection sleeve 30 from mechanical influences and serve as pressure surfaces during assembly of the plugs 12, 13.

The return hose 15 is shown enlarged in a partially cut-away view in fig. 2. The return hose 15 consists of 4 layers: an inner layer 24, an intermediate layer 25, a fabric layer 26 and an outer layer 27, which concentrically surround a cylindrical pipe volume 28. The inner layer 24 is composed of an elastomeric material such as rubber (Kautschuk), in particular fluororubber. Fluororubbers have, in addition to good elastic properties, also high temperature resistance and good resistance to mineral oils, in particular diesel or gasoline fuels and other organic solvents. For further stabilization of the return hose 15 and as a basis for the textile layer 26, an intermediate layer 25 is used, which is formed from a rubber product (Gummi), preferably from an acrylate-ethylene-rubber (AEM). AEMs are characterized by good elastic properties and resistance to fuels, such as gasoline fuels or diesel fuels. In addition, AEMs are resistant to heat and cold and have good impact absorption properties. A fabric layer 26 is applied to this intermediate layer 25, said fabric layer serving to strengthen the return hose 15. The fabric layer 26 consists of fibers, for example aramid fibers, which are alternately wound tangentially around the hose 15 in layers and thus interweave with one another. By using a plurality of layers, the fibers of which are inclined relative to one another and thus form a tight fabric, the fabric layer is fixed and the return hose is stabilized against internal pressure. To protect the fabric layer 26, the fabric layer is also wrapped by an outer layer 27. The outer layer 27 serves to protect the fabric layer 26 from damage and is preferably composed of an elastomeric material. The wall 23 of the return hose 15 thus formed has a thickness d.

Fig. 3 shows the T-shaped plug 13 in a longitudinal section in the installed position on the injector 10, wherein the injector 10 is only partially shown. The plug 13 has a line connection 22, via which the plug 13 is guided in the longitudinal direction R into a receiving opening 29 in the injector 10 and in the process rests against the annular shoulder 19 via the contact surface 18. In order to lock the plug 13 to the injector, a securing clip 31 is introduced into a groove on the injector 10, which engages in the groove on the plug 13 and prevents the latter from being pulled out of the receiving opening 29 inadvertently. The distance a between the connecting sleeve 30 and the contact surface 18 is determined here to be greater than or equal to the wall thickness d of the return tube 15, so that the return tube 15 does not interfere with the assembly of the fastening clip 31 and the return tube 15 cannot be inadvertently clamped between the shoulder 19 and the contact surface 18. At the ends of the connecting sleeve 30, conical surfaces 33 are each formed, which simplify the displacement (aufskieben) of the return tube 15 and increase the extraction force of the return tube 15 from the connecting sleeve 30 by means of the side recesses (hinterschnit) formed in this way. The return hose 15 is pushed onto the connecting sleeve 30 until it rests against the end face 35 of the plug 12.

Fig. 4 shows the same plug 13 as in fig. 3 in a perspective view, so as to illustrate the manner of operation of the fixing clip 31.

Fig. 5 shows a side view of a further exemplary embodiment of the plug 12 together with the return hose 15 to be fitted. The L-shaped plug 12 shown here forms the end of the return line and accordingly has only one connecting sleeve 30. In order to improve the seal between the inner wall of the return tube 15 and the connecting sleeve 30, two sealing flanges 32 are formed on the connecting sleeve 30, which sealing flanges are spaced apart from the conical surface 33. The sealing flange improves the seal between the inner wall of the return hose 15 and the connection sleeve 30 and promotes the press fit (Festsitz) of the return hose 15 on the connection sleeve 30.

Fig. 6 shows a further exemplary embodiment of a T-shaped plug 13 with two opposing connection bushings 30 in a side view. In this case, plug fingers 14 are formed on both sides parallel to the connecting sleeve 30, which plug fingers protect the connecting sleeve 30 and the return tube 15 from mechanical influences. The plug fingers 14 are also used for the assembly of the plugs 12, 13 in that the plugs 12, 13 are pushed into the receiving openings 29 by the pressure acting on the plug fingers 14. An axial distance a is provided between the connecting sleeve 30 and the plug finger 14 ₁ . The axial distance is greater than or equal to the wall thickness d of the return hose 15, in order to enable a problem-free assembly of the return hose 15.

Claims

1. A fuel return device (11) for a fuel injection system (1) has a return hose (15) with a cylindrical wall (23) having, seen from the inside outwards, an inner layer (24), an intermediate layer (25), a fabric layer (26) and an outer layer (27),

and having a plug (12; 13) which can be connected to a fuel-conducting component of the fuel injection system (1) and on which a connecting sleeve (30) is formed, to which the return hose (15) is plugged,

and having a line connection formed on the plug (12; 13) which can be introduced into the receiving opening of the fuel-conducting component in a longitudinal direction (R) until the plug (12; 13) rests with a contact surface (18) against a shoulder (19) of the fuel-conducting component, wherein the connecting sleeve (30) is oriented perpendicularly to the longitudinal direction (R),

characterized in that the distance (a) between the contact surface (18) and the connecting sleeve (30) is greater than or equal to the wall thickness (d) of the return tube (15).

2. The fuel return device (11) according to claim 1, characterized in that a plug finger (14) is formed on the plug (12; 13), which plug finger is oriented parallel to the connecting sleeve (30), wherein a distance (a) is present between the plug finger (14) and the connecting sleeve (30) ₁ ) The distance is greater than or equal to the wall thickness (d) of the return hose (15).

3. The fuel return (11) according to claim 1 or 2, characterized in that the return hose (15) comprises a plurality of line sections (16) through which a plurality of plugs (12; 13) are connected to one another in pairs, wherein the plug (13) connected to two further plugs (12; 13) has two connection bushings (30).

4. The fuel return (11) according to claim 1 or 2, wherein the inner layer (24) is formed of an elastomeric material.

5. The fuel return device (11) according to claim 1 or 2, wherein the intermediate layer (25) is formed of a rubber product.

6. The fuel return (11) according to claim 1 or 2, characterized in that the fabric layer (26) consists of intertwined and/or interwoven fibers or threads which tangentially surround the intermediate layer (25) of the wall (23).

7. The fuel return (11) according to claim 6, wherein the thread or fiber consists of aramid.

8. The fuel return (11) according to claim 1 or 2, wherein the outer layer (27) consists of a firm elastomeric material.

9. The fuel return (11) according to claim 1 or 2, characterized in that the connecting sleeve (30) is cylindrically configured and has a conical surface (33) on the outer end of the connecting sleeve.

10. The fuel return (11) according to claim 9, characterized in that at least one circumferential sealing flange (32) is formed on the connecting sleeve (30) at a distance from the conical surface (33).

11. The fuel return (11) according to claim 10, characterized in that two sealing flanges (32) are formed on the connecting sleeve (30).

12. The fuel return (11) according to claim 4, wherein the elastomeric material is rubber.

13. The fuel return (11) according to claim 12, wherein the rubber is a fluororubber.

14. The fuel return (11) according to claim 5 wherein the rubber article is an acrylate-ethylene-rubber.