Fuel rail with coated screw-in element

Abstract

The utility model relates to a fuel rail (100), especially a fuel rail for a fuel injection system of an internal combustion engine. The fuel rail comprises a base body (102) and at least one screw-in element (109). The base body (102) has at least one screw-in region (108) with an internal thread (202) and a sealing seat (208). The screw-in element (109) has an external thread (204). The screw-in element (109) is screwed with its external thread (204) into the internal thread (202) of the screw-in region (108). The screw-in element (109) has a sealing surface (206) which rests against the sealing seat (208). The base body (102) and the screw-in element (109) are made of stainless steel, wherein at least the sealing surface (206) and / or the external thread (204) of the screw-in element (109) have a coating with a molybdenum disulfide sliding paint.

Description

Technical Field

[0001] This invention relates to a fuel rail with a coated screw-in element, particularly for a fuel rail in the injection system of an internal combustion engine. Background Technology

[0002] Fuel rails are known in principle in the prior art. Fuel rails are used in the injection systems of internal combustion engines. The fuel rail delivers fuel compressed by a high-pressure pump to the injectors and also serves as a high-pressure fuel reservoir. In many cases, the base of the fuel rail is manufactured by forging. After forging, a cavity for the fuel is created by deep-hole drilling. The open ends of the cavity are typically closed by a sealing screw or fitted with an adapter. For this purpose, the fuel rail typically has internal threads into which the external threads of the sealing screw can be screwed. To ensure the required seal, the sealing screw has a sealing face that abuts against a sealing seat formed within the fuel rail. As the sealing screw is screwed in, relative movement occurs between the sealing face of the screw and the sealing seat of the fuel rail.

[0003] In gasoline engines, stainless steel is typically used as the material due to the presence of ethanol in the fuel. However, especially when stainless steel fuel rails are used in conjunction with stainless steel sealing screws, friction corrosion or cold welding can still occur on the sealing surfaces, even if the sealing screws are lubricated. This can lead to a leak. To detect any leaks, mass-produced fuel rails are typically subjected to a leak test (sniffing test) using a test gas (such as helium).

[0004] However, the test gas must leak out through the threads of the screw-in component to be detected by the sensor. Furthermore, any residual installation oil in the threads may prevent the test gas from escaping through the threads within the required test time. Therefore, leak tests are sometimes unreliable in determining the fuel rail's seal.

[0005] According to German patent DE 10 2017 122 301 B3, it is known to integrate a sniffing hole into a sealing screw to improve the identification of unsealed leaks during leak testing. Test gas can escape directly through the sniffing hole without passing through the thread. However, this only improves the identification of unsealed leaks, without improving the seal itself.

[0006] A fuel rail is known from German patent DE 10 1060 203 650 A1, in which the sealing surface of the sealing screw is constructed to be more flexible by means of a stress-relieving groove (Freimachung) within the sealing screw, in order to achieve a better and, in particular, more reliable seal. However, it should be recognized that this problem is not completely solved, because there is still always direct relative movement between the materials of the sealing screw and the fuel rail.

[0007] According to Japanese Patent JP2007170581 A, a fuel rail is known, which has a closed screw with a low-friction coating, the coating comprising carbon nanomaterials. Summary of the Invention

[0008] The technical problem this invention aims to solve is to provide a fuel rail with an improved seal compared to existing technologies, manufactured with higher process safety, or at least an alternative embodiment of the fuel rail. Furthermore, this invention achieves improved detectability of leaks in leak tests.

[0009] The fuel rail according to this invention (particularly for fuel rails in injection systems of internal combustion engines) comprises a base and at least one screw-in element. The base has at least one screw-in region with internal threads and a sealing seat. The screw-in element has external threads. The screw-in element is screwed into the internal threads of the screw-in region with its external threads. The screw-in element has a sealing surface (after the screw-in element is screwed into the screw-in region) abutting against a sealing seat formed in the base. The sealing surface and / or threads of the screw-in element are at least coated.

[0010] The coating is used to ensure that the sealing surfaces and / or threads have low and constant friction values. By coating the sealing surfaces of the screw-in element, frictional corrosion between the sealing surfaces of the screw-in element and the sealing seat on the substrate can be avoided. Both the coating on the sealing surfaces and the coating on the threads help to provide suitable and reproducible friction values ​​during the screwing process, and thus help to achieve constant preload in the threaded connection. This improves the process stability and reliability of the installation process, as well as the sealing performance.

[0011] Furthermore, using a coating instead of lubrication or omitting thread lubrication improves the detectability of unsealed leaks in leak tests because there is no need to squeeze lubricant out of the threads.

[0012] A fuel rail (Kraftstoff-Rail) is also known as a fuel distributor (Kraftstoffverteiler), fuel distribution rail (Kraftstoffleiste), distributor rail (Kraftstoffleiste), or injection manifold (Einspritzleiste). Fuel rails are particularly useful for receiving liquid or gaseous fuels, propellants, or working media. For example, a fuel rail can receive gasoline, diesel, methanol, natural gas, ammonia, or hydrogen.

[0013] The fuel rail can be used to deliver fuel compressed by a high-pressure pump to the injector, and also serves as a high-pressure fuel storage device. The fuel rail can also be used as a fuel distributor for gas cylinders, particularly those containing natural gas or hydrogen.

[0014] The spiral region can also be called the closed region or the connecting region.

[0015] The sealing surface within the substrate can also be referred to as a sealing chamfer. Screw-in elements can be, for example, sealing screws, connectors, adapters, or pressure sensors. Screw-in elements are used to seal the substrate relative to the external environment or to achieve connection with other screw-in or rotary elements that have different connection geometry.

[0016] The base of the fuel rail is made of stainless steel. For example, in gasoline engines, stainless steel must be used to prevent corrosion because the fuel contains ethanol. The stainless steel can be, for example, austenitic stainless steel 1.4301 or 1.4307.

[0017] The screw-in element is made of stainless steel. When a stainless steel base and a stainless steel screw-in element are used together, the risk of frictional corrosion between the sealing surface of the screw-in element and the sealing seat on the base increases. The stainless steel of the fuel rail base and the stainless steel of the screw-in element can be different steels. The materials of the base and the screw-in element can also have different material hardness.

[0018] The screw-in element can be a sealing screw. For example, a screw-in element can seal an opening formed on the end of the base through a deep-hole drill. The screw-in element can also be an adapter for, for example, connecting a high-pressure line. The screw-in element can also be a pressure sensor. The pressure sensor can be mounted on one of the two ends of the fuel rail, or it can be mounted on the side of the fuel rail.

[0019] The manufacturing process of the substrate can include forging. For example, the manufacturing process can include forging and machining. For example, cavities within the substrate can be created by deep hole drilling. Deep hole drilling is a machining process. In addition to deep hole drilling, the manufacturing process can also include other machining processes. Besides forged fuel rails, so-called welded fuel rails are also known in principle, where the fuel rail is assembled from multiple independent components. The concept of coating is also generally applicable to this welded fuel rail.

[0020] The coating on the screw-in element is a sliding varnish. The sliding varnish is understood to be a solid lubricant—typically molybdenum disulfide (MoS2), graphite, or polytetrafluoroethylene (PTFE)—embedded in an organic or inorganic binder. The sliding varnish is used to prevent cold welding, even under high surface pressure, and to achieve predetermined, calculable frictional characteristics. Preferably, a high-temperature resistant and fuel-resistant sliding varnish is used. Due to environmental requirements, a sliding varnish that does not contain PTFE as a solid lubricant is preferred. To prevent the screw-in element from automatically loosening due to vibration, it is advantageous to use a sliding varnish whose friction value does not decrease excessively.

[0021] The coating of the screw-in element contains molybdenum disulfide (MoS2). Molybdenum disulfide (MoS2) can be incorporated into organic or inorganic binders. The coating can also contain other materials.

[0022] Screw-in components can be fully coated, for example, when the screw-in component is a closed screw. However, screw-in components can also be partially coated. For example, only the sealing surface and the threads can be coated. Alternatively, only the sealing surface can be coated. Alternatively, only the threads can be coated. Alternatively, only a defined area of ​​the threads can be coated. Surfaces in contact with fuel can also be intentionally left uncoated.

[0023] The coating on screw-in components can be applied using a spraying method. Unlike roller coating, spraying offers the advantage of eliminating the risk of damage to the sealing surface and allowing for partial coating. In spraying, metered spraying can be used to achieve a defined coating thickness. Spraying is also known as painting.

[0024] The coating thickness of screw-in components can range from 4 µm to 40 µm, particularly from 4 µm to 20 µm, and especially from 4 µm to 12 µm. Specifically, due to the threads, the coating thickness on the threads may vary at different locations on the threads. For example, the coating thickness of a screw may be only 4 µm at a certain location, while at other locations it may be up to 12 µm, with an average coating thickness of 8 µm.

[0025] For manufacturing a fuel rail, particularly for a fuel rail used in an injection system of an internal combustion engine, a substrate and at least one screw-in element are provided. The substrate has at least one screw-in area with internal threads and a sealing seat. The screw-in element has external threads and a sealing surface. At least the sealing surface and / or external threads of the screw-in element, or at least the sealing seat and / or internal threads of the substrate, are coated. The screw-in element is screwed into the substrate. At the coated location, the coating can act as a lubricant during screw-in and prevent or reduce direct relative movement between the materials of the substrate and the screw-in element.

[0026] The sealing surface and the sealing seat do not necessarily have to be two parallel, opposing planes. These two surfaces (the sealing surface and the sealing seat) can have different shapes, such that at least one surface undergoes plastic deformation when the screw-in element is screwed in, thus forming a seal. For example, the sealing surface can consist of at least two separate sealing surfaces / seal chamfers with different taper angles, which intersect to form a ridge. For example, the sealing surface can be constructed as convex. For example, the sealing seat can be constructed as convex. For example, both the sealing surface and the sealing seat can be constructed as convex. Although the sealing surface of the screw should abut against the sealing seat in a 360° arc when screwed in to achieve a seal, this does not mean that the entire sealing surface must abut against the sealing seat in a planar manner.

[0027] In principle, a sealing ring can also be used between the screw-in element and the fuel rail substrate. In principle, a coating can also be considered for this sealing ring. Attached Figure Description

[0028] The concept of this utility model will now be described in more detail with reference to the accompanying drawings. However, the following description is to be considered exemplary only. This utility model is defined only by the subject matter of the claims. Advantageous embodiments of this utility model will now be explained in conjunction with the accompanying drawings. Here, the same reference numerals are used to denote the same or functioning elements. In addition, reference numerals are also used for features not shown in the figures for ease of reading and identification. Similarly, if these features are clearly identified from the preceding figures, not all reference numerals are always drawn in similar figures. The figures are as follows: Figure 1 A cross-sectional view of a fuel rail according to an embodiment of the present invention is shown; Figure 2 Show Figure 1 Enlarged view of section A in the image; Figure 3 The sealing screw of the fuel rail according to an embodiment of the present invention is shown; Figure 4 A schematic illustration of a vehicle with an engine having a fuel rail according to an embodiment of the present invention is shown. Figure 5 A flowchart is shown for a method of manufacturing a fuel rail according to an embodiment of the present invention. Detailed Implementation

[0029] Figure 1 The fuel rail is shown, comprising a base 102, two screw-in regions 108, and two screw-in elements 109. The screw-in elements 109 are a sealing screw 110 and a pressure sensor 111, respectively. Furthermore, the base 102 has a cavity 104, a connection 107 for a high-pressure fuel line, and multiple connections 106 for the injection valves. Fuel compressed by the high-pressure pump is introduced into the cavity 104 through the high-pressure fuel line connection 107, and from there delivered to the respective injection valves through the connections 106. The cavity 104 serves as a fuel reservoir to compensate for pressure fluctuations.

[0030] Figure 2 Show Figure 1 An enlarged view of section A. The base has a screw-in region 108 with internal threads 202. The screw-in element 109 is a sealing screw 110. The sealing screw 110 has external threads 204 and is screwed into the base 102. The base 102 has a sealing seat 208. The sealing screw 110 has a sealing surface 206. The threaded connection achieves the face pressure required for a seal between the sealing surface 206 and the sealing seat 208.

[0031] Figure 3A sealing screw 110 with external threads 204 and a sealing surface 206 is shown. The sealing surface 206 is tapered, wherein the sealing surface 206 has two different taper angles (sealing chamfer 210 and sealing chamfer 212).

[0032] Figure 4 A schematic diagram of a vehicle 400 and its internal combustion engine 402 is shown. According to an embodiment of the present invention, a fuel rail 100 with a sealing screw 110, four injection valves 406, and a high-pressure pump 408 are part of the internal combustion engine 402. The high-pressure pump 408 is connected to the fuel rail 100 via a fuel line 410.

[0033] Figure 5 A flowchart illustrates a method for manufacturing a fuel rail, particularly for an injection system of an internal combustion engine. The method includes at least steps S1 to S4. In step S1, a substrate is provided. In step S2, at least one screw-in element is provided. In step S3, a coating is applied. The sealing surface of the screw-in element can be coated. Alternatively or additionally, the external threads of the screw-in element can also be coated. As an alternative to applying the coating to the screw-in element, the coating can be applied to the substrate. For this purpose, the sealing surface of the screw-in area can be coated. Alternatively or additionally, the internal threads can also be coated. In step S4, the screw-in element is screwed into the substrate such that the sealing surface at least partially abuts against a sealing seat, and alternatively or additionally, the sealing surface at least partially penetrates into the sealing seat, thereby deforming the sealing surface and, alternatively or additionally, partially the sealing seat. By screwing in, the cavity within the substrate is sealed relative to the surrounding fluid environment.

[0034] List of reference numerals 100 fuel rail 102 matrix 104 Cavity 106 Connection part for injection valve 107 Connection part for high-pressure oil pipe 108 Rotation Zone 109 Screw-in element 110 Sealing Screw 111 Pressure Sensor 202 Internal Thread 204 external thread 206 Sealing Surface 208 Sealing seat 400 vehicles 402 Internal Combustion Engine 404 fuel tank 406 Injector 408 High Pressure Pump 410 Fuel Line

Claims

1. A fuel rail (100) comprising: A base (102) and at least one screw-in element (109), wherein the base (102) has at least one screw-in region (108) with an internal thread (202) and a sealing seat (208); the screw-in element (109) has an external thread (204); the screw-in element (109) is screwed into the internal thread (202) of the screw-in region (108) with its external thread (204); the screw-in element (109) has a sealing surface (206) abutting against the sealing seat (208); the base (102) and the screw-in element (109) are made of stainless steel, characterized in that: at least the sealing surface (206) and / or the external thread (204) of the screw-in element (109) have a coating with molybdenum disulfide sliding paint.

2. The fuel rail (100) according to claim 1, wherein, The fuel rail (100) is the fuel rail for the injection system of an internal combustion engine.

3. The fuel rail (100) according to claim 1, wherein, The fuel rail (100) is used to receive gasoline.

4. The fuel rail (100) according to claim 1, wherein, The screw-in element (109) is a closing screw (110).

5. The fuel rail (100) according to any one of claims 1 to 4, wherein, The manufacturing process of the substrate (102) includes forging.

6. The fuel rail (100) according to any one of claims 1 to 4, wherein, The coating of the screw-in element (109) is applied by spraying.

7. The fuel rail (100) according to any one of claims 1 to 4, wherein, The coating thickness of the screw-in element (109) is between 2 μm and 40 μm.

8. The fuel rail (100) according to any one of claims 1 to 4, wherein, The coating thickness of the screw-in element (109) is between 4 μm and 20 μm.

9. The fuel rail (100) according to any one of claims 1 to 4, wherein, The coating thickness of the screw-in element (109) is between 4 μm and 12 μm.

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