Diesel engine double-wall high-pressure oil pipe sealing mechanism and sealing method thereof

Abstract

The application relates to a diesel engine double-wall high-pressure oil pipe sealing mechanism and a sealing method thereof. The sealing mechanism comprises an oil injector sealing cone, a ball head sealing cone, an inner wall positioning ring, a sealing rubber ring I, an outer wall positioning joint, a sealing copper pad, a sealing rubber ring II, a thrust ring, a locking joint and a double-wall pipe. The application adopts a three-stage sealing structure of a metal hard sealing of the oil injector sealing cone and the ball head sealing cone, plastic deformation sealing of the sealing copper pad and elastic sealing of the double-rubber sealing ring, forms a gradient sealing barrier from a high-pressure area to a low-pressure area, solves the problem that a single sealing form is prone to failure under a high-pressure pulse working condition, improves the safety of a high-pressure fuel system of a diesel engine through multi-stage sealing and function decoupling design, and can be widely applied to a high-pressure fuel injection system of a diesel engine.

Description

Technical Field

[0001] This application relates to the field of high-pressure common rail fuel delivery technology for diesel engines, and in particular to a sealing mechanism and sealing method for a double-walled high-pressure fuel pipe for diesel engines. Background Technology

[0002] With increasingly stringent diesel engine emission regulations and continuously improving engine power density, fuel system injection pressures have generally reached over 200 MPa. As a key component for high-pressure fuel delivery, the sealing reliability of high-pressure fuel lines directly affects the operational safety and emission performance of diesel engines. Double-walled high-pressure fuel lines, due to their leakage-guiding function, are widely used in heavy-duty diesel engines.

[0003] Existing double-walled high-pressure oil pipe end sealing structures generally have the following shortcomings:

[0004] First, the sealing and axial positioning functions are integrated into the same component, making assembly stress control difficult. Long-term vibration can easily lead to stress relaxation, resulting in seal failure.

[0005] Secondly, the single sealing layer makes it difficult to simultaneously meet the requirements of high-pressure dynamic sealing of the inner layer and low-pressure static sealing of the outer layer, resulting in poor sealing reliability.

[0006] Third, the sealing cone surface that mates with the fuel injector is prone to wear after repeated disassembly and assembly, resulting in poor contact surface fit and causing leakage;

[0007] Fourth, the lack of dedicated leak monitoring channels and interfaces makes it impossible to achieve real-time monitoring and early warning of fuel leaks, posing a safety hazard.

[0008] The aforementioned problems result in short seal life and low reliability of existing double-walled high-pressure oil pipes, making it difficult to meet the requirements of ultra-high pressure, long-cycle, and strong vibration conditions. Therefore, developing a structurally sound, reliable, wear-resistant, and monitorable double-walled high-pressure oil pipe end seal structure has significant engineering application value. Summary of the Invention

[0009] The technical problem this application aims to solve is that existing double-walled high-pressure oil pipes have significant shortcomings in terms of durability, sealing, and safety, which restricts the development of high-pressure common rail diesel engines towards higher pressure, higher reliability, and longer service life.

[0010] To solve the above-mentioned technical problems, according to one aspect of this application, a double-walled high-pressure fuel pipe sealing mechanism for a diesel engine is provided, comprising: an injector sealing cone, a ball-head sealing cone, an inner wall positioning ring, a sealing rubber ring I, an outer wall positioning joint, a sealing copper gasket, a sealing rubber ring II, a thrust ring, a locking joint, and a double-walled pipe. The double-walled pipe includes an inner pipe and an outer pipe coaxially nested, forming an annular sandwich between the inner and outer pipes. The double-walled pipe is placed horizontally, and a ball-head sealing cone is provided at its left end. The ball-head sealing cone is embedded in the injector sealing cone, which is fixed to the injector body. The inner wall positioning ring is sleeved on the outer circumference of the right axial section of the ball-head sealing cone and fixedly connected to the end of the inner pipe. One end of the outer wall positioning joint is sleeved on the inner wall. The outer side of the positioning ring and the other end are fitted onto the outer wall of the outer tube. The inner side of the outer wall positioning joint has a stepped cap structure. The sealing rubber ring I is embedded in the annular gap between the inner wall positioning ring and the outer wall positioning joint. The left side of the sealing copper gasket is adjacent to the outer wall positioning joint and fitted onto the outer circumference of the right side of the outer wall shaft of the outer tube. The thrust ring is fitted onto the outer wall of the outer tube and fits against the right side of the sealing copper gasket. The sealing rubber ring II is located between the sealing copper gasket and the thrust ring. The sealing copper gasket is clamped axially by the thrust ring and the sealing rubber ring II. The locking joint is located on the right side of the outer periphery of the double-walled tube. The left end of the locking joint is fitted onto the outer end of the outer wall positioning joint, and the right end is connected to the thrust ring. The sealing copper gasket and the sealing rubber ring II are axially pressed between the thrust ring and the locking joint.

[0011] According to an embodiment of this application, the ball head radius R of the ball head sealing cone and the cone angle α of the injector sealing cone satisfy the following relationship: R=(0.8~1.2)×(D / 2sin(α / 2)), where D is the outer diameter of the inner tube, to ensure the formation of an ideal line contact sealing strip.

[0012] According to an embodiment of this application, the ball head sealing cone has a left-facing cone surface that corresponds to and fits against the cone surface of the injector sealing cone, forming a metal-to-metal sealing pair of cone surface and ball head.

[0013] According to an embodiment of this application, the right end of the outer wall positioning connector is connected to the locking connector via an M22×1.5 fine thread, and the outer surface of the left end is provided with an M24×2 external thread to connect to the injector mounting seat.

[0014] According to the embodiments of this application, sealing rubber ring I and sealing rubber ring II are fluororubber sealing rings with different cross-sectional shapes, sealing rubber ring I is an O-ring and sealing rubber ring II is an X-ring.

[0015] According to an embodiment of this application, the inner wall positioning ring is a wave-shaped elastic metal ring installed between the inner tube and the outer tube, with its crests contacting the inner wall of the outer tube and its troughs contacting the outer wall of the inner tube.

[0016] According to an embodiment of this application, the inner tube of the double-walled tube is a precision cold-drawn seamless steel tube with an outer diameter of 6mm and a wall thickness of 1.5mm; the outer tube of the double-walled tube is a 10# steel tube with an outer diameter of 12mm and a wall thickness of 1mm; a 0.5mm annular sandwich is formed between the inner tube and the outer tube.

[0017] According to an embodiment of this application, the thrust ring is a stepped fixing seat structure.

[0018] According to an embodiment of this application, the outer wall positioning joint is pre-drilled with a radial through hole, which connects to the leakage detection pipeline.

[0019] According to another aspect of this application, a sealing method for a diesel engine double-walled high-pressure oil pipe sealing mechanism as described above is provided, comprising the following steps:

[0020] S1: Pre-positioning of inner and outer tubes:

[0021] Install the inner wall positioning ring between the inner tube and the outer tube to make the inner wall positioning ring and the inner wall tube coaxially positioned.

[0022] S2: External wall radial multi-layer seal and auxiliary seal:

[0023] The outer wall positioning joint is fitted onto the left side of the outer tube of the double-walled pipe. A sealing rubber ring I is installed in the stepped pressure cap structure inside the outer wall positioning joint. On the right side shaft section of the outer tube, a sealing copper gasket and a sealing rubber ring II are fitted in sequence, so that the sealing copper gasket is tightly attached to the shoulder end face of the outer tube shaft, and the sealing rubber ring II is located to the right of the sealing copper gasket. The sealing rubber ring I and the sealing rubber ring II form a double radial elastic seal on the outer tube wall.

[0024] S3: Axial rigid limit:

[0025] The thrust ring is fitted onto the outer circumference of the double-walled pipe, so that its left end face is pressed against the sealing rubber ring II. The locking joint is connected to the thrust ring, and the other end of the locking joint is connected to the outer wall positioning joint through the M22 thread, so that the end face of the thrust ring abuts against the end of the double-walled pipe, thereby achieving axial rigid positioning of the piping system.

[0026] S4: Establishment of the main sealing surface:

[0027] The ball head sealing cone is fixedly connected to the left shaft section of the inner wall positioning ring. The injector sealing cone is placed on the injector body. The locking joint is tightened. The axial locking force is transmitted through the thrust ring, which forces the ball head sealing cone and the injector sealing cone to fit tightly together, forming the first metal high-pressure seal between the cone surface and the ball head, thus completing the end face seal of the high-pressure fuel passage.

[0028] S5: Leakage monitoring channel connection:

[0029] The annular interlayer between the inner and outer pipes is connected to the external leak monitoring pipeline through a radial through hole opened on the positioning joint on the outer wall, so as to realize the directional drainage of leaking fuel and alarm triggering.

[0030] Compared with the prior art, the technical solution of this application has the following beneficial effects:

[0031] 1. Three-level sealing and synergistic protection: The conical-ball-head metal seal on the inner wall side blocks the high-pressure fuel passage, the sealing rubber ring I achieves radial sealing between the inner and outer wall pipes, and the copper gasket and rubber ring composite seal on the outer wall side achieves secondary sealing at the end of the outer wall pipe. The synergistic effect of the three-layer seals ensures the sealing reliability of the double-walled high-pressure oil pipe under high-pressure conditions, solving the problem that a single sealing method is prone to failure under high-pressure pulse conditions.

[0032] 2. Decoupling of positioning and sealing functions: The thrust ring is dedicated to axial positioning, separating the positioning force from the sealing force. This avoids the stress concentration and seal damage caused by the simultaneous action of locking force on the sealing surface in traditional designs, significantly improving assembly consistency and long-term reliability.

[0033] 3. The dual function of the inner wall positioning ring: The inner wall positioning ring not only ensures the coaxiality of the inner and outer tubes, but also absorbs vibration and thermal expansion, preventing the inner and outer tubes from interfering with each other due to uneven thermal stress.

[0034] 4. Integrated Leakage Monitoring Function: Utilizing the annular gap between the inner and outer pipes as a natural leakage channel, the leakage is led out through the positioning joint on the outer wall, eliminating the need for additional drilling on the pipe body. The structure is compact and can be used in conjunction with an electronic control alarm device to achieve real-time monitoring of the leakage point.

[0035] 5. Double-thread anti-loosening design: The combination of M22 internal thread and M24 external thread, together with the rigid limit of the thrust ring, effectively resists the wide frequency vibration of the diesel engine, avoids loosening of the connection pair, and improves the safety redundancy of the system. Attached Figure Description

[0036] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings of the embodiments will be briefly described below. Obviously, the drawings described below only relate to some embodiments of this application, and are not intended to limit this application.

[0037] Figure 1 A schematic diagram of a double-walled high-pressure oil pipe sealing mechanism for a diesel engine, as an example of the invention;

[0038] Figure 2 This is a flowchart illustrating the steps of a sealing method for a diesel engine double-walled high-pressure oil pipe sealing mechanism, as exemplified by the present invention.

[0039] The attached diagram is described below:

[0040] 1. Injector sealing cone; 2. Ball head sealing cone; 3. Inner wall positioning ring; 4. Sealing rubber ring I; 5. Outer wall positioning joint; 6. Sealing copper gasket; 7. Sealing rubber ring II; 8. Thrust ring; 9. Locking joint; 10. Outer tube; 11. M22 thread; 12. M24 thread; 13. Inner tube. Detailed Implementation

[0041] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. Based on the described embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0042] Unless otherwise defined, the technical or scientific terms used herein shall have the ordinary meaning as understood by one of ordinary skill in the art to which this application pertains. The terms “first,” “second,” and similar terms used in the specification and claims of this patent application do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Similarly, the terms “an” or “a,” and similar terms, do not indicate a limitation of quantity, but rather indicate the presence of at least one.

[0043] like Figure 1 As shown in the example, this application provides a diesel engine double-wall high-pressure fuel pipe sealing mechanism, including an injector sealing cone 1, a ball-head sealing cone 2, an inner wall positioning ring 3, a sealing rubber ring I4, an outer wall positioning joint 5, a sealing copper gasket 6, a sealing rubber ring II7, a thrust ring 8, a locking joint 9, and a double-wall pipe. This application forms a gradient sealing barrier from the high-pressure area to the low-pressure area through a three-stage sealing structure of "injector sealing cone 1 + ball-head sealing cone 2" (metal hard seal), "sealing copper gasket 6" (plastic deformation seal), and "double rubber sealing rings" (elastic seal). This solves the problem of easy failure of a single sealing form under high-pressure pulse conditions. Through multi-stage sealing and functional decoupling design, the safety of the diesel engine high-pressure fuel system is improved.

[0044] In this embodiment, the double-walled tube includes an inner tube 13 and an outer tube 10 nested coaxially, forming an annular sandwich between the inner tube 13 and the outer tube 10. The double-walled tube is placed horizontally, and its left end is provided with a ball-head sealing cone 2, which is embedded in the injector sealing cone 1, and the injector sealing cone 1 is fixed to the injector body. The inner wall positioning ring 3 is sleeved on the outer periphery of the right axial section of the ball-head sealing cone 2 and is fixedly connected to the end of the inner tube 13. One end of the outer wall positioning joint 5 is sleeved on the outside of the inner wall positioning ring 3, and the other end is sleeved on the outer wall of the outer tube 10. The inner wall positioning joint 5 has a stepped cap structure, and the sealing rubber ring I4 is embedded in the inner wall positioning ring 3. In the annular gap between the outer wall positioning joint 5 and the outer wall positioning joint 5; the left side of the sealing copper gasket 6 is adjacent to the outer wall positioning joint 5 and is sleeved on the outer periphery of the right side shaft section of the outer wall of the outer tube 10; the thrust ring 8 is sleeved on the outer wall of the outer tube 10 and fits against the right side of the sealing copper gasket 6; the sealing rubber ring II7 is located between the sealing copper gasket 6 and the thrust ring 8; the sealing copper gasket 6 is clamped axially by the thrust ring 8 and the sealing rubber ring II7; the locking joint 9 is located on the right side of the outer periphery of the double-walled tube; the left end of the locking joint 9 is sleeved on the outer end of the outer wall positioning joint 5, and the right end is connected to the thrust ring 8; the sealing copper gasket 6 and the sealing rubber ring II7 are axially pressed between the thrust ring 8 and the locking joint 9.

[0045] Specifically, the ball head radius R of the ball head sealing cone 2 and the cone angle α of the injector sealing cone 1 satisfy the following relationship: R=(0.8~1.2)×(D / 2sin(α / 2)), where D is the outer diameter of the inner tube 13, to ensure the formation of an ideal line contact sealing strip.

[0046] Specifically, the sealing copper gasket 6 is an annular metal gasket that is fitted around the outer circumference of the right axial section of the outer wall of the double-walled pipe. It is clamped axially by the thrust ring 8 and the sealing rubber ring II7 to provide a hard metal seal at the connection of the outer wall pipe.

[0047] Specifically, the locking joint 9 is a flange component located at the rightmost end of the overall structure. It is connected to the thrust ring 8 and locked by fasteners, which axially presses the sealing copper gasket 6 and the sealing rubber ring II7 between the thrust ring 8 and the locking joint 9, forming a secondary sealing and locking structure at the end of the outer wall pipe.

[0048] Specifically, the ball head cone 2 has its cone surface facing left, which corresponds to and fits against the cone surface of the injector sealing cone 1, forming a metal-to-metal sealing pair of cone surface and ball head.

[0049] Specifically, the right end of the outer wall positioning connector 5 is connected to the locking connector 9 via an M22×1.5 fine-pitch internal thread, while the left end has an M24×2 external thread that connects to the injector mounting seat. The combination of the M22 internal thread and the M24 external thread, along with the rigid limiting of the thrust ring 8, effectively resists the wide-frequency vibration of the diesel engine, prevents the connection from loosening, and improves the safety redundancy of the system.

[0050] Specifically, sealing rubber ring I4 and sealing rubber ring II7 are fluororubber sealing rings with different cross-sectional shapes. Sealing rubber ring I4 is an O-ring, and sealing rubber ring II7 is an X-ring. Sealing rubber ring I4 is embedded in the annular interlayer between the inner wall positioning ring 3 and the outer wall positioning joint 5. It is compressed by the inner and outer side components to achieve radial sealing between the inner and outer wall pipes, preventing high-pressure fuel from leaking from the interlayer cavity between the inner and outer wall pipes. Sealing rubber ring II7 is located between the sealing copper gasket 6 and the locking joint 9. After being axially compressed, it achieves elastic sealing between the outer wall pipe and the locking joint 9.

[0051] Specifically, the inner wall positioning ring 3 is a corrugated elastic metal ring installed between the inner tube 13 and the outer tube 10. Its crests contact the inner wall of the outer tube 10, and its troughs contact the outer wall of the inner tube 13. The inner wall positioning ring 3 not only ensures the coaxiality of the inner and outer tubes 10, but also absorbs vibration and thermal expansion, preventing the inner and outer tubes 10 from interfering with each other due to uneven thermal stress.

[0052] Specifically, the inner tube 13 of the double-walled tube is a precision cold-drawn seamless steel tube with an outer diameter of 6mm and a wall thickness of 1.5mm; the outer tube 10 of the double-walled tube is a steel tube made of 10# steel with an outer diameter of 12mm and a wall thickness of 1mm; a 0.5mm annular sandwich is formed between the inner tube 13 and the outer tube 10.

[0053] Specifically, the thrust ring 8 is a stepped fixed seat structure. The thrust ring 8 is specifically designed to perform axial positioning, separating the positioning force from the sealing force. This avoids the stress concentration and seal damage caused by the simultaneous action of locking force on the sealing surface in traditional designs, and significantly improves assembly consistency and long-term reliability.

[0054] Specifically, the outer wall positioning connector 5 has a pre-set radial through hole that connects to the leakage detection pipeline. This application utilizes the annular interlayer between the inner and outer pipes 10 as a natural leakage channel, which is led out through the pre-set radial through hole of the outer wall positioning connector 5. No additional drilling is required on the pipe body, resulting in a compact structure that can be used in conjunction with an electronic alarm device to achieve real-time monitoring of the leakage point.

[0055] Another aspect of this application discloses a sealing method for a diesel engine double-walled high-pressure oil pipe sealing mechanism as described above, comprising the following steps:

[0056] S1: Inner and outer tubes 10 pre-positioning:

[0057] The inner wall positioning ring 3 is installed between the inner tube 13 and the outer tube 10, so that the inner wall positioning ring 3 is coaxially positioned with the inner wall tube.

[0058] S2: External wall radial multi-layer seal and auxiliary seal:

[0059] The outer wall positioning joint 5 is fitted onto the left side of the outer tube 10 of the double-walled pipe. A sealing rubber ring I4 is installed in the stepped pressure structure inside the outer wall positioning joint 5. On the right side shaft section of the outer tube 10, a sealing copper gasket 6 and a sealing rubber ring II7 are sequentially fitted, so that the sealing copper gasket 6 is tightly attached to the shoulder end face of the outer tube 10, and the sealing rubber ring II7 is located to the right of the sealing copper gasket 6. The sealing rubber ring I4 and the sealing rubber ring II7 form a double radial elastic seal on the outer tube 10 wall.

[0060] Specifically, the locking joint 9 is connected to the thrust ring 8 and locked with fasteners. The locking force is transmitted through the locking joint 9 to the sealing rubber ring II7 and the sealing copper gasket 6, which are compressed axially between the thrust ring 8 and the locking joint 9. The sealing copper gasket 6 undergoes plastic deformation to fit the sealing surface and fills the micro gap between the thrust ring 8 and the inner tube 13 to form an auxiliary seal. The sealing rubber ring II7 undergoes elastic deformation to achieve an elastic seal, forming a secondary composite sealing structure at the end of the outer wall tube.

[0061] S3: Axial rigid limit:

[0062] The thrust ring 8 is fitted around the outer circumference of the outer tube 10 of the double-walled pipe, so that its left end face is pressed against the sealing rubber ring II7. The locking joint 9 is connected to the thrust ring 8, and the other end of the locking joint 9 is connected to the outer wall positioning joint 5 through the M22 thread 11, so that the end face of the thrust ring 8 abuts against the end of the double-walled pipe, thereby achieving axial rigid positioning of the piping system.

[0063] S4: Establishment of the main sealing surface:

[0064] The ball head sealing cone 2 is fixedly connected to the left shaft section of the inner wall positioning ring 3. The injector sealing cone 1 is placed on the injector body. The locking joint 9 is tightened. The axial locking force is transmitted through the thrust ring 8, which forces the ball head sealing cone 2 and the cone surface of the injector sealing cone 1 to fit tightly together, forming a high-pressure metal seal between the cone surface and the ball head, thus completing the end face sealing of the high-pressure fuel passage.

[0065] Specifically, the assembled double-walled tube is pushed to the left as a whole, so that the ball head cone surface of the ball head sealing cone 2 corresponds and fits with the cone surface of the injector sealing cone 1 fixed on the injector body. An axial locking force is applied to the thrust ring 8 through the locking joint 9, so that the ball head cone surface fits tightly with the injector sealing cone 1 surface, forming the first metal seal between the cone surface and the ball head.

[0066] S5: Leakage monitoring channel connection:

[0067] The annular interlayer between the inner pipe 13 and the outer pipe 10 is connected to the external leakage monitoring pipeline through a radial through hole opened on the positioning joint 5 on the outer wall, so as to realize the directional drainage of leaking fuel and alarm triggering.

[0068] Example 1: Assembly of a double-walled high-pressure oil pipe sealing mechanism for a diesel engine

[0069] During assembly, first press the inner wall positioning ring 3 between the inner and outer tubes 10, then put the outer wall positioning connector 5 on the outer tube 10, and then install the sealing rubber ring I4 on the outer wall of the inner tube 13 and the sealing rubber ring II7 on the outer wall of the outer tube 10 in sequence. Next, install the sealing copper gasket 6 and the thrust ring 8 into the locking connector 9 in sequence, and then pre-tighten the locking connector 9 and the outer wall positioning connector 5 until the resistance appears by hand.

[0070] Screw the entire assembly into the injector mounting bracket via M24 thread 12 until the ball head seal cone 2 makes slight contact with the injector seal cone 1. Then tighten the locking connector 9 using a torque wrench to a torque of 80-100 N·m.

[0071] During tightening, the thrust ring 8 pushes the inner tube 13 to the right, causing a 0.1mm interference between the ball head sealing cone 2 and the injector sealing cone 1, forming a metal line seal with extremely high contact stress. Simultaneously, the sealing copper gasket 6 is compressed and deformed under axial force, filling the microscopic unevenness gap between the thrust ring 8 and the inner tube 13, forming an auxiliary seal. The two external rubber rings ensure a static seal between the outer tube 10 and the outer wall positioning joint 5, preventing external moisture and impurities from entering.

[0072] If the inner pipe 13 ruptures, high-pressure fuel will leak into the annular cavity of the inner and outer pipes 10. The fuel can flow to the leak detection pipeline through the pre-set radial through hole on the outer wall positioning joint 5, triggering the alarm indicator light in the cab and reminding the operator to repair it in time.

[0073] Example 2: Explanation of the technical effects of a double-walled high-pressure oil pipe sealing mechanism for diesel engines

[0074] To verify the technical effect of the present invention, Comparative Example 1 was set up. Comparative Example 1 adopts a traditional single conical sealing structure, which relies on only a 60° conical surface for sealing, without copper gasket to assist the sealing, and only one rubber sealing ring is set between the outer tube 10 and the joint.

[0075] Under the same conditions, a 200-hour durability vibration test was conducted at a frequency of 50 Hz and an acceleration of 5g, along with a pressure pulse test (pressure 0-200 MPa, frequency 1 Hz, 100,000 cycles). The test results are as follows:

[0076] The sealing mechanism of Example 1: No leakage was observed after the test, the connecting threads were not loose, and there was no visible wear on the sealing surface;

[0077] The sealing structure of Comparative Example 1: a slight leak occurred after 80,000 pulses. Upon disassembly and inspection, wear marks were found on the conical surface and the rubber ring was aged and deformed.

[0078] The test results show that the multi-stage sealing structure and positioning design of Example 1 significantly improve the reliability and durability of the sealing system.

[0079] In summary, the technical solution of this application has the following beneficial effects:

[0080] 1. Three-level sealing and synergistic protection: The conical-ball-head metal seal on the inner wall side blocks the high-pressure fuel passage, the sealing rubber ring I achieves radial sealing between the inner and outer wall pipes, and the copper gasket and rubber ring composite seal on the outer wall side achieves secondary sealing at the end of the outer wall pipe. The synergistic effect of the three-layer seals ensures the sealing reliability of the double-walled high-pressure oil pipe under high-pressure conditions, solving the problem that a single sealing method is prone to failure under high-pressure pulse conditions.

[0081] 2. Decoupling of positioning and sealing functions: The thrust ring is dedicated to axial positioning, separating the positioning force from the sealing force. This avoids the stress concentration and seal damage caused by the simultaneous action of locking force on the sealing surface in traditional designs, significantly improving assembly consistency and long-term reliability.

[0082] 3. The dual function of the inner wall positioning ring: The inner wall positioning ring not only ensures the coaxiality of the inner and outer tubes, but also absorbs vibration and thermal expansion, preventing the inner and outer tubes from interfering with each other due to uneven thermal stress.

[0083] 4. Integrated Leakage Monitoring Function: Utilizing the annular gap between the inner and outer pipes as a natural leakage channel, the leakage is led out through the positioning joint on the outer wall, eliminating the need for additional drilling on the pipe body. The structure is compact and can be used in conjunction with an electronic control alarm device to achieve real-time monitoring of the leakage point.

[0084] 5. Double-thread anti-loosening design: The combination of M22 internal thread and M24 external thread, together with the rigid limit of the thrust ring, effectively resists the wide frequency vibration of the diesel engine, avoids loosening of the connection pair, and improves the safety redundancy of the system.

[0085] The above are merely exemplary embodiments of this application and are not intended to limit the scope of protection of this application, which is determined by the appended claims.

Claims

1. A sealing mechanism for a double-walled high-pressure oil pipe of a diesel engine, characterized in that, include: Injector sealing cone, ball head sealing cone, inner wall positioning ring, sealing rubber ring I, outer wall positioning joint, sealing copper gasket, sealing rubber ring II, thrust ring, locking joint, double-walled pipe. The double-walled tube includes a coaxially nested inner tube and an outer tube, forming an annular sandwich between the inner and outer tubes. The double-walled tube is placed horizontally, with a ball-head sealing cone at its left end. The ball-head sealing cone is embedded in the injector sealing cone, which is fixed to the injector body. An inner wall positioning ring is fitted around the outer circumference of the right-side axial section of the ball-head sealing cone and fixedly connected to the end of the inner tube. One end of the outer wall positioning joint is fitted around the outside of the inner wall positioning ring, and the other end is fitted around the outer wall of the outer tube. The outer wall positioning joint has a stepped cap structure inside. A sealing rubber ring I is embedded between the inner wall positioning ring and the outer wall positioning ring. The sealing copper gasket is located in the annular gap between the positioning joints; the left side of the sealing copper gasket is adjacent to the outer wall positioning joint and is sleeved on the outer periphery of the right axial section of the outer wall of the outer tube; the thrust ring is sleeved on the outer wall of the outer tube and fits against the right side of the sealing copper gasket; the sealing rubber ring II is located between the sealing copper gasket and the thrust ring; the sealing copper gasket is clamped axially by the thrust ring and the sealing rubber ring II; the locking joint is located on the right side of the outer periphery of the double-walled tube; the left end of the locking joint is sleeved on the outer end of the outer wall positioning joint, and the right end is connected to the thrust ring; the sealing copper gasket and the sealing rubber ring II are axially pressed between the thrust ring and the locking joint.

2. The diesel engine double-wall high-pressure oil pipe sealing mechanism according to claim 1, characterized in that, The ball head radius R of the ball head sealing cone and the cone angle α of the injector sealing cone satisfy the following relationship: R=(0.8-1.2)×(D / 2sin(α / 2)), where D is the outer diameter of the inner tube, to ensure the formation of an ideal line contact sealing band.

3. The diesel engine double-wall high-pressure oil pipe sealing mechanism according to claim 1, characterized in that, The ball head sealing cone has its cone surface facing left, which corresponds to and fits against the cone surface of the injector sealing cone, forming a metal-to-metal sealing pair of cone surface and ball head.

4. The diesel engine double-wall high-pressure oil pipe sealing mechanism according to claim 1, characterized in that, The right end of the outer wall positioning connector is connected to the locking connector via an M22×1.5 fine-pitch internal thread, and the left end has an M24×2 external thread that connects to the injector mounting seat.

5. The diesel engine double-wall high-pressure oil pipe sealing mechanism according to claim 1, characterized in that, The sealing rubber ring I and sealing rubber ring II are fluororubber sealing rings with different cross-sectional shapes. The sealing rubber ring I is an O-ring, and the sealing rubber ring II is an X-ring.

6. The diesel engine double-wall high-pressure oil pipe sealing mechanism according to claim 1, characterized in that, The inner wall positioning ring is a wave-shaped elastic metal ring installed between the inner tube and the outer tube, with its crest contacting the inner wall of the outer tube and its trough contacting the outer wall of the inner tube.

7. The diesel engine double-wall high-pressure oil pipe sealing mechanism according to claim 1, characterized in that, The inner tube of the double-walled tube is a precision cold-drawn seamless steel tube with an outer diameter of 6mm and a wall thickness of 1.5mm; the outer tube of the double-walled tube is a 10# steel tube with an outer diameter of 12mm and a wall thickness of 1mm; a 0.5mm annular sandwich is formed between the inner tube and the outer tube.

8. A diesel engine double-walled high-pressure oil pipe sealing mechanism according to claim 1, characterized in that, The thrust ring is a stepped fixed seat structure.

9. A diesel engine double-walled high-pressure oil pipe sealing mechanism according to claim 1, characterized in that, The outer wall positioning joint is pre-drilled with a radial through hole, which connects to the leakage detection pipeline.

10. A sealing method for a diesel engine double-walled high-pressure oil pipe sealing mechanism as described in any one of claims 1-9, characterized in that, Includes the following steps: S1: Pre-positioning of inner and outer tubes: The inner wall positioning ring is installed between the inner tube and the outer tube, so that the inner wall positioning ring is coaxially positioned with the inner wall tube. S2: External wall radial multi-layer seal and auxiliary seal: The outer wall positioning joint is sleeved on the left side of the outer tube of the double-walled pipe. The sealing rubber ring I is installed in the stepped pressure cap structure inside the outer wall positioning joint. The sealing copper gasket and sealing rubber ring II are sequentially sleeved on the right side shaft section of the outer tube, so that the sealing copper gasket is tightly attached to the shoulder end face of the outer tube shaft. The sealing rubber ring II is located to the right of the sealing copper gasket. The sealing rubber ring I and sealing rubber ring II form a double radial elastic seal for the outer tube wall. S3: Axial rigid limit: The thrust ring is fitted onto the outer circumference of the double-walled pipe, so that its left end face is pressed against the sealing rubber ring II. The locking connector is connected to the thrust ring, and the other end of the locking connector is connected to the outer wall positioning connector through an M22 thread, so that the end face of the thrust ring abuts against the end of the double-walled pipe, thereby achieving axial rigid positioning of the piping system. S4: Establishment of the main sealing surface: The ball head sealing cone is fixedly connected to the left shaft section of the inner wall positioning ring, the injector sealing cone is placed on the injector body, the locking joint is tightened, and the axial locking force is transmitted through the thrust ring, forcing the ball head sealing cone and the injector sealing cone to fit tightly together, forming the first metal high-pressure seal between the cone surface and the ball head, thus completing the end face sealing of the high-pressure fuel passage. S5: Leakage monitoring channel connection: The annular interlayer between the inner and outer pipes is connected to the external leakage monitoring pipeline through a radial through hole opened on the positioning joint on the outer wall, so as to realize the directional drainage of leaking fuel and alarm triggering.

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