Pressure limiting valve, high-pressure common rail system and machining method of pressure limiting valve

Abstract

The invention provides a pressure limiting valve, a high-pressure common rail system and a machining method of the pressure limiting valve. The pressure limiting valve comprises a first valve body provided with a first space, a second valve body provided with a second space, a valve rod; a sphere; the first space is provided with an inlet communicated with the outside; the ball body is accommodated in the first space; the movement of the valve rod is guided by the wall surface of the first space, and the valve rod is provided with a first curved surface matched with the ball body; the first curved surface is used for making contact with the ball, so that the ball is supported by the valve rod towards the inlet.

Description

Technical Field

[0001] The present application relates to a pressure limiting valve, a high-pressure common rail system, and a processing method of the pressure limiting valve. Background Art

[0002] The pressure limiting valve, a safety device used in high-pressure common rail systems, is typically installed on the common fuel supply line (the common rail). When the common rail pressure exceeds the threshold that triggers the valve to open, the valve opens and releases a certain flow of fuel, maintaining the common rail pressure within a certain range. This prevents component damage caused by excessive pressure while maintaining a certain pressure to ensure fuel injection.

[0003] The pressure-limiting valve of the high-pressure common rail system is in a working condition that requires repeated opening and closing. Its sealing structure includes two types: cone-cone sealing structure and ball-cone sealing structure. The cone-cone sealing structure achieves sealing by the contact and fit of two conical surfaces. Its disadvantages are that the grinding and processing cost of the two conical surfaces is high, and the conical surfaces are prone to scratches and wear when they contact. It requires high precision of motion guide, which leads to high processing difficulty and high cost. The ball-cone sealing structure achieves sealing by the contact and fit of the sphere and the conical surface. Because the sphere has the ability to automatically center during movement, the guidance requirements are reduced. The processing difficulty and cost of the sphere are relatively low, resulting in low processing difficulty and low cost. In addition, the use of spherical contact also helps to reduce friction and wear.

[0004] However, the inventors have discovered that existing pressure-limiting valves employing a ball-cone sealing structure are prone to deformation and failure at the contact point between the ball and the valve stem, which affects the reliability of the sealing structure and results in a short service life of the pressure-limiting valve. In view of this, the inventors have proposed a pressure-limiting valve, a high-pressure common rail system, and a processing method for the pressure-limiting valve to address at least one of the above technical problems. Summary of the Invention

[0005] The purpose of this application is to provide a pressure limiting valve.

[0006] Another object of the present application is to provide a high-pressure common rail system.

[0007] Another object of the present application is to provide a method for processing a pressure-limiting valve.

[0008] According to the first aspect of the present application, a pressure-limiting valve includes: a first valve body, including a first space; a valve stem; and a sphere; wherein the first space has an inlet connected to the outside world; the sphere is accommodated inside the first space; the movement of the valve stem is guided by the wall of the first space, and the valve stem is provided with a first curved surface adapted to the sphere; the first curved surface is used to contact the sphere, so that the sphere is supported by the valve stem toward the inlet.

[0009] After research and analysis, the inventors found that the above technical solution can significantly improve the problem of deformation failure that is prone to occur at the contact point between the ball and the valve stem of the pressure limiting valve, thereby extending the service life of the pressure limiting valve; its principle is that under the operating conditions of the high-pressure common rail system, the ball and the valve stem are subjected to dynamic pressure and impact loads caused by the oil pressure inside the common rail pipe. The comparative solution adopts point contact of the ball to the end plane of the valve stem, and its contact area is small, so that excessive compressive stress is generated in the local contact between the ball and the valve stem, and thus fatigue deformation and other failure problems are prone to occur; the pressure limiting valve provided in the present application is provided with the first curved surface adapted to the ball on the valve stem, and the first curved surface contacts the ball to increase the bearing area and disperse the load, thereby reducing local instantaneous stress concentration, improving fatigue deformation and other failure problems that occur at the contact point between the ball and the valve stem, improving the reliability of the pressure limiting valve and extending its service life.

[0010] In one or more embodiments of the pressure limiting valve, the valve stem includes: a rod body, the movement direction of which is guided by the wall of the first space; a spherical support, one end of which is connected to the rod body and the other end of which is provided with the first curved surface; the rod body and the spherical support are formed separately.

[0011] The design in which the rod body and the ball support are formed separately can significantly reduce the difficulty of producing and processing the valve stem on the basis of being able to support the ball, which is conducive to improving the accuracy of parts and fitting and enhancing structural reliability.

[0012] In one or more embodiments of the pressure limiting valve, the sphere has a nitrided layer or is made of silicon nitride material; and / or the first curved surface of the valve stem has a nitrided layer.

[0013] In one or more embodiments of the pressure-limiting valve, a first gap is formed between the ball seat and a wall surface of the first space.

[0014] In one or more embodiments of the pressure-limiting valve, the first valve body has a first hole to provide the first space, the bottom end surface of the first hole has the inlet, and the bottom of the first hole has an expansion section, the aperture of the expansion section is larger than the aperture of the hole section of the first hole connected to the expansion section; the first valve body also has a second hole extending from the inlet and connected to the outside.

[0015] In one or more embodiments of the pressure limiting valve, the pressure limiting valve further includes: a second valve body, connected to the first valve body and provided with a second space; an elastic member, accommodated in the second space and used to provide elastic force; a gasket, one side of which is connected to the second valve body and the other side of which is connected to the elastic member; and an elastic member support, connected to the elastic member and transmitting the force provided by the elastic member to the valve stem.

[0016] In one or more embodiments of the pressure limiting valve, the pressure limiting valve further includes: a slider, one end of which is connected to the elastic member support, and the other end of which is provided with a second curved surface; and the valve stem is provided with a third curved surface adapted to the second curved surface, and the third curved surface is used to contact the second curved surface.

[0017] In one or more embodiments of the pressure-limiting valve, the wall of the valve stem has a first surface and a second surface, the first surface is in close contact with the wall of the first space, and a second gap is formed between the second surface and the wall of the first space; the elastic member support has a fluid channel; the second space has an outlet connected to the outside world; in the first state, the ball is separated from the inlet; the external fluid flows into the pressure-limiting valve from the inlet, passes through the second gap, passes through the fluid channel, and flows out of the pressure-limiting valve from the outlet; in the second state, the ball contacts the inlet so that the inlet is closed.

[0018] According to a second aspect of the present application, a high-pressure common rail system includes the pressure-limiting valve according to any one of the above embodiments.

[0019] According to a third aspect of the present application, a processing method for a pressure-limiting valve is provided. The pressure-limiting valve is the pressure-limiting valve described in any one of the above embodiments. The processing method includes: treating the first curved surface of the valve stem using a nitriding process. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The above and other features, properties and advantages of the present application will become more apparent through the following description in conjunction with the accompanying drawings and embodiments. In the accompanying drawings, the same reference numerals always represent the same features. It should be noted that these drawings are only for illustration and are not drawn to scale. They should not be used to limit the actual scope of protection claimed in this application. Among them:

[0021] Figure 1 Schematic diagram of the structure of a high-pressure common rail system in one embodiment of the present application.

[0022] Figure 2 This is a structural diagram of a pressure limiting valve in an embodiment of the present application.

[0023] Figure 3 This is a schematic diagram of the partial structure of a pressure limiting valve in an embodiment of the present application.

[0024] Figure 4 Schematic diagram of the structure of a rod body in one embodiment of the present application.

[0025] Figure 5 Schematic diagram of the structure of a rod body in one embodiment of the present application.

[0026] Description of reference numerals:

[0027] 1. High-pressure common rail system;

[0028] 10. Pressure limiting valve;

[0029] 110. First valve body; 1110. First space; 1111. Inlet; 1112. Wall of first space; 1113. Expanding section; 1114. First hole; 1115. Second hole;

[0030] 120. Valve stem; 121. First curved surface; 122. Rod body; 123. Spherical support; 124. Third curved surface; 125. First surface; 126. Second surface;

[0031] 13. Sphere;

[0032] 14 first gap;

[0033] 150. Second valve body; 151. Second space; 152. Outlet;

[0034] 16. Elastic parts;

[0035] 17. Gasket;

[0036] 180. Elastic member support; 181. Fluid channel;

[0037] 190. Slider; 191. Second surface. DETAILED DESCRIPTION

[0038] Each embodiment of the present application will now be described in detail, examples of which are shown in the accompanying drawings and are described below. Although the present application will be described in conjunction with the exemplary embodiments, it should be appreciated that this specification is not intended to limit the present application to those exemplary embodiments. On the contrary, the present application is intended to cover not only these exemplary embodiments, but also various alternative forms, modifications, equivalent forms, and other embodiments that may be included within the spirit and scope of the present application as defined by the appended claims.

[0039] This application uses specific terms to describe the embodiments of this application. For example, "one embodiment" and / or "an embodiment" refers to a feature, structure, or characteristic associated with at least one embodiment of this application. Therefore, it should be emphasized and noted that "one embodiment" or "an embodiment" mentioned twice or multiple times in different places in this specification does not necessarily refer to the same embodiment. In addition, certain features, structures, or characteristics in one or more embodiments of this application may be appropriately combined.

[0040] In the subsequent description, the orientation or position relationship indicated by "upper", "lower", "front", "back", "inside", "outside" or other directional terms is based on the orientation or position relationship shown in the drawings, and is only for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the device or component referred to must have a specific orientation, be constructed and / or implemented in a specific orientation, and therefore cannot be understood as a limitation on the present application.

[0041] In this application, the terms "first", "second", etc. are only used to distinguish descriptions and should not be understood as indicating or implying positional relationships or importance rankings.

[0042] In the following description, unless otherwise specified or limited, the terms "mounted," "connected," "connected," "fixed," etc. should be understood in a broad sense; for example, they can refer to fixed connections or movable connections; they can refer to direct connections or indirect connections through an intermediary. Those skilled in the art will understand the specific meanings of the above terms in the embodiments of this application based on specific circumstances.

[0043] It can be understood that the pressure-limiting valve provided in the present application is particularly suitable for high-pressure common rail systems, but is not limited to this. It can also be applied to other applications that require limiting fluid pressure, such as pressure vessels or other fluid pipelines; the high-pressure common rail system provided in the present application is particularly suitable for marine diesel engines, but is not limited to this. It can also be applied to other applications that require controlling fuel injection, such as power generation equipment, other engines, etc.

[0044] As described above, the pressure-limiting valve is prone to deformation and failure at the contact point between the ball and the valve stem, which affects the reliability of the structure and shortens its service life. In view of this, the inventors of this application propose a pressure-limiting valve and a high-pressure common rail system to solve at least one of the above technical problems.

[0045] See also Figure 2 、 Figure 3The pressure-limiting valve 10 shown in FIG. 1 includes: a first valve body 110 including a first space 1110; a valve stem 120; and a sphere 13; wherein the first space 1110 has an inlet 1111 connected to the outside, and the sphere 13 is accommodated inside the first space 1110; the movement of the valve stem 120 is guided by the wall 1112 of the first space, for example, at least a portion of the valve stem 120 is a structure adapted to the wall 1112 of the first space, so that the valve stem 120 is tightly fitted with the wall 1112 of the first space, and thus the movement direction of the valve stem 120 is limited by the wall 1112 of the first space; the valve stem 120 is provided with a first curved surface 121 adapted to the sphere 13, for example, a concave surface formed by at least a portion of a spherical surface; the first curved surface 121 is capable of contacting the sphere 13 The ball 13 is supported by the valve stem 120 toward the inlet 1111; the inlet 1111 refers to an opening structure provided with a conical surface, etc., which can cooperate and contact with the ball 13 to achieve sealing; the ball 13 refers to a structure that can cooperate and contact with the inlet 1111 to achieve sealing and is adapted to the first curved surface 121; when the external fluid pressure is less than a pressure threshold, the ball 13 can contact and cooperate with the inlet 1111 under the support of the valve stem 120, so that the inlet 1111 is closed; when the external fluid pressure reaches the pressure threshold, the ball 13 overcomes the force supported by the valve stem 120 and separates from the inlet 1111, so that the external fluid can flow into the pressure-limiting valve 10 through the inlet 1111, and then the external fluid is depressurized, thereby limiting the external fluid pressure.

[0046] After research and analysis, the inventors found that the above technical solution can significantly improve the problem of deformation failure of the pressure limiting valve at the contact point between the ball and the valve stem, thereby improving the reliability of the pressure limiting valve and extending its service life; its principle is that under the operating conditions of the high-pressure common rail system, the ball and the valve stem are subjected to dynamic pressure and impact loads caused by the oil pressure inside the common rail pipe. The comparative solution adopts point contact of the ball to the end plane of the valve stem, and its contact area is small, so that excessive compressive stress is generated in the local contact between the ball and the valve stem, which is easy to cause failure problems such as fatigue deformation; the pressure limiting valve 10 provided in the present application is provided with the first curved surface 121 adapted to the ball 13 on the valve stem 120, and the first curved surface 121 and the ball 13 adopt spherical contact, so that the bearing area is increased and the load is dispersed, reducing instantaneous stress concentration, thereby improving the fatigue deformation and other failure problems occurring at the contact point between the ball 13 and the valve stem 120, improving structural reliability and extending service life.

[0047] In one or more embodiments of the pressure-limiting valve 10, the valve stem 120 includes: a rod body 122, the movement direction of which is guided by the wall 1112 of the first space; a spherical support 123, one end of which is connected to the rod body 122 and the other end of which is provided with the first curved surface 121; the rod body 122 and the spherical support 123 are formed separately.

[0048] The inventors have found that it is difficult to ensure the precision of the parts and the precision of the fit between the valve stem 120 and the sphere 13 when the valve stem 120 is formed in one piece. The reason is that when machining the one-piece valve stem 120, the outer circle of the slender rod-shaped workpiece needs to be used as a reference for machining the first curved surface 121. On the one hand, it is difficult to clamp and position the workpiece. On the other hand, the problem of workpiece runout leads to reduced machining precision, especially making it difficult to ensure the contour of the first curved surface 121, affecting the precision of the fit between the valve stem 120 and the sphere 13, and reducing the structural reliability. However, the rod body 122 and the sphere support 123 are formed separately, and the rod body 122 assumes the guiding function of the valve stem 120, and the sphere support 123 is in contact with the sphere 13. On the basis of being able to provide support for the sphere 13, the machining of the first curved surface 121 is not adversely affected by the slender rod-shaped workpiece, thereby reducing the machining difficulty, improving the parts, the precision of the fit and the batch stability of the parts, improving the structural reliability of the pressure limiting valve and extending its service life.

[0049] Optionally, the rod body 122 (or the valve stem 120) is slidably connected to the wall surface 1112 of the first space via a cylindrical surface. The cylindricity of the rod body 122 (or the valve stem 120) is in the range of 2 micrometers (μm) to 3 μm. The rod body 122 (or the valve stem 120) forms a clearance fit with the wall surface 1112 of the first space, and the clearance is in the range of 0.008 mm to 0.015 mm. This design ensures the stability of the rod movement and reduces wear.

[0050] Optionally, the contour of the first curved surface 121 is in the range of 0.01 mm to 0.015 mm, and the ball diameter tolerance is less than or equal to 0.04 mm; such a design is conducive to improving the fitting accuracy between parts and reducing wear on the sphere 13.

[0051] Optionally, the ball support 123 and the rod body 122 are in contact, for example, in planar contact; the fuel flows from the inlet 1111 into the interior of the pressure limiting valve 10, which can play a lubricating and cooling role between the ball support 123 and the rod body 122, and between the ball support 123 and the ball 13, which is beneficial to reduce parts wear, etc.

[0052] In one or more embodiments of the pressure limiting valve 10, the sphere 13 has a nitrided layer or is made of silicon nitride material; and / or the first curved surface 121 of the valve stem 120 has a nitrided layer; specifically, the sphere 13 and / or the valve stem 120 can be made of a metal material, and the sphere 13 and / or the first curved surface 121 are nitrided, or the sphere 13 can be a silicon nitride ceramic ball; such a design is conducive to improving the hardness and wear resistance of the sphere 13 and the first curved surface 121, and improving the structural reliability; further, the sphere support 123 can be made of a nickel-based alloy, and the sphere support 123 has a nitrided layer at least on the first curved surface 121; so The spherical support 123 has high hardness and high wear resistance on the first curved surface 121, and high toughness in the core, which is conducive to absorbing and buffering the impact energy of the sphere 13, and improving the failure problems such as wear and fragmentation of the spherical support 123 under multiple impacts of the sphere 13; further, the silicon nitride ceramic ball can also be a G5 precision grade ceramic ball of ISO standard; silicon nitride ceramic ball has low density, high hardness, high elastic modulus, high temperature resistance, wear resistance, high impact resistance, low thermal expansion coefficient, good insulation, non-magnetic properties, etc., which is particularly suitable for the working environment of the pressure limiting valve 10, and has been applied in technical fields such as ball bearings to form standardized products, which are easy to obtain and conducive to quality and cost control.

[0053] In one or more embodiments of the pressure-limiting valve 10, a first gap 14 is formed between the ball support 123 and the wall 1112 of the first space. Specifically, the radial dimension of the first gap 14 is less than or equal to 1 mm. This design eliminates the need for a precise fit between the ball support 123 and the wall 1112 of the first space, reducing manufacturing complexity. Furthermore, the size range of the first gap 14 is limited, reducing wear and ensuring structural reliability.

[0054] In one or more embodiments of the pressure limiting valve 10, the first valve body 110 has a first hole 1114 to provide the first space 1110, the bottom end surface of the first hole 1114 has the inlet 1111, and the bottom of the first hole 1114 has an expansion section 1113, the aperture of the expansion section 1113 is larger than the aperture of other hole sections of the first hole 1114 connected to the expansion section 1113; the first valve body 110 also has a second hole 1115 extending from the inlet 1111 and communicating with the outside ; Specifically, the first hole 1114 can be a cylindrical hole, and the valve stem 120 (and the rod body 122) can be a cylindrical rod; the design of the expansion section 1113 is conducive to providing operating space for grinding and other processing on the one hand, and on the other hand, it can enable the fluid to enter the inlet 1111 and then be radially ejected outward in the expansion section 1113 to reduce the impact on the ball 13 and improve the reliability of the structure; the second hole 1115 is used as a throttling hole, which is conducive to pressure control of the fluid flowing into the first valve body 110.

[0055] In one or more embodiments of the pressure-limiting valve 10, the pressure-limiting valve 10 further includes: a second valve body 150, connected to the first valve body 110 and provided with a second space 151; an elastic member 16, accommodated inside the second space 151, for providing elastic force to support the ball 13; a gasket 17, one side of which is connected to the second valve body 150 and the other side of which is connected to the elastic member 16; an elastic member support 180, connected to the elastic member 16, and transmitting the force provided by the elastic member 16 to the valve stem 120. Such a design provides a practical and reliable structure to provide force to support the sphere 13; the gasket 17 refers to a structure for adjusting the elastic deformation of the elastic member 16. For example, the elastic member 16 is a spring, and the compression of the spring is adjusted by adjusting the thickness of the gasket 17, so that the force supporting the sphere 13 and the pressure threshold that can separate the sphere 13 from the inlet 1111 can be adjusted; the elastic member support 180 can be provided with a boss, so that the elastic member 16 is mounted on the outer peripheral side of the boss to limit the position and direction of the elastic member 16.

[0056] In one or more embodiments of the pressure limiting valve 10, the pressure limiting valve 10 further includes: a slider 190, one end of which is connected to the elastic member support 180, and the other end of which is provided with a second curved surface 191; and the valve stem 120 is provided with a third curved surface 124 adapted to the second curved surface 191, and the third curved surface 124 is used to contact the second curved surface 191; specifically, the slider 190 and the elastic member support 180 can be in plane contact; if the elastic force provided by the elastic member 16 is not centered, the valve stem 120 will be deflected. The slider 190 is designed to automatically slide and center to reduce the adverse effects of force misalignment on the elastic member 16; and the slider 190 and the valve stem 120 are in contact with the second curved surface 191 and the third curved surface 124. The second curved surface 191 and the third curved surface 124 can be arc surfaces or spherical surfaces, so that the force on the valve stem 120 is directed to the center of the arc surface, which plays an automatic centering role, improves the stability of the force on the valve stem 120, and improves the reliability of the pressure limiting valve 10.

[0057] In one or more embodiments of the pressure limiting valve 10, the wall surface of the valve stem 120 has a first surface 125 and a second surface 126, and the first surface 125 is in close contact with the wall surface 1112 of the first space, so that the first space 1110 can guide the valve stem 120; a second gap is formed between the second surface 126 and the wall surface 1112 of the first space, that is, a structure similar to an oil groove is formed, so that fluid can pass through the second gap; the elastic member support 180 has a fluid channel 181, such as a hole; the second space 151 has a fluid channel connected to The outlet 152 of the pressure limiting valve 10 is connected to the outside. In the first state, the ball 13 is separated from the inlet 1111, and the external fluid flows from the inlet 1111 into the first space 1110 of the pressure limiting valve 10, enters the second space 151 through the second gap of the valve stem 120, and flows out of the pressure limiting valve 10 from the outlet 152 through the fluid channel 181 of the elastic member support 180. In the second state, the ball 13 contacts the inlet 1111 so that the inlet 1111 is closed, and the external fluid cannot enter the pressure limiting valve 10 through the inlet 1111. This design provides a streamlined, compact, and functionally reliable pressure limiting valve structure. Specifically, the valve stem 120 is a roughly cylindrical rod, and has three second surfaces 126 evenly distributed circumferentially on the cylindrical surface, so that the pressure of the fluid remains stable when passing through the second gap.

[0058] According to a second aspect of the present application, a high-pressure common rail system 1 includes the pressure-limiting valve 10 according to any one of the above embodiments; specifically, the pressure-limiting valve 10 can be installed in a common rail pipe of the high-pressure common rail system 1 .

[0059] According to a third aspect of the present application, a processing method for a pressure-limiting valve is provided. The pressure-limiting valve is the pressure-limiting valve 10 described in any one of the above embodiments. The processing method includes: treating the first curved surface 121 of the valve stem 120 using a nitriding process; or, the valve stem 120 includes the rod body 122 and the spherical support 123 described in any one of the above embodiments, and treating the first curved surface 121 of the spherical support 123 using a nitriding process. The nitriding process can form a nitrided layer on the surface of the first curved surface 121, thereby improving the hardness and wear resistance of the first curved surface 121.

[0060] Furthermore, the processing method may further include: nitriding the contact surface between the spherical support 123 and the rod body 122 to further improve structural reliability.

[0061] In summary, the beneficial effects of the pressure limiting valve, high-pressure common rail system, and pressure limiting valve processing method described in the above embodiments include but are not limited to at least one of the following:

[0062] The invention significantly improves the problem of deformation failure easily occurring at the contact part between the ball and the valve stem of the pressure limiting valve, thereby improving the reliability of the pressure limiting valve and extending its service life; its principle is that under the operating conditions of the high-pressure common rail system, the ball and the valve stem are subjected to dynamic pressure and impact loads caused by the oil pressure inside the common rail pipe. The comparative scheme adopts point contact of the ball to the end plane of the valve stem, and its contact area is small, so that excessive compressive stress is generated in the local contact between the ball and the valve stem, which is easy to cause failure problems such as fatigue deformation; the pressure limiting valve provided in the present application is provided with the first curved surface adapted to the ball on the valve stem, and the first curved surface and the ball adopt spherical contact, so that the bearing area is increased and the load is dispersed, thereby reducing instantaneous stress concentration, thereby improving the failure problems such as fatigue deformation occurring at the contact part between the ball and the valve stem, improving structural reliability and extending service life.

[0063] Although the present application is disclosed above with reference to preferred embodiments, this is not intended to limit the present application. Any person skilled in the art may make possible changes and modifications without departing from the spirit and scope of the present application. Therefore, any modifications, equivalent variations, and modifications made to the above embodiments based on the technical essence of the present application without departing from the content of the technical solution of the present application shall fall within the scope of protection defined by the claims of the present application.

Claims

1. A pressure limiting valve (10), characterized in that: include: A first valve body (110) includes a first space (1110); Valve stem (120); sphere (13); wherein, The first space (1110) has an inlet (1111) connected to the outside; the sphere (13) is accommodated inside the first space (1110); the movement of the valve stem (120) is guided by the wall (1112) of the first space, and the valve stem (120) is provided with a first curved surface (121) adapted to the sphere (13); the first curved surface (121) is used to contact the sphere (13), so that the sphere (13) is supported by the valve stem (120) toward the inlet (1111).

2. The pressure limiting valve (10) according to claim 1, characterized in that The valve stem (120) comprises: The rod (122) is guided by the wall (1112) of the first space in its moving direction; a spherical support (123), one end of which is connected to the rod (122) and the other end of which is provided with the first curved surface (121); The rod body (122) and the spherical support (123) are formed in separate bodies.

3. The pressure limiting valve (10) according to claim 1, characterized in that The sphere (13) has a nitriding layer or is made of silicon nitride material; and / or the first curved surface (121) of the valve stem (120) has a nitriding layer.

4. The pressure limiting valve (10) according to claim 2, characterized in that A first gap (14) is formed between the spherical support (123) and the wall surface (1112) of the first space.

5. The pressure limiting valve (10) according to claim 1, characterized in that The first valve body (110) has a first hole (1114) to provide the first space (1110), the bottom end surface of the first hole (1114) has the inlet (1111), and the bottom of the first hole (1114) has an expansion section (1113), the aperture of the expansion section (1113) is larger than the aperture of the hole section of the first hole (1114) connected to the expansion section (1113); the first valve body (110) also has a second hole (1115) extending from the inlet (1111) and connected to the outside.

6. The pressure limiting valve (10) according to claim 1, characterized in that Also includes: a second valve body (150), connected to the first valve body (110) and provided with a second space (151); an elastic member (16), accommodated in the second space (151), and configured to provide elastic force; a gasket (17), one side of which is connected to the second valve body (150) and the other side of which is connected to the elastic member (16); An elastic member support (180) is connected to the elastic member (16) and transmits the force provided by the elastic member (16) to the valve stem (120).

7. The pressure limiting valve (10) according to claim 6, characterized in that Also includes: A slider (190), one end of which is connected to the elastic member support (180), and the other end of which is provided with a second curved surface (191); and The valve stem (120) is provided with a third curved surface (124) adapted to the second curved surface (191), and the third curved surface (124) is used to contact the second curved surface (191).

8. The pressure limiting valve (10) according to claim 6, characterized in that The wall surface of the valve stem (120) has a first surface (125) and a second surface (126); the first surface (125) is in close contact with the wall surface (1112) of the first space, and a second gap is formed between the second surface (126) and the wall surface (1112) of the first space; the elastic member support (180) has a fluid channel (181); the second valve body (150) has an outlet (152) connected to the outside; In a first state, the sphere (13) is separated from the inlet (1111), and external fluid flows into the pressure-limiting valve (10) from the inlet (1111), passes through the second gap, passes through the fluid channel (181), and flows out of the pressure-limiting valve (10) from the outlet (152); In the second state, the ball (13) contacts the inlet (1111) so that the inlet (1111) is closed.

9. A high-pressure common rail system (1), characterized in that: The invention comprises a pressure limiting valve (10) according to any one of claims 1 to 8.

10. A method for processing a pressure limiting valve, wherein the pressure limiting valve is the pressure limiting valve (10) according to any one of claims 1 to 8, characterized in that: The processing method comprises: The first curved surface (121) of the valve stem (120) is treated by a nitriding process.

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