Pressure limiting valve and pressure limiting method

Abstract

The invention provides a pressure limiting valve and a pressure limiting method. The pressure limiting valve comprises a valve body provided with a matching part; the valve element is arranged in the valve body and is connected with the matching part of the valve body in a matched mode, the valve element comprises a plurality of stages of valve element bodies and at least comprises a first-stage valve element body and a second-stage valve element body, and the matching part is in clearance fit with the first-stage valve element body and the second-stage valve element body to form a matched matching part; the matching part is sequentially provided with a first-stage overflow hole, a first-stage overflow volume cavity, a first communicating hole channel, a second-stage overflow volume cavity, a second communicating hole channel, a third-stage overflow volume cavity and a third communicating hole channel which are communicated with one another from upstream to downstream; the first communication hole channel is communicated with the first-stage overflow volume cavity and the second-stage overflow volume cavity, and the second communication hole channel is communicated with the second-stage overflow volume cavity and the third-stage overflow volume cavity.

Description

Technical Field

[0001] The present application relates to the technical field of fuel injection, and in particular to a pressure limiting valve and a pressure limiting method. Background Art

[0002] The high-pressure common rail system is the core component of the diesel engine and serves as the power heart of the diesel engine. It has largely gotten rid of the problem that the injection characteristics of the traditional mechanical fuel system are affected by large fluctuations in engine speed and injection pressure, increased the diesel engine fuel injection pressure, improved the spray atomization condition, and achieved flexible control of the injection amount and injection timing of the diesel engine fuel injection under all operating conditions. It plays a positive role in optimizing the diesel engine's in-cylinder combustion, reducing emissions and fuel consumption.

[0003] With the increasing application of common rail systems in marine engines, the pressure and flow adaptability range of common rail systems is becoming wider and wider. From small-flow high-speed diesel engines to large-flow medium and low-speed diesel engines, high-pressure common rail systems are increasingly being used.

[0004] As an indispensable pressure protection device for the common rail system, the pressure limiting valve will automatically open when the system pressure exceeds the limit value due to a fault in the rail pressure sensor or ECU control, so as to avoid damage to the pressure-bearing components due to excessive internal pressure in the system, thus protecting the common rail system. At the same time, the pressure limiting valve needs to maintain a suitable and stable overflow pressure after opening, so as to ensure that the diesel engine enters the limp state and maintains a certain power output without causing the ship to lose power, thereby ensuring the safety of the ship's navigation.

[0005] As the common rail system matches different types of diesel engines, the pressure and flow range of the common rail system is becoming wider and wider. The existing structure of the pressure limiting valve cannot take into account the wider pressure relief flow to meet the appropriate overflow pressure range of the common rail system. When the overflow flow of the common rail system is small, the pressure limiting valve maintains a small pressure after opening. After the diesel engine enters limp mode, the common rail pressure is small, and the power and emission performance are poor. Even when the overflow pressure is too small, the pressure limiting valve does not have the ability to stabilize the pressure after overflow; when the overflow flow of the common rail system is large, due to the pressure relief overflow capacity of the pressure limiting valve, the pressure limiting valve will maintain a high pressure limp pressure after opening, and may even exceed the pressure protection pressure range, resulting in the pressure limiting valve failing to play the role of pressure protection. Usually, different power common rail systems use different types of pressure limiting valves, resulting in poor product adaptability and multiple models, which increases production and operation costs.

[0006] Therefore, the art needs a pressure limiting valve and a pressure limiting method to solve at least one of the above problems. Summary of the invention

[0007] An object of the present application is to provide a pressure limiting valve.

[0008] One object of the present application is to provide a voltage limiting method.

[0009] According to the first aspect of the present application, a pressure-limiting valve comprises: a valve body having a matching portion; a valve core, the valve core is arranged inside the valve body and is matched and connected with the matching portion of the valve body, the valve core comprises valve cores of multiple stages, at least including a first-stage valve core and a second-stage valve core, the matching portion and the first-stage valve core and the second-stage valve core are matched through clearance to form a matching pair; the matching portion is provided with a first-stage overflow hole, a first-stage overflow volume cavity, a first communicating channel, a second-stage overflow volume cavity, a second communicating channel, a third-stage overflow volume cavity, and a third communicating channel in sequence from upstream to downstream; the first communicating channel is connected to the first-stage overflow hole, the first-stage overflow volume cavity, the second-stage overflow volume cavity, the second communicating channel, the third-stage overflow volume cavity, and the third communicating channel; the first communicating channel is connected to the first-stage overflow hole, the first-stage overflow volume cavity, the second-stage overflow volume cavity, and the third communicating channel; the first communicating channel is connected to the first-stage overflow hole, the first-stage overflow volume cavity, the second-stage overflow volume cavity, and the third communicating channel. The first-stage overflow hole is connected to the second-stage overflow volume chamber, the second communicating channel is connected to the second-stage overflow volume chamber and the third-stage overflow volume chamber, and the third communicating channel is connected to the third-stage overflow volume chamber and the overflow volume chamber of the next stage; wherein, in the closed state of the pressure-limiting valve, the first-stage valve core closes the first-stage overflow hole, the first-stage valve core and the first communicating channel form a first sealing length, the second-stage valve core and the second communicating channel form a second sealing length, the second-stage valve core and the third communicating channel form a third sealing length, and the first sealing length is less than the second sealing length and less than the third sealing length.

[0010] In one or more specific embodiments of the pressure limiting valve, the first-stage valve core, the second-stage valve core, and the first-stage overflow hole, the first-stage overflow volume chamber, the first connecting channel, the second-stage overflow volume chamber, the second connecting channel, the third-stage overflow volume chamber, and the third connecting channel of the corresponding matching parts are distributed in series.

[0011] In one or more specific embodiments of the pressure limiting valve, the valve body includes a first valve body and a second valve body, the second valve body and the first valve body are separate parts, and the two can be detachably fixedly connected; the first valve body provides the matching part, the hollow part of the second valve body and the first valve body define a chamber, and the matching part is connected through a third-stage throttling hole opened in the first valve body between the third-stage overflow volume chamber and the chamber.

[0012] In one or more specific embodiments of the pressure-limiting valve, the second-stage overflow volume chamber and the third-stage overflow volume chamber can be communicated with each other through a second-stage overflow hole provided in the second-stage valve core.

[0013] In one or more specific embodiments of the pressure limiting valve, the radial outer wall of the first-stage valve core includes a first section and a second section in the length direction, wherein the first section is used to form a first sealing length with the first connecting channel, and the second section has a first-stage overflow groove that is radially recessed inward and has a gap with the inner wall of the first connecting channel.

[0014] In one or more specific embodiments of the pressure-limiting valve, the first-stage valve core and the first-stage overflow hole seal the first-stage overflow hole through conical surface cooperation.

[0015] In one or more specific embodiments of the pressure-limiting valve, the radial outer wall of the second-stage valve core includes a third section, a fourth section, a fifth section, and a sixth section in the length direction, the third section is used to form a second sealing length with the second connecting channel, and the fourth section is used to form a third sealing length with the third connecting channel; the fifth section has a second-stage overflow groove that is radially recessed inwardly, and has a gap with the inner wall of the second connecting channel; the sixth section has a third-stage overflow groove that is radially recessed inwardly, and has a gap with the inner wall of the third connecting channel.

[0016] In one or more specific embodiments of the pressure-limiting valve, the valve core is subjected to elastic force to provide an opening pressure of the pressure-limiting valve.

[0017] In one or more specific embodiments of the pressure-limiting valve, a spring seat is adjacently connected to the valve core, and a spring is connected to the spring seat at one end and connected to an adjusting member at the other end.

[0018] According to a second aspect of the present application, a pressure limiting method for a common rail system is provided, an engine has the common rail system, and adopts the pressure limiting valve as described in the first aspect; the pressure limiting method comprises: the engine comprises at least a first power, a second power, and a third power, and the corresponding overflow pressures are respectively the first overflow pressure, the second overflow pressure, and the third overflow pressure, and the corresponding overflow pressures push the valve core to move a first distance, a second distance, and a third distance, respectively, wherein the first sealing length is less than the first distance and less than the second sealing length, the second sealing length is less than the second distance and less than the third sealing length, and the third sealing length is less than the third distance.

[0019] In the technical solution introduced above, a multi-level valve core structure is set by the valve core, and the corresponding valve body is provided with a corresponding overflow hole, overflow volume cavity and connecting channel structure, so as to realize overflow through flow gradient, and the corresponding pressure limiting valve is opened in three stages to relieve pressure and overflow state, so as to ensure that the change gradient of overflow pressure is small under different overflow flow rates, so that the common rail pressure suitable for the common rail system can be guaranteed under different overflow flow rates when the engine (such as a diesel engine) enters limp state after the pressure limiting valve is opened, and a wider range of overflow flow requirements can be met, while taking into account the adaptation of common rail system diesel engines with multiple power ranges, thereby reducing the types of pressure limiting valve specifications. 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 drawings, the same reference numerals always represent the same features. It should be noted that these drawings are only examples and are not drawn in proportion. They should not be used to limit the actual scope of protection claimed by the present application. Among them:

[0021] Figure 1 Schematic diagram of the structure of a pressure limiting valve according to one or more embodiments.

[0022] Figure 2 A schematic structural diagram of a first-stage valve core of a pressure-limiting valve according to one or more embodiments.

[0023] Figure 3 Schematic diagram of the structure of a second-stage valve core of a pressure limiting valve according to one or more embodiments.

[0024] Figure 4 It is a structural schematic diagram of the closed state of the pressure limiting valve of one or more embodiments.

[0025] Figure 5 It is a structural schematic diagram of the first-stage opening pressure relief overflow state of the pressure limiting valve in one or more embodiments.

[0026] Figure 6 It is a structural schematic diagram of the secondary opening pressure relief overflow state of the pressure limiting valve in one or more embodiments.

[0027] Figure 7 It is a structural schematic diagram of the three-stage opening pressure relief overflow state of the pressure limiting valve of one or more embodiments. DETAILED DESCRIPTION

[0028] Reference will now be made in detail to the various embodiments of the application, the examples of which are shown in the accompanying drawings and are described below. Although the application will be described in conjunction with the exemplary embodiments, it should be appreciated that this specification is not intended to limit the application to those exemplary embodiments. On the contrary, the application is intended to not only cover these exemplary embodiments, but also to cover various alternative forms, modified forms, equivalent forms and other embodiments that may be included in the spirit and scope of the application defined by the appended claims.

[0029] In the subsequent description, the orientation or position relationship indicated by "left", "right", "middle", "axial", "radial", "inside", "outside" or other orientation terms is based on the orientation or position relationship shown in the drawings, which 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 operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0030] At the same time, the present application uses specific words to describe the embodiments of the present application. For example, "some embodiments" means a certain feature, structure or characteristic related to at least one embodiment of the present application. Therefore, it should be emphasized and noted that "some embodiments" mentioned twice or multiple times in different locations in this specification do not necessarily refer to the same embodiment. In addition, some features, structures or characteristics of some embodiments of the present application can be appropriately combined.

[0031] As an indispensable pressure protection device for the common rail system, the pressure limiting valve will automatically open when the system pressure exceeds the limit value due to a fault in the rail pressure sensor or ECU control, so as to avoid damage to the pressure-bearing components due to excessive internal pressure in the system, thus protecting the common rail system. At the same time, the pressure limiting valve needs to maintain a suitable and stable overflow pressure after opening, so as to ensure that the diesel engine enters the limp state and maintains a certain power output without causing the ship to lose power, thereby ensuring the safety of the ship's navigation.

[0032] After in-depth research, the inventors of this application have found that the current existing structure of the pressure limiting valve cannot take into account a wider pressure relief flow to meet the appropriate overflow pressure range of the common rail system. When the overflow flow of the common rail system is small, the pressure is maintained at a low level after the pressure limiting valve is opened. After the diesel engine enters limp mode, the common rail pressure is small, and the power and emission performance are poor. Even when the overflow pressure is too small, the pressure limiting valve does not have the ability to stabilize the pressure after overflow; when the overflow flow of the common rail system is large, due to the pressure relief overflow capacity of the pressure limiting valve, the pressure limiting valve will maintain a high limp pressure after opening, and may even exceed the pressure limiting protection pressure range, resulting in the pressure limiting valve failing to play a role in pressure protection. Usually, different power common rail systems use different types of pressure limiting valves, resulting in poor product adaptability, multiple models, and increased production and operating costs.

[0033] Based on the above, the inventor, after in-depth research, has achieved overflow through flow gradient by setting a multi-level valve core structure through the valve core, and the corresponding valve body is provided with corresponding overflow holes, overflow volume chambers and connecting channel structures, so as to ensure that the overflow is carried out through flow gradient, and the corresponding pressure limiting valve is opened in three stages to relieve the pressure and overflow state, so as to ensure that the change gradient of the overflow pressure is small under different overflow flow rates, so that after the pressure limiting valve is opened and the engine (such as a diesel engine) enters limp home, the common rail pressure suitable for the common rail system can be guaranteed under different overflow flow rates, which can meet the overflow flow requirements in a wider range, and take into account the adaptation of common rail system diesel engines with multiple power ranges, thereby reducing the types of pressure limiting valve specifications.

[0034] Although the pressure limiting method of the pressure limiting valve disclosed in the embodiment of the present application is applicable to marine diesel engines to achieve the effect of adapting the same pressure limiting valve to diesel engines with a wider range of power, it is not limited to this. For example, it can be applicable to other application scenarios, such as heavy vehicles, railway trains, and can also be applicable to other internal combustion engines, such as diesel-alternative fuel dual-fuel engines, such as methanol-diesel dual-fuel engines, ammonia-diesel dual-fuel engines, etc., as long as the engine can apply the pressure limiting valve disclosed in the embodiment of the present application.

[0035] refer to Figures 1 to 7 As shown, in some embodiments, the pressure limiting valve 100 includes a valve body 10 and a valve core 20. The valve body 10 has a matching portion. The valve core 20 is arranged inside the valve body 10 and is matched and connected with the matching portion of the valve body 10. The valve core 20 includes multiple stages of valve cores, including at least, for example Figure 2 The first stage valve core 3 shown, for example Figure 3 The second-stage valve core 4 shown, the matching part and the first-stage valve core 3, the second-stage valve core 4 are matched through clearance to form a matching pair. The meaning of the matching part is the part of the valve body 10 used to cooperate with the valve core 20 to realize the pressure limiting function. The structure of the matching part can be that the matching part is sequentially provided with a first-stage overflow hole 101, a first-stage overflow volume cavity 102, a first connecting channel 11, a second-stage overflow volume cavity 103, a second connecting channel 12, a third-stage overflow volume cavity 104, and a third connecting channel 13 from upstream to downstream; the first connecting channel 11 connects the first-stage overflow volume cavity 102 with the second-stage overflow volume cavity 103, the second connecting channel 12 connects the second-stage overflow volume cavity 103 with the third-stage overflow volume cavity 104, and the third connecting channel 13 connects the third-stage overflow volume cavity 104 with the overflow volume cavity of the next stage.

[0036] The multiple-stage valve core here is Figures 1 to 7 As shown in the two-stage valve core, the overflow volume chamber of the next stage is the hollow part of the valve body 10. It can be understood that the valve core of multiple stages can be a valve core of the stage, that is, it can also include a third-stage valve core, a fourth-stage valve core, etc., which are not limited to this. That is, the overflow flow of the pressure limiting valve is divided into gradients for overflow. Through three different overflow states, the change gradient of the overflow pressure under different overflow flow rates is guaranteed to be small, so that the common rail pressure suitable for the common rail system can be guaranteed under different overflow flow rates when the diesel engine enters limp mode after the pressure limiting valve is opened. At the same time, according to the above two-stage structure, more stages of valve cores and overflow states can also be used to ensure the overflow capacity under more overflow flow rates.

[0037] refer to Figure 4As shown, in the closed state of the pressure-limiting valve 100, the first-stage valve core 3 closes the first-stage overflow hole 101, the first-stage valve core 3 and the first connecting channel 11 form a first sealing length L1, the second-stage valve core 4 and the second connecting channel 12 form a second sealing length L2, the second-stage valve core 4 and the third connecting channel 13 form a third sealing length L3, and the first sealing length is less than the second sealing length and less than the third sealing length.

[0038] Continue to refer Figure 1 As shown, for the structure of providing the opening pressure, the valve core 20 may be subjected to the elastic force to provide the opening pressure of the pressure limiting valve. The specific structure may be, in some embodiments, such as Figure 1 As shown, the valve core 20 is adjacently connected to a spring seat 5, a spring 6 is connected to the spring seat 5 at one end, and is connected to an adjustment member 7 at the other end. The specific structure of the adjustment member 7 can be a gasket, and the thickness of the gasket can be adjusted to adjust the opening pressure provided for different opening pressure requirements.

[0039] The conical surface of the first-stage valve core 3 cooperates with the conical surface of the first valve body 1 to form a high-pressure conical surface seal, and the lower end surface of the second-stage valve core 4 cooperates with the upper end surface of the first-stage valve core 3 to form a series structure. The spring 6 is pressed on the upper end of the second-stage valve core 4 through the spring seat 5, and the spring force is transmitted to the sealing surface formed by the first-stage valve core 3 and the first valve body 1 to seal the high-pressure fuel in the common rail system. When the high-pressure fuel pressure of the system is too high, and the hydraulic force acting on the sealing surface of the first-stage valve core 3 is greater than the spring force, the valve core overcomes the spring force and moves upward, the sealing surface opens, and the fuel flows out through the overflow groove of the valve core and the overflow hole of the first valve body to achieve fuel pressure relief. Through the matching of parameters such as the overflow groove, the throttling hole and the spring stiffness, different valve core opening lifts are matched under different overflow flow rates, thereby achieving flow gradient overflow, and the corresponding pressure limiting valve is opened in three stages to relieve pressure and overflow states, ensuring that the change gradient of the overflow pressure under different overflow flow rates is small, so that the common rail pressure suitable for the common rail system can be guaranteed under different overflow flow rates when the diesel engine enters limp mode after the pressure limiting valve is opened.

[0040] In some embodiments, Figure 1 As shown, the first-stage valve core 3, the second-stage valve core 4, and the first-stage overflow hole 101, the first-stage overflow volume cavity 102, the first communication channel 11, the second-stage overflow volume cavity 103, the second communication channel 12, the third-stage overflow volume cavity 104, and the third communication channel 13 of the corresponding matching part are distributed in line. In-line distribution means a structure that is distributed in the same direction without bending to change direction, for example Figure 1 The up and down directions shown in FIG. The in-line distribution structure makes it easier to achieve the overflow flow of the pressure limiting valve in a gradient manner.

[0041] Continue to refer Figure 1As shown, in some embodiments, the valve body 10 includes a first valve body 1 and a second valve body 8, the second valve body 8 and the first valve body 1 are separate parts, and the two can be detachably fixedly connected; the first valve body 1 provides a matching portion, the hollow portion of the second valve body 8 and the first valve body 1 define a chamber 80, and the matching portion is connected to the chamber 80 through the third-stage overflow volume cavity 104 and the third-stage throttling hole 105 opened in the first valve body 1. Figure 1 As shown, the relative position relationship between the first valve body 1 and the second valve body 8 is lower and upper, that is, the first valve body 1 is also referred to as the lower valve body and the second valve body 8 is referred to as the upper valve body, but it can be understood that this is only for the convenience of description. In practice, the relative position relationship can also be front, back, left, right, etc. The two can be detachably fixedly connected by a set screw 2, that is, the second valve body 8 can be positioned through a guide hole and fastened with the first valve body 1 by a screw to form a pressure limiting valve as a whole. The upper end of the second valve body 8 is provided with a low-pressure overflow collection interface, and a low-pressure overflow pipeline is installed to collect the fuel overflowing after the pressure limiting valve is opened. The lower end of the second valve body 8 is provided with a threaded hole and a guide matching section to position and fasten with the first valve body 1. For example, four fastening screws can be used to connect and fasten the first valve body 1 and the second valve body 8, so that the pressure limiting valve is connected and fastened into a whole, which is convenient for disassembly and transportation. However, this is not a limitation, and other detachable fixed connection structures can also be used. In addition, the second valve body 8 may be provided with a step on the outer circumference, and the pressure limiting valve 100 may be installed on the common rail pipe by using a pressure plate or other structure.

[0042] Continue to refer Figures 1 to 7 As shown, the structure of the second-stage valve core 4 may further include that the second-stage overflow volume chamber 103 and the third-stage overflow volume chamber 104 can be communicated with each other through a second-stage overflow hole 402 opened in the second-stage valve core 4 .

[0043] refer to Figure 2 ,as well as Figures 4 to 7 As shown, the matching structure of the first-stage valve core 3 and the matching part can be that the radial outer wall of the first-stage valve core 3 includes a first section 31 and a second section 32 in the length direction, wherein the first section 31 is used to form a first sealing length L1 with the first communication channel 11, and the second section 32 has a first-stage overflow groove 301 that is recessed radially inward, and there is a gap between the first-stage overflow hole 101 and the inner wall of the first communication channel 11. In addition, the first-stage valve core 3 and the first-stage overflow hole 101 can seal the first-stage overflow hole 101 through the conical surface matching, so as to further optimize the reliability of providing the opening pressure.

[0044] refer to Figure 3 ,as well as Figures 4 to 7As shown, the matching structure of the second-stage valve core 4 and the matching part can be that the radial outer wall of the second-stage valve core 4 includes a third section 41, a fourth section 42, a fifth section 43, and a sixth section 44 in the length direction, the third section is used to form a second sealing length L2 with the second connecting channel 12, and the fourth section 42 is used to form a third sealing length L3 with the third connecting channel 13; the fifth section 43 has a second-stage overflow groove 401 that is radially recessed inward, and has a gap between the second connecting channel 12 and the inner wall; the sixth section 44 has a third-stage overflow groove 403 that is radially recessed inward, and has a gap between the third connecting channel 13 and the inner wall.

[0045] Specifically, in some embodiments, a high-pressure sealing ring may be provided at the bottom of the first valve body 1 to achieve sealing with the common rail pipe of the common rail system, an overflow hole and a two-stage valve core matching section are provided on the inside, the matching section with a small inner diameter at the lower end matches with the first-stage valve core 3, and the matching section with a large inner diameter at the upper end matches with the second-stage valve core 4, and two overflow holes are provided on both sides of the upper end of the first valve body 1 to further stabilize the overflow pressure. The first-stage valve core 3 may be a cone valve structure, which is sealed by being pressed by spring force with the cone surface of the first valve body 1, and overflow grooves are provided on both sides of the first valve core 3. When the first-stage valve core 3 of the pressure limiting valve is opened, it is used to overflow the fuel, and the outer cylinder and the first valve body are matched with each other. The second-stage valve core 4 can be a cylindrical structure. The lower end surface of the second-stage valve core 4 cooperates with the upper end surface of the first valve core 3 to realize the series connection of the two valve cores. Two overflow grooves are arranged on the second-stage valve core 4. An overflow hole is arranged in the middle of the two overflow grooves. The overflow hole is connected to the bottom of the second-stage valve core 4. The outer cylinder and the first valve body 1 realize the matching of the parts.

[0046] And combined Figures 4 to 7 The content of the present invention further introduces in detail the principle of using the pressure limiting valve 100 introduced in the above embodiment to realize overflow with gradient overflow, so that the change gradient of the overflow pressure under different overflow flow rates is small, and the pressure limiting valve is opened and the diesel engine enters limp home state. Under different overflow flow rates, the common rail pressure suitable for the common rail system can be guaranteed.

[0047] Combination Figure 4 , a schematic diagram of the valve core closed state of the present invention. When the pressure limiting valve is in the closed state, the upper end of the second-stage valve core 4 is subjected to the downward F spring force, and the lower end of the first-stage valve core 3 is subjected to the upward F liquid pressure of the common rail system. When the pressure of the common rail system is at the normal operating pressure, the F liquid pressure is less than the F spring force, and the conical surface of the first-stage valve core 3 cooperates with the conical surface of the first valve body 1 to form a high-pressure conical surface seal, and the pressure limiting valve is in the closed state.

[0048] The first-stage overflow groove 301 of the first-stage valve core 1 forms an initial sealing length L1 with the first valve body 1, and the second-stage overflow groove 401 and the third-stage overflow groove 403 of the second-stage valve core 2 form initial sealing lengths L2 and L3 with the first valve body 1 respectively. In order to ensure different valve core opening lifts and realize flow gradient overflow, it is designed that L1<L2<L3.

[0049] When the system high-pressure fuel pressure is too high and the force acting on the sealing surface of the first-stage valve core 3 is greater than the spring force, the valve core overcomes the spring force and moves upward, the sealing surface opens, and the fuel pressure is released.

[0050] When the pressure limiting valve matches different common rail systems, the overflow flow of the pressure limiting valve is different. Different valve core opening lifts are matched under different overflow flow rates, thereby realizing flow gradient overflow. The corresponding valve core is divided into three levels of opening pressure relief overflow state to ensure that the change gradient of the overflow pressure under different overflow flow rates is small: when the flow rate is less than Q1, the corresponding valve core displacement is greater than L1 and less than L2; when the flow rate is greater than Q1 and less than Q2, the corresponding valve core displacement is greater than L2 and less than L3; when the flow rate is greater than Q2, the corresponding valve core displacement is greater than L3, as follows:

[0051] Combination Figure 5 , the first-stage opening pressure relief overflow state of the present invention.

[0052] When the pressure limiting valve is opened, the overflow flow of the matched common rail system is less than Q1. By matching the design parameters, the corresponding valve core displacement is greater than L1 and less than L2. The overflowing fuel first enters the first-stage overflow volume chamber 102 through the first-stage overflow hole 101. The valve core displacement is greater than L1, and the first-stage overflow groove 301 is opened to communicate with the second-stage overflow volume chamber 103. Since the valve core lift is less than L2, the second-stage overflow groove 401 and the third-stage overflow groove 403 are not opened, and only a small amount of gap leaks oil. Most of the fuel can only flow into the third-stage overflow volume chamber 104 through the second-stage overflow hole 402 on the second-stage valve core 4, and then flow to the low-pressure return oil pipeline through the third-stage throttling hole 105 on the first valve body 1. By matching the reasonable flow capacity of the first-stage overflow groove 301 and the second-stage overflow hole 402, a reasonable overflow pressure of the common rail system can be maintained.

[0053] Combination Figure 6, the secondary opening pressure relief overflow state of the present invention. When the pressure limiting valve is opened, if the overflow flow of the matching common rail system is greater than Q1 and less than Q2, due to the increase in overflow flow, the system overflow pressure increases, and the F liquid pressure on the valve core increases, the corresponding valve core displacement will increase. Through parameter matching, the valve core displacement is greater than L2 and less than L3. The overflowing fuel first enters the first-stage overflow volume chamber 102 through the first-stage overflow hole 101. The valve core displacement is greater than L2. The first-stage overflow groove 301 and the second-stage overflow groove 401 are both opened. After the fuel enters the first-stage overflow volume chamber 102, it can flow from the second-stage overflow hole 402 and the second-stage overflow groove 401 into the third-stage overflow volume chamber 104, and then flow to the low-pressure return oil pipeline through the third-stage throttle hole 105. Compared with the first-stage open pressure relief overflow state, the second-stage pressure relief increases the pressure relief channel of the overflow groove 402, and the pressure relief capacity becomes stronger, thereby weakening the trend of increasing overflow pressure due to the increase in overflow flow.

[0054] Combination Figure 7 , the three-stage open pressure relief overflow state of the present invention. When the pressure limiting valve is opened, if the overflow flow of the matched common rail system is greater than Q2, the corresponding valve core displacement will be further increased to greater than L3 through parameter matching, and the overflowing fuel first enters the first-stage overflow volume chamber 102 through the first-stage overflow hole 101, and the valve core displacement is greater than L3. The first-stage overflow groove 301, the second-stage overflow groove 401 and the third-stage overflow groove 403 are all opened. After the fuel enters the first-stage overflow volume chamber 102, it can flow from the second-stage overflow hole 402 and the second-stage overflow groove 401 into the third-stage overflow volume chamber 104. After the fuel enters the third-stage overflow volume chamber 104, it flows to the low-pressure oil return pipeline through the third-stage throttle hole 105 and the third-stage overflow groove 403. Compared with the second-stage open pressure relief overflow state, the third-stage pressure relief increases the pressure relief channel of the overflow groove 403, and the pressure relief capacity is further enhanced, thereby further weakening the trend of increasing overflow pressure caused by the increase in overflow flow.

[0055] It can be understood that the present application also provides a pressure limiting method, which adopts the pressure limiting valve 100 introduced in the above embodiment; the pressure limiting method includes: the pressure limiting valve 100 corresponds to the engine with the common rail system including at least a first power, a second power, and a third power, and the corresponding overflow pressures are the first overflow pressure, the second overflow pressure, and the third overflow pressure, respectively, and the corresponding overflow pressures push the valve core 10 to move a first distance, a second distance, and a third distance, respectively, wherein the first sealing length L1 is less than the first distance and less than the second sealing length L2, the second sealing length L2 is less than the second distance and less than the third sealing length L3, and the third sealing length L3 is less than the third distance, thereby achieving the effect of meeting a wider range of overflow flow requirements and adapting to common rail system diesel engines of multiple power ranges, thereby reducing the types of pressure limiting valve specifications and reducing costs.

[0056] The beneficial effects of adopting the above embodiments include, but are not limited to, a multi-level valve core structure is set by the valve core, and the corresponding valve body is provided with a corresponding overflow hole, overflow volume cavity and connecting channel structure, so as to realize overflow through flow gradient, and the corresponding pressure limiting valve is opened in three stages to relieve pressure and overflow state, so as to ensure that the change gradient of overflow pressure under different overflow flow rates is small, so that when the engine (such as a diesel engine) enters limp state after the pressure limiting valve is opened, the common rail pressure suitable for the common rail system can be guaranteed under different overflow flow rates, which can meet the overflow flow requirements in a wider range and adapt to common rail system diesel engines of multiple power ranges, thereby reducing the types of pressure limiting valve specifications.

[0057] Although the present application is disclosed as above in terms of preferred implementation modes, it 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 modification, equivalent changes and modifications made to the above implementation modes 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 (100), characterized in that: include: A valve body (10) having a mating portion; A valve core (20), the valve core (20) being arranged inside the valve body (10) and being connected to a matching portion of the valve body (10), the valve core (20) comprising a plurality of stages of valve cores, at least comprising a first-stage valve core (3) and a second-stage valve core (4), the matching portion and the first-stage valve core (3) and the second-stage valve core (4) being matched through clearance to form a matching pair; The matching portion is provided with a first-stage overflow hole (101), a first-stage overflow volume chamber (102), a first communicating channel (11), a second-stage overflow volume chamber (103), a second communicating channel (12), a third-stage overflow volume chamber (104), and a third communicating channel (13) in sequence from upstream to downstream; the first communicating channel (11) communicates the first-stage overflow volume chamber (102) with the second-stage overflow volume chamber (103), the second communicating channel (12) communicates the second-stage overflow volume chamber (103) with the third-stage overflow volume chamber (104), and the third communicating channel (13) communicates the third-stage overflow volume chamber (104) with the overflow volume chamber of the next stage; Wherein, in the closed state of the pressure-limiting valve (100), the first-stage valve core (3) closes the first-stage overflow hole (101), the first-stage valve core (3) and the first connecting channel (11) form a first sealing length (L1), the second-stage valve core (4) and the second connecting channel (12) form a second sealing length (L2), the second-stage valve core (4) and the third connecting channel (13) form a third sealing length (L3), and the first sealing length is less than the second sealing length and less than the third sealing length.

2. The pressure limiting valve (100) according to claim 1, characterized in that: The first-stage valve core (3), the second-stage valve core (4), and the corresponding first-stage overflow hole (101), the first-stage overflow volume chamber (102), the first connecting channel (11), the second-stage overflow volume chamber (103), the second connecting channel (12), the third-stage overflow volume chamber (104), and the third connecting channel (13) of the matching parts are distributed in series.

3. The pressure limiting valve (100) according to claim 1, characterized in that: The valve body (10) comprises a first valve body (1) and a second valve body (8); the second valve body (8) and the first valve body (1) are separate parts and can be detachably fixedly connected; the first valve body (1) provides the matching portion, the hollow portion of the second valve body (8) and the first valve body (1) define a chamber (80), and the matching portion is connected to the chamber (80) through a third-stage throttling hole (105) opened in the first valve body (1) through a third-stage overflow volume cavity (104).

4. The pressure limiting valve (100) according to claim 1, characterized in that: The second-stage overflow volume chamber (103) and the third-stage overflow volume chamber (104) can be communicated with each other via a second-stage overflow hole (402) provided in the second-stage valve core (4).

5. The pressure limiting valve (100) according to claim 1, characterized in that: The radial outer wall of the first-stage valve core (3) includes a first section (31) and a second section (32) in the length direction, wherein the first section (31) is used to form a first sealing length (L1) with the first connecting channel (11), and the second section (32) has a first-stage overflow groove (301) that is radially recessed inward and has a gap with the inner wall of the first connecting channel (11).

6. The pressure limiting valve (100) according to claim 1, characterized in that: The first-stage valve core (3) and the first-stage overflow hole (101) seal the first-stage overflow hole (101) through conical surface cooperation.

7. The pressure limiting valve (100) according to claim 1, characterized in that: The radial outer wall of the second-stage valve core (4) includes a third section (41), a fourth section (42), a fifth section (43), and a sixth section (44) in the length direction, wherein the third section is used to form a second sealing length (L2) with the second connecting channel (12), and the fourth section (42) is used to form a third sealing length (L3) with the third connecting channel (13); the fifth section (43) has a second-stage overflow groove (401) that is recessed radially inwards, and has a gap with the inner wall of the second connecting channel (12); the sixth section (44) has a third-stage overflow groove (403) that is recessed radially inwards, and has a gap with the inner wall of the third connecting channel (13).

8. The pressure limiting valve (100) according to claim 1, characterized in that: The valve core (20) is subjected to elastic force to provide the opening pressure of the pressure-limiting valve.

9. The pressure limiting valve (100) according to claim 8, characterized in that: The valve core (20) is adjacently connected to a spring seat (5); a spring (6) is connected to the spring seat (5) at one end and to an adjusting member (7) at the other end.

10. A pressure limiting method for a common rail system, an engine having the common rail system, characterized in that: A pressure limiting valve (100) as described in any one of claims 1 to 9 is used; the pressure limiting method includes: the engine includes at least a first power, a second power, and a third power, and the corresponding overflow pressures are the first overflow pressure, the second overflow pressure, and the third overflow pressure, respectively, and the corresponding overflow pressures push the valve core (10) to move a first distance, a second distance, and a third distance, respectively, wherein the first sealing length (L1) is less than the first distance and less than the second sealing length (L2), the second sealing length (L2) is less than the second distance and less than the third sealing length (L3), and the third sealing length (L3) is less than the third distance.

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