Pressure limiting valve and pressure limiting method

Abstract

The present application provides a pressure-limiting valve and a pressure-limiting method. The pressure-limiting valve includes: a valve body having a mating portion; a valve core, the valve core being arranged inside the valve body and matingly connected to the mating portion of the valve body; the valve core including multiple stages of valve cores, including at least a first-stage valve core and a second-stage valve core; the mating portion and the first-stage valve core and the second-stage valve core are mated through clearance fit to form a matching pair; the mating portion is provided with a first-stage overflow hole, a first-stage overflow volume cavity, a first connecting channel, a second-stage overflow volume cavity, a second connecting channel, a third-stage overflow volume cavity, and a third connecting channel in sequence from upstream to downstream; the first connecting channel connects the first-stage overflow volume cavity with the second-stage overflow volume cavity, and the second connecting channel connects the second-stage overflow volume cavity with the third-stage overflow volume cavity.

Description

Technical Field

[0001] The present application relates to the field of fuel injection technology, 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 plays the role of the diesel engine's power heart. 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 also 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] The pressure-limiting valve is an essential pressure protection device in the common rail system. If the system pressure exceeds the limit due to a fault in the rail pressure sensor or ECU control, the pressure-limiting valve automatically opens to prevent damage to pressure-bearing components caused by excessive internal pressure, thus protecting the common rail system. Furthermore, after opening, the pressure-limiting valve must maintain a suitable and stable overflow pressure to ensure that the diesel engine enters limp-home mode and maintains a certain power output without losing power, thereby ensuring safe navigation.

[0005] As common rail systems adapt to different diesel engine models, the pressure and flow ranges of common rail systems are becoming increasingly wider. Currently, existing pressure-limiting valve structures cannot accommodate the wider pressure relief flow range required to meet the common rail system's appropriate overflow pressure range. When the common rail system overflow flow is low, the pressure-limiting valve maintains a low pressure after opening. This results in low common rail pressure after the diesel engine enters limp mode, poor power and emission performance, and even when the overflow pressure is too low, the pressure-limiting valve lacks the ability to stabilize the pressure after overflow. When the common rail system overflow flow is high, due to the limited pressure relief capacity of the pressure-limiting valve, the pressure-limiting valve maintains a high limp mode pressure after opening, which may even exceed the pressure-limiting protection range, rendering the pressure-limiting valve ineffective in providing pressure protection. Common rail systems of varying power typically utilize different pressure-limiting valve models, resulting in limited product adaptability, a wide variety of models, and increased production and operating costs.

[0006] Therefore, there is a need in the art for a pressure limiting valve and a pressure limiting method to solve at least one of the above problems. Summary of the Invention

[0007] One 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 fitting portion; a valve core, the valve core being arranged inside the valve body and being matched and connected with the fitting portion of the valve body, the valve core comprising a plurality of stages of valve cores, at least comprising 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 being 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 first communicating channel, the third-stage overflow volume cavity, and the third communicating channel; volume chamber and the second-stage overflow volume chamber, the second communicating channel communicates the second-stage overflow volume chamber and the third-stage overflow volume chamber, and the third communicating channel communicates 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 cavity, the first communicating channel, the second-stage overflow volume cavity, the second communicating channel, the third-stage overflow volume cavity, and the third communicating channel of the corresponding mating 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 communicating channel, and the second section has a first-stage overflow groove that is radially recessed inward, and there is a gap between the first-stage overflow groove and the inner wall of the first communicating channel.

[0014] In one or more specific embodiments of the pressure-limiting valve, the first-stage valve core and the first-stage overflow hole cooperate with each other through conical surfaces to seal the first-stage overflow hole.

[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 communicating channel, and the fourth section is used to form a third sealing length with the third communicating channel; the fifth section has a second-stage overflow groove that is radially recessed inward, and has a gap between it and the inner wall of the second communicating channel; the sixth section has a third-stage overflow groove that is radially recessed inward, and has a gap between it and the inner wall of the third communicating 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 to the adjusting member at the other end.

[0018] According to the 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 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 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 that overflow is achieved through flow gradient, and the corresponding pressure limiting valve is opened in three stages to relieve the pressure overflow state, so as to ensure that the change gradient of the overflow pressure under different overflow flow rates is small, 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 adapt to common rail system diesel engines of 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 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 pressure limiting valve according to one or more embodiments.

[0022] Figure 2 Schematic diagram of the structure of the first-stage valve core of the pressure limiting valve in one or more embodiments.

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

[0024] Figure 4 Schematic diagram of the structure of the closed state of the pressure limiting valve of one or more embodiments.

[0025] Figure 5 This 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 in one or more embodiments. DETAILED DESCRIPTION

[0028] Reference will now be made in detail to the various embodiments of the present application, examples of which are shown in the accompanying drawings and 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.

[0029] In the subsequent description, the orientations or positional relationships indicated by "left", "right", "center", "axial", "radial", "inside", "outside" or other directional terms are based on the orientations or positional relationships shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or component referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, they should not be understood as limiting this application.

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

[0031] The pressure-limiting valve is an essential pressure protection device in the common rail system. If the system pressure exceeds the limit due to a fault in the rail pressure sensor or ECU control, the pressure-limiting valve automatically opens to prevent damage to pressure-bearing components caused by excessive internal pressure, thus protecting the common rail system. Furthermore, after opening, the pressure-limiting valve must maintain a suitable and stable overflow pressure to ensure that the diesel engine enters limp-home mode and maintains a certain power output without losing power, thereby ensuring safe navigation.

[0032] After in-depth research, the inventors of this application discovered that the currently existing pressure-limiting valve structure cannot take into account a wider range of 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 low pressure after opening. After the diesel engine enters limp mode, the common rail pressure is low, 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 limited pressure relief and 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. Generally, 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, after in-depth research, the inventors set a multi-level valve core structure by setting a valve core, and the corresponding valve body is provided with a corresponding overflow hole, overflow volume cavity and connecting channel structure, thereby realizing overflow through flow gradient, and the corresponding pressure limiting valve is opened in three stages to relieve the pressure overflow state, ensuring that the change gradient of the overflow pressure under different overflow flow rates is small, 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 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 disposed inside the valve body 10 and is connected to 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 has a matching part that is fitted with the first-stage valve core 3 and the second-stage valve core 4 through clearance to form a matching pair. The meaning of the matching part is the part of the valve body 10 that is used to cooperate with the valve core 20 to achieve the pressure limiting function. The structure of the matching part can be that the matching part is 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 that are connected from upstream to downstream; the first connecting channel 11 connects the first-stage overflow volume cavity 102 and the second-stage overflow volume cavity 103, the second connecting channel 12 connects the second-stage overflow volume cavity 103 and the third-stage overflow volume cavity 104, and the third connecting channel 13 connects the third-stage overflow volume cavity 104 and 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 portion of the valve body 10. It is understood that the multiple-stage valve core can be a three-stage valve core, that is, it can also include a third-stage valve core, a fourth-stage valve core, and so on, without limitation. This allows the pressure-limiting valve to overflow in a gradient manner. By using three different overflow states, the gradient of the overflow pressure at different overflow flow rates is minimized. This ensures that the common rail system maintains an appropriate common rail pressure at different overflow flow rates when the diesel engine enters limp mode after the pressure-limiting valve is opened. Furthermore, based on the above two-stage structure, more valve cores and overflow states can be used to ensure overflow capacity at a wider range of 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 communicating channel 11 form a first sealing length L1, the second-stage valve core 4 and the second communicating channel 12 form a second sealing length L2, and the second-stage valve core 4 and the third communicating 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 providing the opening pressure, the valve core 20 may be subjected to 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, and a spring 6 is connected to the spring seat 5 at one end and to an adjustment member 7 at the other end. The specific structure of the adjustment member 7 can be a gasket. The thickness of the gasket can be adjusted to adjust the opening pressure required for different opening pressures.

[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 seal. 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. A spring 6 presses against the upper end of the second-stage valve core 4 via a spring seat 5, transmitting its force to the sealing surface formed by the first-stage valve core 3 and the first valve body 1, sealing the high-pressure fuel in the common rail system. When the system's high-pressure fuel pressure is excessive and the hydraulic force acting on the sealing surface of the first-stage valve core 3 exceeds the spring force, the valve core moves upward against the spring force, opening the sealing surface and allowing fuel to flow out through the valve core's overflow groove and the overflow orifice of the first valve body, thereby relieving fuel pressure. By matching parameters such as the overflow groove, orifice, and spring stiffness, different valve core opening lifts are matched to different overflow flow rates, thereby achieving flow gradient relief. This corresponds to the three-stage opening and pressure relief state of the pressure-limiting valve, ensuring a minimal gradient of relief pressure at different overflow flow rates. This ensures that the common rail system maintains an appropriate common rail pressure at different overflow flow rates when the pressure-limiting valve is opened and the diesel engine enters limp mode.

[0040] In some embodiments, as Figure 1 As shown, 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 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 matching part are distributed in line. In-line distribution means that there is no bend to change the direction and the structure is distributed along the same direction, for example Figure 1 The vertical direction 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 can be detachably fixedly connected. The first valve body 1 provides a mating portion. The hollow portion of the second valve body 8 and the first valve body 1 define a chamber 80. The mating portion is connected to the chamber 80 through a third-stage throttling hole 105 opened in the first valve body 1 between the third-stage overflow volume cavity 104 and the chamber 80. Figure 1 As shown, the first valve body 1 and the second valve body 8 are positioned relative to each other as "bottom" and "top." Hereinafter, the first valve body 1 will be referred to as the "lower valve body" and the second valve body 8 as the "upper valve body." However, it should be understood that this is merely for ease of description; in practice, they could also be positioned front-to-back, left-to-right, or other relative positions. The two can be removably connected by set screws 2. The second valve body 8 can be positioned via guide holes and fastened to the first valve body 1 via screws to form an integral pressure-limiting valve. The upper end of the second valve body 8 is provided with a low-pressure overflow collection port, which houses a low-pressure overflow pipeline for collecting 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 engagement section for positioning and fastening with the first valve body 1. For example, four set screws can be used to connect and fasten the first valve body 1 and the second valve body 8, securing the pressure-limiting valve as a single unit for easy assembly, disassembly, and transportation. However, this is not limiting, and other removable fixed connection structures may also be employed. 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 mounted on the common rail pipe 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 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 mating structure between the first-stage valve core 3 and the mating portion can be such that the radial outer wall of the first-stage valve core 3 includes a first section 31 and a second section 32 along its length. 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 radially inwardly recessed, with a gap between it and the inner wall of the first communication channel 11. Furthermore, the first-stage valve core 3 and the first-stage overflow hole 101 can be sealed by a conical surface, further optimizing 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 concave inward and has a gap between it and the inner wall of the second connecting channel 12; the sixth section 44 has a third-stage overflow groove 403 that is radially concave inward and has a gap between it and the inner wall of the third connecting channel 13.

[0045] Specifically, in some embodiments, the bottom of the first valve body 1 can be provided with a high-pressure sealing ring to achieve sealing with the common rail system common rail pipe. An overflow hole and a two-stage valve core mating section are provided on the inside. The lower end with a smaller inner diameter mating section mates with the first-stage valve core 3, while the upper end with a larger inner diameter mating section mates with the second-stage valve core 4. Two overflow holes are provided on either side of the upper end of the first valve body 1 to further stabilize the overflow pressure. The first-stage valve core 3 can be a cone valve structure, which is tightly pressed against the conical surface of the first valve body 1 by spring force to achieve a seal. 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 fuel. The outer cylinder and the first valve body form a mating part. The second-stage valve core 4 can be a cylindrical structure. The lower end face of the second-stage valve core 4 cooperates with the upper end face of the first valve core 3 to realize the series connection of the two valve cores. Two overflow grooves are set on the second-stage valve core 4, and an overflow hole is set in the middle of the two overflow grooves. The overflow hole is connected to the bottom of the second-stage valve core 4, and the outer cylinder and the first valve body 1 realize the matching of parts.

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

[0047] Combine Figure 4 Schematic diagram of the valve core of the present invention in the closed state. When the pressure-limiting valve is closed, the upper end of the second-stage valve core 4 is subjected to the downward spring force F, and the lower end of the first-stage valve core 3 is subjected to the upward common rail system hydraulic pressure F. When the common rail system pressure is at normal operating pressure, the hydraulic pressure F is less than the spring force F, 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 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 is matched with 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 opened in three levels of 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] Combine Figure 5 , the first-level 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 oil leaks from the gap. 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 flow capacity of the first-stage overflow groove 301 and the second-stage overflow hole 402 reasonably, a reasonable overflow pressure of the common rail system can be maintained.

[0053] Combine Figure 6The present invention enters the secondary open pressure relief overflow state. 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. By matching the parameters, 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, and the first-stage overflow groove 301 and the second-stage overflow groove 401 are both open. After entering the first-stage overflow volume chamber 102, the fuel 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 through the third-stage throttle hole 105 to the low-pressure return oil pipeline. 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] Combine Figure 7 The present invention is in a three-stage open pressure relief overflow state. When the pressure limiting valve is opened, if the overflow flow of the matching common rail system is greater than Q2, the corresponding valve core displacement will be further increased to greater than L3 through parameter matching. 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 L3, and the first-stage overflow groove 301, the second-stage overflow groove 401, and the third-stage overflow groove 403 are all open. After entering the first-stage overflow volume chamber 102, the fuel 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 entering the third-stage overflow volume chamber 104, the fuel flows through the third-stage throttle hole 105 and the third-stage overflow groove 403 to the low-pressure return oil pipeline. Compared with the second-stage open pressure relief overflow state, the third-stage pressure relief adds a 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 embodiment include but are not limited to, by setting a multi-level valve core structure through the valve core, 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 levels to relieve the pressure overflow state, so as to ensure that the change gradient of the overflow pressure under different overflow flow rates is small, so that when the engine (such as a diesel engine) enters limp home 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 discloses the preferred embodiments as described above, they are 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 (100), characterized in that: include: A valve body (10) having a mating portion; A valve core (20), the valve core (20) is arranged inside the valve body (10) and is connected to the matching portion of the valve body (10), the valve core (20) includes multiple stages of valve cores, including at least a first-stage valve core (3) and a second-stage valve core (4), the lower end surface of the second-stage valve core (4) is matched with the upper end surface of the first-stage valve core (3) to form a series structure, and the matching portion and the first-stage valve core (3) and the second-stage valve core (4) are 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 cavity (102), a first communicating channel (11), a second-stage overflow volume cavity (103), a second communicating channel (12), a third-stage overflow volume cavity (104), and a third communicating channel (13) in sequence from upstream to downstream; the first communicating channel (11) communicates the first-stage overflow volume cavity (102) with the second-stage overflow volume cavity (103), the second communicating channel (12) communicates the second-stage overflow volume cavity (103) with the third-stage overflow volume cavity (104), and the third communicating channel (13) communicates the third-stage overflow volume cavity (104) with the overflow volume cavity 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 communicating channel (11) form a first sealing length (L1), the second-stage valve core (4) and the second communicating channel (12) form a second sealing length (L2), and the second-stage valve core (4) and the third communicating 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; The valve body (10) comprises a first valve body (1) and a second valve body (8); the radial outer wall of the first-stage valve core (3) comprises a first-stage overflow groove (301) that is concave radially inward, and the radial outer wall of the second-stage valve core (4) comprises a second-stage overflow groove (401) that is concave radially inward and a third-stage overflow groove (403) that is concave radially inward; When the displacement of the valve core (20) is greater than the first sealing length (L1) and less than the second sealing length (L2), the overflowing fuel can enter the first-stage overflow volume chamber (102) through the first-stage overflow hole (101), the first-stage overflow groove (301) is opened to communicate with the second-stage overflow volume chamber (103), and the second-stage overflow groove (401) and the third-stage overflow groove (403) are not opened. 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 oil return pipeline through the third-stage throttle hole (105) on the first valve body (1), corresponding to the first-stage open pressure relief overflow state; When the displacement of the valve core (20) is greater than the second sealing length (L2) and less than the third sealing length (L3), the overflowing fuel enters the first-stage overflow volume chamber (102) through the first-stage overflow hole (101), the first-stage overflow groove (301) and the second-stage overflow groove (401) are both opened, and after entering the first-stage overflow volume chamber (102), the fuel 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 through the third-stage throttle hole (105) to the low-pressure oil return pipeline, corresponding to the second-stage open pressure relief overflow state; When the displacement of the valve core (20) is greater than the third sealing length (L3), the overflowing fuel enters the first-stage overflow volume chamber (102) through the first-stage overflow hole (101). After entering the first-stage overflow volume chamber (102), the fuel 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 entering the third-stage overflow volume chamber (104), the fuel flows through the third-stage throttle hole (105) and the third-stage overflow groove (403) to the low-pressure oil return pipeline.

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 cavity (102), the first communicating channel (11), the second-stage overflow volume cavity (103), the second communicating channel (12), the third-stage overflow volume cavity (104), and the third communicating channel (13) of the matching portion are distributed in series.

3. The pressure limiting valve (100) according to claim 1, characterized in that The second valve body (8) and the first valve body (1) are separate parts and can be fixedly connected in a detachable manner; 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) between the third-stage overflow volume cavity (104).

4. 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 communicating channel (11), and the second section (32) has a first-stage overflow groove (301) that is radially recessed inward and has a gap between it and the inner wall of the first communicating channel (11).

5. 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) cooperate with each other through conical surfaces to seal the first-stage overflow hole (101).

6. 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 communicating channel (12), and the fourth section (42) is used to form a third sealing length (L3) with the third communicating 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 communicating 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 communicating channel (13).

7. 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.

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

9. A pressure limiting method for a common rail system, wherein an engine has the common rail system, characterized in that: A pressure limiting valve (100) as described in any one of claims 1 to 8 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 (20) 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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